WO2024263227A1 - Inter-ue coordination (iuc) in unlicensed sidelink operation - Google Patents

Abstract

A method of sidelink communications includes receiving, by a first user equipment (UE), a list comprising preferred resources and non-preferred resources and initiating, by the first UE, one or more channel occupancy times (CoTs) based on the list.

Description

INTER-UE COORDINATION (IUC) IN UNLICENSED SIDELINK OPERATION

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority under 35 USC §119(e) from U.S. Provisional Patent Application No. 63/532, 199, filed on June 21, 2023 (“the provisional application”); the content of the provisional patent application is incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] The present invention is directed to 5G, which is the 5^th generation mobile network. It is a new global wireless standard after 1G, 2G, 3G, and 4G networks. 5G enables networks designed to connect machines, objects and devices.

[0003] The invention is more specifically directed to enhancing existing sidelink operations in unlicensed bands, i.e., enhancing sidelink operation for sidelink communications in unlicensed bands (SL-U) and channel occupancy time (CoT) sharing in reliance upon inter-user equipment (UE) coordination (IUC) and exchange of IUC information between UEs.

SUMMARY OF THE INVENTION

[0004] In an embodiment, the invention provides a method of sidelink communications includes receiving, by a first user equipment (UE), a list comprising preferred resources and non-preferred resources and initiating, by the first UE, one or more channel occupancy times (CoTs) based on the list. The method preferably includes enabling, by the first user equipment (UE), channel occupancy time (CoT) sharing with one or more second UEs based on the list. The first user equipment (UE) may receive the list from one or more second UEs. For that matter, the first user equipment (UE) may receive the list from a base station. The list can be based on inter-user equipment (UE) coordination (IUC) information. The first user equipment (UE) also may receive the list in response to a request.

[0005] In the method, the request may be for inter-user equipment (UE) coordination information (IUC). The request may be by the first user equipment (UE) from one or more second user equipments (UEs). The request may be by a base station from one or more second user equipment (UEs). The first user equipment (UE) may receive the list from the base station in response to the base station receiving inter-UE coordination (IUC) information from one or more second UEs. The interuser equipment (UE) coordination (IUC) information may be received by the base station from the one or more second UEs via a physical layer channel. The physical layer channel may be a physical uplink control channel (PUCCH). Preferably the inter-user equipment (UE) coordination (IUC) information is received by the base station from the one or more second UEs via a medium access control (MAC) control element (CE).

[0006] In the method, the inter-user equipment (UE) coordination (IUC) information may be received by the base station from the one or more second UEs via a radio resource control (RRC) message. The radio resource control (RRC) message may be a user equipment (UE) assistance information message. The list may be applicable to one or more sidelink radio bearers (SLRBs). The method can include receiving configuration parameters of the one or more sidelink radio bearers (SLRBs). The configuration parameters may comprise one or more first parameters indicating that the list is applicable to the one or more sidelink radio bearers (SLRBs) . The sidelink communications can be implemented according to a mode 1 sidelink operation. The first user equipment (UE) may determine resource allocation information for communications with one or more second UEs. The resource allocation information may be determined based on the list.

[0007] In the method, the sidelink communications may operate according to a mode 2 sidelink operation. In one form, a base station may determine resource allocation information for communications of the first user equipment (UE) with one or more second UEs. In another form, the method may include receiving, by the first user equipment (UE), the resource allocation information from the base station. The resource allocation information may be determined based on the list. And the method may further include performing one or more listen before talk (LET) processes, and wherein the initiating is based on the one or more LBT processes indicating clear channel.

[0008] In an embodiment, the invention provides a method of sidelink communications that includes transmitting, by a first user equipment (UE) to a second UE, first sidelink control information (SCI) indicating a first set of resources within one or more channel occupancy times (CoTs), receiving, by the first UE from the second UE, a message indicating a second set of resources that is a subset of the first set of resources, which are preferred or are not preferred, and initiating one or more CoTs based on the indication of the preferred or non-preferred resources. Preferably, the method includes enabling channel occupancy time (CoT) sharing on the second set of resources indicated as preferred resources or not indicated as non-preferred resources.

[0009] One or more channel occupancy times (CoTs) may be initiated on the second set of resources indicated as preferred resources or not indicated as non-preferred resources. The method may further include transmitting an updated sidelink control information (SCI) in response to receiving the second set. The updated sidelink control information (SCI) may indicate un-reserving resources that were reserved by the first SCI. The un-reserving can be at least for resources that are indicated as non- preferred. The second set may be received in response to one or more conditions being satisfied at the second user equipment (UE).

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] FIG. 1 shows an example of a system of mobile communications according to some aspects of some of various exemplary embodiments of the present disclosure.

[0011] FIG. 2A and FIG. 2B show examples of radio protocol stacks for user plane and control plane, respectively, according to some aspects of some of various exemplary embodiments of the present disclosure.

[0012] FIG. 3A, FIG. 3B and FIG. 3C show example mappings between logical channels and transport channels in downlink, uplink and sidelink, respectively, according to some aspects of some of various exemplary embodiments of the present disclosure.

[0013] FIG. 4A, FIG. 4B and FIG. 4C show example mappings between transport channels and physical channels in downlink, uplink and sidelink, respectively, according to some aspects of some of various exemplary embodiments of the present disclosure.

[0014] FIG. 5A, FIG. 5B, FIG. 5C and FIG. 5D show examples of radio protocol stacks for NR sidelink communication according to some aspects of some of various exemplary embodiments of the present disclosure.

[0015] FIG. 6 shows example physical signals in downlink, uplink and sidelink according to some aspects of some of various exemplary embodiments of the present disclosure.

[0016] FIG. 7 shows examples of Radio Resource Control (RRC) states and transitioning between different RRC states according to some aspects of some of various exemplary embodiments of the present disclosure. [0017] FIG. 8 shows example frame structure and physical resources according to some aspects of some of various exemplary embodiments of the present disclosure.

[0018] FIG. 9 shows example component carrier configurations in different carrier aggregation scenarios according to some aspects of some of various exemplary embodiments of the present disclosure.

[0019] FIG. 10 shows example bandwidth part configuration and switching according to some aspects of some of various exemplary embodiments of the present disclosure.

[0020] FIG. 11 shows example four-step contention-based and contention-free random access processes according to some aspects of some of various exemplary embodiments of the present disclosure.

[0021] FIG. 12 shows example two-step contention-based and contention- free random access processes according to some aspects of some of various exemplary embodiments of the present disclosure.

[0022] FIG. 13 shows example time and frequency structure of Synchronization Signal and Physical Broadcast Channel (PBCH) Block (SSB) according to some aspects of some of various exemplary embodiments of the present disclosure.

[0023] FIG. 14 shows example SSB burst transmissions according to some aspects of some of various exemplary embodiments of the present disclosure.

[0024] FIG. 15 shows example components of a user equipment and a base station for transmission and/or reception according to some aspects of some of various exemplary embodiments of the present disclosure.

[0025] FIG. 16 shows an example process of Direct IUC Scheme la/b signaling between Rx UEs and the Tx UE according to some aspects of some of various exemplary embodiments of the present disclosure. [0026] FIG. 17 shows an example process of Indirect IUC Scheme la/b signaling between Rx UEs and the Tx UE according to some aspects of some of various exemplary embodiments of the present disclosure.

[0027] FIG. 18 shows an example process of IUC Scheme 2 signaling for SL-U according to some aspects of some of various exemplary embodiments of the present disclosure.

[0028] FIG. 19 shows an example process according to some aspects of some of various exemplary embodiments of the present disclosure.

[0029] FIG. 20 shows an example process according to some aspects of some of various exemplary embodiments of the present disclosure.

DETAILED DESCRIPTION OF THE INVENTION

[0030] FIG. 1 shows an example of a system of mobile communications 100 according to some aspects of some of various exemplary embodiments of the present disclosure. The system of mobile communication 100 may be operated by a wireless communications system operator such as a Mobile Network Operator (MNO), a private network operator, a Multiple System Operator (MSO), an Internet of Things (IOT) network operator, etc., and may offer services such as voice, data (e.g., wireless Internet access), messaging, vehicular communications services such as Vehicle to Everything (V2X) communications services, safety services, mission critical service, services in residential, commercial or industrial settings such as loT, industrial IOT (HOT), etc.

[0031] The system of mobile communications 100 may enable various types of applications with different requirements in terms of latency, reliability, throughput, etc. Example supported applications include enhanced Mobile Broadband (eMBB), Ultra- Reliable Low- Latency Communications (URLLC), and massive Machine Type Communications (mMTC). eMBB may support stable connections with high peak data rates, as well as moderate rates for cell-edge users. URLLC may support applications with strict requirements in terms of latency and reliability and moderate requirements in terms of data rate. Example mMTC application includes a network of a massive number of loT devices, which are only sporadically active and send small data payloads.

[0032] The system of mobile communications 100 may include a Radio Access Network (RAN) portion and a core network portion. The example shown in FIG. 1 illustrates a Next Generation RAN (NG-RAN) 105 and a 5G Core Network (5GC) 110 as examples of the RAN and core network, respectively. Other examples of RAN and core network may be implemented without departing from the scope of this disclosure. Other examples of RAN include Evolved Universal Terrestrial Radio Access Network (EUTRAN), Universal Terrestrial Radio Access Network (UTRAN), etc. Other examples of core network include Evolved Packet Core (EPC), UMTS Core Network (UCN), etc. The RAN implements a Radio Access Technology⁷ (RAT) and resides between User Equipments (UEs) 125 and the core network. Examples of such RATs include New Radio (NR), Long Term Evolution (LTE) also known as Evolved Universal Terrestrial Radio Access (EUTRA), Universal Mobile Telecommunication System (UMTS), etc. The RAT of the example system of mobile communications 100 may be NR. The core network resides between the RAN and one or more external networks (e.g., data networks) and is responsible for functions such as mobility management, authentication, session management, setting up bearers and application of different Quality of Services (QoSs). The functional layer between the UE 125 and the RAN (e.g., the NG-RAN 105) may be referred to as Access Stratum (AS) and the functional layer between the UE 125 and the core network (e.g., the 5GC 110) may be referred to as Non-access Stratum (NAS).

[0033] The UEs 125 may include wireless transmission and reception means for communications with one or more nodes in the RAN, one or more relay nodes, or one or more other UEs, etc. Examples of UEs include, but are not limited to, smartphones, tablets, laptops, computers, wireless transmission and/or reception units in a vehicle, V2X or Vehicle to Vehicle (V2V) devices, wireless sensors, loT devices, HOT devices, etc. Other names may be used for UEs such as a Mobile Station (MS), terminal equipment, terminal node, client device, mobile device, etc.

[0034] The RAN may include nodes (e.g., base stations) for communications with the UEs. For example, the NG-RAN 105 of the system of mobile communications 100 may comprise nodes for communications with the UEs 125. Different names for the RAN nodes may be used, for example depending on the RAT used for the RAN. A RAN node may be referred to as Node B (NB) in a RAN that uses the UMTS RAT. A RAN node may be referred to as an evolved Node B (eNB) in a RAN that uses LTE/EUTRA RAT. For the illustrative example of the system of mobile communications 100 in FIG. 1, the nodes of an NG-RAN 105 may be either a next generation Node B (gNB) 115 or a next generation evolved Node B (ng-eNB) 120. In this specification, the terms base station, RAN node, gNB and ng-eNB may be used interchangeably. The gNB 115 may provide NR user plane and control plane protocol terminations towards the UE 125. The ng-eNB 120 may provide E-UTRA user plane and control plane protocol terminations towards the UE 125. An interface between the gNB 115 and the UE 125 or between the ng- eNB 120 and the UE 125 may be referred to as a Uu interface. The Uu interface may be established with a user plane protocol stack and a control plane protocol stack. For a Uu interface, the direction from the base station (e.g., the gNB 115 or the ng-eNB 120) to the UE 125 may be referred to as downlink and the direction from the UE 125 to the base station (e.g., gNB 115 or ng-eNB 120) may be referred to as uplink.

