WO2025229178A1

WO2025229178A1 - Management of media data transport

Info

Publication number: WO2025229178A1
Application number: PCT/EP2025/062065
Authority: WO
Inventors: Sungduck Chun; Kyungmin Park; Esmael Hejazi Dinan; Taehun Kim; Hsin-Hsi TSAI; Jian Xu
Original assignee: Koninklijke Philips NV
Current assignee: Koninklijke Philips NV
Priority date: 2024-05-02
Filing date: 2025-05-02
Publication date: 2025-11-06
Anticipated expiration: 2026-11-02

Abstract

The invention relates to a method comprising: receiving or determining, by a wireless device, one or more configuration parameters, the one or more configuration parameters comprising an indication to retransmit a radio link control (RLC) service data unit (SDU) in response to the RLC SDU becoming delay-critical; and retransmitting, by the wireless device, based on one or more conditions being met, the RLC SDU, after the RLC SDU becomes delay-critical.

Description

Management of Media Data Transport

FIELD OF THE INVENTION

[0001] This invention and its embodiments relate to the data packets transmission and retransmission in a network, such as a wireless network. It is more specifically related to time constraints pertaining to such transmissions and retransmissions for example depending on the application to which the data packets belong.

SUMMARY OF THE INVENTION

[0002] It is an aim of the invention to reduce the risk of waste of resources for data transmission.

[0003] It is another aim of the invention to provide a mechanism to allow for taking into account delay relative to the data packets.

[0004] It is another aim of the invention to provide a mechanism allowing timely retransmission of data packet without causing waste of resources or congestion.

[0005] In a first aspect of the invention, it is proposed a method comprising: receiving or determining, by a wireless device, one or more configuration parameters, the one or more configuration parameters comprising an indication to retransmit a radio link control (RLC) service data unit (SDU) in response to the RLC SDU becoming delay-critical; and retransmit, by the wireless device, based on one or more conditions being met, the RLC SDU, after the RLC SDU becomes delay-critical.

[0006] In a first variant of the first aspect, the one or more configuration parameters comprises a time value for a first timer, the first timer being a delay-critical timer for a radio link control (RLC) service data unit (SDU).

[0007] In a second variant of the first aspect, the one or more configuration parameters comprises a time value for a first timer, the first timer being used to determine whether a radio link control (RLC) service data unit (SDU) is delay-critical.

[0008] In another variant, the method comprises the wireless device determining whether the RLC SDU becomes delay-critical.

[0009] In another variant, the method comprises the wireless device starting the first timer with a first timer value, upon reception (or generation), by the wireless device, of the RLC SDU from an application of the wireless device.

[0010] In another variant, the method comprises the wireless device waiting for a negative and/or positive acknowledgement to trigger a retransmission of the RLC SDU for a time duration (or while the timer is above a threshold), the wireless device retransmitting the RLC SDU after this time duration passes (or once the timer has become lower than a threshold).

[0011] In a second aspect of the invention, it is proposed a method comprising: receiving, by a wireless device from a base station, one or more configuration parameters, the one or more configuration parameters comprising a time value for a timer, the timer being defined to prohibit retransmission of a radio link control (RLC) service data unit (SDU); and retransmitting, by the wireless device, the RLC SDU, based on determining: that the RLC SDU becomes delay-critical; and expiry of the timer of the RLC SDU.

[0012] In a third aspect of the invention, it is proposed a method comprising: receiving, by a wireless device from a base station, one or more configuration parameters, the one or more configuration parameters comprising a time value for a timer, the timer being defined to prohibit retransmission of a radio link control (RLC) service data unit (SDU); and retransmitting, by the wireless device, the RLC SDU, based on determining: that the RLC SDU becomes delay-critical; and the timer of the RLC SDU is not running.

[0013] In a variant of the second or third aspects, the timer is at least one of a prohibit timer, a retransmission prohibit timer, a delay-critical retransmission timer or a delay-critical retransmission timer.

[0014] In a variant of any of the first to third aspects, the wireless device starts the timer in response to transmitting a RLC protocol data unit (PDU), the RLC PDU comprising at least one of a segment of the RLC SDU or the RLC SDU.

[0015] In another variant, the method comprises the wireless device receiving, from the base station, an acknowledgment for the RLC SDU, the acknowledgement being one of at least a positive acknowledgement and a negative acknowledgement, in response to the acknowledgement being a positive acknowledgement, the wireless device stopping the timer, and in response to the acknowledgement being a negative acknowledgement, the wireless device not stopping the timer.

[0016] In another variant of the first to third aspects, the method comprises the wireless device receiving an indication that the RLC SDU is discarded, the wireless device stopping the timer in response to receiving an indication that the RLC SDU is discarded.

[0017] In another variant, the one or more conditions comprises a first condition that the RLC SDU becomes delay-critical. Optionally, the RLC SDU may become delay critical, if a remaining time of the RLC SDU becomes equal to or less than a first value, or if a first timer of the RLC SDU expires. Optionally, the one or more configuration parameters comprises the first value indicating a first threshold.

[0018] In another variant, the method comprises the wireless device starting the first timer with a first timer value, upon reception (or generation), by the wireless device, of the RLC SDU from an application of the wireless device. Optionally, the one or more configuration parameters comprise the first timer value. Optionally, a RLC entity of the wireless device starts the timer with the first timer value.

[0019] In an option of any the last two preceding variants and their options, the one or more configuration parameters comprises a second value indicating a second threshold, wherein a PDCP entity of the wireless device uses the second threshold value to determine whether a PDCP SDU associated with the RLC SDU is delay-critical PDCP SDU.

[0020] In another variant, the one or more conditions comprises a second condition that a timer of the RLC SDU is not running. Alternatively, the one or more conditions comprises a second condition that the timer of the RLC SDU is not running if the timer is not started after expiry of the timer. Optionally, the wireless device retransmits a RLC PDU of the RLC SDU if the first condition and the second condition are met. Optionally, the RLC PDU comprises at least one of the RLC SDU or a RLC SDU segment, the RLC SDU segment comprising at least a portion of the RLC SDU.

[0021] In another variant of the first to third aspects, the method comprises the wireless device not retransmitting the RLC PDU if the first condition is met and the second condition is not met.

[0022] In another variant, the one or more conditions comprises a third condition that the wireless device receives a negative acknowledgement for the RLC SDU.

[0023] In a variant, the method comprises the wireless device retransmitting the RLC PDU, if the second condition is met and the third condition is met.

[0024] Optionally, the method comprises the wireless device retransmitting the RLC PDU, if the wireless device receives from the base station or is allocated by the base station an uplink resource, the uplink resource being scheduled for transmission of one or more RLC SDUs which is delay-critical.

[0025] In a variant of the first to third aspects, the one or more configuration parameters comprises a fourth value indicating a fourth threshold.

[0026] In another variant, the one or more conditions comprises a fourth condition that a remaining time of the RLC SDU is equal to or less than the fourth threshold.

[0027] In an option of any of the two preceding variants, the method comprises the wireless device retransmitting the RLC PDU, if the fourth condition is not met.

[0028] In a variant, the one or more configuration parameters comprises a fifth value for a fifth timer. In an option, the method comprises the wireless device starting the fifth timer with the fifth value, when the wireless device receives the RLC SDU e.g. from an application. Optionally, the remaining time of the RLC SDU is the remaining time of the fifth timer until expiry of the fifth timer.

[0029] In a fourth aspect of the invention, it is proposed a method comprising: sending, by a base station (BS) central unit (CU) to a BS distributed unit (DU), a request for one or more configuration parameters, comprising a radio link control (RLC) capability information indicating support of retransmission of one or more RLC protocol data unit (PDU) segments of a delay critical RLC service data unit (SDU); receiving, by the BS CU from the BS DU, one or more first configuration parameters configuring, the retransmission of the one or more RLC PDU segments; and sending, by the BS CU to a wireless device, the one or more configuration parameters.

[0030] In a fifth aspect of the invention, it is proposed a method comprising: receiving, by a base station (BS) distributed unit (DU) from a BS central unit (CU), a request for one or more configuration parameters, comprising a radio link control (RLC) capability information indicating support of retransmission of one or more RLC protocol data unit (PDU) segments of a delay critical RLC service data unit (SDU); sending, by the BS DU to the BS CU, one or more first configuration parameters configuring, the retransmission of the one or more RLC PDU segments; receiving, by the BS DU from the BS CU, a RLC SDU; and retransmitting, by the BS DU to a wireless device, one or more first RLC segments of the RLC SDU, in response to the RLC SDU being delay critical.

[0031] In a sixth aspect of the invention, it is proposed a method comprising: sending, by a wireless device to a base station, one or more parameter of one or more capabilities supported by the wireless device, the capabilities comprising a capability of retransmission of a delay critical radio link control (RLC) data unit (DU); receiving, by a wireless device from a base station, one or more configuration parameter of retransmission of a delay critical RLC DU; and receiving, by a wireless device from a base station, a medium access control (MAC) control element (CE) activating retransmission of a delay critical RLC DU.

[0032] In a seventh aspect of the invention, it is proposed a computer program product, storing instructions thereon which cause an apparatus to perform the steps of any of the first to sixth aspects of the invention and their variants.

[0033] In an eighth aspect of the invention, it is proposed a wireless device comprising a receiver, a transmitter, a controller, and a storage unit storing instructions which when executed by the controller cause the wireless device to be configured to: receive or determine, by a wireless device, one or more configuration parameters, the one or more configuration parameters comprising an indication to retransmit a radio link control (RLC) service data unit (SDU) in response to the RLC SDU becoming delay-critical; and retransmit, by the wireless device, based on one or more conditions being met, the RLC SDU, after the RLC SDU becomes delay-critical.

[0034] In a ninth aspect of the invention, it is proposed a wireless device comprising a receiver, a transmitter, a controller, and a storage unit storing instructions which when executed by the controller cause the wireless device to be configured to: receive, by thewireless device from a base station, one or more configuration parameters, the one or more configuration parameters comprising a time value for a timer, the timer being defined to prohibit retransmission of a radio link control (RLC) service data unit (SDU); and retransmit, by the wireless device, the RLC SDU, based on determining: that the RLC SDU becomes delay-critical; and expiry of the timer of the RLC SDU.

[0035] In a tenth aspect of the invention, it is proposed a wireless device comprising a receiver, a transmitter, a controller, and a storage unit storing instructions which when executed by the controller cause the wireless device to be configured to: receive, by the wireless device from a base station, one or more configuration parameters, the one or more configuration parameters comprising a time value for a timer, the timer being defined to prohibit retransmission of a radio link control (RLC) service data unit (SDU); and retransmit, by the wireless device, the RLC SDU, based on determining: that the RLC SDU becomes delay-critical; and the timer of the RLC SDU is not running.

[0036] In an eleventh aspect of the invention, it is proposed a base station (BS) central unit (CU) comprising a receiver, a transmitter, a controller, and a storage unit storing instructions which when executed by the controller cause the BS CU to be configured to: send, by the base station (BS) central unit (CU) to a BS distributed unit (DU), a request for one or more configuration parameters, comprising a radio link control (RLC) capability information indicating support of retransmission of one or more RLC protocol data unit (PDU) segments of a delay critical RLC service data unit (SDU); receive, by the BS CU from the BS DU, one or more first configuration parameters configuring, the retransmission of the one or more RLC PDU segments; and send, by the BS CU to a wireless device, the one or more configuration parameters.

[0037] In a twelfth aspect of the invention, it is proposed a base station (BS) distributed unit (DU) comprising a receiver, a transmitter, a controller, and a storage unit storing instructions which when executed by the controller cause the BS DU to be configured to: receive, by the base station (BS) distributed unit (DU) from a BS central unit (CU), a request for one or more configuration parameters, comprising a radio link control (RLC) capability information indicating support of retransmission of one or more RLC protocol data unit (PDU) segments of a delay critical RLC service data unit (SDU); send, by the BS DU to the BS CU, one or more first configuration parameters configuring, the retransmission of the one or more RLC PDU segments; receive, by the BS DU from the BS CU, a RLC SDU; and retransmitting, by the BS DU to a wireless device, one or more first RLC segments of the RLC SDU, in response to the RLC SDU being delay critical.

[0038] In a thirteenth aspect of the invention, it is proposed a wireless device comprising a receiver, a transmitter, a controller, and a storage unit storing instructions which when executed by the controller cause the wireless device to be configured to: send, by the wireless device to a base station, one or more parameter of one or more capabilities supported by the wireless device, the capabilities comprising a capability of retransmission of a delay critical radio link control (RLC) data unit (DU); receive, by a wireless device from a base station, one or more configuration parameter of retransmission of a delay critical RLC DU; and receive, by a wireless device from a base station, a medium access control (MAC) control element (CE) activating retransmission of a delay critical RLC DU. [0039] It is to be noted that the variants listed above may be applied equally to aspects directed to devices or methods, and may be combined one with another.

BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Examples of several of the various embodiments of the present disclosure are described herein with reference to the drawings.

[0041] FIG. 1 A and FIG. 1 B illustrate example mobile communication networks in which embodiments of the present disclosure may be implemented.

[0042] FIG. 2A and FIG. 2B respectively illustrate a New Radio (NR) user plane and control plane protocol stack.

[0043] FIG. 3 illustrates an example of services provided between protocol layers of the NR user plane protocol stack of FIG. 2A.

[0044] FIG. 4A illustrates an example downlink data flow through the NR user plane protocol stack of FIG. 2A.

[0045] FIG. 4B illustrates an example format of a MAC subheader in a MAC PDU.

[0046] FIG. 5A and FIG. 5B respectively illustrate a mapping between logical channels, transport channels, and physical channels for the downlink and uplink.

[0047] FIG. 6 is an example diagram showing RRC state transitions of a UE.

[0048] FIG. 7 illustrates an example configuration of an NR frame into which OFDM symbols are grouped.

[0049] FIG. 8 illustrates an example configuration of a slot in the time and frequency domain for an NR carrier.

[0050] FIG. 9 illustrates an example of bandwidth adaptation using three configured BWPs for an NR carrier.

[0051] FIG. 10A illustrates three carrier aggregation configurations with two component carriers.

[0052] FIG. 10B illustrates an example of how aggregated cells may be configured into one or more PUCCH groups.

[0053] FIG. 11A illustrates an example of an SS/PBCH block structure and location.

[0054] FIG. 11B illustrates an example of CSI-RSs that are mapped in the time and frequency domains.

[0055] FIG. 12A and FIG. 12B respectively illustrate examples of three downlink and uplink beam management procedures.

[0056] FIG. 13A, FIG. 13B, and FIG. 13C respectively illustrate a four-step contention-based random access procedure, a two-step contention-free random access procedure, and another two-step random access procedure. [0057] FIG. 14A illustrates an example of CORESET configurations for a bandwidth part.

[0058] FIG. 14B illustrates an example of a COE-to-REG mapping for DOI transmission on a CORESET and PDCCH processing.

[0059] FIG. 15 illustrates an example of a wireless device in communication with a base station.

[0060] FIG. 16A, FIG. 16B, FIG. 160, and FIG. 16D illustrate example structures for uplink and downlink transmission.

[0061] FIG. 17 illustrates an aspect of an example embodiment according to the present disclosure. [0062] FIG. 18 illustrates an aspect of an example embodiment according to the present disclosure.

[0063] FIG. 19 illustrates an aspect of an example embodiment according to the present disclosure.

[0064] FIG. 20 illustrates an aspect of an example embodiment according to the present disclosure.

[0065] FIG. 21 illustrates an aspect of an example embodiment according to the present disclosure.

[0066] FIG. 22 illustrates an aspect of an example embodiment according to the present disclosure.

[0067] FIG. 23 illustrates an aspect of an example embodiment according to the present disclosure.

[0068] FIG. 24 illustrates an aspect of an example embodiment according to the present disclosure.

[0069] FIG. 25 illustrates an aspect of an example embodiment according to the present disclosure.

[0070] FIG. 26 illustrates an aspect of an example embodiment according to the present disclosure.

[0071] FIG. 27 illustrates an aspect of an example embodiment according to the present disclosure.

[0072] FIG. 28 illustrates an aspect of an example embodiment according to the present disclosure.

[0073] FIG. 29 illustrates an aspect of an example embodiment according to the present disclosure.

DETAILED DESCRIPTION

[0074] In the present disclosure, various embodiments are presented as examples of how the disclosed techniques may be implemented and/or how the disclosed techniques may be practiced in environments and scenarios. It will be apparent to persons skilled in the relevant art that various changes in form and detail can be made therein without departing from the scope. In fact, after reading the description, it will be apparent to one skilled in the relevant art how to implement alternative embodiments. The present embodiments should not be limited by any of the described exemplary embodiments. The embodiments of the present disclosure will be described with reference to the accompanying drawings. Limitations, features, and/or elements from the disclosed example embodiments may be combined to create further embodiments within the scope of the disclosure. Any figures which highlight the functionality and advantages, are presented for example purposes only. The disclosed architecture is sufficiently flexible and configurable, such that it may be utilized in ways other than that shown. For example, the actions listed in any flowchart may be re-ordered or only optionally used in some embodiments.

[0075] Embodiments may be configured to operate as needed. The disclosed mechanism may be performed when certain criteria are met, for example, in a wireless device, a base station, a radio environment, a network, a combination of the above, and/or the like. Example criteria may be based, at least in part, on for example, wireless device or network node configurations, traffic load, initial system set up, packet sizes, traffic characteristics, a combination of the above, and/or the like. When the one or more criteria are met, various example embodiments may be applied. Therefore, it may be possible to implement example embodiments that selectively implement disclosed protocols. [0076] A base station may communicate with a mix of wireless devices. Wireless devices and/or base stations may support multiple technologies, and/or multiple releases of the same technology. Wireless devices may have some specific capability(ies) depending on wireless device category and/or capability(ies). When this disclosure refers to a base station communicating with a plurality of wireless devices, this disclosure may refer to a subset of the total wireless devices in a coverage area. This disclosure may refer to, for example, a plurality of wireless devices of a given LTE or 5G release with a given capability and in a given sector of the base station. The plurality of wireless devices in this disclosure may refer to a selected plurality of wireless devices, and/or a subset of total wireless devices in a coverage area which perform according to disclosed methods, and/or the like. There may be a plurality of base stations or a plurality of wireless devices in a coverage area that may not comply with the disclosed methods, for example, those wireless devices or base stations may perform based on older releases of LTE or 5G technology.

[0077] In this disclosure, “a” and “an” and similar phrases are to be interpreted as “at least one” and “one or more.” Similarly, any term that ends with the suffix “(s)” is to be interpreted as “at least one” and “one or more.” In this disclosure, the term “may” is to be interpreted as “may, for example.” In other words, the term “may” is indicative that the phrase following the term “may” is an example of one of a multitude of suitable possibilities that may, or may not, be employed by one or more of the various embodiments. The terms “comprises” and “consists of”, as used herein, enumerate one or more components of the element being described. The term “comprises” is interchangeable with “includes” and does not exclude unenumerated components from being included in the element being described. By contrast, “consists of” provides a complete enumeration of the one or more components of the element being described. The term “based on”, as used herein, should be interpreted as “based at least in part on” rather than, for example, “based solely on”. The term “and/or” as used herein represents any possible combination of enumerated elements. For example, “A, B, and/or C” may represent A; B; C; A and B; A and C; B and 0; or A, B, and 0.

[0078] If A and B are sets and every element of A is an element of B, A is called a subset of B. In this specification, only non-empty sets and subsets are considered. For example, possible subsets of B = {celH , cell2} are: {celH }, {cell2}, and {celH , cell2}. The phrase “based on” (or equally “based at least on”) is indicative that the phrase following the term “based on” is an example of one of a multitude of suitable possibilities that may, or may not, be employed to one or more of the various embodiments. The phrase “in response to” (or equally “in response at least to”) is indicative that the phrase following the phrase “in response to” is an example of one of a multitude of suitable possibilities that may, or may not, be employed to one or more of the various embodiments. The phrase “depending on” (or equally “depending at least to”) is indicative that the phrase following the phrase “depending on” is an example of one of a multitude of suitable possibilities that may, or may not, be employed to one or more of the various embodiments. The phrase “employin g/using” (or equally “employing/using at least”) is indicative that the phrase following the phrase “employin g/using” is an example of one of a multitude of suitable possibilities that may, or may not, be employed to one or more of the various embodiments.

[0079] The term configured may relate to the capacity of a device whether the device is in an operational or non- operational state. Configured may refer to specific settings in a device that affect or implement the operational characteristics of the device whether the device is in an operational or non-operational state. In other words, the hardware, software, firmware, registers, memory values, and/or the like may be “configured” within a device, whether the device is in an operational or nonoperational state, to provide the device with specific characteristics. Terms such as “a control message to cause in a device” may mean that a control message has parameters that may be used to configure specific characteristics or may be used to implement certain actions in the device, whether the device is in an operational or non-operational state.

[0080] In this disclosure, parameters (or equally called, fields, or Information elements: lEs) may comprise one or more information objects, and an information object may comprise one or more other objects. For example, if parameter (IE) N comprises parameter (IE) M, and parameter (IE) M comprises parameter (IE) K, and parameter (IE) K comprises parameter (information element) J. Then, for example, N comprises K, and N comprises J. In an example embodiment, when one or more messages comprise a plurality of parameters, it implies that a parameter in the plurality of parameters is in at least one of the one or more messages, but does not have to be in each of the one or more messages.

[0081] Many features presented are described as being optional through the use of “may” or the use of parentheses. For the sake of brevity and legibility, the present disclosure does not explicitly recite each and every permutation that may be obtained by choosing from the set of optional features. The present disclosure is to be interpreted as explicitly disclosing all such permutations. For example, a system described as having three optional features may be embodied in seven ways, namely with just one of the three possible features, with any two of the three possible features or with three of the three possible features.

[0082] Many of the elements described in the disclosed embodiments may be implemented as modules. A module is defined here as an element that performs a defined function and has a defined interface to other elements. The modules described in this disclosure may be implemented in hardware, software in combination with hardware, firmware, wetware (e.g. hardware with a biological element) or a combination thereof, which may be behaviorally equivalent. For example, modules may be implemented as a software routine written in a computer language configured to be executed by a hardware machine (such as C, C++, Fortran, Java, Basic, MATLAB or the like) or a modeling/simulation program such as Simulink, Stateflow, GNU Octave, or LabVI EWMathScript. It may be possible to implement modules using physical hardware that incorporates discrete or programmable analog, digital and/or quantum hardware. Examples of programmable hardware comprise: computers, microcontrollers, microprocessors, applicationspecific integrated circuits (ASICs); field programmable gate arrays (FPGAs); and complex programmable logic devices (OPLDs). Computers, microcontrollers and microprocessors are programmed using languages such as assembly, C, C++ or the like. FPGAs, ASICs and CPLDs are often programmed using hardware description languages (HDL) such as VHSIC hardware description language (VHDL) or Verilog that configure connections between internal hardware modules with lesser functionality on a programmable device. The mentioned technologies are often used in combination to achieve the result of a functional module.

[0083] FIG. 1A illustrates an example of a mobile communication network 100 in which embodiments of the present disclosure may be implemented. The mobile communication network 100 may be, for example, a public land mobile network (PLMN) run by a network operator. As illustrated in FIG. 1A, the mobile communication network 100 includes a core network (ON) 102, a radio access network (RAN) 104, and a wireless device 106.

[0084] The ON 102 may provide the wireless device 106 with an interface to one or more data networks (DNs), such as public DNs (e.g., the Internet), private DNs, and/or intra-operator DNs. As part of the interface functionality, the ON 102 may set up end-to-end connections between the wireless device 106 and the one or more DNs, authenticate the wireless device 106, and provide charging functionality.

[0085] The RAN 104 may connect the ON 102 to the wireless device 106 through radio communications over an air interface. As part of the radio communications, the RAN 104 may provide scheduling, radio resource management, and retransmission protocols. The communication direction from the RAN 104 to the wireless device 106 over the air interface is known as the downlink and the communication direction from the wireless device 106 to the RAN 104 over the air interface is known as the uplink. Downlink transmissions may be separated from uplink transmissions using frequency division duplexing (FDD), time-division duplexing (TDD), and/or some combination of the two duplexing techniques.

[0086] The term wireless device may be used throughout this disclosure to refer to and encompass any mobile device or fixed (non-mobile) device for which wireless communication is needed or usable. For example, a wireless device may be a telephone, smart phone, tablet, computer, laptop, sensor, meter, wearable device, Internet of Things (loT) device, vehicle roadside unit (RSU), relay node, automobile, and/or any combination thereof. The term wireless device encompasses other terminology, including user equipment (UE), user terminal (UT), access terminal (AT), mobile station, handset, wireless transmit and receive unit (WTRU), and/or wireless communication device.

[0087] The RAN 104 may include one or more base stations (not shown). The term base station may be used throughout this disclosure to refer to and encompass a Node B (associated with UMTS and/or 3G standards), an Evolved Node B (eNB, associated with E-UTRA and/or 4G standards), a remote radio head (RRH), a baseband processing unit coupled to one or more RRHs, a repeater node or relay node used to extend the coverage area of a donor node, a Next Generation Evolved Node B (ng-eNB), a Generation Node B (gNB, associated with NR and/or 5G standards), an access point (AP, associated with, for example, Wi-Fi or any other suitable wireless communication standard), and/or any combination thereof. A base station may comprise at least one gNB Central Unit (gNB-CU) and at least one a gNB Distributed Unit (gNB-DU).

[0088] A base station included in the RAN 104 may include one or more sets of antennas for communicating with the wireless device 106 over the air interface. For example, one or more of the base stations may include three sets of antennas to respectively control three cells (or sectors). The size of a cell may be determined by a range at which a receiver (e.g., a base station receiver) can successfully receive the transmissions from a transmitter (e.g., a wireless device transmitter) operating in the cell. Together, the cells of the base stations may provide radio coverage to the wireless device 106 over a wide geographic area to support wireless device mobility. [0089] In addition to three-sector sites, other implementations of base stations are possible. For example, one or more of the base stations in the RAN 104 may be implemented as a sectored site with more or less than three sectors. One or more of the base stations in the RAN 104 may be implemented as an access point, as a baseband processing unit coupled to several remote radio heads (RRHs), and/or as a repeater or relay node used to extend the coverage area of a donor node. A baseband processing unit coupled to RRHs may be part of a centralized or cloud RAN architecture, where the baseband processing unit may be either centralized in a pool of baseband processing units or virtualized. A repeater node may amplify and rebroadcast a radio signal received from a donor node. A relay node may perform the same/similar functions as a repeater node but may decode the radio signal received from the donor node to remove noise before amplifying and rebroadcasting the radio signal.

[0090] The RAN 104 may be deployed as a homogenous network of macrocell base stations that have similar antenna patterns and similar high-level transmit powers. The RAN 104 may be deployed as a heterogeneous network. In heterogeneous networks, small cell base stations may be used to provide small coverage areas, for example, coverage areas that overlap with the comparatively larger coverage areas provided by macrocell base stations. The small coverage areas may be provided in areas with high data traffic (or so-called “hotspots”) or in areas with weak macrocell coverage. Examples of small cell base stations include, in order of decreasing coverage area, microcell base stations, picocell base stations, and femtocell base stations or home base stations.

[0091] The Third-Generation Partnership Project (3GPP) was formed in 1998 to provide global standardization of specifications for mobile communication networks similar to the mobile communication network 100 in FIG. 1A. To date, 3GPP has produced specifications for three generations of mobile networks: a third generation (3G) network known as Universal Mobile Telecommunications System (UMTS), a fourth generation (4G) network known as Long-Term Evolution (LTE), and a fifth generation (5G) network known as 5G System (5GS). Embodiments of the present disclosure are described with reference to the RAN of a 3GPP 5G network, referred to as next-generation RAN (NG- RAN). Embodiments may be applicable to RANs of other mobile communication networks, such as the RAN 104 in FIG. 1A, the RANs of earlier 3G and 4G networks, and those of future networks yet to be specified (e.g., a3GPP 6G network). NG-RAN implements 5G radio access technology known as New Radio (NR) and may be provisioned to implement 4G radio access technology or other radio access technologies, including non-3GPP radio access technologies.

[0092] FIG. 1 B illustrates another example mobile communication network 150 in which embodiments of the present disclosure may be implemented. Mobile communication network 150 may be, for example, a PLMN run by a network operator. As illustrated in FIG. 1B, mobile communication network 150 includes a 5G core network (5G-CN) 152, an NG-RAN 154, and UEs 156A and 156B (collectively UEs 156). These components may be implemented and operate in the same or similar manner as corresponding components described with respect to FIG. 1A.

[0093] The 5G-CN 152 provides the UEs 156 with an interface to one or more DNs, such as public DNs (e.g., the Internet), private DNs, and/or intra-operator DNs. As part of the interface functionality, the 5G-CN 152 may set up end- to-end connections between the UEs 156 and the one or more DNs, authenticate the UEs 156, and provide charging functionality. Compared to the ON of a 3GPP 4G network, the basis of the 5G-CN 152 may be a service-based architecture. This means that the architecture of the nodes making up the 5G-CN 152 may be defined as network functions that offer services via interfaces to other network functions. The network functions of the 5G-CN 152 may be implemented in several ways, including as network elements on dedicated or shared hardware, as software instances running on dedicated or shared hardware, or as virtualized functions instantiated on a platform (e.g., a cloud-based platform).

[0094] As illustrated in FIG. 1B, the 5G-CN 152 includes an Access and Mobility Management Function (AMF) 158A and a User Plane Function (UPF) 158B, which are shown as one component AMF/UPF 158 in FIG. 1 B for ease of illustration. The UPF 158B may serve as a gateway between the NG-RAN 154 and the one or more DNs. The UPF 158B may perform functions such as packet routing and forwarding, packet inspection and user plane policy rule enforcement, traffic usage reporting, uplink classification to support routing of traffic flows to the one or more DNs, quality of service (QoS) handling for the user plane (e.g., packet filtering, gating, uplink/downlink rate enforcement, and uplink traffic verification), downlink packet buffering, and downlink data notification triggering. The UPF 158B may serve as an anchor point for intra-Zinter-Radio Access Technology (RAT) mobility, an external protocol (or packet) data unit (PDU) session point of interconnect to the one or more DNs, and/or a branching point to support a multi-homed PDU session. The UEs 156 may be configured to receive services through a PDU session, which is a logical connection between a UE and a DN.

[0095] The AMF 158A may perform functions such as Non-Access Stratum (NAS) signaling termination, NAS signaling security, Access Stratum (AS) security control, inter-CN node signaling for mobility between 3GPP access networks, idle mode UE reachability (e.g., control and execution of paging retransmission), registration area management, intra-system and inter-system mobility support, access authentication, access authorization including checking of roaming rights, mobility management control (subscription and policies), network slicing support, and/or session management function (SMF) selection. NAS may refer to the functionality operating between a ON and a UE, and AS may refer to the functionality operating between the UE and a RAN.

[0096] The 5G-CN 152 may include one or more additional network functions that are not shown in FIG. 1B for the sake of clarity. For example, the 5G-CN 152 may include one or more of a Session Management Function (SMF), an NR Repository Function (NRF), a Policy Control Function (PCF), a Network Exposure Function (NEF), a Unified Data Management (UDM), an Application Function (AF), and/or an Authentication Server Function (AUSF).

[0097] The NG-RAN 154 may connect the 5G-CN 152 to the UEs 156 through radio communications over the air interface. The NG-RAN 154 may include one or more gNBs, illustrated as gNB 160A and gNB 160B (collectively gNBs 160) and/or one or more ng-eNBs, illustrated as ng-eNB 162A and ng-eNB 162B (collectively ng-eNBs 162). The gNBs 160 and ng-eNBs 162 may be more generically referred to as base stations. The gNBs 160 and ng-eNBs 162 may include one or more sets of antennas for communicating with the UEs 156 over an air interface. For example, one or more of the gNBs 160 and/or one or more of the ng-eNBs 162 may include three sets of antennas to respectively control three cells (or sectors). Together, the cells of the gNBs 160 and the ng-eNBs 162 may provide radio coverage to the UEs 156 over a wide geographic area to support UE mobility.

[0098] As shown in FIG. 1 B, the gNBs 160 and/or the ng-eNBs 162 may be connected to the 5G-CN 152 by means of an NG interface and to other base stations by an Xn interface. The NG and Xn interfaces may be established using direct physical connections and/or indirect connections over an underlying transport network, such as an internet protocol (IP) transport network. The gNBs 160 and/or the ng-eNBs 162 may be connected to the UEs 156 by means of a Uu interface. For example, as illustrated in FIG. 1B, gNB 160A may be connected to the UE 156A by means of a Uu interface. The NG, Xn, and Uu interfaces are associated with a protocol stack. The protocol stacks associated with the interfaces may be used by the network elements in FIG. 1 B to exchange data and signaling messages and may include two planes: a user plane and a control plane. The user plane may handle data of interest to a user. The control plane may handle signaling messages of interest to the network elements.

[0099] The gNBs 160 and/or the ng-eNBs 162 may be connected to one or more AMF/UPF functions of the 5G-CN 152, such as the AMF/UPF 158, by means of one or more NG interfaces. For example, the gNB 160A may be connected to the UPF 158B of the AMF/UPF 158 by means of an NG-User plane (NG-U) interface. The NG-U interface may provide delivery (e.g., non-guaranteed delivery) of user plane PDUs between the gNB 160A and the UPF 158B. The gNB 160A may be connected to the AMF 158A by means of an NG-Control plane (NG-C) interface. The NG-0 interface may provide, for example, NG interface management, UE context management, UE mobility management, transport of NAS messages, paging, PDU session management, and configuration transfer and/or warning message transmission.

[0100] The gNBs 160 may provide NR user plane and control plane protocol terminations towards the UEs 156 over the Uu interface. For example, the gNB 160A may provide NR user plane and control plane protocol terminations toward the UE 156A over a Uu interface associated with a first protocol stack. The ng-eNBs 162 may provide Evolved UMTS Terrestrial Radio Access (E-UTRA) user plane and control plane protocol terminations towards the UEs 156 over a Uu interface, where E-UTRA refers to the 3GPP 4G radio-access technology. For example, the ng-eNB 162B may provide E-UTRA user plane and control plane protocol terminations towards the UE 156B over a Uu interface associated with a second protocol stack.

[0101] The 5G-CN 152 was described as being configured to handle NR and 4G radio accesses. It will be appreciated by one of ordinary skill in the art that it may be possible for NR to connect to a 4G core network in a mode known as “non-standalone operation.” In non-standalone operation, a 4G core network is used to provide (or at least support) control-plane functionality (e.g., initial access, mobility, and paging). Although only one AMF/UPF 158 is shown in FIG. 1B, one gNB or ng-eNB may be connected to multiple AMF/UPF nodes to provide redundancy and/or to load share across the multiple AMF/UPF nodes. [0102] As discussed, an interface (e.g. , Uu, Xn, and NG interfaces) between the network elements in FIG. 1 B may be associated with a protocol stack that the network elements use to exchange data and signaling messages. A protocol stack may include two planes: a user plane and a control plane. The user plane may handle data of interest to a user, and the control plane may handle signaling messages of interest to the network elements.

[0103] FIG. 2A and FIG. 2B respectively illustrate examples of NR user plane and NR control plane protocol stacks for the Uu interface that lies between a UE 210 and a gNB 220. The protocol stacks illustrated in FIG. 2A and FIG. 2B may be the same or similar to those used for the Uu interface between, for example, the UE 156A and the gNB 160A shown in FIG. 1B.

[0104] FIG. 2A illustrates a NR user plane protocol stack comprising five layers implemented in the UE 210 and the gNB 220. At the bottom of the protocol stack, physical layers (PHYs) 211 and 221 may provide transport services to the higher layers of the protocol stack and may correspond to layer 1 of the Open Systems Interconnection (OSI) model. The next four protocols above PHYs 211 and 221 comprise media access control layers (MAGs) 212 and 222, radio link control layers (RLCs) 213 and 223, packet data convergence protocol layers (PDOPs) 214 and 224, and service data application protocol layers (SDAPs) 215 and 225. Together, these four protocols may make up layer 2, or the data link layer, of the OSI model.

[0105] FIG. 3 illustrates an example of services provided between protocol layers of the NR user plane protocol stack. Starting from the top of FIG. 2A and FIG. 3, the SDAPs 215 and 225 may perform QoS flow handling. The UE 210 may receive services through a PDU session, which may be a logical connection between the UE 210 and a DN. The PDU session may have one or more QoS flows. A UPF of a CN (e.g., the UPF 158B) may map IP packets to the one or more QoS flows of the PDU session based on QoS requirements (e.g., in terms of delay, data rate, and/or error rate). The SDAPs 215 and 225 may perform mapping/de-mapping between the one or more QoS flows and one or more data radio bearers. The mapping/de-mapping between the QoS flows and the data radio bearers may be determined by the SDAP 225 at the gNB 220. The SDAP 215 at the UE 210 may be informed of the mapping between the QoS flows and the data radio bearers through reflective mapping or control signaling received from the gNB 220. For reflective mapping, the SDAP 225 at the gNB 220 may mark the downlink packets with a QoS flow indicator (QFI), which may be observed by the SDAP 215 at the UE 210 to determine the mapping/de-mapping between the QoS flows and the data radio bearers.

[0106] The PDCPs 214 and 224 may perform header compression/decompression to reduce the amount of data that needs to be transmitted over the air interface, ciphering/deciphering to prevent unauthorized decoding of data transmitted over the air interface, and integrity protection (to ensure control messages originate from intended sources. The PDCPs 214 and 224 may perform retransmissions of undelivered packets, in-sequence delivery and reordering of packets, and removal of packets received in duplicate due to, for example, an intra-gNB handover. The PDCPs 214 and 224 may perform packet duplication to improve the likelihood of the packet being received and, at the receiver, remove any duplicate packets. Packet duplication may be useful for services that require high reliability. [0107] Although not shown in FIG. 3, PDOPs 214 and 224 may perform mapping/de-mapping between a split radio bearer and RLC channels in a dual connectivity scenario. Dual connectivity is a technique that allows a UE to connect to two cells or, more generally, two cell groups: a master cell group (MCG) and a secondary cell group (SCG). A split bearer is when a single radio bearer, such as one of the radio bearers provided by the PDOPs 214 and 224 as a service to the SDAPs 215 and 225, is handled by cell groups in dual connectivity. The PDOPs 214 and 224 may map/de-map the split radio bearer between RLC channels belonging to cell groups.

[0108] The RLCs 213 and 223 may perform segmentation, retransmission through Automatic Repeat Request (ARQ), and removal of duplicate data units received from MACs 212 and 222, respectively. The RLCs 213 and 223 may support three transmission modes: transparent mode (TM); unacknowledged mode (UM); and acknowledged mode (AM). Based on the transmission mode an RLC is operating, the RLC may perform one or more of the noted functions. The RLC configuration may be per logical channel with no dependency on numerologies and/or Transmission Time Interval (TTI) durations. As shown in FIG. 3, the RLCs 213 and 223 may provide RLC channels as a service to PDCPs 214 and 224, respectively.

[0109] The MACs 212 and 222 may perform multiplexing/demultiplexing of logical channels and/or mapping between logical channels and transport channels. The multiplexing/demultiplexing may include multiplexing/demultiplexing of data units, belonging to the one or more logical channels, into/from Transport Blocks (TBs) delivered to/from the PHYs

211 and 221. The MAC 222 may be configured to perform scheduling, scheduling information reporting, and priority handling between UEs by means of dynamic scheduling. Scheduling may be performed in the g N B 220 (at the MAC 222) for downlink and uplink. The MACs 212 and 222 may be configured to perform error correction through Hybrid Automatic Repeat Request (HARQ) (e.g., one HARQ entity per carrier in case of Carrier Aggregation (CA)), priority handling between logical channels of the UE 210 by means of logical channel prioritization, and/or padding. The MACs

212 and 222 may support one or more numerologies and/or transmission timings. In an example, mapping restrictions in a logical channel prioritization may control which numerology and/or transmission timing a logical channel may use. As shown in FIG. 3, the MACs 212 and 222 may provide logical channels as a service to the RLCs 213 and 223.

