WO2022016495A1

WO2022016495A1 - Cell (re)selection and sidelink relay (re)selection procedures

Info

Publication number: WO2022016495A1
Application number: PCT/CN2020/104060
Authority: WO
Inventors: Peng Cheng; Ozcan Ozturk; Karthika Paladugu; Hong Cheng; Gavin Bernard Horn; Qing Li; Dan Vassilovski
Original assignee: Qualcomm Inc
Current assignee: Qualcomm Inc
Priority date: 2020-07-24
Filing date: 2020-07-24
Publication date: 2022-01-27
Anticipated expiration: 2023-01-24

Abstract

Disclosed are techniques for wireless communication. In an aspect, a remote user equipment (UE) initiates a cell selection procedure, initiates, in response to failure of the cell selection procedure, a relay selection procedure, and establishes, in response to discovering a relay UE during the relay selection procedure that is available to provide one or more UE-to-network relay services to the remote UE, a sidelink with the relay UE. In another aspect, a remote UE establishes a first sidelink with a first relay UE to obtain one or more UE-to-network relay services from the first relay UE, performs a relay discovery procedure to determine whether at least one second relay UE is available for relay reselection, and initiates, based on the at least one second relay UE being available for relay reselection, a relay reselection procedure.

Description

CELL (RE) SELECTION AND SIDELINK RELAY (RE) SELECTION PROCEDURES

BACKGROUND OF THE DISCLOSURE

1. Field of the Disclosure

Aspects of the disclosure relate generally to wireless communication and the like.

2. Description of the Related Art

Wireless communication systems have developed through various generations, including a first-generation analog wireless phone service (1G) , a second-generation (2G) digital wireless phone service (including interim 2.5G and 2.75G networks) , a third-generation (3G) high speed data, Internet-capable wireless service and a fourth-generation (4G) service (e.g., Long Term Evolution (LTE) or WiMax) . There are presently many different types of wireless communication systems in use, including cellular and personal communications service (PCS) systems. Examples of known cellular systems include the cellular analog advanced mobile phone system (AMPS) , and digital cellular systems based on code division multiple access (CDMA) , frequency division multiple access (FDMA) , time division multiple access (TDMA) , the Global System for Mobile communication (GSM) , etc.

A fifth generation (5G) wireless standard, referred to as New Radio (NR) , calls for higher data transfer speeds, greater numbers of connections, and better coverage, among other improvements. The 5G standard, according to the Next Generation Mobile Networks Alliance, is designed to provide data rates of several tens of megabits per second to each of tens of thousands of users, with 1 gigabit per second to tens of workers on an office floor. Several hundreds of thousands of simultaneous connections should be supported in order to support large sensor deployments. Consequently, the spectral efficiency of 5G mobile communications should be significantly enhanced compared to the current 4G standard. Furthermore, signaling efficiencies should be enhanced and latency should be substantially reduced compared to current standards.

SUMMARY

The following presents a simplified summary relating to one or more aspects disclosed herein. Thus, the following summary should not be considered an extensive overview relating to all contemplated aspects, nor should the following summary be considered to identify key or critical elements relating to all contemplated aspects or to delineate the scope associated with any particular aspect. Accordingly, the following summary has the sole purpose to present certain concepts relating to one or more aspects relating to the mechanisms disclosed herein in a simplified form to precede the detailed description presented below.

In an aspect, a method of wireless communication performed by a remote user equipment (UE) includes initiating a cell selection procedure; in response to failure of the cell selection procedure, initiating a relay selection procedure; and in response to discovering a relay UE during the relay selection procedure that is available to provide one or more UE-to-network relay services to the remote UE, establishing a sidelink with the relay UE.

In an aspect, a method of wireless communication performed by a remote UE includes establishing a first sidelink with a first relay UE to obtain one or more UE-to-network relay services from the first relay UE; performing a relay discovery procedure to determine whether at least one second relay UE is available for relay reselection; and based on the at least one second relay UE being available for relay reselection, initiating a relay reselection procedure.

In an aspect, a method of wireless communication performed by a remote UE includes establishing a first sidelink with a first relay UE to obtain one or more UE-to-network relay services from the first relay UE; determining cell ranking criteria for the first relay UE; performing a cell reselection procedure; determining cell ranking criteria for one or more cells detected during the cell reselection procedure; and based on a first cell of the one or more cells having higher cell ranking criteria than the cell ranking criteria for the first relay UE, establishing a wireless connection with the first relay UE.

Other objects and advantages associated with the aspects disclosed herein will be apparent to those skilled in the art based on the accompanying drawings and detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are presented to aid in the description of examples of one or more aspects of the disclosed subject matter and are provided solely for illustration of the examples and not limitation thereof:

FIG. 1 illustrates an exemplary wireless communications system, according to various aspects of the disclosure.

FIGS. 2A and 2B illustrate example wireless network structures, according to various aspects of the disclosure.

FIGS. 3A to 3C are simplified block diagrams of several sample aspects of components that may be employed in wireless communication nodes and configured to support communication as taught herein.

FIGS. 4A and 4B illustrate user plane and control plane protocol stacks, according to aspects of the disclosure.

FIG. 5 illustrates different radio resource control (RRC) states in New Radio (NR) .

FIG. 6A and 6B are diagrams illustrating example frame structures and channels within the frame structures.

FIGS. 7A and 7B illustrate exemplary call flows for different types of proximity services (ProSe) Direct Discovery.

FIG. 8 is a diagram of a simplified Layer-2 frame format for ProSe Direct Discovery messages.

FIG. 9A illustrates an exemplary call flow showing Layer-3 procedures for UE-to-network relay establishment.

FIG. 9B illustrates an exemplary call flow showing Layer-2 procedures for UE-to-network relay establishment.

FIG. 10 is a diagram of an exemplary UE-to-network relay scenario.

FIG. 11 is a diagram of an exemplary cell and relay (re) selection scenario for a remote UE.

FIGS. 12 to 14 illustrate exemplary methods of wireless environment sensing, according to aspects of the disclosure.

DETAILED DESCRIPTION

Aspects of the disclosure are provided in the following description and related drawings directed to various examples provided for illustration purposes. Alternate aspects may be devised without departing from the scope of the disclosure. Additionally, well-known elements of the disclosure will not be described in detail or will be omitted so as not to obscure the relevant details of the disclosure.

The words “exemplary” and/or “example” are used herein to mean “serving as an example, instance, or illustration. ” Any aspect described herein as “exemplary” and/or “example” is not necessarily to be construed as preferred or advantageous over other aspects. Likewise, the term “aspects of the disclosure” does not require that all aspects of the disclosure include the discussed feature, advantage or mode of operation.

Those of skill in the art will appreciate that the information and signals described below may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the description below may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof, depending in part on the particular application, in part on the desired design, in part on the corresponding technology, etc.

Further, many aspects are described in terms of sequences of actions to be performed by, for example, elements of a computing device. It will be recognized that various actions described herein can be performed by specific circuits (e.g., application specific integrated circuits (ASICs) ) , by program instructions being executed by one or more processors, or by a combination of both. Additionally, the sequence (s) of actions described herein can be considered to be embodied entirely within any form of non-transitory computer-readable storage medium having stored therein a corresponding set of computer instructions that, upon execution, would cause or instruct an associated processor of a device to perform the functionality described herein. Thus, the various aspects of the disclosure may be embodied in a number of different forms, all of which have been contemplated to be within the scope of the claimed subject matter. In addition, for each of the aspects described herein, the corresponding form of any such aspects may be described herein as, for example, “logic configured to” perform the described action.

As used herein, the terms “user equipment” (UE) and “base station” are not intended to be specific or otherwise limited to any particular radio access technology (RAT) , unless otherwise noted. In general, a UE may be any wireless communication device (e.g., a mobile phone, router, tablet computer, laptop computer, tracking device, wearable (e.g., smartwatch, glasses, augmented reality (AR) /virtual reality (VR) headset, etc. ) , vehicle (e.g., automobile, motorcycle, bicycle, etc. ) , Internet of Things (IoT) device, etc. ) used by a user to communicate over a wireless communications network. A UE may be mobile or may (e.g., at certain times) be stationary, and may communicate with a radio access network (RAN) . As used herein, the term “UE” may be referred to interchangeably as an “access terminal” or “AT, ” a “client device, ” a “wireless device, ” a “subscriber device, ” a “subscriber terminal, ” a “subscriber station, ” a “user terminal” or UT, a “mobile device, ” a “mobile terminal, ” a “mobile station, ” or variations thereof. Generally, UEs can communicate with a core network via a RAN, and through the core network the UEs can be connected with external networks such as the Internet and with other UEs. Of course, other mechanisms of connecting to the core network and/or the Internet are also possible for the UEs, such as over wired access networks, wireless local area network (WLAN) networks (e.g., based on IEEE 802.11, etc. ) and so on.

A base station may operate according to one of several RATs in communication with UEs depending on the network in which it is deployed, and may be alternatively referred to as an access point (AP) , a network node, a NodeB, an evolved NodeB (eNB) , a next generation eNB (ng-eNB) , a New Radio (NR) Node B (also referred to as a gNB or gNodeB) , etc. A base station may be used primarily to support wireless access by UEs, including supporting data, voice, and/or signaling connections for the supported UEs. In some systems a base station may provide purely edge node signaling functions while in other systems it may provide additional control and/or network management functions. A communication link through which UEs can send signals to a base station is called an uplink (UL) channel (e.g., a reverse traffic channel, a reverse control channel, an access channel, etc. ) . A communication link through which the base station can send signals to UEs is called a downlink (DL) or forward link channel (e.g., a paging channel, a control channel, a broadcast channel, a forward traffic channel, etc. ) . As used herein the term traffic channel (TCH) can refer to either an uplink /reverse or downlink /forward traffic channel.

The term “base station” may refer to a single physical transmission-reception point (TRP) or to multiple physical TRPs that may or may not be co-located. For example, where the term “base station” refers to a single physical TRP, the physical TRP may be an antenna of the base station corresponding to a cell (or several cell sectors) of the base station. Where the term “base station” refers to multiple co-located physical TRPs, the physical TRPs may be an array of antennas (e.g., as in a multiple-input multiple-output (MIMO) system or where the base station employs beamforming) of the base station. Where the term “base station” refers to multiple non-co-located physical TRPs, the physical TRPs may be a distributed antenna system (DAS) (a network of spatially separated antennas connected to a common source via a transport medium) or a remote radio head (RRH) (a remote base station connected to a serving base station) . Alternatively, the non-co-located physical TRPs may be the serving base station receiving the measurement report from the UE and a neighbor base station whose reference RF signals (or simply “reference signals” ) the UE is measuring. Because a TRP is the point from which a base station transmits and receives wireless signals, as used herein, references to transmission from or reception at a base station are to be understood as referring to a particular TRP of the base station.

In some implementations that support positioning of UEs, a base station may not support wireless access by UEs (e.g., may not support data, voice, and/or signaling connections for UEs) , but may instead transmit reference signals to UEs to be measured by the UEs, and/or may receive and measure signals transmitted by the UEs. Such a base station may be referred to as a positioning beacon (e.g., when transmitting signals to UEs) and/or as a location measurement unit (e.g., when receiving and measuring signals from UEs) .

An “RF signal” comprises an electromagnetic wave of a given frequency that transports information through the space between a transmitter and a receiver. As used herein, a transmitter may transmit a single “RF signal” or multiple “RF signals” to a receiver. However, the receiver may receive multiple “RF signals” corresponding to each transmitted RF signal due to the propagation characteristics of RF signals through multipath channels. The same transmitted RF signal on different paths between the transmitter and receiver may be referred to as a “multipath” RF signal. As used herein, an RF signal may also be referred to as a “wireless signal” or simply a “signal” where it is clear from the context that the term “signal” refers to a wireless signal or an RF signal.