[0035] The gNBs 115 and ng-eNBs 120 may be interconnected with each other by means of an Xn interface. The Xn interface may comprise an Xn User plane (Xn-U) interface and an Xn Control plane (Xn-C) interface. The transport network layer of the Xn-U interface may be built on Internet Protocol (IP) transport and GPRS Tunneling Protocol (GTP) may be used on top of User Datagram Protocol (UDP)/IP to cariy the user plane protocol data units (PDUs). Xn-U may provide non-guaranteed delivery of user plane PDUs and may support data forwarding and flow control. The transport network layer of the Xn-C interface may be built on Stream Control Transport Protocol (SCTP) on top of IP. The application layer signaling protocol may be referred to as XnAP (Xn Application Protocol). The SCTP layer may provide the guaranteed delivery of application layer messages. In the transport IP layer, point-to- point transmission may be used to deliver the signaling PDUs. The Xn-C interface may support Xn interface management, UE mobility management, including context transfer and RAN paging, and dual connectivity.

[0036] The gNBs 115 and ng-eNBs 120 may also be connected to the 5GC 110 by means of the NG interfaces, more specifically to an Access and Mobility Management Function (AMF) 130 of the 5GC 110 by means of the NG-C interface and to a User Plane Function (UPF) 135 of the 5GC 110 by means of the NG-U interface. The transport network layer of the NG-U interface may be built on IP transport and GTP protocol may be used on top of UDP/IP to carry the user plane PDUs between the NG- RAN node (e.g., gNB 115 or ng-eNB 120 ) and the UPF 135. NG-U may provide non-guaranteed delivery of user plane PDUs between the NG- RAN node and the UPF. The transport network layer of the NG-C interface may be built on IP transport. For the reliable transport of signaling messages, SCTP may be added on top of IP. The application layer signaling protocol may be referred to as NGAP (NG Application Protocol). The SCTP layer may provide guaranteed delivery of application layer messages. In the transport, IP layer point-to-point transmission may be used to deliver the signaling PDUs. The NG-C interface may provide the following functions: NG interface management; UE context management; UE mobility management; transport of NAS messages; paging; PDU Session Management; configuration transfer; and warning message transmission.

[0037] The gNB 115 or the ng-eNB 120 may host one or more of the following functions: Radio Resource Management functions such as Radio Bearer Control, Radio Admission Control, Connection Mobility Control, Dynamic allocation of resources to UEs in both uplink and downlink (e.g., scheduling); IP and Ethernet header compression, encryption and integrity protection of data; Selection of an AMF at UE attachment when no routing to an AMF can be determined from the information provided by the UE; Routing of User Plane data towards UPF(s): Routing of Control Plane information towards AMF; Connection setup and release; Scheduling and transmission of paging messages; Scheduling and transmission of system broadcast information (e.g., originated from the AMF); Measurement and measurement reporting configuration for mobility and scheduling; Transport level packet marking in the uplink; Session Management; Support of Network Slicing; QoS Flow management and mapping to data radio bearers; Support of UEs in RRC Inactive state; Distribution function for NAS messages; Radio access network sharing; Dual Connectivity; Tight interworking between NR and E-UTRA; and Maintaining security and radio configuration for User Plane 5G system (5GS) Cellular loT (CIoT) Optimization.

[0038] The AMF 130 may host one or more of the following functions: NAS signaling termination; NAS signaling security; AS Security control; Inter CN node signaling for mobility between 3GPP access networks; Idle mode UE Reachability (including control and execution of paging retransmission); Registration Area management; Support of intra-system and inter-system mobility; Access Authentication; Access Authorization including check of roaming rights; Mobility management control (subscription and policies); Support of Network Slicing; Session Management Function (SMF) selection; Selection of 5GS CIoT optimizations.

[0039] The UPF 135 may host one or more of the following functions: Anchor point for Intra-/ Inter- RAT mobility (when applicable); External PDU session point of interconnect to Data Network; Packet routing & forwarding; Packet inspection and User plane part of Policy rule enforcement; Traffic usage reporting; Uplink classifier to support routing traffic flows to a data network; Branching point to support multi-homed PDU session; QoS handling for user plane, e.g. packet filtering, gating, UL/DL rate enforcement; Uplink Traffic verification (Service Data Flow (SDF) to QoS flow mapping); Downlink packet buffering and downlink data notification triggering.

[0040] As shown in FIG. 1, the NG-RAN 105 may support the PC5 interface between two UEs 125 (e.g., UE 125A and UE125B). In the PC5 interface, the direction of communications between two UEs (e.g., from UE 125A to UE 125B or vice versa) may be referred to as sidelink. Sidelink transmission and reception over the PC5 interface may be supported when the UE 125 is inside NG-RAN 105 coverage, irrespective of which RRC state the UE is in, and when the UE 125 is outside NG- RAN 105 coverage. Support of V2X services via the PC5 interface may be provided by NR sidelink communication and/or V2X sidelink communication .

[0041] PC5-S signaling may be used for unicast link establishment with Direct Communication Request/ Accept message. A UE may self-assign its source Layer-2 ID for the PC5 unicast link for example based on the V2X service type. During unicast link establishment procedure, the UE may send its source Layer-2 ID for the PC5 unicast link to the peer UE, e.g., the UE for which a destination ID has been received from the upper layers. A pair of source Layer-2 ID and destination Layer-2 ID may uniquely identify a unicast link. The receiving UE may verify that the said destination ID belongs to it and may accept the Unicast link establishment request from the source UE. During the PC5 unicast link establishment procedure, a PC5-RRC procedure on the Access Stratum may be invoked for the purpose of UE sidelink context establishment as well as for AS layer configurations, capability exchange etc. PC5-RRC signaling may enable exchanging UE capabilities and AS layer configurations such as Sidelink Radio Bearer configurations between pair of UEs for which a PC5 unicast link is established.

[0042] NR sidelink communication may support one of three types of transmission modes (e.g., Unicast transmission, Groupcast transmission, and Broadcast transmission) for a pair of a Source Layer-2 ID and a Destination Layer-2 ID in the AS. The Unicast transmission mode may be characterized by: Support of one PC5-RRC connection between peer UEs for the pair; Transmission and reception of control information and user traffic between peer UEs in sidelink; Support of sidelink HARQ feedback; Support of sidelink transmit power control; Support of RLC Acknowledged Mode (AM); and Detection of radio link failure for the PC5-RRC connection. The Groupcast transmission may be characterized by: Transmission and reception of user traffic among UEs belonging to a group in sidelink; and Support of sidelink HARQ feedback. The Broadcast transmission may be characterized by: Transmission and reception of user traffic among UEs in sidelink.

[0043] A Source Layer-2 ID, a Destination Layer-2 ID and a PC5 Link Identifier may be used for NR sidelink communication. The Source Layer- 2 ID may be a link-layer identity that identifies a device or a group of devices that are recipients of sidelink communication frames. The Destination Layer- 2 ID may be a link-layer identity that identifies a device that originates sidelink communication frames. In some examples, the Source Layer-2 ID and the Destination Layer-2 ID may be assigned by a management function in the Core Network. The Source Layer-2 ID may identify the sender of the data in NR sidelink communication. The Source Layer-2 ID may be 24 bits long and may be split in the MAC layer into two bit strings: One bit string may be the LSB part (8 bits) of Source Layer-2 ID and forwarded to physical layer of the sender. This may identify the source of the intended data in sidelink control information and may be used for filtering of packets at the physical layer of the receiver; and the Second bit string may be the MSB part (16 bits) of the Source Layer-2 ID and may be carried within the Medium Access Control (MAC) header. This may be used for filtering packets at the MAC layer of the receiver. The Destination Layer-2 ID may identify the target of the data in NR sidelink communication. For NR sidelink communication, the Destination Layer- 2 ID may be 24 bits long and may be split in the MAC layer into two bit strings: One bit string may be the LSB part (16 bits) of Destination Layer- 2 ID and forwarded to physical layer of the sender.

This may identify the target of the intended data in sidelink control information and may be used for filtering of packets at the physical layer of the receiver; and the Second bit string may be the MSB part (8 bits) of the Destination Layer-2 ID and may be carried within the MAC header. This may be used for filtering packets at the MAC layer of the receiver. The PC5 Link Identifier may uniquely identify the PC5 unicast link in a UE for the lifetime of the PC5 unicast link. The PC5 Link Identifier may be used to indicate the PC5 unicast link whose sidelink Radio Link failure (RLF) declaration was made and PC5-RRC connection was released.

[0044] FIG. 2A and FIG. 2B show examples of radio protocol stacks for user plane and control plane, respectively, according to some aspects of some of various exemplary⁷ embodiments of the present disclosure. As shown in FIG. 2A, the protocol stack for the user plane of the Uu interface (between the UE 125 and the gNB 115) includes Service Data Adaptation Protocol (SDAP) 201 and SDAP 211, Packet Data Convergence Protocol (PDCP) 202 and PDCP 212, Radio Link Control (RLC) 203 and RLC 213, MAC 204 and MAC 214 sublayers of layer 2 and Physical (PHY) 205 and PHY 215 layer (layer 1 also referred to as LI). [0045] The PHY 205 and PHY 215 offer transport channels 244 to the MAC 204 and MAC 214 sublayer. The MAC 204 and MAC 214 sublayer offer logical channels 243 to the RLC 203 and RLC 213 sublayer. The RLC 203 and RLC 213 sublayer offer RLC channels 242 to the PDCP 202 and PCP 212 sublayer. The PDCP 202 and PDCP 212 sublayer offer radio bearers 241 to the SDAP 201 and SDAP 211 sublayer. Radio bearers may be categorized into two groups: Data Radio Bearers (DRBs) for user plane data and Signaling Radio Bearers (SRBs) for control plane data. The SDAP 201 and SDAP 211 sublayer offers QoS flows 240 to 5GC.

[0046] The main services and functions of the MAC 204 or MAC 214 sublayer include: mapping between logical channels and transport channels; Multiplexing/ demultiplexing of MAC Service Data Units (SDUs) belonging to one or different logical channels into / from Transport Blocks (TB) delivered to/from the physical layer on transport channels;

Scheduling information reporting; Error correction through Hybrid Automatic Repeat Request (HARQ) (one HARQ entity per cell in case of carrier aggregation (CA)); Priority handling between UEs by means of dynamic scheduling; Priority handling between logical channels of one UE by means of Logical Channel Prioritization (LCP); Priority handling between overlapping resources of one UE; and Padding. A single MAC entity may support multiple numerologies, transmission timings and cells. Mapping restrictions in logical channel prioritization control which numerology(ies), cell(s), and transmission timing(s) a logical channel may use.

[0047] The HARQ functionality may ensure delivery between peer entities at Layer 1. A single HARQ process may support one TB when the physical layer is not configured for downlink/uplink spatial multiplexing, and when the physical layer is configured for downlink/uplink spatial multiplexing, a single HARQ process may support one or multiple TBs.

[0048] The RLC 203 or RLC 213 sublayer may support three transmission modes: Transparent Mode (TM); Unacknowledged Mode (UM); and Acknowledged Mode (AM). The RLC configuration may be 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.

[0049] The main services and functions of the RLC 203 or RLC 213 sublayer depend on the transmission mode (e.g., TM, UM or AM) and may include: Transfer of upper layer PDUs; Sequence numbering independent of the one in PDCP (UM and AM); Error Correction through ARQ (AM only); Segmentation (AM and UM) and re-segmentation (AM only) of RLC SDUs; Reassembly of SDU (AM and UM); Duplicate Detection (AM only); RLC SDU discard (AM and UM); RLC reestablishment; and Protocol error detection (AM only).

[0050] The automatic repeat request within the RLC 203 or RLC 213 sublayer may have the following characteristics: ARQ retransmits RLC SDUs or RLC SDU segments based on RLC status reports; Polling for RLC status report may be used when needed by RLC; RLC receiver may also trigger RLC status report after detecting a missing RLC SDU or RLC SDU segment.

[0051] The main services and functions of the PDCP 202 or PDCP 212 sublayer may include: Transfer of data (user plane or control plane); Maintenance of PDCP Sequence Numbers (SNs); Header compression and decompression using the Robust Header Compression (ROHC) protocol; Header compression and decompression using EHC protocol; Ciphering and deciphering; Integrity protection and integrity verification; Timer based SDU discard; Routing for split bearers; Duplication; Reordering and in-order delivery; Out-of-order delivery; and Duplicate discarding.