[0110] The PHYs 211 and 221 may perform mapping of transport channels to physical channels and digital and analog signal processing functions for sending and receiving information over the air interface. These digital and analog signal processing functions may include, for example, coding/decoding and modulation/demodulation. The PHYs 211 and 221 may perform multi-antenna mapping. As shown in FIG. 3, the PHYs 211 and 221 may provide one or more transport channels as a service to the MACs 212 and 222.

[0111] FIG. 4A illustrates an example downlink data flow through the NR user plane protocol stack. FIG. 4A illustrates a downlink data flow of three IP packets (n, n+1, and m) through the NR user plane protocol stack to generate two TBs at the gNB 220. An uplink data flow through the NR user plane protocol stack may be similar to the downlink data flow depicted in FIG. 4A. [0112] The downlink data flow of FIG. 4A begins when SDAP 225 receives the three IP packets from one or more QoS flows and maps the three packets to radio bearers. In FIG. 4A, the SDAP 225 maps IP packets n and n+1 to a first radio bearer 402 and maps IP packet m to a second radio bearer 404. An SDAP header (labeled with an “H” in FIG. 4A) is added to an IP packet. The data unit from/to a higher protocol layer is referred to as a service data unit (SDU) of the lower protocol layer and the data unit to/from a lower protocol layer is referred to as a protocol data unit (PDU) of the higher protocol layer. As shown in FIG. 4A, the data unit from the SDAP 225 is an SDU of lower protocol layer PDCP 224 and is a PDU of the SDAP 225.

[0113] The remaining protocol layers in FIG. 4A may perform their associated functionality (e.g. , with respect to FIG. 3), add corresponding headers, and forward their respective outputs to the next lower layer. For example, the PDCP 224 may perform IP-header compression and ciphering and forward its output to the RLC 223. The RLC 223 may optionally perform segmentation (e.g., as shown for IP packet m in FIG. 4A) and forward its output to the MAC 222. The MAC 222 may multiplex a number of RLC PDUs and may attach a MAC subheader to an RLC PDU to form a transport block. In NR, the MAC subheaders may be distributed across the MAC PDU, as illustrated in FIG. 4A. In LTE, the MAC subheaders may be entirely located at the beginning of the MAC PDU. The NR MAC PDU structure may reduce processing time and associated latency because the MAC PDU subheaders may be computed before the full MAC PDU is assembled.

[0114] FIG. 4B illustrates an example format of a MAC subheader in a MAC PDU. The MAC subheader includes: an SDU length field for indicating the length (e.g., in bytes) of the MAC SDU to which the MAC subheader corresponds; a logical channel identifier (LCID) field for identifying the logical channel from which the MAC SDU originated to aid in the demultiplexing process; a flag (F) for indicating the size of the SDU length field; and a reserved bit (R) field for future use.

[0115] FIG. 4B further illustrates MAC control elements (CEs) inserted into the MAC PDU by a MAC, such as MAC 223 or MAC 222. For example, FIG. 4B illustrates two MAC CEs inserted into the MAC PDU. MAC CEs may be inserted at the beginning of a MAC PDU for downlink transmissions (as shown in FIG. 4B) and at the end of a MAC PDU for uplink transmissions. MAC CEs may be used for in-band control signaling. Example MAC CEs include: scheduling-related MAC CEs, such as buffer status reports and power headroom reports; activation/deactivation MAC CEs, such as those for activation/deactivation of PDCP duplication detection, channel state information (CSI) reporting, sounding reference signal (SRS) transmission, and prior configured components; discontinuous reception (DRX) related MAC CEs; timing advance MAC CEs; and random access related MAC CEs. A MAC CE may be preceded by a MAC subheader with a similar format as described for MAC SDUs and may be identified with a reserved value in the LCID field that indicates the type of control information included in the MAC CE.

[0116] Before describing the NR control plane protocol stack, logical channels, transport channels, and physical channels are first described as well as a mapping between the channel types. One or more of the channels may be used to carry out functions associated with the NR control plane protocol stack described later below. [0117] FIG. 5A and FIG. 5B illustrate, for downlink and uplink respectively, a mapping between logical channels, transport channels, and physical channels. Information is passed through channels between the RLC, the MAC, and the PHY of the NR protocol stack. A logical channel may be used between the RLC and the MAC and may be classified as a control channel that carries control and configuration information in the NR control plane or as a traffic channel that carries data in the NR user plane. A logical channel may be classified as a dedicated logical channel that is dedicated to a specific UE or as a common logical channel that may be used by more than one UE. A logical channel may also be defined by the type of information it carries. The set of logical channels defined by NR include, for example: [0118] - a paging control channel (POOH) for carrying paging messages used to page a UE whose location is not known to the network on a cell level;

[0119] - a broadcast control channel (BOOH) for carrying system information messages in the form of a master information block (MIB) and several system information blocks (SIBs), wherein the system information messages may be used by the UEs to obtain information about how a cell is configured and how to operate within the cell;

[0120] - a common control channel (COCH) for carrying control messages together with random access;

[0121] - a dedicated control channel (DOCH) for carrying control messages to/from a specific the UE to configure the UE; and

[0122] - a dedicated traffic channel (DTCH) for carrying user data to/from a specific the UE.

[0123] Transport channels are used between the MAC and PHY layers and may be defined by how the information they carry is transmitted over the air interface. The set of transport channels defined by NR include, for example: [0124] - a paging channel (PCH) for carrying paging messages that originated from the PCCH;

[0125] - a broadcast channel (BOH) for carrying the MIB from the BCCH;

[0126] - a downlink shared channel (DL-SCH) for carrying downlink data and signaling messages, including the SIBs from the BCCH;

[0127] -- an uplink shared channel (UL-SCH) for carrying uplink data and signaling messages; and

[0128] - a random access channel (RACH) for allowing a UE to contact the network without any prior scheduling. [0129] The PHY may use physical channels to pass information between processing levels of the PHY. A physical channel may have an associated set of time-frequency resources for carrying the information of one or more transport channels. The PHY may generate control information to support the low-level operation of the PHY and provide the control information to the lower levels of the PHY via physical control channels, known as L1/L2 control channels. The set of physical channels and physical control channels defined by NR include, for example:

[0130] -- a physical broadcast channel (PBOH) for carrying the MIB from the BOH;

[0131] -- a physical downlink shared channel (PDSCH) for carrying downlink data and signaling messages from the DL-SCH, as well as paging messages from the PCH;

[0132] -- a physical downlink control channel (PDCCH) for carrying downlink control information (DCI), which may include downlink scheduling commands, uplink scheduling grants, and uplink power control commands; [0133] -- a physical uplink shared channel (PUSCH) for carrying uplink data and signaling messages from the UL- SCH and in some instances uplink control information (UCI) as described below;

[0134] -- a physical uplink control channel (PUCCH) for carrying UCI, which may include HARQ acknowledgments, channel quality indicators (CQI), pre-coding matrix indicators (PMI), rank indicators (Rl), and scheduling requests (SR); and

[0135] -- a physical random access channel (PRACH) for random access.

[0136] Similar to the physical control channels, the physical layer generates physical signals to support the low-level operation of the physical layer. As shown in FIG. 5A and FIG. 5B, the physical layer signals defined by NR include: primary synchronization signals (PSS), secondary synchronization signals (SSS), channel state information reference signals (CSI-RS), demodulation reference signals (DMRS), sounding reference signals (SRS), and phase-tracking reference signals (PT-RS). These physical layer signals will be described in greater detail below.

[0137] FIG. 2B illustrates an example NR control plane protocol stack. As shown in FIG. 2B, the NR control plane protocol stack may use the same/similar first four protocol layers as the example NR user plane protocol stack. These four protocol layers include the PHYs 211 and 221 , the MAGs 212 and 222, the RLCs 213 and 223, and the PDOPs 214 and 224. Instead of having the SDAPs 215 and 225 at the top of the stack as in the NR user plane protocol stack, the NR control plane stack has radio resource controls (RRCs) 216 and 226 and NAS protocols 217 and 237 at the top of the NR control plane protocol stack.

[0138] The NAS protocols 217 and 237 may provide control plane functionality between the UE 210 and the AMF 230 (e.g., the AMF 158A) or, more generally, between the UE 210 and the ON. The NAS protocols 217 and 237 may provide control plane functionality between the UE 210 and the AMF 230 via signaling messages, referred to as NAS messages. There is no direct path between the UE 210 and the AMF 230 through which the NAS messages can be transported. The NAS messages may be transported using the AS of the Uu and NG interfaces. NAS protocols 217 and 237 may provide control plane functionality such as authentication, security, connection setup, mobility management, and session management.

[0139] The RRCs 216 and 226 may provide control plane functionality between the UE 210 and the gNB 220 or, more generally, between the UE 210 and the RAN. The RRCs 216 and 226 may provide control plane functionality between the UE 210 and the gNB 220 via signaling messages, referred to as RRC messages. RRC messages may be transmitted between the UE 210 and the RAN using signaling radio bearers and the same/similar PDCP, RLC, MAC, and PHY protocol layers. The MAC may multiplex control-plane and user-plane data into the same transport block (TB). The RRCs 216 and 226 may provide control plane functionality such as: broadcast of system information related to AS and NAS; paging initiated by the CN or the RAN; establishment, maintenance and release of an RRC connection between the UE 210 and the RAN; security functions including key management; establishment, configuration, maintenance and release of signaling radio bearers and data radio bearers; mobility functions; QoS management functions; the UE measurement reporting and control of the reporting; detection of and recovery from radio link failure (RLF); and/or NAS message transfer. As part of establishing an RRC connection, RRCs 216 and 226 may establish an RRC context, which may involve configuring parameters for communication between the UE 210 and the RAN.

[0140] FIG. 6 is an example diagram showing RRC state transitions of a UE. The UE may be the same or similar to the wireless device 106 depicted in FIG. 1A, the UE 210 depicted in FIG. 2A and FIG. 2B, or any other wireless device described in the present disclosure. As illustrated in FIG. 6, a UE may be in at least one of three RRC states: RRC connected 602 (e.g., RRC_CONNECTED), RRC idle 604 (e.g., RRC_I DLE), and RRC inactive 606 (e.g., RRCJNACTIVE).

[0141] In RRC connected 602, the UE has an established RRC context and may have at least one RRC connection with a base station. The base station may be similar to one of the one or more base stations included in the RAN 104 depicted in FIG. 1A, one of the gNBs 160 orng-eNBs 162 depicted in FIG. 1B, the gNB 220 depicted in FIG. 2A and FIG. 2B, or any other base station described in the present disclosure. The base station with which the UE is connected may have the RRC context for the UE. The RRC context, referred to as the UE context, may comprise parameters for communication between the UE and the base station. These parameters may include, for example: one or more AS contexts; one or more radio link configuration parameters; bearer configuration information (e.g., relating to a data radio bearer, signaling radio bearer, logical channel, QoS flow, and/or PDU session); security information; and/or PHY, MAC, RLC, PDCP, and/or SDAP layer configuration information. While in RRC connected 602, mobility of the UE may be managed by the RAN (e.g., the RAN 104 or the NG-RAN 154). The UE may measure the signal levels (e.g., reference signal levels) from a serving cell and neighboring cells and report these measurements to the base station currently serving the UE. The UE’s serving base station may request a handover to a cell of one of the neighboring base stations based on the reported measurements. The RRC state may transition from RRC connected 602 to RRC idle 604 through a connection release procedure 608 or to RRC inactive 606 through a connection inactivation procedure 610. [0142] In RRC idle 604, an RRC context may not be established for the UE. In RRC idle 604, the UE may not have an RRC connection with the base station. While in RRC idle 604, the UE may be in a sleep state for the majority of the time (e.g., to conserve battery power). The UE may wake up periodically (e.g., once in every discontinuous reception cycle) to monitor for paging messages from the RAN. Mobility of the UE may be managed by the UE through a procedure known as cell reselection. The RRC state may transition from RRC idle 604 to RRC connected 602 through a connection establishment procedure 612, which may involve a random access procedure as discussed in greater detail below.

[0143] In RRC inactive 606, the RRC context previously established is maintained in the UE and the base station. This allows for a fast transition to RRC connected 602 with reduced signaling overhead as compared to the transition from RRC idle 604 to RRC connected 602. While in RRC inactive 606, the UE may be in a sleep state and mobility of the UE may be managed by the UE through cell reselection. The RRC state may transition from RRC inactive 606 to RRC connected 602 through a connection resume procedure 614 or to RRC idle 604 though a connection release procedure 616 that may be the same as or similar to connection release procedure 608. [0144] An RRC state may be associated with a mobility management mechanism. In RRC idle 604 and RRC inactive 606, mobility is managed by the UE through cell reselection. The purpose of mobility management in RRC idle 604 and RRC inactive 606 is to allow the network to be able to notify the UE of an event via a paging message without having to broadcast the paging message over the entire mobile communications network. The mobility management mechanism used in RRC idle 604 and RRC inactive 606 may allow the network to track the UE on a cell-group level so that the paging message may be broadcast over the cells of the cell group that the UE currently resides within instead of the entire mobile communication network. The mobility management mechanisms for RRC idle 604 and RRC inactive 606 track the UE on a cell-group level. They may do so using different granularities of grouping. For example, there may be three levels of cell-grouping granularity: individual cells; cells within a RAN area identified by a RAN area identifier (RAI); and cells within a group of RAN areas, referred to as a tracking area and identified by a tracking area identifier (TAI).

[0145] Tracking areas may be used to track the UE at the CN level. The CN (e.g., the CN 102 or the 5G-CN 152) may provide the UE with a list of TAIs associated with a UE registration area. If the UE moves, through cell reselection, to a cell associated with a TAI not included in the list of TAIs associated with the UE registration area, the UE may perform a registration update with the CN to allow the CN to update the UE’s location and provide the UE with a new the UE registration area.

[0146] RAN areas may be used to track the UE at the RAN level. For a UE in RRC inactive 606 state, the UE may be assigned a RAN notification area. A RAN notification area may comprise one or more cell identities, a list of RAIs, or a list of TAIs. In an example, a base station may belong to one or more RAN notification areas. In an example, a cell may belong to one or more RAN notification areas. If the UE moves, through cell reselection, to a cell not included in the RAN notification area assigned to the UE, the UE may perform a notification area update with the RAN to update the UE’s RAN notification area.

[0147] A base station storing an RRC context for a UE or a last serving base station of the UE may be referred to as an anchor base station. An anchor base station may maintain an RRC context for the UE at least during a period of time that the UE stays in a RAN notification area of the anchor base station and/or during a period of time that the UE stays in RRC inactive 606.

[0148] A gNB, such as gNBs 160 in FIG. 1 B, may be split into two parts: a central unit (gNB-CU), and one or more distributed units (gNB-DU). A gNB-CU may be coupled to one or more gNB-DUs using an F1 interface. The gNB-CU may comprise the RRC, the PDCP, and the SDAP. A gNB-DU may comprise the RLC, the MAC, and the PHY.

[0149] In NR, the physical signals and physical channels (discussed with respect to FIG. 5A and FIG. 5B) may be mapped onto orthogonal frequency divisional multiplexing (OFDM) symbols. OFDM is a multicarrier communication scheme that transmits data over F orthogonal subcarriers (or tones). Before transmission, the data may be mapped to a series of complex symbols (e.g., M-quadrature amplitude modulation (M-QAM) or M-phase shift keying (M-PSK) symbols), referred to as source symbols, and divided into F parallel symbol streams. The F parallel symbol streams may be treated as though they are in the frequency domain and used as inputs to an Inverse Fast Fourier Transform (IFFT) block that transforms them into the time domain. The IFFT block may take in F source symbols at a time, one from each of the F parallel symbol streams, and use each source symbol to modulate the amplitude and phase of one of F sinusoidal basis functions that correspond to the F orthogonal subcarriers. The output of the IFFT block may be F time-domain samples that represent the summation of the F orthogonal subcarriers. The F time-domain samples may form a single OFDM symbol. After some processing (e.g. , addition of a cyclic prefix) and up-conversion, an OFDM symbol provided by the IFFT block may be transmitted over the air interface on a carrier frequency. The F parallel symbol streams may be mixed using an FFT block before being processed by the IFFT block. This operation produces Discrete Fourier Transform (DFT)-precoded OFDM symbols and may be used by UEs in the uplink to reduce the peak to average power ratio (PAPR). Inverse processing may be performed on the OFDM symbol at a receiver using an FFT block to recover the data mapped to the source symbols.

[0150] FIG. 7 illustrates an example configuration of an NR frame into which OFDM symbols are grouped. An NR frame may be identified by a system frame number (SFN). The SFN may repeat with a period of 1024 frames. As illustrated, one NR frame may be 10 milliseconds (ms) in duration and may include 10 subframes that are 1 ms in duration. A subframe may be divided into slots that include, for example, 14 OFDM symbols per slot.

[0151] The duration of a slot may depend on the numerology used for the OFDM symbols of the slot. In NR, a flexible numerology is supported to accommodate different cell deployments (e.g., cells with carrier frequencies below 1 GHz up to cells with carrier frequencies in the mm-wave range). A numerology may be defined in terms of subcarrier spacing and cyclic prefix duration. For a numerology in NR, subcarrier spacings may be scaled up by powers of two from a baseline subcarrier spacing of 15 kHz, and cyclic prefix durations may be scaled down by powers of two from a baseline cyclic prefix duration of 4.7 ps. For example, NR defines numerologies with the following subcarrier spacing/cyclic prefix duration combinations: 15 kHz/4.7 ps; 30 kHz/2.3 ps; 60 kHz/1.2 ps; 120 kHz/0.59 ps; and 240 kHz/0.29 ps.

[0152] A slot may have a fixed number of OFDM symbols (e.g., 14 OFDM symbols). A numerology with a higher subcarrier spacing has a shorter slot duration and, correspondingly, more slots per subframe. FIG. 7 illustrates this numerology-dependent slot duration and slots-per-subframe transmission structure (the numerology with a subcarrier spacing of 240 kHz is not shown in FIG. 7 for ease of illustration). A subframe in NR may be used as a numerologyindependent time reference, while a slot may be used as the unit upon which uplink and downlink transmissions are scheduled. To support low latency, scheduling in NR may be decoupled from the slot duration and start at any OFDM symbol and last for as many symbols as needed for a transmission. These partial slot transmissions may be referred to as mini-slot or subslot transmissions.

[0153] FIG. 8 illustrates an example configuration of a slot in the time and frequency domain for an NR carrier. The slot includes resource elements (REs) and resource blocks (RBs). An RE is the smallest physical resource in NR. An RE spans one OFDM symbol in the time domain by one subcarrier in the frequency domain as shown in FIG. 8. An RB spans twelve consecutive REs in the frequency domain as shown in FIG. 8. An NR carrier may be limited to a width of 275 RBs or 275x12 = 3300 subcarriers. Such a limitation, if used, may limit the NR carrier to 50, 100, 200, and 400 MHz for subcarrier spacings of 15, 30, 60, and 120 kHz, respectively, where the 400 MHz bandwidth may be set based on a 400 MHz per carrier bandwidth limit.

[0154] FIG. 8 illustrates a single numerology being used across the entire bandwidth of the NR carrier. In other example configurations, multiple numerologies may be supported on the same carrier.

[0155] NR may support wide carrier bandwidths (e.g., up to 400 MHz for a subcarrier spacing of 120 kHz). Not all UEs may be able to receive the full carrier bandwidth (e.g., due to hardware limitations). Also, receiving the full carrier bandwidth may be prohibitive in terms of UE power consumption. In an example, to reduce power consumption and/or for other purposes, a UE may adapt the size of the UE’s receive bandwidth based on the amount of traffic the UE is scheduled to receive. This is referred to as bandwidth adaptation.

[0156] NR defines bandwidth parts (BWPs) to support UEs not capable of receiving the full carrier bandwidth and to support bandwidth adaptation. In an example, a BMP may be defined by a subset of contiguous RBs on a carrier. A UE may be configured (e.g., via RRC layer) with one or more downlink BWPs and one or more uplink BWPs per serving cell (e.g., up to four downlink BWPs and up to four uplink BWPs per serving cell). At a given time, one or more of the configured BWPs for a serving cell may be active. These one or more BWPs may be referred to as active BWPs of the serving cell. When a serving cell is configured with a secondary uplink carrier, the serving cell may have one or more first active BWPs in the uplink carrier and one or more second active BWPs in the secondary uplink carrier.

[0157] For unpaired spectra, a downlink BWP from a set of configured downlink BWPs may be linked with an uplink BWP from a set of configured uplink BWPs if a downlink BWP index of the downlink BWP and an uplink BWP index of the uplink BWP are the same. For unpaired spectra, a UE may expect that a center frequency for a downlink BWP is the same as a center frequency for an uplink BWP.

[0158] For a downlink BWP in a set of configured downlink BWPs on a primary cell (POell), a base station may configure a UE with one or more control resource sets (CORESETs) for at least one search space. A search space is a set of locations in the time and frequency domains where the UE may find control information. The search space may be a UE-specific search space or a common search space (potentially usable by a plurality of UEs). For example, a base station may configure a UE with a common search space, on a POell or on a primary secondary cell (PSOell), in an active downlink BWP.

[0159] For an uplink BWP in a set of configured uplink BWPs, a BS may configure a UE with one or more resource sets for one or more PUCOH transmissions. A UE may receive downlink receptions (e.g., PDCOH or PDSCH) in a downlink BWP according to a configured numerology (e.g., subcarrier spacing and cyclic prefix duration) for the downlink BWP. The UE may transmit uplink transmissions (e.g., PUCOH or PUSCH) in an uplink BWP according to a configured numerology (e.g., subcarrier spacing and cyclic prefix length for the uplink BWP). [0160] One or more BWP indicator fields may be provided in Downlink Control Information (DOI). A value of a BWP indicator field may indicate which BWP in a set of configured BWPs is an active downlink BWP for one or more downlink receptions. The value of the one or more BWP indicator fields may indicate an active uplink BWP for one or more uplink transmissions.

[0161] A base station may sem i-statically configure a UE with a default downlink BWP within a set of configured downlink BWPs associated with a POell. If the base station does not provide the default downlink BWP to the UE, the default downlink BWP may be an initial active downlink BWP. The UE may determine which BWP is the initial active downlink BWP based on a CORESET configuration obtained using the PBCH.

[0162] A base station may configure a UE with a BWP inactivity timer value for a PCell. The UE may start or restart a BWP inactivity timer at any appropriate time. For example, the UE may start or restart the BWP inactivity timer (a) when the UE detects a DCI indicating an active downlink BWP other than a default downlink BWP for a paired spectra operation; or (b) when a UE detects a DCI indicating an active downlink BWP or active uplink BWP other than a default downlink BWP or uplink BWP for an unpaired spectra operation. If the UE does not detect DCI during an interval of time (e.g., 1 ms or 0.5 ms), the UE may run the BWP inactivity timer toward expiration (for example, increment from zero to the BWP inactivity timer value, or decrement from the BWP inactivity timer value to zero). When the BWP inactivity timer expires, the UE may switch from the active downlink BWP to the default downlink BWP.

[0163] In an example, a base station may semi-statically configure a UE with one or more BWPs. A UE may switch an active BWP from a first BWP to a second BWP in response to receiving a DCI indicating the second BWP as an active BWP and/or in response to an expiry of the BWP inactivity timer (e.g., if the second BWP is the default BWP). [0164] Downlink and uplink BWP switching (where BWP switching refers to switching from a currently active BWP to a not currently active BWP) may be performed independently in paired spectra. In unpaired spectra, downlink and uplink BWP switching may be performed simultaneously. Switching between configured BWPs may occur based on RRC signaling, DCI, expiration of a BWP inactivity timer, and/or an initiation of random access.

[0165] FIG. 9 illustrates an example of bandwidth adaptation using three configured BWPs for an NR carrier. A UE configured with the three BWPs may switch from one BWP to another BWP at a switching point. In the example illustrated in FIG. 9, the BWPs include: a BWP 902 with a bandwidth of 40 MHz and a subcarrier spacing of 15 kHz; a BWP 904 with a bandwidth of 10 MHz and a subcarrier spacing of 15 kHz; and a BWP 906 with a bandwidth of 20 MHz and a subcarrier spacing of 60 kHz. The BWP 902 may be an initial active BWP, and the BWP 904 may be a default BWP. The UE may switch between BWPs at switching points. In the example of FIG. 9, the UE may switch from the BWP 902 to the BWP 904 at a switching point 908. The switching at the switching point 908 may occur for any suitable reason, for example, in response to an expiry of a BWP inactivity timer (indicating switching to the default BWP) and/or in response to receiving a DCI indicating BWP 904 as the active BWP. The UE may switch at a switching point 910 from active BWP 904 to BWP 906 in response to receiving a DCI indicating BWP 906 as the active BWP. The UE may switch at a switching point 912 from active BWP 906 to BWP 904 in response to an expiry of a BWP inactivity timer and/or in response to receiving a DOI indicating BWP 904 as the active BWP. The UE may switch at a switching point 914 from active BWP 904 to BWP 902 in response to receiving a DOI indicating BWP 902 as the active BWP.

[0166] If a UE is configured for a secondary cell with a default downlink BWP in a set of configured downlink BWPs and a timer value, UE procedures for switching BWPs on a secondary cell may be the same/similar as those on a primary cell. For example, the UE may use the timer value and the default downlink BWP for the secondary cell in the same/similar manner as the UE would use these values for a primary cell.

[0167] To provide for greater data rates, two or more carriers can be aggregated and simultaneously transmitted to/from the same UE using carrier aggregation (GA). The aggregated carriers in GA may be referred to as component carriers (CCs). When GA is used, there are a number of serving cells for the UE, one for a CC. The CCs may have three configurations in the frequency domain.

[0168] FIG. 10A illustrates the three GA configurations with two CCs. In the intraband, contiguous configuration 1002, the two CCs are aggregated in the same frequency band (frequency band A) and are located directly adjacent to each other within the frequency band. In the intraband, non-contiguous configuration 1004, the two CCs are aggregated in the same frequency band (frequency band A) and are separated in the frequency band by a gap. In the interband configuration 1006, the two CCs are located in frequency bands (frequency band A and frequency band B).

[0169] In an example, up to 32 CCs may be aggregated. The aggregated CCs may have the same or different bandwidths, subcarrier spacing, and/or duplexing schemes (TDD or FDD). A serving cell for a UE using CA may have a downlink CC. For FDD, one or more uplink CCs may be optionally configured for a serving cell. The ability to aggregate more downlink carriers than uplink carriers may be useful, for example, when the UE has more data traffic in the downlink than in the uplink.

[0170] When CA is used, one of the aggregated cells for a UE may be referred to as a primary cell (PCell). The PCell may be the serving cell that the UE initially connects to at RRC connection establishment, reestablishment, and/or handover. The PCell may provide the UE with NAS mobility information and the security input. UEs may have different PCells. In the downlink, the carrier corresponding to the PCell may be referred to as the downlink primary CC (DL PCC). In the uplink, the carrier corresponding to the PCell may be referred to as the uplink primary CC (UL PCC). The other aggregated cells for the UE may be referred to as secondary cells (SCells). In an example, the SCells may be configured after the PCell is configured for the UE. For example, an SCell may be configured through an RRC Connection Reconfiguration procedure. In the downlink, the carrier corresponding to an SCell may be referred to as a downlink secondary CC (DL SCC). In the uplink, the carrier corresponding to the SCell may be referred to as the uplink secondary CC (UL SCC).

[0171] Configured SCells for a UE may be activated and deactivated based on, for example, traffic and channel conditions. Deactivation of an SCell may mean that PDCCH and PDSCH reception on the SCell is stopped and PUSCH, SRS, and CQI transmissions on the SCell are stopped. Configured SCells may be activated and deactivated using a MAC CE with respect to FIG. 4B. For example, a MAC CE may use a bitmap (e.g., one bit per SCell) to indicate which SCells (e.g., in a subset of configured SCells) for the UE are activated or deactivated. Configured SCells may be deactivated in response to an expiration of an SCell deactivation timer (e.g., one SCell deactivation timer per SCell). [0172] Downlink control information, such as scheduling assignments and scheduling grants, for a cell may be transmitted on the cell corresponding to the assignments and grants, which is known as self-scheduling. The DOI for the cell may be transmitted on another cell, which is known as cross-carrier scheduling. Uplink control information (e.g., HARQ acknowledgments and channel state feedback, such as CQI, PMI, and/or Rl) for aggregated cells may be transmitted on the PUCCH of the PCell. For a larger number of aggregated downlink CCs, the PUCCH of the PCell may become overloaded. Cells may be divided into multiple PUCCH groups.

[0173] FIG. 10B illustrates an example of how aggregated cells may be configured into one or more PUCCH groups. A PUCCH group 1010 and a PUCCH group 1050 may include one or more downlink CCs, respectively. In the example of FIG. 10B, the PUCCH group 1010 includes three downlink CCs: a PCell 1011, an SCell 1012, and an SCell 1013. The PUCCH group 1050 includes three downlink CCs in the present example: a PCell 1051, an SCell 1052, and an SCell 1053. One or more uplink CCs may be configured as a PCell 1021, an SCell 1022, and an SCell 1023. One or more other uplink CCs may be configured as a primary SCell (PSCell) 1061, an SCell 1062, and an SCell 1063. Uplink control information (UCI) related to the downlink CCs of the PUCCH group 1010, shown as UC1 1031, UC1 1032, and UC1 1033, may be transmitted in the uplink of the PCell 1021. Uplink control information (UCI) related to the downlink CCs of the PUCCH group 1050, shown as UC1 1071, UC1 1072, and UC1 1073, may be transmitted in the uplink of the PSCell 1061. In an example, if the aggregated cells depicted in FIG. 10B were not divided into the PUCCH group 1010 and the PUCCH group 1050, a single uplink PCell to transmit UCI relating to the downlink CCs, and the PCell may become overloaded. By dividing transmissions of UCI between the PCell 1021 and the PSCell 1061, overloading may be prevented.

[0174] A cell, comprising a downlink carrier and optionally an uplink carrier, may be assigned with a physical cell ID and a cell index. The physical cell ID or the cell index may identify a downlink carrier and/or an uplink carrier of the cell, for example, depending on the context in which the physical cell ID is used. A physical cell ID may be determined using a synchronization signal transmitted on a downlink component carrier. A cell index may be determined using RRC messages. In the disclosure, a physical cell ID may be referred to as a carrier ID, and a cell index may be referred to as a carrier index. For example, when the disclosure refers to a first physical cell ID for a first downlink carrier, the disclosure may mean the first physical cell ID is for a cell comprising the first downlink carrier. The same/similar concept may apply to, for example, a carrier activation. When the disclosure indicates that a first carrier is activated, the specification may mean that a cell comprising the first carrier is activated.

[0175] In GA, a multi-carrier nature of a PHY may be exposed to a MAC. In an example, a HARQ entity may operate on a serving cell. A transport block may be generated per assignment/grant per serving cell. A transport block and potential HARQ retransmissions of the transport block may be mapped to a serving cell. [0176] In the downlink, a base station may transmit (e.g., unicast, multicast, and/or broadcast) one or more Reference Signals (RSs) to a UE (e.g., PSS, SSS, CSI-RS, DMRS, and/or PT-RS, as shown in FIG. 5A). In the uplink, the UE may transmit one or more RSs to the base station (e.g., DMRS, PT-RS, and/or SRS, as shown in FIG. 5B). The PSS and the SSS may be transmitted by the base station and used by the UE to synchronize the UE to the base station. The PSS and the SSS may be provided in a synchronization signal (SS) I physical broadcast channel (PBCH) block that includes the PSS, the SSS, and the PBCH. The base station may periodically transmit a burst of SS/PBCH blocks.

[0177] FIG. 11A illustrates an example of an SS/PBCH block's structure and location. A burst of SS/PBCH blocks may include one or more SS/PBCH blocks (e.g., 4 SS/PBCH blocks, as shown in FIG. 11A). Bursts may be transmitted periodically (e.g., every 2 frames or 20 ms). A burst may be restricted to a half-frame (e.g., a first half-frame having a duration of 5 ms). It will be understood that FIG. 11A is an example, and that these parameters (number of SS/PBCH blocks per burst, periodicity of bursts, position of burst within the frame) may be configured based on, for example: a carrier frequency of a cell in which the SS/PBCH block is transmitted; a numerology or subcarrier spacing of the cell; a configuration by the network (e.g., using RRC signaling); or any other suitable factor. In an example, the UE may assume a subcarrier spacing for the SS/PBCH block based on the carrier frequency being monitored, unless the radio network configured the UE to assume a different subcarrier spacing.

[0178] The SS/PBCH block may span one or more OFDM symbols in the time domain (e.g., 4 OFDM symbols, as shown in the example of FIG. 11A) and may span one or more subcarriers in the frequency domain (e.g., 240 contiguous subcarriers). The PSS, the SSS, and the PBCH may have a common center frequency. The PSS may be transmitted first and may span, for example, 1 OFDM symbol and 127 subcarriers. The SSS may be transmitted after the PSS (e.g., two symbols later) and may span 1 OFDM symbol and 127 subcarriers. The PBCH may be transmitted after the PSS (e.g., across the next 3 OFDM symbols) and may span 240 subcarriers.

[0179] The location of the SS/PBCH block in the time and frequency domains may not be known to the UE (e.g., if the UE is searching for the cell). To find and select the cell, the UE may monitor a carrier for the PSS. For example, the UE may monitor a frequency location within the carrier. If the PSS is not found after a certain duration (e.g., 20 ms), the UE may search for the PSS at a different frequency location within the carrier, as indicated by a synchronization raster. If the PSS is found at a location in the time and frequency domains, the UE may determine, based on a known structure of the SS/PBCH block, the locations of the SSS and the PBCH, respectively. The SS/PBCH block may be a celldefining SS block (CD-SSB). In an example, a primary cell may be associated with a CD-SSB. The CD-SSB may be located on a synchronization raster. In an example, a cell selection/search and/or reselection may be based on the CD- SSB.

[0180] The SS/PBCH block may be used by the UE to determine one or more parameters of the cell. For example, the UE may determine a physical cell identifier (PCI) of the cell based on the sequences of the PSS and the SSS, respectively. The UE may determine a location of a frame boundary of the cell based on the location of the SS/PBCH block. For example, the SS/PBCH block may indicate that it has been transmitted in accordance with a transmission pattern, wherein a SS/PBCH block in the transmission pattern is a known distance from the frame boundary.

[0181] The PBCH may use a QPSK modulation and may use forward error correction (FEC). The FEC may use polar coding. One or more symbols spanned by the PBCH may carry one or more DMRSs for demodulation of the PBCH. The PBCH may include an indication of a current system frame number (SFN) of the cell and/or a SS/PBCH block timing index. These parameters may facilitate time synchronization of the UE to the base station. The PBCH may include a master information block (MIB) used to provide the UE with one or more parameters. The MIB may be used by the UE to locate remaining minimum system information (RMSI) associated with the cell. The RMSI may include a System Information Block Type 1 (SIB1). The SIB1 may contain information needed by the UE to access the cell. The UE may use one or more parameters of the MIB to monitor PDCCH, which may be used to schedule PDSCH. The PDSCH may include the SIB1. The SIB1 may be decoded using parameters provided in the MIB. The PBCH may indicate an absence of SIB1. Based on the PBCH indicating the absence of SIB1 , the UE may be pointed to a frequency. The UE may search for an SS/PBCH block at the frequency to which the UE is pointed.

[0182] The UE may assume that one or more SS/PBCH blocks transmitted with a same SS/PBCH block index are quasi co-located (GCLed) (e.g., having the same/similar Doppler spread, Doppler shift, average gain, average delay, and/or spatial Rx parameters). The UE may not assume QCL for SS/PBCH block transmissions having different SS/PBCH block indices.

[0183] SS/PBCH blocks (e.g., those within a half-frame) may be transmitted in spatial directions (e.g., using different beams that span a coverage area of the cell). In an example, a first SS/PBCH block may be transmitted in a first spatial direction using a first beam, and a second SS/PBCH block may be transmitted in a second spatial direction using a second beam.

[0184] In an example, within a frequency span of a carrier, a base station may transmit a plurality of SS/PBCH blocks. In an example, a first PCI of a first SS/PBCH block of the plurality of SS/PBCH blocks may be different from a second PCI of a second SS/PBCH block of the plurality of SS/PBCH blocks. The PCIs of SS/PBCH blocks transmitted in different frequency locations may be different or the same.

[0185] The CSI-RS may be transmitted by the base station and used by the UE to acquire channel state information (CSI). The base station may configure the UE with one or more CSI-RSs for channel estimation or any other suitable purpose. The base station may configure a UE with one or more of the same/similar CSI-RSs. The UE may measure the one or more CSI-RSs. The UE may estimate a downlink channel state and/or generate a CSI report based on the measuring of the one or more downlink CSI-RSs. The UE may provide the CSI report to the base station. The base station may use feedback provided by the UE (e.g., the estimated downlink channel state) to perform link adaptation. [0186] The base station may semi-statically configure the UE with one or more CSI-RS resource sets. A CSI-RS resource may be associated with a location in the time and frequency domains and a periodicity. The base station may selectively activate and/or deactivate a CSI-RS resource. The base station may indicate to the UE that a CSI-RS resource in the CSI-RS resource set is activated and/or deactivated.

[0187] The base station may configure the UE to report CSI measurements. The base station may configure the UE to provide CSI reports periodically, aperiodically, or semi-persistently. For periodic CSI reporting, the UE may be configured with a timing and/or periodicity of a plurality of CSI reports. For aperiodic CSI reporting, the base station may request a CSI report. For example, the base station may command the UE to measure a configured CSI-RS resource and provide a CSI report relating to the measurements. For semi-persistent CSI reporting, the base station may configure the UE to transmit periodically, and selectively activate or deactivate the periodic reporting. The base station may configure the UE with a CSI-RS resource set and CSI reports using RRC signaling.

[0188] The CSI-RS configuration may comprise one or more parameters indicating, for example, up to 32 antenna ports. The UE may be configured to employ the same OFDM symbols for a downlink CSI-RS and a control resource set (CORESET) when the downlink CSI-RS and CORESET are spatially QCLed and resource elements associated with the downlink CSI-RS are outside of the physical resource blocks (PRBs) configured for the CORESET. The UE may be configured to employ the same OFDM symbols for downlink CSI-RS and SS/PBCH blocks when the downlink CSI-RS and SS/PBCH blocks are spatially QCLed and resource elements associated with the downlink CSI-RS are outside of PRBs configured for the SS/PBCH blocks.

[0189] Downlink DMRSs may be transmitted by a base station and used by a UE for channel estimation. For example, the downlink DMRS may be used for coherent demodulation of one or more downlink physical channels (e.g., PDSCH). An NR network may support one or more variable and/or configurable DMRS patterns for data demodulation. At least one downlink DMRS configuration may support a front-loaded DMRS pattern. A front-loaded DMRS may be mapped over one or more OFDM symbols (e.g., one or two adjacent OFDM symbols). A base station may semi- statically configure the UE with a number (e.g. a maximum number) of front-loaded DMRS symbols for PDSCH. A DMRS configuration may support one or more DMRS ports. For example, for single user-MIMO, a DMRS configuration may support up to eight orthogonal downlink DMRS ports per UE. For multiuser-MI MO, a DMRS configuration may support up to 4 orthogonal downlink DMRS ports per UE. A radio network may support (e.g., at least for CP-OFDM) a common DMRS structure for downlink and uplink, wherein a DMRS location, a DMRS pattern, and/or a scrambling sequence may be the same or different. The base station may transmit a downlink DMRS and a corresponding PDSCH using the same precoding matrix. The UE may use the one or more downlink DMRSs for coherent demodulation/channel estimation of the PDSCH.

