Method and device for relaying user equipment in a wireless communication system to support connection with another remote user equipment

Abstract

A method and apparatus for supporting relay between user equipments are disclosed. In one embodiment, the method includes a relay user equipment establishing a first layer 2 link with a first user equipment and a second layer 2 link with a second user equipment, wherein the first layer 2 link and the second layer 2 link are used to forward services between the first user equipment and the second user equipment. The method also includes the relay user equipment receiving a first PC5 message for requesting to establish a third layer 2 link from a third user equipment, wherein the first PC5 message includes second user information of the second user equipment. The method further includes the relay user equipment transmitting a second PC5 message for modifying the second layer 2 link to the second user equipment in response to receiving the first PC5 message from the third user equipment, wherein the second PC5 message includes third user information of the third user equipment and second user information of the second user equipment.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 328,544, filed on April 7, 2022, the entire disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0003] The present disclosure relates generally to wireless communication networks, and more particularly, to methods and apparatus for a relay UE in a wireless communication system to support a connection with another remote UE. Background Art

[0004] As the demand for transmitting large amounts of data to and from mobile communication devices grows rapidly, traditional mobile voice communication networks have evolved into networks with Internet Protocol (IP) packet communications, which can provide IP-based voice, multimedia, multicast, and on-demand communication services to users of mobile communication devices.

[0005] An exemplary network structure is an Evolved Universal Terrestrial Radio Access Network (E-UTRAN). The E-UTRAN system can provide high data throughput to enable the above-mentioned IP-borne voice and multimedia services. Currently, the 3GPP standards organization is discussing new next-generation (e.g., 5G) radio technologies. Therefore, changes to the current body of 3GPP standards are currently being submitted and considered to gradually revise and finalize the 3GPP standards. Summary of the invention

[0006] A method and apparatus for supporting inter-UE relay are disclosed. In one embodiment, the method includes a relay user equipment (UE) establishing a first layer 2 link with a first UE and a second layer 2 link with a second UE, wherein the first layer 2 link and the second layer 2 link are used to forward traffic between the first UE and the second UE. The method also includes the relay UE receiving a first PC5 message for requesting to establish a third layer 2 link from a third UE, wherein the first PC5 message includes second user information of the second UE. The method further includes the relay UE transmitting a second PC5 message for modifying the second layer 2 link to the second UE in response to receiving the first PC5 message from the third UE, wherein the second PC5 message includes third user information of the third UE and the second user information of the second UE. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 A diagram is shown of a wireless communication system according to an exemplary embodiment.

[0008] Figure 2 is a block diagram of a transmitter system (also referred to as an access network) and a receiver system (also referred to as a user equipment or UE) according to an exemplary embodiment.

[0009] Figure 3 is a functional block diagram of a communication system according to an exemplary embodiment.

[0010] Figure 4 According to an exemplary embodiment Figure 3 Functional block diagram of the program code.

[0011] Figure 5 It is 3GPP TR 23.752V17.0.0 Figure 6 .8.2.1-1 is reproduced.

[0012] Figure 6 It is 3GPP TR 23.752V17.0.0 Figure 6 .8.2.2-1 is reproduced.

[0013] Figure 7 It is 3GPP TS 23.287V16.2.0 Figure 5 .2.1.4-1 reappearance.

[0014] Figure 8 It is 3GPP TS 23.287V16.2.0 Figure 6 .Reproduction of 3.3.1-1.

[0015] Fig. 9 It is 3GPP TS 23.287V16.2.0 Figure 6 .Reproduction of 3.3.4-1.

[0016] Fig.10 It is 3GPP TS.836V17.0.0 Figure 5 .Reproduction of 1-1.

[0017] Fig.11 It is 3GPP TS.836V17.0.0 Figure 5 .2-1 is reproduced.

[0018] Fig.12 It is 3GPP TS.836V17.0.0 Figure 5 .Reproduction of 5.1-1.

[0019] Fig.13It is 3GPP TS.836V17.0.0 Figure 5 .Reproduction of 5.1-2.

[0020] Fig.14 It is 3GPP TS 38.331V16.1.0 Figure 5 .8.9.1.1-1 is reproduced.

[0021] Fig.15 It is 3GPP TS 38.331V16.1.0 Figure 5 .8.9.1.1-2 is reproduced.

[0022] Fig.16 An integrated PC5 unicast link via inter-UE relay according to an exemplary embodiment is shown.

[0023] Fig.17 Data / message forwarding via inter-UE relay according to an exemplary embodiment is described.

[0024] Fig.18 Local ID allocation during an integrated unicast link establishment procedure according to an exemplary embodiment is described.

[0025] Fig.19 is a flow chart or message diagram illustrating joining a second source remote UE to a target remote UE via an inter-UE relay according to an exemplary embodiment.

[0026] Fig. 20 is a flow chart according to an exemplary embodiment.

[0027] Fig.21 is a flow chart according to an exemplary embodiment. DETAILED DESCRIPTION

[0028] The exemplary wireless communication systems and devices described below adopt wireless communication systems that support broadcast services. Wireless communication systems are widely deployed to provide various types of communications, such as voice, data, etc. These systems can be based on code division multiple access (code division multiple access, CDMA), time division multiple access (time division multiple access, TDMA), orthogonal frequency division multiple access (orthogonal frequency division multiple access, OFDMA), 3GPP Long Term Evolution (Long Term Evolution, LTE) radio access, 3GPP Long Term Evolution Advanced (Long Term Evolution Advanced, LTE-A or LTE-Advanced), 3GPP2 Ultra Mobile Broadband (Ultra MobileBroadband, UMB), WiMax, 3GPP New Radio (New Radio, NR) or some other modulation technology.

[0029] Specifically, the exemplary wireless communication systems and devices described below may be designed to support one or more standards, such as standards provided by a consortium named "3rd Generation Partnership Project" referred to herein as 3GPP, including: TR 23.752V17.0.0, "Study on System Enhancements for Proximitybased Services (ProSe) in 5G System (5G System, 5GS) (Release 17)"; TS 23.287V16.2.0, "Architecture Enhancements for 5G System (5G System, 5GS) to Support Vehicle-to-Everything (V2X) Services (Release 16)"; TS 38.836V17.0.0, "Study on NR Sidelink Relay (Release 17)"; and TS 38.331V16.1.0, "NR; Radio Resource Control (RRC) Protocol Specification (Release 16)". The standards and documents listed above are hereby expressly incorporated by reference in their entirety.

[0030] Figure 1 1 shows a multiple access wireless communication system according to an embodiment of the present invention. An access network 100 (AN) includes multiple antenna groups, one including 104 and 106, another including 108 and 110, and another including 112 and 114. Figure 1In the figure, only two antennas are shown for each antenna group, however, each antenna group may utilize more or fewer antennas. Access terminal 116 (Access terminal, AT) communicates with antennas 112 and 114, where antennas 112 and 114 transmit information to access terminal 116 via forward link 120 and receive information from access terminal 116 via reverse link 118. Access terminal (Access terminal, AT) 122 communicates with antennas 106 and 108, where antennas 106 and 108 transmit information to access terminal (Access terminal, AT) 122 via forward link 126 and receive information from access terminal (Access terminal, AT) 122 via reverse link 124. In an FDD system, communication links 118, 120, 124, and 126 may use different frequencies for communication. For example, forward link 120 may use a frequency different from the frequency used by reverse link 118.

[0031] Each antenna group and / or the area in which the antenna group is designed to communicate is often referred to as a sector of the access network. In an embodiment, the antenna groups are each designed to communicate with access terminals in a sector of the area covered by the access network 100.

[0032] In communicating over forward links 120 and 126, the transmit antennas of access network 100 may utilize beamforming in order to improve the signal-to-noise ratio of the forward links for the different access terminals 116 and 122. Furthermore, an access network that transmits to access terminals randomly dispersed throughout its coverage area using beamforming may cause less interference to access terminals in neighboring cells than an access network that transmits to all of its access terminals via a single antenna.

[0033] An access network (AN) may be a fixed station or base station for communicating with a terminal, and may also be referred to as an access point, Node B, base station, enhanced base station, evolved Node B (evolved Node B, eNB), network node, network, or some other term. An access terminal (AT) may also be referred to as user equipment (UE), a wireless communication device, terminal, access terminal, or some other term.

[0034] Figure 22 is a simplified block diagram of an embodiment of a transmitter system 210 (also referred to as an access network) and a receiver system 250 (also referred to as an access terminal (AT) or user equipment (UE)) in a MIMO system 200. At the transmitter system 210, traffic data for a number of data streams is provided from a data source 212 to a transmit (TX) data processor 214.

[0035] In one embodiment, each data stream is transmitted through a corresponding transmit antenna.TX data processor 214 formats, codes, and interleaves the traffic data for each data stream based on a particular coding scheme selected for that data stream to provide coded data.

[0036] The decoded data for each data stream may be multiplexed with pilot data using OFDM techniques. The pilot data is typically a known data pattern that is processed in a known manner and may be used at the receiver system to estimate the channel response. The multiplexed pilot and decoded data for each data stream are then modulated (i.e., symbol mapped) based on a specific modulation scheme (e.g., BPSK, QPSK, M-PSK, or M-QAM) selected for each data stream to provide modulation symbols. The data rate, coding, and modulation for each data stream may be determined by instructions executed by processor 230.

[0037] The modulation symbols for all data streams are then provided to a TX MIMO processor 220, which may further process the modulation symbols (eg, for OFDM). The TX MIMO processor 220 then converts the N T The modulation symbol stream is provided to N T transmitters (TMTR) 222a through 222t. In certain embodiments, TX MIMO processor 220 applies beamforming weights to the symbols of the data streams and to the antenna from which the symbol is being transmitted.