[0052] The main services and functions of SDAP 201 or SDAP 211 include: Mapping between a QoS flow and a data radio bearer; and Marking QoS Flow ID (QFI) in both downlink and uplink packets. A single protocol entity of SDAP may be configured for each individual PDU session.

[0053] As shown in FIG. 2B, the protocol stack of the control plane of the Uu interface (between the UE 125 and the gNB 1 15) includes PHY layer (layer 1), and MAC, RLC and PDCP sublayers of layer 2 as described above and in addition, the RRC 206 sublayer and RRC 216 sublayer. The main services and functions of the RRC 206 sublayer and the RRC 216 sublayer over the Uu interface include: Broadcast of System Information related to AS and NAS; Paging initiated by 5GC or NG-RAN;

Establishment, maintenance and release of an RRC connection between the UE and NG-RAN (including Addition, modification and release of carrier aggregation; and Addition, modification and release of Dual Connectivity in NR or between E-UTRA and NR); Security functions including key management; Establishment, configuration, maintenance and release of SRBs and DRBs; Mobility functions (including Handover and context transfer; UE cell selection and reselection and control of cell selection and reselection; and Inter-RAT mobility); QoS management functions; UE measurement reporting and control of the reporting;

Detection of and recovery from radio link failure; and NAS message transfer to/from NAS from/to UE. The NAS 207 and NAS 227 layer is a control protocol (terminated in AMF on the network side) that performs the functions such as authentication, mobility management, security control, etc.

[0054] The sidelink specific services and functions of the RRC sublayer over the Uu interface include: Configuration of sidelink resource allocation via system information or dedicated signaling; Reporting of UE sidelink information; Measurement configuration and reporting related to sidelink; and Reporting of UE assistance information for SL traffic pattern (s).

[0055] FIG. 3A, FIG. 3B and FIG. 3C show example mappings between logical channels and transport channels in downlink, uplink and sidelink, respectively, according to some aspects of some of various exemplary embodiments of the present disclosure. Different kinds of data transfer services may be offered by MAC. Each logical channel type may be defined by what type of information is transferred. Logical channels may be classified into two groups: Control Channels and Traffic Channels. Control channels may be used for the transfer of control plane information only. The Broadcast Control Channel (BCCH) is a downlink channel for broadcasting system control information. The Paging Control Channel (PCCH) is a downlink channel that carries paging messages. The Common Control Channel (CCCH) is channel for transmitting control information between UEs and networks. This channel may be used for UEs having no RRC connection with the network. The Dedicated Control Channel (DCCH) is a point-to-point bi-directional channel that transmits dedicated control information between a UE and the network and may be used by UEs having an RRC connection. Traffic channels may be used for the transfer of user plane information only. The Dedicated Traffic Channel (DTCH) is a point-to-point channel, dedicated to one UE, for the transfer of user information. A DTCH may exist in both uplink and downlink. Sidelink Control Channel (SCCH) is a sidelink channel for transmitting control information (e.g., PC5-RRC and PC5-S messages) from one UE to other UE(s). Sidelink Traffic Channel (STCH) is a sidelink channel for transmitting user information from one UE to other UE(s).

Sidelink Broadcast Control Channel (SBCCH) is a sidelink channel for broadcasting sidelink system information from one UE to other UE(s).

[0056] The downlink transport channel types include Broadcast Channel (BCH), Downlink Shared Channel (DL-SCH), and Paging Channel (PCH). The BCH may be characterized by: fixed, pre-defined transport format; and requirement to be broadcast in the entire coverage area of the cell, either as a single message or by beamforming different BCH instances. The DL-SCH may be characterized by: support for HARQ; support for dynamic link adaptation by vaiying the modulation, coding and transmit power; possibility to be broadcast in the entire cell; possibility to use beamforming; support for both dynamic and semi- static resource allocation; and the support for UE Discontinuous Reception (DRX) to enable UE power saving. The DL-SCH may be characterized by: support for HARQ; support for dynamic link adaptation by varying the modulation, coding and transmit power; possibility to be broadcast in the entire cell; possibility to use beamforming; support for both dynamic and semi-static resource allocation; support for UE discontinuous reception (DRX) to enable UE power saving. The PCH may be characterized by: support for UE discontinuous reception (DRX) to enable UE power saving (DRX cycle is indicated by the network to the UE); requirement to be broadcast in the entire coverage area of the cell, either as a single message or by beamforming different BCH instances; mapped to physical resources which can be used dynamically also for traffic/ other control channels.

[0057] In downlink, the following connections between logical channels and transport channels may exist: BCCH may be mapped to BCH; BCCH may be mapped to DL-SCH; PCCH may be mapped to PCH; CCCH may be mapped to DL-SCH; DCCH may be mapped to DL-SCH; and DTCH may be mapped to DL-SCH.

[0058] The uplink transport channel types include Uplink Shared Channel (UL-SCH) and Random Access Channel(s) (RACH). The UL-SCH may be characterized by possibility to use beamforming; support for dynamic link adaptation by varying the transmit power and potentially modulation and coding; support for HARQ; support for both dynamic and semi- static resource allocation. The RACH may be characterized by limited control information; and collision risk.

[0059] In Uplink, the following connections between logical channels and transport channels may exist: CCCH may be mapped to UL-SCH; DCCH may be mapped to UL- SCH; and DTCH may be mapped to UL-SCH. [0060] The sidelink transport channel types include: Sidelink broadcast channel (SL-BCH) and Sidelink shared channel (SL-SCH). The SL-BCH may be characterized by pre-defined transport format. The SL-SCH may be characterized by support for unicast transmission, groupcast transmission and broadcast transmission; support for both UE autonomous resource selection and scheduled resource allocation by NG-RAN; support for both dynamic and semi-static resource allocation when UE is allocated resources by the NG-RAN; support for HARQ; and support for dynamic link adaptation by varying the transmit power, modulation and coding.

[0061] In the sidelink, the following connections between logical channels and transport channels may exist: SCCH may be mapped to SL-SCH; STCH may be mapped to SL-SCH; and SBCCH may be mapped to SL- BCH.

[0062] FIG. 4A, FIG. 4B and FIG. 4C show example mappings between transport channels and physical channels in downlink, uplink and sidelink, respectively, according to some aspects of some of various exemplary embodiments of the present disclosure. The physical channels in downlink include Physical Downlink Shared Channel (PDSCH), Physical Downlink Control Channel (PDCCH) and Physical Broadcast Channel (PBCH). The PCH and DL-SCH transport channels are mapped to the PDSCH. The BCH transport channel is mapped to the PBCH. A transport channel is not mapped to the PDCCH but Downlink Control Information (DCI) is transmitted via the PDCCH.

[0063] The physical channels in the uplink include Physical Uplink Shared Channel (PUSCH), Physical Uplink Control Channel (PUCCH) and Physical Random Access Channel (PRACH). The UL-SCH transport channel may be mapped to the PUSCH and the RACH transport channel may be mapped to the PRACH. A transport channel is not mapped to the PUCCH but Uplink Control Information (UCI) is transmitted via the PUCCH. [0064] The physical channels in the sidelink include Physical Sidelink Shared Channel (PSSCH), Physical Sidelink Control Channel (PSCCH), Physical Sidelink Feedback Channel (PSFCH) and Physical Sidelink Broadcast Channel (PSBCH). The Physical Sidelink Control Channel (PSCCH) may indicate resource and other transmission parameters used by a UE for PSSCH. The Physical Sidelink Shared Channel (PSSCH) may transmit the TBs of data themselves, and control information for HARQ procedures and CSI feedback triggers, etc. At least 6 OFDM symbols within a slot may be used for PSSCH transmission. Physical Sidelink Feedback Channel (PSFCH) may carry the HARQ feedback over the sidelink from a UE which is an intended recipient of a PSSCH transmission to the UE which performed the transmission. PSFCH sequence may be transmitted in one PRB repeated over two OFDM symbols near the end of the sidelink resource in a slot. The SL-SCH transport channel may be mapped to the PSSCH. The SL-BCH may be mapped to PSBCH. No transport channel is mapped to the PSFCH but Sidelink Feedback Control Information (SFCI) may be mapped to the PSFCH. No transport channel is mapped to PSCCH but Sidelink Control Information (SCI) may be mapped to the PSCCH.

[0065] FIG. 5A, FIG. 5B, FIG. 5C and FIG. 5D show examples of radio protocol stacks for NR sidelink communication according to some aspects of some of various exemplary embodiments of the present disclosure. The AS protocol stack for user plane in the PC5 interface (i.e., for STCH) may consist of SDAP, PDCP, RLC and MAC sublayers, and the physical layer. The protocol stack of user plane is shown in FIG. 5A. The AS protocol stack for SBCCH in the PC5 interface may consist of RRC, RLC, MAC sublayers, and the physical layer as shown below in FIG. 5B. For support of PC5-S protocol, PC5-S is located on top of PDCP, RLC and MAC sublayers, and the physical layer in the control plane protocol stack for SCCH for PC5-S, as shown in FIG. 5C. The AS protocol stack for the control plane for SCCH for RRC in the PC5 interface consists of RRC, PDCP, RLC and MAC sublayers, and the physical layer. The protocol stack of control plane for SCCH for RRC is shown in FIG. 5D.

[0066] The Sidelink Radio Bearers (SLRBs) may be categorized into two groups: Sidelink Data Radio Bearers (SL DRB) for user plane data and Sidelink Signaling Radio Bearers (SL SRB) for control plane data. Separate SL SRBs using different SCCHs may be configured for PC5-RRC and PC5-S signaling, respectively.

[0067] The MAC sublayer may provide the following services and functions over the PC5 interface: Radio resource selection; Packet filtering; Priority handling between uplink and sidelink transmissions for a given UE; and Sidelink CSI reporting. With logical channel prioritization restrictions in MAC, only sidelink logical channels belonging to the same destination may be multiplexed into a MAC PDU for every unicast, groupcast and broadcast transmission which may be associated to the destination. For packet filtering, a SL-SCH MAC header including portions of both Source Layer-2 ID and a Destination Layer-2 ID may be added to a MAC PDU. The Logical Channel Identifier (LCID) included within a MAC subheader may uniquely identify a logical channel within the scope of the Source Layer-2 ID and Destination Layer-2 ID combination.

[0068] The services and functions of the RLC sublayer may be supported for sidelink. Both RLC Unacknowledged Mode (UM) and Acknowledged Mode (AM) may be used in unicast transmission while only UM may be used in groupcast or broadcast transmission. For UM, only unidirectional transmission may be supported for groupcast and broadcast.

[0069] The services and functions of the PDCP sublayer for the Uu interface may be supported for sidelink with some restrictions: Out-of- order delivery may be supported only for unicast transmission; and Duplication may not be supported over the PC5 interface. [0070] The SDAP sublayer may provide the following service and function over the PC5 interface: Mapping between a QoS flow and a sidelink data radio bearer. There may be one SDAP entity per destination for one of unicast, groupcast and broadcast which is associated to the destination.

[0071] The RRC sublayer may provide the following services and functions over the PC5 interface: Transfer of a PC5-RRC message between peer UEs; Maintenance and release of a PC5-RRC connection between two UEs; and Detection of sidelink radio link failure for a PC5-RRC connection based on indication from MAC or RLC. A PC5-RRC connection may be a logical connection between two UEs for a pair of Source and Destination Layer-2 IDs which may be considered to be established after a corresponding PC5 unicast link is established. There may be one-to-one correspondence between the PC5-RRC connection and the PC5 unicast link. A UE may have multiple PC5-RRC connections with one or more UEs for different pairs of Source and Destination Layer-2 IDs. Separate PC5-RRC procedures and messages may be used for a UE to transfer UE capability and sidelink configuration including SL-DRB configuration to the peer UE. Both peer UEs may exchange their own UE capability and sidelink configuration using separate bi-directional procedures in both side link directions.