[0190] In an example, a transmitter (e.g., a base station) may use a precoder matrices for a part of a transmission bandwidth. For example, the transmitter may use a first precoder matrix for a first bandwidth and a second precoder matrix for a second bandwidth. The first precoder matrix and the second precoder matrix may be different based on the first bandwidth being different from the second bandwidth. The UE may assume that a same precoding matrix is used across a set of PRBs. The set of PRBs may be denoted as a precoding resource block group (PRG). [0191] A PDSCH may comprise one or more layers. The UE may assume that at least one symbol with DMRS is present on a layer of the one or more layers of the PDSCH. A higher layer may configure up to 3 DMRSs for the PDSCH.

[0192] Downlink PT-RS may be transmitted by a base station and used by a UE for phase-noise compensation. Whether a downlink PT-RS is present or not may depend on an RRC configuration. The presence and/or pattern of the downlink PT-RS may be configured on a UE-specific basis using a combination of RRC signaling and/or an association with one or more parameters employed for other purposes (e.g., modulation and coding scheme (MCS)), which may be indicated by DCI. When configured, a dynamic presence of a downlink PT-RS may be associated with one or more DCI parameters comprising at least MCS. An NR network may support a plurality of PT-RS densities defined in the time and/or frequency domains. When present, a frequency domain density may be associated with at least one configuration of a scheduled bandwidth. The UE may assume a same precoding for a DMRS port and a PT-RS port. A number of PT-RS ports may be fewer than a number of DMRS ports in a scheduled resource. Downlink PT-RS may be confined in the scheduled time/frequency duration for the UE. Downlink PT-RS may be transmitted on symbols to facilitate phase tracking at the receiver.

[0193] The UE may transmit an uplink DMRS to a base station for channel estimation. For example, the base station may use the uplink DMRS for coherent demodulation of one or more uplink physical channels. For example, the UE may transmit an uplink DMRS with a PUSCH and/or a PUCCH. The uplink DM-RS may span a range of frequencies that is similar to a range of frequencies associated with the corresponding physical channel. The base station may configure the UE with one or more uplink DMRS configurations. At least one DMRS configuration may support a front- loaded DMRS pattern. The front-loaded DMRS may be mapped over one or more OFDM symbols (e.g., one or two adjacent OFDM symbols). One or more uplink DMRSs may be configured to transmit at one or more symbols of a PUSCH and/or a PUCCH. The base station may semi-statically configure the UE with a number (e.g. maximum number) of front-loaded DMRS symbols for the PUSCH and/or the PUCCH, which the UE may use to schedule a single-symbol DMRS and/or a double-symbol DMRS. An NR network may support (e.g., for cyclic prefix orthogonal frequency division multiplexing (CP-OFDM)) a common DMRS structure for downlink and uplink, wherein a DMRS location, a DMRS pattern, and/or a scrambling sequence for the DMRS may be the same or different.

[0194] A PUSCH may comprise one or more layers, and the UE may transmit at least one symbol with DMRS present on a layer of the one or more layers of the PUSCH. In an example, a higher layer may configure up to three DMRSs for the PUSCH.

[0195] Uplink PT-RS (which may be used by a base station for phase tracking and/or phase-noise compensation) may or may not be present depending on an RRC configuration of the UE. The presence and/or pattern of uplink PT- RS may be configured on a UE-specific basis by a combination of RRC signaling and/or one or more parameters employed for other purposes (e.g., Modulation and Coding Scheme (MCS)), which may be indicated by DCI. When configured, a dynamic presence of uplink PT-RS may be associated with one or more DCI parameters comprising at least MOS. A radio network may support a plurality of uplink PT-RS densities defined in time/frequency domain. When present, a frequency domain density may be associated with at least one configuration of a scheduled bandwidth. The UE may assume a same precoding for a DMRS port and a PT-RS port. A number of PT-RS ports may be fewer than a number of DMRS ports in a scheduled resource. For example, uplink PT-RS may be confined in the scheduled time/frequency duration for the UE.

[0196] SRS may be transmitted by a UE to a base station for channel state estimation to support uplink channel dependent scheduling and/or link adaptation. SRS transmitted by the UE may allow a base station to estimate an uplink channel state at one or more frequencies. A scheduler at the base station may employ the estimated uplink channel state to assign one or more resource blocks for an uplink PUSCH transmission from the UE. The base station may semi-statically configure the UE with one or more SRS resource sets. For an SRS resource set, the base station may configure the UE with one or more SRS resources. An SRS resource set applicability may be configured by a higher layer (e.g., RRC) parameter. For example, when a higher layer parameter indicates beam management, an SRS resource in an SRS resource set of the one or more SRS resource sets (e.g., with the same/similar time domain behavior, periodic, aperiodic, and/or the like) may be transmitted at a time instant (e.g., simultaneously). The UE may transmit one or more SRS resources in SRS resource sets. An NR network may support aperiodic, periodic and/or semi-persistent SRS transmissions. The UE may transmit SRS resources based on one or more trigger types, wherein the one or more trigger types may comprise higher layer signaling (e.g., RRC) and/or one or more DOI formats. In an example, at least one DOI format may be employed for the UE to select at least one of one or more configured SRS resource sets. An SRS trigger type 0 may refer to an SRS triggered based on a higher layer signaling. An SRS trigger type 1 may refer to an SRS triggered based on one or more DOI formats. In an example, when PUSCH and SRS are transmitted in a same slot, the UE may be configured to transmit SRS after a transmission of a PUSCH and a corresponding uplink DMRS.

[0197] The base station may semi-statically configure the UE with one or more SRS configuration parameters indicating at least one of following: a SRS resource configuration identifier; a number of SRS ports; time domain behavior of an SRS resource configuration (e.g., an indication of periodic, semi-persistent, or aperiodic SRS); slot, minislot, and/or subframe level periodicity; offset for a periodic and/or an aperiodic SRS resource; a number of OFDM symbols in an SRS resource; a starting OFDM symbol of an SRS resource; an SRS bandwidth; a frequency hopping bandwidth; a cyclic shift; and/or an SRS sequence ID.

[0198] An antenna port is defined such that the channel over which a symbol on the antenna port is conveyed can be inferred from the channel over which another symbol on the same antenna port is conveyed. If a first symbol and a second symbol are transmitted on the same antenna port, the receiver may infer the channel (e.g., fading gain, multipath delay, and/or the like) for conveying the second symbol on the antenna port, from the channel for conveying the first symbol on the antenna port. A first antenna port and a second antenna port may be referred to as quasi colocated (QCLed) if one or more large-scale properties of the channel over which a first symbol on the first antenna port is conveyed may be inferred from the channel over which a second symbol on a second antenna port is conveyed. The one or more large-scale properties may comprise at least one of: a delay spread; a Doppler spread; a Doppler shift; an average gain; an average delay; and/or spatial Receiving (Rx) parameters.

[0199] Channels that use beamforming require beam management. Beam management may comprise beam measurement, beam selection, and beam indication. A beam may be associated with one or more reference signals. For example, a beam may be identified by one or more beamformed reference signals. The UE may perform downlink beam measurement based on downlink reference signals (e.g., a channel state information reference signal (CSI-RS)) and generate a beam measurement report. The UE may perform the downlink beam measurement procedure after an RRC connection is set up with a base station.

[0200] FIG. 11B illustrates an example of channel state information reference signals (CSI-RSs) that are mapped in the time and frequency domains. A square shown in FIG. 11 B may span a resource block (RB) within a bandwidth of a cell. A base station may transmit one or more RRC messages comprising CSI-RS resource configuration parameters indicating one or more CSI-RSs. One or more of the following parameters may be configured by higher layer signaling (e.g., RRC and/or MAC signaling) for a CSI-RS resource configuration: a CSI-RS resource configuration identity, a number of CSI-RS ports, a CSI-RS configuration (e.g., symbol and resource element (RE) locations in a subframe), a CSI-RS subframe configuration (e.g., subframe location, offset, and periodicity in a radio frame), a CSI-RS power parameter, a CSI-RS sequence parameter, a code division multiplexing (CDM) type parameter, a frequency density, a transmission comb, quasi co-location (QCL) parameters (e.g., QCL-scramblingidentity, crs-portscount, mbsfn- subframeconfiglist, csi-rs-configZPid, qcl-csi-rs-configNZPid), and/or other radio resource parameters.

[0201] The three beams illustrated in FIG. 11 B may be configured for a UE in a UE-specific configuration. Three beams are illustrated in FIG. 11 B (beam #1 , beam #2, and beam #3), more or fewer beams may be configured. Beam #1 may be allocated with CSI-RS 1101 that may be transmitted in one or more subcarriers in an RB of a first symbol. Beam #2 may be allocated with CSI-RS 1102 that may be transmitted in one or more subcarriers in an RB of a second symbol. Beam #3 may be allocated with CSI-RS 1103 that may be transmitted in one or more subcarriers in an RB of a third symbol. By using frequency division multiplexing (FDM), a base station may use other subcarriers in a same RB (for example, those that are not used to transmit CSI-RS 1101) to transmit another CSI-RS associated with a beam for another UE. By using time domain multiplexing (TDM), beams used for the UE may be configured such that beams for the UE use symbols from beams of other UEs.

[0202] CSI-RSs such as those illustrated in FIG. 11 B (e.g., CSI-RS 1101, 1102, 1103) may be transmitted by the base station and used by the UE for one or more measurements. For example, the UE may measure a reference signal received power (RSRP) of configured CSI-RS resources. The base station may configure the UE with a reporting configuration and the UE may report the RSRP measurements to a network (for example, via one or more base stations) based on the reporting configuration. In an example, the base station may determine, based on the reported measurement results, one or more transmission configuration indication (TCI) states comprising a number of reference signals. In an example, the base station may indicate one or more TCI states to the UE (e.g., via RRC signaling, a MAC CE, and/or a DCI). The UE may receive a downlink transmission with a receive (Rx) beam determined based on the one or more TCI states. In an example, the UE may or may not have a capability of beam correspondence. If the UE has the capability of beam correspondence, the UE may determine a spatial domain filter of a transmit (Tx) beam based on a spatial domain filter of the corresponding Rx beam. If the UE does not have the capability of beam correspondence, the UE may perform an uplink beam selection procedure to determine the spatial domain filter of the Tx beam. The UE may perform the uplink beam selection procedure based on one or more sounding reference signal (SRS) resources configured to the UE by the base station. The base station may select and indicate uplink beams for the UE based on measurements of the one or more SRS resources transmitted by the UE.

[0203] In a beam management procedure, a UE may assess (e.g., measure) a channel quality of one or more beam pair links, a beam pair link comprising a transmitting beam transmitted by a base station and a receiving beam received by the UE. Based on the assessment, the UE may transmit a beam measurement report indicating one or more beam pair quality parameters comprising, e.g., one or more beam identifications (e.g., a beam index, a reference signal index, or the like), RSRP, a precoding matrix indicator (PMI), a channel quality indicator (CQI), and/or a rank indicator (Rl). [0204] FIG. 12A illustrates examples of three downlink beam management procedures: P1, P2, and P3. Procedure P1 may enable a UE measurement on transmit (Tx) beams of a transmission reception point (TRP) (or multiple TRPs), e.g., to support a selection of one or more base station Tx beams and/or UE Rx beams (shown as ovals in the top row and bottom row, respectively, of P1). Beamforming at a TRP may comprise a Tx beam sweep for a set of beams (shown, in the top rows of P1 and P2, as ovals rotated in a counterclockwise direction indicated by the dashed arrow). Beamforming at a UE may comprise an Rx beam sweep for a set of beams (shown, in the bottom rows of P1 and P3, as ovals rotated in a clockwise direction indicated by the dashed arrow). Procedure P2 may be used to enable a UE measurement on Tx beams of a TRP (shown, in the top row of P2, as ovals rotated in a counterclockwise direction indicated by the dashed arrow). The UE and/or the base station may perform procedure P2 using a smaller set of beams than is used in procedure P1 , or using narrower beams than the beams used in procedure P1. This may be referred to as beam refinement. The UE may perform procedure P3 for Rx beam determination by using the same Tx beam at the base station and sweeping an Rx beam at the UE.

[0205] FIG. 12B illustrates examples of three uplink beam management procedures: U1, U2, and U3. Procedure U1 may be used to enable a base station to perform a measurement on Tx beams of a UE, e.g., to support a selection of one or more UE Tx beams and/or base station Rx beams (shown as ovals in the top row and bottom row, respectively, of U1). Beamforming at the UE may include, e.g., a Tx beam sweep from a set of beams (shown in the bottom rows of U1 and U3 as ovals rotated in a clockwise direction indicated by the dashed arrow). Beamforming at the base station may include, e.g., an Rx beam sweep from a set of beams (shown, in the top rows of U1 and U2, as ovals rotated in a counterclockwise direction indicated by the dashed arrow). Procedure U2 may be used to enable the base station to adjust its Rx beam when the UE uses a fixed Tx beam. The UE and/or the base station may perform procedure U2 using a smaller set of beams than is used in procedure P1, or using narrower beams than the beams used in procedure P1. This may be referred to as beam refinement The UE may perform procedure U3 to adjust its Tx beam when the base station uses a fixed Rx beam.

[0206] A UE may initiate a beam failure recovery (BFR) procedure based on detecting a beam failure. The UE may transmit a BFR request (e.g., a preamble, a UCI, an SR, a MAC CE, and/or the like) based on the initiating of the BFR procedure. The UE may detect the beam failure based on a determination that a quality of beam pair link(s) of an associated control channel is unsatisfactory (e.g., having an error rate higher than an error rate threshold, a received signal power lower than a received signal power threshold, an expiration of a timer, and/or the like).

[0207] The UE may measure a quality of a beam pair link using one or more reference signals (RSs) comprising one or more SS/PBCH blocks, one or more CSI-RS resources, and/or one or more demodulation reference signals (DMRSs). A quality of the beam pair link may be based on one or more of a block error rate (BLER), an RSRP value, a signal to interference plus noise ratio (SINR) value, a reference signal received quality (RSRQ) value, and/or a CSI value measured on RS resources. The base station may indicate that an RS resource is quasi co-located (QCLed) with one or more DM-RSs of a channel (e.g., a control channel, a shared data channel, and/or the like). The RS resource and the one or more DMRSs of the channel may be QCLed when the channel characteristics (e.g., Doppler shift, Doppler spread, average delay, delay spread, spatial Rx parameter, fading, and/or the like) from a transmission via the RS resource to the UE are similar or the same as the channel characteristics from a transmission via the channel to the UE.

[0208] A network (e.g., a gNB and/or an ng-eNB of a network) and/or the UE may initiate a random access procedure. A UE in an RRC_I DLE state and/or an RRC_I NACTI VE state may initiate the random access procedure to request a connection setup to a network. The UE may initiate the random access procedure from an RRC_CONNECTED state. The UE may initiate the random access procedure to request uplink resources (e.g., for uplink transmission of an SR when there is no PUCCH resource available) and/or acquire uplink timing (e.g., when uplink synchronization status is non-synchronized). The UE may initiate the random access procedure to request one or more system information blocks (SIBs) (e.g., other system information such as SIB2, SIB3, and/or the like). The UE may initiate the random access procedure for a beam failure recovery request. A network may initiate a random access procedure for a handover and/or for establishing time alignment for an SCell addition.

[0209] FIG. 13A illustrates a four-step contention-based random access procedure. Prior to initiation of the procedure, a base station may transmit a configuration message 1310 to the UE. The procedure illustrated in FIG. 13A comprises transmission of four messages: a Msg 1 1311, a Msg 2 1312, a Msg 31313, and a Msg 41314. The Msg 1 1311 may include and/or be referred to as a preamble (ora random access preamble). The Msg 2 1312 may include and/or be referred to as a random access response (RAR).

[0210] The configuration message 1310 may be transmitted, for example, using one or more RRC messages. The one or more RRC messages may indicate one or more random access channel (RACH) parameters to the UE. The one or more RACH parameters may comprise at least one of following: general parameters for one or more random access procedures (e.g., RACH-configGeneral); cell-specific parameters (e.g. , RACH-ConfigCommon'); and/or dedicated parameters (e.g., RACH-configDedicated). The base station may broadcast or multicast the one or more RRC messages to one or more UEs. The one or more RRC messages may be UE-specific (e.g., dedicated RRC messages transmitted to a UE in an RRC_CONNECTED state and/or in an RRCJNACTIVE state). The UE may determine, based on the one or more RACH parameters, a time-frequency resource and/or an uplink transmit power for transmission of the Msg 1 1311 and/or the Msg 31313. Based on the one or more RACH parameters, the UE may determine a reception timing and a downlink channel for receiving the Msg 2 1312 and the Msg 41314.

[0211] The one or more RACH parameters provided in the configuration message 1310 may indicate one or more Physical RACH (PRACH) occasions available for transmission of the Msg 1 1311. The one or more PRACH occasions may be predefined. The one or more RACH parameters may indicate one or more available sets of one or more PRACH occasions (e.g., prach-Configlndex). The one or more RACH parameters may indicate an association between (a) one or more PRACH occasions and (b) one or more reference signals. The one or more RACH parameters may indicate an association between (a) one or more preambles and (b) one or more reference signals. The one or more reference signals may be SS/PBCH blocks and/or CSI-RSs. For example, the one or more RACH parameters may indicate a number of SS/PBCH blocks mapped to a PRACH occasion and/or a number of preambles mapped to a SS/PBCH blocks.

[0212] The one or more RACH parameters provided in the configuration message 1310 may be used to determine an uplink transmit power of Msg 1 1311 and/or Msg 3 1313. For example, the one or more RACH parameters may indicate a reference power for a preamble transmission (e.g., a received target power and/or an initial power of the preamble transmission). There may be one or more power offsets indicated by the one or more RACH parameters. For example, the one or more RACH parameters may indicate: a power ramping step; a power offset between SSB and CSI-RS; a power offset between transmissions of the Msg 1 1311 and the Msg 3 1313; and/or a power offset value between preamble groups. The one or more RACH parameters may indicate one or more thresholds based on which the UE may determine at least one reference signal (e.g., an SSB and/or CSI-RS) and/or an uplink carrier (e.g., a normal uplink (NUL) carrier and/or a supplemental uplink (SUL) carrier).

[0213] The Msg 1 1311 may include one or more preamble transmissions (e.g., a preamble transmission and one or more preamble retransmissions). An RRC message may be used to configure one or more preamble groups (e.g., group A and/or group B). A preamble group may comprise one or more preambles. The UE may determine the preamble group based on a pathloss measurement and/or a size of the Msg 3 1313. The UE may measure an RSRP of one or more reference signals (e.g., SSBs and/or CSI-RSs) and determine at least one reference signal having an RSRP above an RSRP threshold (e.g., rs/p-ThresholdSSB and/or rs/p-ThresholdCSI-RS). The UE may select at least one preamble associated with the one or more reference signals and/or a selected preamble group, for example, if the association between the one or more preambles and the at least one reference signal is configured by an RRC message.

[0214] The UE may determine the preamble based on the one or more RACH parameters provided in the configuration message 1310. For example, the UE may determine the preamble based on a pathloss measurement, an RSRP measurement, and/or a size of the Msg 3 1313. As another example, the one or more RACH parameters may indicate: a preamble format; a maximum number of preamble transmissions; and/or one or more thresholds for determining one or more preamble groups (e.g., group A and group B). A base station may use the one or more RACH parameters to configure the UE with an association between one or more preambles and one or more reference signals (e.g., SSBs and/or CSI-RSs). If the association is configured, the UE may determine the preamble to include in Msg 1 1311 based on the association. The Msg 1 1311 may be transmitted to the base station via one or more PRACH occasions. The UE may use one or more reference signals (e.g., SSBs and/or CSI-RSs) for selection of the preamble and for determining of the PRACH occasion. One or more RACH parameters (e.g., ra-ssb-Occasi nMsklndex and/or ra-OccasionList) may indicate an association between the PRACH occasions and the one or more reference signals. [0215] The UE may perform a preamble retransmission if no response is received following a preamble transmission. The UE may increase an uplink transmit power for the preamble retransmission. The UE may select an initial preamble transmit power based on a pathloss measurement and/or a target received preamble power configured by the network. The UE may determine to retransmit a preamble and may ramp up the uplink transmit power. The UE may receive one or more RACH parameters (e.g., PREAMBLE_POWER_RAMP/NG_STEP) indicating a ramping step for the preamble retransmission. The ramping step may be an amount of incremental increase in uplink transmit power for a retransmission. The UE may ramp up the uplink transmit power if the UE determines a reference signal (e.g., SSB and/or CSI-RS) that is the same as a previous preamble transmission. The UE may count a number of preamble transmissions and/or retransmissions (e.g., PREAMBLE_TRANSM/SS/ON_COUNTER). The UE may determine that a random access procedure completed unsuccessfully, for example, if the number of preamble transmissions exceeds a threshold configured by the one or more RACH parameters (e.g., preambleTransMax).

[0216] The Msg 2 1312 received by the UE may include an RAR. In some scenarios, the Msg 21312 may include multiple RARs corresponding to multiple UEs. The Msg 21312 may be received after or in response to the transmitting of the Msg 1 1311. The Msg 2 1312 may be scheduled on the DL-SCH and indicated on a PDCCH using a random access RNTI (RA-RNTI). The Msg 21312 may indicate that the Msg 1 1311 was received by the base station. The Msg 2 1312 may include a time-alignment command that may be used by the UE to adjust the UE’s transmission timing, a scheduling grant for transmission of the Msg 3 1313, and/or a Temporary Cell RNTI (TC-RNTI). After transmitting a preamble, the UE may start a time window (e.g., ra-ResponseWindow) to monitor a PDCCH for the Msg 2 1312. The UE may determine when to start the time window based on a PRACH occasion that the UE uses to transmit the preamble. For example, the UE may start the time window one or more symbols after a last symbol of the preamble (e.g., at a first PDCCH occasion from an end of a preamble transmission). The one or more symbols may be determined based on a numerology. The PDCCH may be in a common search space (e.g., a Typel-PDCCH common search space) configured by an RRC message. The UE may identify the RAR based on a Radio Network Temporary Identifier (RNTI). RNTIs may be used depending on one or more events initiating the random access procedure. The UE may use random access RNTI (RA-RNTI). The RA-RNTI may be associated with PRACH occasions in which the UE transmits a preamble. For example, the UE may determine the RA-RNTI based on: an OFDM symbol index; a slot index; a frequency domain index; and/or a UL carrier indicator of the PRACH occasions. An example of RA-RNTI may be as follows:

[0217] RA-RNTI= 1 + s_id + 14 x t_id + 14 x 80 x fjd + 14 x 80 x 8 x ul_carrier_id, where s_id may be an index of a first OFDM symbol of the PRACH occasion (e.g., 0 < s_id < 14), t_id may be an index of a first slot of the PRACH occasion in a system frame (e.g., 0 < t_id < 80), f_id may be an index of the PRACH occasion in the frequency domain (e.g., 0 < f_id < 8), and ul_carrier_id may be a UL carrier used for a preamble transmission (e.g., 0 for an NUL carrier, and 1 for an SUL carrier).

[0218] The UE may transmit the Msg 3 1313 in response to a successful reception of the Msg 21312 (e.g., using resources identified in the Msg 21312). The Msg 3 1313 may be used for contention resolution in, for example, the contention-based random access procedure illustrated in FIG. 13A. In some scenarios, a plurality of UEs may transmit a same preamble to a base station and the base station may provide an RAR that corresponds to a UE. Collisions may occur if the plurality of UEs interpret the RAR as corresponding to themselves. Contention resolution (e.g., using the Msg 3 1313 and the Msg 41314) may be used to increase the likelihood that the UE does not incorrectly use an identity of another the UE. To perform contention resolution, the UE may include a device identifier in the Msg 3 1313 (e.g., a C-RNTI if assigned, a TC-RNTI included in the Msg 2 1312, and/or any other suitable identifier).

[0219] The Msg 41314 may be received after or in response to the transmitting of the Msg 3 1313. If a C-RNTI was included in the Msg 3 1313, the base station will address the UE on the PDCCH using the C-RNTI. If the UE's unique C-RNTI is detected on the PDCCH, the random access procedure is determined to be successfully completed. If a TC-RNTI is included in the Msg 31313 (e.g., if the UE is in an RRC_IDLE state or not otherwise connected to the base station), Msg 41314 will be received using a DL-SCH associated with the TC-RNTI. If a MAC PDU is successfully decoded and a MAC PDU comprises the UE contention resolution identity MAC CE that matches or otherwise corresponds with the CCCH SDU sent (e.g., transmitted) in Msg 3 1313, the UE may determine that the contention resolution is successful and/or the UE may determine that the random access procedure is successfully completed. [0220] The UE may be configured with a supplementary uplink (SUL) carrier and a normal uplink (NUL) carrier. An initial access (e.g., random access procedure) may be supported in an uplink carrier. For example, a base station may configure the UE with two separate RACH configurations: one for an SUL carrier and the other for an NUL carrier. For random access in a cell configured with an SUL carrier, the network may indicate which carrier to use (NUL or SUL). The UE may determine the SUL carrier, for example, if a measured quality of one or more reference signals is lower than a broadcast threshold. Uplink transmissions of the random access procedure (e.g., the Msg 1 1311 and/or the Msg 31313) may remain on the selected carrier. The UE may switch an uplink carrier during the random access procedure (e.g., between the Msg 1 1311 and the Msg 3 1313) in one or more cases. For example, the UE may determine and/or switch an uplink carrier for the Msg 1 1311 and/or the Msg 31313 based on a channel clear assessment (e.g., a listen- before-talk).

[0221] FIG. 13B illustrates a two-step contention-free random access procedure. Similar to the four-step contentionbased random access procedure illustrated in FIG. 13A, a base station may, prior to initiation of the procedure, transmit a configuration message 1320 to the UE. The configuration message 1320 may be analogous in some respects to the configuration message 1310. The procedure illustrated in FIG. 13B comprises transmission of two messages: a Msg 1 1321 and a Msg 21322. The Msg 1 1321 and the Msg 21322 may be analogous in some respects to the Msg 1 1311 and a Msg 21312 illustrated in FIG. 13A, respectively. As will be understood from FIGS. 13A and 13B, the contention- free random access procedure may not include messages analogous to the Msg 3 1313 and/or the Msg 41314.

[0222] The contention-free random access procedure illustrated in FIG. 13B may be initiated for a beam failure recovery, other SI request, SCell addition, and/or handover. For example, a base station may indicate or assign to the UE the preamble to be used for the Msg 1 1321. The UE may receive, from the base station via PDCCH and/or RRC, an indication of a preamble (e.g., ra-Preamblelndex).

[0223] After transmitting a preamble, the UE may start a time window (e.g., ra-ResponseWindow to monitor a PDCCH for the RAR. In the event of a beam failure recovery request, the base station may configure the UE with a separate time window and/or a separate PDCCH in a search space indicated by an RRC message (e.g., recoverySearchSpaceld). The UE may monitor for a PDCCH transmission addressed to a Cell RNTI (C-RNTI) on the search space. In the contention-free random access procedure illustrated in FIG. 13B, the UE may determine that a random access procedure successfully completes after or in response to transmission of Msg 1 1321 and reception of a corresponding Msg 2 1322. The UE may determine that a random access procedure successfully completes, for example, if a PDCCH transmission is addressed to a C-RNTI. The UE may determine that a random access procedure successfully completes, for example, if the UE receives an RAR comprising a preamble identifier corresponding to a preamble transmitted by the UE and/or the RAR comprises a MAC sub-PDU with the preamble identifier. The UE may determine the response as an indication of an acknowledgement for an SI request.

[0224] FIG. 13C illustrates another two-step random access procedure. Similar to the random access procedures illustrated in FIGS. 13A and 13B, a base station may, prior to initiation of the procedure, transmit a configuration message 1330 to the UE. The configuration message 1330 may be analogous in some respects to the configuration message 1310 and/or the configuration message 1320. The procedure illustrated in FIG. 13C comprises transmission of two messages: a Msg A 1331 and a Msg B 1332.

[0225] Msg A 1331 may be transmitted in an uplink transmission by the UE. Msg A 1331 may comprise one or more transmissions of a preamble 1341 and/or one or more transmissions of a transport block 1342. The transport block 1342 may comprise contents that are similar and/or equivalent to the contents of the Msg 3 1313 illustrated in FIG. 13A. The transport block 1342 may comprise UCI (e.g., an SR, a HARQ ACK/NACK, and/or the like). The UE may receive the Msg B 1332 after or in response to transmitting the Msg A 1331. The Msg B 1332 may comprise contents that are similar and/or equivalent to the contents of the Msg 2 1312 (e.g., an RAR) illustrated in FIGS. 13A and 13B and/or the Msg 41314 illustrated in FIG. 13A.

[0226] The UE may initiate the two-step random access procedure in FIG. 130 for licensed spectrum and/or unlicensed spectrum. The UE may determine, based on one or more factors, whether to initiate the two-step random access procedure. The one or more factors may be: a radio access technology in use (e.g., LTE, NR, and/or the like); whether the UE has valid TA or not; a cell size; the UE’s RRC state; a type of spectrum (e.g., licensed vs. unlicensed); and/or any other suitable factors.

[0227] The UE may determine, based on two-step RACH parameters included in the configuration message 1330, a radio resource and/or an uplink transmit power for the preamble 1341 and/or the transport block 1342 included in the Msg A 1331. The RACH parameters may indicate a modulation and coding schemes (MOS), a time-frequency resource, and/or a power control for the preamble 1341 and/or the transport block 1342. A time-frequency resource for transmission of the preamble 1341 (e.g., a PRACH) and a time-frequency resource for transmission of the transport block 1342 (e.g., a PUSCH) may be multiplexed using FDM, TDM, and/or CDM. The RACH parameters may enable the UE to determine a reception timing and a downlink channel for monitoring for and/or receiving Msg B 1332.

[0228] The transport block 1342 may comprise data (e.g., delay-sensitive data), an identifier of the UE, security information, and/or device information (e.g., an International Mobile Subscriber Identity (I MSI)). The base station may transmit the Msg B 1332 as a response to the Msg A 1331. The Msg B 1332 may comprise at least one of following: a preamble identifier; a timing advance command; a power control command; an uplink grant (e.g., a radio resource assignment and/or an MCS); a UE identifier for contention resolution; and/or an RNTI (e.g., a C-RNTI or a TC-RNTI). The UE may determine that the two-step random access procedure is successfully completed if: a preamble identifier in the Msg B 1332 is matched to a preamble transmitted by the UE; and/or the identifier of the UE in Msg B 1332 is matched to the identifier of the UE in the Msg A 1331 (e.g., the transport block 1342).

[0229] A UE and a base station may exchange control signaling. The control signaling may be referred to as L1/L2 control signaling and may originate from the PHY layer (e.g., layer 1) and/or the MAC layer (e.g., layer 2). The control signaling may comprise downlink control signaling transmitted from the base station to the UE and/or uplink control signaling transmitted from the UE to the base station.

[0230] The downlink control signaling may comprise: a downlink scheduling assignment; an uplink scheduling grant indicating uplink radio resources and/or a transport format; a slot format information; a preemption indication; a power control command; and/or any other suitable signaling. The UE may receive the downlink control signaling in a payload transmitted by the base station on a physical downlink control channel (PDCCH). The payload transmitted on the PDCCH may be referred to as downlink control information (DOI). In some scenarios, the PDCCH may be a group common PDCCH (GC-PDCCH) that is common to a group of UEs. [0231] A base station may attach one or more cyclic redundancy check (ORC) parity bits to a DOI in order to facilitate detection of transmission errors. When the DOI is intended for a UE (or a group of the UEs), the base station may scramble the ORC parity bits with an identifier of the UE (or an identifier of the group of the UEs). Scrambling the ORO parity bits with the identifier may comprise Modulo-2 addition (or an exclusive OR operation) of the identifier value and the ORO parity bits. The identifier may comprise a 16-bit value of a radio network temporary identifier (RNTI).

[0232] DOIs may be used for different purposes. A purpose may be indicated by the type of RNTI used to scramble the ORO parity bits. For example, a DOI having ORO parity bits scrambled with a paging RNTI (P-RNTI) may indicate paging information and/or a system information change notification. The P-RNTI may be predefined as “FFFE” in hexadecimal. A DOI having ORO parity bits scrambled with a system information RNTI (SI-RNTI) may indicate a broadcast transmission of the system information. The SI-RNTI may be predefined as “FFFF” in hexadecimal. A DOI having ORO parity bits scrambled with a random access RNTI (RA-RNTI) may indicate a random access response (RAR). A DOI having ORO parity bits scrambled with a cell RNTI (C-RNTI) may indicate a dynamically scheduled unicast transmission and/or a triggering of PDCOH-ordered random access. A DOI having ORO parity bits scrambled with a temporary cell RNTI (TC-RNTI) may indicate a contention resolution (e.g., a Msg 3 analogous to the Msg 3 1313 illustrated in FIG. 13A). Other RNTIs configured to the UE by a base station may comprise a Configured Scheduling RNTI (CS-RNTI), a Transmit Power Control-PUCOH RNTI (TPC-PUCCH-RNTI), a Transmit Power Control-PUSCH RNTI (TPC-PUSCH-RNTI), a Transmit Power Control-SRS RNTI (TPC-SRS-RNTI), an Interruption RNTI (INT-RNTI), a Slot Format Indication RNTI (SFI-RNTI), a Semi-Persistent CSI RNTI (SP-CSI-RNTI), a Modulation and Coding Scheme Cell RNTI (MCS-C-RNTI), and/or the like.

[0233] Depending on the purpose and/or content of a DCI, the base station may transmit the DCIs with one or more DCI formats. For example, DCI format 0_0 may be used for scheduling of PUSCH in a cell. DCI format 0_0 may be a fallback DCI format (e.g., with compact DCI payloads). DCI format 0_1 may be used for scheduling of PUSCH in a cell (e.g., with more DCI payloads than DCI format 0_0). DCI format 1_0 may be used for scheduling of PDSCH in a cell. DCI format 1_0 may be a fallback DCI format (e.g., with compact DCI payloads). DCI format 1_1 may be used for scheduling of PDSCH in a cell (e.g., with more DCI payloads than DCI format 1_0). DCI format 2_0 may be used for providing a slot format indication to a group of UEs. DCI format 2_1 may be used for notifying a group of UEs of a physical resource block and/or OFDM symbol where the UE may assume no transmission is intended to the UE. DCI format 2_2 may be used for transmission of a transmit power control (TPC) command for PUCCH or PUSCH. DCI format 2_3 may be used for transmission of a group of TPC commands for SRS transmissions by one or more UEs. DCI format(s) for new functions may be defined in future releases. DCI formats may have different DCI sizes, or may share the same DCI size.

[0234] After scrambling a DCI with a RNTI, the base station may process the DCI with channel coding (e.g., polar coding), rate matching, scrambling and/or GPSK modulation. A base station may map the coded and modulated DCI on resource elements used and/or configured for a PDCCH. Based on a payload size of the DCI and/or a coverage of the base station, the base station may transmit the DOI via a PDCCH occupying a number of contiguous control channel elements (CCEs). The number of the contiguous CCEs (referred to as aggregation level) may be 1 , 2, 4, 8, 16, and/or any other suitable number. A COE may comprise a number (e.g., 6) of resource-element groups (REGs). A REG may comprise a resource block in an OFDM symbol. The mapping of the coded and modulated DOI on the resource elements may be based on mapping of CCEs and REGs (e.g., CCE-to-REG mapping).

[0235] FIG. 14A illustrates an example of CORESET configurations for a bandwidth part. The base station may transmit a DOI via a PDCCH on one or more control resource sets (CORESETs). A CORESET may comprise a timefrequency resource in which the UE tries to decode a DOI using one or more search spaces. The base station may configure a CORESET in the time-frequency domain. In the example of FIG. 14A, a first CORESET 1401 and a second CORESET 1402 occur at the first symbol in a slot. The first CORESET 1401 overlaps with the second CORESET 1402 in the frequency domain. A third CORESET 1403 occurs at a third symbol in the slot. A fourth CORESET 1404 occurs at the seventh symbol in the slot. CORESETs may have a different number of resource blocks in frequency domain.

[0236] FIG. 14B illustrates an example of a CCE-to-REG mapping for DCI transmission on a CORESET and PDCCH processing. The CCE-to-REG mapping may be an interleaved mapping (e.g., for the purpose of providing frequency diversity) or a non-interleaved mapping (e.g., for the purposes of facilitating interference coordination and/or frequency- selective transmission of control channels). The base station may perform different or same CCE-to-REG mapping on different CORESETs. A CORESET may be associated with a CCE-to-REG mapping by RRC configuration. A CORESET may be configured with an antenna port quasi co-location (QCL) parameter. The antenna port QCL parameter may indicate QCL information of a demodulation reference signal (DMRS) for PDCCH reception in the CORESET.

[0237] The base station may transmit, to the UE, RRC messages comprising configuration parameters of one or more CORESETs and one or more search space sets. The configuration parameters may indicate an association between a search space set and a CORESET. A search space set may comprise a set of PDCCH candidates formed by CCEs at a given aggregation level. The configuration parameters may indicate: a number of PDCCH candidates to be monitored per aggregation level; a PDCCH monitoring periodicity and a PDCCH monitoring pattern; one or more DCI formats to be monitored by the UE; and/or whether a search space set is a common search space set or a UE- specific search space set. A set of CCEs in the common search space set may be predefined and known to the UE. A set of CCEs in the UE-specific search space set may be configured based on the UE’s identity (e.g., C-RNTI).

[0238] As shown in FIG. 14B, the UE may determine a time-frequency resource for a CORESET based on RRC messages. The UE may determine a CCE-to-REG mapping (e.g., interleaved or non-interleaved, and/or mapping parameters) for the CORESET based on configuration parameters of the CORESET. The UE may determine a number (e.g., at most 10) of search space sets configured on the CORESET based on the RRC messages. The UE may monitor a set of PDCCH candidates according to configuration parameters of a search space set. The UE may monitor a set of PDCCH candidates in one or more CORESETs for detecting one or more DCIs. Monitoring may comprise decoding one or more PDCCH candidates of the set of the PDCCH candidates according to the monitored DOI formats. Monitoring may comprise decoding a DOI content of one or more PDCCH candidates with possible (or configured) PDCCH locations, possible (or configured) PDCCH formats (e.g. , number of CCEs, number of PDCCH candidates in common search spaces, and/or number of PDCCH candidates in the UE-specific search spaces) and possible (or configured) DCI formats. The decoding may be referred to as blind decoding. The UE may determine a DCI as valid for the UE, in response to CRC checking (e.g., scrambled bits for CRC parity bits of the DCI matching a RNTI value). The UE may process information contained in the DCI (e.g., a scheduling assignment, an uplink grant, power control, a slot format indication, a downlink preemption, and/or the like).

[0239] The UE may transmit uplink control signaling (e.g., uplink control information (UCI)) to a base station. The uplink control signaling may comprise hybrid automatic repeat request (HARQ) acknowledgements for received DL- SCH transport blocks. The UE may transmit the HARQ acknowledgements after receiving a DL-SCH transport block. Uplink control signaling may comprise channel state information (CSI) indicating channel quality of a physical downlink channel. The UE may transmit the CSI to the base station. The base station, based on the received CSI, may determine transmission format parameters (e.g., comprising multi-antenna and beamforming schemes) for a downlink transmission. Uplink control signaling may comprise scheduling requests (SR). The UE may transmit an SR indicating that uplink data is available for transmission to the base station. The UE may transmit a UCI (e.g., HARQ acknowledgements (HARQ-ACK), CSI report, SR, and the like) via a physical uplink control channel (PUCCH) or a physical uplink shared channel (PUSCH). The UE may transmit the uplink control signaling via a PUCCH using one of several PUCCH formats.