According to various aspects, FIG. 1 illustrates an exemplary wireless communications system 100. The wireless communications system 100 (which may also be referred to as a wireless wide area network (WWAN) ) may include various base stations 102 and various UEs 104. The base stations 102 may include macro cell base stations (high power cellular base stations) and/or small cell base stations (low power cellular base stations) . In an aspect, the macro cell base station may include eNBs and/or ng-eNBs where the wireless communications system 100 corresponds to an LTE network, or gNBs where the wireless communications system 100 corresponds to a NR network, or a combination of both, and the small cell base stations may include femtocells, picocells, microcells, etc.

The base stations 102 may collectively form a RAN and interface with a core network 170 (e.g., an evolved packet core (EPC) or a 5G core (5GC) ) through backhaul links 122, and through the core network 170 to one or more location servers 172 (which may be part of core network 170 or may be external to core network 170) . In addition to other functions, the base stations 102 may perform functions that relate to one or more of transferring user data, radio channel ciphering and deciphering, integrity protection, header compression, mobility control functions (e.g., handover, dual connectivity) , inter-cell interference coordination, connection setup and release, load balancing, distribution for non-access stratum (NAS) messages, NAS node selection, synchronization, RAN sharing, multimedia broadcast multicast service (MBMS) , subscriber and equipment trace, RAN information management (RIM) , paging, positioning, and delivery of warning messages. The base stations 102 may communicate with each other directly or indirectly (e.g., through the EPC /5GC) over backhaul links 134, which may be wired or wireless.

The base stations 102 may wirelessly communicate with the UEs 104. Each of the base stations 102 may provide communication coverage for a respective geographic coverage area 110. In an aspect, one or more cells may be supported by a base station 102 in each geographic coverage area 110. A “cell” is a logical communication entity used for communication with a base station (e.g., over some frequency resource, referred to as a carrier frequency, component carrier, carrier, band, or the like) , and may be associated with an identifier (e.g., a physical cell identifier (PCI) , a virtual cell identifier (VCI) , a cell global identifier (CGI) ) for distinguishing cells operating via the same or a different carrier frequency. In some cases, different cells may be configured according to different protocol types (e.g., machine-type communication (MTC) , narrowband IoT (NB-IoT) , enhanced mobile broadband (eMBB) , or others) that may provide access for different types of UEs. Because a cell is supported by a specific base station, the term “cell” may refer to either or both of the logical communication entity and the base station that supports it, depending on the context. In addition, because a TRP is typically the physical transmission point of a cell, the terms “cell” and “TRP” may be used interchangeably. In some cases, the term “cell” may also refer to a geographic coverage area of a base station (e.g., a sector) , insofar as a carrier frequency can be detected and used for communication within some portion of geographic coverage areas 110.

While neighboring macro cell base station 102 geographic coverage areas 110 may partially overlap (e.g., in a handover region) , some of the geographic coverage areas 110 may be substantially overlapped by a larger geographic coverage area 110. For example, a small cell base station 102' may have a geographic coverage area 110' that substantially overlaps with the geographic coverage area 110 of one or more macro cell base stations 102. A network that includes both small cell and macro cell base stations may be known as a heterogeneous network. A heterogeneous network may also include home eNBs (HeNBs) , which may provide service to a restricted group known as a closed subscriber group (CSG) .

The communication links 120 between the base stations 102 and the UEs 104 may include uplink (also referred to as reverse link) transmissions from a UE 104 to a base station 102 and/or downlink (also referred to as forward link) transmissions from a base station 102 to a UE 104. The communication links 120 may use MIMO antenna technology, including spatial multiplexing, beamforming, and/or transmit diversity. The communication links 120 may be through one or more carrier frequencies. Allocation of carriers may be asymmetric with respect to downlink and uplink (e.g., more or less carriers may be allocated for downlink than for uplink) .

The wireless communications system 100 may further include a WLAN access point (AP) 150 in communication with WLAN stations (STAs) 152 via communication links 154 in an unlicensed frequency spectrum (e.g., 5 GHz) . When communicating in an unlicensed frequency spectrum, the WLAN STAs 152 and/or the WLAN AP 150 may perform a clear channel assessment (CCA) or listen before talk (LBT) procedure prior to communicating in order to determine whether the channel is available.

The small cell base station 102' may operate in a licensed and/or an unlicensed frequency spectrum. When operating in an unlicensed frequency spectrum, the small cell base station 102' may employ LTE or NR technology and use the same 5 GHz unlicensed frequency spectrum as used by the WLAN AP 150. The small cell base station 102', employing LTE /5G in an unlicensed frequency spectrum, may boost coverage to and/or increase capacity of the access network. NR in unlicensed spectrum may be referred to as NR-U. LTE in an unlicensed spectrum may be referred to as LTE-U, licensed assisted access (LAA) , or MulteFire.

The wireless communications system 100 may further include a millimeter wave (mmW) base station 180 that may operate in mmW frequencies and/or near mmW frequencies in communication with a UE 182. Extremely high frequency (EHF) is part of the RF in the electromagnetic spectrum. EHF has a range of 30 GHz to 300 GHz and a wavelength between 1 millimeter and 10 millimeters. Radio waves in this band may be referred to as a millimeter wave. Near mmW may extend down to a frequency of 3 GHz with a wavelength of 100 millimeters. The super high frequency (SHF) band extends between 3 GHz and 30 GHz, also referred to as centimeter wave. Communications using the mmW/near mmW radio frequency band have high path loss and a relatively short range. The mmW base station 180 and the UE 182 may utilize beamforming (transmit and/or receive) over a mmW communication link 184 to compensate for the extremely high path loss and short range. Further, it will be appreciated that in alternative configurations, one or more base stations 102 may also transmit using mmW or near mmW and beamforming. Accordingly, it will be appreciated that the foregoing illustrations are merely examples and should not be construed to limit the various aspects disclosed herein.

Transmit beamforming is a technique for focusing an RF signal in a specific direction. Traditionally, when a network node (e.g., a base station) broadcasts an RF signal, it broadcasts the signal in all directions (omni-directionally) . With transmit beamforming, the network node determines where a given target device (e.g., a UE) is located (relative to the transmitting network node) and projects a stronger downlink RF signal in that specific direction, thereby providing a faster (in terms of data rate) and stronger RF signal for the receiving device (s) . To change the directionality of the RF signal when transmitting, a network node can control the phase and relative amplitude of the RF signal at each of the one or more transmitters that are broadcasting the RF signal. For example, a network node may use an array of antennas (referred to as a “phased array” or an “antenna array” ) that creates a beam of RF waves that can be “steered” to point in different directions, without actually moving the antennas. Specifically, the RF current from the transmitter is fed to the individual antennas with the correct phase relationship so that the radio waves from the separate antennas add together to increase the radiation in a desired direction, while canceling to suppress radiation in undesired directions.

Transmit beams may be quasi-collocated, meaning that they appear to the receiver (e.g., a UE) as having the same parameters, regardless of whether or not the transmitting antennas of the network node themselves are physically collocated. In NR, there are four types of quasi-collocation (QCL) relations. Specifically, a QCL relation of a given type means that certain parameters about a second reference RF signal on a second beam can be derived from information about a source reference RF signal on a source beam. Thus, if the source reference RF signal is QCL Type A, the receiver can use the source reference RF signal to estimate the Doppler shift, Doppler spread, average delay, and delay spread of a second reference RF signal transmitted on the same channel. If the source reference RF signal is QCL Type B, the receiver can use the source reference RF signal to estimate the Doppler shift and Doppler spread of a second reference RF signal transmitted on the same channel. If the source reference RF signal is QCL Type C, the receiver can use the source reference RF signal to estimate the Doppler shift and average delay of a second reference RF signal transmitted on the same channel. If the source reference RF signal is QCL Type D, the receiver can use the source reference RF signal to estimate the spatial receive parameter of a second reference RF signal transmitted on the same channel.

In receive beamforming, the receiver uses a receive beam to amplify RF signals detected on a given channel. For example, the receiver can increase the gain setting and/or adjust the phase setting of an array of antennas in a particular direction to amplify (e.g., to increase the gain level of) the RF signals received from that direction. Thus, when a receiver is said to beamform in a certain direction, it means the beam gain in that direction is high relative to the beam gain along other directions, or the beam gain in that direction is the highest compared to the beam gain in that direction of all other receive beams available to the receiver. This results in a stronger received signal strength (e.g., reference signal received power (RSRP) , reference signal received quality (RSRQ) , signal-to-interference-plus-noise ratio (SINR) , etc. ) of the RF signals received from that direction.

Receive beams may be spatially related. A spatial relation means that parameters for a transmit beam for a second reference signal can be derived from information about a receive beam for a first reference signal. For example, a UE may use a particular receive beam to receive one or more reference downlink reference signals (e.g., positioning reference signals (PRS) , tracking reference signals (TRS) , phase tracking reference signal (PTRS) , cell-specific reference signals (CRS) , channel state information reference signals (CSI-RS) , primary synchronization signals (PSS) , secondary synchronization signals (SSS) , synchronization signal blocks (SSBs) , etc. ) from a base station. The UE can then form a transmit beam for sending one or more uplink reference signals (e.g., uplink positioning reference signals (UL-PRS) , sounding reference signal (SRS) , demodulation reference signals (DMRS) , PTRS, etc. ) to that base station based on the parameters of the receive beam.

Note that a “downlink” beam may be either a transmit beam or a receive beam, depending on the entity forming it. For example, if a base station is forming the downlink beam to transmit a reference signal to a UE, the downlink beam is a transmit beam. If the UE is forming the downlink beam, however, it is a receive beam to receive the downlink reference signal. Similarly, an “uplink” beam may be either a transmit beam or a receive beam, depending on the entity forming it. For example, if a base station is forming the uplink beam, it is an uplink receive beam, and if a UE is forming the uplink beam, it is an uplink transmit beam.

In 5G, the frequency spectrum in which wireless nodes (e.g., base stations 102/180, UEs 104/182) operate is divided into multiple frequency ranges, FR1 (from 450 to 6000 MHz) , FR2 (from 24250 to 52600 MHz) , FR3 (above 52600 MHz) , and FR4 (between FR1 and FR2) . In a multi-carrier system, such as 5G, one of the carrier frequencies is referred to as the “primary carrier” or “anchor carrier” or “primary serving cell” or “PCell, ” and the remaining carrier frequencies are referred to as “secondary carriers” or “secondary serving cells” or “SCells. ” In carrier aggregation, the anchor carrier is the carrier operating on the primary frequency (e.g., FR1) utilized by a UE 104/182 and the cell in which the UE 104/182 either performs the initial radio resource control (RRC) connection establishment procedure or initiates the RRC connection re-establishment procedure. The primary carrier carries all common and UE-specific control channels, and may be a carrier in a licensed frequency (however, this is not always the case) . A secondary carrier is a carrier operating on a second frequency (e.g., FR2) that may be configured once the RRC connection is established between the UE 104 and the anchor carrier and that may be used to provide additional radio resources. In some cases, the secondary carrier may be a carrier in an unlicensed frequency. The secondary carrier may contain only necessary signaling information and signals, for example, those that are UE-specific may not be present in the secondary carrier, since both primary uplink and downlink carriers are typically UE-specific. This means that different UEs 104/182 in a cell may have different downlink primary carriers. The same is true for the uplink primary carriers. The network is able to change the primary carrier of any UE 104/182 at any time. This is done, for example, to balance the load on different carriers. Because a “serving cell” (whether a PCell or an SCell) corresponds to a carrier frequency /component carrier over which some base station is communicating, the term “cell, ” “serving cell, ” “component carrier, ” “carrier frequency, ” and the like can be used interchangeably.

For example, still referring to FIG. 1, one of the frequencies utilized by the macro cell base stations 102 may be an anchor carrier (or “PCell” ) and other frequencies utilized by the macro cell base stations 102 and/or the mmW base station 180 may be secondary carriers ( “SCells” ) . The simultaneous transmission and/or reception of multiple carriers enables the UE 104/182 to significantly increase its data transmission and/or reception rates. For example, two 20 MHz aggregated carriers in a multi-carrier system would theoretically lead to a two-fold increase in data rate (i.e., 40 MHz) , compared to that attained by a single 20 MHz carrier.