[0072] FIG. 6 shows example physical signals in downlink, uplink and sidelink according to some aspects of some of various exemplary embodiments of the present disclosure. The Demodulation Reference Signal (DM-RS) may be used in downlink, uplink and sidelink and may be used for channel estimation. DM-RS is a UE-specific reference signal and may be transmitted together with a physical channel in downlink, uplink or sidelink and may be used for channel estimation and coherent detection of the physical channel. The Phase Tracking Reference Signal (PT-RS) may be used in downlink, uplink and sidelink and may be used for tracking the phase and mitigating the performance loss due to phase noise. The PT-RS may be used mainly to estimate and minimize the effect of Common Phase Error (CPE) on system performance. Due to the phase noise properties, PT-RS signal may have a low density in the frequency domain and a high density in the time domain. PT-RS may occur in combination with DM-RS and when the network has configured PT-RS to be present. The Positioning Reference Signal (PRS) may be used in downlink for positioning using different positioning techniques. PRS may be used to measure the delays of the downlink transmissions by correlating the received signal from the base station with a local replica in the receiver. The Channel State Information Reference Signal (CSI-RS) may be used in downlink and sidelink. CSI-RS may be used for channel state estimation, Reference Signal Received Power (RSRP) measurement for mobility and beam management, time /frequency tracking for demodulation among other uses. CSI-RS may be configured UE- specifically but multiple users may share the same CSI-RS resource. The UE may determine CSI reports and transmit them in the uplink to the base station using PUCCH or PUSCH. The CSI report may be carried in a sidelink MAC CE. The Primary Synchronization Signal (PSS) and the Secondary Synchronization Signal (SSS) may be used for radio fame synchronization. The PSS and SSS may be used for the cell search procedure during the initial attachment or for mobility purposes. The Sounding Reference Signal (SRS) may be used in uplink for uplink channel estimation. Similar to CSI-RS, the SRS may serve as QCL reference for other physical channels such that they can be configured and transmitted quasi-collocated with SRS. The Sidelink PSS (S-PSS) and Sidelink SSS (S-SSS) may be used in sidelink for sidelink synchronization .

[0073] FIG. 7 shows examples of Radio Resource Control (RRC) states and transitioning between different RRC states according to some aspects of some of various exemplary embodiments of the present disclosure. A UE may be in one of three RRC states: RRC Connected State 710, RRC Idle State 720 and RRC Inactive state 730. After power up, the UE may be in RRC Idle state 720 and the UE may establish connection with the network using initial access and via an RRC connection establishment procedure to perform data transfer and/or to make/receive voice calls. Once RRC connection is established, the UE may be in RRC Connected State 710. The UE may transition from the RRC Idle state 720 to the RRC connected state 710 or from the RRC Connected State 710 to the RRC Idle state 720 using the RRC connection Establishment/ Release procedures 740.

[0074] To reduce the signaling load and the latency resulting from frequent transitioning from the RRC Connected State 710 to the RRC Idle State 720 when the UE transmits frequent small data, the RRC Inactive State 730 may be used. In the RRC Inactive State 730, the AS context may be stored by both UE and gNB. This may result in faster state transition from the RRC Inactive State 730 to RRC Connected State 710. The UE may transition from the RRC Inactive State 730 to the RRC Connected State 710 or from the RRC Connected State 710 to the RRC Inactive State 730 using the RRC Connection Resume/ Inactivation procedures 760. The UE may transition from the RRC Inactive State 730 to RRC Idle State 720 using an RRC Connection Release procedure 750.

[0075] FIG. 8 shows example frame structure and physical resources according to some aspects of some of various exemplary embodiments of the present disclosure. The downlink or uplink or sidelink transmissions may be organized into frames with 10 ms duration, consisting of ten 1 ms subframes. Each subframe may consist of 1, 2, 4, ... slots, wherein the number of slots per subframe may depend on the subcarrier spacing of the carrier on which the transmission takes place. The slot duration may be 14 symbols with Normal Cyclic Prefix (CP) and 12 symbols with Extended CP and may scale in time as a function of the used sub-carrier spacing so that there is an integer number of slots in a subframe. FIG. 8 shows a resource grid in time and frequency domain. Each element of the resource grid, comprising one symbol in time and one subcarrier in frequency, is referred to as a Resource Element (RE). A Resource Block (RB) may be defined as 12 consecutive subcarriers in the frequency domain.

[0076] In some examples and with non-slot-based scheduling, the transmission of a packet may occur over a portion of a slot, for example during 2, 4 or 7 OFDM symbols which may also be referred to as minislots. The mini- slots may be used for low latency applications such as URLLC and operation in unlicensed bands. In some embodiments, the mini-slots may also be used for fast flexible scheduling of services (e.g., pre-emption of URLLC over eMBB).

[0077] FIG. 9 shows example component carrier configurations in different carrier aggregation scenarios according to some aspects of some of various exemplary embodiments of the present disclosure. In Carrier Aggregation (CA), two or more Component Carriers (CCs) may be aggregated. A UE may simultaneously receive or transmit on one or multiple CCs depending on its capabilities. CA may be supported for both contiguous and non-contiguous CCs in the same band or on different bands as shown in FIG. 9. A gNB and the UE may communicate using a serving cell. A serving cell may be associated with at least with one downlink CC (e.g., may be associated only with one downlink CC or may be associated with a downlink CC and an uplink CC). A serving cell may be a Primary Cell (PCell) or a Secondaiy cCell (SCell).

[0078] A UE may adjust the timing of its uplink transmissions using an uplink timing control procedure. A Timing Advance (TA) may be used to adjust the uplink frame timing relative to the downlink frame timing. The gNB may determine the desired Timing Advance setting and provides that to the UE. The UE may use the provided TA to determine its uplink transmit timing relative to the UE's observed downlink receive timing.

[0079] In the RRC Connected state, the gNB may be responsible for maintaining the timing advance to keep the LI synchronized. Serving cells having uplink to which the same timing advance applies and using the same timing reference cell are grouped in a Timing Advance Group (TAG) . A TAG may contain at least one serving cell with configured uplink. The mapping of a serving cell to a TAG may be configured by RRC. For the primary TAG, the UE may use the PCell as timing reference cell, except with shared spectrum channel access where an SCell may also be used as timing reference cell in certain cases. In a secondary TAG, the UE may use any of the activated SCells of this TAG as a timing reference cell and may not change it unless necessary.

[0080] Timing advance updates may be signaled by the gNB to the UE via MAC CE commands. Such commands may restart a TAG-specific timer which may indicate whether the LI can be synchronized or not: when the timer is running, the LI may be considered synchronized, otherwise, the LI may be considered non-synchronized (in which case uplink transmission may only take place on PRACH).

[0081] A UE with single timing advance capability for CA may simultaneously receive and/or transmit multiple CCs corresponding to multiple serving cells sharing the same timing advance (multiple serving cells grouped in one TAG). A UE with multiple timing advance capability for CA may simultaneously receive and/or transmit on multiple CCs corresponding to multiple serving cells with different timing advances (multiple serving cells grouped in multiple TAGs). The NG-RAN may ensure that each TAG contains at least one serving cell. A non-CA capable UE may receive on a single CC and may transmit on a single CC corresponding to one serving cell only (one serving cell in one TAG).

[0082] The multi-carrier nature of the physical layer in case of CA may be exposed to the MAC layer and one HARQ entity may be required per serving cell. When CA is configured, the UE may have one RRC connection with the network. At RRC connection establishment/ reestablishment/ handover, one serving cell (e.g., the PCell) may provide the NAS mobility information. Depending on UE capabilities, SCells may be configured to form together with the PCell a set of serving cells. The configured set of serving cells for a UE may consist of one PCell and one or more SCells. The reconfiguration, addition and removal of SCells may be performed by RRC.

[0083] In a dual connectivity scenario, a UE may be configured with a plurality of cells comprising a Master Cell Group (MCG) for communications with a master base station, a Secondary Cell Group (SCG) for communications with a secondary base station, and two MAC entities: one MAC entity and for the MCG for communications with the master base station and one MAC entity for the SCG for communications with the secondary base station.

[0084] FIG. 10 shows example bandwidth part configuration and switching according to some aspects of some of various exemplary embodiments of the present disclosure. The UE may be configured with one or more Bandwidth Parts (BWPs) 1010 on a given component carrier. In some examples, one of the one or more bandwidth parts may be active at a time. The active bandwidth part may define the UE's operating bandwidth within the cell's operating bandwidth. For initial access, and until the UE's configuration in a cell is received, initial bandwidth part 1020 determined from system information may be used. With Bandwidth Adaptation (BA), for example through BWP switching 1040, the receive and transmit bandwidth of a UE may not be as large as the bandwidth of the cell and may be adjusted. For example, the width may be ordered to change (e.g., to shrink during period of low activity to save power); the location may move in the frequency domain (e.g., to increase scheduling flexibility); and the subcarrier spacing may be ordered to change (e.g., to allow different services). The first active BWP 1020 may be the active BWP upon RRC (re-) configuration for a PCell or activation of an SCell.

[0085] For a downlink BWP or uplink BWP in a set of downlink BWPs or uplink BWPs, respectively, the UE may be provided the following configuration parameters: a Subcarrier Spacing (SCS); a cyclic prefix; a common RB and a number of contiguous RBs; an index in the set of downlink BWPs or uplink BWPs by respective BWP-Id; a set of BWP- common and a set of BWP-dedicated parameters. A BWP may be associated with an OFDM numerology according to the configured subcarrier spacing and cyclic prefix for the BWP. For a serving cell, a UE may be provided by a default downlink BWP among the configured downlink BWPs. If a UE is not provided a default downlink BWP, the default downlink BWP may be the initial downlink BWP.

[0085] A downlink BWP may be associated with a BWP inactivity timer. If the BWP inactivity timer associated with the active downlink BWP expires and if the default downlink BWP is configured, the UE may perform BWP switching to the default BWP. If the BWP inactivity timer associated with the active downlink BWP expires and if the default downlink BWP is not configured, the UE may perform BWP switching to the initial downlink BWP.

[0087] FIG. 11 shows example four-step contention-based and contention-free random access processes according to some aspects of some of various exemplary embodiments of the present disclosure. FIG. 12 shows example two-step contention-based and contention-free random access processes according to some aspects of some of various exemplary embodiments of the present disclosure. The random access procedure may be triggered by a number of events, for example: Initial access from RRC Idle State; RRC Connection Re-establishment procedure; downlink or uplink data arrival during RRC Connected State when uplink synchronization status is "non-synchronized"; uplink data arrival during RRC Connected State when there are no PUCCH resources for Scheduling Request (SR) available; SR failure; Request by RRC upon synchronous reconfiguration (e.g. handover); Transition from RRC Inactive State; to establish time alignment for a secondary TAG; Request for Other System Information (SI); Beam Failure Recoveiy (BFR);

Consistent uplink Listen-Before -Talk (LBT) failure on PCell. [0088] Two types of Random Access (RA) procedure may be supported: 4- step RA type with MSG1 and 2-step RA type with MSGA. Both types of RA procedure may support Contention-Based Random Access (CBRA) and Contention- Free Random Access (CFRA) as shown in FIG. 11 and FIG. 12.

[0089] The UE may select the type of random access at initiation of the random access procedure based on network configuration. When CFRA resources are not configured, an RSRP threshold may be used by the UE to select between 2-step RA type and 4-step RA type. When CFRA resources for 4-step RA type are configured, UE may perform random access with 4-step RA type. When CFRA resources for 2-step RA type are configured, UE may perform random access with 2-step RA type.

[0090] The MSG1 of the 4-step RA type may consist of a preamble on PRACH. After MSG1 transmission, the UE may monitor for a response from the network within a configured window. For CFRA, dedicated preamble for MSG1 transmission may be assigned by the network and upon receiving Random Access Response (RAR) from the network, the UE may end the random access procedure as shown in FIG. 11. For CBRA, upon reception of the random access response, the UE may send MSG3 using the uplink grant scheduled in the random access response and may monitor contention resolution as shown in FIG. 11. If contention resolution is not successful after MSG3 (re)transmission(s), the UE may go back to MSG1 transmission.

