Method and apparatus for enhancing local identity allocation of user equipment for relay communication

Abstract

A method and apparatus for enhancing local identity allocation of user equipment for relay communication is disclosed. In one embodiment, a relay user equipment establishes a first inter-user equipment relay communication between a source user equipment and a first target user equipment and a second inter-user equipment relay communication between the source user equipment and a second target user equipment. The relay user equipment also sends a PC5 radio resource control message to the source user equipment, wherein the PC5 radio resource control message comprises list information indicating at least one of a first mapping of a first local user equipment identification and a first layer 2 identification for the first target user equipment and a second mapping of a second local user equipment identification and a second layer 2 identification for the second target user equipment.

Description

[0001] Cross - Reference to Related Applications

[0002] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 600,410, filed on November 17, 2023, the entire disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0003] The present disclosure generally relates to wireless communication networks, and more particularly to methods and devices for enhancing local ID allocation for multiple end UEs in a wireless communication system for UE - to - UE relay communication. Background Art

[0004] With the rapid growth in the demand for transferring large amounts of data to and from mobile communication devices, traditional mobile voice communication networks have evolved into networks that communicate using Internet Protocol (IP) data packets. This IP packet communication can provide IP - bearer voice, multimedia, multicast, and on - demand communication services to users of mobile communication devices.

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

[0006] A method and apparatus for relaying a User Equipment (UE) are disclosed. In one embodiment, a relay UE establishes a first User Equipment - to - User Equipment (U2U) relay communication between a source end UE and a first target end UE and a second U2U relay communication between the source end UE and a second target end UE. The relay UE also sends a PC5 Radio Resource Control (RRC) message to the source end UE, where the PC5 RRC message contains information indicating at least a first mapping of a first local UE identifier (ID) and a first layer 2 ID for the first target end UE and a second mapping of a second local UE ID and a second layer 2 ID for the second target end UE. Brief Description of the Drawings

[0007] Figure 1 The drawings illustrate a wireless communication system in accordance with one exemplary embodiment.

[0008] Figure 2It 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 It is a functional block diagram of a communication system according to an exemplary embodiment.

[0010] Figure 4 It is according to an exemplary embodiment of Figure 3 the functional block diagram of the program code.

[0011] Figure 5 It is a reproduction of 3GPP TS23.304 V18.2.0 Figure 4 .2.8 - 1.

[0012] Figure 6 It is a reproduction of 3GPP TS23.304 V18.2.0 Figure 6 .3.2.4.2 - 1.

[0013] Figure 7 It is a reproduction of 3GPP TS23.304 V18.2.0 Figure 6 .3.2.4.3 - 1.

[0014] Figure 8 It is a reproduction of 3GPP TS23.304 V18.2.0 Figure 6 .4.3.1 - 1.

[0015] Figure 9 It is a reproduction of 3GPP TS23.304 V18.2.0 Figure 6 .4.3.2 - 1.

[0016] Figure 10 It is a reproduction of 3GPP TS23.304 V18.2.0 Figure 6 .4.3.4 - 1.

[0017] Figure 11 It is a reproduction of 3GPP TS23.304 V18.2.0 Figure 6 .7.1.1 - 1.

[0018] Figure 12 It is a reproduction of 3GPP TS23.304 V18.2.0 Figure 6 .7.1.4 - 1.

[0019] Figure 13 It is a reproduction of 3GPP TS23.304 V18.2.0 Figure 6 .7.2 - 1.

[0020] Figure 14It is a reproduction of 3GPP TS23.304 V18.2.0 Figure 6 .7.3.2-1

[0021] Figure 15 It is a reproduction of 3GPP TS23.304 V18.2.0 Figure 6 .7.3.3-1

[0022] Figure 16 It is a reproduction of 3GPP TS24.554 V18.1.0 Figure 7 .2.2.2.1

[0023] Figure 17 It is a reproduction of 3GPP TS24.554 V18.1.0 Figure 7 .2.2.2.2

[0024] Figure 18 It is a reproduction of 3GPP TS24.554 V18.1.0 Figure 7 .2.3.2.1

[0025] Figure 19 It is a reproduction of 3GPP TS24.554 V18.1.0 Figure 7 .2.3.2.2

[0026] Figure 20 It is a reproduction of 3GPP R2-2312029 Figure 16 .12.x-1

[0027] Figure 21 It is a reproduction of 3GPP R2-2311934 Figure 16 .12.2.x-1

[0028] Figure 22 It is a reproduction of 3GPP R2-2311934 Figure 16 .12.2.x-2

[0029] Figure 23 It is a reproduction of 3GPP R2-2311934 Figure 5 .8.9.1.1-1

[0030] Figure 24 It is a reproduction of 3GPP R2-2311934 Figure 5 .8.9.1.1-2

[0031] Figure 25 Shows a message flow diagram according to an exemplary embodiment

[0032] Figure 26Shows a message flow diagram according to an exemplary embodiment.

[0033] Figure 27 Shows a message flow diagram according to an exemplary embodiment.

[0034] Figure 28 Shows a message flow diagram according to an exemplary embodiment.

[0035] Figure 29 Shows a message flow diagram according to an exemplary embodiment.

[0036] Figure 30 Is a flowchart according to an exemplary embodiment. Detailed implementation

[0037] The exemplary wireless communication systems and devices described below employ a wireless communication system that supports 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 (CDMA), Time Division Multiple Access (TDMA), Orthogonal Frequency Division Multiple Access (OFDMA), 3GPP Long Term Evolution (LTE) radio access, 3GPP Long Term Evolution Advanced (LTE-A), 3GPP2 Ultra Mobile Broadband (UMB), WiMax, 3GPP New Radio (NR), or some other modulation techniques.

[0038] Specifically, the exemplary wireless communication systems and devices described below can be designed to support one or more standards, such as those provided by the consortium named "3rd Generation Partnership Project" and referred to herein as 3GPP, including: TS23.304 V18.2.0, "Proximity-based Services (ProSe) in 5G Systems (5GS) (Release 18)"; TS24.554 V18.1.0, "Proximity-based Services (ProSe) in the protocol aspects of 5G Systems (5GS); Phase 3 (Release 18)"; R2-2312029, "Introduction to NR Sidelink Relay Enhancement" (Draft running CR 38.300), LG Electronics; and R2-2311934, "Introduction to NR Sidelink U2U Relay" (TS 38.331 running CR), vivo. The standards and documents listed above are hereby expressly incorporated by reference in their entirety.

[0039] Figure 1A multi - access wireless communication system according to an embodiment of the present invention is shown. The access network 100 (AN) includes multiple antenna groups, one including 104 and 106, another including 108 and 110, and still another including 112 and 114. In Figure 1 each, only two antennas are shown for each antenna group. However, more or fewer antennas can be utilized for each antenna group. The access terminal 116 (AT) communicates with antennas 112 and 114, where antennas 112 and 114 transmit information to the access terminal 116 via the forward link 120 and receive information from the access terminal 116 via the reverse link 118. The access terminal (AT) 122 communicates with antennas 106 and 108, where antennas 106 and 108 transmit information to the access terminal (AT) 122 via the forward link 126 and receive information from the access terminal (AT) 122 via the reverse link 124. In an FDD system, the communication links 118, 120, 124, and 126 can use different frequencies for communication. For example, the forward link 120 can use a frequency different from the frequency used by the reverse link 118.

[0040] Each group of antennas and / or the area in which they are designed to communicate is often referred to as a sector of the access network. In an embodiment, each antenna group is designed to communicate with access terminals in a sector of the area covered by the access network 100.

[0041] In the communication via the forward links 120 and 126, the transmitting antennas of the access network 100 can utilize beamforming to improve the signal - to - noise ratio of the forward links of different access terminals 116 and 122. Also, compared to an access network that transmits to all its access terminals via a single antenna, the access network that uses beamforming to transmit to access terminals randomly dispersed throughout the coverage area of the access network causes less interference to access terminals in adjacent cells.

[0042] The access network (AN) can be a fixed station or a base station for communicating with terminals and can also be referred to as an access point, Node B, base station, enhanced base station, evolved Node B (eNB), network node, network, or some other term. The access terminal (AT) can also be referred to as a user equipment (UE), wireless communication device, terminal, access terminal, or some other term.

[0043] Figure 2is 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 plurality of data streams is provided from a data source 212 to a transmit (TX) data processor 214.

[0044] In one embodiment, each data stream is transmitted via a respective transmit antenna. The TX data processor 214 formats, encodes, and interleaves the traffic data of the data streams based on a particular encoding scheme selected for each data stream to provide encoded data.

[0045] The encoded data of each data stream can 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 can be used at the receiver system to estimate the channel response. Subsequently, the multiplexed pilot and encoded data for the data stream is modulated (i.e., symbol mapped) based on a particular modulation scheme selected for each data stream (e.g., BPSK, QPSK, M-PSK, or M-QAM) to provide modulated symbols. Instructions executed by a processor 230 can determine the data rate, encoding, and modulation for each data stream.

[0046] Next, the modulated symbols of all data streams are provided to a TX MIMO processor 220, which can further process the modulated symbols (e.g., for OFDM). The TX MIMO processor 220 then provides N T modulated symbol streams to N T transmitters (TMTR) 222a through 222t. In some embodiments, the TX MIMO processor 220 applies beamforming weights to the symbols of the data streams and the antennas from which the symbols are transmitted.

[0047] Each transmitter 222 receives and processes the corresponding symbol stream to provide one or more analog signals, and further conditions (e.g., amplifies, filters, and upconverts) the analog signals to provide a modulated signal suitable for transmission via the MIMO channel. Then, N T modulated signals from transmitters 222a through 222t are transmitted from N T antennas 224a through 224t.

[0048] At the receiver system 250, by N RAntennas 252a through 252r receive the transmitted modulated signals and provide the signals received from each antenna 252 to corresponding receivers (RCVR) 254a through 254r. Each receiver 254 conditions (e.g., filters, amplifies, and down-converts) the corresponding received signal, digitizes the conditioned signal to provide samples, and further processes the samples to provide a corresponding "received" symbol stream.

[0049] RX data processor 260 then receives and processes N R received symbol streams from N R receivers 254 based on specific receiver processing techniques to provide N T "detected" symbol streams. RX data processor 260 then demodulates, deinterleaves, and decodes each detected symbol stream to recover the traffic data for the data stream. The processing performed by RX data processor 260 is complementary to the processing performed by TX MIMO processor 220 and TX data processor 214 at transmitter system 210.

[0050] Processor 270 periodically determines which precoding matrix (discussed below) to use. Processor 270 formulates a reverse link message that includes a matrix index portion and a rank value portion.

[0051] The reverse link message can include various types of information about the communication link and / or the received data streams. The reverse link message is then processed by TX data processor 238 (which also receives traffic data for several data streams from data source 236), modulated by modulator 280, conditioned by transmitters 254a through 254r, and transmitted back to transmitter system 210.

[0052] At transmitter system 210, the modulated signals from receiver system 250 are received by antenna 224, conditioned by receiver 222, demodulated by demodulator 240, and processed by RX data processor 242 to extract the reverse link message transmitted by receiver system 250. Processor 230 then determines which precoding matrix to use to determine the beamforming weights and then processes the extracted message.

[0053] Turning to Figure 3 , this figure shows an alternative simplified functional block diagram of a communication device according to an embodiment of the present invention. As Figure 3 shown, communication device 300 in a wireless communication system can be utilized to implement Figure 1 UEs (or ATs) 116 and 122 in Figure 1a base station (or AN) 100 in, and 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, 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 signals input by a user through the input device 302 (e.g., a keyboard or keypad), and may output images and sounds through the output device 304 (e.g., a monitor or speaker). The transceiver 314 is used to receive and transmit wireless signals, transfer the received signals to the control circuit 306, and wirelessly output the signals generated by the control circuit 306. The AN 100 in Figure 1 may also be implemented by using the communication device 300 in the wireless communication system.

[0054] Figure 4 is a simplified block diagram of the program code 312 shown in Figure 3 according to an embodiment of the present invention. In this embodiment, the program code 312 includes an application layer 400, a layer 3 part 402, and a layer 2 part 404, and is coupled to a layer 1 part 406. The layer 3 part 402 generally performs radio resource control. The layer 2 part 404 generally performs link control. The layer 1 part 406 generally performs physical connection.

[0055] 3GPP TS23.304 describes the following:

[0056] 4.2.8 5G ProSe UE - to - UE Relay Reference Architecture

[0057] Figure 4 .2.8 - 1 shows the layer 2 and layer 3 5G ProSe UE - to - UE relay reference architecture. 5G ProSe end UEs communicate with each other via a 5G ProSe UE - to - UE relay.

[0058] [[The ".2.8 - 1" titled "Reference Architecture for 5G ProSe UE - to - UE Relay" in 3GPP TS23.304 V18.2.0 is reproduced as Figure 4 .2.8 - 1 Figure 5

[0059] Each 5G ProSe end UE and 5G ProSe UE - to - UE relay may have subscriptions from the same PLMN or different PLMNs.

[0060] […]

[0061] ​5.8.4 Identifiers for 5G ProSe UE - to - UE Relay Discovery

[0062] 5.8.4.1 Overview

[0063] The 5G ProSe UE - to - UE relay discovery message contains two sets of identifiers, namely the direct discovery set and the UE - to - UE relay discovery set.

[0064] - The direct discovery identifier set is part of the content of the 5G ProSe direct discovery message, as defined in Clause 5.8.1.

[0065] - The UE - to - UE relay discovery identifier set contains information that supports the discovery of 5G ProSe UE - to - UE relay and the extension of direct discovery.

[0066] The 5G ProSe UE - to - UE relay shall modify the UE - to - UE relay discovery identifier set and forward the direct discovery identifier set and the UE - to - UE relay discovery identifier set during the discovery procedure.

[0067] 5.8.4.2 Common Identifiers for 5G ProSe UE - to - UE Relay Discovery

[0068] The following parameters are used for the 5G ProSe UE - to - UE relay discovery notification message (Model A), where the source layer 2 ID and the destination layer 2 ID are used for sending and receiving messages, and the user information ID and the relay service code are included in the message:

[0069] - Source layer 2 ID: The 5G ProSe UE - to - UE relay selects its own source layer 2 ID for the 5G ProSe UE - to - UE relay discovery notification message.

[0070] - Destination layer 2 ID: The destination layer 2 ID for the 5G ProSe UE - to - UE relay discovery notification message is selected based on the configuration as described in Clause 5.1.5.1.

[0071] - User information ID of the 5G ProSe UE - to - UE relay: Provides information about the 5G ProSe UE - to - UE relay.

[0072] - List of user information IDs of the 5G ProSe end - UE: Provides information about the 5G ProSe end - UE.

[0073] - Relay service code: Information used to indicate the connectivity service provided by the 5G ProSe UE - to - UE relay for the 5G ProSe end - UE.

[0074] The following parameters are for the 5G ProSe UE - to - UE relay discovery request message (Model B) between the discoverer 5G ProSe - side UE and the 5G ProSe UE - to - UE relay. The source layer 2 ID and the destination layer 2 ID are used for sending and receiving messages, and the user information ID and the relay service code are included in the message:

[0075] - Source layer 2 ID: The discoverer 5G ProSe - side UE itself selects the source layer 2 ID for the 5G ProSe UE - to - UE relay discovery request message.

[0076] - Destination layer 2 ID: Based on the configuration described in Clause 5.1.5.1, select the destination layer 2 ID for the 5G ProSe UE - to - UE relay discovery request message.

[0077] - User information ID of the discoverer 5G ProSe - side UE: Provides information about the discoverer 5G ProSe - side UE.

[0078] - User information ID of the discovered 5G ProSe - side UE: Provides information about the discovered 5G ProSe - side UE.

[0079] - Relay service code: Information about the connectivity service that the discoverer 5G ProSe - side UE is interested in.

[0080] The following parameters are for the 5G ProSe UE - to - UE relay discovery response message (Model B) between the discoverer 5G ProSe - side UE and the 5G ProSe UE - to - UE relay. The source layer 2 ID and the destination layer 2 ID are used for sending and receiving messages, and the user information ID and the relay service code are included in the message:

[0081] - Source layer 2 ID: The 5G ProSe UE - to - UE relay itself selects the source layer 2 ID for the 5G ProSe UE - to - UE relay discovery response message.

[0082] - Destination layer 2 ID: Set to the source layer 2 ID of the received 5G ProSe UE - to - UE relay discovery request message.

[0083] - User information ID of the discovered 5G ProSe - side UE: Provides information about the discovered 5G ProSe - side UE.

[0084] - User information ID of the 5G ProSe UE - to - UE relay: Provides information about the 5G ProSe UE - to - UE relay.

[0085] - Relay service code: Identifies the connectivity service provided by the 5G ProSe UE - to - UE relay to the 5G ProSe UE - end UE, which matches the relay service code from the corresponding discovery request message.

[0086] The following parameters are used for the 5G ProSe UE - to - UE relay discovery request message (Model B) between the 5G ProSe UE - to - UE relay and the discovered 5G ProSe UE - end UE, where the source layer 2 ID and the destination layer 2 ID are used to send and receive messages, and the user information ID and the relay service code are included in the message:

[0087] - Source layer 2 ID: The 5G ProSe UE - to - UE relay selects its own source layer 2 ID for the 5G ProSe UE - to - UE relay discovery request message.

[0088] - Destination layer 2 ID: The destination layer 2 ID for the 5G ProSe UE - to - UE relay discovery request message is selected based on the configuration described in Clause 5.1.5.1.

[0089] - User information ID of the discovered 5G ProSe UE - end UE: Provides information about the discovered 5G ProSe UE - end UE.

[0090] - User information ID of the discoverer 5G ProSe UE - end UE: Provides information about the discoverer 5G ProSe UE - end UE.

[0091] - User information ID of the 5G ProSe UE - to - UE relay: Provides information about the 5G ProSe UE - to - UE relay.

[0092] - Relay service code: Identifies the connectivity service provided by the 5G ProSe UE - to - UE relay to the 5G ProSe UE - end UE.

[0093] The following parameters are used for the 5G ProSe UE - to - UE relay discovery response message (Model B) between the 5G ProSe UE - to - UE relay and the discovered 5G ProSe UE - end UE, where the source layer 2 ID and the destination layer 2 ID are used to send and receive messages, and the user information ID and the relay service code are included in the message:

[0094] - Source layer 2 ID: The discovered 5G ProSe UE - end UE selects its own source layer 2 ID for the 5G ProSe UE - to - UE relay discovery response message.

[0095] - Destination layer 2 ID: Is set to the source layer 2 ID of the received 5G ProSe UE - to - UE relay discovery request message.

[0096] - User Information ID of the discovered 5G ProSe UE: Provides information about the discovered 5G ProSe UE.

[0097] - User Information ID of the discoverer 5G ProSe UE: Provides information about the discoverer 5G ProSe UE.

[0098] - Relay service code: Identifies the connectivity service provided by the 5G ProSe UE - to - UE relay to the 5G ProSe UE, which matches the relay service code from the corresponding discovery request message.