The wireless communications system 100 may further include a UE 164 that may communicate with a macro cell base station 102 over a communication link 120 and/or the mmW base station 180 over a mmW communication link 184. For example, the macro cell base station 102 may support a PCell and one or more SCells for the UE 164 and the mmW base station 180 may support one or more SCells for the UE 164.

The wireless communications system 100 may further include one or more UEs, such as UE 190, that connects indirectly to one or more communication networks via one or more device-to-device (D2D) , or peer-to-peer (P2P) , links (referred to as “sidelinks” ) . In the example of FIG. 1, UE 190 has a sidelink 192 with one of the UEs 104 connected to one of the base stations 102 (e.g., through which UE 190 may indirectly obtain cellular connectivity) and a sidelink 194 with WLAN STA 152 connected to the WLAN AP 150 (through which UE 190 may indirectly obtain WLAN-based Internet connectivity) . In an example, the sidelinks 192 and 194 may be supported with any well-known D2D RAT, such as LTE Direct (LTE-D) , WiFi Direct (WiFi-D) ,

PC5 (a vehicle-to-everything (V2X) D2D interface) , and so on. UE 190 may also communicate directly with the UE 104 and WLAN STA 152 over the sidelink 192 and the sidelink 194, respectively.

Sidelink communication may be used for D2D media-sharing, vehicle-to-vehicle (V2V) communication, V2X communication (e.g., cellular V2X (cV2X) communication, enhanced V2X (eV2X) communication, etc. ) , emergency rescue applications, etc. One or more of a group of UEs utilizing D2D communications may be within the geographic coverage area 110 of a base station 102. Other UEs in such a group may be outside the geographic coverage area 110 of a base station 102 (as illustrated by UE 190) or be otherwise unable to receive transmissions from a base station 102. In some cases, groups of UEs communicating via D2D communications may utilize a one-to-many (1: M) system in which each UE transmits to every other UE in the group. In some cases, a base station 102 facilitates the scheduling of resources for D2D communications. In other cases, D2D communications are carried out between UEs without the involvement of a base station 102.

In an aspect, the

sidelinks

192 and 194 may operate over a communication medium of interest, which may be shared with other communications between other vehicles and/or infrastructure access points, as well as other RATs. A “medium” may be composed of one or more frequency, time, and/or space communication resources (e.g., encompassing one or more channels across one or more carriers) associated with communication between one or more transmitter /receiver pairs.

In an aspect, the medium of interest may correspond to at least a portion of an unlicensed frequency band shared among various RATs. Although different licensed frequency bands have been reserved for certain communication systems (e.g., by a government entity such as the Federal Communications Commission (FCC) in the United States) , these systems, in particular those employing small cell access points, have recently extended operation into unlicensed frequency bands such as the Unlicensed National Information Infrastructure (U-NII) band used by WLAN technologies, most notably IEEE 802.11x WLAN technologies generally referred to as “Wi-Fi. ” Example systems of this type include different variants of CDMA systems, TDMA systems, FDMA systems, orthogonal FDMA (OFDMA) systems, single-carrier FDMA (SC-FDMA) systems, and so on.

Note that although FIG. 1 only illustrates three of the UEs connected over sidelinks (i.e., WLAN STA 152, UE 190, one UE 104) , any of the illustrated UEs may engage in sidelink communication. In addition, although only UE 182 was described as being capable of beam forming, any of the illustrated UEs may be capable of beam forming. For example, where UE 190 is capable of beam forming, it may beam form over the

sidelinks

192 and 194.

According to various aspects, FIG. 2A illustrates an exemplary wireless network structure 200. For example, a 5GC 210 (also referred to as a Next Generation Core (NGC) ) can be viewed functionally as control plane functions (C-plane) 214 (e.g., UE registration, authentication, network access, gateway selection, etc. ) and user plane functions (U-plane) 212 (e.g., UE gateway function, access to data networks, IP routing, etc. ) , which operate cooperatively to form the core network. User plane interface (NG-U) 213 and control plane interface (NG-C) 215 connect the gNB 222 to the 5GC 210 and specifically to the user plane functions 212 and control plane functions 214, respectively. In an additional configuration, an ng-eNB 224 may also be connected to the 5GC 210 via NG-C 215 to the control plane functions 214 and NG-U 213 to user plane functions 212. Further, ng-eNB 224 may directly communicate with gNB 222 via a backhaul connection 223. In some configurations, the New RAN 220 may only have one or more gNBs 222, while other configurations include one or more of both ng-eNBs 224 and gNBs 222. Either (or both) gNB 222 or ng-eNB 224 may communicate with UEs 204 (e.g., any of the UEs described herein) over, for example, communication links 120 and/or 184. In an aspect, two or more UEs 204 may communicate with each other over a sidelink 242, which may correspond to sidelink 192 in FIG. 1.

Another optional aspect may include location server 230, which may be in communication with the 5GC 210 to provide location assistance for UEs 204. The location server 230 can be implemented as a plurality of separate servers (e.g., physically separate servers, different software modules on a single server, different software modules spread across multiple physical servers, etc. ) , or alternately may each correspond to a single server. The location server 230 can be configured to support one or more location services for UEs 204 that can connect to the location server 230 via the core network, 5GC 210, and/or via the Internet (not illustrated) . Further, the location server 230 may be integrated into a component of the core network, or alternatively may be external to the core network.

According to various aspects, FIG. 2B illustrates another example wireless network structure 250. For example, a 5GC 260 can be viewed functionally as control plane functions, provided by an access and mobility management function (AMF) 264, and user plane functions, provided by a user plane function (UPF) 262, which operate cooperatively to form the core network (i.e., 5GC 260) . User plane interface 263 and control plane interface 265 connect the ng-eNB 224 to the 5GC 260 and specifically to UPF 262 and AMF 264, respectively. In an additional configuration, a gNB 222 may also be connected to the 5GC 260 via control plane interface 265 to AMF 264 and user plane interface 263 to UPF 262. Further, ng-eNB 224 may directly communicate with gNB 222 via the backhaul connection 223, with or without gNB direct connectivity to the 5GC 260. In some configurations, the New RAN 220 may only have one or more gNBs 222, while other configurations include one or more of both ng-eNBs 224 and gNBs 222. The base stations of the New RAN 220 communicate with the AMF 264 over the N2 interface and with the UPF 262 over the N3 interface. Either (or both) gNB 222 or ng-eNB 224 may communicate with UEs 204 (e.g., any of the UEs described herein) over, for example, communication links 120 and/or 184. In an aspect, two or more UEs 204 may communicate with each other over a sidelink 242, which may correspond to wireless unicast sidelink 192 in FIG. 1.

The functions of the AMF 264 include registration management, connection management, reachability management, mobility management, lawful interception, transport for session management (SM) messages between the UE 204 and a Session Management Function (SMF) 266, transparent proxy services for routing SM messages, access authentication and access authorization, transport for short message service (SMS) messages between the UE 204 and the short message service function (SMSF) (not shown) , and security anchor functionality (SEAF) . The AMF 264 also interacts with an authentication server function (AUSF) (not shown) and the UE 204, and receives the intermediate key that was established as a result of the UE 204 authentication process. In the case of authentication based on a UMTS (universal mobile telecommunications system) subscriber identity module (USIM) , the AMF 264 retrieves the security material from the AUSF. The functions of the AMF 264 also include security context management (SCM) . The SCM receives a key from the SEAF that it uses to derive access-network specific keys. The functionality of the AMF 264 also includes location services management for regulatory services, transport for location services messages between the UE 204 and a location management function (LMF) 270 which acts as a location server 230, transport for location services messages between the New RAN 220 and the LMF 270, evolved packet system (EPS) bearer identifier allocation for interworking with the EPS, and UE 204 mobility event notification. In addition, the AMF 164 also supports functionalities for non-Third Generation Protocol Partnership (3GPP) access networks.

Functions of the UPF 262 include acting as an anchor point for intra-/inter-RAT mobility (when applicable) , acting as an external protocol data unit (PDU) session point of interconnect to a data network (not shown) , providing packet routing and forwarding, packet inspection, user plane policy rule enforcement (e.g., gating, redirection, traffic steering) , lawful interception (user plane collection) , traffic usage reporting, quality of service (QoS) handling for the user plane (e.g., UL/DL rate enforcement, reflective QoS marking in the DL) , UL traffic verification (service data flow (SDF) to QoS flow mapping) , transport level packet marking in the UL and DL, DL packet buffering and DL data notification triggering, and sending and forwarding of one or more “end markers” to the source RAN node. The UPF 262 may also support transfer of location services messages over a user plane between the UE 204 and a location server such as a secure user plane location (SUPL) Location Platform (SLP) 272.

The functions of the SMF 266 include session management, UE Internet protocol (IP) address allocation and management, selection and control of user plane functions, configuration of traffic steering at the UPF 262 to route traffic to the proper destination, control of part of policy enforcement and QoS, and downlink data notification. The interface over which the SMF 266 communicates with the AMF 264 is referred to as the N11 interface.

Another optional aspect may include an LMF 270, which may be in communication with the 5GC 260 to provide location assistance for UEs 204. The LMF 270 can be implemented as a plurality of separate servers (e.g., physically separate servers, different software modules on a single server, different software modules spread across multiple physical servers, etc. ) , or alternately may each correspond to a single server. The LMF 270 can be configured to support one or more location services for UEs 204 that can connect to the LMF 270 via the core network, 5GC 260, and/or via the Internet (not illustrated) . The SLP 272 may support similar functions to the LMF 270 but, whereas the LMF 270 may communicate with the AMF 264, New RAN 220, and UEs 204 over a control plane (e.g., using interfaces and protocols intended to convey signaling messages and not voice or data) , the SLP 272 may communicate with UEs 204 and external clients (not shown in FIG. 2B) over a user plane (e.g. using protocols intended to carry voice and/or data like the transmission control protocol (TCP) and/or IP) .

In an aspect, the LMF 270 and/or the SLP 272 may be integrated into a base station, such as the gNB 222 and/or the ng-eNB 224. When integrated into the gNB 222 and/or the ng-eNB 224, the LMF 270 and/or the SLP 272 may be referred to as a “location management component, ” or “LMC. ” However, as used herein, references to the LMF 270 and the SLP 272 include both the case in which the LMF 270 and the SLP 272 are components of the core network (e.g., 5GC 260) and the case in which the LMF 270 and the SLP 272 are components of a base station.

FIGS. 3A, 3B, and 3C illustrate several exemplary components (represented by corresponding blocks) that may be incorporated into a UE 302 (which may correspond to any of the UEs described herein) , a base station 304 (which may correspond to any of the base stations described herein) , and a network entity 306 (which may correspond to or embody any of the network functions described herein, including the location server 230 and the LMF 270) to support the file transmission operations as taught herein. It will be appreciated that these components may be implemented in different types of apparatuses in different implementations (e.g., in an ASIC, in a system-on-chip (SoC) , etc. ) . The illustrated components may also be incorporated into other apparatuses in a communication system. For example, other apparatuses in a system may include components similar to those described to provide similar functionality. Also, a given apparatus may contain one or more of the components. For example, an apparatus may include multiple transceiver components that enable the apparatus to operate on multiple carriers and/or communicate via different technologies.

The UE 302 and the base station 304 each include wireless wide area network (WWAN)

transceiver

310 and 350, respectively, configured to communicate via one or more wireless communication networks (not shown) , such as an NR network, an LTE network, a GSM network, and/or the like. The

WWAN transceivers

310 and 350 may be connected to one or

more antennas

316 and 356, respectively, for communicating with other network nodes, such as other UEs, access points, base stations (e.g., eNBs, gNBs) , etc., via at least one designated RAT (e.g., NR, LTE, GSM, etc. ) over a wireless communication medium of interest (e.g., some set of time/frequency resources in a particular frequency spectrum) . The

WWAN transceivers

310 and 350 may be variously configured for transmitting and encoding signals 318 and 358 (e.g., messages, indications, information, and so on) , respectively, and, conversely, for receiving and decoding signals 318 and 358 (e.g., messages, indications, information, pilots, and so on) , respectively, in accordance with the designated RAT. Specifically, the

transceivers

310 and 350 include one or

more transmitters

314 and 354, respectively, for transmitting and

encoding signals

318 and 358, respectively, and one or

more receivers

312 and 352, respectively, for receiving and

decoding signals

318 and 358, respectively.