[0091] The MSGA of the 2-step RA type may include a preamble on PRACH and a payload on PUSCH. After MSGA transmission, the UE may monitor for a response from the network within a configured window. For CFRA, dedicated preamble and PUSCH resource may be configured for MSGA transmission and upon receiving the network response, the UE may end the random access procedure as shown in FIG. 12. For CBRA, if contention resolution is successful upon receiving the network response, the UE may end the random access procedure as shown in FIG. 12; while if fallback indication is received in MSGB, the UE may perform MSG3 transmission using the uplink grant scheduled in the fallback indication and may monitor contention resolution. If contention resolution is not successful after MSG3 (re)transmission(s), the UE may go back to MSGA transmission.

[0092] FIG. 13 shows example time and frequency structure of Synchronization Signal and Physical Broadcast Channel (PBCH) Block (SSB) according to some aspects of some of various exemplary embodiments of the present disclosure. The SS/PBCH Block (SSB) may consist of Primary and Secondary Synchronization Signals (PSS, SSS), each occupying 1 symbol and 127 subcarriers (e.g., subcarrier numbers 56 to 182 in FIG. 13), and PBCH spanning across 3 OFDM symbols and 240 subcarriers, but on one symbol leaving an unused part in the middle for SSS as show in FIG. 13. The possible time locations of SSBs within a half-frame may be determined by sub-carrier spacing and the periodicity of the half-frames, where SSBs are transmitted, may be configured by the network. During a half-frame, different SSBs may be transmitted in different spatial directions (i.e., using different beams, spanning the coverage area of a cell).

[0093] The PBCH may be used to carry Master Information Block (MIB) used by a UE during cell search and initial access procedures. The UE may first decode PBCH /MIB to receive other system information. The MIB may provide the UE with parameters required to acquire System Information Block 1 (SIB1), more specifically, information required for monitoring of PDCCH for scheduling PDSCH that carries SIB 1. In addition, MIB may indicate cell barred status information. The MIB and SIB 1 may be collectively referred to as the minimum system information (SI) and SIB1 may be referred to as remaining minimum system information (RMSI). The other system information blocks (SIBs) (e.g., SIB2, SIB3, ..., SIB 10 and SIBpos) may be referred to as Other SI. The Other SI may be periodically broadcast on DL-SCH, broadcast on- demand on DL-SCH (e.g., upon request from UEs in RRC Idle State, RRC Inactive State, or RRC connected State), or sent in a dedicated manner on DL-SCH to UEs in RRC Connected State (e.g., upon request, if configured by the network, from UEs in RRC Connected State or when the UE has an active BWP with no common search space configured).

[0094] FIG. 14 shows example SSB burst transmissions according to some aspects of some of various exemplary embodiments of the present disclosure. An SSB burst may include N SSBs and each SSB of the N SSBs may correspond to a beam. The SSB bursts may be transmitted according to a periodicity (e.g., SSB burst period). During a contentionbased random access process, a UE may perform a random access resource selection process, wherein the UE first selects an SSB before selecting a RA preamble. The UE may select an SSB with an RSRP above a configured threshold value. In some embodiments, the UE may select any SSB if no SSB with RSRP above the configured threshold is available. A set of random access preambles may be associated with an SSB. After selecting an SSB, the UE may select a random access preamble from the set of random access preambles associated with the SSB and may transmit the selected random access preamble to start the random access process.

[0095] In some embodiments, a beam of the N beams may be associated with a CSI-RS resource. A UE may measure CSI-RS resources and may select a CSI-RS with RSRP above a configured threshold value. The UE may select a random access preamble corresponding to the selected CSI- RS and may transmit the selected random access process to start the random access process. If there is no random access preamble associated with the selected CSI-RS, the UE may select a random access preamble corresponding to an SSB which is Quasi-Collocated with the selected CSI-RS.

[0096] In some embodiments, based on the UE measurements of the CSI-

RS resources and the UE CSI reporting, the base station may determine a Transmission Configuration Indication (TCI) state and may indicate the TCI state to the UE, wherein the UE may use the indicated TCI state for reception of downlink control information (e.g., via PDCCH) or data (e.g., via PDSCH). The UE may use the indicated TCI state for using the appropriate beam for reception of data or control information. The indication of the TCI states may be using RRC configuration or in combination of RRC signaling and dynamic signaling (e.g., via a MAC Control element (MAC CE) and/or based on a value of field in the downlink control information that schedules the downlink transmission). The TCI state may indicate a Quasi-Colocation (QCL) relationship between a downlink reference signal such as CSI-RS and the DM-RS associated with the downlink control or data channels (e.g., PDCCH or PDSCH, respectively).

[0097] In some embodiments, the UE may be configured with a list of up to M TCI-State configurations, using Physical Downlink Shared Channel (PDSCH) configuration parameters, to decode PDSCH according to a detected PDCCH with DCI intended for the UE and the given serving cell, where M may depend on the UE capability. Each TCI-State may contain parameters for configuring a QCL relationship between one or two downlink reference signals and the DM-RS ports of the PDSCH, the DM- RS port of PDCCH or the CSI-RS port(s) of a CSI-RS resource. The quasi co-location relationship may be configured by one or more RRC parameters. The quasi co-location types corresponding to each DL RS may take one of the following values: 'QCL-TypeA': {Doppler shift, Doppler spread, average delay, delay spread}; ’QCL-TypeB': {Doppler shift, Doppler spread}; 'QCL-TypeC: {Doppler shift, average delay}; 'QCL- TypeD': {Spatial Rx parameter}. The UE may receive an activation command (e.g., a MAC CE), used to map TCI states to the codepoints of a DCI field.

[0098] FIG. 15 shows example components of a user equipment and a base station for transmission and/or reception according to some aspects of some of various exemplary embodiments of the present disclosure. All or a subset of blocks and functions in FIG. 15 may be in the base station 1505 and the user equipment 1500 and may be performed by the user equipment 1500 and by the base station 1505. The Antenna 1510 may be used for transmission or reception of electromagnetic signals. The Antenna 1510 may comprise one or more antenna elements and may enable different input-output antenna configurations including Multiple-Input Multiple Output (MIMO) configuration, Multiple- Input Single-Output (MISO) configuration and Single-Input Multiple-Output (SIMO) configuration. In some embodiments, the Antenna 150 may enable a massive MIMO configuration with tens or hundreds of antenna elements. The Antenna 1510 may enable other multi-antenna techniques such as beamforming. In some examples, depending on the UE 1500 capabilities or the type of UE 1500 (e.g., a low-complexity UE), the UE 1500 may support a single antenna only.

[0099] The transceiver 1520 may communicate bi-directionally, via the Antenna 1510, wireless links as described herein. For example, the transceiver 1520 may represent a wireless transceiver at the UE and may communicate bi-directionally with the wireless transceiver at the base station or vice versa. The transceiver 1520 may include a modem to modulate the packets and provide the modulated packets to the Antennas 1510 for transmission, and to demodulate packets received from the Antennas 1510.

[0100] The memory 1530 may include RAM and ROM. The memory 1530 may store computer-readable, computer-executable code 1535 including instructions that, when executed, cause the processor to perform various functions described herein. In some examples, the memory 1530 may contain, among other things, a Basic Input/output System (BIOS) which may control basic hardware or software operation such as the interaction with peripheral components or devices. [0101] The processor 1540 may include a hardware device with processing capability (e.g., a general purpose processor, a DSP, a CPU, a microcontroller, an ASIC, an FPGA, a programmable logic device, a discrete gate or transistor logic component, a discrete hardware component, or any combination thereof). In some examples, the processor 1540 may be configured to operate a memory using a memory controller. In other examples, a memory controller may be integrated into the processor 1540. The processor 1540 may be configured to execute computer-readable instructions stored in a memory (e.g., the memory 1530) to cause the UE 1500 or the base station 1505 to perform various functions.

[0102] The Central Processing Unit (CPU) 1550 may perform basic arithmetic, logic, controlling, and Input/output (I/O) operations specified by the computer instructions in the Memory 1530. The user equipment 1500 and/or the base station 1505 may include additional peripheral components such as a graphics processing unit (GPU) 1560 and a Global Positioning System (GPS) 1570. The GPU 1560 is a specialized circuitry for rapid manipulation and altering of the Memory 1530 for accelerating the processing performance of the user equipment 1500 and/or the base station 1505. The GPS 1570 may be used for enabling location-based services or other services for example based on geographical position of the user equipment 1500.

[0103] In some examples, for NR sidelink communication, the UE may operate in two modes for resource allocation in sidelink: Scheduled resource allocation and UE autonomous resource selection. Scheduled resource allocation may be characterized by: The UE needs to be RRC CONNECTED in order to transmit data; and NG-RAN schedules transmission resources. UE autonomous resource selection may be characterized by: The UE may transmit data when inside NG-RAN coverage, irrespective of which RRC state the UE is in, and when outside NG-RAN coverage; and The UE autonomously selects transmission resources from resource pool(s). In some examples, for NR sidelink communication, the UE may perform sidelink transmissions only on a single carrier.

[0104] In some examples, NG-RAN may dynamically allocate resources to the UE via the SL-RNTI on PDCCH(s) for NR sidelink communication.

[0105] In some examples, in addition, NG-RAN may allocate sidelink resources to a UE with two types of configured sidelink grants: With type 1 , RRC may directly provide the configured sidelink grant only for NR sidelink communication; With type 2, RRC may define the periodicity of the configured sidelink grant while PDCCH can either signal and activate the configured sidelink grant or deactivate it. The PDCCH may be addressed to SL-CS-RNTI for NR sidelink communication.

[0106] In some examples, NG-RAN may semi-persistently allocate sidelink resources to the UE via the SL Semi-Persistent Scheduling V-RNTI on PDCCH(s) for V2X sidelink communication.

[0107] In some examples, for the UE performing NR sidelink communication, there may be more than one configured sidelink grant activated at a time on the carrier configured for sidelink transmission.

[0108] In some examples, when beam failure or physical layer problem occurs on MCG, the UE may continue using the configured sidelink grant Type 1 until initiation of the RRC connection re-establishment procedure. During handover, the UE may be provided with configured sidelink grants via handover command, regardless of the type. If provided, the UE may activate the configured sidelink grant Type 1 upon reception of the handover command or execution of CHO.

[0109] In some examples, the UE may send sidelink buffer status report to support scheduler operation in NG-RAN. For NR sidelink communication, the sidelink buffer status reports may refer to the data that is buffered in for a group of logical channels (LCG) per destination in the UE. Eight LCGs may be used for reporting of the sidelink buffer status reports. Two formats, which may be SL BSR and truncated SL BSR, may be used.

[0110] In some examples, the UE may autonomously select sidelink resource(s) from resource pool(s) provided by broadcast system information or dedicated signalling while inside NG-RAN coverage or by pre-configuration while outside NG-RAN coverage.

[0111] In some examples, for NR sidelink communication, the resource pool(s) may be provided for a given validity area where the UE does not need to acquire a new pool of resources while moving within the validity area, at least when this pool is provided by SIB. The NR SIB area scope mechanism may be reused to enable validity area for SL resource pool configured via broadcasted system information.

[0112] In some examples, the UE may be allowed to temporarily use UE autonomous resource selection with random selection for sidelink transmission based on configuration of the exceptional transmission resource pool.

[0113] In some examples, when a UE is inside NG-RAN coverage, NR sidelink communication and/or V2X sidelink communication may be configured and controlled by NG-RAN via dedicated signalling or system information: The UE may support and may be authorized to perform NR sidelink communication and/or V2X sidelink communication in NG-RAN; If configured, the UE may perform V2X sidelink communication unless otherwise specified, with the restriction that the dynamic scheduling for V2X sidelink communication (i.e. based on SL-V-RNTI) may not be supported; NG-RAN may provide the UE with intra-carrier sidelink configuration, inter-carrier sidelink configuration and anchor carrier(s) which may provide sidelink configuration via a Uu carrier for NR sidelink communication and/or V2X sidelink communication; When the UE cannot simultaneously perform both NR sidelink transmission and NR uplink transmission in time domain, prioritization between both transmissions may be done based on their priorities and thresholds configured by the NG-RAN or pre-configured. When the UE cannot simultaneously perform both V2X sidelink transmission and NR uplink transmission in time domain, prioritization between both transmissions may be done based on the priorities (i.e., PPPP) of V2X sidelink communication and a threshold configured by the NG-RAN or preconfigured.