[0099] Note: The UE implementation needs to ensure that when the UE selects its own source layer 2 ID, the source layer 2 ID it selects is different between the 5G ProSe direct discovery in Clause 6.3.2 (including 5G ProSe UE - to - network relay discovery and 5G ProSe UE - to - UE relay discovery) and the 5G ProSe direct communication in Clauses 6.4, 6.5, and 6.7 (including 5G ProSe UE - to - network relay communication and 5G ProSe UE - to - UE relay communication), and is different from any other provided destination layer 2 ID described in Clause 5.1 and any other self - selected source layer 2 ID for simultaneous 5G ProSe direct discovery with different discovery models (including 5G ProSe UE - to - network relay discovery and 5G ProSe UE - to - UE relay discovery).

[0100] 5.8.5 Identifiers for 5G ProSe UE - to - UE Relay Communication with Discovery Integrated

[0101] For the broadcast direct communication request message on the first - hop PC5 reference point, the source layer 2 ID is self - selected by the source 5G ProSe UE, and the destination layer 2 ID is selected based on the configuration described in Clause 5.1.

[0102] For the broadcast direct communication request message on the second - hop PC5 reference point, the source layer 2 ID is self - selected by the 5G ProSe UE - to - UE relay, and the destination layer 2 ID is selected based on the configuration described in Clause 5.1.

[0103] The 5G ProSe UE - to - UE relay can send a unicast direct communication request message to the target 5G ProSe UE by setting the destination layer 2 ID, where the received unicast destination layer 2 ID of the target 5G ProSe UE is specified in Clause 6.4.3.7. The source layer 2 ID is self - selected by the 5G ProSe UE - to - UE relay.

[0104] For unicast direct communication receive messages, the source layer 2 ID is selected by the target 5G ProSe UE or the 5G ProSe UE - to - UE relay itself.

[0105] […]

[0106] 6.3.2.4 5G ProSe UE - to - UE Relay Discovery

[0107] 6.3.2.4.1 General Overview

[0108] 5G ProSe UE - to - UE relay discovery is suitable for both 5G ProSe layer 3 and layer 2 UE - to - UE relay discovery for public safety purposes and commercial services. To perform 5G ProSe UE - to - UE relay discovery, the 5G ProSe UE and the 5G ProSe UE - to - UE relay are pre - configured or provisioned with the relevant information described in clause 5.1.

[0109] The Relay Service Code (RSC) is used for 5G ProSe UE - to - UE relay discovery to indicate the connectivity service provided by the 5G ProSe UE - to - UE relay to the 5G ProSe UE. The RSC is pre - configured or pre - provisioned on the 5G ProSe UE - to - UE relay and the 5G ProSe UE, as defined in clause 5.1. The 5G ProSe UE - to - UE relay and the 5G ProSe UE know whether the RSC provides a 5G ProSe layer 2 or layer 3 UE - to - UE relay service based on the policy specified in clause 5.1. A 5G ProSe UE - to - UE relay supporting multiple RSCs may use multiple discovery messages to advertise the RSCs, one RSC per discovery message.

[0110] 6.3.2.4.2 Procedures for 5G ProSe UE - to - UE Relay Discovery Using Model A

[0111] Figure 6 .3.2.4.2 - 1 depicts the procedures for 5G ProSe UE - to - UE discovery using Model A.

[0112] [The section in 3GPP TS23.304 V18.2.0 titled "5G ProSe UE - to - UE Relay Discovery Using Model A" Figure 6 .3.2.4.2 - 1 is reproduced as Figure 6

[0113] 1. The 5G ProSe UE - to - UE relay has discovered other neighboring UEs (e.g., via a previous 5G ProSe UE - to - UE relay discovery or 5G ProSe UE - to - UE relay communication procedures). The 5G ProSe UE - to - UE relay obtains the user information ID of the other neighboring UEs for each RSC.

[0114] ​The 2.5G ProSe UE - to - UE relay sends a UE - to - UE relay discovery notification message. The UE - to - UE relay discovery notification message contains the type of the discovery message, the user information ID of the 5G ProSe UE - to - UE relay, the RSC, and a list of user information IDs of the 5G ProSe UE at the source side, and is sent using the source layer 2 ID and the destination layer 2 ID, as described in clause 5.8.4.

[0115] The 5G ProSe UE - to - UE relay will only notify the user information IDs of other neighboring UEs that provided relay_indication when they were previously discovered.

[0116] The 5G ProSe UE at the source side listens for the notification message from the 5G ProSe UE - to - UE relay. The 5G ProSe UE at the source side determines the destination layer 2 ID for signaling reception, as specified in clause 5.1.

[0117] 6.3.2.4.3 Procedures for 5G ProSe UE - to - UE Relay Discovery Using Model B

[0118] Figure 6 The procedures for 5G ProSe UE - to - UE relay discovery using Model B are depicted in.3.2.4.3 - 1.

[0119] [In 3GPP TS23.304 V18.2.0, the section titled "5G ProSe UE - to - UE Relay Discovery Using Model B" Figure 6 .3.2.4.3 - 1 is reproduced as Figure 7

[0120] 1. The discoverer 5G ProSe UE at the source side (UE - 1) sends a 5G ProSe UE - to - UE relay discovery request message. The 5G ProSe UE - to - UE relay discovery request message contains the type of the discovery message, its own user information ID, the RSC, and the user information ID of the discovered 5G ProSe UE at the source side (UE - 2), and is sent using the source layer 2 ID and the destination layer 2 ID, as described in clause 5.8.4.

[0121] The 5G ProSe UE - to - UE relay determines the destination layer 2 ID for signaling reception, as specified in clause 5.1.

[0122] ​2. The 5G ProSe UE - to - UE relay that matches the RSC sends a 5G ProSe UE - to - UE relay discovery request message. The 5G ProSe UE - to - UE relay discovery request message contains the type of the discovery message, the user information ID of the discovering 5G ProSe UE at the source (UE - 1), the user information ID of the UE - to - UE relay, the RSC, and the user information ID of the discovered 5G ProSe UE at the destination (UE - 2), and is sent using the source layer 2 ID and the destination layer 2 ID, as described in Clause 5.8.4.

[0123] The 5G ProSe UE at the destination determines the destination layer 2 ID for signaling reception, as specified in Clause 5.1.

[0124] 3. The discovered 5G ProSe UE at the destination (UE2) that matches the value of the RSC and the user information ID of the discovered 5G ProSe UE at the destination (UE2) respond to the 5G ProSe UE - to - UE relay with a 5G ProSe UE - to - UE relay discovery response message. The 5G ProSe UE - to - UE relay discovery response message contains the type of the discovery message, the RSC, the user information ID of the discovering 5G ProSe UE at the source (UE - 1), and its own user information ID, and is sent using the source layer 2 ID and the destination layer 2 ID, as described in Clause 5.8.4. If the discovered 5G ProSe UE at the destination (UE - 2) receives multiple UE - to - UE relay discovery request messages from different 5G ProSe UE - to - UE relays, then it can choose to respond or not respond to the 5G ProSe UE - to - UE relay (e.g., based on the PC5 signal strength of each received message).

[0125] 4. The 5G ProSe UE - to - UE relay sends a 5G ProSe UE - to - UE relay discovery response message. The 5G ProSe UE - to - UE relay discovery response message contains the type of the discovery message, the user information ID of the UE - to - UE relay, the RSC, and the user information ID of the discovered 5G ProSe UE at the destination (UE - 2), and is sent using the source layer 2 ID and the destination layer 2 ID, as described in Clause 5.8.4.

[0126] 6.3.2.4.4 Candidate 5G ProSe UE - to - UE Relay Discovery

[0127] When the discovering UE at the source discovers a candidate 5G ProSe UE - to - UE relay, this procedure for candidate 5G ProSe UE - to - UE relay discovery supports negotiated relay reselection, as described in Clause 6.7.4.

[0128] Use the procedure for 5G ProSe UE - to - UE relay discovery with Model B (see Clause 6.3.2.4.3), with the following differences:

[0129] - Step 1: In the 5G ProSe UE - to - UE relay discovery request message, the RSC is not included, and the user information ID of the discovered 5G ProSe UE is replaced with the user information ID of the candidate 5G ProSe UE - to - UE relay. If the 5G ProSe UE receives the layer 2 ID of the candidate 5G ProSe UE - to - UE relay in the link modification request message, then it can set the layer 2 ID of the candidate 5G ProSe UE - to - UE relay as the destination layer 2 ID.

[0130] - Steps 2 and 3 are skipped because the RSC does not exist in the received 5G ProSe UE - to - UE relay discovery request message.

[0131] - Step 4: If the 5G ProSe UE - to - UE relay matches the user information ID of the candidate 5G ProSe UE - to - UE relay received in the 5G ProSe UE - to - UE relay discovery request, then it sends a 5G ProSe UE - to - UE relay discovery response and does not include the user information ID of the discovered 5G ProSe UE.

[0132] […]

[0133] 6.4.3 Unicast Mode 5G ProSe Direct Communication

[0134] 6.4.3.1 Layer 2 Link Establishment via the PC5 Reference Point

[0135] To perform the unicast mode of ProSe direct communication over the PC5 reference point, the UE is configured with the relevant information as described in Clause 5.1.3.

[0136] Figure 6 .4.3.1 - 1 shows the layer 2 link establishment procedure for unicast mode ProSe direct communication via the PC5 reference point.

[0137] [The one named "Layer 2 Link Establishment Procedure" in 3GPP TS23.304 V18.2.0 Figure 6 .4.3.1 - 1 is reproduced as Figure 8

[0138] 1. As specified in Clause 5.8.2.4, the UE determines the destination layer 2 ID for signaling reception for PC5 unicast link establishment.

[0139] 2. The ProSe application layer in UE - 1 provides application information for PC5 unicast communication. The application information includes ProSe service information, the application layer ID of the UE. The application layer ID of the target UE may be included in the application information.

[0140] ​The ProSe application layer in UE-1 may provide the ProSe application requirements for this unicast communication. As specified in clause 5.6.1, UE-1 determines the PC5 QoS parameters and PFI.

[0141] If UE-1 decides to reuse an existing PC5 unicast link as specified in clause 5.3.4, then UE triggers the layer 2 link modification procedure as specified in clause 6.4.3.4.

[0142] 3. UE-1 sends a direct communication request message to initiate the unicast layer 2 link establishment procedure. The direct communication request message contains:

[0143] - Source user information: The application layer ID of the initiating UE (i.e., the application layer ID of UE-1).

[0144] - If the ProSe application layer provides the application layer ID of the target UE in step 2, then it contains the following information:

[0145] - Target user information: The application layer ID of the target UE (i.e., the application layer ID of UE-2).

[0146] - ProSe service information: Information about the ProSe identifier for which the layer 2 link establishment is requested.

[0147] - Security information: Information for establishing security.

[0148] Note 1: The security information and the necessary protection for the source user information and target user information are defined in TS 33.503

[29] .

[0149] As specified in clauses 5.8.2.1 and 5.8.2.4, the source layer 2 ID and the destination layer 2 ID for sending the direct communication request message are determined. The destination layer 2 ID can be a broadcast or unicast layer 2 ID. When using the unicast layer 2 ID, the target user information shall be included in the direct communication request message.

[0150] UE-1 sends the direct communication request message via PC5 broadcast or unicast using the source layer 2 ID and the destination layer 2 ID.

[0151] The default PC5 DRX configuration can be used for the transmission and reception of this message (see TS 38.300

[12] ).

[0152] 4. The security of UE-1 is established as follows:

[0153] 4a. If the target user information is included in the direct communication request message, then the target UE (i.e., UE-2) responds by establishing security with UE-1.

[0154] 4b. If the target user information is not included in the direct communication request message, then the UEs interested in using the notified ProSe service over the PC5 unicast link with UE-1 respond by establishing security with UE-1.

[0155] Note 2: The signaling for the security procedures is defined in TS 33.503

[29] .

[0156] When security protection is enabled, UE-1 sends the following information to the target UE:

[0157] - If IP communication is used, then:

[0158] - IP address configuration: For IP communication, this link requires IP address configuration and it indicates one of the following values:

[0159] - "DHCPv4 server", if only the IPv4 address allocation mechanism is supported by the initiating UE, i.e., acting as a DHCPv4 server; or

[0160] - "IPv6 router", if the initiating UE only supports the IPv6 address allocation mechanism, i.e., acting as an IPv6 router; or

[0161] - "DHCPv4 server and IPv6 router", if both the IPv4 and IPv6 address allocation mechanisms are supported by the initiating UE; or

[0162] - "Address allocation not supported", if neither the IPv4 nor the IPv6 address allocation mechanism is supported by the initiating UE.

[0163] - Link-local IPv6 address: If UE-1 does not support the IPv6 IP address allocation mechanism, i.e., the IP address configuration indicates "Address allocation not supported", then a link-local IPv6 address is formed locally based on RFC 4862

[17] .

[0164] - QoS information: Information about the PC5 QoS flow. For each PC5 QoS flow, the PFI and the corresponding PC5 QoS parameters (i.e., PQI and optionally other parameters such as MFBR / GFBR, etc.) and optionally the associated ProSe identifier.

[0165] - Optional PC5 QoS rules.

[0166] The source layer 2 ID for the security establishment procedure is determined as specified in clauses 5.8.2.1 and 5.8.2.4. The destination layer 2 ID is set to the source layer 2 ID of the received direct communication request message.

[0167] Once the security establishment procedure message is received, UE-1 obtains the layer 2 ID of the peer UE for signaling and data traffic for this unicast link for future communication.

[0168] 5. One or more target UEs that have successfully established security with UE-1 send a direct communication acceptance message to UE-1:

[0169] 5a. (UE-oriented layer 2 link establishment) If the direct communication request message contains target user information, then, in the case where the application layer ID of UE-2 matches, the target UE (i.e., UE-2) responds with a direct communication acceptance message.

[0170] 5b. (ProSe service-oriented layer 2 link establishment) If the direct communication request message does not contain target user information, then the UEs (UE-2 and UE-4 in Figure 6 .4.3.1-1) interested in the ProSe service notified respond to the request by sending a direct communication acceptance message.

[0171] The direct communication acceptance message contains:

[0172] - Source user information: The application layer ID of the UE that sends the direct communication acceptance message.

[0173] - QoS information: Information about the PC5 QoS flow. For each PC5 QoS flow, the PFI and the corresponding PC5 QoS parameters requested by UE-1 (i.e., PQI and optionally other parameters such as MFBR / GFBR, etc.) and optionally the associated ProSe identifier.

[0174] - Optional PC5 QoS rules.

[0175] - If IP communication is used, then:

[0176] - IP address configuration: For IP communication, this link requires IP address configuration, and it indicates one of the following values:

[0177] - "DHCPv4 server", if only the IPv4 address allocation mechanism is supported by the target UE, i.e., acting as a DHCPv4 server; or

[0178] - "IPv6 router", if the target UE only supports the IPv6 address allocation mechanism, i.e., acting as an IPv6 router; or

[0179] - "DHCPv4 server and IPv6 router", if both the IPv4 and IPv6 address allocation mechanisms are supported by the target UE; or

[0180] - "Address allocation not supported", if neither the IPv4 nor the IPv6 address allocation mechanism is supported by the target UE.

[0181] - Link-local IPv6 address: A link-local IPv6 address formed locally based on RFC 4862

[17] , if the target UE does not support the IPv6 IP address allocation mechanism, i.e., the IP address configuration indicates "address allocation not supported", and UE-1 includes the link-local IPv6 address in the direct communication request message. The target UE shall include a non-conflicting link-local IPv6 address.

[0182] If two UEs (i.e., the initiating UE and the target UE) are selected to use the link-local IPv6 address, then these two UEs will deactivate the duplicate address detection defined in RFC 4862

[17] .

[0183] Note 3: When the initiating UE or the target UE indicates support for an IPv6 router, the corresponding address configuration procedure will be implemented after establishing the layer 2 link and the link-local IPv6 address will be ignored.

[0184] The ProSe layer of the UE that establishes the PC5 unicast link will assign the PC5 link identifier for the unicast link and the PC5 unicast link-related information and pass it down to the AS layer. The information related to the PC5 unicast link includes layer 2 ID information (i.e., the source layer 2 ID and the destination layer 2 ID). This enables the AS layer to maintain the PC5 link identifier and the PC5 unicast link-related information.

[0185] Two UEs can negotiate the PC5 DRX configuration in the AS layer, and the PC5 DRX parameter values can be configured for each pair of source and destination layer 2 IDs in the AS layer.

[0186] 6. Transmit ProSe data over the established unicast link as follows:

[0187] The PC5 link identifier and the PFI are provided to the AS layer together with the ProSe data.

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

[0189] Note 4: The UE implementation scheme provides the layer 2 ID information to the AS layer.

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

[0191] Note 5: The PC5 unicast link is bidirectional. Therefore, the peer UE of UE-1 can send ProSe data to UE-1 via the unicast link with UE-1.

[0192] […]

[0193] 6.4.3.2 Link Identifier Update for Unicast Links

[0194] Figure 6 .4.3.2-1 shows the link identifier update procedure for unicast links. When privacy requirements are configured for the ProSe identifier associated with a unicast link, the identifiers (e.g., application layer ID, source layer 2 ID, and IP address / prefix) for the unicast mode of 5G ProSe communication via the PC5 reference point shall change over time as specified in clauses 5.8.2.1 and 5.8.2.4. For other reasons, e.g., application layer requirements, the UE may decide to change the identifier. This procedure is used to update and exchange the new identifier between the source and peer UEs for the unicast link and then use the new identifier, thus preventing service interruption. When there are privacy requirements as pointed out above, this procedure is performed over the security-protected unicast link.

[0195] If the UE has multiple unicast links using the same application layer ID or layer 2 ID, then the UE needs to perform the link identifier update procedure over each of the unicast links.

[0196] [The [Link Identifier Update Procedure] in 3GPP TS23.304 V18.2.0 Figure 6 .4.3.2-1 is reproduced as Figure 9

[0197] 0. UE-1 and UE-2 have a unicast link established as described in clause 6.4.3.1.

[0198] 1. For example, due to a change in the application layer ID or when a timer expires, UE-1 decides to change its identifier. UE-1 generates its new layer 2 ID using the old identifier and sends a link identifier update request message to UE-2.

[0199] The link identifier update request message contains the new identifier to be used (including the new layer 2 ID, security information, optional new application layer ID, and optional new IP address / prefix (if IP communication is used)). If security is configured for the unicast link, the new identifier will be encrypted to protect privacy. After sending the link identifier update request message, if UE-1 has data to send, then UE-1 continues to send data traffic to UE-2 using the old identifier until UE-1 sends a link identifier update confirmation message to UE-2.

[0200] ​Note 1: The timer runs for each source layer 2 ID.

[0201] Note 2: When one of the two UEs acts as an IPv6 router as described in Clause 5.5.1.1 and the IP address / prefix also needs to be changed, the corresponding address configuration procedure will be carried out after the link identifier update procedure.

[0202] 2. After receiving the link identifier update request message, UE-2 changes its identifier. UE-2 responds with a link identifier update response message that contains the new identifier to be used (including the new layer 2 ID, security information, optionally including the new application layer ID, and optionally including the new IP address / prefix in the case of using IP communication). If security is configured for the unicast link, the new identifier should be encrypted to protect privacy. The link identifier update response message is sent using the old identifier. UE-2 continues to receive traffic from UE-1 with the old layer 2 ID until UE-2 receives traffic from UE-1 with the new layer 2 ID. After sending the link identifier update response message, if UE-2 has data to send, UE-2 continues to send data traffic to UE-1 with the old identifier until UE-2 receives a link identifier update confirmation message from UE-1.