The UE 302 and the base station 304 also include, at least in some cases, wireless local area network (WLAN) transceivers 320 and 360, respectively. The WLAN transceivers 320 and 360 may be connected to one or more antennas 326 and 366, respectively, for communicating with other network nodes, such as other UEs, access points, base stations, etc., via at least one designated RAT (e.g., WiFi, LTE-D,

etc. ) over a wireless communication medium of interest. The

WLAN transceivers

320 and 360 may be variously configured for transmitting and encoding signals 328 and 368 (e.g., messages, indications, information, and so on) , respectively, and, conversely, for receiving and decoding signals 328 and 368 (e.g., messages, indications, information, pilots, and so on) , respectively, in accordance with the designated RAT. Specifically, the

transceivers

320 and 360 include one or

more transmitters

324 and 364, respectively, for transmitting and

encoding signals

328 and 368, respectively, and one or

more receivers

322 and 362, respectively, for receiving and

decoding signals

328 and 368, respectively.

Transceiver circuitry including at least one transmitter and at least one receiver may comprise an integrated device (e.g., embodied as a transmitter circuit and a receiver circuit of a single communication device) in some implementations, may comprise a separate transmitter device and a separate receiver device in some implementations, or may be embodied in other ways in other implementations. In an aspect, a transmitter may include or be coupled to a plurality of antennas (e.g.,

antennas

316, 326, 356, 366) , such as an antenna array, that permits the respective apparatus to perform transmit “beamforming, ” as described herein. Similarly, a receiver may include or be coupled to a plurality of antennas (e.g.,

antennas

316, 326, 356, 366) , such as an antenna array, that permits the respective apparatus to perform receive beamforming, as described herein. In an aspect, the transmitter and receiver may share the same plurality of antennas (e.g.,

antennas

316, 326, 356, 366) , such that the respective apparatus can only receive or transmit at a given time, not both at the same time. A wireless communication device (e.g., one or both of the

transceivers

310 and 320 and/or 350 and 360) of the UE 302 and/or the base station 304 may also comprise a network listen module (NLM) or the like for performing various measurements.

The UE 302 and the base station 304 also include, at least in some cases, satellite positioning systems (SPS)

receivers

330 and 370. The

SPS receivers

330 and 370 may be connected to one or

more antennas

336 and 376, respectively, for receiving

SPS signals

338 and 378, respectively, such as global positioning system (GPS) signals, global navigation satellite system (GLONASS) signals, Galileo signals, Beidou signals, Indian Regional Navigation Satellite System (NAVIC) , Quasi-Zenith Satellite System (QZSS) , etc. The

SPS receivers

330 and 370 may comprise any suitable hardware and/or software for receiving and processing SPS signals 338 and 378, respectively. The

SPS receivers

330 and 370 request information and operations as appropriate from the other systems, and performs calculations necessary to determine positions of the UE 302 and the base station 304 using measurements obtained by any suitable SPS algorithm.

The base station 304 and the network entity 306 each include at least one network interfaces 380 and 390 for communicating with other network entities. For example, the network interfaces 380 and 390 (e.g., one or more network access ports) may be configured to communicate with one or more network entities via a wire-based or wireless backhaul connection. In some aspects, the network interfaces 380 and 390 may be implemented as transceivers configured to support wire-based or wireless signal communication. This communication may involve, for example, sending and receiving messages, parameters, and/or other types of information.

The UE 302, the base station 304, and the network entity 306 also include other components that may be used in conjunction with the operations as disclosed herein. The UE 302 includes processor circuitry implementing a processing system 332 for providing functionality relating to, for example, RF sensing, and for providing other processing functionality. The base station 304 includes a processing system 384 for providing functionality relating to, for example, RF sensing as disclosed herein, and for providing other processing functionality. The network entity 306 includes a processing system 394 for providing functionality relating to, for example, RF sensing as disclosed herein, and for providing other processing functionality. In an aspect, the

processing systems

332, 384, and 394 may include, for example, one or more general purpose processors, multi-core processors, ASICs, digital signal processors (DSPs) , field programmable gate arrays (FPGA) , or other programmable logic devices or processing circuitry.

The UE 302, the base station 304, and the network entity 306 include memory circuitry implementing

memory components

340, 386, and 396 (e.g., each including a memory device) , respectively, for maintaining information (e.g., information indicative of reserved resources, thresholds, parameters, and so on) . In some cases, the UE 302, the base station 304, and the network entity 306 may include

relay components

342, 388, and 398, respectively. The

relay components

342, 388, and 398 may be hardware circuits that are part of or coupled to the

processing systems

332, 384, and 394, respectively, that, when executed, cause the UE 302, the base station 304, and the network entity 306 to perform the functionality described herein. In other aspects, the

relay components

342, 388, and 398 may be external to the

processing systems

332, 384, and 394 (e.g., part of a modem processing system, integrated with another processing system, etc. ) . Alternatively, the

relay components

342, 388, and 398 may be memory modules (as shown in FIGS. 3A-C) stored in the

memory components

340, 386, and 396, respectively, that, when executed by the

processing systems

332, 384, and 394 (or a modem processing system, another processing system, etc. ) , cause the UE 302, the base station 304, and the network entity 306 to perform the functionality described herein.

The UE 302 may include one or more sensors 344 coupled to the processing system 332 to provide movement and/or orientation information that is independent of motion data derived from signals received by the WWAN transceiver 310, the WLAN transceiver 320, and/or the SPS receiver 330. By way of example, the sensor (s) 344 may include an accelerometer (e.g., a micro-electrical mechanical systems (MEMS) device) , a gyroscope, a geomagnetic sensor (e.g., a compass) , an altimeter (e.g., a barometric pressure altimeter) , and/or any other type of movement detection sensor. Moreover, the sensor (s) 344 may include a plurality of different types of devices and combine their outputs in order to provide motion information. For example, the sensor (s) 344 may use a combination of a multi-axis accelerometer and orientation sensors to provide the ability to compute positions in 2D and/or 3D coordinate systems.

In addition, the UE 302 includes a user interface 346 for providing indications (e.g., audible and/or visual indications) to a user and/or for receiving user input (e.g., upon user actuation of a sensing device such a keypad, a touch screen, a microphone, and so on) . Although not shown, the base station 304 and the network entity 306 may also include user interfaces.

Referring to the processing system 384 in more detail, in the downlink, IP packets from the network entity 306 may be provided to the processing system 384. The processing system 384 may implement functionality for an RRC layer, a packet data convergence protocol (PDCP) layer, a radio link control (RLC) layer, and a medium access control (MAC) layer. The processing system 384 may provide RRC layer functionality associated with broadcasting of system information (e.g., master information block (MIB) , system information blocks (SIBs) ) , RRC connection control (e.g., RRC connection paging, RRC connection establishment, RRC connection modification, and RRC connection release) , inter-RAT mobility, and measurement configuration for UE measurement reporting; PDCP layer functionality associated with header compression/decompression, security (ciphering, deciphering, integrity protection, integrity verification) , and handover support functions; RLC layer functionality associated with the transfer of upper layer packet data units (PDUs) , error correction through automatic repeat request (ARQ) , concatenation, segmentation, and reassembly of RLC service data units (SDUs) , re-segmentation of RLC data PDUs, and reordering of RLC data PDUs; and MAC layer functionality associated with mapping between logical channels and transport channels, scheduling information reporting, error correction, priority handling, and logical channel prioritization.

The transmitter 354 and the receiver 352 may implement Layer-1 functionality associated with various signal processing functions. Layer-1, which includes a physical (PHY) layer, may include error detection on the transport channels, forward error correction (FEC) coding/decoding of the transport channels, interleaving, rate matching, mapping onto physical channels, modulation/demodulation of physical channels, and MIMO antenna processing. The transmitter 354 handles mapping to signal constellations based on various modulation schemes (e.g., binary phase-shift keying (BPSK) , quadrature phase-shift keying (QPSK) , M-phase-shift keying (M-PSK) , M-quadrature amplitude modulation (M-QAM) ) . The coded and modulated symbols may then be split into parallel streams. Each stream may then be mapped to an orthogonal frequency division multiplexing (OFDM) subcarrier, multiplexed with a reference signal (e.g., pilot) in the time and/or frequency domain, and then combined together using an inverse fast Fourier transform (IFFT) to produce a physical channel carrying a time domain OFDM symbol stream. The OFDM symbol stream is spatially precoded to produce multiple spatial streams. Channel estimates from a channel estimator may be used to determine the coding and modulation scheme, as well as for spatial processing. The channel estimate may be derived from a reference signal and/or channel condition feedback transmitted by the UE 302. Each spatial stream may then be provided to one or more different antennas 356. The transmitter 354 may modulate an RF carrier with a respective spatial stream for transmission.

At the UE 302, the receiver 312 receives a signal through its respective antenna (s) 316. The receiver 312 recovers information modulated onto an RF carrier and provides the information to the processing system 332. The transmitter 314 and the receiver 312 implement Layer-1 functionality associated with various signal processing functions. The receiver 312 may perform spatial processing on the information to recover any spatial streams destined for the UE 302. If multiple spatial streams are destined for the UE 302, they may be combined by the receiver 312 into a single OFDM symbol stream. The receiver 312 then converts the OFDM symbol stream from the time-domain to the frequency domain using a fast Fourier transform (FFT) . The frequency domain signal comprises a separate OFDM symbol stream for each subcarrier of the OFDM signal. The symbols on each subcarrier, and the reference signal, are recovered and demodulated by determining the most likely signal constellation points transmitted by the base station 304. These soft decisions may be based on channel estimates computed by a channel estimator. The soft decisions are then decoded and de-interleaved to recover the data and control signals that were originally transmitted by the base station 304 on the physical channel. The data and control signals are then provided to the processing system 332, which implements Layer-3 and Layer-2 functionality.

In the uplink, the processing system 332 provides demultiplexing between transport and logical channels, packet reassembly, deciphering, header decompression, and control signal processing to recover IP packets from the core network. The processing system 332 is also responsible for error detection.

Similar to the functionality described in connection with the downlink transmission by the base station 304, the processing system 332 provides RRC layer functionality associated with system information (e.g., MIB, SIBs) acquisition, RRC connections, and measurement reporting; PDCP layer functionality associated with header compression/decompression, and security (ciphering, deciphering, integrity protection, integrity verification) ; RLC layer functionality associated with the transfer of upper layer PDUs, error correction through ARQ, concatenation, segmentation, and reassembly of RLC SDUs, re-segmentation of RLC data PDUs, and reordering of RLC data PDUs; and MAC layer functionality associated with mapping between logical channels and transport channels, multiplexing of MAC SDUs onto transport blocks (TBs) , demultiplexing of MAC SDUs from TBs, scheduling information reporting, error correction through hybrid automatic repeat request (HARQ) , priority handling, and logical channel prioritization.

Channel estimates derived by the channel estimator from a reference signal or feedback transmitted by the base station 304 may be used by the transmitter 314 to select the appropriate coding and modulation schemes, and to facilitate spatial processing. The spatial streams generated by the transmitter 314 may be provided to different antenna (s) 316. The transmitter 314 may modulate an RF carrier with a respective spatial stream for transmission.

The uplink transmission is processed at the base station 304 in a manner similar to that described in connection with the receiver function at the UE 302. The receiver 352 receives a signal through its respective antenna (s) 356. The receiver 352 recovers information modulated onto an RF carrier and provides the information to the processing system 384.