[0038] Each transmitter 222 receives and processes a respective symbol stream to provide one or more analog signals, and further conditions (eg, amplifies, filters, and upconverts) the analog signals to provide a modulated signal suitable for transmission over the MIMO channel. T The antennas 224a to 224t transmit N signals from the transmitters 222a to 222t. T a modulated signal.

[0039] At the receiver system 250, N RThe transmitted modulated signals are received by each antenna 252a through 252r and the received signal from each antenna 252 is provided to a respective receiver (RCVR) 254a through 254r. Each receiver 254 conditions (e.g., filters, amplifies, and downconverts) a respective received signal, digitizes the conditioned signal to provide samples, and further processes the samples to provide a corresponding "received" symbol stream.

[0040] RX data processor 260 then extracts the N R The receiver 254 receives N R received symbol streams and processes N R received symbol streams to provide N T The RX data processor 260 then demodulates, deinterleaves, and decodes each detected symbol stream to recover the traffic data for the data stream. The processing by the RX data processor 260 is complementary to the processing performed by the TX MIMO processor 220 and the TX data processor 214 at the transmitter system 210.

[0041] Processor 270 periodically determines which pre-coding matrix to use (discussed below). Processor 270 formulates a reverse link message comprising a matrix index portion and a rank value portion.

[0042] The reverse link message may include various types of information related to the communication link and / or the received data stream. The reverse link message is then processed by the TX data processor 238 (which also receives traffic data for a plurality of data streams from the data source 236), modulated by the modulator 280, conditioned by the transmitters 254a to 254r, and transmitted back to the transmitter system 210.

[0043] At the transmitter system 210, the modulated signal from the receiver system 250 is received by the antenna 224, conditioned by the receiver 222, demodulated by the demodulator 240, and processed by the RX data processor 242 to extract the reverse link message transmitted by the receiver system 250. The processor 230 then determines which precoding matrix to use to determine the beamforming weights and then processes the extracted message.

[0044] Steering Figure 3 , this figure shows an alternative simplified functional block diagram of a communication device according to one embodiment of the present invention. Figure 3 As shown in FIG. , the communication device 300 in the wireless communication system can be used to implement Figure 1 UE (or AT) 116 and 122 in or Figure 1The base station (or AN) 100 in the wireless communication system is preferably an NR system. The communication device 300 may include an input device 302, an output device 304, a control circuit 306, a central processing unit (CPU) 308, a memory 310, a program code 312, and a transceiver 314. The control circuit 306 executes the program code 312 in the memory 310 through the CPU 308, thereby controlling the operation of the communication device 300. The communication device 300 may receive a signal input by a user through an input device 302 such as a keyboard or a keypad, and may output images and sounds through an output device 304 such as a monitor or a speaker. The transceiver 314 is used to receive and transmit wireless signals, pass the received signal to the control circuit 306, and wirelessly output the signal generated by the control circuit 306. The communication device 300 in the wireless communication system may also be implemented Figure 1 AN 100 in.

[0045] Figure 4 According to an embodiment of the present invention Figure 3 4 is a simplified block diagram of program code 312 shown. In this embodiment, program code 312 includes application layer 400, layer 3 portion 402, and layer 2 portion 404, and is coupled to layer 1 portion 406. Layer 3 portion 402 generally performs radio resource control. Layer 2 portion 404 generally performs link control. Layer 1 portion 406 generally performs physical connectivity.

[0046] 3GPP TR 23.752 proposes to support inter-UE relay and related solutions for subsequent releases (e.g., Release 17 / 18) as follows:

[0047] 5.4 Key Issue #4: Support for Inter-UE Relay

[0048] 5.4.1 Overview

[0049] This key issue aims to support inter-UE relaying, including support for both in-coverage and out-of-coverage operations.

[0050] Among the possible solutions, at least the following aspects need to be considered:

[0051] - How to (re)select a nearby inter-UE relay UE?

[0052] - Whether and how the network can control the inter-UE relay operation, including at least how to:

[0053] - Authorize inter-UE relay, for example, authorize the UE as an inter-UE relay?

[0054] - Authorize remote UE to access inter-UE relay?

[0055] - Provide visibility of source / target UEs and inter-UE relays to the network for e.g. charging purposes?

[0056] -How to establish the connection between source UE and target UE via inter-UE relay?

[0057] -How to provide an end-to-end QoS framework to meet QoS requirements (e.g., data rate, reliability, latency)?

[0058] -How to enhance the system architecture to provide security protection for relay connections?

[0059] - How to provide a mechanism for path change, for example in case of inter-UE relay change?

[0060] NOTE 1: In order to participate in NG-RAN, coordination with the RAN WG is required.

[0061] Note 2: For security aspects, coordination with SA WG3 is required.

[0062] […]

[0063] 6.8 Solution #8: Inter-UE Relay Selection without Relay Discovery

[0064] 6.8.1 Description

[0065] When the source UE wants to communicate with the target UE, it will first try to discover the target UE by sending a direct communication request or request message with the target UE information. If the source UE cannot reach the target UE directly, it will try to discover the inter-UE relay to reach the target UE, which can also trigger the relay to discover the target UE. To be more efficient, this solution attempts to integrate target UE discovery with inter-UE relay discovery and selection, including two alternatives:

[0066] -Alternative 1: Inter-UE relay discovery and selection may be integrated into the unicast link establishment procedure as described in section 6.3.3 of TS 23.287 [5].

[0067] -Alternative 2: Inter-UE relay discovery and selection is integrated into the Model B direct discovery procedure.

[0068] It is proposed to add a new field in the direct communication request or request message to indicate whether relay can be used in the communication. The field may be called relay_indication. When a UE wants to broadcast a direct communication request or request message, it indicates in the message whether inter-UE relay can be used. For Release 17, it is assumed that the value of the indication is limited to a single hop.

[0069] When an inter-UE relay receives a direct communication request or request message with relay_indication set, it should decide whether to forward the message (i.e., modify the message and broadcast it in its vicinity) based on, for example, the relay service code (if any), application ID, authorization policy (e.g., relay for a specific ProSe service), the current traffic load of the relay, the radio conditions between the source UE and the relay UE, etc.

[0070] It may be the case that multiple inter-UE relays may be used to reach the target UE, or the target UE may also receive a direct communication request or request message directly from the source UE. The target UE may select which one to reply based on, for example, signal strength, local policy (e.g., traffic load of the inter-UE relays), relay service code (if any), or operator policy (e.g., always prefer direct communication or use only some specific inter-UE relays).

[0071] The source UE may receive responses from multiple inter-UE relays and may also receive responses directly from the target UE, the source UE selecting the communication path based on, for example, signal strength or operator policy (eg, always preferring direct communication or using only some specific inter-UE relays).

[0072] 6.8.2 Procedure

[0073] 6.8.2.1 Integrating Inter-UE Relay Discovery and Selection into Unicast Link Establishment Procedure (Alternative 1)

[0074] [3GPP TR 23.752 V17.0.0 entitled "5G ProSe UE-to-UE relay selection (Alternative 1)" Figure 6 .8.2.1-1 Reproduced as Figure 5 ]

[0075] Figure 6 .8.2.1-1Describe the procedures for the proposed method.

[0076] 0. Authorize the UE to use services provided by the inter-UE relay. Authorize the inter-UE relay to provide services that relay traffic between UEs. Authorization and parameter provisioning can use solutions from KI#8, such as Sol#36. Authorization can be performed when the UE / relay registers with the network. Security-related parameters can be provisioned so that the UE and relay can verify authorization with each other when needed.

[0077] 1.UE-1 wants to establish unicast communication with UE-2, and the communication can be through a direct link with UE-2 or via an inter-UE relay. Then, UE-1 broadcasts a direct communication request with relay_indication enabled. The message will be received by relay-1, relay-2. If UE-2 is near UE-1, the message can also be received by UE-2. UE-1 includes source UE information, target UE information, application ID, and relay service code (if any). If UE-1 does not want to involve relays in the communication, it will disable relay_indication.

[0078] NOTE 1: The data type of relay_indication may be determined in stage 3. The details of the direct communication request / accept message will be determined in stage 3.

[0079] 2. Relay-1 and Relay-2 decide to participate in the procedure. They broadcast a new direct communication request message in their vicinity without enabling relay_indication. If a relay receives this message, it will simply discard the message. When a relay broadcasts a direct communication request message, it includes the source UE information, target UE information and relay UE information (e.g., relay UE ID) in the message, and uses the relay's L2 address as the source layer 2 ID. The relay maintains the association between the source UE information (e.g., source UE L2 ID) and the new direct communication request.

[0080] 3. UE-2 receives direct communication request from relay-1 and relay-2. If UE-2 is in the communication range of UE-1, UE-2 may also directly receive a direct communication request message from UE-1.

[0081] 4. UE-2 selects Relay-1 and replies with a Direct Communication Accept message. If UE-2 receives a Direct Communication Request directly from UE-1, it may choose to establish a direct communication link by sending a Direct Communication Accept message directly to UE-1. After receiving the Direct Communication Accept, the Inter-UE Relay retrieves the Source UE information stored in step 2 and sends a Direct Communication Accept message to the Source UE with the Relay UE information added to the message.

[0082] After step 4, UE-1 and UE-2 respectively establish PC5 links with the selected inter-UE relay.

[0083] NOTE 2: Security establishment between UE1 and Relay-1 and between Relay-1 and UE-2 is performed before Relay-1 and UE-2 send direct communication accept messages. The details of the authentication / security establishment procedure are determined by SA WG3. If a PC5 link already exists between the source (or target) UE and a relay that can be used for relay services, the security establishment procedure can be skipped.