[0203] 3. After receiving the link identifier update response message, UE-1 responds with a link identifier update confirmation message. The link identifier update confirmation message contains the new identifier received from UE-2 in the link identifier update response message. The link identifier update confirmation message is sent using the old identifier. UE-1 continues to receive traffic from UE-2 with the old layer 2 ID until UE-1 receives traffic from UE-2 with the new layer 2 ID.

[0204] 4. The ProSe layer of UE-1 passes the PC5 link identifier and the updated layer 2 ID for the unicast link (i.e., the new layer 2 ID of UE-1 for the source and the new layer 2 ID of UE-2 for the destination) down to the AS layer. This enables the AS layer to update the provided layer 2 ID for the unicast link.

[0205] For this unicast link, UE-1 starts using its new identifier and the new identifier of UE-2.

[0206] 5. After receiving the link identifier update confirmation message, the ProSe layer of UE-2 passes the PC5 link identifier and the updated layer 2 ID for the unicast link (i.e., the new layer 2 ID of UE-2 for the source and the new layer 2 ID of UE-1 for the destination) down to the AS layer. This enables the AS layer to update the provided layer 2 ID for the unicast link.

[0207] For this unicast link, UE-2 starts using its new identifier and the new identifier of UE-1.

[0208] Note 3: The security information in the above messages also needs to be updated simultaneously with the Layer 2 ID. This is defined in TS 33.503

[29] .

[0209] […]

[0210] 6.4.3.4 Layer 2 Link Modification for Unicast Link

[0211] Figure 6 .4.3.4-1 shows the Layer 2 link modification procedure for unicast link. This procedure is used to:

[0212] - Add a new PC5 QoS flow to an existing PC5 unicast link.

[0213] - This covers the cases of adding a new PC5 QoS flow to an existing ProSe service and adding a new PC5 QoS flow to a new ProSe service.

[0214] - Modify an existing PC5 QoS flow in an existing PC5 unicast link.

[0215] - This covers the cases of modifying the PC5 QoS parameters for an existing PC5 QoS flow.

[0216] - This also covers the cases of removing the associated ProSe service from an existing PC5 QoS flow and associating a new ProSe service with an existing PC5 QoS flow.

[0217] - Remove an existing PC5 QoS flow from an existing PC5 unicast link.

[0218] [The [["Layer 2 Link Modification Procedure"]] in 3GPP TS 23.304 V18.2.0 Figure 6 .4.3.4-1 is reproduced as Figure 10

[0219] 0. UE-1 and UE-2 have a unicast link established as described in Clause 6.4.3.1.

[0220] 1. The ProSe application layer in UE-1 provides application information for PC5 unicast communication. The application information includes ProSe service information and the application layer ID of the originating UE. The application layer ID of the target UE may be included in the application information. If UE-1 decides to reuse an existing PC5 unicast link, as specified in Clause 5.3.4, and thus decides to modify the unicast link established with UE-2, then UE-1 sends a link modification request to UE-2. ​

[0221] The link modification request message contains:

[0222] a) To add a new PC5 QoS flow to an existing PC5 unicast link:

[0223] - QoS information: Information about the PC5 QoS flow to be added. For each PC5 QoS flow, it is the PFI, the corresponding PC5 QoS parameters (i.e., PQI and optionally other parameters such as MFBR / GFBR, etc.), and optionally the associated ProSe identifier.

[0224] - Optional PC5 QoS rules.

[0225] b) To modify a PC5 QoS flow in an existing PC5 unicast link:

[0226] - QoS information: Information about the PC5 QoS flow to be modified. For each PC5 QoS flow, it is the PFI, the corresponding PC5 QoS parameters (i.e., PQI and optionally other parameters such as MFBR / GFBR, etc.), and optionally the associated ProSe identifier.

[0227] - Optional PC5 QoS rules.

[0228] c) To remove a PC5 QoS flow from an existing PC5 unicast link:

[0229] - PFI.

[0230] 2. UE-2 responds with a link modification acceptance message.

[0231] The link modification acceptance message contains:

[0232] - For cases a) and b) described in step 1:

[0233] - QoS information: Information about the PC5 QoS flow requested by UE-1. For each PC5 QoS flow, it is the PFI, the corresponding PC5 QoS parameters (i.e., PQI and optionally other parameters such as MFBR / GFBR, etc.), and optionally the associated ProSe identifier.

[0234] - Optional PC5 QoS rules.

[0235] The ProSe 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.

[0236] […]

[0237] 6.4.3.7 Layer 2 Link Management over the PC5 Reference Point for 5G ProSe UE - to - UE Relaying

[0238] 6.4.3.7.1 Common Part of Layer 2 Link Management over the PC5 Reference Point for 5G ProSe UE - to - UE Relaying

[0239] For 5G ProSe communication via 5G ProSe UE - to - UE relaying as described in Clauses 6.7.1 and 6.7.2:

[0240] - The direct communication request message on the first - hop PC5 reference point contains:

[0241] - The user information ID of the source 5G ProSe end - UE: The identifier (i.e., the user information ID) of the source 5G ProSe end - UE that requests the relaying operation.

[0242] - The user information ID of the 5G ProSe UE - to - UE relaying: The identifier (i.e., the user information ID) of the UE - to - UE relaying provided to the source 5G ProSe end - UE during the 5G ProSe UE - to - UE relaying discovery procedure.

[0243] - The user information ID of the destination 5G ProSe end - UE: The identifier (i.e., the user information ID) of the destination 5G ProSe end - UE provided to the source 5G ProSe end - UE during the UE - to - UE relaying discovery procedure.

[0244] -(Optional) The destination layer 2 ID of the destination 5G ProSe end - UE: The unicast destination layer 2 ID of the destination 5G ProSe end - UE determined by the source 5G ProSe end - UE, as specified in Clause 5.8.2.4.

[0245] - ProSe service information: Information about the ProSe identifier for which the layer 2 link establishment is requested.

[0246] - RSC: The connectivity service provided by the 5G ProSe UE - to - UE relaying requested by the source 5G ProSe end - UE.

[0247] - Security information: Information used to establish the security for the first - hop PC5 link establishment.

[0248] Note 1: The security information is defined by SA WG3.

[0249] The direct communication request message on the second - hop PC5 reference point contains:

[0250] - The user information ID of the source 5G ProSe end - UE.

[0251] - User information ID of the target 5G ProSe end UE.

[0252] - User information ID of the 5G ProSe UE - to - UE relay.

[0253] - ProSe service information: Information about ProSe identifiers.

[0254] - RSC: Connectivity service requested by the source 5G ProSe end UE and provided by the 5G ProSe UE - to - UE relay.

[0255] - Security information: Information used to establish the security for the second - hop PC5 link establishment.

[0256] Note 2: The security information is defined by SA WG3.

[0257] The direct communication acceptance message on the second - hop PC5 reference point contains:

[0258] - User information ID of the target 5G ProSe end UE.

[0259] The direct communication acceptance message on the first - hop PC5 reference point contains:

[0260] - User information ID of the target 5G ProSe end UE.

[0261] - User information ID of the 5G ProSe UE - to - UE relay.

[0262] The link modification request message on the first - hop PC5 reference point contains:

[0263] - User information ID of the target 5G ProSe end UE: The identity of the target 5G ProSe end UE provided to the source 5G ProSe end UE during the UE - to - UE relay discovery procedure.

[0264] -(Optional) Destination layer 2 ID of the target 5G ProSe end UE: The unicast destination layer 2 ID of the target 5G ProSe end UE determined by the source 5G ProSe end UE, as specified in clause 5.8.2.4.

[0265] The link modification request message on the second - hop PC5 reference point contains:

[0266] - User information ID of the source 5G ProSe end UE.

[0267] - User information ID of the target 5G ProSe end UE.

[0268] The link modification acceptance message on the second - hop PC5 reference point contains:

[0269] - User information ID of the target 5G ProSe end UE.

[0270] The link modification acceptance message on the first-hop PC5 reference point contains:

[0271] - User information ID of the target 5G ProSe end UE.

[0272] 6.4.3.7.2 Layer 2 link management via the PC5 reference point for 5G ProSe layer 2 UE - to - UE relay

[0273] For 5G ProSe communication via 5G ProSe layer 2 UE - to - UE relay as described in Clause 6.7.2, the description in Clause 6.4.3.7.1 applies.

[0274] The message content on the PC5 reference point for unicast mode 5G ProSe direct communication described in Clauses 6.4.3.1 to 6.4.3.5 is the same for the end - to - end connection between peer 5G ProSe end UEs.

[0275] Editor's note: Whether the LIU between peer layer 2 end UEs has the same message content as the direct PC5 LIU message remains to be further studied.

[0276] 6.4.3.7.3 Layer 2 link management via the PC5 reference point for 5G ProSe layer 3 UE - to - UE relay

[0277] For 5G ProSe communication via 5G ProSe layer 3 UE - to - UE relay as described in Clause 6.7.1, the description in Clause 6.4.3.7.1 applies, but with the following differences and interpretations:

[0278] - In the security procedure of the first - hop PC5 reference point, the source 5G ProSe layer 3 end UE provides the IP address configuration or link - local IPv6 address and QoS information of the end - to - end QoS to the 5G ProSe layer 3 UE - to - UE relay. If the PC5 link is used to carry Ethernet traffic, then the source 5G ProSe layer 3 end UE provides its Ethernet MAC address instead of IP - related information.

[0279] - In the security procedure of the second - hop PC5 reference point, the 5G ProSe layer 3 UE - to - UE relay provides the IP address configuration or link - local IPv6 address and QoS information of the second - hop QoS to the target 5G ProSe end UE. If the PC5 link is used to carry Ethernet traffic, then the 5G ProSe layer 3 UE - to - UE relay provides the Ethernet MAC address of the source 5G ProSe layer 3 end UE instead of IP - related information.

[0280] - The direct communication acceptance message at the second-hop PC5 reference point further includes IP address configuration or link-local IPv6 address and QoS information of the second-hop QoS. If the PC5 link is used to transport Ethernet services, the target 5G ProSe layer 3 end UE provides its Ethernet MAC address instead of IP-related information.

[0281] - Considering the received second-hop QoS, the 5G ProSe layer 3 UE relay determines the QoS information of the first-hop QoS, and the direct communication acceptance message at the first-hop PC5 reference point further includes IP address configuration or link-local IPv6 address, QoS information of the first-hop QoS, and may include the IP address of the target 5G ProSe end UE. If the PC5 link is used to deliver Ethernet services, then the 5G ProSe layer 3 UE relay provides the Ethernet MAC address of the target 5G ProSe layer 3 end UE instead of IP-related information.

[0282] - In the link modification request message at the first-hop PC5 reference point, the source 5G ProSe end UE further includes QoS information of the end-to-end QoS. If the PC5 link is used to deliver Ethernet services, then the source 5G ProSe layer 3 end UE may provide its Ethernet MAC address.

[0283] - In the link modification request message at the second-hop PC5 reference point, the 5G ProSe layer 3 UE relay further includes QoS information of the second-hop QoS to the target 5G ProSe end UE. If the PC5 link is used to deliver Ethernet services, then the 5G ProSe layer 3 UE relay provides the Ethernet MAC address of the source 5G ProSe layer 3 end UE.

[0284] - The link modification acceptance message at the second-hop PC5 reference point further includes QoS information of the second-hop QoS. If the PC5 link is used to deliver Ethernet services, then the target 5G ProSe layer 3 end UE may provide its Ethernet MAC address.

[0285] - Considering the received second-hop QoS, the 5G ProSe layer 3 UE relay determines the QoS information of the first-hop QoS, and the link modification acceptance message at the first-hop PC5 reference point further includes QoS information of the first-hop QoS, and may include the IP address of the target 5G ProSe end UE. If the PC5 link is used to deliver Ethernet services, then the 5G ProSe layer 3 UE relay provides the Ethernet MAC address of the target 5G ProSe layer 3 end UE instead of IP-related information.

[0286] When the PC5 link between a 5G ProSe layer 3 UE and a relay between 5G ProSe layer 3 UEs is released, the relay between 5G ProSe layer 3 UEs may initiate a PC5 link release to the peer 5G ProSe layer 3 UE, or notify the peer 5G ProSe layer 3 UE that the peer PC5 link has been released.

[0287] 6.4.3.7.4 Layer 2 link management on the PC5 reference point for 5G ProSe UE - to - UE relay communication with discovery integrated

[0288] This clause is for 5G ProSe UE - to - UE relay communication with discovery procedures integrated, as described in clause 6.7.3.

[0289] The direct communication request message on the first - hop PC5 reference point contains:

[0290] - The user information ID of the source 5G ProSe UE.

[0291] - (Optional) The user information ID of the target 5G ProSe UE: The identity of the target 5G ProSe UE, provided that it is available from the ProSe application layer.

[0292] - (Optional) The destination layer 2 ID of the target 5G ProSe UE: The unicast destination layer 2 ID of the target 5G ProSe UE determined by the source 5G ProSe UE, as specified in clause 5.8.2.4.

[0293] - ProSe service information: Information about the ProSe identifier for which the layer 2 link establishment is requested.

[0294] - RSC: The connectivity service requested by the source 5G ProSe UE to be provided by the 5G ProSe UE - to - UE relay.

[0295] - Relay_indication: Indicates whether the direct communication request message can be forwarded by the 5G ProSe UE - to - UE relay.

[0296] - Security information: Information used to establish the security for the first - hop PC5 link establishment.

[0297] Note 1: The security information is defined by SA WG3.

[0298] The direct communication request message on the second - hop PC5 reference point contains:

[0299] - The user information ID of the source 5G ProSe UE.

[0300] - The user information ID of the 5G ProSe UE - to - UE relay.

[0301] -(Optional) User information ID of the target 5G ProSe end UE.

[0302] -ProSe service information: Information about ProSe identifiers.

[0303] -RSC: Connectivity service provided by 5G ProSe UE - to - UE relay requested by the source 5G ProSe end UE.

[0304] -Security information: Information used to establish security for the second - hop PC5 link establishment.

[0305] Note 2: Security information is defined by SA WG3.

[0306] The direct communication acceptance message on the second - hop PC5 reference point contains:

[0307] -User information ID of the target 5G ProSe end UE.

[0308] The direct communication acceptance message on the first - hop PC5 reference point contains:

[0309] -User information ID of the target 5G ProSe end UE.

[0310] -User information ID of the 5G ProSe UE - to - UE relay.

[0311] For 5G ProSe communication via 5G ProSe layer 3 UE - to - UE relay, additional explanations are as follows:

[0312] -In the security procedure at the second - hop PC5 reference point, the 5G ProSe layer 3 UE - to - UE relay provides IP address configuration or link - local IPv6 address to the target 5G ProSe end UE.

[0313] -The direct communication acceptance message on the second - hop PC5 reference point additionally contains IP address configuration or link - local IPv6 address (if using IP communication), and the Ethernet MAC address of the target 5G ProSe end UE (if using Ethernet communication). QoS information is not included in the security procedure or the direct communication acceptance message at the second - hop PC5 reference point.

[0314] -In the security procedure at the first - hop PC5 reference point, the source 5G ProSe end UE provides IP address configuration, link - local IPv6 address, and QoS information of end - to - end QoS to the 5G ProSe layer 3 UE - to - UE relay.

[0315] - The 5G ProSe layer 3 UE - to - UE relay uses layer 2 link modification to provide the QoS information of the second hop to the target 5G ProSe end UE, as described in clause 6.4.3.4.

[0316] - Considering the second - hop QoS received from the target 5G ProSe end UE, the 5G ProSe layer 3 UE - to - UE relay determines the QoS information of the first hop. The direct communication acceptance message on the first - hop PC5 reference point further includes IP address configuration or link - local IPv6 address, the QoS information of the first hop, and may include the IP address of the target 5G ProSe end UE (if using IP communication) or the Ethernet MAC address of the target 5G ProSe end UE (if using Ethernet communication).

[0317] For 5G ProSe communication via 5G ProSe layer 2 UE - to - UE relay, the message content on the PC5 reference point for unicast - mode 5G ProSe direct communication described in clauses 6.4.3.1 to 6.4.3.5 is the same for the end - to - end connection between peer 5G ProSe end UEs.

[0318] […]

[0319] 6.7 5G ProSe UE - to - UE Relay Communication

[0320] 6.7.1 5G ProSe Communication via 5G ProSe Layer 3 UE - to - UE Relay

[0321] 6.7.1.1 Layer 2 Link Establishment for PC5 Communication via 5G ProSe Layer 3 UE - to - UE Relay

[0322] Figure 6 .7.1.1 - 1 shows the procedure for layer 2 link establishment for communication via 5G ProSe layer 3 UE - to - UE relay.

[0323] [As described in "Layer 2 Link Establishment via 5G ProSe Layer 3 UE - to - UE Relay" in 3GPP TS23.304 V18.2.0 Figure 6 .7.1.1 - 1 is reproduced as Figure 11

[0324] 1. Perform service authorization and provisioning for the source 5G ProSe layer 3 end UE, the target 5G ProSe layer 3 end UE, and the 5G ProSe layer 3 UE - to - UE relay, as described in clause 6.2.

[0325] 2. The source 5G ProSe layer 3 end UE performs discovery of the 5G ProSe layer 3 UE - to - UE relay, as described in clause 6.3.2.4. ​

[0326] 3. The source 5G ProSe layer 3 end UE sends a direct communication request message to initiate a unicast layer 2 link establishment procedure for relaying between 5G ProSe layer 3 UEs. The parameters included in the direct communication request message are described in Clause 6.4.3.7.

[0327] The source layer 2 ID of the direct communication request message is assigned by the source 5G ProSe layer 3 end UE itself, and the destination layer 2 ID is set to the source layer 2 ID of the discovery message for relaying between 5G ProSe layer 3 UEs.

[0328] 4. If the user information ID of the 5G ProSe layer 3 UE relay in the direct communication request message matches the user information ID of the 5G ProSe UE relay, and the RSC in the direct communication request matches one of the RSCs supported by the relay, then the 5G ProSe layer 3 UE relay responds by establishing security with the source 5G ProSe layer 3 end UE. When security protection is enabled, the source 5G ProSe layer 3 end UE sends the parameters described in Clause 6.4.3.7 to the 5G ProSe layer 3 UE relay.

[0329] If the Ethernet MAC address of the source 5G ProSe layer 3 end UE is already in use by another 5G ProSe layer 3 end UE, then the 5G ProSe layer 3 UE relay may send a message indicating the existence of an Ethernet MAC address conflict to the source 5G ProSe layer 3 end UE.

[0330] The source layer 2 ID for the security establishment procedure is assigned by the 5G ProSe layer 3 UE relay itself, and the destination layer 2 ID is set to the source layer 2 ID of the received direct communication request message.

[0331] The 5G ProSe layer 3 UE relay will select different source layer 2 IDs for PC5 links for different types of services (i.e., IP service, Ethernet service, and unstructured service).

[0332] If the PC5 link is used to carry unstructured service, then the 5G ProSe layer 3 UE relay will select different source layer 2 IDs for different pairs of source and target 5G ProSe layer 3 end UEs.

[0333] After receiving the security establishment procedure message, the source 5G ProSe layer 3 end UE obtains the layer 2 ID of the 5G ProSe layer 3 UE relay for future communication, thus for signaling and data services of this unicast link.