[0114] In some examples, when a UE is outside NG-RAN coverage, SL DRB configuration(s) may be preconfigured to the UE for NR sidelink communication. If UE changes the RRC state but has not received the SL DRB configuration(s) for the new RRC state, UE may continue using the configuration obtained in the previous RRC state to perform sidelink data transmissions and receptions until the configuration for the new RRC state is received.

[0115] In some examples, the UE in RRC_CONNECTED may perform NR sidelink communication and/or V2X sidelink communication, as configured by the upper layers. The UE may send Sidelink UE Information to NG-RAN in order to request or release sidelink resources and report QoS information for each destination.

[0116] In some examples, NG-RAN may provide RRCReconfiguration to the UE in order to provide the UE with dedicated sidelink configuration. The RRCReconfiguration may include SL DRB configuration (s) for NR sidelink communication as well as mode 1 resource configuration and/or mode 2 resource configuration. If UE has received SL DRB configuration via system information, UE may continue using the configuration to perform sidelink data transmissions and receptions until a new configuration is received via the RRCReconfiguration.

[0117] In some examples, NG-RAN may configure measurement and reporting of CBR for NR sidelink communication and V2X sidelink communication and reporting of location information for V2X sidelink communication to the UE via RRCReconfiguration. [0118] In some examples, during handover, the UE may perform sidelink transmission and reception based on configuration of the exceptional transmission resource pool or configured sidelink grant Type 1 (for NR sidelink communication only) and reception resource pool of the target cell as provided in the handover command.

[0119] In some examples, the UE in RRC_IDLE or RRC_INACTIVE may perform NR sidelink communication and/or V2X sidelink communication, as configured by the upper layers. NG-RAN may provide common sidelink configuration to the UE in RRC_IDLE or RRC_INACTIVE via system information for NR sidelink communication and/or V2X sidelink communication. UE may receive resource pool configuration and SL DRB configuration via SIB 12 for NR sidelink communication, and/or resource pool configuration via SIB13 and SIB14 for V2X sidelink communication.

[0120] In some examples, when the UE performs cell reselection, the UE interested in V2X service(s) may consider at least whether NR sidelink communication and/or V2X sidelink communication are supported by the cell. The UE may consider the following carrier frequency as the highest priority frequency, except for the carrier only providing the anchor carrier: the frequency providing both NR sidelink communication configuration and V2X sidelink communication configuration, if configured to perform both NR sidelink communication and V2X sidelink communication; the frequency providing NR sidelink communication configuration, if configured to perform only NR sidelink communication; the frequency providing V2X sidelink communication configuration, if configured to perform only V2X sidelink communication.

[0121] In some examples, the UE may perform NR sidelink discoven- while in-coverage or out-of-coverage for non-relay operation. In some examples, the Relay discovery mechanism (except the U2N Relay specific threshold based discovery message transmission) may be applied to sidelink discovery. [0122] In some examples, Sidelink may support SL DRX for unicast, groupcast, and broadcast. Similar parameters as defined for Uu (on- duration, inactivity-timer, retransmission-timer, cycle) may be defined for SL to determine the SL active time for SL DRX. During the SL active time, the UE may perform SCI monitoring for data reception (i.e., PSCCH and 2nd stage SCI on PSSCH). The UE may skip monitoring of SCI for data reception during SL DRX inactive time.

[0123] In some examples, the SL active time of the RX UE may include the time in which any of its applicable SL on-duration timer(s), SL inactivity - timer(s) or SL retransmission timer(s) (for any of unicast, groupcast, or broadcast) are running. In some examples, the slots associated with announced periodic transmissions by the TX UE and the time in which a UE is expecting CSI report following a CSI request (for unicast) may be considered as SL active time of the RX UE.

[0124] In some examples, a TX UE may maintain a set of timers corresponding to the SL DRX timers in the RX UE(s) for each pair of source/destination L2 ID for unicast or destination L2 ID for groupcast/ broadcast. When data is available for transmission to one or more RX UE(s) configured with SL DRX, the TX UE may select resources taking into account the active time of the RX UE(s) determined by the timers maintained at the TX UE.

[0125] In some examples, a UE may determine from SIB 12 whether the gNB supports SL DRX or not.

[0126] In some examples, a default SL DRX configuration for groupcast/ broadcast may be used for discovery message in sidelink discovery and for relay discovery messages.

[0127] In some examples, for unicast, SL DRX may be configured per pair of source L2 ID and destination L2 ID.

[0128] In some examples, the UE may maintain a set of SL DRX timers for each direction per pair of source L2 ID and destination L2 ID. The SL DRX configuration for a pair of source/destination L2 IDs for a direction may be negotiated between the UEs in the AS layer. For SL DRX configuration of each direction, where one UE is the TX UE and the other is the RX UE: RX UE may send assistance information, which may include its desired SL on-duration timer, SL DRX start offset, and SL DRX cycle, to the TX UE and the mode 2 TX UE may use it to determine the SL DRX configuration for the RX UE; Regardless of whether assistance information is provided or not, the TX UE in RRC_IDLE/RRCJNACTIVE/OOC, or in RRC_CONNECTED and using mode 2 resource allocation, may determine the SL DRX Configuration for the RX UE. For a TX UE in RRC_CONNECTED and using mode 1 resource allocation, the SL DRX configuration for the RX UE may be determined by the serving gNB of the TX UE; TX UE may send the SL DRX configuration to be used by the RX UE to the RX UE; The RX UE may accept or reject the SL DRX configuration.

[0129] In some examples, a default SL DRX configuration for groupcast/ broadcast may be used for DCR messages.

[0130] In some examples, when the TX UE is in RRC_CONNECTED, the TX UE may report the received assistance information to its serving gNB and may send the SL DRX configuration to the RX UE upon receiving the SL DRX configuration in dedicated RRC signaling from the gNB. When the RX UE is in RRC_CONNECTED, the RX UE may report the received SL DRX configuration to its serving gNB, e.g., for alignment of the Uu and SL DRX configurations.

[0131] In some examples, SL on-duration timer, SL inactivity-timer, SL HARQ RTT timer, and SL HARQ retransmission timer may be supported in unicast. SL HARQ RTT timer and SL HARQ retransmission timer may be maintained per SL process at the RX UE. In addition to

(pre) configured values for each of these timers, SL HARQ RTT timer value may be derived from the retransmission resource timing when SCI indicates more than one transmission resource. [0132] In some examples, SL DRX MAC CE may be introduced for SL DRX operation in unicast only.

[0133] In some examples, for groupcast/broadcast, SL DRX may be configured commonly among multiple UEs based on QoS profile and Destination L2 ID. Multiple SL DRX configurations may be supported for each groupcast/broadcast.

[0134] In some examples, SL on-duration timer, SL inactivity-timer, SL HARQ RTT and SL retransmission timers may be supported for groupcast. In some examples, only SL on-duration timer may be supported for broadcast. SL DRX cycle, SL on-duration, and SL inactivity timer (only for groupcast) may be configured per QoS profile. The starting offset and slot offset of the SL DRX cycle may be determined based on the destination L2 ID. The SL HARQ RTT timer (only for groupcast) and SL HARQ retransmission timer (only for groupcast) may not be configured per QoS profile or per destination L2 ID. For groupcast, the RX UE may maintain an SL inactivity timer for each destination L2 ID, and may select the largest SL inactivity timer value if multiple SL inactivity timer values associated with different QoS profiles may be configured for that L2 ID. For groupcast and broadcast, the RX UE may maintain a single SL DRX cycle (selected as the smallest SL DRX cycle of any QoS profile of that L2 ID) and single SL on-duration (selected as the largest SL on-duration of any QoS profile of that L2 ID) for each destination L2 ID when multiple QoS profiles may be configured for that L2 ID.

[0135] In some examples, for groupcast, SL HARQ RTT timer and SL retransmission timer may be maintained per SL process at the RX UE. SL HARQ RTT timer may be set to different values to support both HARQ enabled and HARQ disabled transmissions.

[0136] In some examples, a default SL DRX configuration, common between groupcast and broadcast, may be used for a QoS profile which may not be mapped onto any non-default SL DRX configuration(s). [0137] In some examples, in-coverage TX and RX UEs in RRC_IDLE/RRC_INACTIVE may obtain their SL DRX configuration from SIB. UEs (TX or RX) in RRC_CONNECTED may obtain the SL DRX configuration from SIB, or from dedicated RRC signaling during handover. For the out of coverage case, the SL DRX configuration may be obtained from pre-configuration.

[0138] In some examples, for groupcast, the TX UE may restart its timer corresponding to the SL inactivity timer for the destination L2 ID (used for determining the allowable transmission time) upon reception of new data with the same destination L2 ID.

[0139] In some examples, TX profile may be introduced to ensure compatibility for groupcast and broadcast transmissions between UEs supporting/not-supporting SL DRX functionality. A TX profile may be provided by upper layers to AS layer and identifies one or more sidelink feature group(s) . Multiple TX profiles with the support of SL DRX and without the support of SL DRX may be associated to a destination L2 ID. A TX UE may only assume SL DRX for the destination L2 IDs when all the associated TX profiles correspond to support of SL DRX. A Tx UE may assume no SL DRX for the destination L2 ID if there is no associated TX profile. An RX UE may determine that SL DRX is used if all destination L2 IDs of interest are assumed to support SL DRX. For groupcast, the UE may report each destination L2 ID and associated SL DRX on/ off indication to the gNB.

[0140] In some examples, alignment of Uu DRX and SL DRX for a UE in RRC_CONNECTED may be supported for unicast, groupcast, and broadcast. Alignment of Uu DRX and SL DRX at the same UE may be supported. In some examples, for mode 1 scheduling, the alignment of Uu DRX of the TX UE and SL DRX of the RX UE may be supported.

[0141] In some examples, alignment may comprise of either full overlap or partial overlap in time between Uu DRX and SL DRX. For SL RX UEs in RRC_CONNECTED, alignment may be achieved by the gNB. [0142] In some examples, the SL UE in Mode 2 may support partial sensing-based resource allocation and random resource selection as power saving resource allocation methods. A SL mode 2 TX resource pool may be (pre)configured to allow full sensing only, partial sensing only, random selection only, or any combination(s) thereof. A UE may decide which resource allocation scheme(s) may be used in the AS based on its capability (for a UE in RRCJDLE/RRCJNACTIVE/OOC) and the allowed resource schemes in the resource pool configuration.

[0143] In some examples, random resource selection is applicable to both periodic and aperiodic traffic.

[0144] In example embodiments, Sidelink (SL) may support UE-to-UE direct communication using the sidelink resource allocation modes, physical-layer signals /channels, and physical layer procedures.

[0145] In example embodiments, two sidelink resource allocation modes may be supported: mode 1 and mode 2. In mode 1, the sidelink resource allocation may be provided by the network. In mode 2, UE may decide the SL transmission resources in the resource pool(s).

[0146] In example embodiments, Physical Sidelink Control Channel (PSCCH) may indicate resource and other transmission parameters used by a UE for PSSCH. PSCCH transmission may be associated with a DM- RS.

[0147] In example embodiments, Physical Sidelink Shared Channel (PSSCH) may transmit the TBs of data themselves, and control information for HARQ procedures and CSI feedback triggers, etc. At least 6 OFDM symbols within a slot may be used for PSSCH transmission. PSSCH transmission may be associated with a DM-RS and may be associated with a PT-RS.

[0148] In example embodiments, Physical Sidelink Feedback Channel (PSFCH) may carry HARQ feedback over the sidelink from a UE which is an intended recipient of a PSSCH transmission to the UE which performed the transmission. PSFCH sequence may be transmitted in one PRB repeated over two OFDM symbols near the end of the sidelink resource in a slot.

[0149] In example embodiments, the Sidelink synchronization signal may consist of sidelink primary and sidelink secondary synchronization signals (S-PSS, S-SSS), each occupying 2 symbols and 127 subcarriers. Physical Sidelink Broadcast Channel (PSBCH) may occupy 9 and 7 symbols for normal and extended CP cases respectively, including the associated DM-RS.