[0084] 5. UE-1 receives a direct communication accept message from relay-1. UE-1 selects a path based on, for example, policy (e.g., always select a direct path when possible), signal strength, etc. If UE-1 receives a direct communication accept / response message requesting acceptance directly from UE-2, it may choose to establish a direct PC5 L2 link with UE-2, as described in Section 6.3.3 of TS 23.287 [5], and then skip step 6.

[0085] 6a. For the L3 inter-UE relay case, UE-1 and UE-2 complete establishing a communication link via the selected inter-UE relay. The link establishment information may vary depending on the relay type (e.g., L2 or L3 relay). UE-1 and UE-2 may then communicate via the relay. Regarding the IP address allocation of the source / remote UE, the address may be allocated by the relay or by the UE itself (e.g., link-local IP address), as defined in Section 6.3.3 of TS 23.287 [5].

[0086] 6b. For the layer 2 inter-UE relay case, the source UE and the target UE may establish an end-to-end PC5 link via the relay. UE-1 sends a unicast E2E direct communication request message to UE-2 via relay-1, and UE-2 responds to UE-1 with a unicast E2E direct communication accept message via relay-1. Relay-1 delivers the message based on the identity information of UE-1 / UE-2 in the adaptation layer.

[0087] NOTE 3: How Relay-1 can deliver messages based on the identity information of UE-1 / UE-2 in the Adaptation Layer requires collaboration with RAN2 during the normative phase.

[0088] Note 4: For relay or path selection, the source UE may set a timer after issuing a direct communication request to collect corresponding response messages before making a decision. Similarly, the target UE may also set a timer after receiving the first copy of the direct communication request / message to collect multiple copies of the message from different paths before making a decision.

[0089] NOTE 5: When a UE receives a message from an inter-UE relay for the first time, the UE needs to verify that the relay is authorized as an inter-UE relay. Similarly, an inter-UE relay may also need to verify that the UE is authorized to use the relay service. The verification details and how to ensure communication between two UEs via an inter-UE relay will be defined by SA WG3.

[0090] 6.8.2.2 Inter-UE Relay Discovery and Selection Integrated into Model B Direct Discovery Procedure (Alternative 2)

[0091] Figure 6The procedures for inter-UE relay discovery model B are described in .8.2.2-1, and the discovery / selection procedures are separated from the hop-by-hop and end-to-end link establishment.

[0092] [3GPP TR 23.752 V17.0.0 entitled "5G ProSe UE-to-UE relay selection (Alternative 2)" Figure 6 .8.2.2-1 Reproduced as Figure 6 ]

[0093] 1. UE-1 broadcasts a discovery request message carrying UE-1 information, target UE information (UE-2), application ID, relay service code (if any), and UE-1 may also indicate that relay_indication is enabled.

[0094] 2. Upon receiving the discovery request, the candidate relay UE-R broadcasts a discovery request carrying UE-1 information, UE-R information, target UE information. The relay UE-R uses the relay's L2 address as the source layer 2 ID.

[0095] 3. The target UE-2 responds to the discovery message. If UE-2 receives the discovery request message in step 1, then UE-2 responds to the discovery response message with UE-1 information and UE-2 information in step 3b. If UE-2 does not receive the discovery request in step 2, then UE-2 responds to the discovery response message with UE-1 information, UE-R information, and UE-2 information in step 3a.

[0096] 4. Upon receiving the discovery response in step 3a, UE-R sends a discovery response with UE-1 information, UE-R information, UE-2 information. If more than one candidate relay UE responds to the discovery response message, UE-1 may select a relay UE based on, for example, implementation or link qualifications.

[0097] 5. The source UE and the target UE may need to establish a PC5 link with the relay before communicating with each other. If a PC5 link already exists between UE-1 and UE-R that can be used for relay, step 5a can be skipped. If a PC5 link already exists between UE-2 and UE-R that can be used for relay, step 5b can be skipped.

[0098] 6a. Same as step 6a described in Section 6.8.2.1.

[0099] 6b. For layer 2 inter-UE relay, an E2E unicast direct communication request message is sent from UE1 to the selected relay via the per-hop link (established in step 5a) and the adaptation layer information identifying the peer UE (UE3) as the destination. The inter-UE relay delivers the E2E message based on the identity information of the peer UE in the adaptation layer. The initiator (UE1) knows the adaptation layer information identifying the peer UE (UE3) after the discovery procedure. UE3 responds with an E2E unicast direct communication accept message in the same manner.

[0100] NOTE 1: For the Layer 2 inter-UE relay case, whether step 5b is performed before step 6b or triggered during step 6b will be decided at the normative stage.

[0101] NOTE 2: How Relay-1 can deliver messages based on the identity information of UE-1 / UE-2 in the Adaptation Layer requires collaboration with RAN2 during the normative phase.

[0102] 6.8.3 Impact on Services, Entities, and Interfaces

[0103] Impact on UEs supporting new relay-related functions.

[0104] 3GPP TS 23.287 specifies unicast mode Vehicle-to-Everything (V2X) communication over the PC5 reference point, Layer 2 link establishment, link identifier update, and Layer 2 link modification over the PC5 reference point as follows:

[0105] 5.2.1.4 Unicast mode communication via PC5 reference point

[0106] Unicast communication mode is only supported by NR based PC5 reference point. Figure 5 .2.1.4-1 describes an example of a PC5 unicast link.

[0107] [3GPP TS 23.287 V16.2.0, entitled "Example of PC5 Unicast Links" Figure 5 .2.1.4-1 Reproduced as Figure 7 ]

[0108] When V2X communications are carried over PC5 unicast links, the following principles apply:

[0109] - A PC5 unicast link between two UEs allows V2X communication between one or more pairs of peer V2X services in these UEs. All V2X services in a UE using the same PC5 unicast link use the same application layer ID.

[0110] NOTE 1: Due to privacy reasons, the application layer ID may change over time as described in clauses 5.6.1.1 and 6.3.3.2. This does not cause re-establishment of the PC5 unicast link. The UE triggers the Link Identifier Update procedure as specified in clause 6.3.3.2.

[0111] - If one or more V2X service types (e.g., PSID or ITS-AID) are associated with at least one pair of peer application layer IDs of a PC5 unicast link, then the PC5 unicast link supports these V2X service types. Figure 5 As illustrated in .2.1.4-1, UE A and UE B have two PC5 unicast links, one between peer application layer ID 1 / UE A and application layer ID 2 / UE B and one between peer application layer ID 3 / UE A and application layer ID 4 / UE B.

[0112] NOTE 2: The source UE is not required to know whether different target application layer IDs on different PC5 unicast links belong to the same target UE.

[0113] -PC5 unicast links support V2X communications using a single network layer protocol (e.g., IP or non-IP).

[0114] - PC5 unicast links support the per-flow QoS model as specified in Section 5.4.1.

[0115] When the application layer in the UE initiates data transfer for a V2X service type that requires unicast communication mode over the PC5 reference point:

[0116] - If the pair of peer application layer IDs and the network layer protocol of this PC5 unicast link are the same as those required by the application layer in the UE for this V2X service, then the UE shall reuse the existing PC5 unicast link and modify the existing PC5 unicast link as specified in Section 6.3.3.4 to add this V2X service; otherwise

[0117] - The UE shall trigger the establishment of a new PC5 unicast link as specified in clause 6.3.3.1.

[0118] After successfully establishing the PC5 unicast link, UE A and UE B use the same pair of Layer 2 IDs for subsequent PC5-S signaling message exchanges and V2X service data transmissions, as specified in Section 5.6.1.4. The V2X layer of the transmitting UE indicates to the AS layer whether the transmission is for PC5-S signaling messages (i.e., direct communication request / acceptance, link identifier update request / response / confirmation, disconnect request / response, link modification request / acceptance) or for V2X service data.

[0119] For each PC5 unicast link, the UE allocates a different PC5 link identifier that uniquely identifies the PC5 unicast link in the UE during the lifetime of the PC5 unicast link. Each PC5 unicast link is associated with a unicast link profile, which includes:

[0120] - V2X service type (e.g., PSID or ITS-AID); and

[0121] - UE A's application layer ID and layer 2 ID; and

[0122] - UE B's Application Layer ID and Layer 2 ID; and

[0123] - Network layer protocol used over PC5 unicast links; and

[0124] - For each V2X service type, a set of PC5 QoS Flow Identifiers (PFIs). Each PFI is associated with a QoS parameter (ie, PQI).

[0125] For privacy reasons, the Application Layer ID and Layer 2 ID may change during the lifetime of a PC5 unicast link as described in Sections 5.6.1.1 and 6.3.3.2, and if so, should be updated in the unicast link profile accordingly. The UE indicates a PC5 unicast link to the V2X application layer using the PC5 link identifier, so the V2X application layer identifies the corresponding PC5 unicast link, even if there is more than one unicast link associated with one V2X service type (e.g., the UE establishes multiple unicast links with multiple UEs for the same V2X service type).

[0126] Following a Layer 2 link modification of an established PC5 unicast link as specified in clause 6.3.3.4 or a Layer 2 link identifier update as specified in clause 6.3.3.2, the unicast link profile shall be updated accordingly.

[0127] The V2X service information and QoS information are carried in the PC5-S signaling message and exchanged between two UEs as specified in Section 6.3.3. Based on the exchanged information, the PFI is used to identify the V2X service. When the receiving UE receives the V2X service data through the established PC5 unicast link, the receiving UE determines the appropriate V2X service based on the PFI to forward the received V2X service data to the upper layer.