[0334] 5. After the security establishment procedure in step 4 is completed, the 5G ProSe layer 3 UE - to - UE relay sends a direct communication request message to initiate a unicast layer 2 link establishment procedure with the target 5G ProSe layer 3 end - UE. The parameters contained in the direct communication request message are described in clause 6.4.3.7.

[0335] The source layer 2 ID of the direct communication request message is self - assigned by the 5G ProSe layer 3 UE - to - UE relay, and the destination layer 2 ID is the unicast layer 2 ID of the target 5G ProSe layer 3 end - UE associated with the user information ID of the target 5G ProSe layer 3 end - UE.

[0336] The 5G ProSe layer 3 UE - to - UE relay will select different source layer 2 IDs for PC5 links for different types of services (i.e., IP service, Ethernet service, and unstructured service).

[0337] If the PC5 link is used to carry unstructured service, then the 5G ProSe layer 3 UE - to - UE relay will select different source layer 2 IDs for different pairs of source and target 5G ProSe layer 3 end - UEs.

[0338] 6. If the user information ID of the target 5G ProSe layer 3 end - UE and the RSC contained in the direct communication request match the user information ID of the target UE and the RSC supported by the target UE, then the target 5G ProSe layer 3 end - UE responds by establishing security with the 5G ProSe layer 3 UE - to - UE relay. When security protection is enabled, the 5G ProSe layer 3 UE - to - UE relay sends the parameters described in clause 6.4.3.7 to the target 5G ProSe layer 3 end - UE.

[0339] The source layer 2 ID for the security establishment procedure is self - assigned by the target 5G ProSe layer 3 end - UE, and the destination layer 2 ID is set to the source layer 2 ID of the received direct communication request message.

[0340] After receiving the security establishment procedure message, the 5G ProSe layer 3 UE - to - UE relay obtains the layer 2 ID of the target 5G ProSe layer 3 end - UE for future communication, thus for signaling and data services of this unicast link.

[0341] 7. The target 5G ProSe layer 3 end - UE sends a direct communication acceptance message to the 5G ProSe layer 3 UE - to - UE relay with which security has been successfully established. The parameters contained in the direct communication acceptance message are described in clause 6.4.3.7.

[0342] 8. For IP service, an IPv6 prefix or an IPv4 address is allocated for the target 5G ProSe layer 3 end - UE, as defined in clause 5.5.1.4.

[0343] 9. After receiving a direct communication acceptance message from the target 5G ProSe layer 3 UE, the 5G ProSe layer 3 UE-to-UE relay sends a direct communication acceptance message to the source 5G ProSe layer 3 UE for which security has been successfully established. The parameters included in the direct communication acceptance message are described in Clause 6.4.3.7.

[0344] 10. For IP services, an IPv6 prefix or an IPv4 address is allocated for the source 5G ProSe layer 3 UE, as defined in Clause 5.5.1.4.

[0345] 11. For IP communication, the 5G ProSe layer 3 UE-to-UE relay may store the association of the user information ID and the IP address of the target 5G ProSe layer 3 UE in its DNS entries, and the 5G ProSe layer 3 UE-to-UE relay may act as a DNS server for other UEs. If the IP address of the target 5G ProSe layer 3 UE is not received in step 9, then after step 10, the source 5G ProSe layer 3 UE may send a DNS query to the 5G ProSe layer 3 UE-to-UE relay to request the IP address of the target 5G ProSe layer 3 UE, and the 5G ProSe layer 3 UE-to-UE relay returns the IP address of the target 5G ProSe layer 3 UE to the source 5G ProSe layer 3 UE.

[0346] For Ethernet communication, the 5G ProSe layer 3 UE-to-UE relay maintains the association between the PC5 link and the Ethernet MAC address received from the 5G ProSe layer 3 UE.

[0347] For unstructured service communication, for each pair of source and target 5G ProSe layer 3 UEs, the 5G ProSe layer 3 UE-to-UE relay maintains a 1:1 mapping between the PC5 link with the source 5G ProSe layer 3 UE and the PC5 link with the target 5G ProSe layer 3 UE.

[0348] 12. The source 5G ProSe layer 3 UE communicates with the target 5G ProSe layer 3 UE via the 5G ProSe layer 3 UE-to-UE relay.

[0349] In the case where a source 5G ProSe layer 3 UE communicates with multiple target 5G ProSe layer 3 UEs, according to the RSC, the PC5 link between the source 5G ProSe layer 3 UE and the relay between 5G ProSe layer 3 UEs can be shared among the multiple target 5G ProSe layer 3 UEs. At the same time, according to the RSC, the PC5 link can be established separately between the relay between 5G ProSe layer 3 UEs and the target 5G ProSe layer 3 UE. For the shared PC5 link, the layer 2 link modification procedure shall be used.

[0350] In the case where multiple source 5G ProSe layer 3 UEs communicate with a target 5G ProSe layer 3 UE, according to the RSC, the PC5 link between the relay between 5G ProSe layer 3 UEs and the target 5G ProSe layer 3 UE can be shared. At the same time, according to the RSC, the PC5 link can be established separately between the source 5G ProSe layer 3 UEs and the relay between 5G ProSe layer 3 UEs. For the shared PC5 link, the layer 2 link modification procedure shall be used.

[0351] […]

[0352] 6.7.1.4 Layer 2 Link Modification for PC5 Communication via 5G ProSe Layer 3 UE - to - UE Relay

[0353] Figure 6 .7.1.4 - 1 shows the layer 2 link modification procedure via the layer 3 UE - to - UE relay. This procedure is used to add / modify / remove PC5 QoS flows in an existing PC5 unicast link, as described in clause 6.4.3.7.3.

[0354] [The one titled "Layer 2 Link Modification Procedure via Layer 3 UE - to - UE Relay" in 3GPP TS23.304 V18.2.0 Figure 6 .7.1.4 - 1 is reproduced as Figure 12

[0355] 0. A unicast link is established between UE - 1 and the UE - to - UE relay and between the UE - to - UE relay and UE - 2, as described in clause 6.7.1.1.

[0356] 1. UE - 1 sends a link modification request to the UE - to - UE relay, as described in clause 6.4.3.7.3.

[0357] 2. After receiving the link modification request message from UE - 1, the UE - to - UE relay sends a link modification request to UE - 2, as described in clause 6.4.3.7.3.

[0358] 3. UE - 2 responds to the UE - to - UE relay with a link modification acceptance message, as described in clause 6.4.3.7.3.​

[0359] 4. After receiving the link modification acceptance message from UE-2, the inter-UE relay responds to UE-1 with the link modification acceptance message as described in clause 6.4.3.7.3.

[0360] […]

[0361] 6.7.2 5G ProSe communication via layer 2 inter-UE relay

[0362] This procedure applies to layer 2 inter-UE relay for 5G ProSe.

[0363] [As described in clause 6.2, service authorization and provisioning have been performed for layer 2 inter-UE relay for 5G ProSe and 5G ProSe end UEs prior to this procedure. Figure 6 .7.2 -1 is reproduced as Figure 13

[0364] 1. Perform Model A or Model B 5G ProSe inter-UE relay discovery as described in clause 6.3.2.4, and the source 5G ProSe end UE selects a suitable layer 2 inter-UE relay for 5G ProSe to communicate with the target 5G ProSe end UE.

[0365] 2. The source 5G ProSe end UE decides whether to use the existing PC5 link with the layer 2 inter-UE relay to obtain the required service. If the existing PC5 link is used, then use the layer 2 link modification procedure as specified in clause 6.4.3.7 towards the layer 2 inter-UE relay; otherwise, use the layer 2 link establishment procedure towards the layer 2 inter-UE relay.

[0366] 3. This procedure is towards the selected layer 2 inter-UE relay for 5G ProSe, and for layer 2 link establishment, security establishment is performed before initiating step 3.

[0367] 3. The layer 2 inter-UE relay for 5G ProSe decides whether to use the existing PC5 link between the layer 2 inter-UE relay and the target 5G ProSe end UE to obtain the required service, and initiates the layer 2 link establishment procedure or the layer 2 link modification procedure as specified in clause 6.4.3.7 with the target 5G ProSe end UE.

[0368] This procedure is performed using the unicast layer 2 ID towards the target 5G ProSe end UE.

[0369] ​​

[0370] After step 3 is completed, the 5G ProSe layer 2 inter-UE relay sends a direct communication acceptance message or a link modification acceptance message to the source 5G ProSe end UE.

[0371] 4. The source 5G ProSe end UE establishes an end-to-end connection for unicast mode communication with the target 5G ProSe end UE, as described in clause 6.4.3.7.

[0372] Data is transferred between the source 5G ProSe end UE and the target 5G ProSe end UE via the 5G ProSe layer 2 inter-UE relay. The 5G ProSe layer 2 inter-UE relay forwards all data messages between the source 5G ProSe end UE and the target 5G ProSe end UE, as specified in TS 38.300

[12] .

[0373] 6.7.3 5G ProSe inter-UE relay communication integrated with discovery

[0374] 6.7.3.1 Overview

[0375] Supports 5G ProSe communication via the 5G ProSe inter-UE relay integrated with discovery.

[0376] For 5G ProSe inter-UE relay communication integrated with discovery, when a UE permits a direct communication request to another UE that involves an inter-UE relay, the UE indicates this by including relay_indication in the broadcast direct communication request message.

[0377] When the inter-UE relay receives a direct communication request containing relay_indication, it decides whether to forward the message based on, for example, the relay service code (if present), the application ID, the operator policy for each relay service code, the signal strength, and the local policy.

[0378] 6.7.3.2 Procedures for communication via layer 3 inter-UE relay

[0379] [As titled "5G ProSe inter-UE relay communication integrated with discovery via layer 3 inter-UE relay" in 3GPP TS23.304 V18.2.0 Figure 6 .7.3.2-1 is reproduced as Figure 14

[0380] 0.5G ProSe end UEs are authorized and provisioned with parameters to use the services provided by the 5G ProSe inter-UE relay. The 5G ProSe inter-UE relay is authorized and provisioned with parameters to provide services for relaying traffic among 5G ProSe end UEs. ​

[0381] 1. The source 5G ProSe end UE (i.e., UE-1) wants to establish unicast communication with the destination 5G ProSe end UE (i.e., UE-2) and broadcasts a direct communication request. The parameters included in the direct communication request message are described in Clause 6.4.3.7.

[0382] The relay_indication in the direct communication request is used to indicate whether the 5G ProSe UE-to-UE relay can forward the direct communication request message. It is also used to limit the hop count of the 5G ProSe UE-to-UE relay by removing the relay_indication from the direct communication request message from the 5G ProSe UE-to-UE relay.

[0383] The source layer 2 ID and the destination layer 2 ID for the direct communication request message are defined in Clause 5.8.5.

[0384] Note 1: The data type of the relay_indication can be determined in Phase 3.

[0385] 2. When receiving a direct communication request with relay_indication from UE-1, the 5G ProSe UE-to-UE relay (i.e., Relay-1 and Relay-2) can decide to participate in the procedure and broadcast the direct communication request message in its vicinity without the relay_indication. The parameters included in the direct communication request message are described in Clause 6.4.3.7.

[0386] The source layer 2 ID and the destination layer 2 ID for the direct communication request message are defined in Clause 5.8.5.

[0387] 3. When UE-2 receives a direct communication request from one or more 5G ProSe UE-to-UE relays, UE-2 selects the 5G ProSe UE-to-UE relay to which UE-2 will respond. UE-2 can select the 5G ProSe UE-to-UE relay based on, for example, signal strength, local policy, operator policy for each relay service code (if any).

[0388] 4. If needed, security establishment occurs between UE-2 and the selected 5G ProSe UE-to-UE relay (here Relay-1).

[0389] If the existing PC5 link can be reused, then the link modification request and link modification acceptance messages are used.

[0390] Note 2: The conflict between the link modification request and the direct communication request can be determined in Phase 3.

[0391] 5. UE-2 replies to Relay-1 with a direct communication acceptance message. The parameters included in the direct communication acceptance message are described in Clause 6.4.3.7.

[0392] 6. For IP services, an IPv6 prefix or an IPv4 address is allocated to the target 5G ProSe layer 3 end UE, as defined in Clause 5.5.1.4.

[0393] 7. If required, security establishment occurs between UE-1 and Relay-1.

[0394] 8. For 5G ProSe UE-to-UE relay communication integrated with discovery, after receiving the QoS information of the end-to-end QoS from UE-1, Relay-1 provides the QoS information of the second-hop QoS to UE-2 using a link modification request message.

[0395] 9. For 5G ProSe UE-to-UE relay communication integrated with discovery, UE-2 responds with a link modification acceptance message.

[0396] 10. Relay-1 responds to UE-1 with a direct communication acceptance. The parameters included in the direct communication acceptance message are described in Clause 6.4.3.7.

[0397] 11. For IP services, an IPv6 prefix or an IPv4 address is allocated to the source 5G ProSe layer 3 end UE, as defined in Clause 5.5.1.4.

[0398] 12. For IP communication, the 5G ProSe layer 3 UE-to-UE relay can store the association of the user information ID and the IP address of the target 5G ProSe layer 3 end UE in its DNS entry, and the 5G ProSe layer 3 UE-to-UE relay can act as a DNS server for other UEs. If the IP address of the target 5G ProSe layer 3 end UE is not received in Step 10, then after Step 11, the source 5G ProSe layer 3 end UE can send a DNS query to the 5G ProSe layer 3 UE-to-UE relay to request the IP address of the target 5G ProSe layer 3 end UE, and the 5G ProSe layer 3 UE-to-UE relay returns the IP address of the target 5G ProSe layer 3 end UE to the source 5G ProSe layer 3 end UE.

[0399] For Ethernet communication, the 5G ProSe layer 3 UE-to-UE relay acts as an Ethernet switch by maintaining the association between the PC5 link and the Ethernet MAC address received from the 5G ProSe layer 3 end UE.

[0400] For unstructured service communication, for each pair of source and destination 5G ProSe layer 3 UE, the 5G ProSe layer 3 UE - to - UE relay maintains a 1:1 mapping between the PC5 link with the source 5G ProSe layer 3 UE and the PC5 link with the destination 5G ProSe layer 3 UE.

[0401] The source 5G ProSe layer 3 UE communicates with the destination 5G ProSe layer 3 UE via the 5G ProSe layer 3 UE - to - UE relay.

[0402] 6.7.3.3 Procedures for communication via layer 2 UE - to - UE relay

[0403] [The content titled "5G ProSe UE - to - UE relay communication integrated with discovery via layer 2 UE - to - UE relay" in 3GPP TS23.304 V18.2.0 Figure 6 .7.3.3 - 1 is reproduced as Figure 15

[0404] Steps 0 to step 5 are the same as Figure 6 Steps 0 to step 5 of.7.3.2 - 1.

[0405] Step 6 is the same as Figure 6 Step 7 of.7.3.2 - 1.

[0406] Step 7 is the same as Figure 6 Step 10 of.7.3.2 - 1. The parameters included in the message are described in clause 6.4.3.7.

[0407] 8. For 5G ProSe UE - to - UE relay communication via layer 2 UE - to - UE relay, UE - 1 establishes an end - to - end connection for unicast mode communication with UE - 2, as described in clause 6.4.3.7.

[0408] Editor's note: Any additional updates to the procedures including those via layer 2 UE - to - UE relay, such as updates based on RAN decisions, will be included here.

[0409] 3GPP TS24.554 introduces the following:

[0410] 7.2.2 5G ProSe direct link establishment procedures

[0411] 7.2.2.1 Overview

[0412] ​Depending on the type of 5G ProSe direct link establishment procedure (i.e., UE-oriented layer 2 link establishment or ProSe service-oriented layer 2 link establishment in 3GPP TS 23.304 [2]), the 5G ProSe direct link establishment procedure is used to establish a 5G ProSe direct link between two UEs or multiple 5G ProSe direct links between a UE and multiple target UEs. The UE that sends the request message is called the "initiating UE", and the other UE is called the "target UE". If the request message does not indicate a specific target UE (i.e., the target user information is not included in the request message) and multiple target UEs are interested in the ProSe application indicated in the request message, the initiating UE will process the corresponding response messages received from those target UEs. The maximum number of 5G ProSe direct links established in a UE at any time should not exceed the implementation-specific maximum number of 5G ProSe direct links established.

[0413] […]

[0414] When the 5G ProSe direct link establishment procedure for a 5G ProSe layer 3 remote UE is successfully completed, and if there is a PDU session established for relaying the traffic of the 5G ProSe remote UE, the 5G ProSe layer 3 UE-to-network relay UE will perform the remote UE reporting procedure as specified in 3GPP TS 24.501

[11] .

[0415] Note 2: A single PC5 unicast link is established between the 5G ProSe layer 2 UE-to-network relay UE and the 5G ProSe layer 2 remote UE to support the PDU session of the 5G ProSe layer 2 remote UE, as specified in 3GPP TS 38.300

[21] .

[0416] 7.2.2.2 Initiation of 5G ProSe direct link establishment procedure by the initiating UE

[0417] The initiating UE shall meet the following prerequisites before initiating this procedure:

[0418] a) A request from the upper layer transmits data packets for the ProSe application via PC5, or a request from the lower layer triggers the ProSe direct link establishment;

[0419] b) The communication mode is the unicast mode (e.g., pre-configured as specified in Clause 5.2.4 or indicated by the upper layer);

[0420] c) The link layer identifier for the initiating UE (i.e., the layer 2 ID for unicast communication) is available (e.g., pre-configured or self-assigned) and is not used by other existing 5G ProSe direct links within the initiating UE;

[0421] d) The link layer identifier for the destination UE (i.e., the unicast layer 2 ID or broadcast layer 2 ID of the target UE) can be used by the initiating UE (e.g., obtained through pre-configuration, as specified in Clause 5.2, known from previous ProSe direct communication, or indicated by the lower layer).

[0422] Note 1: In cases where different ProSe applications are mapped to different default destination layer 2 IDs, when the initiating UE wishes to establish a single unicast link that can be used for more than one ProSe identifier, the UE can select any of the default destination layer 2 IDs for unicast initial signaling.

[0423] e) The initiating UE is authorized to perform 5G ProSe direct communication on PC5 in NR-PC5 in the serving PLMN, has a valid authorization for 5G ProSe direct communication on PC5 in NR-PC5 when not served by NG-RAN, is authorized to use a 5G ProSe UE-to-network relay UE, is authorized to use a 5G ProSe UE-to-UE relay UE, or is authorized to act as a 5G ProSe UE-to-UE relay UE. The UE considers itself not served by NG-RAN if the following conditions are met:

[0424] 1) Not served by NG-RAN to perform ProSe direct communication via PC5;

[0425] 2) In a restricted service state as specified in 3GPP TS 23.122

[14] , provided that the reason for the UE being in the restricted service state is one of the following;

[0426] i) The UE cannot find a suitable cell in the selected PLMN, as specified in 3GPP TS 38.304

[15] ;

[0427] ii) The UE receives a registration rejection message or service rejection message with 5GMM cause #11 "PLMN not allowed", as specified in 3GPP TS 24.501

[11] ; or

[0428] iii) The UE receives a registration rejection message or service rejection message with 5GMM cause #7 "5GS service not allowed", as specified in 3GPP TS 24.501

[11] ; or

[0429] 3) In a limited service state as specified in 3GPP TS 23.122

[14] for reasons other than i), ii), or iii) above, and located in a geographical area where the UE has "non-operator managed" radio parameters as specified in Clause 5.2.