In the uplink, the processing system 384 provides demultiplexing between transport and logical channels, packet reassembly, deciphering, header decompression, control signal processing to recover IP packets from the UE 302. IP packets from the processing system 384 may be provided to the core network. The processing system 384 is also responsible for error detection.

For convenience, the UE 302, the base station 304, and/or the network entity 306 are shown in FIGS. 3A-C as including various components that may be configured according to the various examples described herein. It will be appreciated, however, that the illustrated blocks may have different functionality in different designs.

The various components of the UE 302, the base station 304, and the network entity 306 may communicate with each other over data buses 334, 382, and 392, respectively. The components of FIGS. 3A-C may be implemented in various ways. In some implementations, the components of FIGS. 3A-C may be implemented in one or more circuits such as, for example, one or more processors and/or one or more ASICs (which may include one or more processors) . Here, each circuit may use and/or incorporate at least one memory component for storing information or executable code used by the circuit to provide this functionality. For example, some or all of the functionality represented by blocks 310 to 346 may be implemented by processor and memory component (s) of the UE 302 (e.g., by execution of appropriate code and/or by appropriate configuration of processor components) . Similarly, some or all of the functionality represented by blocks 350 to 388 may be implemented by processor and memory component (s) of the base station 304 (e.g., by execution of appropriate code and/or by appropriate configuration of processor components) . Also, some or all of the functionality represented by blocks 390 to 398 may be implemented by processor and memory component (s) of the network entity 306 (e.g., by execution of appropriate code and/or by appropriate configuration of processor components) . For simplicity, various operations, acts, and/or functions are described herein as being performed “by a UE, ” “by a base station, ” “by a positioning entity, ” etc. However, as will be appreciated, such operations, acts, and/or functions may actually be performed by specific components or combinations of components of the UE, base station, positioning entity, etc., such as the

processing systems

332, 384, 394, the

transceivers

310, 320, 350, and 360, the

memory components

340, 386, and 396, the

relay components

342, 388, and 398, etc.

FIG. 4A illustrates a user plane protocol stack, according to aspects of the disclosure. As illustrated in FIG. 4A, a UE 404 and a base station 402 (which may correspond to any of the UEs and base stations, respectively, described herein) implement, from highest layer to lowest, a service data adaptation protocol (SDAP) layer 410, a PDCP layer 415, an RLC layer 420, a MAC layer 425, and a PHY layer 430. As illustrated by the double-arrow lines in FIG. 4A, each layer of the protocol stack implemented by the UE 404 communicates with the same layer of the base station 402, and vice versa. Note that the PHY layer 430 is also referred to as “Layer-1” or “L1. ” Collectively, the SDAP layer 410, the PDCP layer 415, the RLC layer 420, and the MAC layer 425 are referred to as “Layer-2” or “L2. ”

FIG. 4B illustrates a control plane protocol stack, according to aspects of the disclosure. In addition to the PDCP layer 415, the RLC layer 420, the MAC layer 425, and the PHY layer 430, the UE 404 and the base station 402 also implement an RRC layer 445. Further, the UE 404 and an AMF 406 (e.g., AMF 264) implement a NAS layer 440. Collectively, the RRC layer 445 and the NAS layer 440 are collectively referred to as “Layer-3” or “L3. ”

The main services and functions of the RLC layer 420 depend on the transmission mode and include transfer of upper layer PDUs, sequence numbering independent of the one in the PDCP layer 415, error correction through ARQ, segmentation and re-segmentation, reassembly of service data units (SDUs) , RLC SDU discard, and RLC re-establishment. The ARQ functionality provides error correction in AM mode, and has the following characteristics: ARQ retransmits RLC PDUs or RLC PDU segments based on RLC status reports, polling for an RLC status report is used when needed by RLC, and the RLC receiver can also trigger an RLC status report after detecting a missing RLC PDU or RLC PDU segment.

The main services and functions of the PDCP layer 415 for the user plane include sequence numbering, header compression and decompression (for robust header compression (ROHC) only) , transfer of user data, reordering and duplicate detection (if in-order delivery to layers above the PDCP layer 415 is required) , PDCP PDU routing (in case of split bearers) , retransmission of PDCP SDUs, ciphering and deciphering, PDCP SDU discard, PDCP re-establishment and data recovery for RLC AM, and duplication of PDCP PDUs. The main services and functions of the PDCP layer 415 for the control plane include ciphering, deciphering, and integrity protection, transfer of control plane data, and duplication of PDCP PDUs.

The SDAP layer 410 is an access stratum (AS) layer, the main services and functions of which include mapping between a QoS flow and a data radio bearer and marking QoS flow ID in both DL and UL packets. A single protocol entity of SDAP is configured for each individual PDU session.

The main services and functions of the RRC layer 445 include broadcast of system information related to AS and NAS, paging initiated by the 5GC (e.g., NGC 210 or 260) or RAN (e.g., New RAN 220) , establishment, maintenance, and release of an RRC connection between the UE and RAN, security functions including key management, establishment, configuration, maintenance, and release of signaling radio bearers (SRBs) and data radio bearers (DRBs) , mobility functions (including handover, UE cell selection and reselection and control of cell selection and reselection, context transfer at handover) , QoS management functions, UE measurement reporting and control of the reporting, and NAS message transfer to/from the NAS from/to the UE.

The NAS layer 440 is the highest stratum of the control plane between the UE 404 and the AMF 406 at the radio interface. The main functions of the protocols that are part of the NAS layer 440 are the support of mobility of the UE 404 and the support of session management procedures to establish and maintain IP connectivity between the UE 404 and a packet data network. The NAS layer 440 performs EPS bearer management, authentication, EPS connection management (ECM) -IDLE mobility handling, paging origination in ECM-IDLE, and security control.

FIG. 5 illustrates the different RRC states in NR. When a UE is powered up, it is initially in the RRC disconnected/idle state 510. After a random-access procedure to gain network access, the UE moves to the RRC connected state 520. If there is no activity from UE for a short time, it can suspend its session by moving to the RRC inactive state 530. The UE can resume its session by performing another random-access procedure to transition back to the RRC connected state 520. Thus, the UE needs to perform a random-access procedure to transition to the RRC connected state 520, regardless of whether the UE is in the RRC idle state 510 or the RRC inactive state 530.

The operations performed in the RRC idle state 510 include public land mobile network (PLMN) selection, broadcast of system information, cell re-selection mobility, paging for mobile terminated data (initiated and managed by the 5GC) , discontinuous reception (DRX) for core network paging (configured by NAS) . The operations performed in the RRC connected state 520 include 5GC (e.g., 5GC 260) and New RAN (e.g., New RAN 220) connection establishment (both control and user planes) , UE context storage at the New RAN and the UE, New RAN knowledge of the cell to which the UE belongs, transfer of unicast data to/from the UE, and network controlled mobility. The operations performed in the RRC inactive state 530 include the broadcast of system information, cell re-selection for mobility, paging (initiated by the New RAN) , RAN-based notification area (RNA) management (by the New RAN) , DRX for RAN paging (configured by the New RAN) , 5GC and New RAN connection establishment for the UE (both control and user planes) , storage of the UE context in the New RAN and the UE, and New RAN knowledge of the RNA to which the UE belongs.

Various frame structures may be used to support downlink and uplink transmissions between network nodes (e.g., base stations and UEs) . FIG. 6A is a diagram 600 illustrating an example of a downlink frame structure, according to aspects of the disclosure. FIG. 6B is a diagram 630 illustrating an example of channels within the downlink frame structure, according to aspects of the disclosure. Other wireless communications technologies may have different frame structures and/or different channels.

LTE, and in some cases NR, utilizes OFDM on the downlink and single-carrier frequency division multiplexing (SC-FDM) on the uplink. Unlike LTE, however, NR has an option to use OFDM on the uplink as well. OFDM and SC-FDM partition the system bandwidth into multiple (K) orthogonal subcarriers, which are also commonly referred to as tones, bins, etc. Each subcarrier may be modulated with data. In general, modulation symbols are sent in the frequency domain with OFDM and in the time domain with SC-FDM. The spacing between adjacent subcarriers may be fixed, and the total number of subcarriers (K) may be dependent on the system bandwidth. For example, the spacing of the subcarriers may be 15 kHz and the minimum resource allocation (resource block) may be 12 subcarriers (or 180 kHz) . Consequently, the nominal FFT size may be equal to 128, 256, 512, 1024, or 2048 for system bandwidth of 1.25, 2.5, 5, 10, or 20 megahertz (MHz) , respectively. The system bandwidth may also be partitioned into subbands. For example, a subband may cover 1.08 MHz (i.e., 6 resource blocks) , and there may be 1, 2, 4, 8, or 16 subbands for system bandwidth of 1.25, 2.5, 5, 10, or 20 MHz, respectively.

LTE supports a single numerology (subcarrier spacing, symbol length, etc. ) . In contrast, NR may support multiple numerologies (μ) , for example, subcarrier spacing of 15 kHz, 30 kHz, 60 kHz, 120 kHz, and 240 kHz or greater may be available. Table 1 provided below lists some various parameters for different NR numerologies.

Table 1

In the example of FIG. 6A and 6B, a numerology of 15 kHz is used. Thus, in the time domain, a 10 millisecond (ms) frame is divided into 10 equally sized subframes of 1 ms each, and each subframe includes one time slot. In FIG. 6A and 6B, time is represented horizontally (on the X axis) with time increasing from left to right, while frequency is represented vertically (on the Y axis) with frequency increasing (or decreasing) from bottom to top.

A resource grid may be used to represent time slots, each time slot including one or more time-concurrent resource blocks (RBs) (also referred to as physical RBs (PRBs) ) in the frequency domain. The resource grid is further divided into multiple resource elements (REs) . An RE may correspond to one symbol length in the time domain and one subcarrier in the frequency domain. In the numerology of FIG. 6A and 6B, for a normal cyclic prefix, an RB may contain 12 consecutive subcarriers in the frequency domain and seven consecutive symbols in the time domain, for a total of 84 REs. For an extended cyclic prefix, an RB may contain 12 consecutive subcarriers in the frequency domain and six consecutive symbols in the time domain, for a total of 72 REs. The number of bits carried by each RE depends on the modulation scheme.

Some of the REs carry downlink reference (pilot) signals (DL-RS) . The DL-RS may include PRS, TRS, PTRS, CRS, CSI-RS, DMRS, PSS, SSS, SSB, etc. FIG. 6A illustrates example locations of REs carrying PRS (labeled “R” ) .

FIG. 6B illustrates an example of various channels within a downlink slot of a radio frame. In NR, the channel bandwidth, or system bandwidth, is divided into multiple bandwidth parts (BWPs) . A BWP is a contiguous set of PRBs selected from a contiguous subset of the common RBs for a given numerology on a given carrier. Generally, a maximum of four BWPs can be specified in the downlink and uplink. That is, a UE can be configured with up to four BWPs on the downlink, and up to four BWPs on the uplink. Only one BWP (uplink or downlink) may be active at a given time, meaning the UE may only receive or transmit over one BWP at a time. On the downlink, the bandwidth of each BWP should be equal to or greater than the bandwidth of the SSB, but it may or may not contain the SSB.

Referring to FIG. 6B, a primary synchronization signal (PSS) is used by a UE to determine subframe/symbol timing and a physical layer identity. A secondary synchronization signal (SSS) is used by a UE to determine a physical layer cell identity group number and radio frame timing. Based on the physical layer identity and the physical layer cell identity group number, the UE can determine a PCI. Based on the PCI, the UE can determine the locations of the aforementioned DL-RS. The physical broadcast channel (PBCH) , which carries an MIB, may be logically grouped with the PSS and SSS to form an SSB (also referred to as an SS/PBCH) . The MIB provides a number of RBs in the downlink system bandwidth and a system frame number (SFN) . The physical downlink shared channel (PDSCH) carries user data and system information (SI) not transmitted through the PBCH, such as SIBs and paging messages.