[0240] There may be five PUCCH formats and the UE may determine a PUCCH format based on a size of the UCI (e.g., a number of uplink symbols of UCI transmission and a number of UCI bits). PUCCH format 0 may have a length of one or two OFDM symbols and may include two or fewer bits. The UE may transmit UCI in a PUCCH resource using PUCCH format 0 if the transmission is over one or two symbols and the number of HARQ-ACK information bits with positive or negative SR (HARQ-ACK/SR bits) is one or two. PUCCH format 1 may occupy a number between four and fourteen OFDM symbols and may include two or fewer bits. The UE may use PUCCH format 1 if the transmission is four or more symbols and the number of HARQ-ACK/SR bits is one or two. PUCCH format 2 may occupy one or two OFDM symbols and may include more than two bits. The UE may use PUCCH format 2 if the transmission is over one or two symbols and the number of UCI bits is two or more. PUCCH format 3 may occupy a number between four and fourteen OFDM symbols and may include more than two bits. The UE may use PUCCH format 3 if the transmission is four or more symbols, the number of UCI bits is two or more and PUCCH resource does not include an orthogonal cover code. PUCCH format 4 may occupy a number between four and fourteen OFDM symbols and may include more than two bits. The UE may use PUCCH format 4 if the transmission is four or more symbols, the number of UCI bits is two or more and the PUCCH resource includes an orthogonal cover code. [0241] The base station may transmit configuration parameters to the UE for a plurality of PUCCH resource sets using, for example, an RRC message. The plurality of PUCCH resource sets (e.g., up to four sets) may be configured on an uplink BWP of a cell. A PUCCH resource set may be configured with a PUCCH resource set index, a plurality of PUCCH resources with a PUCCH resource being identified by a PUCCH resource identifier (e.g., pucch-Resourceid), and/or a number (e.g. a maximum number) of UCI information bits the UE may transmit using one of the plurality of PUCCH resources in the PUCCH resource set. When configured with a plurality of PUCCH resource sets, the UE may select one of the plurality of PUCCH resource sets based on a total bit length of the UCI information bits (e.g., HARQ- ACK, SR, and/or CSI). If the total bit length of UCI information bits is two or fewer, the UE may select a first PUCCH resource set having a PUCCH resource set index equal to “0”. If the total bit length of UCI information bits is greater than two and less than or equal to a first configured value, the UE may select a second PUCCH resource set having a PUCCH resource set index equal to “1”. If the total bit length of UCI information bits is greater than the first configured value and less than or equal to a second configured value, the UE may select a third PUCCH resource set having a PUCCH resource set index equal to “2”. If the total bit length of UCI information bits is greater than the second configured value and less than or equal to a third value (e.g., 1406), the UE may select a fourth PUCCH resource set having a PUCCH resource set index equal to “3”.

[0242] After determining a PUCCH resource set from a plurality of PUCCH resource sets, the UE may determine a PUCCH resource from the PUCCH resource set for UCI (HARQ-ACK, CSI, and/or SR) transmission. The UE may determine the PUCCH resource based on a PUCCH resource indicator in a DCI (e.g., with a DCI format 1_0 or DCI for 1_1) received on a PDCCH. A three-bit PUCCH resource indicator in the DCI may indicate one of eight PUCCH resources in the PUCCH resource set. Based on the PUCCH resource indicator, the UE may transmit the UCI (HARQ- ACK, CSI and/or SR) using a PUCCH resource indicated by the PUCCH resource indicator in the DCI.

[0243] FIG. 15 illustrates an example of a wireless device 1502 in communication with a base station 1504 in accordance with embodiments of the present disclosure. The wireless device 1502 and base station 1504 may be part of a mobile communication network, such as the mobile communication network 100 illustrated in FIG. 1A, the mobile communication network 150 illustrated in FIG. 1 B, or any other communication network. Only one wireless device 1502 and one base station 1504 are illustrated in FIG. 15, but it will be understood that a mobile communication network may include more than one UE and/or more than one base station, with the same or similar configuration as those shown in FIG. 15.

[0244] The base station 1504 may connect the wireless device 1502 to a core network (not shown) through radio communications over the air interface (or radio interface) 1506. The communication direction from the base station 1504 to the wireless device 1502 over the air interface 1506 is known as the downlink, and the communication direction from the wireless device 1502 to the base station 1504 over the air interface is known as the uplink. Downlink transmissions may be separated from uplink transmissions using FDD, TDD, and/or some combination of the two duplexing techniques. [0245] In the downlink, data to be sent to the wireless device 1502 from the base station 1504 may be provided to the processing system 1508 of the base station 1504. The data may be provided to the processing system 1508 by, for example, a core network. In the uplink, data to be sent to the base station 1504 from the wireless device 1502 may be provided to the processing system 1518 of the wireless device 1502. The processing system 1508 and the processing system 1518 may implement layer 3 and layer 2 OSI functionality to process the data for transmission. Layer 2 may include an SDAP layer, a PDCP layer, an RLC layer, and a MAC layer, for example, with respect to FIG. 2A, FIG. 2B, FIG. 3, and FIG. 4A. Layer 3 may include an RRC layer as with respect to FIG. 2B.

[0246] After being processed by processing system 1508, the data to be sent to the wireless device 1502 may be provided to a transmission processing system 1510 of base station 1504. Similarly, after being processed by the processing system 1518, the data to be sent to base station 1504 may be provided to a transmission processing system 1520 of the wireless device 1502. The transmission processing system 1510 and the transmission processing system 1520 may implement layer 1 OSI functionality. Layer 1 may include a PHY layer with respect to FIG. 2A, FIG. 2B, FIG. 3, and FIG. 4A. For transmit processing, the PHY layer may perform, for example, forward error correction coding of transport channels, interleaving, rate matching, mapping of transport channels to physical channels, modulation of physical channel, multiple-input multiple-output (MIMO) or multi-antenna processing, and/or the like. [0247] At the base station 1504, a reception processing system 1512 may receive the uplink transmission from the wireless device 1502. At the wireless device 1502, a reception processing system 1522 may receive the downlink transmission from base station 1504. The reception processing system 1512 and the reception processing system 1522 may implement layer 1 OSI functionality. Layer 1 may include a PHY layer with respect to FIG. 2A, FIG. 2B, FIG. 3, and FIG. 4A. For receive processing, the PHY layer may perform, for example, error detection, forward error correction decoding, deinterleaving, demapping of transport channels to physical channels, demodulation of physical channels, MIMO or multi-antenna processing, and/or the like.

[0248] As shown in FIG. 15, a wireless device 1502 and the base station 1504 may include multiple antennas. The multiple antennas may be used to perform one or more MIMO or multi-antenna techniques, such as spatial multiplexing (e.g., single-user MIMO or multi-user MIMO), transmit/receive diversity, and/or beamforming. In other examples, the wireless device 1502 and/or the base station 1504 may have a single antenna.

[0249] The processing system 1508 and the processing system 1518 maybe associated with a memory 1514 and a memory 1524, respectively. Memory 1514 and memory 1524 (e.g., one or more non-transitory computer readable mediums) may store computer program instructions or code that may be executed by the processing system 1508 and/or the processing system 1518 to carry out one or more of the functionalities discussed in the present application. Although not shown in FIG. 15, the transmission processing system 1510, the transmission processing system 1520, the reception processing system 1512, and/or the reception processing system 1522 may be coupled to a memory (e.g., one or more non-transitory computer readable mediums) storing computer program instructions or code that may be executed to carry out one or more of their respective functionalities. [0250] The processing system 1508 and/or the processing system 1518 may comprise one or more controllers and/or one or more processors. The one or more controllers and/or one or more processors may comprise, for example, a general-purpose processor, a digital signal processor (DSP), a microcontroller, an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) and/or other programmable logic device, discrete gate and/or transistor logic, discrete hardware components, an on-board unit, or any combination thereof. The processing system 1508 and/or the processing system 1518 may perform at least one of signal coding/processing, data processing, power control, input/output processing, and/or any other functionality that may enable the wireless device 1502 and the base station 1504 to operate in a wireless environment.

[0251] The processing system 1508 and/or the processing system 1518 may be connected to one or more peripherals 1516 and one or more peripherals 1526, respectively. The one or more peripherals 1516 and the one or more peripherals 1526 may include software and/or hardware that provide features and/or functionalities, for example, a speaker, a microphone, a keypad, a display, a touchpad, a power source, a satellite transceiver, a universal serial bus (USB) port, a hands-free headset, a frequency modulated (FM) radio unit, a media player, an Internet browser, an electronic control unit (e.g., for a motor vehicle), and/or one or more sensors (e.g., an accelerometer, a gyroscope, a temperature sensor, a radar sensor, a lidar sensor, an ultrasonic sensor, a light sensor, a camera, and/or the like). The processing system 1508 and/or the processing system 1518 may receive user input data from and/or provide user output data to the one or more peripherals 1516 and/or the one or more peripherals 1526. The processing system 1518 in the wireless device 1502 may receive power from a power source and/or may be configured to distribute the power to the other components in the wireless device 1502. The power source may comprise one or more sources of power, for example, a battery, a solar cell, a fuel cell, or any combination thereof. The processing system 1508 and/or the processing system 1518 may be connected to a GPS chipset 1517 and a GPS chipset 1527, respectively. The GPS chipset 1517 and the GPS chipset 1527 may be configured to provide geographic location information of the wireless device 1502 and the base station 1504, respectively.

[0252] FIG. 16A illustrates an example structure for uplink transmission. A baseband signal representing a physical uplink shared channel may perform one or more functions. The one or more functions may comprise at least one of: scrambling; modulation of scrambled bits to generate complex-valued symbols; mapping of the complex-valued modulation symbols onto one or several transmission layers; transform precoding to generate complex-valued symbols; precoding of the complex-valued symbols; mapping of precoded complex-valued symbols to resource elements; generation of complex-valued time-domain Single Carrier-Frequency Division Multiple Access (SC-FDMA) or CP- OFDM signal for an antenna port; and/or the like. In an example, when transform precoding is enabled, a SC-FDMA signal for uplink transmission may be generated. In an example, when transform precoding is not enabled, a CP-OFDM signal for uplink transmission may be generated by FIG. 16A. These functions are illustrated as examples and it is anticipated that other mechanisms may be implemented in various embodiments. [0253] FIG. 16B illustrates an example structure for modulation and up-conversion of a baseband signal to a carrier frequency. The baseband signal may be a complex-valued SC-FDMA or CP-OFDM baseband signal for an antenna port and/or a complex-valued Physical Random Access Channel (PRACH) baseband signal. Filtering may be employed prior to transmission.

[0254] FIG. 160 illustrates an example structure for downlink transmissions. A baseband signal representing a physical downlink channel may perform one or more functions. The one or more functions may comprise: scrambling of coded bits in a codeword to be transmitted on a physical channel; modulation of scrambled bits to generate complexvalued modulation symbols; mapping of the complex-valued modulation symbols onto one or several transmission layers; precoding of the complex-valued modulation symbols on a layer for transmission on the antenna ports; mapping of complex-valued modulation symbols for an antenna port to resource elements; generation of complex-valued timedomain OFDM signal for an antenna port; and/or the like. These functions are illustrated as examples and it is anticipated that other mechanisms may be implemented in various embodiments.

[0255] FIG. 16D illustrates another example structure for modulation and up-conversion of a baseband signal to a carrier frequency. The baseband signal may be a complex-valued OFDM baseband signal for an antenna port. Filtering may be employed prior to transmission.

[0256] A wireless device may receive from a base station one or more messages (e.g. RRC messages) comprising configuration parameters of a plurality of cells (e.g. primary cell, secondary cell). The wireless device may communicate with at least one base station (e.g. two or more base stations in dual connectivity) via the plurality of cells. The one or more messages (e.g. as a part of the configuration parameters) may comprise parameters of physical, MAC, RLC, PCDP, SDAP, RRC layers for configuring the wireless device. For example, the configuration parameters may comprise parameters for configuring physical and MAC layer channels, bearers, etc. For example, the configuration parameters may comprise parameters indicating values of timers for physical, MAC, RLC, PCDP, SDAP, RRC layers, and/or communication channels.

[0257] A timer may begin running once it is started and continue running until it is stopped or until it expires. A timer may be started if it is not running or restarted if it is running. A timer may be associated with a value (e.g. the timer may be started or restarted from a value or may be started from zero and expire once it reaches the value). The duration of a timer may not be updated until the timer is stopped or expires (e.g., due to BWP switching). A timer may be used to measure a time period/window for a process. When the specification refers to an implementation and procedure related to one or more timers, it will be understood that there are multiple ways to implement the one or more timers. For example, it will be understood that one or more of the multiple ways to implement a timer may be used to measure a time period/window for the procedure. For example, a random access response window timer may be used for measuring a window of time for receiving a random access response. In an example, instead of starting and expiry (or expiration) of a random access response window timer, the time difference between two time stamps may be used. When a timer is restarted, a process for measurement of time window may be restarted. Other example implementations may be provided to restart a measurement of a time window.

[0258] In the present disclosure, any two or more than two of the following sentences, paragraphs, (sub)-bullets, points, actions, behaviors, terms, alternatives, aspects, examples, or claims described in the following invention(s) may be combined logically, reasonably, and properly to form a specific method.

[0259] In the present disclosure, any sentence, paragraph, (sub)-bullet, point, action, behaviors, terms, alternatives, aspects, examples, or claims described in the following invention(s) may be implemented independently and separately to form a specific method.

[0260] In the present disclosure, dependency, such as “based on”, “more specifically”, “preferably”, “in one embodiment”, “in one alternative”, “in one example”, “in one aspect”, “in one implementation”, etc., in the present disclosure is just one possible example which would not restrict the specific method.

[0261] In the present disclosure, it should be understood that any discussion of operations from the perspective of wireless device may also be applied to a base station. Reciprocal operations may not be stated explicitly for each and every operation, although it is implied and a part of the present disclosure. For example, when the present disclosure describes one or more embodiments in which a transmitter device (e.g., a wireless device or a base station) transmits a signal, a receiver device (e.g., a wireless device or a base station) receives the signal. Reciprocal determinations and/or timer operations may occur to ensure alignment between operations of the transmitter device and receiver device. Furthermore, as an example of reciprocal operations, a wireless device may determine a time to transmit a signal based on a grant and a base station may determine the time to receive the signal and/or determine the time to schedule the signal for the wireless device to transmit via the grant. Similarly, as another reciprocal operation, if a receiver device (e.g., a wireless device or a base station) monitors for a signal or monitors a channel, a transmitter device (e.g., a wireless device or a base station) transmits the signal or transmits the channel.

[0262] User Equipment (UE) may report its UE radio access capabilities which are static at least when the Base Station (BS) requests. The BS may request what capabilities for the UE to report based on band information. The UE capability may be represented by a capability ID, which may be exchanged in Non-Access Stratum (NAS) signaling over the air and in network signaling instead of the UE capability structure.

[0263] UE may receive a UECapabilityEnquiry message from the BS. In response to the UECapability Enquiry message, UE may set the contents of UECapabilitylnformation message based on some conditions and/or UE may transmit the UECapabilitylnformation message to the BS.

[0264] BS may initiate a procedure to a UE in RRC_CONNECTED when it needs (additional) UE capability information. BS may retrieve UE capabilities after AS security activation. Network may not forward UE capabilities that were retrieved before Access Stratum (AS) security activation to the Core Network (CN). [0265] UE may transmit, to BS, an UE assistance information via an IE UEAssistancelnformation. UE may transmit, to BS, an UE assistance information via an IE UEAssistancelnformation based on a configuration received from the BS. The configuration may be included in a Radio Resource Control (RRC) message (e.g., RRC Reconfiguration message). [0266] Radio Link Control (RLC) layer (referred to as RLC sublayer) may support Transparent Mode (TM), Unacknowledged Mode (UM), and/or Acknowledged Mode (AM).

[0267] RLC configuration may be configured per logical channel with no dependency on numerologies and/or transmission durations, and Automatic Repeat reQuest (ARQ) may operate on any of the numerologies and/or transmission durations the logical channel is configured with.

[0268] For SRBO, paging and broadcast system information, TM mode may be used. For other Signaling Radio Bearers (SRBs) AM mode may be used. For Data Radio Bearers (DRBs), either UM or AM ode may be used.

[0269] The services and functions of the RLC layer depend on the transmission mode and comprise:

- Transfer of upper layer (e.g., Packet Data Convergence Protocol (PDCP)) Protocol Data Units (PDUs);

- Sequence numbering independent of the one in PDCP (e.g., in UM and/or AM);

- Error Correction through ARQ (e.g., in AM);

- Segmentation (e.g., in AM and/or UM) and/or re-segmentation (e.g., in AM) of RLC Service Data Units (SDUs);

- Reassembly of SDU (e.g., in AM and/or UM);

- Duplicate Detection (e.g., in AM);

- RLC SDU discard (e.g., in AM);

- RLC re-establishment; and/or

- Protocol error detection (e.g., AM only).

[0270] The ARQ mechanism within the RLC layer may have the following characteristics:

- ARQ retransmits RLC SDUs and/or RLC SDU segments based on RLC status reports;

- Polling for RLC status report may be used when needed by RLC; and/or

- RLC receiver may trigger RLC status report after detecting a missing RLC SDU and/or RLC SDU segment.

[0271] RRC may be in control of the RLC configuration. Functions of the RLC (sub)layer may be performed by RLC entities. For an RLC entity configured at the gNB, there is a peer RLC entity configured at the UE and vice versa. An RLC entity may receive/deliver RLC SDUs from/to upper layer (e.g., PDCP) and sends/receives RLC PDUs to/from its peer RLC entity via lower layers (e.g., Medium Access Control (MAC) and/or Physical Layer (PHY)).

[0272] An RLC PDU may be either be an RLC data PDU or an RLC control PDU. If an RLC entity receives RLC SDUs from upper layer (e.g., PDCP), it receives them through a single RLC channel between RLC and upper layer (e.g., PDCP), and after forming RLC data PDUs from the received RLC SDUs, the RLC entity submits the RLC data PDUs to lower layer (e.g., MAC and/or PHY) through a single logical channel. If an RLC entity receives RLC data PDUs from lower layer (e.g., MAC and/or PHY), it receives them through a single logical channel, and after forming RLC SDUs from the received RLC data PDUs, the RLC entity may deliver the RLC SDUs to upper layer (e.g., PDCP) through a single RLC channel between RLC and upper layer (e.g., PDCP). If an RLC entity submits/receives RLC control PDUs to/from lower layer (e.g., MAC and/or PHY), it submits/receives them through the same logical channel it submits/receives the RLC data PDUs through.

[0273] An RLC entity may be configured to perform data transfer in one of the following three modes: Transparent Mode (TM), Unacknowledged Mode (UM) and/or Acknowledged Mode (AM). Consequently, an RLC entity may be categorized as a TM RLC entity (e.g., referred to as TM RLC), an UM RLC entity (e.g., referred to as UM RLC) or an AM RLC entity (e.g., referred to as AM RLC) depending on the mode of data transfer that the RLC entity is configured to provide.

[0274] A TM RLC entity may be configured either as a transmitting TM RLC entity (e.g., referred to as transmitting TM RLC) or a receiving TM RLC entity (e.g., referred to as receiving TM RLC). The transmitting TM RLC entity may receive RLC SDUs from upper layer (e.g., PDCP) and sends RLC PDUs to its peer receiving TM RLC entity via lower layers (e.g., MAC and/or PHY). The receiving TM RLC entity may deliver RLC SDUs to upper layer and may receive RLC PDUs from its peer transmitting TM RLC entity via lower layers (e.g., MAC and/or PHY).

[0275] An UM RLC entity may be configured either as a transmitting UM RLC entity (e.g., referred to as transmitting UM RLC) or a receiving UM RLC entity (e.g., referred to as receiving UM RLC). The transmitting UM RLC entity may receive RLC SDUs from upper layer (e.g., PDCP) and sends RLC PDUs to its peer receiving UM RLC entity via lower layers (e.g., MAC and/or PHY). The receiving UM RLC entity may deliver RLC SDUs to upper layer (e.g., PDCP) and may receive RLC PDUs from its peer transmitting UM RLC entity via lower layers (e.g., MAC and/or PHY).

[0276] An AM RLC entity may comprise a transmitting side and a receiving side. The transmitting side of an AM RLC entity (e.g., referred to as transmitting AM RLC) may receive RLC SDUs from upper layer (e.g., PDCP) and sends RLC PDUs to its peer AM RLC entity via lower layers (e.g., MAC and/or PHY). The receiving side of an AM RLC entity (e.g., referred to as receiving AM RLC) may deliver RLC SDUs to upper layer (e.g., PDCP) and may receive RLC PDUs from its peer AM RLC entity via lower layers (e.g., MAC and/or PHY).

[0277] RLC SDUs of variable sizes which are byte aligned (e.g., multiple of 8 bits) may be supported for all RLC entity types (e.g., TM, UM and/or AM RLC entity).

[0278] Each RLC SDU may be used to construct an RLC PDU without waiting for notification from the lower layer (e.g., by MAC) of a transmission opportunity. In the case of UM and AM RLC entities, an RLC SDU may be segmented and transported using two or more RLC PDUs based on the notification(s) from the lower layer (e.g., by MAC).

[0279] RLC PDUs may be submitted to lower layer (e.g., MAC) only when a transmission opportunity has been notified by lower layer (i.e. by MAC).

[0280] A TM RLC entity may be configured to submit/receive RLC PDUs through the following logical channels: BCCH, DL/UL CCCH, PCCH, and/or SBCCH. A TM RLC entity may submit/receive the following RLC data PDU: TM Data (TMD) PDU. When a transmitting TM RLC entity forms TMD PDUs from RLC SDUs, it may not segment the RLC SDUs; and/or may not include any RLC headers in the TMD PDUs. When a receiving TM RLC entity receives TMD PDUs, it may not deliver the TMD PDUs (which are just RLC SDUs) to upper layer (e.g., PDCP).

[0281] An UM RLC entity may be configured to submit/receive RLC PDUs through the following logical channels: DL/UL DTCH, SCCH, STCH, MCCH, and/or MTCH. An UM RLC entity may submit/receive the following RLC data PDU: UM data (UMD) PDU. An UMD PDU may comprise either one complete RLC SDU or one RLC SDU segment. The transmitting UM RLC entity may generate UMD PDU(s) for each RLC SDU. The transmitting UM RLC entity may include relevant RLC headers in the UMD PDU. When notified of a transmission opportunity by the lower layer (e.g., MAC), the transmitting UM RLC entity may segment the RLC SDUs, e.g. if needed, so that the corresponding UMD PDUs, with RLC headers may be updated as needed, fit within the total size of RLC PDU(s) indicated by lower layer (e.g., MAC). When a receiving UM RLC entity receives UMD PDUs, it may detect the loss of RLC SDU segments at lower layers; may reassemble RLC SDUs from the received UMD PDUs and deliver the RLC SDUs to upper layer (e.g., PDCP) as soon as they are available; and/or may discard received UMD PDUs that cannot be re-assembled into an RLC SDU due to loss at lower layers (e.g., MAC and/or PHY) of an UMD PDU which belonged to the particular RLC SDU.

[0282] An AM RLC entity may be configured to submit/receive RLC PDUs through the following logical channels: DL/UL DCCH, DL/UL DTCH, SCCH, and/or STCH. An AM RLC entity may deliver/receive the following RLC data PDUs: AM Data (AMD) PDU. An AMD PDU may comprise either one complete RLC SDU or one RLC SDU segment. An AM RLC entity may deliver/receive the following RLC control PDU: STATUS PDU. The transmitting side of an AM RLC entity may generate AMD PDU(s) for each RLC SDU. When notified of a transmission opportunity by the lower layer (e.g., MAC and/or PHY), the transmitting AM RLC entity may segment the RLC SDUs, e.g., if needed, so that the corresponding AMD PDUs, with RLC headers may be updated as needed, fit within the total size of RLC PDU(s) indicated by lower layer (e.g., MAC and/or PHY).

[0283] The transmitting side of an AM RLC entity may support retransmission of RLC SDUs or RLC SDU segments (ARQ): if the RLC SDU or RLC SDU segment to be retransmitted (including the RLC header) does not fit within the total size of RLC PDU(s) indicated by lower layer (e.g., MAC and/or PHY) at the particular transmission opportunity notified by lower layer (e.g., MAC and/or PHY), the AM RLC entity may segment the RLC SDU or re-segment the RLC SDU segments into RLC SDU segments; the number of re-segmentation may be not limited. When the transmitting side of an AM RLC entity forms AMD PDUs from RLC SDUs or RLC SDU segments, the transmitting side of an AM RLC entity may include relevant RLC headers in the AMD PDU.

[0284] When the receiving side of an AM RLC entity receives AMD PDUs, it may detect whether or not the AMD PDUs have been received in duplication, and discard duplicated AMD PDUs; and/or may detect the loss of AMD PDUs at lower layers and request retransmissions to its peer AM RLC entity; and/or may reassemble RLC SDUs from the received AMD PDUs and deliver the RLC SDUs to upper layer (e.g., PDCP) as soon as they are available. [0285] When upper layers (e.g. , RRC and/or PDCP) request an RLC entity establishment, the UE may establish a RLC entity; and/or may set the state variables of the RLC entity to initial values. When upper layers (e.g., RRC and/or PDCP) request an RLC entity re-establishment, the UE may discard all RLC SDUs, RLC SDU segments, and/or RLC PDUs, if any; and/or may stop and reset all timers; and/or may reset all state variables to their initial values. When upper layers (e.g., RRC and/or PDCP) request an RLC entity release, the UE may discard all RLC SDUs, RLC SDU segments, and RLC PDUs, if any; and/or may release the RLC entity.

[0286] The transmitting side of an AM RLC entity may prioritize transmission of RLC control PDUs over AM Data (AMD PDU). The transmitting side of an AM RLC entity may prioritize transmission of AMD PDUs containing previously transmitted RLC SDUs or RLC SDU segments over transmission of AMD PDUs containing not previously transmitted RLC SDUs or RLC SDU segments.

[0287] The transmitting side of an AM RLC entity may maintain a transmitting window according to the state variable TX_Next_Ack as follows: a SN falls within the transmitting window if TX_Next_Ack <= SN < TX_Next_Ack + AM_Window_Size; and/or a SN falls outside of the transmitting window otherwise. The transmitting side of an AM RLC entity may not submit to lower layer (e.g., MAC and/or PHY) any AMD PDU whose Sequence Number (SN) falls outside of the transmitting window.

[0288] For each RLC SDU received from the upper layer (e.g., PDCP), the AM RLC entity may associate a SN with the RLC SDU equal to TX_Next and construct an AMD PDU by setting the SN of the AMD PDU to TX_Next; and/or may increment TX_Next by one. When submitting an AMD PDU that contains a segment of an RLC SDU, to lower layer (e.g., MAC and/or PHY), the transmitting side of an AM RLC entity may set the SN of the AMD PDU to the SN of the corresponding RLC SDU.

[0289] The transmitting side of an AM RLC entity may receive a positive acknowledgement (e.g., ACK and/or confirmation of successful reception by its peer AM RLC entity) for an RLC SDU by the following: STATUS PDU from its peer AM RLC entity. When receiving a positive acknowledgement (e.g., ACK) for an RLC SDU with SN = x, the transmitting side of an AM RLC entity may send an indication to the upper layers (e.g., PDCP and/or RRC) of successful delivery of the RLC SDU; and/or may set TX_Next_Ack equal to the SN of the RLC SDU with the smallest SN, whose SN falls within the range TX_Next_Ack <= SN <= TX_Next and for which a positive acknowledgment has not been received yet.

[0290] The receiving side of an AM RLC entity may maintain a receiving window according to the state variable RX_Next as follows: a SN falls within the receiving window if RX_Next <= SN < RX_Next + AM_Window_Size; and/or a SN falls outside of the receiving window otherwise. When receiving an AMD PDU from lower layer (e.g., MAC and/or PHY), the receiving side of an AM RLC entity may: either discard the received AMD PDU or place it in the reception buffer; and/or if the received AMD PDU was placed in the reception buffer: update state variables, reassemble and deliver RLC SDUs to upper layer (e.g., PDCP and/or RRC) and start/stop t-Reassembly as needed. When t- Reassembly expires, the receiving side of an AM RLC entity may update state variables and start t-Reassembly as needed.

[0291] When an AMD PDU is received from lower layer (e.g., MAC and/or PHY), where the AMD PDU comprises byte segment numbers y to z of an RLC SDU with SN = x, the receiving side of an AM RLC entity may:

- if x falls outside of the receiving window; and/or if byte segment numbers y to z of the RLC SDU with SN = x have been received before: discard the received AMD PDU.

- else: o place the received AMD PDU in the reception buffer; o if some byte segments of the RLC SDU contained in the AMD PDU have been received before: discard the duplicate byte segments.

[0292] When an AMD PDU with SN = x is placed in the reception buffer, the receiving side of an AM RLC entity shall:

- if x >= RX_Next_H ighest: update RX_Next_Highest to x+ 1.

- if all bytes of the RLC SDU with SN = x are received: o reassemble the RLC SDU from AMD PDU(s) with SN = x, remove RLC headers when doing so and deliver the reassembled RLC SDU to upper layer; o if x = RX_Highest_Status: update RX_H ighest_Status to the SN of the first RLC SDU with SN > current RX_H ighest_Status for which not all bytes have been received. o if x = RX_Next: update RX_Next to the SN of the first RLC SDU with SN > current RX_Next for which not all bytes have been received.

- if t-Reassembly is running: o if RX_Next_Status_T rigger = RX_Next; and/or if RX_N ext_Status_T rigger = RX_Next + 1 and there is no missing byte segment of the SDU associated with SN = RX_Next before the last byte of all received segments of this SDU; and/or if RX_Next_Status_T rigger falls outside of the receiving window and RX_Next_Status_T rigger is not equal to RX_Next + AM_Window_Size:

■ stop and reset t-Reassembly.

- if t-Reassembly is not running (includes the case t-Reassembly is stopped due to actions above): o if RX_Next_H ighest> RX_Next +1 ; and/or if RX_Next_Highest = RX_Next + 1 and there is at least one missing byte segment of the SDU associated with SN = RX_Next before the last byte of all received segments of this SDU:

■ start t-Reassembly; and/or set RX_Next_S tatu s_T rigger to RX_Next_H i gh est.

[0293] When t-Reassembly expires, the receiving side of an AM RLC entity may:

- update RX_Highest_Status to the SN of the first RLC SDU with SN >= RX_Next_Status_T rigger for which not all bytes have been received; - if RX_Next_H ighest> RX_Highest_Status +1 : and/or if RX_Next_H ighest = RX_Highest_Status + 1 and there is at least one missing byte segment of the SDU associated with SN = RX_H ighest_Status before the last byte of all received segments of this SDU: o start t-Reassembly; and/or set RX_Next_S tatu s_T rigger to RX_Next_H i gh est.

[0294] ARQ procedures may be performed by an AM RLC entity.

[0295] The transmitting side of an AM RLC entity may receive a negative acknowledgement (e.g., NACK and/or notification of reception failure by its peer AM RLC entity) for an RLC SDU or an RLC SDU segment by the following: STATUS PDU from its peer AM RLC entity.

[0296] When receiving a negative acknowledgement (e.g., NACK) for an RLC SDU or an RLC SDU segment by a STATUS PDU from its peer AM RLC entity, the transmitting side of the AM RLC entity may:

- if the SN of the corresponding RLC SDU falls within the range TX_Next_Ack <= SN < = the highest SN of the AMD PDU among the AMD PDUs submitted to lower layer: o consider the RLC SDU or the RLC SDU segment for which a negative acknowledgement was received for retransmission.

[0297] When an RLC SDU or an RLC SDU segment is considered for retransmission, the transmitting side of the AM RLC entity may:

- if the RLC SDU or RLC SDU segment is considered for retransmission for the first time: set the RETX_COUNT associated with the RLC SDU to zero.

- else, if it (e.g., the RLC SDU or the RLC SDU segment that is considered for retransmission) is not pending for retransmission already and the RETX_COUNT associated with the RLC SDU has not been incremented due to another negative acknowledgment in the same STATUS PDU: increment the RETX_COUNT.

- if RETX_COUNT = maxRetxThreshold: indicate to upper layers (e.g., RRC) that max retransmission has been reached.

[0298] When retransmitting an RLC SDU or an RLC SDU segment, the transmitting side of an AM RLC entity may: if needed, segment the RLC SDU or the RLC SDU segment; and/or may form a new AMD PDU which will fit within the total size of AMD PDU(s) indicated by lower layer at the particular transmission opportunity; and/or may submit the new AMD PDU to lower layer (e.g., MAC).

[0299] When forming a new AMD PDU, the transmitting side of an AM RLC entity may: only map the original RLC SDU or RLC SDU segment to the Data field of the new AMD PDU; and/or may modify the header of the new AMD PDU; and/or may set the P field.

[0300] An AM RLC entity may poll its peer AM RLC entity in order to trigger STATUS reporting at the peer AM RLC entity. [0301] Upon notification of a transmission opportunity by lower layer (e.g. , MAC), for each AMD PDU submitted for transmission such that the AMD PDU contains either a not previously transmitted RLC SDU or an RLC SDU segment containing not previously transmitted byte segment, the transmitting side of an AM RLC entity may:

- increment PDU_WITHOUT_POLL by one; and/or increment BYTE_WITHOUT_POLL by every new byte of Data field element that it maps to the Data field of the AMD PDU;

- if PDU_WITHOUT_POLL >= pollPDU; and/or if BYTE_WITHOUT_POLL >= pollByte: o include a poll in the AMD PDU.

[0302] Upon notification of a transmission opportunity by lower layer (e.g., MAC), for each AMD PDU submitted for transmission, the transmitting side of an AM RLC entity may:

- if both the transmission buffer and the retransmission buffer become empty (excluding transmitted RLC SDUs or RLC SDU segments awaiting acknowledgements) after the transmission of the AMD PDU; and/or if no new RLC SDU can be transmitted after the transmission of the AMD PDU (e.g. due to window stalling): o include a poll in the AMD PDU.

[0303] To include a poll in an AMD PDU, the transmitting side of an AM RLC entity may: set the P field of the AMD PDU to "1"; and/or may set PDU_WITHOUT_POLL to 0; and/or may set BYTE_WITHOUT_POLL to 0.

[0304] Upon submission of an AMD PDU including a poll to lower layer (e.g., MAC), the transmitting side of an AM RLC entity may:

- set POLL_SN to the highest SN of the AMD PDU among the AMD PDUs submitted to lower layer;

- if t-Poll Retransm it is not running: start t-Pol I Retransmit.

- else: restart t-PollRetransmit.

[0305] Upon reception of a STATUS report from the receiving RLC AM entity the transmitting side of an AM RLC entity may:

- if the STATUS report comprises a positive (e.g., ACK) or negative acknowledgement (e.g., NACK) for the RLC SDU with sequence number equal to POLL_SN and/or if t-Poll Retransmit is running: Stop and reset t- PollRetransmit.

[0306] Upon expiry of t-Poll Retransmit, the transmitting side of an AM RLC entity may:

- if both the transmission buffer and the retransmission buffer are empty (excluding transmitted RLC SDU or RLC SDU segment awaiting acknowledgements); and/or if no new RLC SDU or RLC SDU segment can be transmitted (e.g. due to window stalling): o consider the RLC SDU with the highest SN among the RLC SDUs submitted to lower layer for retransmission; and/or consider any RLC SDU which has not been positively acknowledged (e.g., ACKed) for retransmission. o include a poll in an AMD PDU. [0307] An AM RLC entity may send STATUS PDUs to its peer AM RLC entity in order to provide positive and/or negative acknowledgements of RLC SDUs (or portions of them).

[0308] Triggers to initiate STATUS reporting include:

- Polling from its peer AM RLC entity: o When an AMD PDU with SN = x and the P field set to "1 " is received from lower layer, the receiving side of an AM RLC entity may:

■ if the AMD PDU is to be discarded; and/or if x < RX_Highest_Status or x >= RX_Next + AM_Window_Size: trigger a STATUS report.

■ else: delay triggering the STATUS report until x < RX_Highest_Status or x >= RX_Next + AM_Window_Size.

- Detection of reception failure of an AMD PDU: the receiving side of an AM RLC entity may trigger a STATUS report when t-Reassembly expires.

[0309] The expiry of t-Reassembly triggers both RX_H ighest_Status to be updated and a STATUS report to be triggered, but the STATUS report may be triggered after RX_Highest_Status is updated.

[0310] When STATUS reporting has been triggered, the receiving side of an AM RLC entity may:

- if t-StatusProhibit is not running: at the first transmission opportunity indicated by lower layer (e.g., MAC), construct a STATUS PDU and submit it to lower layer (e.g., MAC).

- else: at the first transmission opportunity indicated by lower layer (e.g., MAC) after t-StatusProhibit expires, construct a single STATUS PDU even if status reporting was triggered several times while t-StatusProhibit was running and submit it to lower layer (e.g., MAC).

[0311] When a STATUS PDU has been submitted to lower layer (e.g., MAC), the receiving side of an AM RLC entity may start t-StatusProhibit.

[0312] When constructing a STATUS PDU, the AM RLC entity may:

- for the RLC SDUs with SN such that RX_Next <= SN < RX_Highest_Status that has not been completely received yet, in increasing SN order of RLC SDUs and increasing byte segment order within RLC SDUs, starting with SN = RX_Next up to the point where the resulting STATUS PDU still fits to the total size of RLC PDU(s) indicated by lower layer (e.g., MAC): o for an RLC SDU for which no byte segments have been received yet:

■ include in the STATUS PDU a NACK_SN which is set to the SN of the RLC SDU. o for a continuous sequence of byte segments of a partly received RLC SDU that have not been received yet:

■ include in the STATUS PDU a set of NACK_SN, SOstart and SOend. o for a continuous sequence of RLC SDUs that have not been received yet:

■ include in the STATUS PDU a set of NACK_SN and NACK range; ■ include in the STATUS PDU, if required, a pair of SOstart and SOend.

- set the ACK_SN to the SN of the next not received RLC SDU which is not indicated as missing in the resulting STATUS PDU.

[0313] When indicated from upper layer (e.g. PDCP) to discard a particular RLC SDU, the transmitting side of an AM RLC entity or the transmitting UM RLC entity may discard the indicated RLC SDU, if neither the RLC SDU nor a segment thereof has been submitted to the lower layers (e.g., MAC and/or PHY). The transmitting side of an AM RLC entity may not introduce an RLC SN gap when discarding an RLC SDU.

[0314] RLC PDUs may be categorized into RLC data PDUs and/or RLC control PDUs. RLC data PDUs may be used by TM, UM and/or AM RLC entities to transfer upper layer PDUs (e.g., RLC SDUs and/or PDCP PDUs). RLC control PDUs may be used by AM RLC entity to perform ARQ procedures. TMD PDU may be used to transfer upper layer PDUs (e.g., RLC SDUs and/or PDCP PDUs) by a TM RLC entity. UMD PDU may be used to transfer upper layer PDUs (e.g., RLC SDUs and/or PDCP PDUs) by an UM RLC entity. AMD PDU may be used to transfer upper layer PDUs (e.g., RLC SDUs and/or PDCP PDUs) by an AM RLC entity. STATUS PDU may be used by the receiving side of an AM RLC entity to inform the peer AM RLC entity about RLC data PDUs that are received successfully, and RLC data PDUs that are detected to be lost by the receiving side of an AM RLC entity.

[0315] TMD PDU may consists only of a Data field and may not consist of any RLC headers.