[0128] After receiving an indication from the AS layer to release the PC5-RRC connection due to RLF, the V2X layer in the UE locally releases the PC5 unicast link associated with this PC5-RRC connection. The AS layer uses the PC5 link identifier to indicate the release of the PC5 unicast link of the PC5-RRC connection.

[0129] When the PC5 unicast link has been released as specified in Section 6.3.3.3, the V2X layer of each UE for the PC5 unicast link notifies the AS layer that the PC5 unicast link has been released. The V2X layer uses the PC5 link identifier to indicate the released unicast link.

[0130] […]

[0131] 5.6.1.4 Identifiers for unicast mode V2X communications over the PC5 reference point

[0132] For unicast mode V2X communications over the PC5 reference point, the destination Layer 2 ID used depends on the communicating peer. The Layer 2 ID of the communicating peer, identified by the application layer ID, may be discovered during establishment of the PC5 unicast link, or known to the UE via previous V2X communications (e.g., an existing or previous unicast link to the same application layer ID), or obtained from an application layer service announcement. The initial signaling for establishing a PC5 unicast link may use the known Layer 2 ID of the communicating peer, or a preset destination Layer 2 ID associated with a V2X service type (e.g., PSID / ITS-AID) configured for PC5 unicast link establishment, as specified in Section 5.1.2.1. As specified in Section 6.3.3.1, during the PC5 unicast link establishment procedure, the Layer 2 IDs are exchanged and applied to future communications between the two UEs.

[0133] The application layer ID is associated with one or more V2X applications within the UE. If a UE has more than one application layer ID, then from the perspective of a peer UE, each application layer ID of the same UE may be considered as an application layer ID of a different UE.

[0134] Since the V2X application layer does not use the Layer 2 ID, the UE maintains a mapping between the application layer ID and the source Layer 2 ID for the PC5 unicast link. This allows the source Layer 2 ID to be changed without interrupting the V2X application.

[0135] When the application layer ID changes, the source layer 2 ID of the PC5 unicast link should be changed if the link is used for V2X communication with the changed application layer ID.

[0136] Based on the privacy configuration as specified in section 5.1.2.1, updating the new identifier of the source UE to the peer UE for the established unicast link may result in the peer UE changing its Layer 2 ID and optionally IP address / prefix (if IP communication is used as defined in section 6.3.3.2).

[0137] A UE may establish multiple PC5 unicast links with a peer UE and use the same or different source layer 2 IDs for these PC5 unicast links.

[0138] […]

[0139] 6.3.3.1 Layer 2 link establishment over PC5 reference point

[0140] In order to perform V2X communication in unicast mode over the PC5 reference point, the UE is configured with relevant information as described in Section 5.1.2.1.

[0141] Figure 6 .3.3.1-1 shows the Layer 2 link establishment procedure for unicast mode V2X communication over the PC5 reference point.

[0142] [3GPP TS 23.287 V16.2.0 is titled "Layer 2 link establishment procedure (Layer-2 link establishment

[0143] procedure) Figure 6 .3.3.1-1 Reproduced as Figure 8 ]

[0144] 1. The UE determines the destination Layer 2 ID for signaling reception for PC5 unicast link establishment as specified in Section 5.6.1.4. The destination Layer 2 ID is configured with the UE as specified in Section 5.1.2.1.

[0145] 2. The V2X application layer in UE-1 provides application information for PC5 unicast communication. The application information includes the V2X service type (e.g., PSID or ITS-AID) of the V2X application and the application layer ID of the initiating UE. The application information may include the application layer ID of the target UE.

[0146] The V2X application layer in UE-1 may provide the V2X application requirements for this unicast communication. UE-1 determines the PC5 QoS parameters and PFI as specified in Section 5.4.1.4.

[0147] If UE-1 decides to reuse the existing PC5 unicast link as specified in section 5.2.1.4, the UE triggers the Layer 2 Link Modification procedure as specified in section 6.3.3.4.

[0148] 3. UE-1 sends a direct communication request message to initiate the unicast layer 2 link establishment procedure. The direct communication request message contains:

[0149] - Source user information: the application layer ID of the originating UE (ie, the application layer ID of UE-1).

[0150] - If the V2X application layer provides the target UE's application layer ID in step 2, the following information is included:

[0151] - Target user information: Application layer ID of the target UE (ie, the application layer ID of UE-2).

[0152] - V2X service information: Information about the V2X service requesting Layer 2 link establishment (e.g., PSID or ITS-AID).

[0153] - Security information: information used to establish security.

[0154] NOTE 1 Security information and the necessary protection of source user information and destination user information are defined by SA WG3.

[0155] As specified in Sections 5.6.1.1 and 5.6.1.4, the source layer 2ID and destination layer 2ID used to send the direct communication request message are determined. The destination layer 2ID can be a broadcast or unicast layer 2ID. When a unicast layer 2ID is used, the target user information should be included in the direct communication request message.

[0156] UE-1 sends a direct communication request message via PC5 by broadcast or unicast using the source layer 2ID and the destination layer 2ID.

[0157] 4. Establish security for UE-1 as follows:

[0158] 4a. If the target user information is included in the direct communication request message, the target UE (ie, UE-2) responds by establishing security with UE-1.

[0159] 4b. If the target user information is not included in the direct communication request message, the UE interested in using the notified V2X service over the PC5 unicast link with UE-1 responds by establishing security with UE-1. NOTE 2: Signaling for security procedures is defined by SA WG3.

[0160] When security protection is enabled, UE-1 sends the following information to the target UE:

[0161] - If using IP communication, then:

[0162] -IP address configuration: For IP communication, this link requires IP address configuration, and it indicates the following values

[0163] one of the:

[0164] - If the initiating UE supports the IPv6 address allocation mechanism, i.e. acts as an IPv6 router, then

[0165] "IPv6 router"; or

[0166] - If the initiating UE does not support the IPv6 address allocation mechanism, then "does not support IPv6 address allocation".

[0167] - Link-local IPv6 address: If UE-1 does not support the IPv6 IP address allocation mechanism, i.e., the IP address configuration indicates "IPv6 address allocation is not supported", then a link-local IPv6 address is formed locally based on RFC 4862

[21] .

[0168] -QoS Information: Information about PC5 QoS flows. For each PC5 QoS flow, PFI and corresponding PC5 QoS parameters (ie, PQI and conditionally other parameters such as MFBR / GFBR, etc.).

[0169] Determine the source Layer 2 ID for the security establishment procedure as specified in clauses 5.6.1.1 and 5.6.1.4.

[0170] The destination Layer 2 ID is set to the source Layer 2 ID of the received direct communication request message.

[0171] Upon receiving the Security Setup Procedure message, UE-1 obtains the Layer 2 ID of the peer UE for future communications for signaling and data traffic for this unicast link.

[0172] 5. One or more target UEs that have successfully established security with UE-1 send a direct communication accept message to UE-1:

[0173] 5a. (Layer 2 link establishment towards UE) If the target user information is contained in the direct communication request message, then if the application layer ID for UE-2 matches, the target UE (ie, UE-2) responds with a direct communication accept message.

[0174] 5b. (Layer 2 Link Establishment for V2X Services) If the direct communication request message does not contain target user information, the UE interested in using the notified V2X service (in Figure 6 .UE-2 and UE-4 in 3.3.1-1) respond to the request by sending a direct communication accept message.

[0175] The direct communication acceptance message contains:

[0176] -Source user information: the application layer ID of the UE that sends the direct communication acceptance message.

[0177] -QoS Information: Information about PC5 QoS flows. For each PC5 QoS flow, the PFI requested by UE-1 and the corresponding PC5 QoS parameters (ie, PQI and conditionally other parameters, such as MFBR / GFBR, etc.).

[0178] - If using IP communication, then:

[0179] -IP Address Configuration: For IP communication, this link requires IP address configuration, and it indicates one of the following values:

[0180] - "IPv6 Router" if the target UE supports the IPv6 address allocation mechanism, i.e. acts as an IPv6 router; or

[0181] - If the target UE does not support the IPv6 address allocation mechanism, then "does not support IPv6 address allocation".

[0182] - Link-local IPv6 address: If the target UE does not support the IPv6 IP address allocation mechanism, i.e. the IP address configuration indicates "IPv6 address allocation is not supported", and UE-1 includes a link-local IPv6 address in the Direct Communication Request message, then a link-local IPv6 address is formed locally based on RFC 4862

[21] . The target UE shall include a non-conflicting link-local IPv6 address.

[0183] If both UEs (ie, the initiating UE and the target UE) are selected to use link-local IPv6 addresses, they shall disable dual address detection as defined in RFC 4862

[21] .

[0184] NOTE 3: When the initiating UE or the target UE indicates support for IPv6 routers, the corresponding address configuration procedure shall be performed after the layer 2 link is established and the link-local IPv6 address shall be ignored.

[0185] The V2X layer of the UE that establishes the PC5 unicast link passes the PC5 link identifier and PC5 unicast link related information allocated for the unicast link down to the AS layer. The information related to the PC5 unicast link includes layer 2ID information (i.e., source layer 2ID and destination layer 2ID). This enables the AS layer to maintain the PC5 link identifier and PC5 unicast link related information.

[0186] 6. The V2X service data is transmitted via the established unicast link as follows:

[0187] The PC5 link identifier and PF are provided to the AS layer together with the V2X service data.

[0188] Additionally, layer 2 ID information (ie, source layer 2 ID and destination layer 2 ID) is optionally provided to the AS layer.

[0189] NOTE 4: It is up to the UE implementation to provide the Layer 2 ID information to the AS layer.

[0190] UE-1 uses the source layer 2 ID (i.e., the layer 2 ID of UE-1 for this unicast link) and the destination layer 2 ID

[0191] (i.e., the Layer 2 ID of the peer UE for this unicast link) to send V2X service data.