[0150] In example embodiments, Sidelink HARQ feedback may use PSFCH and may be operated in one of two options. In one option, which may be configured for unicast and groupcast, PSFCH may transmit either ACK or NACK using a resource dedicated to a single PSFCH transmitting UE. In another option, which may be configured for groupcast, PSFCH may transmit NACK, or no PSFCH signal may be transmitted, on a resource that can be shared by multiple PSFCH transmitting UEs.

[0151] In sidelink resource allocation mode 1, a UE which received PSFCH may report sidelink HARQ feedback to gNB via PUCCH or PUSCH.

[0152] In an example, for in-coverage operation, the power spectral density of the sidelink transmissions may be adjusted based on the pathloss from the gNB.

[0153] In an example, for unicast, the power spectral density of some sidelink transmissions may be adjusted based on the pathloss between the two communicating UEs.

[0154] In an example, for unicast, channel state information reference signal (CSI-RS) may be supported for CSI measurement and reporting in sidelink. A CSI report may be carried in a sidelink MAC CE.

[0155] In example embodiments, for measurement on the sidelink, the following UE measurement quantities may be supported: PSBCH reference signal received power (PSBCH RSRP); PSSCH reference signal received power (PSSCH-RSRP); PSCCH reference signal received power (PSCCH-RSRP); Sidelink received signal strength indicator (SL RSSI); Sidelink channel occupancy ratio (SL CR); Sidelink channel busy ratio (SL CBR).

[0156] In example embodiments, sidelink (SL) operation may utilize unlicensed spectrum (SL-U) for both mode 1 and mode 2 sidelink. In an example, the Uu interface operation for mode 1 may be via licensed spectrum (e.g., via licensed spectrum only).

[0157] In an example, channel access mechanisms from NR in unlicensed bands (NR-U) (e.g., channel access mechanisms for transmissions in unlicensed bands via the Uu interface) may be reused for sidelink unlicensed operation.

[0158] Example embodiments may enhance efficient Channel Occupancy Time acquisition and sharing to allow Receiving UEs feedback.

[0159] In example embodiments, power saving solutions and/or inter-UE coordination may be used to improve power consumption for battery limited terminals and reliability of Sidelink transmissions.

[0160] In an example, the Inter-UE Coordination (IUC) may be used to address the reliability issue due to a potential half-duplex and hidden node constraint in a unicast/ groupcast transmission for NR mode-2 operation. Such reliability risk may have major impact on some use cases including V2X. IUC may mitigate the effect of half-duplex and hidden node constraint though control signaling between Tx and RX UEs. With IUC, sidelink peers may coordinate with each other to jointly select the necessary sidelink resources for their communications.

[0161] In an example, the IUC procedure may be triggered by the Tx-UE and/or by the Rx-UE, which may want to receive any communication from the Tx-UE.

[0162] In an example, the UE triggering the periodic or event-driven IUC process may transmit an IUC request, which indicates the set of preferred or non-preferred resources to be used for upcoming sidelink data transmissions. [0163] In an example, the peer UE which receives the IUC request may respond to it by further providing its own preferences. Since the IUC mechanism involves both Tx-UE and Rx-UE in the process of UE autonomous resource selection, the collision probability of data transmission due to the classical hidden node issues may be minimized. Therefore, the QoS for sidelink communications may be improved with IUC while using mode-2 resource selection.

[0164] In an example SL operation, UEs may support inter-UE coordination (IUC) in Mode 2, whereby a UE-A sends information about resources to UE-B, which UE-B may then use for resource (re) selection.

[0165] In an example proactive scheme (e.g., scheme 1) of inter-UE coordination, UE-A may transmit preferred resource (scheme la) and non-preferred resource (scheme lb) to UE-B to aid resource selection at UE-B for transmission toward UE-A. In scheme 1, the transmission of IUC information from UE-A may be triggered by an explicit request from UE-B, or by a condition at UE-A. UE-A may determine the set of resources reserved by other UEs or slots where UE-A, when it is the intended receiver of UE-B, does not expect to perform SL reception from UE-B due to half-duplex operation. UE-A uses these resources as the set of non-preferred resources or excludes these resources to determine a set of preferred resources and sends the preferred/ non-preferred resources to UE-B. Preferred resources may be conflict-free, with higher received signal received power (RSRP) values, while non-preferred resources may be conflicted resources where UE-A is performing transmission to some other UEs or uplink transmission. UE-B's resources for resource (re)selection may be based on both UE-B's sensing results (e.g., if available) and the IUC information received from UE-A. For scheme 1, MAC CE and second-stage SCI or MAC CE only may be used to send IUC information. In an example, transmission of the explicit request and reporting for IUC information in unicast manner may be supported. [0166] In an example reactive approach (e.g., scheme 2), the IUC information sent from a UE-A to a UE-B may be the presence of expected/ potential resource conflict on the resources indicated by UE- B's sidelink control information (SCI). In scheme 2, UE-A may determine the expected / potential resource conflict within the resources indicated by UE-B's SCI. UE-B may use the conflicting resources to determine the resources to be reselected and exclude the conflicting resources from the reselected resources. In an example, for scheme 2, PSFCH may be used to send IUC information.

[0167] In example embodiments, Sidelink may operate in unlicensed spectrum (SL-U). In unlicensed spectrum a SL transmission may be subject to additional requirements such as Listen Before Talk (LBT) and maximum Channel Occupancy Time (CoT). Issues such as hidden node and half duplex operation of UEs in sidelink communications may be applicable to sidelink operation in unlicensed spectrum. More specifically, CoT initiation and sharing by a TX UE may also be based on IUC information received from Rx UEs.

[0168] In an example, IUC signaling framework in SL may be used for Tx UEs decisions on CoT initiation and sharing in SL-U.

[0169] In an example, the use and the schemes, e.g., IUC schemes la, lb and 2 , to be used for a SL-U communication may be configured by the network or pre-configured for a Sidelink Radio Bearer (SLR).

[0170] In an example embodiment, IUC information may be exchanged between Rx UEs and Tx UE and may be in Mode 2 operation of Sidelink.

[0171] In an example embodiment, gNB may help in triggering and collection of IUC information from Rx UEs and share them with a Tx UE in either Mode 1 or Mode 2 of SL resource allocation.

[0172] In an example, an IUC signaling framework in SL may support triggering, aggregation and sharing of such information from Rx UE in by gNB to be used for both Mode 1 and Mode 2 SL resource allocation. [0173] In an example, IUC information may be provided based on explicit request from Tx UE or gNB or it may be triggered based on a predefined condition, for example based on number of available slot for SL communication, due to other conflicts, becoming smaller than a threshold.

[0174] In an example as shown in FIG. 16, when IUC Scheme la/ lb is configured by the network or pre-configured for SL-U, one or more of the following steps may be used:

The Rx UE(s) may provide the Tx UE, directly or indirectly through gNB, with list of upcoming preferred /non-preferred resources.

Tx UE may enable CoT Sharing with the Rx UEs on resources tagged as preferred, or not tagged as non-preferred based on IUC by target Rx UEs.

Tx UE may initiate new CoTs based on resources tagged as preferred, or not tagged as non-preferred, by target Rx UEs.

[0175] In an example embodiment as shown in FIG. 17, in Scheme la/ lb if indirect IUC signaling framework is used, the Rx UEs with active PC5 connections configured with IUC in unicast/ groupcast SLRBs provide their list of upcoming preferred or non-preferred resources to the gNB. In an example, IUC signaling may be triggered based on a (pre) configured condition or be triggered by the gNB. In an example, the Rx UEs may send such information to the gNB using, PUCCH, MAC CE or using the UE Assistance Information messages. In an example, in Mode 2 Resource allocation, the gNB may provide the Tx UE with combined set of preferred/ non-preferred resources, for each SLRB to be used in Mode 2 resource reservation/ selection. In an example, in Mode 1 Resource Allocation, the gNB may take IUC information into account in allocating SL resources to Tx UE. [0176] In an example embodiment as shown in FIG. 18, when IUC Scheme 2 is configured by the network or pre-configured for SL-U, the following steps may be used:

Tx UE may send the SCI reserving, may be over booking, a set of time/ frequency resources (TFR-Setl) within one or multiple CoTs.

Rx UE may send PSFCH indicating a subset of TFR-Setl , i.e., TFR-Set2 which are preferred/non-preferred.

Tx UE may enable CoT Sharing with the Rx UEs on resources tagged as preferred, or not tagged as non-preferred based on IUC by target Rx UEs. Tx UE may initiate new CoTs based on resources tagged as preferred, or not tagged as non-preferred, by target Rx UEs.

Tx UE may also unreserve previously reserved resources, e.g., with an updated stage 1 SCI, if they would not be considered for upcoming transmissions based on IUC information or other reasons.

[0177] UE Sidelink communications may be in unlicensed bands. Communications in unlicensed bands may be subject to listen before talk (LBT) requirements and may further be subject to hidden node problems. There is a need to enhance sidelink operations in unlicensed bands. Inter-UE coordination (IUC) and exchange of IUC information between UEs may enhance the sidelink operation for sidelink communications in unlicensed bands (SL-U). Example embodiments enhance the sidelink operation in unlicensed bands and channel occupancy time (CoT) sharing based on inter-UE coordination.

[0178] In an example embodiment as shown in FIG. 19, a first UE may be configured with sidelink communications. The first UE may receive a list (e.g., a list of resources/ slots) indicating one or more preferred resources (e.g., slots) and/or one or more non-preference resources (e.g., slots). In some examples, the list may be received from a base station. In some examples, the list may be received by the first UE from a second UE or from one or more second UEs. For example, in response to the list being received from the one or more second UEs, the first UE may create a compound list based on the preferred/ non-preferred resources (e.g., slots) indicated by (e.g., by each of) the one or more second UEs. In some examples, the list may be provided by a base station. The list may be based on/ for inter-UE coordination (IUC) purposes. In some examples, the list may be received by the first UE in response to a request, e.g., a request by the first UE from the one or more second UEs or a request by the base station from the one or more second UEs, receiving the IUC information by the base station from the one or more second UEs and consequently, send the list/IUC information by the base station to the first UE. In case the IUC information is received by the base station from the one or more second UEs, the IUC information may be received via a physical layer channel (e.g., via PUCCH), via a MAC layer message (e.g., a MAC CE) or via one or more RRC messages (e.g., UE Assistance Information message).

[0179] In some examples, the list (e.g., the preferred and/or the nonpreferred) resources may be sidelink radio bearer (SLRB) specific and may be applicable to one or more SLRBs. For example, the message carrying the list/IUC information (e.g., the message sent to the first UE and/or to the base station) may include the SLRB information and may indicate the SLRB(s) to which the IUC/ list of preferred/ non-preferred resources apply. The first UE may receive the configuration parameters of one or more SLRBs and the configuration parameters may comprise first parameters indicating one or more first SLRBs to which the list of the preferred and/or non-preferred resources apply.

[0180] In response to receiving/ based on the received list, the first UE may enable CoT sharing (e.g., CoT sharing with one or more second UEs). The first UE may take into account the received list (e.g., the one or more preferred resources and / or the non-preferred resources indicated by the list) and may initiate one or more CoTs. The first UE may determine /initiate the one or more CoTs in response to /based on performing one or more LBT processes and the LBT processes indicating clear channel.

[0181] In some examples, the sidelink communications may be according to a mode 1 operation and the first UE may determine the resources for communications with one or more second UEs. The determination of the resources for communications with the one or more second UEs may be based on the list/IUC information.

[0182] In some examples, the sidelink communications may be according to a mode 2 operation and a base station may determine the resources for communications with one or more second UEs and may send the determined resources to the first UE. The determination of the resources for communications with the one or more second UEs may be based on the IUC information received from the one or more second UEs.