A base station (more specifically, a cell or TRP of a base station) periodically transmits MIBs and SIBs to enable a UE to access the network/RAN through the base station. A MIB may be transmitted with the periodicity of 80 ms, with repetitive transmissions within this 80 ms periodicity. A MIB includes the parameters needed to decode a SIB Type 1 (SIB1) . The MIB and SIB1 are the first two RRC messages of an RRC session. A SIB1 may be transmitted with a periodicity of 160 ms, with repetitive transmissions within this 160 ms periodicity. A SIB1 includes information regarding the availability and scheduling (e.g., periodicity) of other SIB types (e.g., SIB2, SIB3, etc. ) and whether the other SIB types are transmitted periodically or on-demand. If the other SIB types are transmitted on-demand, then the SIB1 includes information for the UE to perform an SI request.

Paging is the mechanism whereby the network informs the UE that it has data for the UE. In most cases, the paging process occurs while the UE is in the IDLE or INACTIVE states (e.g., RRC idle state 510, RRC inactive state 530) . This means that the UE needs to monitor whether the network is transmitting any paging message to it. Specifically, during the idle state, the UE enters the sleep mode defined in its DRX cycle (defined in SIB2) . The UE periodically wakes up and monitors the physical downlink control channel (PDCCH) to check for the presence of a paging message on the PDCCH. If the PDCCH indicates that a paging message is transmitted in the subframe, then the UE needs to demodulate the paging channel (PCH) to see if the paging message is directed to it.

The PDCCH also carries downlink control information (DCI) within one or more control channel elements (CCEs) , each CCE including one or more RE group (REG) bundles (which may span multiple symbols in the time domain) , each REG bundle including one or more REGs, each REG corresponding to 12 resource elements (one resource block) in the frequency domain and one OFDM symbol in the time domain. The set of physical resources used to carry the PDCCH/DCI is referred to in NR as the control resource set (CORESET) . In NR, a PDCCH is confined to a single CORESET and is transmitted with its own DMRS. This enables UE-specific beamforming for the PDCCH.

In the example of FIG. 6B, there is one CORESET per BWP, and the CORESET spans three symbols (although it may be only one or two symbols) in the time domain. Unlike LTE control channels, which occupy the entire system bandwidth, in NR, PDCCH channels are localized to a specific region in the frequency domain (i.e., a CORESET) . Thus, the frequency component of the PDCCH shown in FIG. 6B is illustrated as less than a single BWP in the frequency domain. Note that although the illustrated CORESET is contiguous in the frequency domain, it need not be. In addition, the CORESET may span less than three symbols in the time domain.

The DCI within the PDCCH carries information about uplink resource allocation (persistent and non-persistent) and descriptions about downlink data transmitted to the UE. Multiple (such as up to eight) DCIs can be configured in the PDCCH, and these DCIs can have one of multiple formats. For example, there are different DCI formats for uplink scheduling, for non-MIMO downlink scheduling, for MIMO downlink scheduling, and for uplink power control. A PDCCH may be transported by 1, 2, 4, 8, or 16 CCEs in order to accommodate different DCI payload sizes or coding rates.

Proximity services (referred to as “ProSe” ) have been introduced in LTE and 5G. ProSe is a D2D technology that allows ProSe-enabled UEs to “discover” each other and to communicate with each other directly (e.g., over a sidelink or via the same serving base station) . For example, UE 190 and UE 104 in FIG. 1 may be examples of ProSe-enabled UEs. ProSe Direct Discovery procedures identify ProSe-enabled UEs that are in proximity to each another. ProSe Direct Communication procedures enable the establishment of communication paths between two or more ProSe-enabled UEs that are in direct wireless communication range. The ProSe Direct Communication path may be through the RAN (e.g., a shared serving base station) or over a unicast sidelink (e.g., sidelinks 192, 194) between the involved UEs.

5G supports two types of ProSe Direct Discovery procedures, “Model A” and “Model B. ” These Direct Discovery procedures are defined in 3GPP Technical Report (TR) 23.752, which is publicly available and incorporated by reference herein in its entirety. FIG. 7A illustrates an exemplary call flow 700 for Model A discovery, and FIG. 7B illustrates an exemplary call flow 750 for Model B discovery. As illustrated in FIG. 7A, for Model A discovery, an announcing UE (labeled “UE-1” ) sends announcement messages to one or more monitoring UEs (labeled “UE-2, ” “UE-3, ” “UE-4, ” and “UE-5” ) . In contrast, as illustrated in FIG. 7B, a discoverer UE (labeled “UE-1” ) sends a solicitation message to one or more discoveree UEs (labeled “UE-2, ” “UE-3, ” “UE-4, ” and “UE-5” ) . Discoveree UEs ( “UE-2” and “UE-3” in the example of FIG. 7B) interested in establishing a sidelink with the discoverer UE respond to the solicitation message with a response message.

The discovery messages (whether announcement messages or solicitation messages) are sent over a PC5 communication channel and not over a separate discovery channel. Discovery messages may be carried within the same Layer-2 frames as those used for ProSe Direct Communication. FIG. 8 is a diagram 800 of a simplified Layer-2 frame format for ProSe Direct Discovery messages. The “Destination Layer-2 ID” field can be set to a unicast, groupcast, or broadcast identifier. The “Source Layer-2 ID” field is set to a unicast identifier of the transmitter (e.g., “UE-1” in FIGS. 7A and 7B) . The “Frame type” field indicates that it is a ProSe Direct Discovery message.

5G also supports UE-to-network relaying, in which a ProSe-capable “relay” UE forwards downlink network traffic from the RAN to a ProSe-capable “remote” UE, and forwards uplink user data from the remote UE to the RAN. Relay discovery in 5G leverages the existing LTE ProSe relay discovery procedures, i.e., both Model A (announcement) and Model B (solicitation and response) restricted discovery, as illustrated in FIGS. 7A and 7B. The UE 190 in FIG. 1 may be an example of a remote UE and the UE 104 to which it is connected over sidelink 192 may be an example of a relay UE.

Relay service codes are used to identify the connectivity service (s) a ProSe relay UE may provide. A remote UE interested in a UE-to-network relay for a particular relay service attempts to discover a relay UE offering that relay service by monitoring for discovery messages from relay UEs that include a relay service code matching the desired relay service. Different relay service codes may be assigned for different PC5 services (e.g., for public safety police members, public safety firefighters, network controlled interactive service (NCIS) gaming, NCIS virtual conferencing, etc. ) . Relay service codes may be provisioned to a UE by the original equipment manufacturer (OEM) , the policy control function (PCF) during Uu (the air interface between the UE and the RAN) registration, or the like. Security information for discovery messages may be provisioned during the key management process.

A relay UE can provide Layer-2 or Layer-3 relaying between a network entity (e.g., a base station) and a remote UE. FIG. 9A illustrates an exemplary call flow 900 showing Layer-3 procedures for UE-to-network relay establishment. The remote UE and the relay UE (labeled “UE-to-NW Relay UE” ) illustrated in FIG. 9A may correspond to any of the UEs described herein. The NG-RAN may correspond to New RAN 220 in FIGS. 2A and 2B. The AMF, SMF, and UPF may correspond to the AMF 264, SMF 266, and UPF 262, respectively, in FIGS. 2A and 2B.

At stage 0, the remote UE and the relay UE register with the 5G system (5GS) and/or establish PDU session connectivity. The Layer-3 entities (e.g., the RRC layer 445 and/or the NAS layer 440) of the relay UE may establish a dedicated PDU session associated with one or more relay service codes. As such, at stage 1, the relay UE performs a separate relay PDU session establishment for each relay service the relay UE supports. At stage 2, the remote UE and the relay UE perform a discovery procedure, such as a Model A or Model B discovery procedure illustrated in FIGS. 7A and 7B.

At stage 3, the remote UE establishes a PC5-Sunicast sidelink with the relay UE, and at stage 4, obtains an IP address. The PC5 unicast sidelink AS configuration is managed using PC5-RRC. The relay UE and the remote UE coordinate on the AS configuration. The relay UE may consider information from the RAN (e.g., the base station serving the relay UE) to configure the PC5 sidelink. Whether the remote UE is authenticated and/or authorized to access relay services is performed during the PC5 sidelink establishment. Also at stage 3, the relay UE may establish a new PDU session for the relay UE. This may be a PDU session for another relay service code. After stage 4, the relay UE performs Layer-3 relaying for the remote UE.

FIG. 9B illustrates an exemplary call flow 950 showing Layer-2 procedures for UE-to-network relay establishment. The remote UE and the relay UE (labeled “UE-to-NW Relay UE” ) illustrated in FIG. 9B may correspond to any of the UEs described herein. The NG-RAN may correspond to New RAN 220 in FIGS. 2A and 2B. The AMF, SMF, and UPF may correspond to the AMF 264, SMF 266, and UPF 262, respectively, in FIGS. 2A and 2B.

In the call flow 950, there is no PC5 unicast sidelink setup prior to relaying. At stage 0, the remote UE and the relay UE register with the 5GS and/or establish PDU session connectivity. The Layer-2 entity (e.g., the SDAP layer 410, the PDCP layer 415, the RLC layer 420, and/or the MAC layer 425) of the relay UE may establish a dedicated PDU session associated with one or more relay service codes. As such, at stage 1, the relay UE performs a separate relay PDU session establishment for each relay service the relay UE supports. At stage 2, the remote UE and the relay UE perform a discovery procedure, such as a Model A or Model B discovery procedure illustrated in FIGS. 7A and 7B.

At stage 3, the remote UE sends an RRC connection request to the relay UE, which forwards it to the RAN (e.g., the base station serving the relay UE) . The remote UE sends the RRC messages over the sidelink broadcast control channel (SBCCH) on PC5 signaling radio bearers (SRBs) . Also at stage 3, the relay UE may establish a new PDU session for the relay UE. This may be a PDU session for another relay service code.

At stage 4, the remote UE and the relay UE perform RRC connection/security context establishment. At stage 5, the remote UE and the relay UE receive RRC reconfiguration messages from the RAN. The RAN can indicate the PC5 AS configuration to the remote UE and the relay UE independently via RRC messages.

At stage 6, the remote UE and the relay UE configure the new PC5 logical channels for the sidelink based on the RRC messages received at stage 5. Changes to V2X PC5 stack operation support radio bearer handling at the RRC/PDCP layers and support the corresponding logical channels of the PC5 sidelink. The PC5 RLC layer needs to support interaction with the PDCP layer directly.

Before relay establishment for a UE-to-network relay, the remote UE performs relay selection, and in case the relay connection is dropped after relay establishment, the remote UE may need to perform relay reselection. In NR, relay selection and reselection are similar to LTE ProSe UE-to-network relay selection and reselection. For relay selection, before the remote UE connects to a relay UE, the remote UE discovers all relay UEs whose sidelink discovery RSRP (SD-RSRP) is above a minimum threshold (e.g., q-RxLevMin) for relay reselection by some amount (e.g., minHyst) . Among the discovered relay UEs, the relay UE with the best SD-RSRP is selected as the relay UE.

For relay reselection, the remote UE has connected to one relay UE, but when the sidelink RSRP (SL-RSRP) of the sidelink with the current relay UE falls below a minimum threshold (e.g., q-RxLevMin) for relay reselection by some amount (e.g., minHyst) , the remote UE performs relay reselection. Specifically, like relay selection, the remote UE discovers all relay UEs whose SD-RSRP is above a minimum threshold (e.g., q-RxLevMin) for relay reselection by some amount (e.g., minHyst) . Among the discovered relay UEs, the relay UE with best SD-RSRP is reselected as the relay UE.

FIG. 10 is a diagram 1000 of an exemplary UE-to-network relay scenario. In the example of FIG. 10, a remote UE 1004 (e.g., any of the UEs described herein) and a relay UE 1006 (e.g., any other of the UEs described herein) are within the geographic coverage area 1010 of a serving base station 1002 (labeled “gNB, ” and which may correspond to any of the base stations described herein) . When the remote UE 1004 is in-coverage of the serving base station 1002 (i.e., within geographic coverage area 1010) , the remote UE 1004 monitors Uu paging (i.e., pages sent over the Uu air interface) and SIBs from the serving base station 1002, and therefore, the relay UE 1006 does not monitor the remote UE’s 1004 paging. The remote UE 1004 also sends any RRC setup or RRC resume messages directly to the serving base station 1002.