[0192] NOTE 5: The PC5 unicast link is bidirectional, so UE-1’s peer UE can send V2X service data to UE-1 via the unicast link with UE-1.

[0193] […]

[0194] 6.3.3.4 Layer 2 Link Modification for Unicast Links

[0195] Figure 6 .3.3.4-1 shows the Layer 2 link modification procedure for unicast links. This procedure is used to:

[0196] -Add new V2X services to existing PC5 unicast links.

[0197] -Remove V2X services from existing PC5 unicast links.

[0198] -Add new PC5 QoS flow in existing PC5 unicast link.

[0199] - Modify an existing PC5 QoS flow in an existing PC5 unicast link.

[0200] - Remove existing PC5 QoS flows in existing PC5 unicast links.

[0201] [3GPP TS 23.287 V16.2.0 entitled "Layer 2 link modification procedure

[0202] procedure) Figure 6 .3.3.4-1 Reproduced as Fig. 9 ]

[0203] 0. UE-1 and UE-2 have a unicast link established as described in Section 6.3.3.1.

[0204] 1. The V2X application layer in UE-1 provides application information for PC5 unicast communication. The application information contains the V2X service type (e.g., PSID or ITS-AID) of the V2X application and the application layer ID of the initiating UE. The application layer ID of the target UE may be included in the application information. If UE-1 decides to reuse the existing PC5 unicast link as specified in Section 5.2.1.4 and therefore decides to modify the unicast link established with UE-2, then UE-1 sends a link modification request to UE-2.

[0205] The link modification request message contains:

[0206] a) To add new V2X services to an existing PC5 unicast link:

[0207] - V2X service information: Information about the V2X service to be added (eg, PSID or ITS-AID).

[0208] -QoS Information: Information about the PC5 QoS flow for each V2X service to be added. For each PC5 QoS flow, PFI and corresponding PC5 QoS parameters (ie, PQI and conditionally other parameters, such as MFBR / GFBR, etc.).

[0209] b) Remove V2X services from existing PC5 unicast links:

[0210] - V2X service information: Information about the V2X service to be removed (eg, PSID or ITS-AID).

[0211] c) Add a new PC5 QoS flow to the existing PC5 unicast link:

[0212] - V2X service information: Information about the V2X service that needs to add a new QoS flow (e.g. PSID or ITS-AID).

[0213] -QoS Information: Information about the PC5 QoS flow to be modified. For each PC5 QoS flow, PFI and corresponding PC5 QoS parameters (ie, PQI and conditionally other parameters, such as MFBR / GFBR, etc.).

[0214] d) To modify a PC5 QoS flow in an existing PC5 unicast link:

[0215] -QoS Information: Information about the PC5 QoS flow to be modified. For each PC5 QoS flow, PFI and corresponding PC5 QoS parameters (ie, PQI and conditionally other parameters, such as MFBR / GFBR, etc.).

[0216] e) To remove the PC5 QoS flow from an existing PC5 unicast link:

[0217] -PFI.

[0218] 2. UE-2 responds with a Link Modification Accept message.

[0219] The link modification acceptance message contains:

[0220] - For cases a), c) and d) described in step 1:

[0221] -QoS Information: Information about PC5 QoS flows. For each PC5 QoS flow, PFI and corresponding PC5 QoS parameters (ie, PQI and conditionally other parameters, e.g., MFBR / GFBR, etc.).

[0222] The V2X layer of each UE provides information about the unicast link modification to the AS layer. This enables the AS layer to update the context related to the modified unicast link.

[0223] 3GPP TS 38.836 specifies the following for sidelink-based UE relay:

[0224] 5. Inter-UE Relay Based on Sidelink

[0225] 5.1 Scenarios, assumptions and requirements

[0226] Inter-UE relaying enables coverage extension and power saving of sidelink transmissions between two sidelink UEs. The coverage scenarios considered in this study are as follows:

[0227] 1) All UEs (source UE, relay UE, destination UE) are within coverage.

[0228] 2) All UEs (source UE, relay UE, destination UE) are out of coverage.

[0229] 3) Partial coverage, where at least one of the UEs involved in the relay (source UE, relay UE, destination UE) is within the coverage, and at least one of the UEs involved in the relay is out of the coverage.

[0230] RAN2 will strive to find a common solution for both in-coverage and out-of-coverage scenarios. For inter-UE relay, the scenario where the UE can be in the coverage of different cells is supported.

[0231] Figure 5 .1-1 shows the considered scenario of inter-UE relay. Figure 5 In .1-1, coverage implies that the source / destination UE and / or inter-UE relay UE are within the coverage and can access the network on Uu.

[0232] [3GPP TS.836 V17.0.0 entitled "Scenarios for UE-to-UE Relay (where the coverage status is not shown)" Figure 5 .1-1 reproduced as Fig.10 ]

[0233] PC5 assumes NR side link between remote UE and inter-UE relay.

[0234] The cross-RAT configuration / control of source UE, inter-UE relay and destination UE is not considered, i.e., the eNB / ng-eNB does not control / configure the NR source UE, target UE or inter-UE relay UE. For inter-UE relay, this study focuses on unicast data services between source UE and destination UE.

[0235] Configuring / scheduling a UE (source UE, destination UE or inter-UE relay UE) by a SN to perform NR sidelink communication is out of the scope of this study.

[0236] For inter-UE relaying, it is assumed that the remote UE has an active end-to-end connection only via a single relay UE at a given time.

[0237] Once the PC5 link is established between the source UE, the inter-UE relay and the destination UE, data relay between the source UE and the destination UE may occur.

[0238] No restrictions are assumed regarding the RRC state of any UE involved in inter-UE relay.

[0239] During this release of mobility, the requirement for service continuity is only for UE-to-network relaying and not for inter-UE relaying.

[0240] 5.2 Discovery

[0241] Model A and Model B discovery models as defined in Section 5.3.1.2 of TS 23.303 [3] are supported for inter-UE relay and integrated PC5 unicast link establishment procedures may be supported based on SA2 conclusions. Figure 5 The protocol stack for discovery messages is described in .2-1.

[0242] [3GPP TS.836 V17.0.0 entitled "Protocol Stack of Discovery Message for UE-to-UE Relay" Figure 5 .2-1 reproduced as Fig.11 ]

[0243] When triggered by upper layers, a relay UE or a remote UE is allowed to transmit a discovery message.

[0244] Both remote UE and relay UE may rely on pre-configuration unless the relevant radio configuration is provided by the network via system information or dedicated signaling.

[0245] The resource pool for transmitting discovery messages may be shared or separate from the resource pool for data transmission.

[0246] - For shared resource pools and separate resource pools, new LCIDs are introduced for discovery messages, ie, discovery messages are carried by new SL SRBs.

[0247] - Within separate resource pools, discovery messages are processed equally to each other during the LCP procedure.

[0248] 5.3 Relay Selection (Reselection) Criteria and Procedures

[0249] The baseline solution for relay selection (reselection) is as follows:

[0250] Radio measurements at the PC5 interface are considered as part of the (re)selection criteria for the relay.

[0251] - The remote UE uses at least the radio signal strength measurements of the sidelink discovery messages to assess whether the PC5 link quality of the relay UE meets the relay selection and reselection criteria.

[0252] - When a remote UE is connected to a relay UE, it may use SL-RSRP measurements on the sidelink unicast link to assess whether the PC5 link quality of the relay UE meets the relay reselection criteria.

[0253] Additional details about PC5 radio measurement criteria, for example in the case of no transmission on the sidelink unicast link, may be discussed in the WI phase. If the remote UE has a PC5-RRC connection with the relay UE, how to perform RSRP measurements based on RSRP of discovery messages and / or SL-RSRP may be decided in the WI phase.

[0254] For relay selection (reselection), the remote UE compares the relay UE's PC5 radio measurements with thresholds configured or pre-configured by the gNB. The remote UE also needs to consider higher layer criteria for relay selection (reselection), but the details can be left to SA2. Relay selection (reselection) can be triggered by upper layers of the remote UE.

[0255] If the NR sidelink signal strength of the current sidelink relay is below a (pre-)configured threshold, then relay reselection should be triggered. And, if the remote UE detects RLF of the PC5 link with the current relay UE, then relay reselection may be triggered.

[0256] The above baseline for relay (re)selection is applicable to both L2 and L3 relay solutions.Additional AS layer criteria may be considered in the WI phase for both L2 and L3 inter-UE relay solutions.

[0257] For relay selection (reselection), when the remote UE has multiple suitable relay UE candidates that meet all AS layer and higher layer criteria and the remote UE needs to select a relay UE by itself, it is up to the UE implementation to decide which relay UE to select.

[0258] As captured in TR 23.752, Solution #8 and Solution #50 in TR 23.752 are considered as baseline solutions for L2 and L3 inter-UE relay reselection, and Solution #8 and Solution #11 in TR 23.752 are considered as baseline solutions for L3 inter-UE relay selection.

[0259] 5.4 Relay / Remote UE Authorization

[0260] RAN2 concludes that the authorization of both the Relay UE and the Remote UE has no RAN2 impact.

[0261] 5.5 Layer 2 Relay

[0262] 5.5.1 Architecture and Protocol Stack

[0263] For L2 inter-UE relay architecture, the protocol stack is similar to L2UE to network relay except for the fact that the termination points are two remote UEs. The protocol stack for user plane and control plane for L2 inter-UE relay architecture is described in Figure 5 .5.1-1 and Figure 5 .Described in 5.1-2.