[0316] UMD PDU may consist of a Data field and an UMD PDU header. The UMD PDU header may be byte aligned. When an UMD PDU contains a complete RLC SDU, the UMD PDU header may only contain the SI and R fields. An UM RLC entity may be configured by RRC/BS to use either a 6 bit SN or a 12 bit SN. An UMD PDU header may contain the SN field only when the corresponding RLC SDU is segmented. An UMD PDU may carry the first segment of an RLC SDU does not carry the SO field in its header. The length of the SO field may be 16 bits.

[0317] AMD PDU may consist of a Data field and an AMD PDU header. The AMD PDU header may be byte aligned. An AM RLC entity may be configured by RRC/BS to use either a 12 bit SN or a 18 bit SN. The length of the AMD PDU header may be two and three bytes respectively. An AMD PDU header may contain a D/C, a P, a SI, and a SN fields. An AMD PDU header may contain the SO field only when the Data field consists of an RLC SDU segment which is not the first segment, in which case a 16 bit SO may be present.

[0318] STATUS PDU may consist of a STATUS PDU payload and an RLC control PDU header. RLC control PDU header may consist of a D/C and a CPT field. The STATUS PDU payload may start from the first bit following the RLC control PDU header, and it may consist of one ACK_SN and one E1, zero or more sets of a NACK_SN, an E1, an E2 and an E3, and possibly a pair of a SOstart and a SOend or a NACK range field for each NACK_SN.

[0319] In the definition of each field in the present disclosure, the bits in the parameters may be represented in which the first and most significant bit is the left most bit and the last and least significant bit is the rightmost bit. Integers may be encoded in standard binary encoding for unsigned integers. [0320] Data field elements may be mapped to the Data field in the order which they arrive to the RLC entity at the transmitter.

[0321] For TMD PDU, UMD PDU and AMD PDU: The granularity of the Data field size may be one byte; The maximum Data field size may be the maximum size of a PDCP PDU.

[0322] For TMD PDU: Only one RLC SDU may be mapped to the Data field of one TMD PDU.

[0323] For UMD PDU and AMD PDU: Either of the following can be mapped to the Data field of one UMD PDU, or AMD PDU: One RLC SDU; and/or One RLC SDU segment.

[0324] The length of Sequence Number (SN) field may be 12 bits or 18 bits (configurable) for AMD PDU. 6 bits or 12 bits (configurable) for UMD PDU. The SN field may indicate the sequence number of the corresponding RLC SDU. For

RLC AM, the sequence number may be incremented by one for every RLC SDU. For RLC UM, the sequence number may be incremented by one for every segmented RLC SDU.

[0325] The length of Segmentation Info (SI) field may be 2 bits. The SI field may indicate whether an RLC PDU contains a complete RLC SDU or the first, middle, last segment of an RLC SDU. The Table 2 shows the SI field interpretation.

[0326] Table 2: SI field interpretation

[0327] The length of the Segment Offset (SO) field may be 16 bits. The SO field may indicate the position of the RLC

SDU segment in bytes within the original RLC SDU. Specifically, the SO field indicates the position within the original RLC SDU to which the first byte of the RLC SDU segment in the Data field corresponds. The first byte of the original RLC SDU is referred by the SO field value "0000000000000000", e.g., numbering starts at zero.

[0328] The length of the Data/Control (D/C) field may be 1 bit. The D/C field may indicate whether the RLC PDU is an RLC data PDU or RLC control PDU. The interpretation of the D/C field is provided in Table 3.

[0329] Table 3: D/C field interpretation

[0330] The length of the Polling bit (P) field may be 1 bit. The field may indicate whether or not the transmitting side of an AM RLC entity requests a STATUS report from its peer AM RLC entity. The interpretation of the P field is provided in Table 4.

[0331] Table 4: P field interpretation

[0332] The length of the Reserved (R) field may be 1 bit. The R field may be a reserved field. The transmitting entity may set the R field to "0". The receiving entity may ignore this field.

[0333] The length of the Control PDU Type (OPT) field may be 3 bits. The OPT field may indicate the type of the RLC control PDU. The interpretation of the OPT field is provided in Table 5.

[0334] Table 5: OPT field interpretation

[0335] T he length of the Acknowledgement SN (ACK_SN) field may be 12 bits or 18 bits (which may be configurable, e.g., by RRC/BS). The ACK_SN field may indicate the SN of the next not received RLC SDU which is not reported as missing in the STATUS PDU. When the transmitting side of an AM RLC entity receives a STATUS PDU, it interprets that all RLC SDUs up to but not including the RLC SDU with SN = ACK_SN have been received by its peer AM RLC entity, excluding those RLC SDUs indicated in the STATUS PDU with NACK_SN, portions of RLC SDUs indicated in the STATUS PDU with NACK.SN, SOstart and SOend, RLC SDUs indicated in the STATUS PDU with NACK.SN and NACK.range, and portions of RLC SDUs indicated in the STATUS PDU with NACK_SN, NACK range, SOstart and SOend.

[0336] The length of the Extension bit 1 (E1) field may be 1 bit. The E1 field may indicate whether or not a set of NACK_SN, E1, E2 and E3 follows. The interpretation of the E1 field is provided in Table 6.

[0337] Table 6: E1 field interpretation

[0338] The length of the Negative Acknowledgement SN (NACK_SN) field may be 12 bits or 18 bits (which may be configurable, e.g., by RRC/BS). The NACK_SN field may indicate the SN of the RLC SDU (and/or RLC SDU segment) that has been detected as lost at the receiving side of the AM RLC entity.

[0339] The length of the Extension bit 2 (E2) field may be 1 bit. The E2 field may indicate whether or not a set of SOstart and SOend follows. The interpretation of the E2 field is provided in Table 7.

[0340] Table 7: E2 field interpretation

[0341] The length of the SO start (SOstart) field may be 16 bits. The SOstart field (e.g., together with the SOend field) may indicate the portion of the RLC SDU with SN = NACK_SN (the NACK_SN for which the SOstart is related to) that has been detected as lost at the receiving side of the AM RLC entity. Specifically, the SOstart field may indicate the position of the first byte of the portion of the RLC SDU in bytes within the original RLC SDU. The first byte of the original RLC SDU is referred by the SOstart field value "0000000000000000", e.g., numbering starts at zero.

[0342] The length of the SO end (SOend) field may be 16 bits. When E3 is 0, the SOend field (together with the SOstart field) may indicate the portion of the RLC SDU with SN = NACK_SN (the NACK_SN for which the SOend is related to) that has been detected as lost at the receiving side of the AM RLC entity. Specifically, the SOend field may indicate the position of the last byte of the portion of the RLC SDU in bytes within the original RLC SDU. The first byte of the original RLC SDU is referred by the SOend field value "0000000000000000", i.e., numbering starts at zero. The special SOend value "1111111111111111 " is used to indicate that the missing portion of the RLC SDU includes all bytes to the last byte of the RLC SDU. When E3 is 1 , the SOend field may indicate the portion of the RLC SDU with SN = NACK_SN + NACK range - 1 that has been detected as lost at the receiving side of the AM RLC entity. Specifically, the SOend field indicates the position of the last byte of the portion of the RLC SDU in bytes within the original RLC SDU. The first byte of the original RLC SDU is referred by the SOend field value "0000000000000000", e.g., numbering starts at zero. The special SOend value "1111111111111111" is used to indicate that the missing portion of the RLC SDU includes all bytes to the last byte of the RLC SDU.

[0343] The length of the Extension bit 3 (E3) field may be 1 bit. The E3 field may indicate whether or not information about a continuous sequence of RLC SDUs that have not been received follows. The interpretation of the E2 field is provided in Table 8.

[0344] Table 8: E3 field interpretation

[0345] The length of the NACK range field may be 8 bits. This NACK range field may be the number of consecutively lost RLC SDUs starting from and including NACK_SN.

[0346] The state variables related to AM data transfer may take values from 0 to 4095 for 12 bit SN and/or from 0 to 262143 for 18 bit SN. The arithmetic operations contained in the present disclosure on state variables related to AM data transfer may be affected by the AM modulus (e.g., final value = [value from arithmetic operation] modulo 4096 for 12 bit SN and 262144 for 18 bit SN). The state variables related to UM data transfer may take values from 0 to 63 for 6 bit SN or from 0 to 4095 for 12 bit SN. The arithmetic operations contained in the present disclosure on state variables related to UM data transfer may be affected by the UM modulus (e.g., final value = [value from arithmetic operation] modulo 64 for 6 bit SN and 4096 for 12 bit SN). When performing arithmetic comparisons of state variables or SN values, a modulus base may be used.

[0347] TX_Next_Ack and RX_Next may be assumed as the modulus base at the transmitting side and receiving side of an AM RLC entity, respectively. This modulus base may be subtracted from all the values involved, and then an absolute comparison is performed.

[0348] RX_Next_Highest- UM_Window_Size may be assumed as the modulus base at the receiving UM RLC entity. This modulus base may be subtracted from all the values involved, and then an absolute comparison is performed.

[0349] The transmitting side of each AM RLC entity may maintain the following state variables:

- TX_Next_Ack may be referred to as Acknowledgement (ACK) state variable and vice versa. The TX_Next_Ack state variable may hold the value of the SN of the next RLC SDU for which a positive acknowledgment is to be received in-sequence, and it serves as the lower edge of the transmitting window. It is initially set to 0, and is updated whenever the AM RLC entity receives a positive acknowledgment for an RLC SDU with SN = TX_Next_Ack.

- TX_Next may be referred to as Send state variable and vice versa. The TX_Next state variable may hold the value of the SN to be assigned for the next newly generated AMD PDU. It is initially set to 0, and is updated whenever the AM RLC entity constructs an AMD PDU with SN = TX_Next and contains an RLC SDU or the last segment of a RLC SDU.

- POLL_SN may be referred to as Poll send state variable and vice versa. The POLL_SN state variable may hold the value of the highest SN of the AMD PDU among the AMD PDUs submitted to lower layer when POLL_SN is set. It is initially set to 0.

[0350] The transmitting side of each AM RLC entity may maintain the following counters:

- PDU_WITHOUT_POLL may be referred to as a PDU Poll Counter and vice versa. The PDU_WITHOUT_POLL counter may be initially set to 0. It counts the number of AMD PDUs sent since the most recent poll bit was transmitted.

- BYTE_WITHOUT_POLL may be referred to as a Byte Poll Counter and vice versa. The BYTE_WITHOUT_POLL counter may be initially set to 0. It counts the number of data bytes sent since the most recent poll bit was transmitted.

- RETX_COUNT may be referred to as a Retransmission Counter and vice versa. The - RETX_COUNT counter counts the number of retransmissions of an RLC SDU or RLC SDU segment. There is one RETX_COUNT counter maintained per RLC SDU.

[0351] The receiving side of each AM RLC entity may maintain the following state variables:

- RX_Next may be referred to as a Receive state variable and vice versa. The RX_Next state variable holds the value of the SN following the last in-sequence completely received RLC SDU, and it serves as the lower edge of the receiving window. It is initially set to 0, and is updated whenever the AM RLC entity receives an RLC SDU with SN = RX.Next.

- RX_Next_S tatu s_T rigger may be referred to as a t-Reassembly state variable and vice versa. The RX_Next_Status_T rigger state variable holds the value of the SN following the SN of the RLC SDU which triggered t-Reassembly.

- RX_Highest_Status may be referred to as a Maximum STATUS transmit state variable and vice versa. The RX_H ighest_Status state variable holds the highest possible value of the SN which can be indicated by "ACK_SN" when a STATUS PDU needs to be constructed. It is initially set to 0.

- RX_Next_Highest may be referred to as a Highest received state variable and vice versa. The RX_Next_Highest state variable holds the value of the SN following the SN of the RLC SDU with the highest SN among received RLC SDUs. It is initially set to 0.

[0352] Each transmitting UM RLC entity shall maintain the following state variables:

- TX_Next may be referred to as a UM send state variable and vice versa. The TX_Next state variable holds the value of the SN to be assigned for the next newly generated UMD PDU with segment. It is initially set to 0, and is updated after the UM RLC entity submits a UMD PDU including the last segment of an RLC SDU to lower layers (e.g., MAC and/or PHY).

[0353] Each receiving UM RLC entity shall maintain the following state variables:

- RX_Next_ Reassembly may be referred to as a UM receive state variable and vice versa. The

RX_Next_ Reassembly state variable holds the value of the earliest SN that is still considered for reassembly. It is initially set to 0. For groupcast and broadcast of NR sidelink communication or for SL-SRB4 of NR sidelink discovery, it is initially set to the SN of the first received UMD PDU containing an SN. For the receiving UM RLC entity configured for MCCH or MTCH, it is up to UE implementation to set the initial value of RX_Next_ Reassembly to a value before RX_Next_Highest.

- RX_Timer_T rigger may be referred to as a UM t-Reassembly state variable and vice versa. The RX_Timer_T rigger state variable holds the value of the SN following the SN which triggered t-Reassembly.

- RX_Next_Highest may be referred to as a UM receive state variable and vice versa. The RX_Next_Highest state variable holds the value of the SN following the SN of the UMD PDU with the highest SN among received UMD PDUs. It serves as the higher edge of the reassembly window. It is initially set to 0.

[0354] The AM_Window_Size constant may be used by both the transmitting side and the receiving side of each AM RLC entity. AM_Window_Size = 2048 when a 12 bit SN is used, AM_Window_Size = 131072 when an 18 bit SN is used.

[0355] The UM_Window_Size constant may be used by the receiving UM RLC entity to define SNs of those UMD SDUs that can be received without causing an advancement of the receiving window. UM_Window_Size = 32 when a 6 bit SN is configured, UM_Window_Size = 2048 when a 12 bit SN is configured. [0356] The following timers may be configured by RRC/BS configuration parameters:

- The t-PollRetransmit timer may be used by the transmitting side of an AM RLC entity in order to retransmit a poll. The t-Poll Retransm it timer may be referred to as a Retransmission timer and vice versa.

- The t-Reassembly timer may be used by the receiving side of an AM RLC entity and receiving UM RLC entity in order to detect loss of RLC PDUs at lower layer. If t-Reassembly is running, t-Reassembly shall not be started additionally, i.e. only one t-Reassembly per RLC entity is running at a given time. The t-Poll Retransmit timer may be referred to as a Reassembly timer and vice versa.

- The t-StatusProhibit timer may be used by the receiving side of an AM RLC entity in order to prohibit transmission of a STATUS PDU. The t-StatusProhibit timer may be referred to as a prohibit timer and vice versa.

[0357] The following parameters may be configured by RRC/BS:

- The maxRetxThreshold parameter may be used by the transmitting side of each AM RLC entity to limit the number of retransmissions corresponding to an RLC SDU, including its segments.

- The pollPDU parameter may be used by the transmitting side of each AM RLC entity to trigger a poll for every pollPDU PDUs.

- The poll Byte parameter may be used by the transmitting side of each AM RLC entity to trigger a poll for every pollByte bytes.

[0358] For AM DRBs, when upper layers request a PDCP data recovery for a radio bearer, the transmitting PDCP entity may perform retransmission of all the PDCP Data PDUs previously submitted to re-established or released AM RLC entities in ascending order of the associated COUNT values for which the successful delivery has not been confirmed by lower layers, following the data submission procedure.

[0359] When upper layers request a PDCP entity re-establishment, the transmitting PDCP entity may, for UM DRBs and AM DRBs, reset the Robust Header Compression (ROHC) protocol for uplink and start with an I R state in U-mode, e.g., if drb-ContinueROHC is not configured.

[0360] When upper layers request a PDCP entity re-establishment, the transmitting PDCP entity may, for UM DRBs and AM DRBs, reset the Ethernet Header Compression (EHC) protocol for uplink if d rb-Contin ueEHC-U L is not configured.

[0361] When upper layers request a PDCP entity re-establishment, the transmitting PDCP entity may, for AM DRBs, reset the User Data Convergence (UDC) compression buffer to all zeros and prefill the dictionary, e.g., if drb- ContinueUDC is not configured.

[0362] When upper layers request a PDCP entity re-establishment, the transmitting PDCP entity may, for SRBs and UM DRBs, set TX_NEXT to the initial value.

[0363] When upper layers request a PDCP entity re-establishment, the transmitting PDCP entity may, for SRBs, discard all stored PDCP SDUs and PDCP PDUs. [0364] When upper layers request a PDCP entity re-establishment, the transmitting PDCP entity may, apply the ciphering algorithm and key provided by upper layers during the PDCP entity re-establishment procedure.

[0365] When upper layers request a PDCP entity re-establishment, the transmitting PDCP entity may, apply the integrity protection algorithm and key provided by upper layers during the PDCP entity re-establishment procedure. [0366] When upper layers request a PDCP entity re-establishment, the transmitting PDCP entity may, for UM DRBs, for each PDCP SDU already associated with a PDCP SN but for which a corresponding PDU has not previously been submitted to lower layers.

[0367] When upper layers request a PDCP entity re-establishment, the transmitting PDCP entity may, for AM DRBs for Uu interface whose PDCP entities were suspended, from the first PDCP SDU for which the successful delivery of the corresponding PDCP Data PDU has not been confirmed by lower layers, for each PDCP SDU already associated with a PDCP SN:

- consider the PDCP SDUs as received from upper layer;

- perform transmission of the PDCP SDUs in ascending order of the COUNT value associated to the PDCP SDU prior to the PDCP re-establishment without restarting the discardTimer or the discardTimerForLowl mportance.

[0368] When upper layers request a PDCP entity re-establishment, the transmitting PDCP entity may, for AM DRBs whose PDCP entities were not suspended, from the first PDCP SDU for which the successful delivery of the corresponding PDCP Data PDU has not been confirmed by lower layers, perform retransmission or transmission of all the PDCP SDUs already associated with PDCP SNs in ascending order of the COUNT values associated to the PDCP SDU prior to the PDCP entity re-establishment as specified below:

- perform header compression of the PDCP SDU using ROHC and/or using EHC;

- If drb-ContinueUDC is configured and if the PDCP SDU has been compressed before: o submit the PDCP SDU previously compressed to integrity protection and ciphering function;

- else: o perform uplink data compression of the PDCP SDU, and submit the PDCP SDU to integrity protection and ciphering function;

- perform integrity protection and ciphering of the PDCP SDU using the COUNT value associated with this PDCP SDU;

- submit the resulting PDCP Data PDU to lower layer.

[0369] When the successful delivery of a PDCP SDU is confirmed by PDCP status report, the transmitting PDCP entity may discard the PDCP SDU along with the corresponding PDCP Data PDU.

[0370] When the discardTimer and/or discardTimerForLowl mportance expires for a PDCP SDU, the transmitting PDCP entity may: - if pdu-SetDiscard is configured: discard all PDCP SDUs belonging to the PDU Set to which the PDCP SDU belongs along with the corresponding PDCP Data PDUs. Specifically, PDCP SDUs subsequently received from upper layers are also discarded if they belong to the PDU Set.

- else: discard the PDCP SDU along with the corresponding PDCP Data PDU.

[0371] If the corresponding PDCP Data PDU has already been submitted to lower layers, the discard may be indicated to lower layers.

[0372] For SRBs, when upper layers request a PDCP SDU discard, the PDCP entity may discard all stored PDCP SDUs and PDCP PDUs.

[0373] At reception of a PDCP SDU from upper layers, the transmitting PDCP entity may:

- if discardTimerForLowl mportance is configured and PSI based SDU discard is activated, and the PDCP SDU belongs to a low importance PDU Set: start the discardTimerForLowImportance associated with this PDCP SDU;

- else: start the discardTimer associated with this PDCP SDU (e.g., if configured).

[0374] For a PDCP SDU received from upper layers, the transmitting PDCP entity may:

- associate the COUNT value corresponding to TX_NEXT to this PDCP SDU;

- perform header compression of the PDCP SDU using ROHC and/or using EHC;

- perform uplink data compression of the PDCP SDU;

- perform integrity protection, and ciphering using the TX_NEXT ;

- set the PDCP SN of the PDCP Data PDU to TX.NEXT modulo 2[pdcp-SN-SizeUL];

- increment TX_NEXT by one; and/or

- submit the resulting PDCP Data PDU to lower layer.

[0375] When submitting a PDCP PDU to lower layer, the transmitting PDCP entity may:

- if the transmitting PDCP entity is associated with one SRAP entity: submit the PDCP PDU to the associated SRAP entity;

- else, if the transmitting PDCP entity is associated with one RLC entity: submit the PDCP PDU to the associated RLC entity;

- else, if the transmitting PDCP entity is associated with one or more RLC entities and, either one SRAP entity or the N3C: o if PDCP duplication is activated for the RB:

■ if the PDCP PDU is a PDCP Data PDU: duplicate the PDCP Data PDU and submit the PDCP Data PDU to both the primary path and secondary path, including any associated Uu RLC entities activated for PDCP duplication;

■ else: submit the PDCP Control PDU to the primary path; o else (e.g., PDCP duplication is deactivated for the RB): ■ if the total amount of PDCP data volume, RLC data volume pending for initial transmission in the RLC entity, and data volume pending for either transmission in the N3C (if available) or mapped SL RLC entity associated with the SRAP entity, is equal to or larger than ul- DataSplitTh reshold : submit the PDCP PDU to either the primary path or secondary path;

■ else: submit the PDCP PDU to the primary path;

[0376] When submitting a PDCP PDU to lower layer, the transmitting PDCP entity may:

- if the transmitting PDCP entity is associated with at least two RLC entities: o if the PDCP duplication is activated for the RB:

■ if the PDCP PDU is a PDCP Data PDU: duplicate the PDCP Data PDU and submit the PDCP Data PDU to the associated RLC entities activated for PDCP duplication;

■ else: submit the PDCP Control PDU to the primary RLC entity;

[0377] When submitting a PDCP PDU to lower layer, the transmitting PDCP entity may: (e.g., the PDCP duplication is deactivated for the RB and/or the RB is a Dual Active Protocol Stack (DAPS) bearer):

- if the split secondary RLC entity is configured; and/or if the total amount of PDCP data volume and RLC data volume pending for initial transmission in the primary RLC entity and the split secondary RLC entity is equal to or larger than ul-DataSplitThreshold: submit the PDCP PDU to either the primary RLC entity or the split secondary RLC entity;

- else, if the transmitting PDCP entity is associated with the DAPS bearer: o if the uplink data switching has not been requested: submit the PDCP PDU to the RLC entity associated with the source cell; o else:

■ if the PDCP PDU is a PDCP Data PDU: submit the PDCP Data PDU to the RLC entity associated with the target cell;

■ else:

• if the PDCP Control PDU is associated with source cell: submit the PDCP Control PDU to the RLC entity associated with the source cell;

• else: submit the PDCP Control PDU to the RLC entity associated with the target cell; else: submit the PDCP PDU to the primary RLC entity.

[0378] If the transmitting PDCP entity is associated with two RLC entities, or with one or more RLC entities and either an SRAP entity or the N3C, the UE may minimize the amount of PDCP PDUs submitted to lower layers before receiving request from lower layers and minimize the PDCP SN gap between PDCP PDUs submitted to two associated RLC entities, or to the RLC entity and either the SRAP entity or the N3C, to minimize PDCP reordering delay in the receiving PDCP entity. [0379] Multi-modal Data: Multi-modal Data may be defined to describe the input data from different kinds of devices/sensors or the output data to different kinds of destinations (e.g. one or more UEs) required for the same task or application. Multi-modal Data consists of more than one Single-modal Data, and there is strong dependency among each Single-modal Data. Single-modal Data can be seen as one type of data.

[0380] Data Burst may be a set of multiple PDUs generated and sent by the application in a short period of time. A Data Burst may be composed by one or multiple PDU Sets.

[0381] PDU Set may be composed of one or more PDUs carrying the payload of one unit of information generated at the application level (e.g., a frame or video slice for XR Services). In some implementations all PDUs in a PDU Set are needed by the application layer to use the corresponding unit of information. In other implementations, the application layer may still recover parts all or of the information unit, when some PDUs are missing.

[0382] PDU Set Error Rate (PSER) may define an upper bound for a rate of non-congestion related PDU Set losses between RAN and the UE. A PDU set may be considered as successfully delivered only when all PDUs of a PDU Set are delivered successfully, and if the PSER is available, the usage of PSER supersedes the usage of PER.

[0383] PDU Set Delay Budget (PSDB) may define time between reception of the first PDU (at the UPF in DL, at the UE in UL) and the successful delivery of the last arrived PDU of a PDU Set (at the UE in DL, at the UPF in UL). PSDB may be an optional parameter and when provided, the PSDB supersedes the PDB.

[0384] PDU Set Integrated Handling Indication (PSI HI) may indicate whether all PDUs of the PDU Set are needed for the usage of PDU Set by application layer.

[0385] PDU Set Importance (PSI) may identify the relative importance of a PDU Set compared to other PDU Sets within a QoS Flow. RAN may use it for PDU Set level packet discarding in presence of congestion.

[0386] Extended Reality (XR) may be referred to real-and-virtual combined environments and human-machine interactions generated by computer technology and wearables. XR may be an umbrella term for different types of realities:

- Virtual reality (VR) may be a rendered version of a delivered visual and audio scene. The rendering may be designed to mimic the visual and audio sensory stimuli of the real world as naturally as possible to an observer or user as they move within the limits defined by the application. Virtual reality usually, but not necessarily, requires a user to wear a head mounted display (HMD), to completely replace the user's field of view with a simulated visual component, and to wear headphones, to provide the user with the accompanying audio. Some form of head and motion tracking of the user in VR is usually also necessary to allow the simulated visual and audio components to be updated in order to ensure that, from the user's perspective, items and sound sources remain consistent with the user's movements.

- Augmented reality (AR) may be when a user is provided with additional information or artificially generated items or content overlaid upon their current environment. Such additional information or content will usually be visual and/or audible and their observation of their current environment may be direct, with no intermediate sensing, processing and rendering, or indirect, where their perception of their environment is relayed via sensors and may be enhanced or processed.

- Mixed reality (MR) may be an advanced form of AR where some virtual elements are inserted into the physical scene with the intent to provide the illusion that these elements are part of the real scene.

[0387] The present application may use the acronym XR throughout to refer to equipment, applications and functions used for VR, AR and MR. Examples include, but are not limited to HMDs for VR, optical see-through glasses and camera see-through HMDs for AR and MR and mobile devices with positional tracking and camera. They may offer some degree of spatial tracking and the spatial tracking results in an interaction to view some form of virtual content. [0388] Many of the XR use cases may be characterized by quasi-periodic traffic (with possible jitter) with high data rate in DL (i.e., video steam) combined with the frequent UL (i.e., pose/control update) and/or UL video stream. Both DL and UL traffic are also characterized by relatively strict packet delay budget (PDB). Hence, there is a need to study and potentially specify possible solutions to better support such challenging services, i.e., by better matching the noninteger periodicity of traffic, such as 60/90/120 frames per second to the NR signaling.

[0389] Many of the end user XR devices are expected to be mobile and of small-scale, thus having limited battery power resources. Therefore, additional power enhancements may be needed to reduce the overall UE power consumption when running XR services and thus extend the effective UE battery lifetime. From the Release 17 Study Item on “XR evaluations” it is identified that the current DRX configurations do not fit well for (i) the non-integer XR traffic periodicity, (ii) variable XR data rate and (iii) quasi-periodic XR periodicity, hence enhancements would be beneficial in this area.

[0390] The set of anticipated XR services has a certain variety and characteristics of the data streams (e.g. , video) may change “on-the-fly”, while the services are running over NR. Therefore, additional information on the running services from higher layers may be beneficial to facilitate informed choices of radio parameters.

[0391] XR content may be represented in different formats, e.g. panoramas or spheres depending on the capabilities of the capture systems. Since modern video coding standards are not designed to handle spherical content, projection is used for conversion of a spherical (or 360°) video into a two-dimensional rectangular video before the encoding stage. After projection, the obtained two-dimensional rectangular image can be partitioned into regions (e.g. front, right, left, back, top, bottom) that can be rearranged to generate "packed" frames to increase coding efficiency or viewport dependent stream arrangement.

[0392] The frame rate for XR video varies from 15 frames per second up to 90 or even 120 frames per second, with a typical minimum of 60 for VR. The latency of action of the angular or rotational vestibu lo-ocular reflex is known to be of the order of 10 ms or in a range from 7-15 milliseconds and it seems reasonable that this should represent a performance goal for XR systems. This results in a motion-to-photon latency of less than 20 milliseconds, with 10ms being given as a goal. Regarding the bit rates, between 10 and 200Mbps can be expected forXR depending on frame rate, resolution and codec efficiency. [0393] For Audio, it can be distinguished as channel-based and object-based representations:

- Channel-based representation using multiple microphones to capture sounds from different directions and post-processing techniques are well known in the industry, as they have been the standard for decades.

- Object-based representations represent a complex auditory scene as a collection of single audio elements, each comprising an audio waveform and a set of associated parameters or metadata. The metadata embody the artistic intent by specifying the transformation of each of the audio elements to playback by the final reproduction system. Sound objects generally use monophonic audio tracks that have been recorded or synthesized through a process of sound design. These sound elements can be further manipulated, so as to be positioned in a horizontal plane around the listener, or in full three-dimensional space using positional metadata.

[0394] Due to the relatively slower speed of sound compared to that of light, it is natural that users are more accustomed to, and therefore tolerant of, sound being relatively delayed with respect to the video component than sound being relatively in advance of the video component. Recent studies have led to recommendations of an accuracy of between 15 ms (audio delayed) and 5 ms (audio advanced) for the synchronization, with recommended absolute limits of 60 ms (audio delayed) and 40 ms (audio advanced) for broadcast video.

[0395] To maintain a reliable registration of the virtual world with the real world, as well as to ensure accurate tracking of the XR Viewer pose, XR applications require highly accurate, low-latency tracking of the device at about 1 kHz sampling frequency. The size of a XR Viewer Pose associated to time, typically results in packets of size in the range of 30-100 bytes, such that the generated data is around several hundred kbit/s if delivered over the network with latency requirements in the range of 10-20ms.

[0396] Repeatedly providing the XR Viewer Pose for the same display time may not necessarily return the same result (the prediction gets increasingly accurate as the information is closer to the time when a prediction is made) and there is a trade-off between providing several XR Viewer Pose for a display time and using the same XR Viewer Pose for several consecutive display times. However, it can be assumed that sending one XR Viewer Pose aligned with the frame rate of the rendered video may be sufficient, for example at 60fps.

[0397] Pose information has to be delivered with ultra-high reliability, therefore, similar performance as URLLO is expected, e.g., packet loss rate may be lower than 10E-4 for uplink sensor data.

[0398] XR-Awareness relies on QoS flows, PDU Sets, Data Bursts and traffic assistance information. PDU Set QoS Parameters may be provided by the SMF to the g N B as part of the QoS profile of the QoS flow:

- PDU Set Delay Budget (PSDB): upper bound for the duration between the reception time of the first PDU (at the UPF for DL, at the UE for UL) and the time when all PDUs of a PDU Set have been successfully received (at the UE in DL, at the UPF in UL). A QoS Flow is associated with only one PSDB, and when available, it applies to both DL and UL and supersedes the PDB of the QoS flow. - PDU Set Error Rate (PSER): upper bound for a rate of non-congestion related PDU Set losses between RAN and the UE. A QoS Flow is associated with only one PSER, and when available, it applies to both DL and UL and supersedes the PER of the QoS flow.

- A PDU set may be considered as successfully delivered only when all PDUs of a PDU Set are delivered successfully.

- PDU Set Integrated Handling Information (PSI HI): indicates whether all PDUs of the PDU Set are needed for the usage of PDU Set by application layer.

- The PDU Set QoS parameters may be common for all PDU Sets within a QoS flow.

[0399] UPF may identify PDUs that belong to PDU Sets, and may determine the following PDU Set Information which it sends to the gNB in the General Packet Radio System Tunnelling Protocol User Plane (GTP-U) header:

- PDU Set Sequence Number;

- Indication of End PDU of the PDU Set;

- PDU Sequence Number within a PDU Set;

- PDU Set Size in bytes;

- PDU Set Importance (PSI), which identifies the relative importance of a PDU Set compared to other PDU Sets within the same QoS Flow.

[0400] The following traffic assistance information may be provided by 5GC to the gNB:

- Via Time Sensitive Communication Assistance Indication (TSCAI): o UL and/or DL Periodicity; o N6 Jitter Information associated with the DL Periodicity.

- Indication of End of Data Burst in the GPRS Tunnelling Protocol-User Plan (GTP-U) header of the last PDU in downlink.

[0401] In the uplink, the UE may need to be able to identify PDU Sets and Data Bursts dynamically, including PSI. [0402] When a certain number of PDUs of a PDU Set are known to be required by the application layer to use the corresponding unit of information (for instance due to the absence or limitations of error concealment techniques, the PSIHI is set for a QoS flow, as soon as the number of one PDUs of a PDU set is known to be lost exceeds this number, the remaining PDUs of that PDU Set may be considered as no longer needed by the application and may be subject to discard operation of data.

[0403] Most XR video frame rates (15, 30, 45, 60, 72, 90 and 120 fps) may correspond to periodicities that are not an integer (66.66, 33.33, 22.22, 16.66, 13.88, 11.11 and 8.33 ms respectively). The gNB may configure a DRX cycle expressed in rational numbers so that the DRX cycle matches those periodicities, e.g. , for the traffic with a frame rate of 60 fps, the network may configure the UE with a DRX cycle of 50/3 ms.

[0404] Configured grants may be configured without the need for the UE to monitor possible UL retransmissions, thus increasing the number of power saving opportunities for the UE. [0405] The following enhancements for configured grant based transmission may be recommended:

- Support of multiple CG PUSCH transmission occasions within a single period of a CG configuration Indication of unused CG PUSCH occasion(s) of a CG configuration with Uplink Control;

- Information multiplexed in CG PUSCH transmission of the CG configuration.

[0406] In order to enhance the scheduling of uplink resources for XR, the following improvements are introduced:

- One additional buffer size table to reduce the quantization errors in BSR reporting (e.g. for high bit rates): o Whether, for an LCG, the new table can be used in addition to the regular one is configured by the gNB; o When the new table is configured for an LCG, it is used whenever the amount of the buffered data of that LCG is within the range of the new table, otherwise the regular table is used.

- Delay Status Report (DSR) of buffered data via a dedicated MAC CE: o Triggered for an LCG when the remaining time before discard of any buffered PDCP SDU goes below a configured threshold (threshold configured per LCG by the gNB); o When triggered for an LCG, reports the amount of data buffered with a remaining time before discard below the configured threshold, together with the shortest remaining time of any PDCP SDU buffered.

- Reporting of uplink assistance information (jitter range, burst arrival time, UL data burst periodicity) per QoS flow by the UE via UE Assistance Information.

[0407] When the PSIHI is set for a QoS flow, as soon as one PDU of a PDU set is known to be lost, the remaining PDUs of that PDU Set can be considered as no longer needed by the application and may be subject to discard operation at the transmitter to free up radio resources. In uplink, the UE may be configured with PDU Set based discard operation for a specific DRB. When configured, the UE discards all packets in a PDU set when one PDU belonging to this PDU set is discarded, e.g. based on discard timer expiry. In case of congestion, the PSI may be used for PDU set discarding. In uplink, dedicated signaling is used to trigger discard mechanism based on PSI. How SDUs are identified as low importance may be determined by UE. When a PDU Set Importance (PSI) is available, it may be used to classify the PDCP SDUs of a PDU Set.

[0408] The network activates and deactivates PSI-based SDU discard by sending the PSI-Based SDU Discard Activation/Deactivation MAC CE. The PSI-based SDU discard is initially deactivated upon (re-)configuration by upper layers and after reconfiguration with sync.

[0409] The MAC entity may for each DRB configured with PSI-based SDU discard:

- if a PSI-Based SDU Discard Activation/Deactivation MAC CE is received activating the PSI-based SDU discard for the DRB: indicate the activation of the PSI-based SDU discard for the DRB to upper layers;

- if a PSI-Based SDU Discard Activation/Deactivation MAC CE is received deactivating the PSI-based SDU discard for the DRB: indicate the deactivation of the PSI-based SDU discard for the DRB to upper layers. [0410] The PSI-Based SDU Discard Activation/Deactivation MAC CE may be identified by MAC subheader with an one-octet eLCID. It has a fixed size and consists of one octet defined as follows: Di: This field may indicate the activation/deactivation status of the PSI-based SDU discard of DRB i, where i is the ascending order of the DRB ID among the DRBs configured with PSI-based SDU discard. The Di field set to 1 indicates that the PSI-based SDU discard shall be activated for DRB i. The Di field set to 0 indicates that the PSI-based SDU discard shall be deactivated for DRB i.

[0411] FIG. 17 illustrates an example as per an aspect of an embodiment of the present disclosure.

[0412] As illustrated in FIG. 17, a data generated by an application is delivered from a sender to a receiver. The unit of data generated by the application may be an application data unit (ADU). The ADU may comprise, for example, a picture file, a video frame, text file and so on. The ADU may, for example, be generated and/or created by a first instance of a particular application, for use and/or enjoyment by a second instance of the application, or for processing by an application server of the application. To reliably deliver the ADU and/or to process the ADU efficiently, the ADU may be divided into one or more smaller units. For example, the one or more smaller units may be one or more protocol data units (PDUs). One or more first PDUs (e.g. , PDU 1 , PDU 2) for a first ADU may be of a first PDU set (e.g., PDU set 1). In an example, the first ADU may be segmented to (constructed into) the one or more first PDUs. The first PDU set may comprise the one or more first PDUs. One or more second PDUs (e.g., PDU 3, PDU 4) for a second ADU may be of a second PDU set (e.g., PDU set 2). In an example, the second ADU may be segmented into the one or more second PDUs. The second PDU set may comprise the one or more second PDUs.

[0413] In an example, the application may deliver the one or more first PDUs and/or the one or more second PDUs to an SDAP/PDCP entity (e.g., a SDAP entity, a PDCP entity, and/or both a SDAP entity and a PDCP entity). The first PDU (e.g., PDU 1) may be delivered from the application to the SDAP/PDCP entity. In the SDAP/PDCP entity, the first PDU may correspond to (or be associated with) a first SDAP SDU, a first SDAP PDU, a first PDCP SDU, and/or a first PDCP PDU. The second PDU (e.g., PDU 2) may be delivered from the application to the SDAP/PDCP entity. In the SDAP/PDCP entity, the second PDU may correspond to a second SDAP SDU, a second SDAP PDU, a second PDCP SDU, and/or a second PDCP PDU. Similarly, the PDU 3 may be a third PDCP SDU (e.g., PDCP SDU 3) and/or the PDU 4 may be a fourth PDCP SDU (e.g., PDCP SDU 4).

[0414] In an example, one or more PDCP PDUs (e.g., PDCP PDU 1 , 2, 3, 4) may be delivered from the SDAP/PDCP entity to a RLC entity. The RLC layer may provide functionality of forwarding the one or more PDCP PDUs, for example, over a particular interface, from one node to another, using a MAC entity and/or a PHY entity.

[0415] In an example, the application of the sender may generate one or more PDU sets. For example, the one or more PDU sets comprise the first PDU set and/or the second PDU set. The application in the sender may deliver the one or more PDU sets to the SDAP/PDCP entity of the sender. The SDAP/PDCP entity may classify the one or more PDUs of the one or more PDU sets, may apply header compression to the one or more PDUs to reduce size of headers of the one or more PDUs, may apply ciphering to the one or more PDUs to provide security, and/or may generate one or more PDCP PDUs. The one or more PDCP PDUs may comprise the one or more PDUs.