When the remote UE 1004 moves out-of-coverage (OOC) of the serving base station 1002 (i.e., outside geographic coverage area 1010) , as illustrated by the dotted line, the remote UE 1004 can no longer monitor Uu paging or SIB broadcasts from the serving base station 1002. Instead, the relay UE 1006 (referred to as an L2 relay) forwards pages and SIB broadcasts from the serving base station 1002 to the remote UE 1004. Specifically, for SIB broadcasts, the relay UE 1006 broadcasts an essential SIB (E-SIB) as part of the discovery procedure. An E-SIB consists of a MIB and part of the SIB1.

For paging, the relay UE 1006 performs forward-paging for the remote UE 1004 and forwards any pages from the network to the remote UE 1004. To determine if there is a page for the remote UE 1004, the relay UE 1006 monitors the remote UE’s 1004 paging frame (PF) and paging occasion (PO) within that PF. The PF and PO indicate the time period (e.g., one or more symbols, slots, subframes, etc. ) during which the RAN (i.e., serving base station 1002 in the example of FIG. 10) will transmit any pages for the remote UE 1004, and therefore, the time period the relay UE 1006 should monitor for pages for the remote UE 1004. As will be appreciated, the PF and PO are configured to occur periodically. Although both the PF and PO are needed to determine the time at which to monitor for pages, for simplicity, often only the PO is referenced. There is no change needed to the remote UE’s 1004 existing PF and PO calculation, the relay UE 1006 simply needs to be informed of the remote UE’s 1004 paging PO.

An issue with current relay selection and reselection techniques is that there are no procedures for how the remote UE is to perform both cell (re) selection and relay (re) selection. Relay (re) selection is described in 3GPP TR 23.752, which is publicly available and incorporated by reference herein in its entirety. Cell (re) selection is described in 3GPP Technical Specification (TS) 38.304, which is publicly available and incorporated by reference herein in its entirety.

FIG. 11 is a diagram 1100 of an exemplary cell and relay (re) selection scenario for a remote UE. In the example of FIG. 11, a remote UE 1104 (e.g., any of the UEs described herein) is within a handover region 1112 of a geographic coverage area 1110 of a first base station 1102 (labeled “Cell A, ” and which may correspond to any of the base stations described herein) . FIG. 11 also illustrates a second base station 1108 (labeled “Cell B, ” and which may correspond to any other of the base stations described herein) having a geographic coverage area 1120 adjacent the geographic coverage area 1110.

Because the remote UE 1104 is within the handover region 1112, it may need to perform cell reselection. For example, the remote UE 1104 may need to (attempt to) handover to the second base station 1108. In addition, the remote UE 1104 may need to select a new relay UE or, if already connected to a relay UE, reselect to a different relay UE. However, there are no existing procedures for how the remote UE 1104 is expected to perform both cell (re) selection and relay (re) selection in such a scenario.

Accordingly, the present disclosure provides techniques for performing relay (re) selection and cell (re) selection when both are needed. A first solution described herein can be performed before a remote UE has connected to a relay UE. Referring to the example of FIG. 11, when the remote UE 1104 is in the handover region 1112, the remote UE 1104 first attempts to perform cell (re) selection. That is, the remote UE 1104 searches for and attempts to camp on a “suitable” cell (e.g., a cell of the second base station 1108 in the example of FIG. 11) . In addition, the remote UE 1104 ignores any E-SIB broadcasts forwarded by the relay UE 1106 in this stage. Note that a “suitable” cell is defined in the applicable standard, and is a cell associated with a sufficient signal quality (e.g., RSRP, RSRQ) that it can be used for wireless communication.

If, however, the cell (re) selection procedure fails (i.e., the remote UE 1104 cannot find a “suitable” cell) , the remote UE 1104 regards itself as out-of-coverage and begins a relay (re) selection procedure by monitoring the E-SIBs from any nearby relay UEs. In the example of FIG. 11, cell reselection to the second base station 1108 may have failed because the remote UE 1104 is not within geographic coverage area 1120. As illustrated in FIG. 11, the remote UE 1104 can receive E-SIBs from a relay UE 1106 (e.g., any other of the UEs described herein) within the geographic coverage area 1110, and therefore, the remote UE 1104 may (re) select the relay UE 1106. Once connected to the relay UE 1106, the remote UE 1104 may no longer monitor Uu paging or SIB broadcasts from the first base station 1102. Instead, the relay UE 1106 may forward paging and SIB broadcasts from the first base station 1102 to the remote UE 1104, as described above with reference to FIG. 10.

Additional solutions disclosed herein can be performed after the remote UE has connected to a relay UE. As a second solution disclosed herein, in the case of cell (re) selection once the remote UE is connected to a relay UE, if there is at least one “suitable” relay UE available (e.g., relay UE 1106 in the example of FIG. 11) , the remote UE does not attempt to perform cell (re) selection. More specifically, if the relay UE to which the remote UE is currently connected is “suitable” for obtaining UE-to-network relay services, the remote UE does not attempt to perform cell reselection. Alternatively (if the current relay UE is not suitable) , or additionally (to determine if there is a more suitable relay UE) , the remote UE may perform a relay reselection procedure (since the remote UE is already connected to relay UE) to identify other available relay UEs. The available relay UE (s) may or may not include the relay UE to which the remote UE is currently connected. If one of the available relay UEs is more suitable than the current relay UE, the remote UE may drop the sidelink with the current relay UE and select a new, more suitable, relay UE based on the relay reselection procedure.

The reason avoid cell reselection in this solution is to keep the remote UE in the same cell, that is, relay (re) selection should not trigger cell (re) selection. This may be beneficial in the scenario illustrated in FIG. 11, where it would be preferable for the remote UE 1104 to stay in geographic coverage area 1110 as opposed to dropping its connection to the first base station 1102 when it cannot handover to the second base station 1108. If there is no “suitable” relay UE, the remote UE triggers a cell (re) selection procedure. Note that a “suitable” relay UE is a relay UE whose SL-RSRP is above a minimum threshold (e.g., q-RxLevMin) for relay reselection by some amount (e.g., minHyst) .

As a third solution disclosed herein, again for the case of cell (re) selection once the remote UE is connected to a relay UE, the remote UE regards relay UEs as inter-RAT cells and performs joint cell (re) selection and relay (re) selection. At a first stage, the remote UE performs a relay reselection procedure to ensure that the relay UE to which it is currently connected is “suitable” and has the highest SL-RSRP and/or sidelink RSRQ (SL-RSRQ) . If the current relay UE is suitable and has the highest SL-RSRP/SL-RSRQ, the remote UE can maintain the sidelink with the current relay UE. If the current relay UE is not suitable or does not have the highest SL-RSRP/SL-RSRQ of the discovered relay UEs, then the remote UE establishes a sidelink with a new relay UE that is suitable and has the highest SL-RSRP/SL-RSRQ.

At a second stage, the remote UE regards the connected relay UE (whether the original relay UE or a new relay UE) as its serving cell and calculates cell ranking criteria R _s for the connected relay UE based on the SL-RSRP/SL-RSRQ of the relay UE and a Q _Hyst parameter broadcast by the relay UE. For example, the remote UE calculates the cell rank for the relay UE as:

R _s=Q _mess, s+Q _Hyst-Q _{offset_temp}

where Q _meas, s is the measured RSRP/RSRQ of neighbor cell, Q _Hyst is provided by the relay UE, and Q _{offset_temp} is an additional offset to be used for cell selection and reselection when the RRC connection establishment fails on the cell.

At a third stage, the remote UE treats all Uu cells (i.e., cells of base stations) as neighbor cells. The remote UE can then perform a cell reselection procedure, and calculates cell ranking criteria R _n for the neighbor cells based on their RSRP and/or RSRQ and the Q _offset parameter broadcast by these cells. For example, the remote UE calculates the cell rank for a neighbor cell n as:

R _n=Q _meas, n+Q _offset-Q _{offset_temp}

where Q _meas, s is the measured RSRP/RSRQ of neighbor cell, Q _offsetis the RSRP/RSRQ offset for neighbor cell measurement, and Q _{offset_temp} is an additional offset to be used for cell selection and reselection when the RRC connection establishment fails on the cell.

The remote UE can then (re) select a neighbor cell having a higher cell ranking than the serving cell (i.e., the connected relay UE) , if one is available.

A fourth solution disclosed herein, again in the case of cell (re) selection once the remote UE is connected to a relay UE, is similar to the third solution, except that the remote UE can rank a Uu cell according to the best relay UE that can be used to connect to that cell, and consider the signal quality of the relay UE as a proxy for the signal quality of that cell. For example, referring to FIG. 11, the remote UE 1104 would consider the relay UE 1106 as a proxy for the first base station 1102.

The difference from the third solution is in the third stage of the third solution. Specifically, in the third stage, the remote UE treats all Uu cells and all detected relay UEs other than the relay UE to which it is currently connected as neighbor cells. The remote UE can then perform a cell reselection procedure, and calculate cell ranking criteria R _n for each cell and relay UE based on the RSRP/RSRQ and Q _offset of the Uu cells and the SL-RSRP/SL-RSRQ and Q _offset of the relay UEs. The remote UE can then (re) select a neighbor cell (a cell of a base station or a different relay UE) having a higher cell ranking than the serving cell (i.e., the connected relay UE) , if one is available.

In this fourth solution, a relay UE needs to provide the cell identifier of its serving cell and the basic serving cell configuration (e.g., ServingCellConfigCommonSIB1) in the E-SIBs it broadcasts. A relay UE also needs to indicate whether it is an “open” relay that can allow all UEs to connect to it. This indication may be provided in, for example, the parameter cellReservedForOtherUse. This is similar to the case of cell (re) selection to cells in a CSG.

In an aspect, a relay UE may include various relay (re) selection and cell (re) selection parameters in its broadcasted E-SIBs. Relay (re) selection-related parameters may include parameters such as q-RxLevMin, minHyst, and the relay UE’s QoS, load, and/or battery status. The relay (re) selection-related parameters may optionally include a neighbor relay list of other relay UEs associated with the same base station. A relay UE may also include SL-RSRP/SL-RSRQ related parameters.

For the third solution for cell (re) selection once the remote UE is connected to a relay UE (i.e., joint cell reselection and relay reselection) , the parameters in the E-SIBs may include the R-criteria related parameters for cell reselection (e.g., Q _Hyst, Q _offset) . These may be different from the parameters/values broadcast by the base station associated with the relay UE. Also for the third solution, a relay UE may include a serving frequency priority list for cell reselection, and optionally, a neighbor cell list. The R- criteria related parameters and the serving frequency priority list should be the same across all the relay UEs associated with the same base station.

For the fourth solution for cell (re) selection once the remote UE is connected to a relay UE, the parameters in an E-SIB may include the cell identifier of the relay UE’s serving cell and the basic serving cell configuration (e.g., ServingCellConfigCommonSIB1) , as noted above. A relay UE may also include a parameter indicating whether it is an “open” relay that can allow all UEs to connect to it. This indication may be provided in an E-SIB using, for example, the parameter cellReservedForOtherUse.

Note that in the foregoing, the terms “ (re) selection, ” “ (re) select, ” and the like are used to indicate that the remote UE may be performing an initial cell/relay selection procedure, where the remote UE is not currently connected to a cell or relay UE, or may be performing a cell/relay reselection procedure (i.e., a reselection procedure) , where the remote UE is currently connected to a cell or relay UE. In addition, unless indicated otherwise, a cell or relay selection procedure includes a cell or relay reselection procedure.