[0264] An adaptation layer is supported on the second PC5 link (i.e., the PC5 link between the relay UE and the destination UE) for L2 inter-UE relay. For L2 inter-UE relay, the adaptation layer is placed on the RLC sublayer for CP and UP on the second PC5 link. Sidelink SDAP / PDCP and RRC terminate between the two remote UEs, while RLC, MAC and PHY terminate in each PC5 link.

[0265] [3GPP TS.836 V17.0.0 entitled "User plane protocol stack for L2 UE-to-UE Relay" Figure 5 .5.1-1 reproduced as Fig.12 ]

[0266] [3GPP TS.836 V17.0.0 entitled "Control plane protocol stack for L2 UE-to-UE Relay" Figure 5 .5.1-2 reproduced as Fig.13 ]

[0267] For the first hop of L2 inter-UE relay:

[0268] - The first hop PC5 adaptation layer between the remote UE SL radio bearers and the first hop PC5 RLC channels supports N:1 mapping for relaying.

[0269] - Supporting an adaptation layer on the first PC5 hop between a source remote UE and a relay UE to identify traffic destined for different destination remote UEs.

[0270] For the second hop of L2 inter-UE relay:

[0271] - The second hop PC5 adaptation layer may be used to support bearer mapping between incoming RLC channels on the first PC5 hop and outgoing RLC channels on the second PC5 hop at the relay UE.

[0272] - The PC5 adaptation layer supports N:1 bearer mapping between multiple incoming PC5 RLC channels on the first PC5 hop and one outgoing PC5 RLC channel on the second PC5 hop, and supports remote UE identification functionality.

[0273] For L2 inter-UE relay:

[0274] - Identity information of the remote UE end-to-end radio bearers is contained in the adaptation layer in the first and second PC5 hops.

[0275] - In addition, the identity information of the source remote UE and / or the identity information of the destination remote UE are candidate information to be included in the adaptation layer, which will be decided in the WI stage.

[0276] 5.5.2QoS

[0277] The QoS handling for L2 inter-UE relay is influenced by upper layers, such as solution #31 in TR 23.752 studied by SA2.

[0278] 5.5.3 Security

[0279] As described in Section 6.9.1.2 (Solution #9) of TR 23.752, in case of L2 inter-UE relay, security is established at the PDCP layer in an end-to-end manner between UE1 and UE2. The security aspect requires confirmation of SA3.

[0280] 5.5.4 Control Plane Programs

[0281] RAN2 considers the SA2 solution in TR 23.752 [6] as the baseline. Other RAN2 impacts (if any) may be discussed in the WI phase.

[0282] 3GPP TS 38.331 specifies the sidelink radio resource control (RRC) reconfiguration for NR sidelink communications as follows:

[0283] 5.8.9.1 Sidelink RRC Reconfiguration

[0284] 5.8.9.1.1 Overview

[0285] [3GPP TS 38.331 V16.1.0 entitled "Sidelink RRC reconfiguration, successful" Figure 5 .8.9.1.1-1 reproduced as Fig.14 ]

[0286] [3GPP TS 38.331 V16.1.0 entitled "Sidelink RRC reconfiguration, failure" Figure 5 .8.9.1.1-2 reproduced as Fig.15 ]

[0287] The purpose of this procedure is to modify the PC5-RRC connection, such as establishing / modifying / releasing sidelink DRBs, configuring NR sidelink measurements and reporting, configuring sidelink CSI reference signal resources and CSI reporting latency bounds.

[0288] In the following cases, the UE may initiate the sidelink RRC reconfiguration procedure and perform the operations in subclause 5.8.9.1.2 on the corresponding PC5-RRC connection:

[0289] - Release the sidelink DRB associated with the peer UE as specified in subclause 5.8.9.1a.1;

[0290] - Establishing a sidelink DRB associated with the peer UE as specified in subclause 5.8.9.1a.2;

[0291] - modifying the parameters contained in the SLRB-Config of the sidelink DRB associated with the peer UE, as specified in section 5.8.9.1.5a.2;

[0292] - Configuration of peer UE to perform NR sidelink measurements and reporting.

[0293] -Configuration of sidelink CSI reference signal resources and CSI reporting delay bound.

[0294] In RRC_CONNECTED, the UE applies the NR sidelink communication parameters provided in RRCReconfiguration (if present). In RRC_IDLE or RRC_INACTIVE, the UE applies the NR sidelink communication parameters provided in system information (if present). For other cases, the UE applies the NR sidelink communication parameters provided in SidelinkPreconfigNR (if present). When the UE performs a state transition between the above three cases, after obtaining the new configuration, the UE applies the NR sidelink communication parameters provided in the new state. Before obtaining the new configuration, the UE continues to apply the NR sidelink communication parameters provided in the old state.

[0295] Key issue #4 in 3GPP TR 23.752 describes support for inter-UE relay in the next release (i.e., Release 17 / 18), which means that relay can be used to support communication between two UEs in the case where the two UEs cannot communicate with each other directly. Presumably, the inter-UE relay needs to establish a PC5 unicast link with each of the source remote UE (i.e., the first PC5 hop) and the target remote UE (i.e., the second PC5 hop), so that the integrated PC5 unicast link between the source remote UE and the target remote UE can support related proximity-based services (ProSe) services, such as Fig.16 , which shows an integrated PC5 unicast link via inter-UE relay according to an exemplary embodiment.

[0296] 3GPP TS 38.836 Figure 5 .5.1-1 (reproduced as Fig.12 )and Figure 5 .5.1-2 (reproduced as Fig.13) describes the protocol stack of the user plane and control plane of the L2 inter-UE relay architecture, which includes an adaptation layer to support multiple source UEs to communicate with one target UE via the inter-UE relay and to support one source UE to communicate with multiple target UEs via the inter-UE relay. 3GPP TS38.836 further stipulates that the header of the adaptation layer PDU of the first and second PC5 hops includes the identity information of the (remote UE) end-to-end radio bearer. In addition, the identity information of the source remote UE and / or the identity information of the target remote UE is the candidate information to be included in the header of the adaptation layer PDU, which will be determined in the next work item (WI) stage.

[0297] Presumably, when transmitting an adaptation layer protocol data unit (PDU), the source UE may need to include information (e.g., a local ID of the target UE) in the header of the PDU to identify the target UE, so that the inter-UE relay can forward the SDU contained in the PDU to the target UE on the right link radio link control (RLC) bearer (or logical channel) of the second PC5 hop, because separate sidelink RLC bearers can be established for communication between the inter-UE relay and different target UEs. In addition to the identity information of the target UE, the ID of the end-to-end radio bearer included in the header by the source UE can also be used by the inter-UE relay to determine the sidelink RLC bearer.

[0298] The header may not need to include information identifying the source UE. On the other hand, the inter-UE relay may need to include information (e.g., the local ID of the source UE) to identify the source UE in the header of the adaptation layer PDU sent to the target UE, so that the target UE can deliver the service data unit (SDU) contained in the PDU to the right link PDCP entity, because a separate side link packet data convergence protocol (PDCP) entity is established in the target UE for different source UEs. The end-to-end radio bearer ID can also be included in the header of the adaptation layer PDU through the inter-UE relay. The header may not need to include information identifying the target UE. Fig.17 Examples illustrating the above concepts. Fig.17 Data / message forwarding via inter-UE relay according to an exemplary embodiment is described.

[0299] In order to satisfy the above concepts, a remote UE will need to know the local ID of another remote UE for the adaptation layer when communicating with another remote UE via an inter-UE relay, and the inter-UE relay needs to know the local IDs of the two remote UEs. It seems that the remote UE does not need to know its own local ID. In addition, each local ID of other remote UEs associated with the relevant remote UE may be unique within the scope of the relevant remote UE. It is also possible that each local ID of the remote UE may be unique within the scope of the inter-UE relay. Since the inter-UE relay needs to know the local IDs of the two paired remote UEs, a possible solution is that the inter-UE relay assigns or allocates a local ID to each remote UE, and then provides the local ID of one remote UE to the other remote UE. Alternatively, one remote UE can assign or allocate a local ID to another remote UE, and then provide it to the inter-UE relay. In this case, the inter-UE relay will need to maintain the associated local ID of each remote UE.

[0300] Basically, each remote UE may maintain a UE context of another remote UE communicating with it via an inter-UE relay to support relay operations. The UE context may include an upper layer ID (e.g., an application layer ID of the UE), a local ID, and an application / service ID. In other words, an association between an upper layer ID and a local ID is maintained in each remote UE to support relay operations. The inter-UE relay may also maintain a UE context for each remote UE. In addition to the upper layer ID (e.g., the application layer ID of the UE), the local ID, and the application / service ID, the UE context in the inter-UE relay may also include a layer 2 ID of the relevant remote UE. The upper layer ID of the UE may be the application layer ID of the UE, which is not a layer 2 ID.

[0301] For a possible solution, the inter-UE relay may assign or allocate a local ID for each remote UE, and then provide the local ID of one remote UE to the other remote UE during an integrated unicast link establishment procedure with two paired remote UEs. In one embodiment, the inter-UE relay may transmit the local ID to the remote UE in a direct communication request message or a direct communication accept message. More specifically, after receiving a direct communication request message from a source remote UE, the inter-UE relay may include the local ID of the source remote UE in another direct communication request message and transmit it to the target remote UE. Both direct communication request messages may also include an upper layer ID of the source remote UE (e.g., an application layer ID of the UE) and an upper layer ID of the target remote UE (e.g., an application layer ID of the UE).