[0416] In an example, the SDAP/PDCP entity of the sender delivers the generated one or more PDCP PDUs to the RLC entity of the sender. The RLC entity may be responsible for transferring data between a UE and a NG-RAN, using the MAC entity and/or the PHY entity. For example, the RLC entity of the sender may process and generate one or more RLC PDUs for the one or more PDCP PDUs (e.g., RLC SDUs) delivered from the PDCP/SDAP entity. For example, the RLC entity may generate a first RLC PDU from the first PDCP PDU (e.g., the first RLC SDU) and/or the RLC entity may generate a second RLC PDU from the second PDCP PDU (e.g., the second RLC SDU). If resources allocated for transmission is not enough to transmit an entire RLC SDU via the resources, one or more RLC PDUs may comprise at least a portion of the RLC SDU. For example, the portion of the RLC SDU may be a RLC SDU segment. For example, a RLC PDU X associated with the RLC SDU Y may comprise at least one of a first portion of the RLC SDU Y (e.g., the first RLC SDU segment) or the (entire) RLC SDU Y. For the RLC SDU Y, one or more RLC SDU segments may be associated (generated, used, constructed). One or more RLC PDUs may comprise at least one of one or more RLC SDU segments, one or more RLC SDUs, one or more RLC control PDUs (e.g., RLC status PDU). The one or more RLC PDUs comprising at least one of a RLC SDU segment or a RLC SDU may be one or more AM RLC PDUs.

[0417] In an example, the one or more RLC PDUs generated by the RLC entity of the sender may be delivered to the MAC entity of the sender. The MAC entity of the sender may send the one or more RLC PDUs to a MAC entity of the receiver. The MAC entity of the receiver may deliver the one or more RLC PDUs to a RLC entity of the receiver. For example, the RLC entity of the receiver may receive the one or more RLC PDUs (e.g., RLC PDU 1, 2, 3, 4) from the RLC entity of the sender via the MAC entity of the receiver. The RLC entity of the receiver may recover (reassemble) the one or more RLC SDUs (e.g., PDCP PDUs) using the one or more RLC PDUs. The RLC entity of the receiver may deliver one or more recovered PDCP PDUs to a PDCP entity of the receiver. The PDCP entity of the receiver may process the one or more received PDCP PDUs, and/or may recover one or more PDUs (e.g., one or more PDCP SDUs) from the one or more PDCP PDUs. To recover a PDCP SDU from a PDCP PDU may be that the PDCP SDU is extracted from the PDCP PDU.

[0418] FIG. 18 illustrates an example as per an aspect of an embodiment of the present disclosure.

[0419] In an example, for one or more RLC SDUs (e.g., RLC SDU 0, RLC SDU 1 , and so on) received from an application (or a PDCP entity), a RLC entity (and/or via a MAC entity) may transmit one or more RLC PDUs. When delivery of a RLC SDU from a sender to a receiver fails, the RLC entity (of the sender) may perform re-transmission of the RLC SDU. For example, if the RLC entity of the sender receives from the RLC entity of the receiver, a negative acknowledgement for the RLC SDU, the RLC entity of the sender may perform re-transmission of the RLC SDU. [0420] In an example, before time t=tO, the RLC entity of the sender may receive from the PDCP entity of the sender, a RLC SDU 0. The RLC entity may generate (compose, construct, assemble) one or more RLC PDUs using the RLC S DU 0. For example, at the time t=tO, the RLC entity generates a RLC PDU 0 comprising the RLC SDU 0 and/or transmits the RLC PDU 0.

[0421] In an example, the transmission of the RLC PDU 0 may fail and/or the receiver may not receive the RLC PDU 0. At the time t=t1 , the receiver may determine that the receiver fails to receive the RLC PDU 0 and/or the RLC SDU 0. In response to the determination, at time t=t3, the receiver may transmit a RLC Status report (e.g., RLC status PDU, RLC control PDU) to the sender. For example, the RLC Status report may comprise an indication that the RLC SDU 0 is not received and/or a negative acknowledgement (e.g., NACK) for the RLC SDU 0.

[0422] In an example, the transmission of the RLC Status report from the receiver to the sender may fail. For example, the sender may fail to receive the RLC Status report. Because the sender does not receive the RLC status report and/or because the sender does not receive an indication that the receiver does not receive the RLC SDU 0, the sender may not perform retransmission of the RLC SDU 0.

[0423] In an example, at t=t4, a time limit for delivery of the RLC SDU 0 may expire (elapse, stop). For example, the time limit may be associated with a time boundary until which a content in the RLC SDU is useful to the receiver (or a receiving entity, an application of the other end). For example, in case of a voice call application, if a packet comprising a voice data arrives to a receiver 1 hours later, a user at the receiver may not be able to use the voice data.

[0424] In an example, t=t5, the receiver may determine to transmit a second RLC Status report. For example, the second RLC Status report may comprise an indication that the RLC SDU 0 is not received and/or the negative acknowledgement for the RLC SDU 0.

[0425] In an example, the sender may receive the second RLC Status report. Because the second RLC Status report indicates the negative acknowledgement for the RLC SDU 0, the sender may retransmit the RLC SDU 0 to the receiver, at t=t6. The receiver may receive the RLC SDU 0. As shown in this example, retransmission of the RLC SDU 0, based on receiving the negative acknowledgement, may help to increase reliability of data delivery (e.g., the RLC SDU 0 is guaranteed to be delivered from the sender to the receiver). The retransmission may help in avoiding loss of a data from the sender to the receiver. However, as shown in the example of FIG. 18, the existing technologies may cause unnecessary use of radio resource, because the retransmission of the RLC SDU 0 occurs after a time boundary during which the RLC SDU 0 is useful to the application or to the receiver. For example, in case of XR (extended Reality, e.g., AR, MR) application, more than 1GB data is generated per second and a packet delay budget (PDB) is less than 20 ms. For this type of application, transmission of data packet after the PDB may be frequent and lead to loss of radio resources. On the other hand, for this type of application, even small loss of data packet may impact on user experience (e.g., dizziness).

[0426] Example embodiments of the present disclosure improve system efficiency by triggering retransmission based on time information associated with a packet. This may help unnecessary delay of transmission of the packet. In another example, a UE may determine whether to perform retransmission of the packet, based on a time of last transmission of the packet. This may help reducing unnecessary retransmission. In another example, a signalling is enhanced to configure a UE with information in managing retransmission by an RLC entity. This may help for the UE to determine when to perform retransmission of the packet, after determining to retransmit. In another example, the UE may determine whether remaining delivery time of packet is less than a threshold. This may help in avoiding delivery of the packet which may not be useful to a receiver. In another example, the UE may determine selectively one or more segments of the packets for retransmission. This may help in avoiding radio resource shortage. In another example, the UE may perform retransmission of a delay critical packet based on a timer expiry. This may help in reducing transmission delay and in wasting radio resource. In another example, the UE may use multiple logical channels for transmission of a delay critical packets. This may help in increasing reliability of data delivery.

[0427] In the specification, the term “network system” may be interpreted as, or may refer to, a communication system, and/or a generation of the communication system. For example, one or more network systems may comprise an EPS, a 5GS. For example, the first network system may be the EPS. The EPS may comprise of one or more UEs, one or more eNB, one or more en-gNBs, one or more EPCs. The one or more EPCs may comprise a MME, a SGW, a PGW, and/or the like. For example, the second network system may be the 5GS. The 5GS may comprise of one or more UEs, one or more gNB, one or more ng-eNBs, one or more 5G core networks. The one or more 5G core networks may comprise an AMF, a SMF, a PCF, and/or the like. For example, a 6th generation (6G) system may be the 6GS. The 6GS may comprise of one or more UEs, one or more 6G-RAN, one or more gNBs, one or more 6G core networks.

[0428] In the specification, the term “5G System” may be interpreted as, or may refer to, a 3GPP system consisting of at least one of 5G access network (or NG-RAN), 5G core network and/or a UE.

[0429] In the specification, the term “EPS” may be interpreted as, or may refer to, a 3GPP system consisting of at least one of EPC, E-UTRAN and/or a UE.

[0430] In the specification, the term “network node” may be interpreted as, or may refer to, at least one of a core network node, an access node, a UE, the like, and/or a combination thereof. A network may comprise one or more network nodes.

[0431] In the specification, the term “core network node” may be interpreted as, or may refer to, a core network device, which may comprise at least one of an AMF, a SMF, a NSSF, a UPF, a NRF a UDM, a PCF, a SoR-AF, an AF, an DDNMF, an MB-SMF, an MB-UPF, a MME, a SGW, a PGW, a SMF+PGW-C, a SMF^GW-U, a UDM+HSS and/or the like. The core network node may be a 5G core network node, a 6G core network node, a 4G core network node, the likes, and/or a combination thereof.

[0432] In the specification, the term “5G core network” may be interpreted as, or may refer to, a core network connecting to a 5G access network. This may be 5G core (5GC).

[0433] In the specification, the term “RAT type” may be interpreted as, or may refer to, identifying the transmission technology used in the access network for 3GPP accesses and/or for non-3GPP accesses. For example, RAT type for 3GPP access may comprise at least one of NR, NB-IOT, E-UTRA, and/or the like. For example, RAT type for non- 3GPP access may comprise at least one of untrusted non-3GPP, trusted non-3GPP, trusted IEEE 802.11 non-3GPP access, Wireline, Wireline-Cable, Wireline-BBF, WiFi, etc.

[0434] In the specification, the term “3GPP RAT” may be interpreted as, or may refer to, a radio access technology based on 3rd generation partnership (3GPP) project. For example, this may comprise at least one of a NR, a E-UTRA, UTRA, GSM, 6GR (6G radio), the like, and/or a combination thereof.

[0435] In the specification, the term “N3GPP RAT” may be interpreted as, or may refer to, a radio access technology not based on 3rd generation partnership project. This may be an access technology not developed by 3GPP. For example, this may comprise a WiFi, trusted WiFi, non-trusted WiFi, fixed access, wireline broadband, the like, and/or a combination thereof.

[0436] In the specification, the term “5G access network” may be interpreted as, or may refer to, an access network comprising at least one of a NG-RAN and/or non-3GPP RAN, and connecting to a 5G core network.

[0437] In the specification, the term “3GPP RAN” may be interpreted as, or may refer to, a radio access network using 3GPP RAT. For example, this may comprise at least one of a gNB, an eNB, a ng-eNB, an en-gNB, the like, and/or a combination thereof. For example, this may be at least one of an E-UTRAN, NG-RAN, 6G-RAN (6th generation RAN), the like, and/or a combination thereof. The 3GPP RAN may be 3GPP access node.

[0438] In the specification, the term “NG-RAN” may be interpreted as, or may refer to, a base station, which may comprise at least one of a gNB, a ng-eNB, a relay node, a base station central unit (e.g., gNB-CU), a base station distributed unit (e.g., gNB-DU), and/or the like. This may be a radio access network that connects to 5G0, supporting at least one of NR, E-UTRA, and/or a combination thereof.

[0439] In the specification, the term “E-UTRAN” may be interpreted as, or may refer to, a base station, which may comprise at least one of an eNB, an en-gNB, and/or the like. This may be a radio access network that connects to evolved packet core (EPC), supporting at least one of NR, E-UTRA, and/or a combination thereof.

[0440] In the specification, the term “mobility management node” may be interpreted as, or may refer to, a function and/or a node performing mobility management for a UE. For example, mobility management may be at least one of management of registration status, management of context, management of authorization, management of registration area, management of paging, and/or the like. For example, the mobility management node may comprise at least one of a MME, AMF, and/or the like.

[0441] In the specification, a term “procedure” may be interpreted as, or may refer to, comprising sending by a first node to a second node a first message, receiving by the second node from the first node the first message, sending by the second node to the first node a second message, and/or receiving by the first node from the second node the second message. The first node may be one or more first network nodes, and the second node may be a one or more second network nodes. The procedure may comprise a registration procedure, a deregistration procedure, a service request procedure, a notification procedure, a PDU session establishment procedure, a PDU session modification procedure, a UE configuration update procedure, and/or the like. [0442] In the specification, a term “NAS message” may be interpreted as, or may refer to, a message exchanged between a UE and a core network node. The NAS message may be exchanged via a 3GPP access and/or via a N3GPP access. The NAS message may comprise a MM (mobility management) message, a SM (session management) message, and/or the like. The MM message may comprise a registration request message, a registration accept message, a registration reject message, a UE configuration update message, a UL NAS transport message, a DL NAS transport message, a deregistration message, a service request message, a service accept message, a service reject message, a PDU session establishment request message, a PDU session establishment accept message, a PDU session establishment reject message, a PDU session modification request message, a PDU session modification accept message, a PDU session modification reject message, a PDU session modification command message, a PDU session release request message, a PDU session release command message, and/or the like.

[0443] In an example, a timer may begin running once it is started and continue running until it is stopped or until it expires. A timer may be started if it is not running or restarted if it is running. A timer may be associated with a value (e.g. the timer may be started or restarted from a value or may be started from zero and expire once it reaches the value). The duration of a timer may not be updated until the timer is stopped or expires (e.g., due to change of the value). A timer may be used to measure a time period/window for a process. When the specification refers to an implementation and procedure related to one or more timers, it will be understood that there are multiple ways to implement the one or more timers. For example, it will be understood that one or more of the multiple ways to implement a timer may be used to measure a time period/window for the procedure. For example, a network slice inactivity window timer (e.g., a NS UE monitoring timer, a NS PDU monitoring timer) may be used for measuring a window of time for measuring the network slice inactivity. In an example, instead of starting and expiry of a network slice inactivity window timer, the time difference between two time stamps may be used. When a timer is restarted, a process for measurement of time window may be restarted. Other example implementations may be provided to restart a measurement of a time window.

[0444] In an example, indication (e.g., indicate, indicating) may be achieved in various ways. For example, a first indication may be done by including a first field in a first signalling (e.g., a message). Alternatively and/or additional, a second indication may be done by not including the first field in the first signalling. For example, if a first message comprises the first field (e.g., used/ assigned for the first indication, e.g., field A), the first indication (e.g., a timer is used) may be done (e.g., achieved, delivered from a sender to a receiver). For example, if the first field in the first message is set to a value A, a third indication (e.g., timer value is value A) may be done. For example, if the first message does not comprise the first field, the second indication (e.g., timer is not used) may be done. In another example, a fourth indication (e.g., a UE is allowed for action 0) may be done by sending a second signalling (e.g., a message whose name comprises 'O’ and/or ‘accept’). Alternatively and/or additionally, a fifth indication (e.g., a UE is not allowed for action C) may be done by not sending the second signalling (e.g., a message, a field (e.g., allowed bit)). For example, the sender can indicate A, by sending a message A1 comprising an indicator (e.g., an information element) indicating A and/or by sending a message A2. For example, the message A2 may be used only to indicate A and/or the message A2 itself may indicate the A. For example, when a first entity indicates to a second entity about first something, the first entity may send to the second entity, an indicator (e.g., an information element) indicating the first something, and/or may send to the second entity, a message comprising the indicator and/or may send a first dedicated message for the first something. In other example, when a first entity does not indicate to a second entity about second something, the first entity may not send to the second entity, a first indicator (e.g., an information element) indicating the second something, may not send to the second entity, a message comprising the first indicator, and/or may send to the second entity, a second indicator indicating that the second something does not apply, and/or may send a message not comprising the first indicator, and/or may send to the second entity, a second dedicated message for indicating the second something. In another example, not sending any message may be interpreted as an indication.

[0445] In the specification, “protocol entity” may be interpreted, or may refer to, as an entity performing a set of specific functions related to a wireless access (e.g., LTE access, NR access) and/or a wireline access (e.g., Ethernet) and/or communication (e.g., TCP, IP). In an example, an entity may be interpreted as a protocol entity. In an example, the protocol entity of LTE and/or NR may be at least one of a SDAP entity, a PDCP entity, a RLC entity, a MAC entity and/or a PHY entity. In an example, a layer (e.g., a SDAP layer, a PDCP layer, a RLC layer, a MAC layer a PHY layer) may be interpreted as a protocol entity (e.g., SDAP entity, a PDCP entity, a RLC entity, a MAC entity, a PHY entity). [0446] In the specification, “service data unit” may be interpreted, or may refer to, as a unit of a data, received by a protocol entity. In the specification, a protocol data unit may be interpreted as a unit of a data, sent by a protocol entity. A protocol entity may receive one or more service data units (SDUs) from other protocol entity, and the protocol entity may send one or more protocol service data units (PDUs) to another protocol entity of same host or another host. A PDU in a PDU set may corresponds to a PDCP SDU. For example, a PDCP entity may receive one or more PDCP SDUs from a higher entity and the PDCP entity may send one or more PDCP PDUs to a lower entity (e.g., an RLC entity). The lower entity (e.g., an RLC entity) may receive one or more SDUs (e.g., RLC SDUs) from the higher layer. The one or more SDUs received by the lower layer may be same as the one or more PDUs sent by the higher layer. In the specification, a PDCP SDU may be a PDU. For example, PDU 1 and PDU 2 may be generated by an application of a sender (a UE or in an application server). The PDU 1 and the PDU 2 may be delivered to a sending SDAP entity as a SDAP SDU 1 and 1 SDAP SDU 2. The sending SDAP entity may construct a SDAP PDU 1 from a SDAP header 1 and the SDAP SDU 1. The sending SDAP entity may deliver the SDAP PDU 1 to a sending PDCP entity. The sending PDCP entity may receive the SDAP PDU 1 as a PDCP SDU 1. The sending PDCP entity may construct a PDCP PDU 1 from a PDCP header 1 and the PDCP SDU 1. The PDCP SDU 1 may be a PDU of a PDU set. The sending PDCP entity may deliver the PDCP PDU 1 to a sending RLC entity. The sending RLC entity may receive the PDCP PDU 1 as a RLC SDU 1. The sending RLC entity may construct a RLC PDU 1 from a RLC header 1 and the RLC SDU 1. The sending RLC entity may deliver the RLC PDU 1 to a receiving RLC entity via a MAC/PHY entity. The receiving RLC entity may receive the RLC PDU 1. The receiving RLC entity may recover the RLC SDU 1 from the RLC PDU 1 and/or may deliver the RLC SDU 1 to a receiving PDCP entity. The receiving PDCP entity may receive the RLC SDU 1 as the PDCP PDU 1. The receiving PDCP entity may recover the PDCP SDU 1 from the PDCP PDU 1 and/or may deliver the PDCP SDU 1 to a receiving SDAP entity. The receiving SDAP entity may receive the PDCP SDU 1 as the SDAP PDU 1. For example, the RLC PDU may be a AMD PDU.

[0447] In the specification, the term “AF (application function)” may be interpreted as a AS (application server), which may host and/or run one or more applications.

[0448] In the specification, the term “PDU set” may be interpreted as, or may refer to, one or more PDUs carrying a payload of one unit of information generated at an application layer level (e.g., a frame or video slice). In some implementations all PDUs in a PDU Set may be needed by the application layer to use the corresponding unit of information. In other implementations, the application layer may be able to recover parts of the unit of information unit, when some PDUs in the PDU set are missing. A PDU in the PDU Set may correspond to a PDCP SDU. A PDU in the PDU Set may correspond to a packet of an ADU.

[0449] In the specification, the term “ADU” may be interpreted as, or may refer to, one unit of information. The unit of information may be exchanged among one or more hosts serving an application. In an example, an application (e.g., an internet browser, an instant messaging application, a video-player application, etc.) may be running on a first host (e.g., a smartphone, computer, application server, etc.) and the same application may be running on a second host (e.g., another smartphone, computer, application server, etc.). The application on a first host may generate one or more units (e.g., a picture file, a text message, etc.) of information. Each of the one or more units of information may comprises one or more PDUs, and/or the one or more PDUs for a unit of information may be a PDU set. The ADU may comprise one or more packets (e.g., PDUs)

[0450] In the specification, the term “header” may be interpreted as, or may refer to, a part in a PDU (or packet) which is not payload. The payload may comprise a user data, and/or an upper layer (entity) PDU. For example, the header may be and/or comprise one or more header fields. For example, the header may sometimes be interpreted as a header field and/or the header field may be interpreted as a header. For example, the header may be a RTP header, a RTP extension header, a FEO header, and/or the like. For example, a RTP header may comprise one or more header fields. A header fields may be a header field of the one or more header fields, one or more of the one or more header fields, and/or all header fields. The header field in the PDU may be set to a value. Based on the value of the header field, different behavior and/or different interpretations may be performed/ triggered by a receiver of the PDU.

[0451] In the specification, the term “delay-critical” may be interpreted as, or may refer to, remaining time being less than a threshold. For example, a packet delay budget of a packet may be X ms and the threshold (for delay-critical determination) may be Y ms. If the packet is generated at time T=Ta, the packet needs to be delivered to a peer until T=Ta +X. From a time T=Ta to a time T=Ta+X-Y, the packet may not be delay-critical and/or may be non-delay- critical. After a time T=Ta+X-Y, the packet may be delay-critical. The threshold may be threshold of a remaining time. For example, the remaining time may be a time remaining until discarding (delay budget) of the packet. In an example, different layer may have different threshold. For example, a PDCP entity may use a second threshold (e.g., remainingTimeThreshold), for determination of a delay critical PDCP SDU. For example, a RLC entity may use a first threshold (e.g., remainingTimeThresholdRLC, RLCremainingTimeThreshold), for determination of a delay critical RLC SDU. For example, due to internal processing, a first time when the PDCP entity receives from an application a first PDCP SDU may be different from a second time when the RLC entity receives from the PDCP entity, a first RLC SDU (associated with the PDCP SDU). In this case, separate determination by the RLC entity and the PDCP entity may help. In some case, to reduce use of computing resource, the PDCP entity may determine whether a PDCP SDU is delay critical or not, and may indicate this to the RLC entity.

[0452] In the specification, the term “positive acknowledgement” may be interpreted as, or may refer to, an indication of successful reception. For example, when a receiver receives a SDU X, the receiver may send a positive acknowledgement of the SDU X, to the sender. The positive acknowledgement may be ACK. For example, the positive acknowledgement of the SDU X may be indicated via a sequence number of the SDU X and/or via a bitmap of a RLC control PDU.

[0453] In the specification, the term “negative acknowledgement” may be interpreted as, or may refer to, an indication of unsuccessful reception. For example, when a receiver determines (detects) that the receiver fails to receive a SDU Y and/or that the SDU Y is not received, the receiver may send a negative acknowledgement of the SDU Y, to the sender. The negative acknowledgement may be NACK. For example, the negative acknowledgement of the SDU Y may be indicated via a sequence number of the SDU X and/or via a bitmap of a RLC control PDU.

[0454] In the specification, the term “non-acknowledgement” may be interpreted as, or may refer to, not receiving any of positive acknowledgment or negative acknowledgement. For example, if a receiver fails to determine (detect) whether the receiver fails to receive a SDU Z, the receiver may not send a negative acknowledgement of the SDU Z and may not send a positive acknowledgment of the SDU Z, to the sender. In this case, the sender may not be able to determine whether the transmission of the SDU Z is successful or not. In another example, if the negative acknowledgement of the SDU Z is not successfully delivered from the receiver to the sender, and/or if the positive acknowledgement of the SDU Z is not successfully delivered to the sender, the sender may not be able to determine whether the transmission of the SDU Z is successful or not. If the sender may not be able to determine whether the transmission of the SDU Z is successful or not, the SDU Z is non-acknowledged and/or the SDU Z is un-acknowledged. [0455] FIG. 19 illustrates an example as per an aspect of an embodiment of the present disclosure.

[0456] A sender (e.g., of a UE, a base station) may receive a data (e.g., a packet, a RLC SDU, a PDCP PDU) from an upper layer, at time T=T0. For example, a (transmitting) RLC entity of the sender may receive a RLC SDU from a (transmitting) PDCP entity of the sender. For example, a (transmitting) PDCP entity of the sender may receive a PDCP SDU from an application of the sender, the PDCP entity may generate a PDCP PDU from the PDCP SDU, and/or the PDCP entity may deliver the PDCP PDU (the RLC SDU) to the RLC entity. When the RLC entity receives the RLC SDU, the RLC entity may associate a sequence number (SN) with the RLC SDU. For example, the RLC entity may associate SN=0 to a RLC SDU 0, may associate SN=1 to a RLC SDU 1.

[0457] The RLC entity of the sender may send one or more RLC PDUs to a RLC entity of a receiver. The one or more RLC PDUs may comprise at least one of one or more RLC SDUs and/or one or more RLC SDU segments. Each of the one or more RLC PDUs may be successfully delivered to the receiver and/or may not be successfully delivered to the receiver. For example, the RLC entity of the sender may generate a first RLC PDU (associated with SN=1) using the first RLC SDU (associated with SN=1). The first RLC PDU may comprise at least one of the first RLC SDU (associated with SN=1) and/or a first RLC SDU segment (associated with SN=1) of the first RLC SDU. The first RLC PDU may comprise a field indicating a sequence number associated with the first RLC SDU (e.g., SN= 1 ) . For example, the first RLC SDU segment may comprise at least a portion of the first RLC SDU. The RLC entity of the sender may send (e.g., transmit) the first RLC PDU to the receiver, at time T=T1. The RLC entity of the receiver may fail to receive the first RLC PDU. For example, the RLC entity of the receiver may not be able to receive the first RLC PDU, e.g., due to radio channel condition.

[0458] The RLC entity (e.g., receiving RLC entity) of the receiver may determine whether to send a RLC status PDU (or RLC status report, RLC Control PDU) to the sender. For example, the RLC entity of the receiver may determine whether there is a missing RLC SDU and/or a missing RLC SDU segment. The missing RLC SDU may be a RLC SDU for which the receiver does not receive and/or the receiver fails to receive. The missing RLC SDU segment may be a RLC SDU segment for which the receiver does not receive and/or the receiver fails to receive. If the receiver determines that there is a missing RLC SDU and/or a missing RLC SDU segment, the receiver may send the RLC Status PDU, to the sender (e.g., the RLC entity of the sender). For example, the RLC status report may comprise a negative acknowledgement. For example, the negative acknowledgement may be a negative acknowledgement for SN= 1 (or for the first RLC SDU). In another example, if the receiver cannot determine whether there is a missing RLC SDU and/or a missing RLC SDU segment, the receiver may not send the RLC Status PDU, to the sender, unless the receiver receives a polling bit.

[0459] The RLC entity of the sender may receive the RLC Status PDU, at time T=T1 ’. Based on the RLC Status PDU (e.g., because the RLC Status PDU indicates the negative acknowledgement for SN=1 (RLC SDU associated with the SN=1)), the RLC entity of the sender may determine to retransmit the RLC SDU (associated with the SN=1). For example, the RLC entity of the send may transmit a second RLC PDU, at T=T2. For example, the second RLC PDU may comprise at least one of the first RLC SDU and/or the first RLC SDU segment. For example, the second RLC PDU may comprise a field (e.g., a sequence number field, SN field) set to SN=1.

[0460] The RLC entity of the sender may determine whether the first RLC SDU is delay-critical or not, whether a status of the first RLC SDU changes from non-delay-critical to delay-critical, and/or the like. For example, to determine whether the first RLC SDU is delay-critical or not, the RLC entity of the sender may determine (check, identify, compare) whether a remaining time of the first RLC SDU is less than (or equal to) a first value. For example, the first value may be at least one of a first threshold, a first RLC threshold, a first RLC remaining time threshold, and/or the like. For example, the remaining time may be calculated based on a timer (e.g., a fifth timer in the example of FIG. 21, discardTimer) for determining delay-critical. For example, the sender (and/or the RLC entity of the sender, and/or a PDCP entity of the sender) may start the timer with a time value when the sender receives a packet (e.g., a RLC SDU, a PDCP SDU) from the application of the sender. The remaining time may be a remaining time until expiry of the timer. For example, a first parameter may be the first value. For example, if the remaining time is larger than (or equal to) the first value, the sender may determine that the first RLC SDU is not delay critical. In another example, if the remaining time is less than (or equal to) the first value, the sender may determine that the first RLC SDU is delay critical.

[0461] The RLC entity of the sender may determine that the first RLC SDU becomes delay-critical, at time T=T3. For example, until T=T3, the RLC entity may determine that the first RLC SDU is non-delay-critical. For example, after time T=T3, the RLC entity may determine that the first RLC SDU is delay-critical.

[0462] In response to determining that the first RLC SDU is delay-critical, the RLC entity may determine when/whether to perform retransmission of the first RLC SDU. For example, the RLC entity may determine whether one or more conditions are met. For example, if the one or more conditions are met, the RLC entity may retransmit the first RLC SDU. For example, if the one or more conditions are not met, the RLC entity may not retransmit the first RLC SDU.

[0463] For example, the one or more conditions may comprise at least one of:

[0464] - a first condition that the first RLC SDU is (becomes) delay-critical. For example, the first parameter may be associated with the first condition.

[0465] - a second condition that at least first amount of time elapses since last retransmission of the first RLC SDU. [0466] - a third condition that at least second amount of time is left until discarding of the first RLC SDU. For example, this may indicate a (remaining) time until T5 (e.g., PDB of the first RLC SDU). For example, a fourth parameter may be associated with the third condition.

[0467] - a fourth condition that a timer prohibiting retransmission of the first RLC SDU is not running and/or that the timer prohibiting retransmission expires. For example, the fourth condition may be associated with a timer, a timer value.

[0468] - a fifth condition that the sender is configured to perform retransmission of a RLC SDU which is delay critical. For example, the sender (e.g., a UE) may receive from a base station, one or more configuration parameters (one or more parameters) indicating that the sender retransmits the RLC SDU, if the RLC SDU becomes delay-critical. For example, the fifth condition may be associated with a seventh parameter. For example, the seventh parameter may indicate whether retransmission of a delay critical RLC SDU is configured or not.

[0469] - a sixth condition that an uplink resource is available for transmission, for the RLC entity. For example, the RLC entity is indicated transmission opportunity by a lower layer (e.g., a MAC entity). [0470] The sender may determine one or more first conditions of the one or more conditions are met, at time T=T4. For example, if the one or more first conditions are met, the sender may retransmit a RLC SDU for which the one or more first conditions are met.

[0471] For example, the sender (e.g., the RLC entity of the sender) may determine that the first RLC SDU is delay- critical, that the first amount of time elapses since last (latest) retransmission of the first RLC SDU (or the first RLC SDU segment), that the remaining time (until discarding, or packet delay budget) of the RLC SDU is more than the at least second amount of the time, that the timer prohibiting retransmission of the first RLC SDU is not running (or expired), that the sender is configured for retransmission of the delay critical RLC SDU, and/or that the RLC entity is indicated transmission opportunity by the lower layer, the sender may determine to retransmit the first RLC SDU, at T=T4. For example, at T=T4, the sender may transmit a third RLC PDU comprising at least one of the first RLC SDU and/or the first RLC SDU segment.

[0472] In other example, the sender may determine one or more second conditions of the one or more conditions are met, at time T=T4. For example, if the one or more second conditions are met, the sender may not retransmit a RLC SDU for which the one or more second conditions are met.

[0473] For example, the sender (e.g., the RLC entity of the sender) may determine that the first RLC SDU is not delay-critical, that the first amount of time does not elapse since last (latest) retransmission of the first RLC SDU (or the first RLC SDU segment), that the remaining time (until discarding, or packet delay budget) of the RLC SDU is less than the at least second amount of the time, that the timer prohibiting retransmission of the first RLC SDU is running (or not expired), that the sender is not configured for retransmission of the delay critical RLC SDU, and/or that the RLC entity is not indicated transmission opportunity by the lower layer, the sender may determine not to retransmit the first RLC SDU, at T=T4.

[0474] In an example, in response to determining to retransmit the first RLC SDU and/or the first RLC SDU segment, the sender may place the first RLC SDU and/or the first RLC SDU segment, onto a RLC retransmission buffer.

[0475] Example embodiments of FIG. 19 may help in increasing reliability of data delivery from the sender to the receiver, while reducing unnecessary use of radio resource. For example, by checking the one or more conditions, the RLC entity may prevent unnecessary retransmission at T=T4, if the transmission at T=T2 is successful. For example, by checking the one or more conditions, the RLC entity may increase reliability, if the transmission at T=T2 is unsuccessful and/or if the sender does not receive a RLC status report until T=T4.

[0476] FIG. 20 illustrates an example as per an aspect of an embodiment of the present disclosure. In an example, a sender (e.g., a UE, a RLC entity of the sender) may use a timer to prohibit unnecessary retransmission of a RLC SDU (e.g., a delay-critical RLC SDU, or when a RLC SDU becomes delay-critical). For brevity, based on the other part of the present disclosure, redundant details will be omitted.

[0477] The sender (e.g., a UE, a base station, a RLC entity of the sender, a transmitting RLC entity of the sender) may receive a data (e.g., a packet, a RLC SDU, a PDCP PDU) from an upper layer (e.g., a PDCP entity of the sender, an application of the sender), at time T=T0. For example, the (transmitting) RLC entity of the sender may receive the RLC SDU from the (transmitting) PDCP entity of the sender. For example, the (transmitting) PDCP entity of the sender may receive the PDCP SDU from the application of the sender, the PDCP entity may generate the PDCP PDU from the PDCP SDU, and/or the PDCP entity may deliver the PDCP PDU (the RLC SDU, e.g., a RLC SDU 0, a RLC SDU 1 ) to the RLC entity. When the RLC entity receives the RLC SDU from the PDCP entity, the RLC entity may associate a sequence number (SN) with the RLC SDU. For example, the RLC entity may associate S N =0 to the RLC SDU 0 (corresponding to a PDCP PDU 0, associated with a PDCP SDU 0), may associate SN=1 to the RLC SDU 1 (corresponding to a PDCP PDU 1, associated with a PDCP SDU 1).

[0478] The RLC entity of the sender may send (e.g., transmit) one or more RLC PDUs to a RLC entity of a receiver. The one or more RLC PDUs may comprise at least one of one or more RLC SDUs and/or one or more RLC SDU segments. Each of the one or more RLC SDUs may be successfully delivered to the receiver and/or may not be successfully delivered to the receiver. Each of the one or more RLC SDU segments may be successfully delivered to the receiver and/or may not be successfully delivered to the receiver. For example, the RLC entity of the sender may generate a first RLC PDU (associated with SN=1) of a first RLC SDU (e.g., the RLC SDU 1). The first RLC PDU may comprise at least one of the first RLC SDU (associated with SN=1) and/or a first RLC SDU segment (associated with SN= 1 , comprising at least a portion of the first RLC SDU). The first RLC PDU may comprise a field indicating a sequence number (e.g., SN=1). For example, the first RLC SDU segment may comprise at least a portion of the first RLC SDU. The RLC entity of the sender may send (e.g., transmit) the first RLC PDU to the receiver, at time T=T1. The RLC entity of the receiver may fail to receive the first RLC PDU. For example, the RLC entity of the receiver may not be able to receive the first RLC PDU, e.g., due to radio channel condition of the time T=T1. The RLC entity of the sender may transmit one or more RLC PDUs comprising at least one of the first RLC SDU and/or the one or more RLC SDU segments (comprising at least a portion of the first RLC SDU), zero or more times, after the time T=T1 and until the time T=T2.

[0479] In an example, the RLC entity of the sender may transmit a RLC PDU N at time T=T2. For example, the RLC PDU N may comprise at least one of the first RLC SDU or the first RLC SDU segment.

[0480] In response to transmitting the RLC PDU N, the RLC entity of the sender may start a timer. For example, the RLC entity may start the timer at the time T=T2, for the first RLC SDU.

[0481] In an example, the RLC entity of the sender may restart the timer (for the first RLC SDU, associated with the first RLC SDU and/or of the first RLC SDU) when the RLC entity transmits a RLC PDU X comprising at least one of the first RLC SDU and/or the first RLC SDU segment. For example, the timer may be a timer for prohibiting retransmission of a RLC SDU for a certain time period after the last (latest) transmission of the RLC SDU. For example, the timer may be a retransmission prohibit timer, a delay-critical retransmission prohibit timer, and/or the like. The RLC entity of the sender may start (restart) the timer with a timer value. A RRC entity of the sender may configure the RLC entity of the sender with one or more parameters. The one or more parameters may comprise a parameter. The parameter may be the timer value. The timer may help to prevent frequent retransmission of the first RLC SDU or may prevent too early retransmission of the first RLC SDU, when the first RLC SDU becomes a delay-critical.

[0482] In another example, the RLC entity of the sender may stop the timer if the RLC entity of the sender receives at least one of a RLC status report indicating at least one of a negative acknowledgement of the first RLC SDU with SN=1, a negative acknowledgment of the first RLC SDU (or the first RLC SDU segment), a positive acknowledgment of the RLC SDU with SN=1, a positive acknowledgment of the first RLC SDU (or the first RLC SDU segment), and/or the like. If the RLC entity of the sender receives the positive acknowledgement for the first RLC SDU, there is no need for retransmission and/or for using the timer associated with the first RLC SDU and/or the sender may stop the time for the first RLC SDU. If the RLC entity of the sender receives the negative acknowledgement for the first RLC SDU, there is no need for the sender to wait until the first RLC SDU becomes delay-critical and/or the sender may retransmit the first RLC SDU and/or the sender may restart the timer.

[0483] In another example, the timer may expire at time T=T2’. For example, the timer may expire while the first RLC SDU is non-delay critical. For example, the time T=T2’ may be earlier than the time T=T3. For example, the first RLC SDU is non-delay critical before the time T=T3, and the first RLC SDU is delay-critical after the time T=T3.

[0484] In an example, when the timer expires, the UE may determine whether an RLC SDU (e.g., the first RLC SDU) associated with the timer is delay-critical or not. For example, when the timer for the first RLC SDU expires, the sender may determine whether the first RLC SDU is delay-critical or not. When the timer expires at the time T=T2’, the sender may determine that the first RLC SDU is not delay-critical. In this case, the sender may not retransmit the first RLC SDU (or the first RLC SDU segment) and/or wait until reception of a RLC Status report comprising an indication of the first RLC SDU and/or until the first RLC SDU becoming delay-critical. When the timer expires, the timer may not run until the timer starts (restarts).

[0485] In an example, the RLC entity of the sender may determine whether the first RLC SDU is delay-critical or not, whether a status of the first RLC SDU changes from non-delay-critical to delay-critical, and/or the like. The RLC entity of the sender may determine that the first RLC SDU becomes delay-critical, at time T=T3. For example, until T=T3, the RLC entity may determine that the first RLC SDU is non-delay-critical. For example, after time T=T3, the RLC entity may determine that the first RLC SDU is delay-critical. The examples shown in other FIGs of this disclosure can be used for the determination of the time T=T3 and/or the determination of whether the first RLC SDU is delay-critical or not.

[0486] In response to determining that the first RLC SDU is delay-critical, the RLC entity may determine whether the timer of the first RLC SDU is running or not. Based on the status of the timer of the first RLC SDU, the RLC entity may determine whether the RLC entity retransmits the RLC SDU or not.

[0487] For example, when the first RLC SDU becomes delay-critical, if the timer of the first RLC SDU does not run (e.g., is not running), and/or if the RLC entity of the sender does not receive a positive acknowledgment of the first RLC SDU (e.g., until T=T3 or T=T3’), the RLC entity may retransmit the first RLC SDU and/or the first RLC SDU segment, at the time T=T3’.

[0488] For example, when the first RLC SDU becomes delay-critical, if the timer of the first RLC SDU does not run, and/or if the RLC entity of the sender receives a positive acknowledgment of the first RLC SDU (e.g., until T=T3 or T=T3’), the RLC entity may not retransmit the first RLC SDU and/or the first RLC SDU segment, and/or the RLC entity may stop the timer.

[0489] For example, after the first RLC SDU becomes delay-critical, while the timer of the first RLC SDU is running, and/or if the RLC entity of the sender receives a negative acknowledgment of the first RLC, the RLC entity may retransmit the first RLC SDU and/or the first RLC SDU segment SDU, and/or the RLC entity may restart the timer.