[0430] Editor's Note: The UE characteristics in a limited service state in the case of direct communication between a 5G ProSe end UE and a relay UE between 5G ProSe UEs for the 5G ProSe direct link establishment procedure need to be re-discussed, which will be determined by SA2.

[0431] f) There is no existing 5G ProSe direct link for a pair of peer application layer IDs, or there is an existing 5G ProSe direct link for a pair of peer application layer IDs, and:

[0432] […]

[0433] 5) In the case where the 5G ProSe direct link establishment procedure is used for direct communication between a 5G ProSe layer 3 end UE and a relay UE between 5G ProSe layer 3 UEs, the existing 5G ProSe direct link for the peer UE is established with a different RSC, or is established but not used for direct communication between the 5G ProSe layer 3 end UE and the relay UE between 5G ProSe layer 3 UEs;

[0434] g) The number of established 5G ProSe direct links is less than the implementation-specific maximum number of established 5G ProSe direct links allowed in the UE each time;

[0435] h) The timer T5088 is not associated with the link layer identifier of the destination UE or the timer T5088 associated with the link layer identifier of the destination UE has expired or stopped.

[0436] i) In the following cases: The UE acts as a relay UE between 5G ProSe layer 3 UEs, the 5G ProSe direct link modification procedure is initiated on the existing 5G ProSe direct link for direct communication between a 5G ProSe layer 3 end UE and a relay UE between 5G ProSe layer 3 UEs, and there is no existing 5G ProSe direct link between the relay UE between 5G ProSe layer 3 UEs and an additional target 5G ProSe layer 3 end UE. The PROSE direct link modification request message is received from the 5G ProSe layer 3 end UE to establish 5G ProSe UE - to - UE relay communication with the additional 5G ProSe layer 3 end UE, as specified in Clause 7.2.3.2; and

[0437] j) The initiating UE has received a PROSE direct link establishment request message containing a relay indication, and the initiating UE acts as a relay UE between 5G ProSe UEs, and the 5G ProSe direct link establishment procedure is for direct communication between the relay UE between 5G ProSe UEs and a 5G ProSe end UE

[0438] After receiving service data or requests from upper layers, the initiating UE shall derive the PC5 QoS parameters and assign a PQFI for establishing PC5 QoS flows as specified in clause 7.2.7.

[0439] If the 5G ProSe direct link establishment procedure is used for direct communication between a 5G ProSe remote UE and a 5G ProSe UE-to-network relay UE, the UE shall apply DUCK or DUSK, where the associated encrypted bitmask is used for UE-to-network relay discovery and the UTC-based counter is used for encryption:

[0440] a) The relay service code; and

[0441] b) The UP-PRUK ID or CP-PRUK ID (if available),

[0442] as specified in clause 6.3.5.2 of 3GPP TS 33.503

[34] , and the UE shall use the security-protected relay service code and the security-protected UP-PRUK ID or security-protected CP-PRUK ID to create a ProSe direct link establishment request message.

[0443] Note 2: If the UE is neither configured to use DUCK nor configured to use DUSK, then the relay service code and the UP-PRUK ID or CP-PRUK ID are not encrypted.

[0444] If the 5G ProSe direct link establishment procedure is used for direct communication between a 5G ProSe UE-to-UE relay UE and a target 5G ProSe end UE, and the initiating UE acting as the 5G ProSe UE-to-UE relay UE cannot identify an existing 5G ProSe direct link established between the initiating UE and the target UE after receiving a PROSE direct link establishment request message using integrated discovery (i.e., where the destination L2ID is set to the broadcast value as specified in clause 5.2.4 and the relay indication is included), then the initiating UE shall initiate a 5G ProSe direct link establishment procedure to the target 5G ProSe end UE.

[0445] If the 5G ProSe direct link establishment procedure is used for direct communication between a 5G ProSe UE-to-UE relay UE and a target 5G ProSe end UE without integrated discovery, then the initiating UE acting as the 5G ProSe UE-to-UE relay UE shall initiate a 5G ProSe direct link establishment procedure to the target 5G ProSe end UE after successfully completing the 5G ProSe direct link security mode control procedure with the source 5G ProSe end UE.

[0446] […]

[0447] To initiate the 5G ProSe direct link establishment procedure, the initiating UE shall generate a ProSe direct link establishment request message. Initiating UE:

[0448] a) shall contain source user information, which is set to the application layer ID of the initiating UE received from the upper layer, or to the user information ID of the source 5G ProSe end UE in the case of 5G ProSe direct communication between a 5G ProSe end UE and a relay UE between 5G ProSe UEs in the 5G ProSe direct link establishment procedure;

[0449] b) shall contain the ProSe identifier received from the upper layer if the 5G ProSe direct link establishment procedure is not for 5G ProSe direct communication between a 5G ProSe remote UE and a relay UE from a 5G ProSe UE to the network;

[0450] c) shall contain destination user information, which is set to the application layer ID of the destination UE if received from the upper layer or if known based on the unicast layer 2 ID of the destination UE (i.e., the destination layer 2 ID) as described in clause 5.8.2.4 of 3GPP TS 23.304 [3], set to the user information ID of the 5G ProSe UE-to-network relay UE obtained during the 5G ProSe UE-to-network relay discovery procedure, or set to the user information ID of the destination 5G ProSe end UE:

[0451] 1) if the initiating UE acts as the source 5G ProSe end UE and the user information ID of the destination 5G ProSe end UE is obtained during the 5G ProSe UE-to-UE relay discovery procedure; or

[0452] 2) if the initiating UE acts as a 5G ProSe UE-to-UE relay UE and the user information ID of the destination 5G ProSe end UE is obtained in a PROSE direct link establishment request message or a PROSE direct link modification request message from the source 5G ProSe end UE;

[0453] ca) shall contain UE-to-UE relay UE user information set to the user information ID of the 5G ProSe UE-to-UE relay UE:

[0454] 1) if obtained during the 5G ProSe UE-to-UE relay discovery procedure and the 5G ProSe direct link establishment procedure is for 5G ProSe direct communication between a source 5G ProSe end UE and a 5G ProSe UE-to-UE relay UE; or

[0455] 2) If the originating UE acts as a 5G ProSe UE - to - UE relay UE and the user information ID is configured under the configuration parameters for 5G ProSe UE - to - UE relay as specified in clause 5.2.7;

[0456] cb) If the originating UE acts as a source 5G ProSe end - UE and the Layer 2 ID of the target 5G ProSe end - UE is available in the source 5G ProSe end - UE via a previous direct communication, then the target end - UE Layer 2 ID set to the Layer 2 ID of the target 5G ProSe end - UE will be included;

[0457] d) If the 5G ProSe direct link is not used for direct communication between a 5G ProSe remote UE and a 5G ProSe UE - to - network relay UE:

[0458] 1) If the UE PC5 unicast signaling integrity protection policy is set to "Signaling integrity protection required" or "Signaling integrity protection preferred", then the key establishment information container will be included, and if the UE PC5 unicast signaling integrity protection policy is set to "No signaling integrity protection required", then the key establishment information container may be included;

[0459] Note 3: The key establishment information container is provided by the upper layer.

[0460] […]

[0461] j) The relay service code IE will be included, which is set to the relay service code of the target relay UE in the case where the 5G ProSe direct link establishment procedure is used for direct communication between a 5G ProSe remote UE and a 5G ProSe UE - to - network relay UE, or is set to the relay service code indicating the connectivity service requested by the source 5G ProSe end - UE in the case where the 5G ProSe direct link establishment procedure is used for direct communication between a (source or target) 5G ProSe end - UE and a 5G ProSe UE - to - UE relay UE;

[0462] […]

[0463] p) The relay indication will be included, which indicates that the PROSE direct link establishment request message can be forwarded by a 5G ProSe UE - to - UE relay UE, provided that the 5G ProSe direct link establishment procedure is used for direct communication between a source 5G ProSe end - UE and a 5G ProSe UE - to - UE relay UE;

[0464] Editor's note: The security parameters for 5G ProSe UE - to - UE relay and the parameters for 5G ProSe Layer 2 UE - to - UE relay are subject to further study.

[0465] After generating the ProSe direct link establishment request message, the initiating UE passes this message, along with the source layer 2 ID and the destination layer 2 ID, to the lower layer for transmission as follows:

[0466] a) If 5G ProSe direct communication is due to 5G ProSe direct discovery as defined in clauses 6.2.14, 6.2.15, 8.2.1, and 8a.2.1:

[0467] Self-assign the source layer 2 ID, and

[0468] 1) Set the destination layer 2 ID to the target end UE layer 2 ID received in the ProSe direct link establishment request message or ProSe direct link modification request message from the source 5G ProSe end UE if the initiating UE acts as a 5G ProSe UE - to - UE relay UE;

[0469] 2) Otherwise, set it to the destination layer 2 ID of the source layer 2 ID in the received ProSe PC5 discovery message for the discovery procedure;

[0470] b) If the initiating UE acts as a source 5G ProSe end UE and the 5G ProSe direct link establishment procedure is for integrated discovery - based direct communication between the source 5G ProSe end UE and a 5G ProSe UE - to - UE relay UE:

[0471] Self - assign the source layer 2 ID and set the destination layer 2 ID to the broadcast destination layer 2 ID configured as specified in clause 5.2.4; or

[0472] c) If the initiating UE acts as a 5G ProSe UE - to - UE relay UE and the 5G ProSe direct link establishment procedure is for integrated discovery - based direct communication between the 5G ProSe UE - to - UE relay UE and a target 5G ProSe end UE:

[0473] Self - assign the source layer 2 ID and set the destination layer 2 ID to:

[0474] 1) The target end UE layer 2 ID if received in the ProSe direct link establishment request message from the source 5G ProSe end UE; otherwise

[0475] 2) The broadcast destination layer 2 ID configured as specified in clause 5.2.4; or

[0476] d) Otherwise:

[0477] Self - assign the source layer 2 ID and the destination layer 2 ID set to the destination layer 2 ID for unicast initial signaling specified in clause 5.2.4,

[0478] Note 6: The UE implementation ensures that any value of the self-assigned source layer 2 ID in a) and b) is different from any other self-assigned source layer 2 ID used for 5G ProSe direct discovery specified in Clause 6.2.14, Clause 6.2.15, and Clause 8.2.1, and is different from any other provided destination layer 2 ID specified in Clause 5.2.

[0479] Note 6A: The UE implementation ensures that any value of the self-assigned source layer 2 ID in a) and b) is different from any source layer 2 ID self-assigned when used for 5G ProSe direct communication where the data unit type is different from the data unit type of the established 5G ProSe direct link, if the 5G ProSe direct link establishment procedure is used for 5G ProSe direct communication between a 5G ProSe layer 3 inter-UE relay UE and a target 5G ProSe layer 3 end UE.

[0480] Note 6B: The UE implementation ensures that any value of the self-assigned source layer 2 ID in a) and b) is different from any other self-assigned source layer 2 ID and different user information IDs of the source 5G ProSe end UE and the target 5G ProSe end UE for different pairs when used for 5G ProSe direct communication for unstructured services, if the 5G ProSe direct link establishment procedure is used for 5G ProSe direct communication between a 5G ProSe layer 3 inter-UE relay UE and a target 5G ProSe layer 3 end UE and is used for unstructured services.

[0481] Note 7: The initiating UE may reuse the layer 2 ID of the initiating UE used in a previous 5G ProSe direct link with the same peer UE, except when the 5G ProSe direct link establishment procedure is used for 5G ProSe direct communication between a 5G ProSe layer 3 inter-UE relay UE and a target 5G ProSe layer 3 end UE for unstructured services and different user information IDs of the source 5G ProSe end UE and the target 5G ProSe end UE for different pairs, and except when the 5G ProSe direct link establishment procedure is used for 5G ProSe direct communication between a 5G ProSe layer 3 inter-UE relay UE and a target 5G ProSe layer 3 end UE where the data unit type is different from the data unit type of the previous 5G ProSe direct link.

[0482] And start timer T5080.

[0483] Note 8: The predefined PC5 DRX configuration is used to transmit the ProSe direct link establishment request message, as specified in 3GPP TS 38.300

[21] .

[0484] When the timer T5080 is running, the UE shall not send a new ProSe direct link establishment request message to the same target UE identified by the same application layer ID. If the target user information IE is not included in the ProSe direct link establishment request message (i.e., the 5G ProSe direct link establishment procedure for ProSe applications), the initiating UE shall process multiple ProSe direct link establishment acceptance messages (if any) received from different target UEs before the timer T5080 expires for establishing multiple 5G ProSe direct links.

[0485] Note 9: To ensure successful 5G ProSe direct link establishment, T5080 shall be set to a value greater than the sum of T5089 and T5092.

[0486] Figure 7 .2.2.2.1 in Figure 16

[0487] Figure 7 .2.2.2.2 in Figure 17

[0488] 7.2.2.3 5G ProSe direct link establishment procedure accepted by the target UE

[0489] After receiving the ProSe direct link establishment request message, if the target UE accepts this request, the target UE shall uniquely assign a PC5 link identifier and generate a 5G ProSe direct link context.

[0490] Note 1: The preconfigured PC5 DRX configuration is used to receive the ProSe direct link establishment request message, as specified in 3GPP TS 38.300

[21] .

[0491] If the ProSe direct link establishment request message is for 5G ProSe direct communication between a 5G ProSe remote UE and a 5G ProSe UE-to-network relay UE, the target UE shall verify the MIC field in the received ProSe direct link establishment request with DUIK (if any) and decrypt the encrypted:

[0492] a) Relay service code; and

[0493] ​​​​b) The UP-PRUK ID or CP-PRUK ID (if received),

[0494] where the associated encrypted bitmask is used for 5G ProSe UE-to-network relay discovery (see clause 6.3.5.2 of 3GPP TS 33.503

[34] ) and to verify whether the relay service code matches the code sent by the target UE during the 5G ProSe UE-to-network relay discovery procedure.

[0495] Note 2: If the UE is not configured to use DUCK or DUSK, then the relay service code and the UP-PRUK ID or CP-PRUK ID are not encrypted.

[0496] If the target UE acts as the target 5G ProSe end UE and the 5G ProSe direct link establishment procedure is used for integrated discovery direct communication between the 5G ProSe UE-to-UE relay UE and the target 5G ProSe end UE, then after receiving a ProSe direct link establishment request message containing the same source user information, ProSe identifier, and relay service code as received from multiple 5G ProSe UE-to-UE relay UEs, the target UE selects one of the 5G ProSe UE-to-UE relay UEs used to communicate with the source 5G ProSe end UE, as specified in clause 6.7.3.2 of TS 23.304.

[0497] […]

[0498] If the target UE accepts the 5G ProSe direct link establishment procedure, then the target UE shall generate a ProSe direct link establishment acceptance message. The target UE:

[0499] a) Shall include the source user information, which is set to the application layer ID of the target UE received from the upper layer, or to the user information ID of the target 5G ProSe end UE in the case where the 5G ProSe direct link establishment procedure is used for 5G ProSe direct communication between the 5G ProSe end UE and the 5G ProSe UE-to-UE relay UE;

[0500] aa) Shall include the UE-to-UE relay UE user information, which is set to the user information ID of the 5G ProSe UE-to-UE relay UE in the case where the 5G ProSe direct link establishment procedure is used for 5G ProSe direct communication between the source 5G ProSe end UE and the 5G ProSe UE-to-UE relay UE;

[0501] b) Include the PQFI, the corresponding PC5 QoS parameters, and optionally the ProSe identifier accepted by the target UE, if the target UE does not act as a relay UE from the 5G ProSe layer 2 UE to the network and the 5G ProSe direct link establishment procedure is not integrated with discovery and is not used for 5G ProSe direct communication between the target 5G ProSe end UE and the relay UE between 5G ProSe UEs;

[0502] c) May include PC5 QoS rules, provided that the target UE does not act as a relay UE from the 5G ProSe layer 2 UE to the network and the 5G ProSe direct link establishment procedure is not integrated with discovery and is not used for 5G ProSe direct communication between the target 5G ProSe end UE and the relay UE between 5G ProSe UEs;

[0503] Editor's note: How to forward the PC5 QoS parameters and PQFI of the PC5 QoS flow between the 5G ProSe layer 3 UE relay UE and the 5G ProSe layer 3 end UE remains to be further studied.

[0504] d) If IP communication is used and the target UE does not act as a relay UE from the 5G ProSe layer 2 UE to the network, then include an IP address configuration IE set to one of the following values:

[0505] 1) "DHCPv4 server", if only the IPv4 address allocation mechanism is supported by the target UE, i.e., acting as a DHCPv4 server;

[0506] 2) "IPv6 router", if only the IPv6 address allocation mechanism is supported by the target UE, i.e., acting as an IPv6 router;

[0507] 3) "DHCPv4 server and IPv6 router", if both the IPv4 and IPv6 address allocation mechanisms are supported by the target UE; or

[0508] 4) "Address allocation not supported", if neither the IPv4 nor the IPv6 address allocation mechanism is supported by the target UE and the target UE does not act as a relay UE from the 5G ProSe layer 3 UE to the network;

[0509] Note 4: If the communication uses Ethernet or unstructured data unit types, then the UE does not include an IP address configuration IE nor a link-local IPv6 address IE.

[0510] e) If the IP address configuration IE is set to "Address allocation not supported", the received ProSe direct link security mode complete message contains a link-local IPv6 address IE and the target UE neither acts as a 5G ProSe layer 2 UE-to-network relay UE nor acts as a 5G ProSe layer 3 relay UE, then a link-local IPv6 address IE formed locally based on IETF RFC 4862

[25] will be included;

[0511] f) It shall include the configuration of UE PC5 unicast user plane security protection based on the agreed user plane security policy, as specified in 3GPP TS 33.503

[34] ;

[0512] Editor's note: The security parameters for 5G ProSe UE-to-UE relay and the parameters for 5G ProSe layer 2 UE-to-UE relay are subject to further study.

[0513] g) If the 5G ProSe direct link establishment procedure is used for 5G ProSe direct communication between a source or target 5G ProSe layer 3 end UE and a 5G ProSe layer 3 UE-to-UE relay UE and for Ethernet services, then the MAC address of the target 5G ProSe layer 3 end UE will be included; and

[0514] h) A target 5G ProSe layer 3 end UE IP address IE may be included, which is set to the IP address of the target 5G ProSe layer 3 end UE, if the 5G ProSe direct link establishment procedure is used for 5G ProSe direct communication between a source 5G ProSe layer 3 end UE and a 5G ProSe layer 3 UE-to-UE relay UE and the type of data unit for communication is IP.

[0515] Editor's note: The security parameters for 5G ProSe UE-to-UE relay and the parameters for 5G ProSe layer 2 UE-to-UE relay are subject to further study.

[0516] After generating the ProSe direct link establishment accept message, in the following cases, the initiating UE passes this message together with the layer 2 ID of the initiating UE for unicast communication and the layer 2 ID of the target UE for unicast communication to the lower layer for transmission, and starts timer T5090:

[0517] a) At least one ProSe identifier for the 5G ProSe direct link meets the privacy requirements specified in Clause 5.2.4; or

[0518] b) T5090 is configured as specified in Clause 5.2.5.

[0519] Note 5: The PC5 DRX configuration in the AS layer is negotiated between two UEs, and the PC5 DRX parameter values are configured according to a pair of source / destination layer 2 IDs in the AS layer, as specified in 3GPP TS 38.300

[21] .