[0302] And after receiving the direct communication accept message from the target remote UE, the inter-UE relay may include the local ID of the target remote UE in another direct communication accept message and transmit it to the source remote UE. Both direct communication accept messages may also include the upper layer ID of the target remote UE (e.g., the application layer ID of the UE). Considering that there may be multiple source remote UEs, the direct communication accept message from the target remote UE or both the direct communication accept message may also include the upper layer ID of the source remote UE. After the two remote UEs obtain the local ID of the other remote UE, data exchange on the user plane and message exchange on the control plane via the inter-UE relay may be initiated. Fig.18 Explain the above solution. Fig.18 Local ID allocation during an integrated unicast link establishment procedure according to an exemplary embodiment is described.

[0303] After the unicast link between the inter-UE relay and the remote UE has been established, the inter-UE relay may also provide the local ID of another remote UE to the remote UE. The local ID may be transmitted in a PC5-S message (e.g., a link identifier update request message, a link modification request message), a sidelink RRC message (e.g., an RRC reconfiguration sidelink message), or a sidelink MAC control element (to be specified). In addition to the local ID, the PC5-S message, the sidelink RRC message, or the sidelink MAC control element may also include an upper layer ID of another remote UE (e.g., an application layer ID of the UE) for associating the local ID with the upper layer ID of the other remote UE.

[0304] A first source remote UE (UE1) may want to connect to a target remote UE (UE2) via an inter-UE relay UE. The first source remote UE may initiate a first layer 2 link establishment procedure with the inter-UE relay UE for establishing a first PC5 unicast link (i.e., first PC5 hop) between the first source remote UE and the inter-UE relay UE. In response to the establishment of the first PC5 unicast link, the inter-UE relay UE may initiate a second layer 2 link establishment procedure with the target remote UE for establishing a second PC5 unicast link (i.e., second PC5 hop) between the inter-UE relay UE and the target remote UE. The first source remote UE and the target remote UE may then initiate a third layer 2 link establishment procedure via the inter-UE relay UE on the first PC5 unicast link and the second PC5 unicast link for establishing an end-to-end connection between the first source remote UE and the target remote UE.

[0305] After a first source remote UE (UE1) connects with a target remote UE (UE2) via an inter-UE relay, data (or traffic) from one remote UE may be forwarded by the inter-UE relay UE to another remote UE. It is possible that a second source remote UE (UE3) may want to connect with a target remote UE (UE2) via the same inter-UE relay UE. The second remote UE may initiate a fourth layer 2 link establishment procedure to the inter-UE relay for establishing a third PC5 unicast link (i.e., the first PC5 hop) between the second source remote UE and the inter-UE relay UE. If the inter-UE relay UE still follows the step flow for establishing a second PC5 unicast link to establish a fourth PC5 unicast link (i.e., the second PC5 hop) with the target remote UE, then this situation will reduce the use of the adaptation layer over a single PC5 unicast link in the first / second layer 2 link.

[0306] The benefit of routing adaptation layer PDUs / packets between the second source remote UE and the target remote UE is that the target remote UE can identify which source remote UE the side link packet belongs to based on the PC5 unicast link on which the side link packet is received, and each PC5 unicast link can be identified by a pair of source / destination L2IDs.

[0307] Therefore, instead of establishing a fourth PC5 unicast link with the target remote UE in order to relay the service of the second source remote UE, the inter-UE relay UE may only modify the second PC5 unicast link with the target remote UE. The inter-UE relay may initiate a layer 2 link modification procedure to the target remote UE in response to receiving a request to establish a third PC5 unicast link with the second source remote UE. The request to establish the third PC5 unicast link may be a direct communication request message or a link establishment request message. The inter-UE relay UE may send a link modification request message to the target remote UE in the layer 2 link modification procedure. After completing the above procedure, the second source remote UE may further initiate a fifth layer 2 link establishment procedure to the target remote UE via the inter-UE relay for establishing an end-to-end connection between the second source remote UE and the target remote UE.

[0308] In one embodiment, a link modification request message for initiating a layer 2 link modification procedure transmitted by an inter-UE relay UE to a target remote UE may include user information of the target remote UE (target user information). The link modification request message may also include user information of a second source remote UE (source user information), a relay service code (RSC) and / or (requested) quality of service (QoS) information (such as indicated in a request to establish a third PC5 unicast link or derived from the request). In response, the target remote UE may reply to the inter-UE relay UE with a link modification accept message. The link modification accept message may include user information of the target remote UE (source user information), user information of a second source remote UE (target user information), a relay service code (RSC) and / or (acceptable) QoS information.

[0309] The Relay Service Code (RSC) is a parameter that identifies the service requested by the second source remote UE (when initiating an end-to-end connection with the target remote UE). Fig.19 Explain the above solution. Fig.19 is a flow chart or message diagram illustrating joining a second source remote UE to a target remote UE via an inter-UE relay according to an exemplary embodiment.

[0310] It is also possible that the second target remote UE (UE3) may want to connect with the source remote UE (UE1) via the same inter-UE relay UE. The above solution is also applicable to this scenario.

[0311] Fig. 20 Flowchart 2000 is provided to illustrate an exemplary method for supporting inter-UE communication. In step 2005, a relay UE establishes a first layer 2 link with a first UE and a second layer 2 link with a second UE, wherein the first layer 2 link and the second layer 2 link are used to forward traffic between the first UE and the second UE. In step 2010, the relay UE receives a first PC5 message for requesting to establish a third layer 2 link from a third UE, wherein the first PC5 message includes second user information of the second UE. In step 2015, the relay UE transmits a second PC5 message for modifying the second layer 2 link to the second UE in response to receiving the first PC5 message from the third UE, wherein the second PC5 message includes third user information of the third UE and second user information of the second UE.

[0312] In one embodiment, the relay UE may receive a third PC5 message from the second UE for completing the modification of the second layer 2 link, wherein the third PC5 message includes the second user information of the second UE. The second PC5 message may be a link modification request message, and the third PC5 message may be a link modification acceptance message. The third PC5 message may further include the third user information, RSC and / or second QoS information of the third UE.

[0313] In one embodiment, the relay UE may transmit a fourth PC5 message for completing the establishment of the third layer 2 link to the third UE. The first PC5 message may be a direct communication request message or a link establishment request message, and the fourth PC5 message may be a direct communication acceptance message or a link establishment acceptance message. The first PC5 message may further include third user information of the third UE. The user information may be an upper layer ID or an application layer identity / identifier (ID). The second PC5 message may further include a relay service code (RSC) and / or first quality of service (QoS) information.

[0314] In one embodiment, the relay UE may assign a first local identity / identifier (ID) associated with the first UE for the first layer 2 link. The relay UE may send the first local ID to the second UE. The relay UE may assign a second local ID associated with the second UE for the second layer 2 link. The relay UE may send the second local ID to the first UE.

[0315] In one embodiment, the relay UE may allocate a third local identity / identifier (ID) associated with the third UE for the third layer 2 link. The relay UE may send the third local ID to the second UE. The relay UE may send the second local ID to the third UE.

[0316] Return to view Figure 3 and 4In an exemplary embodiment of a relay UE, the relay UE 300 includes a program code 312 stored in a memory 310. The CPU 308 can execute the program code 312 to enable the relay UE to perform the following operations: (i) establish a first layer 2 link with a first UE and establish a second layer 2 link with a second UE, wherein the first layer 2 link and the second layer 2 link are used to forward traffic between the first UE and the second UE; (ii) receive a first PC5 message for requesting to establish a third layer 2 link from a third UE, wherein the first PC5 message includes the second user information of the second UE; and (iii) transmit a second PC5 message for modifying the second layer 2 link to the second UE in response to receiving the first PC5 message from the third UE, wherein the second PC5 message includes the third user information of the third UE and the second user information of the second UE. In addition, the CPU 308 can execute the program code 312 to perform all the actions and steps described above or other actions and steps described herein.

[0317] Fig.21 Flowchart 2100 is provided to illustrate an exemplary method for supporting inter-UE communication. In step 2105, the relay UE establishes a first layer 2 link with the first UE and a second layer 2 link with the second UE, wherein the first layer 2 link and the second layer 2 link are used to forward traffic between the first UE and the second UE. In step 2110, the relay UE receives a first PC5-S message for requesting to establish a third layer 2 link from a third UE, wherein the first PC5-S message includes second user information of the second UE. In step 2115, the relay UE transmits a second PC5-S message for modifying the second layer 2 link to the second UE in response to receiving the first PC5-S message from the third UE, wherein the second PC5-S message includes third user information of the third UE.

[0318] In one embodiment, the relay UE may receive a third PC5-S message for completing the modification of the second layer 2 link from the second UE. The relay UE may transmit a fourth PC5-S message for completing the establishment of the third layer 2 link to the third UE.

[0319] In one embodiment, the first PC5-S message may be a direct communication request message or a link establishment request message. The first PC5-S message may further include third user information of the third UE. The user information may be an upper layer ID or an application layer identity / identifier (ID). The second PC5-S message may be a link modification request message. The third PC5-S message may be a link modification acceptance message. The fourth PC5-S message may be a direct communication acceptance message or a link establishment acceptance message.

[0320] In one embodiment, the first PC5-S message may include the third user information of the third UE, the user information of the relay UE, the relay service code (SC), the first security information and / or the first QoS information. The second PC5-S message may include the second user information of the second UE, the RSC and / or the first QoS information. The third PC5-S message may include the second user information of the second UE, the third user information of the third UE, the RSC and / or the second QoS information. The fourth PC5-S message may include the second user information of the second UE, the third user information of the third UE, the user information of the relay UE, the RSC, the second security information and / or the second QoS information.

[0321] In one embodiment, the second QoS information may be generated by the second UE at least according to the first QoS information. The first UE may be a first source remote UE. The second UE may be a target remote UE. The third UE may be a second source remote UE. The relay UE may be an inter-UE relay UE.