[0490] For example, after the first RLC SDU becomes delay-critical, while the timer of the first RLC SDU is running, and/or if the RLC entity of the sender does not receive a positive acknowledgment of the first RLC SDU and/or if the RLC entity of the sender does not receive a negative acknowledgment of the first RLC SDU (e.g., until T=T3 or T=T3’), the RLC entity may not retransmit the first RLC SDU and/or the first RLC SDU segment SDU.

[0491] For example, after the first RLC SDU becomes delay-critical, when the timer of the first RLC SDU expires (e.g., after T=T3), and/or if the RLC entity of the sender does not receive a positive acknowledgment of the first RLC SDU until the expiry of the timer, the RLC entity may retransmit the first RLC SDU and/or the first RLC SDU segment SDU after the expiry of the timer.

[0492] For example, the time T=T3’ may be equal to or later than the time T=T3. For example, the T=T3’ may be a time when the lower layer indicates transmission opportunity to the RLC entity and/or a time when the RLC entity delivers a RLC PDU to a lower layer (e.g., MAC entity). The sender may be aware that the first RLC SDU is delay critical at T=T3. However, radio resource for transmission may not available until T=T3’. In this case, it may help to consider one or more events (described above) until T=T3’.

[0493] For example, if the first RLC SDU becomes delay-critical, when the timer of the first RLC SDU expires, and/or if the RLC entity does not receive indication of transmission opportunity until T=T5 and/or T=T4, the sender may not retransmit the first RLC SDU and/or the first RLC SDU segment SDU after T=T5 and/or T=T4. This may help unnecessary transmission of a delay critical RLC SDU, after PDB, from the sender to the receiver.

[0494] For example, the time T=T5 may be at least one of a time when the first RLC SDU is discarded, a time when the first PDCP PDU is discarded, and/or the like. For example, the time T=T4 may be Y ms (or second) earlier than the T=T5. For example, the Y ms may be a threshold value, a guard time value, and/or a round trip time value. This may help unnecessary transmission of a delay critical RLC SDU, after PDB, considering delay over air interface. The fourth parameter may comprise (or indicate) the Y ms.

[0495] Alternatively and/or additionally, when the timer expires, the sender may determine whether the first RLC SDU is delay critical or not. For example, when the timer expires, the sender may determine that the first RLC SDU is delay critical. In this case, if the sender does not receive the positive acknowledgement for the first RLC SDU while the timer is running (or until expiry of the timer), the sender may retransmit the first RLC SDU and/or the first RLC SDU segment, in response to the expiry of the timer. In another example, when the timer expires, the sender may determine that the first RLC SDU is not delay critical. In this case, when the timer expires, if the sender does not receive the negative acknowledgement for the first RLC SDU until the expiry of the timer (or while the timer is running), the sender may not retransmit the first RLC SDU and/or the first RLC SDU segment.

[0496] Example embodiments of FIG. 20 may help in reducing unnecessary retransmission of a RLC SDU after the RLC SDU becomes delay critical.

[0497] FIG. 21 illustrates an example as per an aspect of an embodiment of the present disclosure. In an example, a sender (e.g., a UE, a RLC entity of the sender) may use one or more timers to determine when/ whether to perform retransmission of a RLC SDU (e.g., a delay-critical RLC SDU, or when a RLC SDU becomes delay-critical). For brevity, based on the other part of the present disclosure, redundant details will be omitted.

[0498] The sender may receive the data from the upper layer, at time T=T0 (for example, as shown in the example of FIG. 19, 20). The RLC entity of the sender may send the first RLC PDU to the receiver, at time T=T1, and/or the RLC entity of the sender may transmit the one or more RLC PDUs, after the time T=T 1 and until the time T=T2 (for example, as shown in FIG. 19, 20).

[0499] In an example, the RLC entity of the sender may transmit a RLC PDU N at time T=T2. For example, the RLC PDU N may comprise at least one of the first RLC SDU or the first RLC SDU segment. In response to transmitting the RLC PDU N, the RLC entity of the sender may start the timer. For example, the RLC entity may start the timer at the time T=T2, for the first RLC SDU, with the parameter (e.g., the value, the time value, 0^th parameter, 0^th value, 0^th time value). The parameter (e.g., the parameter in the example of FIG. 20) may indicate a time duration (a time period, a duration, a period) during which the sender (e.g., the RLC entity of the sender). The time duration for the first RLC SDU is a time when the sender is not allowed to transmit a RLC PDU comprising at least one of the first RLC SDU and/or a first RLC SDU segment. When the RLC entity retransmits the first RLC SDU (and/or the first RLC SDU segment), the RLC entity may restart the timer for the first RLC SDU. When the RLC entity receives a positive acknowledgement for the first RLC SDU (and/or the first RLC SDU segment), the RLC entity may stop the timer for the first RLC SDU. When the RLC entity receives a negative acknowledgement for the first RLC SDU (and/or the first RLC SDU segment), the RLC entity may restart the timer for the first RLC SDU and/or the RLC entity may retransmit the first RLC SDU (and/or the first RLC SDU segment). When the timer expires, if the first RLC SDU is delay-critical, the RLC entity may restart the timer for the first RLC SDU and/or the RLC entity may retransmit the first RLC SDU (and/or the first RLC SDU segment). When the timer expires, if the first RLC SDU is not delay-critical, the RLC entity may stop the timer for the first RLC SDU and/or the RLC entity may send to the receiver, to request the receiver to send a RLC status PDU.

[0500] In an embodiment, while the timer for the first RLC SDU is running, the RLC entity of the sender may not transmit one or more RLC PDUs comprising at least one of the first RLC SDU and/or a first RLC SDU segment. When the timer expires, and/or if the first RLC SDU associated with the timer becomes delay-critical, the RLC entity may retransmit the RLC PDU (for example, as shown in the example of FIG. 19, 20).

[0501] In an example, the sender may determine that the first RLC SDU becomes delay-critical, based on the first parameter (1^st parameter, e.g., as shown in the example of FIG. 20). For example, the first parameter may be a first value, a first threshold. For example, the sender (e.g., the RLC entity of the sender) may determine (compare, check) whether a remaining time of the first RLC SDU is above (e.g., higher, larger), equal to, and/or less (lower, smaller) than the first parameter. For example, if the remaining time of the first RLC SDU is above and/or equal to the first parameter, the sender may determine that the first RLC SDU is non-delay critical and/or that the first RLC SDU is not delay critical. For example, if the remaining time of the first RLC SDU is less than and/or equal to the first parameter, the sender may determine that the first RLC SDU is (becomes) delay critical.

[0502] In an example, the remaining time of the first RLC SDU may be at least one of a remaining time until discarding of the first RLC SDU, a remaining time until discarding of the first PDCP SDU, a remaining time until expiry of a fifth timer (managed in the RLC entity), a remaining time until expiry of a PDCP-discard-timer for the first PDCP SDU, a remaining time until the packet delay budget of the first RLC SDU, a boundary time after which transmission of the first RLC SDU is not allowed, and/or the like. For example, the remaining time of the first RLC SDU may be a difference between a current time (e.g., a time when determining is performed) and the time T=T5.

[0503] The sender may determine that the first RLC SDU becomes delay-critical at time T=T3, based on the first parameter

[0504] In an example, when the first RLC SDU becomes delay-critical, based on that the timer is running at time T=T3, the sender may not transmit a RLC PDU comprising at least one of the first RLC SDU and/or the first RLC SDU segment, until the expiry of the timer and/or until reception of a negative acknowledgement of the first RLC SDU.

[0505] In an example, based on that the timer expires at time T=T4, and/or based on that the first RLC SDU associated with the timer is delay-critical, the sender may transmit the RLC PDU comprising at least one of the first RLC SDU and/or the first RLC SDU segment, after the expiry of the timer.

[0506] Example embodiments of FIG. 21 may help in reducing unnecessary retransmission of a RLC SDU, if the RLC SDU becomes delay critical.

[0507] FIG. 22 illustrates an example as per an aspect of an embodiment of the present disclosure. In an example, a sender (e.g., a UE, a RLC entity of the sender) may use one or more parameters to determine when/ whether to perform retransmission of a RLC SDU (e.g., a delay-critical RLC SDU, or when a RLC SDU becomes delay-critical). For brevity, based on the other part of the present disclosure, redundant details will be omitted.

[0508] The sender may receive the data from the upper layer, at time T=T0 (for example, as shown in the example of FIG. 19, 20, 21). For example, in response to receiving the first RLC SDU, at time T=T0, the RLC entity of the sender may start a fifth timer (e.g., a fifth time duration) with a fifth parameter (e.g., 5^th parameter). The fifth parameter may indicate a fifth time value. The fifth parameter may indicate when the first RLC SDU expires, when the first RLC SDU is discarded, after when transmission of the first RLC SDU is not allowed, what is the maximum allowed packet delay of the first RLC SDU, and/or the like. For example, this may indicate (be associated with) the time T=T5. For example, when the first RLC SDU is successfully transmitted to the receiver (e.g., when a positive acknowledgement for the first RLC SDU is received), the sender may stop the fifth timer. For example, when the fifth timer expires, the sender may discard the first RLC SDU and/or may indicate discarding of the first RLC SDU to the receiver.

[0509] Alternative and/or additionally, when the PDCP entity of the sender receives the first PDCP SDU from the application of the sender, the PDCP entity may start a PDCP discard timer for the first PDCP SDU. When the PDCP discard timer expires at a time T=T5’, the PDCP entity may notify (indicate to) the RLC entity that the first PDCP SDU (the first RLC SDU) is discarded (or expires). The time T=T5 may or may not be the time T=T5’ . For example, considering internal processing of the RLC entity and/or the PDCP entity, T5 may be different from T5’. For example, considering round trip time between the sender and/or the receiver, the T5 and the T5’ may be configured differently between the PDCP entity and the RLC entity. To support this, the one or more parameters may comprise a PDCP discard value for the PDCP discard timer and/or the fifth parameter for the fifth timer.

[0510] The RLC entity of the sender may send the first RLC PDU to the receiver, at time T=T1 , and/or the RLC entity of the sender may transmit the one or more RLC PDUs, after the time T=T1 and until the time T=T2 (for example, as shown in FIG. 19, 20, 21).

[0511] In an example, the RLC entity of the sender may transmit the RLC PDU N at time T=T2. In response to transmitting the RLC PDU N, the RLC entity of the sender may start the timer. For example, the RLC entity may start the timer at the time T=T2, for the first RLC SDU, with the parameter. The parameter may indicate the time duration (a time period, a duration, a period) during which the sender (e.g., the RLC entity of the sender) is not allowed to transmit the RLC PDU comprising at least one of the first RLC SDU and/or the first RLC SDU segment.

[0512] In an embodiment, if the first RLC SDU is (becomes) delay-critical, the sender may determine whether the remaining time of the first RLC SDU is less than and/or equal to a fourth parameter (e.g., 4^th parameter). For example, the fourth parameter may be a fourth value, a fourth threshold, a fourth time value, a fourth time threshold.

[0513] For example, the sender (e.g., the RLC entity of the sender) may determine (compare, check) whether a remaining time of the first RLC SDU is above (e.g., higher, larger), equal to, and/or less (lower, smaller) than the fourth parameter. The fourth parameter may be associated with a time period from the time T=T4” to the time T=T5, and/or the time T=T4”. For example, after the time T=T4”, if the first RLC SDU becomes delay-critical, if the timer is not running, the sender may not retransmit the first RLC SDU. This may help to prevent unnecessary transmission, because, if the transmission at the sender occurs after T=T4”, the reception at the receiver may occur after T=T5.

[0514] For example, if the remaining time of the first RLC SDU is above and/or equal to the fourth parameter, if the first RLC SDU is delay-critical, and/or if the timer is not running, the sender may determine that the retransmission of the first RLC SDU is allowed and/or may determine to retransmit the RLC PDU comprising at least one of the first RLC S DU and/or the first RLC SDU segment. For example, if the remaining time of the first RLC SDU is less than and/or equal to the fourth parameter, the sender may determine not to retransmit the RLC PDU.

[0515] In an example, the remaining time of the first RLC SDU may be at least one of a remaining time until discarding of the first RLC SDU, a remaining time until discarding of the first PDCP SDU, a remaining time until expiry a fifth timer (managed in the RLC entity), a remaining time until expiry of a PDCP-discard-timer for the first PDCP SDU, a remaining time until the packet delay budget of the first RLC SDU, a boundary time after which transmission of the first RLC SDU is not allowed, and/or the like. For example, the remaining time of the first RLC SDU may be a difference between a current time (e.g., a time when determining is performed) and the time T=T5.

[0516] Example embodiments of FIG. 22 may help in determining a time after which retransmission is not allowed and/or a remaining time for a RLC SDU.

[0517] FIG. 23 illustrates an example as per an aspect of an embodiment of the present disclosure. In an example, when a RLC SDU becomes delay-critical, a sender (e.g., a UE, a RLC entity of the sender) may determine one or more first portions of the RLC SDU, to prevent unnecessary transmission of one or more second portions of the RLC SDU. For brevity, based on the other part of the present disclosure, redundant details will be omitted.

[0518] The sender may receive the data from the upper layer, at time T=T0, the first RLC SDU (for example, as shown in the example of FIG. 19, 20, 21 , 22, 23).

[0519] The RLC entity of the sender may construct (compose, generate, assemble) one or more first RLC PDUs, from the first RLC SDU. For example, at each transmission opportunity, based on an amount of available resources for uplink transmission, the first RLC SDU may be segmented into one or more first RLC SDU segments. Each of the one or more first RLC PDUs may comprise each of the one or more first RLC SDU segments. For example, the one or more first RLC SDU segments may comprise a RLC SDU segment 1, a RLC SDU segment 2, a RLC SDU segments, a RLC SDU segment 4, a RLC SDU segment 5, a RLC SDU segment 6, a RLC SDU segment K, and so on. The sender may transmit the one or more first RLC PDUs to the receiver. For example, the receiver may receive some of the one or more first RLC PDUs and/or may not receive other of the one or more first RLC PDUs. For example, based on the some of the one or more first RLC PDUs, the receiver may successfully receive a first set (e.g., the RLC SDU segment 1, 3, 5) of the one or more first RLC SDU segments, and/or the receiver may not successfully receive a second set (e.g., the RLC SDU segment 2, 4) of the one or more first RLC SDU segments.

[0520] In an example, the receiver may send a RLC status report to the sender and/or the sender may receive the RLC status report at the time T=T2’. For example, the RLC status report may comprise at least one of, one or more positive acknowledgement of one or more RLC SDUs, one or more positive acknowledgement of one or more RLC SDU segments of the one or more RLC SDUs, one or more negative acknowledgement of one or more RLC SDUs, one or more negative acknowledgement of one or more RLC SDU segments of the one or more RLC SDUs, and/or the like. [0521] In an example, based on the RLC status report (e.g., the RLC status report indicates negative acknowledgement for one or more RLC SDU segment of the first RLC SDU, the RLC status report does not indicates a positive acknowledgement for one or more RLC SDU segment of the first RLC SDU), the sender may determine that the first RLC SDU is not successfully delivered, and/or that positive acknowledgement for the first RLC SDU is not received (indicated) from the receiver.

[0522] In an example, at time T= T3, the sender may determine that the first RLC SDU becomes delay critical.

[0523] In an embodiment, after the time T=T3, in response to the determining that the first RLC SDU becomes delay critical, the sender may determine to retransmit the first RLC SDU (e.g., as shown in the example of the FIG, 19, 20, 21, 22).

[0524] After determining to retransmit the first RLC SDU, the sender may determine whether to retransmit the first RLC SDU or to retransmit a third set of the one or more first RLC SDU segments. For example, the RLC entity of the sender may determine whether the RLC entity receives positive acknowledgement for at least one of the one or more first RLC PDU segments (e.g., whether the at least one of the one or more first RLC SDU segments is positively acknowledged).

[0525] In one embodiment, if the RLC entity receives positive acknowledgement for the at least one of the one or more first RLC SDU segments, the RLC entity may determine (select, identify) one or more non-acknowledged RLC SDU segments (e.g., the RLC SDU segment 2, the RLC SDU segment 4, the RLC SDU segment 6) associated with the first RLC SDU. After determining, the RLC entity may retransmit the one or more non-acknowledged RLC SDU segments, after the time T=T3 (and/or as shown in the example of the FIG. 19, 20, 21, 22).

[0526] In another embodiment, if the RLC entity does not receive positive acknowledgement for the at least one of the one or more first RLC SDU segments, the RLC entity may determine (select, identify) to retransmit the first RLC SDU (e.g., one or more RLC SDU segments comprising entire of the first RLC SDU). After determining, the RLC entity may retransmit the first RLC SDU, using one or more RLC PDUs, after the time T=T3 (and/or as shown in the example of the FIG. 19, 20, 21, 22).

[0527] Example embodiments of FIG. 23 may help in reducing usage of radio resources, when the sender determines that the first RLC SDU becomes delay critical. In response to a RLC SDU becoming delay critical, when a radio resource for the retransmission is limited, retransmitting the entire RLC SDU may cause further delay. Identifying and/or retransmitting one or more RLC SDU segments (which are not positively acknowledged) of a delay critical RLC SDU may help to support an application of high data rate and short packet delay budget.

[0528] FIG. 24 illustrates an example as per an aspect of an embodiment of the present disclosure. In an example, when a RLC SDU becomes delay-critical, a sender (e.g., a UE, a RLC entity of the sender) may start a timer for retransmission, to prevent early retransmission. For brevity, based on the other part of the present disclosure, redundant details will be omitted.

[0529] The sender may receive the data from the upper layer, at time T=T0, the first RLC SDU (for example, as shown in the example of FIG. 19, 20, 21 , 22, 23). [0530] In an example, at time T= T3, the sender may determine that the first RLC SDU becomes delay critical. Alternatively and/or additionally, at time T=T3, the PDCP entity of the sender may send to the RLC entity of the sender, an indication that the first RLC SDU (the first PDCP PDU, the first PDCP SDU) is delay-critical. In response to receiving the indication, the RLC entity may determine that the first RLC SDU is delay-critical.

[0531] In an example, at the time T=T3, based on determining that the first RLC SDU is delay-critical, the RLC entity may start a sixth timer for the first RLC SDU with a sixth parameter. For example, the sixth parameter may be a sixth time value for the sixth timer. The sixth timer may be for triggering of retransmission of a delay critical RLC SDU. For example, the sixth timer may be a delay-critical retransmission timer.

[0532] When the sixth timer expires (e.g., at T=T4’), the RLC entity may retransmit the first RLC SDU. When a positive acknowledgement is received for the first RLC SDU while the sixth timer is running, the RLC entity may stop the sixth timer and/or may not retransmit the first RLC SDU. When a negative acknowledgement is received for the first RLC SDU while the sixth time is running, the RLC entity may stop the sixth timer and/or may retransmit the first RLC SDU (or the first RLC SDU segment).

[0533] Example embodiments of FIG. 24 may help in reducing too early retransmission of a RLC SDU after the RLC SDU becomes delay-critical. For example, if the receiver already receives the RLC SDU, immediate retransmission at the time T=T3 may waste a radio resource. Accordingly, for a time duration indicated by the sixth parameter, the sender may wait for negative and/or positive acknowledgement from the receiver. And, after this time duration passes, the sender may retransmit the RLC SDU. This may help in enhancing reliability while reducing waste of radio resource.

[0534] FIG. 25 illustrates an example as per an aspect of an embodiment of the present disclosure. In an example, when a RLC SDU becomes delay-critical, a sender (e.g., a UE, a RLC entity of the sender) may retransmit the RLC SDU via a second logical channel and/or via multiple logical channels. For brevity, based on the other part of the present disclosure, redundant details will be omitted.

[0535] In an example, the RLC entity of the sender may receive, from a RRC entity of the sender, one or more parameters for configuration of retransmission of a delay critical RLC SDU. For example, the one or more parameters may comprise configuration information of one or more logical channels of the RLC entity. For example, the configuration information of the one or more logical channels may comprise a first logical channel (e.g., 1^st logical channel, logical channel 1) and/or a second logical channel (e.g., 2^nd logical channel, logical channel 2). The first logical channel may be used for transmission of a RLC SDU, if the RLC SDU is not delay-critical. The second logical channel may be used for transmission of the RLC SDU, if the RLC SDU is delay-critical.

[0536] The sender may receive the data from the upper layer, at time T=T0, the first RLC SDU (for example, as shown in the example of FIG. 19, 20, 21 , 22, 23, 24).

[0537] In an example, at time T= T1, the sender may transmit the first RLC PDU. Based on the one or more parameters, because the first RLC SDU is not delay critical, the sender may transmit the first RLC PDU via the first logical channel. [0538] In an example, the sender may receive a negative acknowledgment for the first RLC SDU, from the receiver. In response to receiving the negative acknowledgement for the first RLC SDU, the sender may determine to retransmit the first RLC SDU. For example, the send may transmit a second RLC PDU comprising at least a portion of the first RLC SDU. Based on that the first RLC SDU is not delay-critical, the sender may transmit the second RLC PDU via the first logical channel.

[0539] In an example, at time T=T3, the sender may determine that the first RLC SDU becomes delay critical. In an example, at time T=T4’, the sender may determine to retransmit the first RLC SDU (as shown in the example of FIG 19, 20, 21, 22, 23, 24). For example, the sender may transmit a third RLC PDU comprising at least a portion of the first RLC SDU. For example, based on that the first RLC SDU is delay critical, based on that a plurality of logical channel is configured for the RLC entity, and/or based on that the second logical channel is for delay-critical RLC SDU, the sender may transmit the third RLC PDU via the second logical channel and/or the sender may transmit the third RLC PDU via the first logical channel.

[0540] In another example, if the RLC entity is configured with the first logical channel and/or is not configured with the second logical channel, the sender may transmit the third RLC PDU via first logical channel, a plurality of times. For example, the configuration information of one or more logical channels of the RLC entity may comprise a configuration value indicating the plurality of times. For example, after T=T3, the RLC entity of the sender may deliver a plurality of the third RLC PDU (comprising the first RLC SDU) to the MAC entity of the sender. For example, if the configuration value indicates 3, the RLC entity may, 3 times, the third RLC PDU. The MAC entity of the sender may transmit the plurality of the third RLC PDU to the receiver.

[0541] Example embodiments of FIG. 25 may help in enhancing transmission reliability of a delay critical RLC SDU. This may help in delivering the RLC SDU from a sender to a receiver, before validity of the RLC SDU ends. This may help in supporting QoS of the application.

[0542] FIG. 26 illustrates an example as per an aspect of an embodiment of the present disclosure. In an example, an RLC entity of the base station and/or the UE may need to retransmit a RLC SDU if the RLC SDU becomes delay- critical. If a first RLC entity supports retransmission of a delay-critical RLC SDU and/or a second RLC entity does not support, this may lead to waste of radio resource and/or low QoS experience. If one or more values are not properly configured, QoS experience will be impacted. For brevity, based on the other part of the present disclosure, redundant detailswill be omitted.

[0543] In an example, a UE may send a first message to a first base station. The first message may be a RRC message. For example, the RRC message may be at least one of a RRC Setup Request message, a RRC Setup Complete message, UE Capability Information, RRC resume request message, RRC resume complete message, a UL RRC message, and/or the like. The first message may comprise one or more capability indications. For example, the one or more capability indications may indicate that the UE supports retransmission of a RLC SDU which is delay- critical, AM RLC enhancement and/or the like. The first message may comprise a NAS message. For example, the NAS message may be at least of a registration request message, a PDU session establishment request message, a UL NAS transport message, and/or the like. For example, the NAS message may comprise the one or more capability indications. For example, the first base station may be at least one of a base station OU and/or a gNB OU. In an example, in response to receiving the first message, the gNB OU may send the NAS message to a core network node (e.g., an AMF, a SMF, a UCMF (UE capability management function)).

[0544] Alternatively and/or additionally, the core network node may send a second NG (N2) message to the first base station. For example, the second NG message may comprise one or more NAS message for the UE, resource setup request for one or more PDU sessions of the UE, the one or more capability indications of the UE and/or the like. For example, the second NG message may be at least one of an initial UE context setup request message, PDU session resource setup request, PDU session resource modification request, UE context modification request, and/or the like. The one or more capability indications may indicate that the UE supports retransmission of a RLC SDU based on the RLC SDU becoming delay critical, AM RLC enhancements and/or the like. The resource setup request for one or more PDU sessions may comprise QoS information of the one or more PDU sessions.

[0545] In an example, based on the second NG message, the first base station may determine whether to use (apply) retransmission of a delay critical RLC SDU. To determine, the first base station may send a third F1 message to a second base station. For example, the second base station may be at least one of a base station distributed unit (DU) and/or a gNB DU. For example, the second base station may comprise a RLC entity of a base station, for a PDU session of the UE. For example, the third F1 message may comprise the one or more capability indications and/or the QoS information. This may help the second base station to determine whether to apply (configure, use) the retransmission of a delay critical RLC SDU. For example, based on that the UE supports the retransmission of a delay critical RLC SDU, based on that the second base station supports the retransmission of a delay critical RLC SDU, and/or based on the QoS information, the second base station may determine one or more parameters (one or more configuration parameters) configuring one or more RLC entities of the UE (and/or the second base station). For example, the third F1 message may be at least one of gNB-DU configuration update acknowledgement, gNB-CU configuration update, UE context setup request, UE context modification request, UE context modification confirm, and/or the like.

[0546] In an example, the one or more parameters (e.g., one or more configuration parameters, one or more RLC configuration parameters) may comprise the parameter (e.g., the time value (e.g., as shown in the example of FIG. 20, 21), the first parameter (e.g., parameters associated with the first timer, the first threshold, the first value, as shown in the example of FIG. 19. 21 ), the Y ( as shown in the example of FIG. 20), the one or more conditions (e.g., as shown in the example of FIG. 19), the parameter (e.g., as shown in the example of FIG. 21), the fifth parameter (e.g., as shown in the example of FIG. 22), the first value (as shown in the example of FIG. 19), the fourth parameter (e.g., fourth value, fourth threshold, as shown in the example of FIG. 20, 22), an indication of whether the UE needs to retransmission of the RLC SDU when the RLC SDU becomes delay-critical (e.g., the seventh parameter, seventh configuration), the sixth parameter (e.g., as shown in the example of FIG. 24), the configuration information of one or more logical channels (e.g., as shown in the example of FIG. 25), the second threshold value, and/or the like. For example, the one or more parameters may comprise one or more parameters of RLC entities, and/or one or more parameters for one or more logical channels, for delay-critical RLC SDU retransmission.

[0547] In an example, the second base station may send a fourth F1 message to the first base station. For example, the fourth F1 message may comprise the one or more parameters (configuring the one or more RLC entities). For example, the fourth F1 message may be at least one of gNB-DU configuration update, gNB-CU configuration update acknowledgement, UE context setup response, UE context modification response, UE context modification required, and/or the like.

[0548] In an example, the first base station may receive the fourth F1 message. Based on the fourth message, the first base station may be able to determine whether the retransmission of delay critical RLC SDU is configured or not. For example, the first base station may send to the UE, a fifth message. The fifth message may be a RRC message. For example, the fifth message may be at least one of a RRC Setup message, UE Capability Information Enquiry, RRC resume Setup message, RRC resume message, a DL RRC message, a RRC reconfiguration message, and/or the like. The fifth message may comprise the one or more parameters.

[0549] In an example, based on the fifth message, the UE may determine whether the retransmission of a delay critical RLC SDU is configured or not. The retransmission of a delay critical RLC SDU may be retransmission of a RLC SDU, when the RLC SDU becomes delay critical. The UE may use the one or more parameters in the fifth message (e.g., as shown in the example of FIG. 19, 20, 21, 22, 23, 24, 25).

[0550] For example, an RRC entity of the UE may receive the fifth message. Based on the one or more one or more parameters (e.g., of the fifth message), the RRC entity of the UE may configure the RLC entity of the UE. For example, the RLC entity of the UE may receive from the RRC entity, the one or more parameters.

[0551] Example embodiments of FIG. 26 may help a base station to determine whether to use a functionality of retransmission of a delay critical RLC SDU, whether one or more base stations supports the functionality, whether the UE supports the functionality, to deliver one or more parameters for the functionality, and/or the like.

[0552] FIG. 27 illustrates an example as per an aspect of an embodiment of the present disclosure. In an example, the first base station hosting a PDCP entity may send to the second base station hosing a RLC entity, information of whether an RLC SDU is delay critical or not. For example, for active queue management, the first base station may control a time when the first base stations delivers a PDCP PDU (a RLC SDU) to the second base station. In this case, the second base station may not be able to determine when the PDCP PDU becomes obsolete and/or how long the PDCP PDU stays at the first base station. The information from the first base station to the second base station may help in guaranteeing that delay requirement is met for the PDCP PDU. For brevity, based on the other part of the present disclosure, redundant details will be omitted. [0553] In an example, after establishing one or more PDU sessions, the second base station (e.g., the base station DU) may send to the first base station (e.g., the base station OU, the base station CU-CP, the base station CU-UP), a request. For example, the request may be that the first base station sends to the second base station, a timing information. The timing information may be an information of whether a PDCP PDU (e.g., a RLC SDU, an associated PDCP SDU) becomes delay-critical and/or an information of when the PDCP PDU expires (or be discarded) and/ow whether the PDCP PDU is delay critical.

[0554] In an example, the first base station may send a first GTP-U packet to the second base station. The first GTP- U packet may comprise at least one of a first RLC SDU (e.g., a first PDCP PDU), and/or a first timing information. For example, the first timing information may indicate a time when the first RLC SDU becomes delay-critical, a time when the first RLC SDU expires, a time after which the first RLC SDU is not allowed to be transmitted, a time when the second base station needs to discard the first RLC SDU, an indication of whether the first RLC SDU (or associated PDCP SDU) is delay critical or not. For example, the first GTP-U packet may comprise a sequence number of the first RLC SDU and/or an indication that the first RLC SDU is not delay critical.

[0555] In an example, based on the first timing information, the second base station may transmit (or retransmit) the first RLC SDU to the UE. In an example, based on the first timing information (e.g., T=T3, 50 ms later, 12:00:53), the second base station may determine a time when the first RLC SDU becomes delay-critical. For example, at T=T3 and/or at 12:00:53, the second base station may determine that the first RLC SDU becomes delay-critical. For example, 50 ms later after receiving the first RLC SDU, the second base station may determine that the first RLC SDU becomes delay-critical.

[0556] In an example, the first base station may send a second GTP-U packet to the second base station. The second GTP-U packet may comprise at least one of a second RLC SDU (e.g., a second PDCP PDU), and/or a second timing information. For example, the second timing information may indicate that the first RLC SDU becomes delay- critical, that the first RLC SDU is discarded, and/or the like. For example, the second timing information may comprise the sequence number of the first RLC SDU and/or an indication that the first RLC SDU is delay critical. For example, the second GTP-U packet may comprise a second sequence number of the second RLC SDU.

[0557] In an example, the second base station may determine whether the first RLC SDU becomes delay-critical. For example, based on the first timing information and/or based on the second timing information, the second base station may determine that the first RLC SDU becomes delay-critical.

[0558] For example, based on the determination that the first RLC SDU is delay critical, and/or based on the one or more parameters (e.g., as shown in the FIG. 26, that retransmission of delay critical RLC SDU is configured), and/or based on the first RLC SDU is not discarded (is not expired), the second base station may determine to retransmit the first RLC SDU. For example, the second base station may transmit one or more RLC PDUs comprising the first RLC SDU. [0559] In other example, based on the determination that the first RLC SDU is delay critical, and/or based on the one or more parameters (e.g., as shown in the FIG. 26, that retransmission of delay critical RLC SDU is configured), and/or based on the first RLC SDU is discarded (expired), the second base station may determine not to retransmit the first RLC SDU. For example, the second base station may not transmit one or more RLC PDUs comprising the first RLC SDU.

[0560] Example embodiments of FIG. 27 may help a second base station to determine whether a RLC SDU is delay critical. This may help for the second base station not to waste radio resource while meeting delay requirement.

[0561] FIG. 28 illustrates an example as per an aspect of an embodiment of the present disclosure. In an example, use of functionality of retransmission of a delay critical RLC SDU (e.g., triggering retransmission of a RLC SDU, based on the RLC SDU becoming delay critical), may be configured per a RLC entity. When a MAC PDU comprising one or more RLC PDUs from a plurality RLC entities, retransmission of one or more RLC SDUs of the plurality RLC entities may waste radio resource, if a RLC entity of the plurality RLC entities is associated with a low data rate and a long PDB. For brevity, based on the other part of the present disclosure, redundant details will be omitted.

[0562] In an example, a UE may be configured with the plurality of RLC entities. For example, the UE may configure the plurality of RLC entities, based on the fifth message. The plurality of RLC entities may comprise a first RLC entity and/or a second RLC entity. For example, the fifth message may indicate (comprise an indication), for the first RLC entity, to use (activate/configure) functionality of retransmission of a delay critical RLC SDU. For example, the fifth message may not indicate, for the second RLC entity, to use of function of retransmission of a delay critical RLC SDU. [0563] In an example, the UE may receive an uplink resource assignment from the second base station. In response to receiving the uplink resource assignment, the MAC entity of the UE may request the plurality of RLC entities, one or more MAC SDUs. For example, the MAC entity may indicate a transmission opportunity. The first RLC entity may deliver to the MAC entity, a first RLC PDU (a first MAC SDU, comprising at least a portion of a first RLC SDU). The second RLC entity may deliver to the MAC entity, a second RLC PDU (a second MAC SDU, comprising at least a portion of a second RLC SDU). The MAC entity may compose a MAC PDU comprising the first MAC SDU and/or the second MAC SDU. The MAC entity may transmit the MAC PDU, to the second base station.

[0564] In an example, the MAC PDU may not be successfully delivered from the UE to the second base station. For example, the MAC entity may not receive a HARQ ACK for the MAC PDU from the second base station, and/or the MAC entity may receive a HARQ NACK for the MAC PDU from the second base station. In response to detecting that the MAC PDU is not successfully delivered, the MAC entity may send a notification to the plurality of RLC entities. For example, based on that the MAC PDU comprises the first MAC SDU from the first RLC entity and/or based on that the MAC PDU comprises the second MAC SDU from the second RLC entity, the MAC entity may send the notification to the first RLC entity and/or the second RLC entity. The notification may indicate that the transmission of the MAC PDU (the first RLC PDU, the second RLC PDU) fails. [0565] In an example, based on the notification, each of the plurality of RLC entities may determine whether to perform retransmission of one of more RLC SDUs.

[0566] For example, because the first RLC entity is configured with retransmission of a delay critical RLC SDU, because the first RLC SDU is delay critical, and/or because the notification indicates HARQ transmission failure associated with the first RLC SDU, the first RLC entity may determine to retransmit the first RLC SDU. For example, the first RLC entity may deliver a third MAC SDU (comprising at least a portion of the first RLC SDU) to the MAC entity. The MAC entity may transmit a third MAC PDU comprising the third MAC SDU to the second base station.

[0567] In another example, because the first RLC entity is configured with retransmission of a delay critical RLC SDU, because the first RLC SDU is not delay critical, and/or because the notification indicates HARQ transmission failure associated with the first RLC SDU, the first RLC entity may determine not to retransmit the first RLC SDU.

[0568] In another example, because the second RLC entity is not configured with retransmission of a delay critical RLC SDU, and/or because the notification indicates HARQ transmission failure associated with the second RLC SDU, the second RLC entity may determine not to retransmit the second RLC SDU.

[0569] Example embodiments of FIG. 28 may help optimized use of radio resource considering whether retransmission of delay critical RLC SDU is configured or not, and/or whether HARQ failure occurs for the delay critical RLC SDU. This may prevent unnecessary early retransmission of a RLC SDU.

[0570] FIG. 29 illustrates an example as per an aspect of an embodiment of the present disclosure. When a retransmission of an RLC SDU is triggered based on the RLC SDU becoming delay critical, if FIFO (first in first out) mechanism is used by an RLC entity, the retransmission of the delay critical RLC SDU may be delayed until other previously buffered RLC SDUs are transmitted, leading to unnecessary delay and waste of radio resource. In an example, the RLC entity may determine priority among one or more RLC PDUs and/or the one or more RLC SDUs. For brevity, based on the other part of the present disclosure, redundant details will be omitted.

[0571] In an example, the RLC entity of a sender (e.g., a UE, a base station) may manage one or more buffers. The one or more buffers may comprise a first buffer, a second buffer, and/or a third buffer.

[0572] For example, the first buffer may store one or more first RLC SDUs, one or more first RLC SDU segments (of the one or more first RLC SDUs), and/or one or more first RLC PDUs comprising the one or more first RLC SDUs (and/or one or more first RLC SDU segments). For example, the one or more first RLC SDUs may be one or more delay-critical RLC SDUs. For example, retransmission of each of the one or more delay-critical RLC SDUs may be determined (as shown in the example of FIG. 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29).

[0573] For example, the second buffer may store one or more second RLC SDUs, one or more second RLC SDU segments (of the one or more second RLC SDUs), and/or one or more second RLC PDUs comprising (containing) the one or more second RLC SDUs (and/or one or more second RLC SDU segments). The one or more second RLC SDUs may be one or more RLC SDU which are not previously transmitted by the RLC entity. In an example, when a second RLC SDU of the one or more second RLC SDUs becomes delay-critical, the second RLC SDU may be moved from the second buffer to the first buffer.

[0574] For example, the third buffer may store one or more third RLC SDUs, one or more third RLC SDU segments (of the one or more third RLC SDUs), and/or one or more third RLC PDUs comprising the one or more third RLC SDUs (and/or one or more third RLC SDU segments). The one or more third RLC SDUs may be one or more RLC SDU for which negative acknowledgement are received by the RLC entity. After the one or more third RLC PDUs are transmitted, the one or more third RLC PDUs (and/or one or more associated RLC PDUs of the one or more third RLC PDUs) may be removed from the third buffer. In an example, when a third RLC SDU of the one or more third RLC SDUs becomes delay-critical, the third RLC SDU may be moved from the third buffer to the first buffer. Alternatively and/or additionally, when the first RLC SDU of the one or more first RLC SDUs becomes delay-critical, the first RLC SDU may be moved from the first buffer to the third buffer.

[0575] In an example, the RLC entity may receive from a MAC entity (e.g., a lower layer), an indication indicating a transmission opportunity. For example, the MAC entity may indicate a total size of a RLC PDU (e.g., AMD PDU) that can be transmitted in the transmission opportunity. In response to receiving the indication, the RLC entity may form the RLC PDU.

[0576] In an example, when the RLC entity forms the RLC PDU, the RLC entity may determine prioritization. For example, the prioritization may be determining which RLC PDU, RLC SDU, control PDU is prioritized for transmission. That the RLC entity prioritizes transmission of A over B may be that the RLC entity sends the A (or a part of the A) before the RLC entity sends the B (or a part of the B).

[0577] For example, the RLC entity may prioritize transmission of a RLC control PDU (e.g., one or more RLC PDUs not comprising at least a portion of one or more RLC SDUs) over one or more non RLC control PDUs (e.g., AMD PDUs, e.g., one or more RLC PDUs comprising at least a portion of one or more RLC SDUs). The RLC entity may prioritize transmission of a first data (e.g., one or more first RLC SDUs, one or more first RLC SDU segments, one or more first RLC PDUs) from the first buffer over a second data (e.g., one or more second RLC SDUs, one or more second RLC SDU segments, one or more second RLC PDUs) from the second buffer. The RLC entity may prioritize transmission of the first data from the first buffer over a third data (e.g., one or more third RLC SDUs, one or more third RLC SDU segments, one or more third RLC PDUs) from the third buffer. This may help a delay-critical data to be delivered from the sender to the receiver, before expiration of packet delay budget. For example, the one or more non RLC control PDUs may be at least one of the first data, the second data, and/or the third data.