[0520] After sending the ProSe direct link establishment acceptance message, the target UE provides the following information to the lower layer together with the layer 2 ID, which enables the lower layer to process the incoming PC5 signaling or traffic data:

[0521] a) The PC5 link identifier self-assigned for this 5G ProSe direct link;

[0522] b) The PQFI and its corresponding PC5 QoS parameters (if available); and

[0523] c) An indication to activate the PC5 unicast user plane security protection (if applicable) for the 5G ProSe direct link.

[0524] If the target UE accepts the 5G ProSe direct link establishment request and the 5G ProSe direct link is established but not used for 5G ProSe direct communication between the 5G ProSe remote UE and the 5G ProSe UE-to-network relay UE and not used for 5G ProSe direct communication between the 5G ProSe end UE and the 5G ProSe UE-to-UE relay UE, then the target UE can perform PC5 QoS flow establishment on the 5G ProSe direct link, as specified in Clause 7.2.7. If the 5G ProSe direct link is established for 5G ProSe direct communication between the 5G ProSe layer 3 remote UE and the 5G ProSe layer 3 UE-to-network relay UE, then the target UE can perform PC5 QoS flow establishment on the 5G ProSe direct link, as specified in Clause 8.2.6. If the 5G ProSe direct link is established for 5G ProSe direct communication between the 5G ProSe layer 3 end UE and the 5G ProSe layer 3 UE-to-UE relay UE, then the target UE can perform PC5 QoS flow establishment on the 5G ProSe direct link, as specified in Clause 8a.2.7.

[0525] 7.2.2.4 Completion of the 5G ProSe direct link establishment procedure by the initiating UE

[0526] If the target user information IE is included in the ProSe direct link establishment request message, then after receiving the ProSe direct link establishment acceptance message, the initiating UE shall stop timer T5080. If the target user information IE is not included in the ProSe direct link establishment request message, then the initiating UE may keep timer T5080 running and continue to process multiple response messages (i.e., ProSe direct link establishment acceptance messages) from multiple target UEs.

[0527] For each of the received ProSe direct link establishment acceptance messages, the initiating UE shall uniquely assign a PC5 link identifier and generate a 5G ProSe direct link context for each of the 5G ProSe direct links. Then, the initiating UE shall store the source layer 2 ID and the destination layer 2 ID used in the transmission of this message provided by the lower layer in the 5G ProSe direct link context to complete the establishment of the 5G ProSe direct link with the target UE. Henceforth, the initiating UE shall use the established link for ProSe direct communication via PC5 and additional PC5 signaling messages to the target UE.

[0528] If the initiating UE acts as a 5G ProSe UE - to - UE relay and the 5G ProSe direct link establishment procedure is for integrated discovery direct communication between the 5G ProSe UE - to - UE relay UE and the target 5G ProSe end - UE, then after receiving the ProSe direct link establishment acceptance message from the target 5G ProSe end - UE, the initiating UE shall initiate a 5G ProSe direct link security mode control procedure with the source 5G ProSe end - UE, and after successfully completing the 5G ProSe direct link security mode control procedure with the source 5G ProSe end - UE, the initiating UE shall create a ProSe direct link establishment acceptance message as specified in clause 7.2.2.3 to send to the source 5G ProSe end - UE.

[0529] After receiving the ProSe direct link establishment acceptance message, the initiating UE shall provide the following information together with the layer 2 ID to the lower layer so that the lower layer can process the incoming PC5 signaling or traffic data:

[0530] a) The PC5 link identifier self - assigned for this 5G ProSe direct link;

[0531] b) The PQFI and its corresponding PC5 QoS parameters (if available); and

[0532] c) An indication to activate PC5 unicast user plane security protection (if applicable) for the 5G ProSe direct link.

[0533] The initiating UE shall start timer T5090 if:

[0534] a) At least one ProSe identifier for the 5G ProSe direct link meets the privacy requirements specified in clause 5.2.4; or

[0535] b) T5090 is configured as specified in clause 5.2.5.

[0536] In addition, the initiating UE may perform PC5 QoS flow establishment on the 5G ProSe direct link as specified in clause 7.2.7.

[0537] After timer T5080 expires, if the ProSe direct link establishment request message does not contain the target user information IE and the initiating UE receives at least one ProSe direct link establishment accept message, then the UE implementation shall consider the 5G ProSe direct link establishment procedure as completed or restart timer T5080.

[0538] If the 5G ProSe direct link establishment procedure is triggered by a ProSe direct link modification request message from the source 5G ProSe layer 3 UE, as specified in clause 7.2.3.2, then in the case where the initiating UE acts as an intermediate UE between 5G ProSe layer 3 UEs, after receiving the ProSe direct link establishment accept message, the initiating UE shall send a ProSe direct link modification accept message to the source 5G ProSe layer 3 UE, as specified in clause 7.2.3.3.

[0539] 7.2.2.5 5G ProSe direct link establishment procedure not accepted by the target UE

[0540] If the ProSe direct link establishment request message cannot be accepted, the target UE shall send a ProSe direct link establishment reject message. The ProSe direct link establishment reject message contains a PC5 signaling protocol cause IE with the cause value set to one of the following:

[0541] #1 Direct communication with the target UE is not allowed;

[0542] #3 Conflict of layer 2 ID detected for unicast communication;

[0543] #5 Lack of resources for the 5G ProSe direct link;

[0544] #13 Congestion situation;

[0545] #15 Security procedure failure for 5G ProSe UE to network relay;

[0546] #20 Fault from the UE at the 5G ProSe side; or

[0547] #111 Unspecified protocol error.

[0548] If the target UE is not allowed to accept a ProSe direct link establishment request message, e.g., based on operator policy or configuration parameters for ProSe direct communication on PC5 as specified in clause 5.2, or the target UE acts as a 5G ProSe layer 3 UE to network relay UE in a non - allowed area of its serving PLMN and the corresponding relay service code is not associated with high - priority access as defined in clause 5.3.5 of 3GPP TS24.501

[11] , then the target UE shall send a ProSe direct link establishment rejection message containing the PC5 signalling protocol cause value #1 "Direct communication with the target UE not allowed".

[0549] Note 1: When a target UE acting as a 5G ProSe layer 3 UE to network relay UE is involved in its own emergency service as specified in 3GPP TS24.501

[11] or handling the emergency service of another 5G ProSe layer 3 remote UE, and receives a ProSe direct link establishment request message with an RSC specific to the emergency service, if the target UE decides to prioritize its own ongoing emergency service or the emergency service of other 5G ProSe layer 3 remote UE due to local regulations or implementation - specific requirements, then the target UE is allowed to ignore the ProSe direct link establishment request message.

[0550] For a ProSe direct link establishment request message received from a layer 2 ID (for unicast communication), if the target UE has already established an existing link to the UE using this layer 2 ID or is currently processing a ProSe direct link establishment request message from the same layer 2 ID and one of the following parameters is different from the existing link or the link for which the link establishment is in progress:

[0551] a) Source user information;

[0552] b) Type of data (e.g., IP, Ethernet or unstructured); or

[0553] c) Security policy,

[0554] The target UE shall send a PROSE direct link establishment rejection message containing the PC5 signalling protocol cause value #3 "Conflict detected for layer 2 ID for unicast communication".

[0555] Note 2: If the UE is processing ProSe direct discovery messages with the same source layer 2 ID as the received ProSe direct link establishment request message, then avoiding destination layer 2 ID conflicts depends on the UE implementation (e.g., sending a ProSe direct link establishment rejection message containing the PC5 signaling protocol cause value #3 "Conflict of layer 2 ID detected for unicast communication" or ignoring the ProSe direct discovery message).

[0556] Note 3: The type of data (e.g., IP, Ethernet, or unstructured) is indicated by the optional IP address configuration IE included in the corresponding direct link security mode complete message, i.e., if this IE is included, then the type of data for the requested link is of IP type, and if this IE is not included, then the type of data for the requested link is Ethernet or unstructured.

[0557] If the 5G ProSe direct link establishment fails due to reaching the implementation-specific maximum number of established 5G ProSe direct links or other temporary lower layer problems causing resource constraints, then the target UE shall send a ProSe direct link establishment rejection message containing the PC5 signaling protocol cause value #5 "Lack of resources for 5G ProSe direct link".

[0558] […]

[0559] If the 5G ProSe direct link establishment request is for 5G ProSe UE-to-UE relay and:

[0560] a) The target UE acting as the target 5G ProSe end UE is under congestion;

[0561] The target UE shall send a ProSe direct link establishment rejection message containing the PC5 signaling protocol cause value #13 "Congestion situation". The target UE may provide a backoff timer value to the initiating UE in the ProSe direct link establishment rejection message.

[0562] After receiving a ProSe direct link establishment rejection message from the target 5G ProSe end UE, the initiating UE acts as a 5G ProSe UE - to - UE relay UE, and the 5G ProSe direct link establishment procedure is used for direct communication between the source 5G ProSe end UE and the 5G ProSe UE - to - UE relay UE. The target 5G ProSe end UE has rejected the 5G ProSe direct link establishment procedure or the 5G ProSe direct link modification procedure. The rejection message contains a back - off value. The initiating UE has not reached the maximum number of allowed re - transmissions. The initiating UE will notify (message TBD) the source 5G ProSe end UE that the target 5G ProSe end UE has rejected the link establishment or link modification request and will provide the cause value from the target 5G ProSe end UE.

[0563] Editor's note: How the target 5G ProSe end UE notifies the 5G ProSe UE - to - UE relay UE that has rejected the link establishment or link modification request remains to be further studied.

[0564] After receiving a ProSe direct link establishment rejection message from the target 5G ProSe end UE, the initiating UE acts as a 5G ProSe UE - to - UE relay UE. The 5G ProSe direct link establishment procedure is used for direct communication between the source 5G ProSe end UE and the 5G ProSe UE - to - UE relay UE. The target 5G ProSe end UE has rejected the 5G ProSe direct link establishment procedure or the 5G ProSe direct link modification procedure. The rejection message contains a back - off value, and the initiating UE has reached the maximum number of allowed re - transmissions. The initiating UE may send a ProSe direct link establishment rejection message with an appropriate PC5 signaling protocol cause value to the source 5G ProSe end UE. The initiating UE will include the PC5 protocol cause value #xx "Failure from 5G ProSe end UE" in the ProSe direct link establishment rejection message and include the PC5 end UE failure cause IE set to #13 "Congestion situation" received from the target 5G ProSe end UE that has rejected the 5G ProSe direct link establishment or 5G ProSe direct link modification procedure. The initiating UE may include the target end UE information IE set to the user information ID of the target 5G ProSe end UE in the ProSe direct link establishment rejection message.

[0565] If the 5G ProSe direct link establishment request is for 5G ProSe UE - to - UE relay and:

[0566] a) The target UE acting as a 5G ProSe UE - to - UE relay UE is under congestion;

[0567] The target UE will send a ProSe direct link establishment rejection message containing the PC5 signaling protocol cause value #13 "congestion situation". The target UE may provide a backoff timer value to the initiating UE in the ProSe direct link establishment rejection message.

[0568] […]

[0569] If the target UE acts as the target 5G ProSe end UE and the 5G ProSe direct link establishment procedure is between the 5G ProSe UE - to - UE relay UE and the target 5G ProSe end UE, then the target 5G ProSe end UE may include the following in the ProSe direct link establishment rejection message:

[0570] a) A source end UE information IE set to the user information ID of the source 5G ProSe end UE;

[0571] b) A target end UE information IE set to the user information ID of the target 5G ProSe end UE; and

[0572] c) A UE - to - UE relay UE information IE set to the user information ID of the 5G ProSe UE - to - UE relay UE.

[0573] If the target UE acts as the 5G ProSe UE - to - UE relay UE, the 5G ProSe direct link establishment procedure is between the source 5G ProSe end UE and the 5G ProSe UE - to - UE relay UE, and the target 5G ProSe end UE has rejected the 5G ProSe direct link establishment procedure or the 5G ProSe direct link modification procedure, then the 5G ProSe UE - to - UE relay UE will send a ProSe direct link establishment rejection message with the PC5 signaling protocol cause value #20 "failure from 5G ProSe end UE" to the source 5G ProSe end UE. The 5G ProSe UE - to - UE relay UE may include a PC5 end UE failure cause IE in the ProSe direct link establishment rejection message, which is set to the PC5 signaling protocol cause received from the target 5G ProSe end UE that has rejected the 5G ProSe direct link establishment procedure. The 5G ProSe UE - to - UE relay UE may include the following in the ProSe direct link establishment rejection message:

[0574] a) A source end UE information IE set to the user information ID of the source 5G ProSe end UE;

[0575] b) A target end UE information IE set to the user information ID of the target 5G ProSe end UE; and

[0576] c) UE - to - UE Relay UE information IE that is set as the user information ID of the 5G ProSe UE - to - UE Relay UE.

[0577] […]

[0578] If the establishment of the 5G ProSe direct link fails for other reasons, the target UE will send a ProSe direct link establishment rejection message containing the PC5 signaling protocol cause value #111 "Unspecified protocol error".

[0579] After sending the ProSe direct link establishment rejection message, the target UE will provide the following information to the lower layer, along with the layer 2 ID of the initiating UE for unicast communication and the layer 2 ID of the target UE for unicast communication:

[0580] a) Indication of the de - activation of PC5 unicast security protection and deletion of the security context for the 5G ProSe direct link (if applicable).

[0581] After receiving the ProSe direct link establishment rejection message, the initiating UE will stop timer T5080 and abort the 5G ProSe direct link establishment procedure. If the PC5 signaling protocol cause value in the ProSe direct link establishment rejection message is #1 "Direct communication with the target UE is not allowed" or #5 "Lack of resources for the 5G ProSe direct link", the initiating UE should not attempt to initiate the 5G ProSe direct link establishment procedure with the same target UE for at least a time period T. If the PC5 signaling protocol cause value in the ProSe direct link establishment rejection message is #13 "Congestion situation", and the ProSe direct link establishment rejection message provides a back - off timer value, the initiating UE shall start timer T5088 associated with the layer 2 ID of the target UE and set its value to the provided timer value.....

[0582] 7.2.3 5G ProSe Direct Link Modification Procedure

[0583] 7.2.3.1 Overview

[0584] The purpose of the 5G ProSe direct link modification procedure is to modify an existing ProSe direct link to:

[0585] a) Add a new PC5 QoS flow to the existing 5G ProSe direct link;

[0586] b) Modify an existing PC5 QoS flow to update the PC5 QoS parameters of the existing PC5 QoS flow;

[0587] c) Modify an existing PC5 QoS flow to associate a new ProSe application with the existing PC5 QoS flow;

[0588] d) Modify the existing PC5 QoS flow to remove the associated ProSe application from the existing PC5 QoS flow;

[0589] e) Remove the existing PC5 QoS flow from the existing 5G ProSe direct link;

[0590] f) Negotiate a new 5G ProSe UE - to - UE relay UE on the existing 5G ProSe direct link;

[0591] g) Establish 5G ProSe UE - to - UE relay communication with an additional 5G ProSe layer 3 source UE using the existing 5G ProSe direct link between the 5G ProSe layer 3 source UE and the 5G ProSe layer 3 UE - to - UE relay UE; or

[0592] h) Release 5G ProSe UE - to - UE relay communication with one of the peer 5G ProSe layer 3 source UEs using the shared 5G ProSe direct link between the 5G ProSe layer 3 source UE and the 5G ProSe layer 3 UE - to - UE relay UE.

[0593] In this procedure, the UE that sends the ProSe direct link modification request message is called the "initiating UE", and the other UE is called the "target UE".

[0594] Note: The 5G ProSe direct link modification procedure does not apply to the case of 5G ProSe layer 2 UE - to - network relay.

[0595] 7.2.3.2 5G ProSe direct link modification procedure initiated by the initiating UE

[0596] Before initiating this procedure to add a new ProSe application to an existing 5G ProSe direct link, the initiating UE shall meet the following pre - conditions:

[0597] a) There is a 5G ProSe direct link between the initiating UE and the target UE;

[0598] b) The pair of application layer ID and network layer protocol of this 5G ProSe direct link are the same as those required by the application layer in the initiating UE of this ProSe application;

[0599] c) The security policy corresponding to the ProSe identifier is consistent with the security policy of the existing 5G ProSe direct link;

[0600] d) Timer T5091 is not running; and

[0601] e) The initiating UE does not execute the 5G ProSe direct link key update procedure initiated by the target UE.

[0602] Before initiating this procedure for negotiating a new 5G ProSe UE - to - UE relay UE on an existing 5G ProSe direct link, the initiating UE shall meet the following prerequisites:

[0603] a) The initiating UE is the source 5G ProSe end - UE communicating with the target 5G ProSe end - UE via a 5G ProSe UE - to - UE relay UE;

[0604] b) The initiating UE determines to perform UE - to - UE relay reselection, for example, based on the PC5 signal strength; and

[0605] c) The initiating UE obtains a list of candidate UE - to - UE relays via the UE - to - UE discovery procedure.

[0606] After receiving service data or a request from the upper layer, the initiating UE shall perform PC5 QoS flow matching as specified in Clause 7.2.8. If there is no matching PC5 QoS flow, then the initiating UE shall derive PC5 QoS parameters and assign a PQFI for the PC5 QoS flow to be established, as specified in Clause 7.2.7.

[0607] If the 5G ProSe direct link modification procedure is to add a new PC5 QoS flow to an existing 5G ProSe direct link, then the initiating UE shall create a ProSe direct link modification request message. In this message, the initiating UE:

[0608] a) Shall include the PQFI, the corresponding PC5 QoS parameters, and an optional ProSe identifier;

[0609] b) Shall include a link modification operation code set to "Add a new PC5 QoS flow to an existing 5G ProSe direct link";

[0610] c) May include PC5 QoS rules to indicate the packet filters for the PC5 QoS flow;

[0611] d) Shall include the source end - UE information set to the user information ID of the source 5G ProSe layer 3 end - UE if the UE acts as a 5G ProSe layer 3 UE - to - UE relay UE, the 5G ProSe direct link is between the 5G ProSe layer 3 UE - to - UE relay UE and the target 5G ProSe layer 3 end - UE, and multiple source 5G ProSe layer 3 end - UEs have established direct communication with the target 5G ProSe layer 3 end - UE via the same 5G ProSe direct link through the 5G ProSe layer 3 UE - to - UE relay UE;

[0612] e) may include source UE information with the user information ID set as the source 5G ProSe end UE, if the UE acts as an intermediate UE between 5G ProSe UEs, the 5G ProSe direct link is between the intermediate UE between 5G ProSe UEs and the target 5G ProSe end UE, and only one source 5G ProSe end UE has established direct communication with the target 5G ProSe end UE via the intermediate UE between 5G ProSe UEs using the 5G ProSe direct link;

[0613] f) will include target UE information with the user information ID set as the target 5G ProSe layer 3 end UE, if the UE acts as the source 5G ProSe layer 3 end UE, the 5G ProSe direct link is between the source 5G ProSe layer 3 end UE and the intermediate UE between 5G ProSe layer 3 UEs, and the source 5G ProSe layer 3 end UE has established direct communication with multiple target 5G ProSe layer 3 end UEs via the intermediate UE between 5G ProSe layer 3 UEs using the same 5G ProSe direct link;

[0614] g) may include target UE information with the user information ID set as the target 5G ProSe end UE, provided that:

[0615] 1) the UE acts as the source 5G ProSe end UE, the 5G ProSe direct link is between the source 5G ProSe end UE and the intermediate UE between 5G ProSe UEs, and the source 5G ProSe end UE has established direct communication with only one target 5G ProSe end UE via the intermediate UE between 5G ProSe UEs using the 5G ProSe direct link; or

[0616] 2) the UE acts as an intermediate UE between 5G ProSe UEs and the 5G ProSe direct link is between the intermediate UE between 5G ProSe UEs and the target 5G ProSe end UE; and

[0617] h) may include the target UE layer 2 ID with the layer 2 ID set as the target 5G ProSe end UE, if the UE acts as the source 5G ProSe end UE and the 5G ProSe direct link is between the source 5G ProSe end UE and the intermediate UE between 5G ProSe UEs.