[0322] Return to view Figure 3 and 4 In an exemplary embodiment of a relay UE, the relay UE 300 includes a program code 312 stored in a memory 310. The CPU 308 can execute the program code 312 to enable the relay UE to perform the following operations: (i) establish a first layer 2 link with a first UE and establish a second layer 2 link with a second UE, wherein the first layer 2 link and the second layer 2 link are used to forward traffic between the first UE and the second UE; (ii) receive a first PC5-S message for requesting to establish a third layer 2 link from a third UE, wherein the first PC5-S message includes second user information of the second UE; and (iii) transmit a second PC5-S message for modifying the second layer 2 link to the second UE in response to receiving the first PC5-S message from the third UE, wherein the second PC5-S message includes third user information of the third UE. In addition, the CPU 308 can execute the program code 312 to perform all the actions and steps described above or other actions and steps described herein.

[0323] Various aspects of the present disclosure have been described above. It should be understood that the teachings herein can be implemented in a wide variety of forms, and any specific structure, function, or both disclosed herein are only representative. Based on the teachings herein, it should be understood by those skilled in the art that the aspects disclosed herein can be implemented independently of any other aspects, and two or more of these aspects can be combined in various ways. For example, any number of aspects set forth herein can be used to implement a device or practice method. In addition, other structures, functions, or structures and functions other than one or more aspects set forth herein or different from the aspects can be used to implement such a device or practice such a method. As an example of some of the above concepts, in some aspects, parallel channels can be established based on pulse repetition frequency. In some aspects, parallel channels can be established based on pulse position or offset. In some aspects, parallel channels can be established based on time hopping sequences. In some aspects, parallel channels can be established based on pulse repetition frequency, pulse position or offset, and time hopping sequences.

[0324] Those skilled in the art will appreciate that any of a variety of different technologies and techniques may be used to represent information and signals. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the above description may be represented by voltage, current, electromagnetic waves, magnetic fields or magnetic particles, optical fields or optical particles, or any combination thereof.

[0325] Those skilled in the art will further appreciate that the various illustrative logical blocks, modules, processors, components, circuits, and algorithm steps described in conjunction with the various aspects disclosed herein may be implemented as electronic hardware (e.g., a digital implementation, an analog implementation, or a combination of the two that may be designed using source decoding or some other technique), various forms of programs or design codes incorporating instructions (which, for convenience, may be referred to herein as "software" or "software modules"), or a combination of the two. 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 on the specific application and the design constraints imposed on the overall system. Those skilled in the art may implement the described functionality in different ways for each specific application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present disclosure.

[0326] In addition, the various illustrative logical blocks, modules, and circuits described in conjunction with the aspects disclosed herein may be implemented within or performed by an integrated circuit ("IC"), an access terminal, or an access point. An IC may include a general purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, electrical components, optical components, mechanical components, or any combination thereof designed to perform the functions described herein, and may execute code or instructions residing within the IC, outside the IC, or both. 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, for example, a combination of a DSP and a microprocessor, a combination of multiple microprocessors, one or more microprocessors in combination with a DSP core, or any other such configuration.

[0327] It should be understood that any specific order or hierarchy of steps in any disclosed process is an example of a sample method. It should be understood that based on design preferences, the specific order or hierarchy of steps in a process can be rearranged while remaining within the scope of the present disclosure. The accompanying method claims present elements of the various steps in a sample order, and it is not meant to be limited to the specific order or hierarchy shown.

[0328] The steps of the method or algorithm described in conjunction with the aspects disclosed herein can be implemented directly in hardware, in software modules executed by a processor, or in a combination of the two. Software modules (e.g., containing executable instructions and associated data) and other data can reside in a data memory, such as a RAM memory, a flash memory, a ROM memory, an EPROM memory, an EEPROM memory, a register, a hard disk, a removable disk, a CD-ROM, or any other form of computer-readable storage medium known in the art. Sample storage media can be coupled to a machine such as a computer / processor (for convenience, the machine can be referred to as a "processor" in this article) so that the processor can read information (e.g., code) from the storage medium and write information to the storage medium. Sample storage media can be integrated with the processor. The processor and storage medium can reside in an ASIC. The ASIC can reside in a user device. In an alternative, the processor and storage medium can reside in a user device as discrete components. In addition, in some aspects, any suitable computer program product can include a computer-readable medium, and the computer-readable medium includes a code related to one or more of the various aspects of the present disclosure. In some aspects, the computer program product can include packaging materials.

[0329] Although the present invention has been described in conjunction with various aspects, it will be appreciated that the present invention is capable of further modification. This application is intended to cover any changes, uses or adaptations of the present invention that generally follow the principles of the present invention and include such deviations from the present disclosure that are within the scope of known and customary practice in the technical field to which the present invention belongs.

Claims

1. A method for supporting relaying between user equipments, characterized in that: include: The relay user equipment establishes a first layer 2 link with the first user equipment and a second layer 2 link with the second user equipment, wherein the first layer 2 link and the second layer 2 link are used to forward the service between the first user equipment and the second user equipment; The relay user equipment receives a first PC5 message for requesting to establish a third layer 2 link from a third user equipment, wherein the first PC5 message includes second user information of the second user equipment; as well as The relay user equipment transmits a second PC5 message for modifying the second layer 2 link to the second user equipment in response to receiving the first PC5 message from the third user equipment, wherein the second PC5 message includes third user information of the third user equipment and the second user information of the second user equipment.

2. The method according to claim 1, characterized in that: Further including: The relay user equipment receives a third PC5 message for completing the modification of the second layer 2 link from the second user equipment, wherein the third PC5 message includes the second user information of the second user equipment.

3. The method according to claim 2, characterized in that The second PC5 message is a link modification request message, and the third PC5 message is a link modification accept message.

4. The method according to claim 2, characterized in that: The third PC5 message further includes the third user information of the third user equipment, a relay service code and / or second service quality information.

5. The method according to claim 1, characterized in that Further including: The relay user equipment transmits a fourth PC5 message for completing establishment of the third layer 2 link to the third user equipment.

6. The method according to claim 5, characterized in that The first PC5 message is a direct communication request message or a link establishment request message, and the fourth PC5 message is a direct communication acceptance message or a link establishment acceptance message.

7. The method according to claim 1, characterized in that The second PC5 message further includes a relay service code and / or first quality of service information.

8. The method according to claim 1, characterized in that: Further including: The relay user equipment assigns a first local identity / identifier associated with the first user equipment to the first layer 2 link; The relay user equipment sends the first local identity / identifier to the second user equipment; The relay user equipment assigns a second local identity / identifier associated with the second user equipment for the second layer 2 link; and The relay user equipment sends the second local identity / identifier to the first user equipment.

9. The method according to claim 8, characterized in that Further including: The relay user equipment assigns a third local identity / identifier associated with the third user equipment to the third layer 2 link; The relay user equipment sends the third local identity / identifier to the second user equipment; and The relay user equipment sends the second local identity / identifier to the third user equipment.

10. The method according to claim 1, characterized in that The first PC5 message further includes the third user information of the third user equipment, and / or the user information is an upper layer identity / identifier or an application layer identity / identifier.

11. A relay user equipment, characterized in that: include: Control circuit; a processor installed in the control circuit; as well as a memory installed in the control circuit and operatively coupled to the processor; wherein the processor is configured to execute program code stored in the memory to: Establishing a first layer 2 link with a first user equipment and establishing a second layer 2 link with a second user equipment, wherein the first layer 2 link and the second layer 2 link are used to forward traffic between the first user equipment and the second user equipment; receiving a first PC5 message for requesting to establish a third layer 2 link from a third user equipment, wherein the first PC5 message includes second user information of the second user equipment; as well as In response to receiving the first PC5 message from the third user equipment, a second PC5 message for modifying the second layer 2 link is transmitted to the second user equipment, wherein the second PC5 message includes third user information of the third user equipment and the second user information of the second user equipment.

12. The relay user equipment according to claim 11, characterized in that: The processor is further configured to execute program code stored in the memory to: A third PC5 message for completing the modification of the second layer 2 link is received from the second user equipment, wherein the third PC5 message includes the second user information of the second user equipment.

13. The relay user equipment according to claim 12, characterized in that: The second PC5 message is a link modification request message, and the third PC5 message is a link modification accept message.

14. The relay user equipment according to claim 12, characterized in that: The third PC5 message further includes the third user information of the third user equipment, a relay service code and / or second service quality information.

15. The relay user equipment according to claim 11, characterized in that: The processor is further configured to execute program code stored in the memory to: A fourth PC5 message for completing the establishment of the third layer 2 link is transmitted to the third user equipment.

16. The relay user equipment according to claim 15, characterized in that: The first PC5 message is a direct communication request message or a link establishment request message, and the fourth PC5 message is a direct communication acceptance message or a link establishment acceptance message.

17. The relay user equipment according to claim 11, characterized in that: The second PC5 message further includes a relay service code and / or first quality of service information.

18. The relay user equipment according to claim 11, characterized in that: The processor is further configured to execute program code stored in the memory to: assigning, to the first layer 2 link, a first local identity / identifier associated with the first user equipment; sending the first local identity / identifier to the second user equipment; assigning a second local identity / identifier associated with the second user equipment to the second layer 2 link; as well as The second local identity / identifier is sent to the first user equipment.

19. The relay user equipment according to claim 18, characterized in that: The processor is further configured to execute program code stored in the memory to: assigning a third local identity / identifier associated with the third user equipment to the third layer 2 link; sending the third local identity / identifier to the second user equipment; as well as The second local identity / identifier is sent to the third user equipment.

20. The relay user equipment according to claim 11, characterized in that: The first PC5 message further includes the third user information of the third user equipment, and / or the user information is an upper layer identity / identifier or an application layer identity / identifier.

Images