[0183] In an example embodiment as shown in FIG. 20, a first UE may transmit first sidelink control information (SCI) to a second UE. The first SCI may indicate (e.g., may indicate reservation of) a first set of resources within one or more channel occupancy times (CoTs). In response to transmitting the first SCI, the first UE may receive a message (e.g., via a sidelink channel), indicating a second set of resources that is a subset of the first set of resources and are preferred and/or non-preferred. The second UE may send the message to the first UE based on a triggering condition, e.g., reception of the first SCI from the first UE or based on a condition being satisfied at the second UE. In response to/based on receiving the message from the second UE, the first UE may enable CoT sharing on the second set of resources that are indicated to be /tagged as preferred and/or are not indicated to be/tagged as non-preferred. The first UE may initiate one or more CoTs based on the indication of the preferred or non-preferred resources (e.g., via/on the second set of resources that are indicated as preferred and/or are not indicated as non-preferred).

[0184] In some examples, in response to receiving the message indicating the preferred/ non-preferred resources, the first UE may send a second SCI (e.g., an updated SCI) indicating that certain resources are unreserved as opposed to being reserved according to the first SCI. The unreserved resources may be determined according to the preferred and/or non-preferred resources. For example, the updated SCI may indicate that at least the resources that are non-preferred according to the message (e.g., the message received by the first UE from the second UE comprising the UCI information) are un-reserved.

[0185] In an example embodiment, a method of sidelink communications may be used. A first user equipment (UE) may receive a list comprising at least one of one or more preferred resources and one or more nonpreferred resources. The first UE may initiate one or more channel occupancy times (CoTs) based on the list.

[0186] In some examples, the first UE may enable channel occupancy time (CoT) sharing with one or more second UEs based on the list.

[0187] In some examples, the receiving the list, by the first user equipment (UE), may be from one or more second UEs.

[0188] In some examples, the receiving the list, by the first user equipment (UE), may be from a base station.

[0189] In some examples, the list may be based on inter-UE coordination (IUC) information.

[0190] In some examples, receiving the list, by the first user equipment (UE), may be in response to a request. In some examples, the request may be for inter-UE coordination information (IUC). In some examples, the request may be by the first user equipment (UE) from one or more second UEs. In some examples, the request may be by a base station from one or more second UEs. In some examples, receiving the list by the first user equipment (UE), may be from the base station and in response to receiving inter-UE coordination (IUC) information by the base station from one or more second UEs. In some examples, receiving inter-user equipment (UE) coordination (IUC) information by the base station from the one or more second UEs is via a physical layer channel. In some examples, the physical layer channel is physical uplink control channel (PUCCH). In some examples, receiving inter-user equipment (UE) coordination (IUC) information by the base station from the one or more second UEs may be via a medium access control (MAC) control element (CE). In some examples, receiving inter-user equipment (UE) coordination (IUC) information by the base station from the one or more second UEs may be via a radio resource control (RRC) message. In some examples, the radio resource control (RRC) message may be a user equipment (UE) assistance information message.

[0191] In some examples, the list may be applicable to one or more sidelink radio bearers (SLRBs). In some examples, the first UE may receive configuration parameters of the one or more sidelink radio bearers (SLRBs). In some examples, the configuration parameters may comprise one or more first parameters indicating that the list is applicable to the one or more sidelink radio bearers (SLRBs).

[0192] In some examples, the sidelink communications may be according to a mode 1 sidelink operation. In some examples, the first user equipment (UE) may determine resource allocation information for communications with one or more second UEs. In some examples, determining the resource allocation information may be based on the list.

[0193] In some examples, the sidelink communications may be according to a mode 2 sidelink operation. In some examples, a base station may determine resource allocation information for communications of the first user equipment (UE) with one or more second UEs. In some examples, the first user equipment (UE) may receive, from the base station, the resource allocation information. In some examples, determining the resource allocation information may be based on the list. [0194] In some examples, the first user equipment (UE) may perform one or more listen before talk (LBT) processes, wherein the initiating the one or more channel occupancy times (CoTs) may be based on the one or more LBT processes indicating clear channel.

[0195] In an example embodiment, a method of sidelink communications may be used. A first user equipment (UE) may transmit, to a second UE, first sidelink control information (SCI) indicating a first set of resources within one or more channel occupancy times (CoTs). The first UE may receive, from the second UE, a message indicating a second set of resources, which is a subset of the first set of resources, which are preferred or are not preferred. The first UE may initiate one or more CoTs based on the indication of the preferred or non-preferred resources.

[0196] In an example, the first user equipment (UE) may enable channel occupancy time (CoT) sharing on the second set of resources indicated as preferred resources or not indicated as non-preferred resources.

[0197] In some examples, the initiating the one or more channel occupancy times (CoTs) may be on the second set of resources indicated as preferred resources or not indicated as non-preferred resources.

[0198] In some examples, the first user equipment (UE) may transmit an updated sidelink control information (SCI) in response to receiving the second set. In some examples, the updated sidelink control information (SCI) may indicate un-reserving resources that were reserved by the first SCI. In some examples, the un-reserving may at least be for resources that are indicated as non-preferred.

[0199] In some examples, the receiving the second set may be in response to one or more conditions being satisfied at the second user equipment (UE).

[0200] The exemplary blocks and modules described in this disclosure with respect to the various example embodiments may be implemented or performed with a general-purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. Examples of the general-purpose processor include but are not limited to a microprocessor, any conventional processor, a controller, a microcontroller, or a state machine. In some examples, a processor may be implemented using a combination of devices (e.g., a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration).

[0201] The functions described in this disclosure may be implemented in hardware, software executed by a processor, firmware, or any combination thereof. Instructions or code may be stored or transmitted on a computer-readable medium for implementation of the functions. Other examples for implementation of the functions disclosed herein are also within the scope of this disclosure. Implementation of the functions may be via physically co-located or distributed elements (e.g., at various positions), including being distributed such that portions of functions are implemented at different physical locations.

[0202] Computer-readable media includes but is not limited to non- transitory computer storage media. A non-transitory storage medium may be accessed by a general purpose or special purpose computer. Examples of non-transitory storage media include, but are not limited to, random access memoiy (RAM), read-only memory (ROM), electrically erasable programmable ROM (EEPROM), flash memory, compact disk (CD) ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, etc. A non-transitory medium may be used to carry or store desired program code means (e.g., instructions and/or data structures) and may be accessed by a general-purpose or specialpurpose computer, or a general-purpose or special-purpose processor. In some examples, the software/ program code may be transmitted from a remote source (e.g., a website, a server, etc.) using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave. In such examples, the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are within the scope of the definition of medium. Combinations of the above examples are also within the scope of computer-readable media.

[0203] As used in this disclosure, use of the term “or” in a list of items indicates an inclusive list. The list of items may be prefaced by a phrase such as “at least one of or “one or more of. For example, a list of at least one of A, B, or C includes A or B or C or AB (i.e., A and B) or AC or BC or ABC (i.e., A and B and C). Also, as used in this disclosure, prefacing a list of conditions with the phrase “based on” shall not be construed as “based only on” the set of conditions and rather shall be construed as “based at least in part on” the set of conditions. For example, an outcome described as “based on condition A” may be based on both a condition A and a condition B without departing from the scope of this disclosure.

[0204] In this specification the terms “comprise”, “include” or “contain” may be used interchangeably and have the same meaning and are to be construed as inclusive and open-ending. The terms “comprise”, “include” or “contain” may be used before a list of elements and indicate that at least all of the listed elements within the list exist but other elements that are not in the list may also be present. For example, if A comprises B and C, both {B, C] and {B, C, D} are within the scope of A.

[0205] The present disclosure, in connection with the accompanied drawings, describes example configurations that are not representative of all the examples that may be implemented or all configurations that are within the scope of this disclosure. The term “exemplary” should not be construed as “preferred” or “advantageous compared to other examples” but rather “an illustration, an instance or an example.” By reading this disclosure, including the description of the embodiments and the drawings, it will be appreciated by a person of ordinary skills in the art that the technology disclosed herein may be implemented using alternative embodiments. The person of ordinary skill in the art would appreciate that the embodiments, or certain features of the embodiments described herein, may be combined to arrive at yet other embodiments for practicing the technology described in the present disclosure. Thus, the disclosure is not limited to the examples and designs described herein but is to be accorded the broadest scope consistent with the principles and novel features disclosed herein.

Claims

WHAT IS CLAIMED IS:

1. A method of sidelink communications, comprising the steps of: receiving, by a first user equipment (UE), a list comprising preferred resources and non-preferred resources; and initiating, by the first UE, one or more channel occupancy times (CoTs) based on the list.

2. The method of claim 1, further comprising enabling, by the first user equipment (UE), channel occupancy time (CoT) sharing with one or more second UEs based on the list.

3. The method of claim 1, wherein the first user equipment (UE) receives the list from one or more second UEs.

4. The method of claim 1 , wherein the first user equipment (UE) receives the list from a base station.

5. The method of claim 1, wherein the list is based on inter-user equipment (UE) coordination (IUC) information.

6. The method of claim 1, wherein the first user equipment (UE) receives the list in response to a request.

7. The method of claim 6, wherein the request is for inter-user equipment (UE) coordination information (IUC).

8. The method of claim 6, wherein the request is by the first user equipment (UE) from one or more second user equipments (UEs).

9. The method of claim 5, wherein the request is by a base station from one or more second user equipment (UEs).

10- The method of claim 9, wherein the first user equipment (UE) receives the list from the base station in response to the base station receiving inter-UE coordination (IUC) information from one or more second UEs.

11. The method of claim 10, wherein the inter-user equipment (UE) coordination (IUC) information is received by the base station from the one or more second UEs via a physical layer channel.

12. The method of claim 11, wherein the physical layer channel is a physical uplink control channel (PUCCH).

13. The method of claim 10, wherein the inter-user equipment (UE) coordination (IUC) information is received by the base station from the one or more second UEs via a medium access control (MAC) control element (CE).

14. The method of claim 10, wherein the inter-user equipment (UE) coordination (IUC) information is received by the base station from the one or more second UEs via a radio resource control (RRC) message.

15. The method of claim 14, wherein the radio resource control (RRC) message is a user equipment (UE) assistance information message.

16. The method of claim 1, wherein the list is applicable to one or more sidelink radio bearers (SLRBs).

17. The method of claim 16, further comprising receiving configuration parameters of the one or more sidelink radio bearers (SLRBs).

18. The method of claim 17, wherein the configuration parameters comprise one or more first parameters indicating that the list is applicable to the one or more sidelink radio bearers (SLRBs).

19. The method of claim 1, wherein the sidelink communications is according to a mode 1 sidelink operation.

20. The method of claim 19, wherein the first user equipment (UE) determines resource allocation information for communications with one or more second UEs.

21. The method of claim 20, wherein the resource allocation information is determined based on the list.

22. The method of claim 1, wherein the sidelink communications operates according to a mode 2 sidelink operation.

23. The method of claim 22, wherein a base station determines resource allocation information for communications of the first user equipment (UE) with one or more second UEs.

24. The method of claim 23, further comprising receiving, by the first user equipment (UE), the resource allocation information from the base station.

25. The method of claim 22, wherein the resource allocation information is determined based on the list.

26. The method of claim 1, further comprising performing one or more listen before talk (LBT) processes, and wherein the initiating is based on the one or more LBT processes indicating clear channel.

27. A method of sidelink communications, comprising the steps of: transmitting, by a first user equipment (UE) to a second UE, first sidelink control information (SCI) indicating a first set of resources within one or more channel occupancy times (CoTs); receiving, by the first UE from the second UE, a message indicating a second set of resources that is a subset of the first set of resources, which are preferred or are not preferred; initiating one or more CoTs based on the indication of the preferred or non-preferred resources.

28. The method of claim 27, further comprising enabling channel occupancy time (CoT) sharing on the second set of resources indicated as preferred resources or not indicated as non-preferred resources.

29. The method of claim 27, wherein the one or more channel occupancy times (CoTs) are initiated on the second set of resources indicated as preferred resources or not indicated as non-preferred resources.

30. The method of claim 27, further comprising transmitting an updated sidelink control information (SCI) in response to receiving the second set.

31. The method of claim 30, wherein the updated sidelink control information (SCI) indicates un-reserving resources that were reserved by the first SCI.

32. The method of claim 31 , wherein the un-reserving is at least for resources that are indicated as non-preferred.

33. The method of claim 27, wherein the second set is received in response to one or more conditions being satisfied at the second user equipment (UE).