FIG. 12 illustrates an exemplary method 1200 of wireless communication, according to aspects of the disclosure. In an aspect, the method 1200 may be performed by a remote UE (e.g., any of the UEs described herein) .

At 1210, the remote UE initiates a cell selection procedure. In an aspect, operation 1210 may be performed by WWAN transceiver 310, processing system 332, memory component 340, and/or relay component 342, any or all of which may be considered means for performing this operation.

At 1220, in response to failure of the cell selection procedure, the remote UE initiates a relay selection procedure. In an aspect, operation 1220 may be performed by WWAN transceiver 310, processing system 332, memory component 340, and/or relay component 342, any or all of which may be considered means for performing this operation.

At 1230, in response to discovering a relay UE during the relay selection procedure that is available to provide one or more UE-to-network relay services to the remote UE, the remote UE establishes a sidelink with the relay UE, as described above with reference to FIGS. 9A and 9B, for example. In an aspect, operation 1230 may be performed by WWAN transceiver 310, processing system 332, memory component 340, and/or relay component 342, any or all of which may be considered means for performing this operation.

FIG. 13 illustrates an exemplary method 1300 of wireless communication, according to aspects of the disclosure. In an aspect, the method 1300 may be performed by a remote UE (e.g., any of the UEs described herein) .

At 1310, the remote UE establishes a first sidelink with a first relay UE to obtain one or more UE-to-network relay services from the first relay UE, as described above with reference to FIGS. 9A and 9B, for example. In an aspect, operation 1310 may be performed by WWAN transceiver 310, processing system 332, memory component 340, and/or relay component 342, any or all of which may be considered means for performing this operation.

At 1320, the remote UE performs a relay discovery procedure to determine whether at least one second relay UE is available for relay reselection, as described above with reference to FIGS. 7A and 7B, for example. In an aspect, operation 1320 may be performed by WWAN transceiver 310, processing system 332, memory component 340, and/or relay component 342, any or all of which may be considered means for performing this operation.

At 1330, based on the at least one second relay UE being available for relay reselection, the remote UE initiates a relay reselection procedure. In an aspect, operation 1330 may be performed by WWAN transceiver 310, processing system 332, memory component 340, and/or relay component 342, any or all of which may be considered means for performing this operation.

FIG. 14 illustrates an exemplary method 1400 of wireless communication, according to aspects of the disclosure. In an aspect, the method 1400 may be performed by a remote UE (e.g., any of the UEs described herein) .

At 1410, the remote UE establishes a first sidelink with a first relay UE to obtain one or more UE-to-network relay services from the first relay UE, as described above with reference to FIGS. 9A and 9B, for example. In an aspect, operation 1410 may be performed by WWAN transceiver 310, processing system 332, memory component 340, and/or relay component 342, any or all of which may be considered means for performing this operation.

At 1420, the remote UE determines cell ranking criteria for the first relay UE. In an aspect, operation 1420 may be performed by WWAN transceiver 310, processing system 332, memory component 340, and/or relay component 342, any or all of which may be considered means for performing this operation.

At 1430, the remote UE performs a cell reselection procedure. In an aspect, operation 1430 may be performed by WWAN transceiver 310, processing system 332, memory component 340, and/or relay component 342, any or all of which may be considered means for performing this operation.

At 1440, the remote UE determines cell ranking criteria for one or more cells detected during the cell reselection procedure. In an aspect, operation 1440 may be performed by WWAN transceiver 310, processing system 332, memory component 340, and/or relay component 342, any or all of which may be considered means for performing this operation.

At 1450, based on a first cell of the one or more cells having higher cell ranking criteria than the cell ranking criteria for the first relay UE, the remote UE establishes a wireless connection with the first relay UE. In an aspect, operation 1450 may be performed by WWAN transceiver 310, processing system 332, memory component 340, and/or relay component 342, any or all of which may be considered means for performing this operation.

Those of skill in the art will appreciate that information and signals may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.

Further, those of skill in the art will appreciate that the various illustrative logical blocks, modules, circuits, and algorithm steps described in connection with the aspects disclosed herein may be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present disclosure.

The various illustrative logical blocks, modules, and circuits described in connection with the aspects disclosed herein may be implemented or performed with a general purpose processor, a DSP, an ASIC, an 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. A general purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

The methods, sequences and/or algorithms described in connection with the aspects disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module may reside in random access memory (RAM) , flash memory, read-only memory (ROM) , erasable programmable ROM (EPROM) , electrically erasable programmable ROM (EEPROM) , registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. An exemplary storage medium is coupled to the processor such that the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor. The processor and the storage medium may reside in an ASIC. The ASIC may reside in a user terminal (e.g., UE) . In the alternative, the processor and the storage medium may reside as discrete components in a user terminal.

In one or more exemplary aspects, the functions described may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored on or transmitted over as one or more instructions or code on a computer-readable medium. Computer-readable media includes both computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. A storage media may be any available media that can be accessed by a computer. By way of example, and not limitation, such computer-readable media can comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to carry or store desired program code in the form of instructions or data structures and that can be accessed by a computer. Also, any connection is properly termed a computer-readable medium. For example, if the software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL) , or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of medium. Disk and disc, as used herein, includes compact disc (CD) , laser disc, optical disc, digital versatile disc (DVD) , floppy disk and Blu-ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer-readable media.

While the foregoing disclosure shows illustrative aspects of the disclosure, it should be noted that various changes and modifications could be made herein without departing from the scope of the disclosure as defined by the appended claims. The functions, steps and/or actions of the method claims in accordance with the aspects of the disclosure described herein need not be performed in any particular order. Furthermore, although elements of the disclosure may be described or claimed in the singular, the plural is contemplated unless limitation to the singular is explicitly stated.

Claims

A method of wireless communication performed by a remote user equipment (UE) , comprising:

initiating a cell selection procedure;

in response to failure of the cell selection procedure, initiating a relay selection procedure; and

in response to discovering a relay UE during the relay selection procedure that is available to provide one or more UE-to-network relay services to the remote UE, establishing a sidelink with the relay UE.
The method of claim 1, ignoring essential system information blocks (E-SIBs) from relay UEs, including the relay UE, during the cell selection procedure.
The method of claim 1, further comprising:

in response to the failure of the cell selection procedure, switching to an out-of-coverage mode.
The method of claim 1, wherein:

the relay UE performs Layer 3 relaying between a network entity and the remote UE, or

the relay UE performs Layer 2 relaying between the network entity and the remote UE.
A method of wireless communication performed by a remote user equipment (UE) , comprising:

establishing a first sidelink with a first relay UE to obtain one or more UE-to-network relay services from the first relay UE;

performing a relay discovery procedure to determine whether at least one second relay UE is available for relay reselection; and

based on the at least one second relay UE being available for relay reselection, initiating a relay reselection procedure.
The method of claim 5, wherein the at least one second relay UE is available based on a sidelink reference signal received power (SL-RSRP) and/or a sidelink reference signal received quality (SL-RSRQ) associated with the at least one second relay UE being higher than a minimum threshold by a preconfigured amount.
The method of claim 5, further comprising:

based on success of the relay reselection procedure, establishing a second sidelink with the at least one second relay UE to obtain the one or more UE-to-network relay services from the at least one second relay UE.
The method of claim 7, further comprising:

disconnecting from the first sidelink with the first relay UE.
The method of claim 5, wherein, based on the at least one second relay UE not being available for relay reselection, the remote UE maintains the first sidelink with the first relay UE and does not perform the relay reselection procedure.
The method of claim 5, wherein:

the at least one second relay UE is the first relay UE, and

the remote UE maintains the first sidelink with the first relay UE and does not perform the relay reselection procedure.
The method of claim 5, wherein:

the remote UE and the at least one second relay UE are served by the same base station, and

the remote UE does not perform a cell reselection procedure.
A method of wireless communication performed by a remote user equipment (UE) , comprising:

establishing a first sidelink with a first relay UE to obtain one or more UE-to-network relay services from the first relay UE;

determining cell ranking criteria for the first relay UE;

performing a cell reselection procedure;

determining cell ranking criteria for one or more cells detected during the cell reselection procedure; and

based on a first cell of the one or more cells having higher cell ranking criteria than the cell ranking criteria for the first relay UE, establishing a wireless connection with the first relay UE.
The method of claim 12, further comprising:

establishing an initial sidelink with an initial relay UE to obtain the one or more UE-to-network relay services from the initial relay UE; and

performing a relay reselection procedure to determine whether the initial relay UE is suitable to provide the one or more UE-to-network relay services; and

identifying one or more relay UEs, including the first relay UE, based on the relay reselection procedure,

wherein the remote UE establishes the first sidelink with the first relay UE based on the first relay UE being associated with a better signal quality than the initial relay UE.
The method of claim 13, further comprising:

disconnecting from the initial sidelink with the initial relay UE.
The method of claim 12, further comprising:

performing a relay reselection procedure to determine whether the first relay UE is suitable to provide the one or more UE-to-network relay services; and

determining that the first relay UE is suitable to provide the one or more UE-to-network relay services based on the relay reselection procedure.
The method of claim 15, wherein the first relay UE is determined to be suitable to provide the one or more UE-to-network relay services based on a sidelink reference signal received power (SL-RSRP) and/or a sidelink reference signal received quality (SL-RSRQ) associated with the first relay UE being higher than a minimum threshold by a preconfigured amount.
The method of claim 12, wherein the remote UE treats the first relay UE as a serving cell for the remote UE and the one or more cells detected during the cell reselection procedure as neighbor cells.
The method of claim 17, wherein the one or more cells comprise all cells of all base stations discovered during the cell reselection procedure.
The method of claim 17, wherein the one or more cells comprise all relay UEs discovered during a relay reselection procedure and all cells of all base stations discovered during the cell reselection procedure.
The method of claim 19, further comprising:

receiving, from each relay UE discovered during the relay reselection procedure, an identifier of a cell of a base station with which the relay UE is associated, a basic serving cell configuration, and an indication of whether the relay UE can allow the remote UE to connect to the relay UE.
The method of claim 20, wherein the remote UE receives, from each relay UE discovered during the relay reselection procedure, the identifier of the cell of the base station with which the relay UE is associated and the basic serving cell configuration in an essential system information block (E-SIB) .
The method of claim 12, further comprising:

receiving, from each relay UE discovered during a relay reselection procedure, an E-SIB, the E-SIB including relay selection parameters.
The method of claim 22, wherein the relay selection parameters comprise:

a minimum signal quality threshold associated with the relay UE,

an amount a signal quality measurement should be above the minimum signal quality threshold,

a list of neighbor relay UEs of the relay UE associated with the same base station,

parameters related to SL-RSRQ and/or SL-RSRP for the relay UE, or

any combination thereof.
The method of claim 23, wherein the relay selection parameters further comprise:

one or more parameters for cell reselection,

a serving frequency priority list for cell reselection,

a list of neighbor cells of a cell serving the relay UE, or

any combination thereof.
The method of claim 24, wherein the one or more parameters for cell reselection are different than parameters for cell reselection broadcasted by a cell associated with the relay UE.
The method of claim 23, wherein the relay selection parameters further comprise:

an identifier of a cell of a base station with which the relay UE is associated,

a basic serving cell configuration,

an indication of whether the relay UE can allow the remote UE to connect to the relay UE, or

any combination thereof.
The method of claim 12, wherein the cell ranking criteria for the first relay UE comprises an SL-RSRP, an SL-RSRQ, a Q _Hyst, or any combination thereof associated with the first relay UE.
The method of claim 12, wherein the cell ranking criteria for the one or more cells comprises a reference signal received power (RSRP) , a reference signal received quality (RSRQ) , a Q _Hyst, or any combination thereof associated with each of the one or more cells.
The method of claim 12, wherein:

the first relay UE performs Layer 3 relaying between a network entity and the remote UE, or

the first relay UE performs Layer 2 relaying between the network entity and the remote UE.
An apparatus comprising at least one processor and memory coupled to the at least one processor, the at least one processor and memory being configured to perform a method in accordance with any of claims 1 to 29.