[0618] If the 5G ProSe direct link modification procedure is to modify the PC5 QoS parameters of the existing PC5 QoS flow in the existing 5G ProSe direct link, the initiating UE will create a ProSe direct link modification request message. In this message, the initiating UE:

[0619] a) It will contain the PQFI and corresponding PC5 QoS parameters, including the ProSe identifier;

[0620] b) It will contain a link modification operation code set to "Modify the PC5 QoS parameters of an existing PC5 QoS flow";

[0621] c) It may contain PC5 QoS rules to indicate the packet filter of the PC5 QoS flow;

[0622] d) It will contain source UE information set to the user information ID of the source 5G ProSe layer 3 end UE. If the UE acts as a 5G ProSe layer 3 UE - to - UE relay UE, the 5G ProSe direct link is between the 5G ProSe layer 3 UE - to - UE relay UE and the target 5G ProSe layer 3 end UE, and multiple source 5G ProSe layer 3 end UEs have established direct communication with the target 5G ProSe layer 3 end UE via the 5G ProSe layer 3 UE - to - UE relay UE using the same 5G ProSe direct link;

[0623] e) It may contain source UE information set to the user information ID of the source 5G ProSe end UE. If the UE acts as a 5G ProSe UE - to - UE relay UE, the 5G ProSe direct link is between the 5G ProSe UE - to - UE relay UE and the target 5G ProSe end UE, and only one source 5G ProSe end UE has established direct communication with the target 5G ProSe end UE via the 5G ProSe UE - to - UE relay UE using the 5G ProSe direct link;

[0624] f) It will contain target UE information set to the user information ID of the target 5G ProSe layer 3 end UE. If the UE acts as a source 5G ProSe layer 3 end UE, the 5G ProSe direct link is between the source 5G ProSe layer 3 end UE and the 5G ProSe layer 3 UE - to - UE relay UE, and the source 5G ProSe layer 3 end UE has established direct communication with multiple target 5G ProSe layer 3 end UEs via the 5G ProSe layer 3 UE - to - UE relay UE using the same 5G ProSe direct link;

[0625] g) It may contain target UE information set to the user information ID of the target 5G ProSe end UE, provided that:

[0626] 1) The UE acts as a source 5G ProSe end UE. The 5G ProSe direct link is between the source 5G ProSe end UE and the 5G ProSe UE - to - UE relay UE, and the source 5G ProSe end UE has established direct communication with only one target 5G ProSe end UE via the 5G ProSe UE - to - UE relay UE using the 5G ProSe direct link; or

[0627] 2) The UE acts as a 5G ProSe UE - to - UE relay UE and the 5G ProSe direct link is between the 5G ProSe UE - to - UE relay UE and the target 5G ProSe end UE; and

[0628] h) May include a target end UE layer 2 ID set as the destination layer 2 ID of the target 5G ProSe end UE if the UE acts as a source 5G ProSe end UE and the 5G ProSe direct link is between the source 5G ProSe end UE and the 5G ProSe UE - to - UE relay UE.

[0629] If the 5G ProSe direct link modification procedure is to associate a new ProSe application with an existing PC5 QoS flow, the initiating UE will create a ProSe direct link modification request message. In this message, the initiating UE:

[0630] a) Will include the PQFI and corresponding PC5 QoS parameters, including the ProSe identifier;

[0631] b) Will include a link modification operation code set to "associate a new ProSe application with an existing PC5 QoS flow";

[0632] c) May include PC5 QoS rules to indicate the packet filter of the PC5 QoS flow;

[0633] d) Will include the source end UE information set as the user information ID of the source 5G ProSe layer 3 end UE if the UE acts as a 5G ProSe layer 3 UE - to - UE relay UE, the 5G ProSe direct link is between the 5G ProSe layer 3 UE - to - UE relay UE and the target 5G ProSe layer 3 end UE, and multiple source 5G ProSe layer 3 end UEs have established direct communication with the target 5G ProSe layer 3 end UE using the same 5G ProSe direct link via the 5G ProSe layer 3 UE - to - UE relay UE;

[0634] e) may include source UE information with the user information ID set to the source 5G ProSe end UE. If the UE acts as an intermediate UE between 5G ProSe UEs, the 5G ProSe direct link is between the intermediate UE between 5G ProSe UEs and the target 5G ProSe end UE, and only one source 5G ProSe end UE has established direct communication with the target 5G ProSe end UE via the intermediate UE between 5G ProSe UEs using the 5G ProSe direct link;

[0635] f) will include target UE information with the user information ID set to the target 5G ProSe layer 3 end UE. If the UE acts as the source 5G ProSe layer 3 end UE, the 5G ProSe direct link is between the source 5G ProSe layer 3 end UE and the intermediate UE between 5G ProSe layer 3 UEs, and the source 5G ProSe layer 3 end UE has established direct communication with multiple target 5G ProSe layer 3 end UEs via the intermediate UE between 5G ProSe layer 3 UEs using the same 5G ProSe direct link;

[0636] g) may include target UE information with the user information ID set to the target 5G ProSe end UE, provided that:

[0637] 1) The UE acts as the source 5G ProSe end UE, the 5G ProSe direct link is between the source 5G ProSe end UE and the intermediate UE between 5G ProSe UEs, and the source 5G ProSe end UE has established direct communication with only one target 5G ProSe end UE via the intermediate UE between 5G ProSe UEs using the 5G ProSe direct link; or

[0638] 2) The UE acts as an intermediate UE between 5G ProSe UEs and the 5G ProSe direct link is between the intermediate UE between 5G ProSe UEs and the target 5G ProSe end UE; and

[0639] h) may include the target UE layer 2 ID with the layer 2 ID set to the target 5G ProSe end UE if the UE acts as the source 5G ProSe end UE and the 5G ProSe direct link is between the source 5G ProSe end UE and the intermediate UE between 5G ProSe UEs.

[0640] If the PC5 5G ProSe direct link modification procedure removes the associated ProSe application from the existing PC5 QoS flow, the initiating UE will create a ProSe direct link modification request message. In this message, the initiating UE:

[0641] a) will include the PQFI and the corresponding PC5 QoS parameters, including the ProSe identifier; and

[0642] b) will include a link modification operation code set to "Remove ProSe application from the existing PC5 QoS flow".

[0643] If the direct link modification procedure removes any PC5 QoS flow from the existing 5G ProSe direct link, the initiating UE will create a ProSe direct link modification request message. In this message, the initiating UE:

[0644] a) will include the PQFI; and

[0645] b) will include a link modification operation code set to "Remove the existing PC5 QoS flow from the existing 5G ProSe direct link".

[0646] If the 5G ProSe direct link modification procedure is to establish 5G ProSe UE - to - UE relay communication with an additional 5G ProSe layer 3 - end UE using the existing 5G ProSe direct link between the 5G ProSe layer 3 - end UE and the relay UE between 5G ProSe layer 3 UEs, the initiating UE will create a ProSe direct link modification request message. In this message, the initiating UE:

[0647] a) will include the source - end UE information set to the source user information ID of the 5G ProSe layer 3 - end UE received in the ProSe direct link establishment request message, if the UE acts as a relay UE between 5G ProSe layer 3 UEs and the 5G ProSe direct link is between the relay UE between 5G ProSe layer 3 UEs and the target 5G ProSe layer 3 - end UE;

[0648] b) for Ethernet services, will include the MAC address of the source 5G ProSe layer 3 - end UE, if the UE acts as a relay UE between 5G ProSe layer 3 UEs and the 5G ProSe direct link is between the relay UE between 5G ProSe layer 3 UEs and the target 5G ProSe layer 3 - end UE;

[0649] c) will include the target - end UE information set to the user information ID of the additional target 5G ProSe layer 3 - end UE to which 5G ProSe UE - to - UE relay communication is requested, if the UE acts as the source 5G ProSe layer 3 - end UE and the 5G ProSe direct link is between the source 5G ProSe layer 3 - end UE and the relay UE between 5G ProSe layer 3 UEs;

[0650] d) The ProSe identifier that is included and is received from the upper layer when the UE acts as the source 5G ProSe layer 3 end UE or is set to be received in the ProSe direct link establishment request message when the UE acts as a 5G ProSe layer 3 UE - to - UE relay UE;

[0651] Editor's note: Whether to include the PQFI and the corresponding PC5 QoS parameter containing the ProSe identifier instead of only including the ProSe identifier remains to be further studied.

[0652] Editor's note: Whether to include and how to set the ProSe identifier for the 5G ProSe direct link between the source 5G ProSe layer 3 end UE and the 5G ProSe layer 3 UE - to - UE relay UE and for the 5G ProSe direct link between the 5G ProSe layer 3 UE - to - UE relay UE and the target 5G ProSe layer 3 end UE remains to be further studied.

[0653] e) Include the link modification operation code set to "Add a new 5G ProSe layer 3 end UE to the existing 5G ProSe direct link"; and

[0654] f) May include the target end UE layer 2 ID set to the layer 2 ID of the target 5G ProSe layer 3 end UE if the UE acts as the source 5G ProSe layer 3 end UE and the 5G ProSe direct link is between the source 5G ProSe layer 3 end UE and the 5G ProSe layer 3 UE - to - UE relay UE.

[0655] If the 5G ProSe direct link modification procedure is to use the shared 5G ProSe direct link between the 5G ProSe layer 3 end UE and the 5G ProSe layer 3 UE - to - UE relay UE to release the 5G ProSe UE - to - UE relay communication with the peer 5G ProSe layer 3 end UE, then the initiating UE will create a ProSe direct link modification request message. In this message, the initiating UE:

[0656] a) Include the source end UE information with the source user information ID of the 5G ProSe layer 3 end UE set to be received in the ProSe direct link release request message if the UE acts as a 5G ProSe layer 3 UE - to - UE relay UE and the 5G ProSe direct link is between the 5G ProSe layer 3 UE - to - UE relay UE and the 5G ProSe layer 3 end UE;

[0657] b) The target UE information containing the user information ID of the peer 5G ProSe layer 3 end UE that is set to release the 5G ProSe UE-to-UE relay communication therebetween, if the UE acts as a 5G ProSe layer 3 end UE and the 5G ProSe direct link is between the 5G ProSe layer 3 end UE and the 5G ProSe UE-to-UE relay UE; and

[0658] c) The link modification operation code containing the setting of "removing the 5G ProSe layer 3 end UE from the existing 5G ProSe direct link".

[0659] If the 5G ProSe direct link modification procedure is to trigger UE-to-UE relay reselection, the initiating UE will create a ProSe direct link modification request message. In this message:

[0660] 1) If the initiating UE acts as the source 5G ProSe end UE and the 5G ProSe direct link is between the source 5G ProSe end UE and the 5G ProSe UE-to-UE relay UE, then the initiating UE:

[0661] a) Will contain a relay reselection indication;

[0662] b) Will contain a list of candidate 5G ProSe UE-to-UE relay UE user information IDs;

[0663] c) If using IP communication, will contain a list of the target 5G ProSe end UE IP addresses / prefixes; and

[0664] d) May contain a list of candidate 5G ProSe UE-to-UE relay UE layer 2 IDs.

[0665] 2) If the initiating UE acts as a 5G ProSe UE-to-UE relay UE and the 5G ProSe direct link is between the 5G ProSe UE-to-UE relay UE and the target 5G ProSe end UE, then the initiating UE:

[0666] a) Will contain a relay reselection indication;

[0667] b) Will contain a list of candidate 5G ProSe UE-to-UE relay UE user information IDs;

[0668] c) If using IP communication, will contain the initiating source 5G ProSe UE IP address / prefix; and

[0669] d) May contain a list of candidate 5G ProSe UE-to-UE relay UE layer 2 IDs.

[0670] Editor's note: The PROSE direct link modification request message needs to be updated.

[0671] If the 5G ProSe direct link modification procedure is to trigger relay reselection and the initiating UE acts as a 5G ProSe UE - to - UE relay UE, then the initiating UE shall create a ProSe direct link modification request message for each IP address / prefix of the target 5G ProSe UE received from the 5G ProSe source UE on the associated ProSe direct link modification request message.

[0672] After the ProSe direct link modification request message is generated, the initiating UE shall pass this message, together with the layer 2 ID of the initiating UE for 5G ProSe direct communication and the layer 2 ID of the target UE for 5G ProSe direct communication, to the lower layer for transmission and start timer T5081. While timer T5081 is running, the UE shall not send a new ProSe direct link modification request message to the same target UE.

[0673] [[The heading of 3GPP TS24.554 V18.1.0 is "5G ProSe direct link modification procedure"]] Figure 7 .2.3.2.1 is reproduced as Figure 18

[0674] [[The heading of 3GPP TS24.554 V18.1.0 is "5G ProSe direct link modification procedure for layer 3 UE - to - UE relay reselection"]] Figure 7 .2.3.2.2 is reproduced as Figure 19

[0675] 7.2.3.3 5G ProSe direct link modification procedure accepted by the target UE

[0676] If the ProSe direct link modification request message is accepted, the target UE shall respond with a ProSe direct link modification acceptance message.

[0677] If the ProSe direct link modification request message is to add a new ProSe application, then add a new PC5 QoS flow or modify any existing PC5 QoS flow in the 5G ProSe direct link, the target UE:

[0678] a) shall include the PQFI, the corresponding PC5 QoS parameters, and optionally the ProSe identifier accepted by the target UE;

[0679] b) may include a PC5 QoS rule for indicating the packet filter of the PC5 QoS flow;

[0680] ​​c) Source UE information including the user information ID set as the source 5G ProSe layer 3 end UE, if the UE acts as the target 5G ProSe layer 3 end UE, the 5G ProSe direct link is between the relay UE between 5G ProSe layer 3 UEs and the target 5G ProSe layer 3 end UE, and the target 5G ProSe layer 3 end UE has established direct communication with multiple source 5G ProSe layer 3 end UEs using the same 5G ProSe direct link by the relay UE between 5G ProSe layer 3 UEs; and

[0681] d) Source UE information that may include the user information ID set as the source 5G ProSe end UE, if the UE acts as the target 5G ProSe end UE, the 5G ProSe direct link is between the relay UE between 5G ProSe UEs and the target 5G ProSe end UE, and the target 5G ProSe end UE has established direct communication with only one source 5G ProSe end UE using the 5G ProSe direct link by the relay UE between 5G ProSe UEs; and

[0682] e) Target UE information including the user information ID set as the target 5G ProSe end UE, if the UE acts as the relay UE between 5G ProSe UEs, the 5G ProSe direct link is between the source 5G ProSe end UE and the relay UE between 5G ProSe UEs, and the source 5G ProSe layer 3 end UE has established direct communication with multiple target 5G ProSe layer 3 end UEs using the same 5G ProSe direct link by the relay UE between 5G ProSe layer 3 UEs;

[0683] f) Target UE information that may include the user information ID set as the target 5G ProSe end UE, if the UE acts as the relay UE between 5G ProSe UEs, the 5G ProSe direct link is between the source 5G ProSe end UE and the relay UE between 5G ProSe UEs, and the source 5G ProSe end UE has established direct communication with only one target 5G ProSe end UE using the 5G ProSe direct link by the relay UE between 5G ProSe UEs;

[0684] In the ProSe direct link modification acceptance message.

[0685] If the ProSe direct link modification request message is to remove an existing ProSe application from the 5G ProSe direct link, then the target UE shall delete the ProSe identifier received in the ProSe direct link modification request message and the corresponding PQFI and PC5 QoS parameters from the attribute set associated with the 5G ProSe direct link.

[0686] If the ProSe direct link modification request message removes an existing PC5 QoS flow from the PC5 5G ProSe direct link, the target UE shall delete the PQFI and the corresponding PC5 QoS parameters from the set of attributes associated with the 5G ProSe direct link.

[0687] If the ProSe direct link modification request message adds a new ProSe application, adds a new PC5 QoS flow, or modifies any existing PC5 QoS flow in the 5G ProSe direct link, after sending the ProSe direct link modification acceptance message, the target UE shall provide the added or modified PQFI and the corresponding PC5 QoS parameters, as well as the PC5 link identifier, to the lower layer.

[0688] After sending the ProSe direct link modification acceptance message, if the ProSe direct link modification request message removes an existing ProSe application or removes an existing PC5 QoS flow from the 5G ProSe direct link, the target UE shall provide the removed PQFI and the PC5 link identifier to the lower layer.

[0689] If the ProSe direct link modification request message establishes 5G ProSe UE - to - UE relay communication between an additional 5G ProSe layer 3 - end UE using an existing 5G ProSe direct link between the 5G ProSe layer 3 - end UE and the 5G ProSe layer 3 - UE - to - UE relay UE, the target UE:

[0690] a) If acting as the 5G ProSe layer 3 - UE - to - UE relay UE, shall perform the 5G ProSe direct link establishment procedure towards the target 5G ProSe layer 3 - end UE as specified in Clause 7.2.2.2; and after receiving the ProSe direct link establishment acceptance message from the target 5G ProSe layer 3 - end UE, shall create a ProSe direct link modification acceptance message;

[0691] b) If acting as the target 5G ProSe layer 3 - end UE, shall create a ProSe direct link modification acceptance message; and

[0692] c) In the ProSe direct link modification acceptance message, the target UE:

[0693] 1) If the UE acts as the target 5G ProSe layer 3 - end UE, shall include the source UE information with the user information ID set to the source 5G ProSe layer 3 - end UE; or

[0694] 2) If the UE acts as the 5G ProSe layer 3 - UE - to - UE relay UE:

[0695] i) The target UE information including the user information ID of the target 5G ProSe layer 3 side UE set;

[0696] ii) For IP services, it may include the target 5G ProSe layer 3 side UE IP address IE with the IP address of the additional target 5G ProSe layer 3 side UE set; and

[0697] iii) For Ethernet services, it will include the MAC address of the target 5G ProSe layer 3 side UE.

[0698] If the ProSe direct link modification request message is for 5G ProSe UE - to - UE relay communication between the 5G ProSe layer 3 side UE and one of the peer 5G ProSe layer 3 side UEs using the shared 5G ProSe direct link release between the 5G ProSe layer 3 side UE and the relay UE between 5G ProSe layer 3 UEs, then the target UE:

[0699] a) If acting as a relay UE between 5G ProSe layer 3 UEs, it may initiate one of the following procedures towards the target 5G ProSe layer 3 side UE:

[0700] 1) The 5G ProSe direct link release procedure, as specified in Clause 7.2.6.2, for releasing the 5G ProSe direct link with the peer 5G ProSe layer 3 side UE; or

[0701] 2) The 5G ProSe direct link modification procedure, as specified in Clause 7.2.3.2, for removing the corresponding PC5 QoS flow, provided that the UE determines to maintain the 5G ProSe direct link with the peer 5G ProSe layer 3 side UE; and

[0702] b) It will create a ProSe direct link modification acceptance message, and in this message, the target UE:

[0703] 1) If the UE acts as the target 5G ProSe layer 3 side UE, it will include the source UE information with the user information ID of the source 5G ProSe layer 3 side UE set; or

[0704] 2) If the UE acts as a relay UE between 5G ProSe layer 3 UEs, it will include the target UE information with the user information ID of the target 5G ProSe layer 3 side UE set.