[0578] In another example, the RLC entity may prioritize transmission of the RLC control PDU over the one or more RLC PDUs. The RLC entity may prioritize transmission of the first data from the first buffer over a second data from the second buffer. The RLC entity may prioritize transmission of the third data from the third buffer over the first data from the first buffer. This may help reducing waste of radio resource, because the sender is able to determine that the third data is not received by the receiver, while the sender may not be able to determine whether the first data is not received by the receiver.

[0579] Alternatively and/or additionally, the RLC entity may prioritize transmission of the first data from the first buffer over the RLC control PDU. The RLC entity may prioritize transmission of the RLC control PDU over the second data from the second buffer and/or the third data from the third buffer. This may help in supporting low delay data transmission while supporting low delay data reception. For example, the RLC control PDU (e.g., a RLC status PDU, the RLC status report) sent by the RLC entity of the sender (e.g., a first node) may comprise one or more positive acknowledgement and/or one or more negative acknowledgment for one or more RLC SDUs that the sender (e.g., the first node) may receive from the receiver (e.g., the second node). By prioritizing the RLC control PDU over the second data and/or the third data, the sender (of the first node) may be able to receive a delay critical data from the second node. By prioritizing the first data over the RLC control PDU, the sender may be able to send a delay critical data to the second node.

[0580] In an example, the RLC entity of the sender may perform prioritization without using the first buffer, the second buffer, and/or the third buffer. Alternatively, the first buffer may be the third buffer. In this case, the RLC entity may associate an attribute to each RLC SDU in the first buffer. For example, the attribute may be whether the RLC SDU is delay critical or not.

[0581] In another example, the RLC entity may determine to transmit (or retransmit) a RLC SDU A1 , a RLC SDU A2. For example, the RLC SDU A1 may be a delay critical RLC SDU and/or the RLC SDU A2 may be non-delay critical SDU. In this case, the RLC entity may prioritize transmission of the RLC SDU A1 over the RLC SDU A2. This may increase the possibility that packet delay budget is met for the one or more RLC SDUs.

[0582] In another example, the RLC entity may determine to transmit (or retransmit) a RLC SDU B1 , a RLC SDU B2. For example, the RLC SDU B1 may be a delay critical RLC SDU for which are non-acknowledged, the RLC SDU B2 may be a delay critical RLC SDU which is negatively acknowledged. In this case, the RLC entity may prioritize transmission of the RLC SDU B2 over the RLC SDU B1. This may help increase of reliability, because there is a possibility that the RLC SDU B1 is delivered successfully.

[0583] In another example, the RLC entity may determine to transmit (or retransmit) a RLC SDU E1 , a RLC SDU E2. For example, the RLC SDU E1 may be a delay critical RLC SDU for which are non-acknowledged, the RLC SDU E2 may be a RLC SDU which is negatively acknowledged. In this case, the RLC entity may prioritize transmission of the RLC SDU E1 over the RLC SDU E2. This may help increase of reliability, because there is a more transmission opportunity for RLC SDU E2.

[0584] In another example, the RLC entity may determine to transmit (or retransmit) a RLC SDU C1 , a RLC SDU C2. For example, the RLC SDU C1 may be a delay critical RLC SDU which is previously transmitted, the RLC SDU C2 may be a delay critical RLC SDU which is not previously transmitted. In this case, the RLC entity may prioritize transmission of the RLC SDU C1 over the RLC SDU 02. This may help increase of quality of experience, because there is a possibility that other PDUs of a PDU set for which the RLC SDU 01 is associated may be delivered successfully. [0585] In another example, the RLC entity may determine to transmit (or retransmit) a RLC SDU D1 , a RLC SDU D2. For example, the RLC SDU D1 may be a delay critical RLC SDU which is previously transmitted, the RLC SDU D2 may be a delay critical RLC SDU which is not previously transmitted. In this case, the RLC entity may prioritize transmission of the RLC SDU D2 over the RLC SDU D1. This may help increase of reliability of data delivery, because there is a possibility that the RLC SDU D1 may be delivered successfully.

[0586] In another example, the RLC entity may determine to transmit (or retransmit) a RLC SDU F1 , a RLC SDU F2. For example, the RLC SDU F1 may be a delay critical RLC SDU, the RLC SDU F2 may be a RLC SDU which is not previously transmitted. In this case, the RLC entity may prioritize transmission of the RLC SDU F2 over the RLC SDU F1. This may help delivery of more data units.

[0587] In another example, the RLC entity may determine to transmit (or retransmit) a RLC SDU G1 , a RLC control PDU G2 (e.g., a RLC status PDU) For example, the RLC SDU G1 may be a delay critical RLC SDU. In this case, the RLC entity may prioritize transmission of the RLC SDU G1 over the RLC control PDU G2. This may help when uplink data is more important than downlink data.

[0588] In another example, the RLC entity may determine to transmit (or retransmit) a RLC SDU H 1 , a RLC control PDU H2 (e.g., a RLC status PDU) For example, the RLC SDU H 1 may be a delay critical RLC SDU. In this case, the RLC entity may prioritize transmission of the RLC control PDU H2 over the RLC SDU H 1. This may help when downlink data is more important than uplink data.

[0589] In an example, when the transmission opportunity is indicated to the RLC entity by the MAC entity, the RLC entity may deliver to the MAC entity, a first MAC SDU comprising a data (which is prioritized) earlier than a MAC SDU which comprising another data (which is not prioritized). The MAC entity may transmit the first MAC SDU and/or the second MAC SDU.

[0590] Example embodiments of FIG. 29 may help efficient use of a radio resource, when an allocated resource is not enough to deliver all data in the one or more buffers. By determining which data is prioritized for transmission, the RLC entity can support timely delivery of one or more RLC SDUs after becoming delay-critical.

[0591] Clause 1. A method comprising: receiving, by a wireless device from a base station, one or more configuration parameters comprising: a first configuration parameter indicating to retransmit a radio link control (RLC) service data unit (SDU) in response to the RLC SDU becoming delay-critical; and a time value for a timer to prohibit retransmission of the RLC SDU; transmitting, by the wireless device, a first RLC PDU comprising a first RLC SDU; starting, by the wireless device, the timer for the first RLC SDU; determining, by the wireless device, that: the first RLC SDU becomes delay-critical; and a positive acknowledgement for the first RLC SDU is not received, while the timer is running; and transmitting, by the wireless device and based on the determining, a second RLC PDU comprising the first RLC SDU after expiration of the timer for the first RLC SDU. [0592] Clause 2. A method comprising: receiving, by a wireless device from a base station, one or more configuration parameters comprising a time value for a timer to prohibit retransmission of a radio link control (RLC) service data unit (SDU); and retransmitting, by the wireless device, the RLC SDU, based on determining: the RLC SDU becomes delay- critical; and expiry of the timer of the RLC SDU.

[0593] Clause 3. A method comprising: receiving, by a wireless device from a base station, one or more configuration parameters comprising a time value for a timer to prohibit retransmission of a radio link control (RLC) service data unit (SDU); and retransmitting, by the wireless device, the RLC SDU, based on determining: the RLC SDU becomes delay- critical; and the timer of the RLC SDU is not running.

[0594] Clause 4. A method comprising: receiving, by a wireless device from a base station, one or more configuration parameters comprising an indication to retransmit a radio link control (RLC) service data unit (SDU) in response to the RLC SDU becoming delay-critical; and retransmitting, by the wireless device and based on the one or more conditions being met, the RLC SDU, after the RLC SDU becomes delay-critical.

[0595] Clause 5. The method of clause 4 (or any other preceding clause), wherein the one or more configuration parameters comprises a time value for a timer to prohibit retransmission of a radio link control (RLC) service data unit (SDU).

[0596] Clause 6. The method of clause 5 (or any other preceding clause), wherein the time is at least one of a prohibit timer, a retransmission prohibit timer, a delay-critical retransmission timer.

[0597] Clause 7. The method of clause 4-6 (or any other preceding clause), wherein the wireless device starts the timer in response to transmitting a RLC protocol data unit (PDU) comprising at least one of a segment of the RLC SDU or the RLC SDU.

[0598] Clause 8. The method of clause 4-7 (or any other preceding clause), wherein the wireless device stops the timer in response to receiving a positive acknowledgment for the RLC SDU, from the base station, and the wireless device does not stop the timer in response to receiving a negative acknowledgement for the RLC SDU.

[0599] Clause 9. The method of clause 4-8 (or any other preceding clause), wherein the wireless device stops the time in response to receiving an indication that the RLC SDU is discarded.

[0600] Clause 10. The method of clause 4 (or any other preceding clause), wherein the one or more conditions comprises a first condition that the RLC SDU becomes delay-critical.

[0601] Clause 11. The method of clause 10 (or any other preceding clause), wherein the RLC SDU becomes delay critical, if a remaining time of the RLC SDU becomes equal to or less than a first value, or if a first timer of the RLC SDU expires.

[0602] Clause 12. The method of clause 11 (or any other preceding clause), wherein the one or more configuration parameters comprises the first value indicating a first threshold. [0603] Clause 13. The method of clause 11 (or any other preceding clause), wherein the wireless device starts the first timer with a first timer value, when the wireless device receives the RLC SDU from an application of the wireless device.

[0604] Clause 14. The method of clause 13 (or any other preceding clause), wherein the one or more configuration parameters comprise the first timer value.

[0605] Clause 15. The method of clause 14 (or any other preceding clause), wherein a RLC entity of the wireless device starts the timer with the first timer value.

[0606] Clause 16. The method of clause 12 (or any other preceding clause), wherein the one or more configuration parameters comprises a second value indicating a second threshold, wherein a PDCP entity of the wireless device uses the second threshold value to determine whether a PDCP SDU associated with the RLC SDU is delay-critical PDCP SDU.

[0607] Clause 17. The method of clause 4 (or any other preceding clause), wherein the one or more conditions comprises a second condition that a timer of the RLC SDU is not running.

[0608] Clause 18. The method of clause 4 (or any other preceding clause), wherein that the timer is not running if the timer is not started after expiry of the timer.

[0609] Clause 19. The method of clause 4-18 (or any other preceding clause), wherein the wireless device retransmit a RLC PDU of the RLC SDU if the first condition and the second condition are met.

[0610] Clause 20. The method of clause 19 (or any other preceding clause), wherein the RLC PDU comprises at least one of the RLC SDU or a RLC SDU segment comprising at least a portion of the RLC SDU.

[0611] Clause 21. The method of clause 4-20 (or any other preceding clause), wherein the wireless device does not retransmit the RLC PDU if the first condition is met and the second condition is not met.

[0612] Clause 22. The method of clause 4 (or any other preceding clause), wherein the one or more conditions comprises a third condition that the wireless device receives a negative acknowledgement for the RLC SDU.

[0613] Clause 23. The method of clause 4-22 (or any other preceding clause), wherein the wireless retransmit the RLC PDU, if the second condition is met and the third condition is met.

[0614] Clause 24. The method of clause 19 or 22 (or any other preceding clause), wherein the wireless device retransmits the RLC PDU, if the wireless device receives from the base station, an uplink resources for transmission of one or more RLC SDUs which are delay-critical.

[0615] Clause 25. The method of clause 4-24 (or any other preceding clause), wherein the one or more configuration parameters comprises a fourth value indicating a fourth threshold.

[0616] Clause 26. The method of clause 4-25 (or any other preceding clause), wherein the one or more conditions comprises a fourth condition that a remaining time of the RLC SDU is equal to or less than the fourth threshold.

[0617] Clause 27. The method of clause 24-26 (or any other preceding clause), wherein the wireless device retransmits the RLC PDU, if the fourth condition is not met. [0618] Clause 28. The method of clause 4-27 (or any other preceding clause), wherein the one or more configuration parameters comprises a fifth value for a fifth timer.

[0619] Clause 29. The method of clause 28 (or any other preceding clause), wherein the wireless device starts the fifth timer with the fifth value, when the wireless device receives the RLC SDU.

[0620] Clause 30. The method of clause 29 (or any other preceding clause), the remaining time of the RLC SDU is the remaining time of the fifth timer until expiry of the fifth timer.

[0621] Clause 31. A method comprising: receiving, by a wireless device from a base station, a configuration parameter configuring retransmission of a delay critical radio resource control (RLC) service data unit (SDU); and transmitting, by the wireless device and based on a first RLC SDU being delay critical, a first RLC PDU comprising a first RLC SDU segment of the first RLC SDU, wherein the first RLC SDU segment is not acknowledged by the base station.

[0622] Clause 32. A method comprising: receiving, by a wireless device from a base station, a configuration parameter configuring retransmission of a delay critical radio resource control (RLC) service data unit (SDU); and determining, by the wireless device, that a first RLC SDU is delay critical; and transmitting, by the wireless: a first RLC PDU comprising a first RLC SDU segment of the first RLC SDU, in response to receiving negative acknowledgement of the first RLC SDU segment; and a second RLC PDU comprising a second RLC SDU segment of the first RLC SDU, in response to not receiving acknowledgement of the second RLC SDU segment.

[0623] Clause 33. A method comprising: receiving, by a wireless device from a base station, one or more configuration parameters comprising: a seventh configuration parameter configuring retransmission of a delay critical radio resource control (RLC) service data unit (SDU); and a configuration parameter of a time value for a timer prohibiting the retransmission of the delay critical RLC SDU; starting, by the wireless device, the prohibit timer after transmitting a RLC PDU comprising a segment of a first RLC SDU, with the time value; determining, by the wireless device, that the first RLC SDU is delay critical; and not transmitting, by the wireless device and based on determining, a RLC PDU comprising a second segment of the first RLC SDU, in response to the timer running.

[0624] Clause 34. A method comprising: receiving, by a wireless device from a base station, one or more configuration parameters comprising: a seventh configuration parameter configuring retransmission of a delay critical radio resource control (RLC) protocol data unit (PDU); and a configuration parameter of a time value for a timer prohibiting the retransmission of the delay critical RLC PDU; starting, by the wireless device, the timer after retransmitting a RLC PDU; determining, by the wireless device, that a RLC PDU is delay critical; and not retransmitting, by the wireless device and based on determining, the RLC PDU, in response to the timer running.

[0625] Clause 35. A method comprising: receiving, by a wireless device from a base station, one or more configuration parameters comprising: a seventh configuration parameter configuring retransmission of a delay critical radio resource control (RLC) protocol data unit (PDU); and a configuration parameter of a time value for a timer prohibiting the retransmission of the delay critical RLC PDU; starting, by the wireless device, the timer after retransmitting a RLC PDU; determining, by the wireless device, that a RLC PDU is delay critical; and retransmitting, by the wireless device and based on determining, the RLC PDU, in response to expiry of the timer.

[0626] Clause 36. A method comprising: receiving, by a wireless device from a base station, one or more configuration parameters comprising: a seventh configuration parameter configuring retransmission of a delay critical radio resource control (RLC) protocol data unit (PDU); and a sixth configuration parameter of a sixth time value for a retransmission timer triggering the retransmission of the delay critical RLC PDU; receiving, by the wireless device, an indication that a RLC SDU is delay critical; starting, by the wireless device and based on the indication, a retransmission timer for a RLC PDU of the RLC SDU; retransmitting, by the wireless device and based on expiry of the retransmission timer, the RLC PDU.

[0627] Clause 37. A method comprising: receiving, by a wireless device from a base station, one or more configuration parameters comprising: a seventh configuration parameter configuring retransmission of a delay critical radio resource control (RLC) protocol data unit (PDU); and a sixth configuration parameter of a sixth time value for a retransmission timer triggering the retransmission of the delay critical RLC PDU; a fourth configuration parameter of a fourth time value for determining whether a RLC SDU is delay critical; determining, by the wireless device and based on the fourth time value, that a RLC SDU is delay critical; starting, by the wireless device and based on the sixth time value, a retransmission timer for a RLC PDU of the RLC SDU; retransmitting, by the wireless device and based on expiry of the retransmission timer, the RLC PDU.

[0628] Clause 38. A method comprising: receiving, by a wireless device from a base station, one or more configuration parameters comprising: a fifth configuration parameter of a fifth time value for a RLC discard timer of a RLC SDU; a fourth configuration parameter of a threshold time value for the retransmission of a delay critical RLC SDU; starting, by the wireless device, a first RLC discard timer for a first RLC SDU; determining, by the wireless device, that the first RLC SDU is delay critical; and retransmitting, by the wireless device, a first RLC PDU of the first RLC SDU, based on that remaining value of the discard timer is more than the threshold time value.

[0629] Clause 39. A method comprising: receiving, by a wireless device from a base station, one or more configuration parameters comprising a seventh configuration parameter configuring retransmission of a delay critical radio resource control (RLC) service data unit (SDU); determining, by the wireless device, that a RLC SDU is delay critical; and retransmitting, by the wireless device and based on determining, one or more RLC PDUs comprising one or more SDU segments of the RLC SDU, in response to the timer prohibiting retransmission for the RLC SDU not being running.

[0630] Clause 40. A method comprising: receiving, by a wireless device from a base station, one or more configuration parameters comprising a seventh configuration parameter configuring retransmission of a delay critical radio resource control (RLC) service data unit (SDU); a fourth configuration parameter of a threshold time value for the retransmission of a delay critical RLC SDU; determining, by the wireless device, that a RLC SDU is delay critical; and sending, by the wireless device, a delay status report requesting resource allocation for retransmission of at least one of one or more RLC PDUs comprising one or more non-acknowledged RLC SDU segments of the RLC SDU; receiving, by the wireless device, an allocation of uplink resource; and not retransmitting, by the wireless device, the at least one of the one or more non-acknowledged RLC SDU segments, in response to a remaining time of the RLC SDU being less than the threshold time value.

[0631] Clause 41. A method comprising: receiving, by a wireless device from a base station, one or more configuration parameters comprising: a seventh configuration parameter configuring retransmission of a radio resource control (RLC) protocol data unit (PDU) of a delay critical RLC service data unit (SDU); and determining, by the wireless device, that: a first RLC SDU is delay critical; a first RLC PDU segment of the first RLC SDU is not acknowledged; and a second RLC PDU segment of the first RLC SDU is acknowledged; and retransmitting, by the wireless device and based on determining, the first RLC PDU segment.

[0632] Clause 42. A method comprising: receiving, by a wireless device from a base station, one or more configuration parameter of retransmission of a delay critical radio link control (RLC) data unit (SDU), comprising: a first time threshold triggering retransmission of a RLC SDU; a fourth time threshold prohibiting retransmission of the RLC SDU; determining, by the wireless device and based on a first remaining time of a first RLC SDU being the first time threshold, to retransmit the first RLC SDU; and receiving, by the wireless device, a resource allocation for uplink transmission; and determining, by the wireless and based on a fourth remaining time of the first RLC SDU being less than the second time threshold, not to retransmit the first RLC SDU.

[0633] Clause 43. A method comprising: sending, by a wireless device to a base station, one or more parameter of one or more capabilities supported by the wireless device, comprising a capability of retransmission of a delay critical radio link control (RLC) data unit (DU); receiving, by a wireless device from a base station, one or more configuration parameter of retransmission of a delay critical RLC DU.

[0634] Clause 44. A method comprising: receiving, by a wireless device from a base station, one or more configuration parameters comprising: a seventh configuration parameter configuring retransmission of a delay critical radio resource control (RLC) service data unit (SDU); determining, by the wireless device, that: a first RLC SDU is delay critical, wherein the first RLC SDU comprises a first RLC SDU segment and a second RLC segment; and an acknowledgement is received for a second RLC SDU segment; retransmitting, by the wireless device and based on determining, a first RLC PDU comprising the first RLC SDU segment; and not retransmitting, by the wireless device based on determining, a second RLC PDU comprising the second RLC SDU segment.

[0635] Clause 45. A method comprising: receiving, by a wireless device from a base station, one or more configuration parameters comprising: a seventh configuration parameter configuring retransmission of a delay critical radio resource control (RLC) service data unit (SDU); determining, by the wireless device, that: a first RLC SDU is delay critical, wherein the first RLC SDU comprises a first RLC SDU segment, a third RLC segment; and a negative acknowledgement is received for a third RLC SDU segment; retransmitting, by the wireless device and based on determining, a first RLC PDU comprising the first RLC SDU segment; and retransmitting, by the wireless device and after retransmitting the first RLC PDU, a second RLC PDU comprising the third RLC SDU segment.

[0636] Clause 46. A method comprising: sending, by a base station (BS) central unit (CU) to a BS distributed unit (DU), a request for one or more configuration parameters, comprising a radio link control (RLC) capability information indicating support of retransmission of one or more RLC protocol data unit (PDU) segments of a delay critical RLC service data unit (SDU); receiving, by the BS CU from the BS DU, one or more first configuration parameters configuring, the retransmission of the one or more RLC PDU segments; and sending, by the BS CU to a wireless device, the one or more configuration parameters.

[0637] Clause 47. A method comprising: receiving, by a base station (BS) distributed unit (DU) from a BS central unit (CU), a request for one or more configuration parameters, comprising a radio link control (RLC) capability information indicating support of retransmission of one or more RLC protocol data unit (PDU) segments of a delay critical RLC service data unit (SDU); sending, by the BS DU to the BS CU, one or more first configuration parameters configuring, the retransmission of the one or more RLC PDU segments; receiving, by the BS DU from the BS CU, a RLC SDU; and retransmitting, by the BS DU to a wireless device, one or more first RLC segments of the RLC SDU, in response to the RLC SDU being delay critical.

[0638] Clause 48. A method comprising: receiving, by a wireless device from a base station, one or more configuration parameters comprising: a seventh configuration parameter configuring retransmission of a delay critical radio resource control (RLC) protocol data unit (PDU); and a second configuration parameter of a time value for a prohibit timer prohibiting the retransmission of the delay critical RLC PDU; determining, by the wireless device, that a RLC PDU is delay critical; and retransmitting, by the wireless device and based on determining, the RLC PDU, in response to the prohibit timer for the RLC PDU not being running.

[0639] Clause 49. A method comprising: receiving, by a wireless device from a base station: a seventh configuration parameter of a first radio link control (RLC) entity, configuring retransmission of a delay critical data unit; and a eighth configuration parameter of a second RLC entity, not configuring retransmission of the delay critical data unit; and determining, by the wireless device, transmission failure of a medium access control (MAC) protocol data unit (PDU) comprising a first RLC PDU of the first RLC entity and a second PLC SDU of the second RLC entity; and retransmitting, by the wireless device, the first RLC PDU, based on: that the first RLC PDU is delay critical; and the seventh configuration parameter.

[0640] Clause 50. A method comprising: receiving, by a radio link control (RLC) entity of a wireless device from a protocol data convergence protocol (PDCP) entity of the wireless device, one or more RLC SDUs, wherein the one or more RLC SDUs comprises a first RLC SDU and a second RLC SDU; prioritizing, by the RLC entity, transmission of the first RLC SDU over the second RLC SDU, in response to determining: a first RLC SDU becomes delay-critical; and a second RLC SDU is non-delay-critical; submitting, by the RLC entity to a medium access control (MAC) entity of the wireless device, one or more RLC protocol data units (PDUs) comprising the first RLC SDU. [0641] Clause 51. A method comprising: receiving, by a radio link control (RLC) entity of a wireless device from a protocol data convergence protocol (PDCP) entity of the wireless device, one or more RLC SDUs, wherein the one or more RLC SDUs comprises a first RLC SDU and a second RLC SDU; prioritizing, by the RLC entity, transmission of the first RLC SDU over the second RLC SDU, in response to determining: a first RLC SDU becomes delay-critical; and a second RLC SDU is negatively acknowledged; and submitting, by the RLC entity to a medium access control (MAC) entity of the wireless device, one or more RLC protocol data units (PDUs) comprising the first RLC SDU.

[0642] Clause 52. A method comprising: receiving, by a radio link control (RLC) entity of a wireless device from a protocol data convergence protocol (PDCP) entity of the wireless device, one or more RLC SDUs, wherein the one or more RLC SDUs comprises a first RLC SDU and a second RLC SDU; prioritizing, by the RLC entity, transmission of the second RLC SDU over the first RLC SDU, in response to determining: a first RLC SDU becomes delay-critical; and a second RLC SDU is negatively acknowledged; and submitting, by the RLC entity to a medium access control (MAC) entity of the wireless device, one or more RLC protocol data units (PDUs) comprising the second RLC SDU.

[0643] Clause 53. A method comprising: receiving, by a radio link control (RLC) entity of a wireless device from a protocol data convergence protocol (PDCP) entity of the wireless device, one or more RLC SDUs, wherein the one or more RLC SDUs comprises a first RLC SDU; determining, by the RLC entity, whether a status PDU is triggered; prioritizing, by the RLC entity, transmission of: the status PDU over the first RLC SDU, in response to determining that the status PDU is triggered; and a first RLC SDU, in response to determining that the first RLC SDU is delay-critical; and submitting, by the RLC entity to a medium access control (MAC) entity of the wireless device, one or more RLC protocol data units (PDUs) comprising at least one of the status PDU or the first RLC SDU.

[0644] Clause 54. A method comprising: receiving, by a radio link control (RLC) entity of a wireless device from a protocol data convergence protocol (PDCP) entity of the wireless device, one or more RLC SDUs, wherein the one or more RLC SDUs comprises a first RLC SDU; determining, by the RLC entity, that a status PDU is triggered; prioritizing, by the RLC entity, transmission of the first RLC SDU, in response to determining that the first RLC SDU is delay-critical; and submitting, by the RLC entity to a medium access control (MAC) entity of the wireless device, one or more RLC protocol data units (PDUs) comprising the first RLC SDU.

[0645] Clause 55. A method comprising: sending, by a wireless device to a base station, one or more parameter of one or more capabilities supported by the wireless device, comprising a capability of retransmission of a delay critical radio link control (RLC) data unit (DU); receiving, by a wireless device from a base station, one or more configuration parameter of retransmission of a delay critical RLC DU; and receiving, by a wireless device from a base station, a medium access control (MAC) control element (CE) activating retransmission of a delay critical RLC DU.

[0646] Clause 56. A method comprising: receiving, by a wireless device from a base station, one or more configuration parameters comprising: a seventh configuration parameter configuring retransmission of a radio resource control (RLC) service data unit (SDU) in response to the RLC SDU becoming delay-critical; determining, by the wireless device, that a first RLC SDU becomes delay critical, wherein the first RLC SDU comprises a first RLC SDU segment and a second RLC segment; retransmitting, by the wireless device and based on the determining: the first RLC SDU segment, based on a positive acknowledgement not being received for the first SDU segment; and the second RLC SDU segment, based on a negative acknowledgement being received for the second SDU segment.

[0647] Clause 57. A method comprising: receiving, by a wireless device from a base station, one or more configuration parameters comprising: a seventh configuration parameter configuring retransmission of a radio resource control (RLC) service data unit (SDU) in response to the RLC SDU becoming delay-critical; determining, by the wireless device, that a first RLC SDU becomes delay critical, wherein the first RLC SDU comprises a first RLC SDU segment and a second RLC segment; considering for retransmission of, by the wireless device: the first RLC SDU segment, based on that that a first RLC SDU becomes delay critical; and the second RLC SDU segment, in response to receiving a negative acknowledgement being received for the second SDU segment; and retransmitting, by the wireless device, the first RLC SDU segment, after retransmitting the second RLC SDU segment.

[0648] Clause 58. A method comprising: receiving, by a wireless device from a base station, one or more configuration parameters comprising: a seventh configuration parameter configuring retransmission of a radio resource control (RLC) service data unit (SDU) in response to the RLC SDU becoming delay-critical; determining, by the wireless device, that a first RLC SDU becomes delay critical, wherein the first RLC SDU comprises a first RLC SDU segment and a second RLC segment; considering for retransmission of, by the wireless device: the first RLC SDU segment, based on that that a first RLC SDU becomes delay critical; and the second RLC SDU segment, in response to receiving a negative acknowledgement being received for the second SDU segment; and retransmitting, by the wireless device, the second RLC SDU segment, after retransmitting the first RLC SDU segment.

[0649] Clause 59. A method comprising: receiving, by a wireless device from a base station, one or more configuration parameters comprising: a seventh configuration parameter configuring retransmission of a radio resource control (RLC) service data unit (SDU) in response to the RLC SDU becoming delay-critical; determining, by the wireless device, that a first RLC SDU becomes delay critical; considering for retransmission of, by the wireless device: the first RLC SDU, based on that that a first RLC SDU becomes delay critical; and the second RLC SDU, in response to receiving a negative acknowledgement being received for the second SDU; and retransmitting, by the wireless device, the first RLC SDU, after retransmitting the second RLC SDU.

[0650] Clause 60. A method comprising: receiving, by a wireless device from a base station, one or more configuration parameters comprising: a seventh configuration parameter configuring retransmission of a radio resource control (RLC) service data unit (SDU) in response to the RLC SDU becoming delay-critical; determining, by the wireless device, that a first RLC SDU becomes delay critical; considering for retransmission of, by the wireless device: the first RLC SDU, based on that that a first RLC SDU becomes delay critical; and the second RLC SDU, in response to receiving a negative acknowledgement being received for the second SDU; and retransmitting, by the wireless device, the second RLC SDU, after retransmitting the first RLC SDU.

Claims

1. A method comprising: receiving or determining, by a wireless device, one or more configuration parameters, the one or more configuration parameters comprising an indication to retransmit a radio link control (RLC) service data unit (SDU) in response to the RLC SDU becoming delay-critical; and retransmitting, by the wireless device, based on one or more conditions being met, the RLC SDU, after the RLC SDU becomes delay-critical.

2. The method of claim 1 , wherein the one or more configuration parameters comprises a time value for a first timer, the first timer being a delay-critical timer for a radio link control (RLC) service data unit (SDU).

3. The method of claim 1 , wherein the one or more configuration parameters comprises a time value for a first timer, the first timer being used to determine whether a radio link control (RLC) service data unit (SDU) is delay-critical.

4. The method of any of the previous claims, comprising the wireless device determining whether the RLC SDU becomes delay-critical.

5. The method of any of the preceding claims, comprising the wireless device starting the first timer with a first timer value, upon reception (or generation), by the wireless device, of the RLC SDU from an application of the wireless device.

6. The method of any of the preceding claims, comprising the wireless device waiting for a negative and/or positive acknowledgement to trigger a retransmission of the RLC SDU for a time duration (or while the timer is above a threshold), the wireless device retransmitting the RLC SDU after this time duration passes (or once the timer has become lower than a threshold).

7. A method comprising: receiving, by a wireless device from a base station, one or more configuration parameters, the one or more configuration parameters comprising a time value for a timer, the timer being defined to prohibit retransmission of a radio link control (RLC) service data unit (SDU); and retransmitting, by the wireless device, the RLC SDU, based on determining: that the RLC SDU becomes delay-critical; and expiry of the timer of the RLC SDU.

8. A method comprising: receiving, by a wireless device from a base station, one or more configuration parameters, the one or more configuration parameters comprising a time value for a timer, the timer being defined to prohibit retransmission of a radio link control (RLC) service data unit (SDU); and retransmitting, by the wireless device, the RLC SDU, based on determining: that the RLC SDU becomes delay-critical; and the timer of the RLC SDU is not running.

9. The method of any of claims 7 or 8, wherein the timer is at least one of a prohibit timer, a retransmission prohibit timer, a delay-critical retransmission timer or a delay-critical retransmission timer.

10. The method of any of the preceding claims, wherein the wireless device starts the timer in response to transmitting a RLC protocol data unit (PDU), the RLC PDU comprising at least one of a segment of the RLC SDU or the RLC SDU.

11 . The method of any of the preceding claims, comprising the wireless device receiving, from the base station, an acknowledgment for the RLC SDU, the acknowledgement being one of at least a positive acknowledgement and a negative acknowledgement, in response to the acknowledgement being a positive acknowledgement, the wireless device stopping the timer, and in response to the acknowledgement being a negative acknowledgement, the wireless device not stopping the timer.

12. The method of any of the preceding claims, comprising the wireless device receiving an indication that the RLC SDU is discarded, the wireless device stopping the timer in response to receiving an indication that the RLC SDU is discarded.

13. The method of any of the preceding claims, wherein the one or more conditions comprises a first condition that the RLC SDU becomes delay-critical.

14. The method of claim 13, wherein the RLC SDU becomes delay critical, if a remaining time of the RLC SDU becomes equal to or less than a first value, or if a first timer of the RLC SDU expires.

15. The method of claim 13 or 14, wherein the one or more configuration parameters comprises the first value indicating a first threshold.

16. The method of any of the preceding claims, comprising the wireless device starting the first timer with a first timer value, upon reception (or generation), by the wireless device, of the RLC SDU from an application of the wireless device.

17. The method of claim 16, wherein the one or more configuration parameters comprise the first timer value.

18. The method of claim 16 or 17, wherein a RLC entity of the wireless device starts the timer with the first timer value.

19. The method of any of claims 15-18, wherein the one or more configuration parameters comprises a second value indicating a second threshold, wherein a PDCP entity of the wireless device uses the second threshold value to determine whether a PDCP SDU associated with the RLC SDU is delay-critical PDCP SDU.

20. The method of any of the preceding claims, wherein the one or more conditions comprises a second condition that a timer of the RLC SDU is not running.

21. The method of any of the preceding claims, wherein the one or more conditions comprises a second condition that the timer of the RLC SDU is not running if the timer is not started after expiry of the timer.

22. The method of claim 20 or 21 , wherein the wireless device retransmits a RLC PDU of the RLC SDU if the first condition and the second condition are met.

23. The method of claim 22, wherein the RLC PDU comprises at least one of the RLC SDU or a RLC SDU segment, the RLC SDU segment comprising at least a portion of the RLC SDU.

24. The method of claims 13 and 21 , comprising the wireless device not retransmitting the RLC PDU if the first condition is met and the second condition is not met.

25. The method of any of the preceding claims, wherein the one or more conditions comprises a third condition that the wireless device receives a negative acknowledgement for the RLC SDU.

26. The method of claim 9 and 16 or 17 and claim 21 , comprising the wireless device retransmitting the RLC PDU, if the second condition is met and the third condition is met.

27. The method of claim 18 or 21 , comprising the wireless device retransmitting the RLC PDU, if the wireless device receives from the base station or is allocated by the base station an uplink resource, the uplink resource being scheduled for transmission of one or more RLC SDUs which is delay-critical.

28. The method of any of the preceding claims, wherein the one or more configuration parameters comprises a fourth value indicating a fourth threshold.

29. The method of any of the preceding claims, wherein the one or more conditions comprises a fourth condition that a remaining time of the RLC SDU is equal to or less than the fourth threshold.

30. The method of claim 28-29, comprising the wireless device retransmitting the RLC PDU, if the fourth condition is not met.

31 . The method of any of the preceding claims, wherein the one or more configuration parameters comprises a fifth value for a fifth timer.

32. The method of claim 31 , comprising the wireless device starting the fifth timer with the fifth value, when the wireless device receives the RLC SDU e.g. from an application.

33. The method of claim 32, wherein the remaining time of the RLC SDU is the remaining time of the fifth timer until expiry of the fifth timer.

34. A method comprising: sending, by a base station (BS) central unit (CU) to a BS distributed unit (DU), a request for one or more configuration parameters, comprising a radio link control (RLC) capability information indicating support of retransmission of one or more RLC protocol data unit (PDU) segments of a delay critical RLC service data unit (SDU); receiving, by the BS CU from the BS DU, one or more first configuration parameters configuring, the retransmission of the one or more RLC PDU segments; and sending, by the BS CU to a wireless device, the one or more configuration parameters.

35. A method comprising: receiving, by a base station (BS) distributed unit (DU) from a BS central unit (CU), a request for one or more configuration parameters, comprising a radio link control (RLC) capability information indicating support of retransmission of one or more RLC protocol data unit (PDU) segments of a delay critical RLC service data unit (SDU); sending, by the BS DU to the BS CU, one or more first configuration parameters configuring, the retransmission of the one or more RLC PDU segments; receiving, by the BS DU from the BS CU, a RLC SDU; and retransmitting, by the BS DU to a wireless device, one or more first RLC segments of the RLC SDU, in response to the RLC SDU being delay critical.

36. A method comprising: sending, by a wireless device to a base station, one or more parameter of one or more capabilities supported by the wireless device, the capabilities comprising a capability of retransmission of a delay critical radio link control (RLC) data unit (DU); receiving, by a wireless device from a base station, one or more configuration parameter of retransmission of a delay critical RLC DU; and receiving, by a wireless device from a base station, a medium access control (MAC) control element (CE) activating retransmission of a delay critical RLC DU.

37. A computer program product, storing instructions thereon which cause an apparatus to perform the steps of claims 1-36 when executed.

38. A wireless device comprising a receiver, a transmitter, a controller, and a storage unit storing instructions which when executed by the controller cause the wireless device to be configured to: receive or determine, by a wireless device, one or more configuration parameters, the one or more configuration parameters comprising an indication to retransmit a radio link control (RLC) service data unit (SDU) in response to the RLC SDU becoming delay-critical; and retransmit, by the wireless device, based on one or more conditions being met, the RLC SDU, after the RLC SDU becomes delay-critical.

39. A wireless device comprising a receiver, a transmitter, a controller, and a storage unit storing instructions which when executed by the controller cause the wireless device to be configured to: receive, by thewireless device from a base station, one or more configuration parameters, the one or more configuration parameters comprising a time value for a timer, the timer being defined to prohibit retransmission of a radio link control (RLC) service data unit (SDU); and retransmit, by the wireless device, the RLC SDU, based on determining: that the RLC SDU becomes delay-critical; and expiry of the timer of the RLC SDU.

40. A wireless device comprising a receiver, a transmitter, a controller, and a storage unit storing instructions which when executed by the controller cause the wireless device to be configured to: receive, by the wireless device from a base station, one or more configuration parameters, the one or more configuration parameters comprising a time value for a timer, the timer being defined to prohibit retransmission of a radio link control (RLC) service data unit (SDU); and retransmit, by the wireless device, the RLC SDU, based on determining: that the RLC SDU becomes delay-critical; and the timer of the RLC SDU is not running.

41. A base station (BS) central unit (CU) comprising a receiver, a transmitter, a controller, and a storage unit storing instructions which when executed by the controller cause the BS CU to be configured to: send, by the base station (BS) central unit (CU) to a BS distributed unit (DU), a request for one or more configuration parameters, comprising a radio link control (RLC) capability information indicating support of retransmission of one or more RLC protocol data unit (PDU) segments of a delay critical RLC service data unit (SDU); receive, by the BS CU from the BS DU, one or more first configuration parameters configuring, the retransmission of the one or more RLC PDU segments; and send, by the BS CU to a wireless device, the one or more configuration parameters.

42. A base station (BS) distributed unit (DU) comprising a receiver, a transmitter, a controller, and a storage unit storing instructions which when executed by the controller cause the BS DU to be configured to: receive, by the base station (BS) distributed unit (DU) from a BS central unit (CU), a request for one or more configuration parameters, comprising a radio link control (RLC) capability information indicating support of retransmission of one or more RLC protocol data unit (PDU) segments of a delay critical RLC service data unit (SDU); send, by the BS DU to the BS CU, one or more first configuration parameters configuring, the retransmission of the one or more RLC PDU segments; receive, by the BS DU from the BS CU, a RLC SDU; and retransmitting, by the BS DU to a wireless device, one or more first RLC segments of the RLC SDU, in response to the RLC SDU being delay critical.

43. A wireless device comprising a receiver, a transmitter, a controller, and a storage unit storing instructions which when executed by the controller cause the wireless device to be configured to: send, by the wireless device to a base station, one or more parameter of one or more capabilities supported by the wireless device, the capabilities comprising a capability of retransmission of a delay critical radio link control (RLC) data unit (DU); receive, by a wireless device from a base station, one or more configuration parameter of retransmission of a delay critical RLC DU; and receive, by a wireless device from a base station, a medium access control (MAC) control element (CE) activating retransmission of a delay critical RLC DU.