[0705] If the 5G ProSe direct link is for 5G ProSe direct communication between a 5G ProSe remote UE and a 5G ProSe layer 3 UE to network relay UE, and if the initiating UE is a 5G ProSe remote UE, then the target UE (as a 5G ProSe layer 3 UE to network relay UE) performs the QoS flow handling procedures as specified in Clause 8.2.6.3.3 and Clause 8.2.6.4.2.

[0706] If the ProSe direct link modification request message is for inter-UE relay UE reselection, then the target UE may perform the 5G ProSe inter-UE relay discovery procedure, where the user information ID of the candidate 5G ProSe inter-UE relay is in the discovery message, and may set the layer 2 ID of the candidate 5G ProSe inter-UE relay to the destination layer 2 ID to carry the discovery message, provided that it is received in the ProSe direct link modification request message.

[0707] If the ProSe direct link modification request message is accepted to trigger inter-UE relay reselection, then the target UE will establish a PC5 unicast link with the selected 5G ProSe inter-UE relay UE (if such a PC5 unicast link does not already exist), and the 5G ProSe direct link is between the target 5G ProSe end UE and the 5G ProSe inter-UE relay UE.

[0708] If the ProSe direct link modification request message is accepted to trigger relay reselection, then the target UE will respond with a ProSe direct link modification acceptance message. In this message:

[0709] 1) If the target UE acts as a target 5G ProSe end UE, and the 5G ProSe direct link is between the target 5G ProSe end UE and the 5G ProSe inter-UE relay UE, then the target UE:

[0710] a) will include a relay reselection indication;

[0711] b) will include the new 5G ProSe inter-UE relay UE user information ID;

[0712] c) will include the initiating 5G ProSe end UE IP address; and

[0713] d) if using IP communication, will include the target 5G ProSe end UE IP address to be used with the newly selected 5G ProSe inter-UE relay UE.

[0714] 2) If the target UE acts as a 5G ProSe UE - to - UE relay UE and the 5G ProSe direct link is between the 5G ProSe UE - to - UE relay UE and the source 5G ProSe UE - end UE, then the target UE.

[0715] a) will contain a relay reselection indication;

[0716] b) will contain a new 5G ProSe UE - to - UE relay UE user information ID;

[0717] c) will contain the target 5G ProSe UE - end UE IP address; and

[0718] d) if IP communication is used, will contain the target 5G ProSe UE - end UE IP address to be used with the newly selected 5G ProSe UE - to - UE relay UE.

[0719] Editor's note: The ProSe direct link modification acceptance message needs to be updated.

[0720] If the target UE accepts the 5G ProSe direct link modification request, then the target UE may perform PC5 QoS flow establishment on the 5G ProSe direct link as specified in Clause 7.2.7, and perform PC5 QoS flow matching on the 5G ProSe direct link as specified in Clause 7.2.8.

[0721] 7.2.3.4 5G ProSe direct link modification procedure completed by the initiating UE

[0722] After receiving the ProSe direct link modification acceptance message, the initiating UE will stop timer T5081.

[0723] After receiving the ProSe direct link modification acceptance message, if the ProSe direct link modification request message is to add a new ProSe application, add a new PC5 QoS flow, or modify any existing PC5 QoS flow in the 5G ProSe direct link, then the initiating UE shall provide the added or modified PQFI and the corresponding PC5 QoS parameters, as well as the PC5 link identifier, to the lower layer.

[0724] After receiving the ProSe direct link modification acceptance message, if the ProSe direct link modification request message is to remove an existing ProSe application or remove an existing PC5 QoS flow from the 5G ProSe direct link, then the initiating UE will provide the removed PQFI and the PC5 link identifier to the lower layer.

[0725] After receiving a ProSe direct link modification acceptance message, if the ProSe direct link modification request message is to establish ProSe UE - to - UE relay communication between an additional 5G ProSe layer 3 peer UE and a 5G ProSe layer 3 UE using an existing 5G ProSe direct link between a 5G ProSe layer 3 - end UE and a relay UE between 5G ProSe layer 3 UEs, then the initiating UE shall send a ProSe direct link establishment acceptance message to the source 5G ProSe layer 3 - end UE, as specified in clause 7.2.2.3, provided that the initiating UE acts as a relay UE between 5G ProSe layer 3 UEs.

[0726] […]

[0727] After receiving a ProSe direct link modification acceptance message containing a relay reselection indication, if the ProSe direct link modification request message is for layer 3 UE - to - UE relay reselection, then the initiating UE shall establish a PC5 unicast link (if such a PC5 unicast link does not already exist) with the selected relay UE between 5G ProSe UEs and shall create a ProSe direct link modification confirmation message. In this message, the initiating UE:

[0728] a) shall include the relay reselection indication, the IP address of the initiating 5G ProSe UE to be used with the newly selected relay UE between 5G ProSe UEs, and the IP address of the target 5G ProSe layer 3 - end UE, if IP communication is used, and if:

[0729] 1) the UE acts as a source 5G ProSe layer 3 - end UE and the 5G ProSe direct link is between the source 5G ProSe layer 3 - end UE and the relay UE between 5G ProSe layer 3 UEs; or

[0730] b) shall include the relay reselection indication, the IP address of the target 5G ProSe layer 3 - end UE to be used with the newly selected relay UE between 5G ProSe UEs, and the IP address of the source 5G ProSe layer 3 - end UE, if IP communication is used, and if:

[0731] 1) the UE acts as a relay UE between 5G ProSe UEs and the 5G ProSe direct link is between the relay UE between 5G ProSe UEs and the target 5G ProSe layer 3 - end UE.

[0732] After the ProSe direct link modification confirmation message is generated, the initiating UE shall pass this message, together with the layer 2 ID of the initiating UE for 5G ProSe direct communication and the layer 2 ID of the target UE for 5G ProSe direct communication, to the lower layer for transmission.

[0733] If the source UE confirms acceptance of the 5G ProSe direct link modification, the source UE starts receiving and / or transmitting traffic via the most recently selected 5G ProSe inter-UE relay UE.

[0734] 7.2.3.5 5G ProSe direct link modification procedure not accepted by the target UE

[0735] If the 5G ProSe direct link modification request cannot be accepted, the target UE shall send a ProSe direct link modification rejection message. The ProSe direct link modification rejection message contains a PC5 signaling protocol cause IE set to one of the following cause values:

[0736] #5 Lack of resources for the 5G ProSe direct link;

[0737] #6 Desired service not allowed;

[0738] #12 Security policy misalignment;

[0739] #16 Lack of local capabilities;

[0740] #20 Failure from the 5G ProSe end UE;

[0741] #yy Relay UE not selected for link establishment with integrated discovery; or

[0742] #111 Unspecified protocol error.

[0743] If the target UE acts as the target 5G ProSe end UE and the 5G ProSe direct link modification procedure is between the 5G ProSe inter-UE relay UE and the target 5G ProSe end UE, the target 5G ProSe end UE may include in the ProSe direct link modification rejection message a source UE information IE set to the user information ID of the source 5G ProSe end UE that initiated the 5G ProSe direct link establishment procedure.

[0744] If the target UE acts as a 5G ProSe UE - to - UE relay UE, the 5G ProSe direct link modification procedure is between the source 5G ProSe UE - end UE and the 5G ProSe UE - to - UE relay UE, and the target 5G ProSe UE - end UE has rejected the 5G ProSe direct link establishment procedure or the 5G ProSe direct link modification procedure, then the 5G ProSe UE - to - UE relay UE shall send a ProSe direct link modification rejection message with the PC5 signaling protocol cause value #20 "Failure from 5G ProSe UE - end UE" to the source 5G ProSe UE - end UE. The 5G ProSe UE - to - UE relay UE may include in the ProSe direct link modification rejection message a PC5 - end UE failure cause IE set to the PC5 signaling protocol cause received from the target 5G ProSe UE - end UE that has rejected the 5G ProSe direct link establishment procedure, as specified in Clause 7.2.2.5. The 5G ProSe UE - to - UE relay UE may include in the ProSe direct link modification rejection message a target - end UE information IE set to the user information ID of the target 5G ProSe UE - end UE that has rejected the 5G ProSe direct link establishment procedure.

[0745] […]

[0746] After receiving the ProSe direct link modification rejection message, the initiating UE shall stop timer T5081 and abort the 5G ProSe direct link modification procedure. If the PC5 signaling protocol cause value in the ProSe direct link modification rejection message is #11 "Required service not allowed" or #5 "Lack of resources for 5G ProSe direct link" or #12 "Security policy misalignment", then the initiating UE shall not attempt to initiate a 5G ProSe direct link modification to the same target UE to add the same ProSe application or add or modify the same PC5 QoS flow for at least a period of time T.

[0747] […]

[0748] 7.2.3.7 Completion of 5G ProSe direct link modification procedure by the target UE

[0749] After receiving the ProSe direct link modification confirmation, the target 5G ProSe UE - end UE starts to receive traffic, transmit traffic, or do both via the newly selected 5G ProSe UE - to - UE relay UE.

[0750] […]

[0751] 10.3.1 ProSe direct link establishment request

[0752] 10.3.1.1 Message definition

[0753] This message is sent by a UE to another peer UE to establish a direct link. See Table 10.3.1.1.1.

[0754] Message type: ProSe direct link establishment request

[0755] Importance: Dual

[0756] Direction: UE to peer UE

[0757] […]

[0758] 10.3.1.14 UE - to - UE relay UE user information

[0759] The UE shall include this IE in the following cases:

[0760] 1) The user information ID of the 5G ProSe UE - to - UE relay UE is obtained during the 5G ProSe UE - to - UE relay discovery procedure, and the 5G ProSe direct link establishment procedure is for 5G ProSe direct communication between the source 5G ProSe end UE and the 5G ProSe UE - to - UE relay UE; or

[0761] 2) The UE acts as a 5G ProSe UE - to - UE relay UE.

[0762] 10.3.1.15 Destination end UE layer 2 ID

[0763] If the destination end UE layer 2 ID is available to the source 5G ProSe end UE via a previous direct communication, and the 5G ProSe direct link establishment procedure is for 5G ProSe direct communication between the source 5G ProSe end UE and the 5G ProSe UE - to - UE relay UE, then the UE shall include this IE.

[0764] 10.3.2 ProSe direct link establishment acceptance

[0765] 10.3.2.1 Message definition

[0766] This message is sent by a UE to another peer UE to accept the received ProSe direct link establishment request message. See Table 10.3.2.1.1.

[0767] Message type: ProSe direct link establishment acceptance

[0768] Importance: Dual

[0769] […]

[0770] 10.3.2.6 UE - to - UE relay UE user information

[0771] If the 5G ProSe direct link establishment procedure is for 5G ProSe direct communication between a (source or target) 5G ProSe end UE and a relay UE among 5G ProSe UEs, the UE shall include this IE.

[0772] 10.3.2.7 Target 5G ProSe layer 3 end UE MAC address

[0773] The UE shall include this IE when it is necessary to indicate the MAC address of the target 5G ProSe layer 3 end UE.

[0774] The 3GPP TS 38.300 running CR for U2U relay (3GPP R2-2312029) introduced the following:

[0775] 16.12.x Control plane procedures for L2 U2U relay

[0776] The L2 U2U remote UE needs to establish an end-to-end SL-SRB / DRB with the peer L2 U2U remote UE before user plane data transfer.

[0777] Figure 16 .12.x-1 The following high-level connection establishment procedures apply to the L2 U2U relay UE and the L2U2U remote UE:

[0778] [The procedures titled "Procedures for L2 U2U remote UE connection establishment" in 3GPP R2-2312029 Figure 16 .12.x-1 are reproduced as Figure 20

[0779] 1. The L2 U2U remote UE, the L2 U2U relay UE, and the peer L2 U2U remote UE perform discovery procedures or integrated discovery procedures.

[0780] 2a. The L2 U2U remote UE establishes / modifies the PC5-RRC connection with the selected L2 U2U relay UE (i.e., as specified in TS23.304

[48] ).

[0781] 2b. The L2 U2U relay UE establishes / modifies the PC5-RRC connection with the peer L2 U2U remote UE (i.e., as specified in TS23.304

[48] ).

[0782] ​3. The L2 U2U relay UE allocates two local IDs, and the two local IDs are delivered to each of the L2 U2U remote UEs via the RRCReconfigurationSidelink message: one local ID is used to identify the L2 U2U remote UE, and the other local ID is used to identify the peer L2 U2U remote UE. When delivering the local IDs, the L2 ID of the peer L2U2U remote UE is also delivered to the U2U remote UE for associating between the local ID and the L2 ID of the peer U2U remote UE.

[0783] 4. The L2 U2U remote UE sends all QoS attribute sets for the end-to-end QoS flow to the L2 U2U relay UE via the PC5-RRC message.

[0784] 5. The L2 U2U relay UE performs QoS splitting at least for the PDB.

[0785] Note: How to split the PDB depends on the L2 U2U relay UE implementation.

[0786] 6. The L2 U2U relay UE sends the split QoS values (i.e., at least the PDB) to the L2 U2U remote UE via the PC5-RRC message.

[0787] Editor's note: Whether it is necessary to deliver the split QoS values to the peer L2 U2U remote UE remains to be further studied.

[0788] 7. The L2 U2U remote UE establishes an end-to-end PC5-RRC connection with the peer L2 U2U remote UE via the L2 U2U relay UE. The L2 U2U remote UE derives the PDCP and SDAP configurations for the end-to-end SL-DRB, and provides the received-related part of the configuration to the peer L2 U2U remote UE using the end-to-end PC5-RRC message. For end-to-end connection establishment, fixed indexes (i.e., 0 / 1 / 2 / 3) are defined respectively for the end-to-end SL-SRB 0 / 1 / 2 / 3, and the specified PC5 RLC channel configuration is used at each hop. The end-to-end bearer IDs for the SL-SRB and SL-DRB are used as inputs for encryption and decryption at the L2U2U relay at the PDCP.

[0789] 8a. The L2 U2U remote UE derives the configuration for the first hop for the SL-DRB (e.g., the PC5 relay RLC channel configuration), and provides the configuration related to reception at the first hop (i.e., Rx by the relay UE) to the L2 U2U relay UE using the per-hop RRCReconfigurationSidelink message

[0790] 8b. The L2 U2U relay UE derives the second-hop configuration (e.g., PC5 relay RLC channel configuration) for each SL-DRB and provides the configuration related to reception on the second hop (i.e., Rx by the peer remote UE) to the peer L2 U2U remote UE using each hop RRCReconfigurationSidelink message.

[0791] 9. The L2 U2U remote UE and the peer L2 U2U remote UE transmit or receive data via the L2 U2U relay UE.

[0792] The 3GPP TS 38.331 running CR (3GPP R2-2311934) for U2U relay describes the following:

[0793] 16.12.2.x Relay between L2 UEs

[0794] The protocol stacks for the user plane and the control plane for the L2 U2N relay architecture are described in Figure 16 .12.2.x-1 and Figure 16 .12.2.x-2. The SRAP sublayer is placed above the RLC sublayer for both CP and UP at the two PC5 interfaces. The sidelink SDAP, PDCP, and RRC terminate between the two L2 U2U remote UEs (i.e., end-to-end), while the SRAP, RLC, MAC, and PHY terminate in each hop-by-hop PC5 link.

[0795] [The [3GPP R2-2311934] titled "User Plane Protocol Stack for Relay between L2 UEs" Figure 16 .12.2.x-1 is reproduced as Figure 21

[0796] [The [3GPP R2-2311934] titled "Control Plane Protocol Stack for Relay between L2 UEs" Figure 16 .12.2.x-2 is reproduced as Figure 22

[0797] For relay between L2 UEs, the SRAP sublayer at the L2 U2U remote UE:

[0798] - The SRAP sublayer at the L2 U2U remote UE performs the bearer mapping between the end-to-end PC5 radio bearers (SL-SRB, SL-DRB) of the L2 U2U remote UE and the hop-by-hop PC5 relay RLC channels between the L2 U2U remote UE and the L2 U2U relay UE.

[0799] ​​- For the traffic transmitted from the L2 U2U remote UE to the L2 U2U relay UE, different end-to-end PC5 radio bearers (SL-SRB or SL-DRB) going to the same peer L2 U2U remote UE and / or different peer L2 U2U remote UEs can be multiplexed onto the same PC5 relay RLC channel, where the PC5 relay RLC channel is between the L2 U2U remote UE and the L2 U2U relay UE.

[0800] - For the traffic received at the L2 U2U remote UE, the same PC5 relay RLC channel from one L2 U2U relay UE can be demultiplexed into different end-to-end PC5 radio bearers (SL-SRB or SL-DRB) for the same peer L2 U2U remote UE and / or different peer L2 U2U remote UEs.

[0801] - The SRAP sublayer at the L2 U2U remote UE supports the identification of the peer L2 U2U remote UE and itself. The local ID is assigned by the L2 U2U relay UE to the two L2 U2U remote UEs for identification. For the two local IDs, one of the local IDs identifies the L2 U2U remote UE and the other local ID identifies the peer L2 U2U remote UE. The local ID of the peer L2 U2U remote UE and its own (i.e., the L2 U2U remote UE) local ID are delivered to the L2 U2U remote UE together with the corresponding L2 ID of the peer L2 U2U remote UE. The local ID of the L2 U2U remote UE and its own (i.e., the peer L2 U2U remote UE) local ID are delivered to the peer L2 U2U remote UE. The identification information of the end-to-end PC5 radio bearer and the two local IDs are included in the SRAP header so that the received packets for a specific PDCP entity at the peer L2 U2U remote UE can be associated with the correct end-to-end PC5 radio bearer of the L2 U2U remote UE.

[0802] For L2 UE - to - UE relay, the SRAP sublayer at the L2 U2U relay UE:

[0803] - The SRAP sublayer at the L2 U2U relay UE determines the egress PC5 relay RLC channel based on the mapping of the specific pair of end-to-end PC5 radio bearers between the L2 U2U remote UE and the peer L2 U2U remote UE and the egress PC5 relay RLC channel.

[0804] - For the ingress traffic received at the L2 U2U relay UE from one or more L2 U2U remote UEs, if the local IDs identifying the peer L2 U2U remote UEs are the same, then different end-to-end PC5 radio bearers (SRB or DRB) of the same L2 U2U remote UE and / or different L2 U2U remote UEs can be multiplexed onto the same egress PC5 relay RLC channel between the L2 U2U relay UE and the peer L2 U2U remote UE identified by the local ID.

[0805] […]

[0806] 5.8.9.1 Sidelink RRC Reconfiguration

[0807] 5.8.9.1.1 Overview

[0808] [The title of 3GPP R2-2311934 is "Sidelink RRC Reconfiguration, Success" Figure 5 .8.9.1.1-1 is reproduced as Figure 23

[0809] [The title of 3GPP R2-2311934 is "Sidelink RRC Reconfiguration, Failure" Figure 5 .8.9.1.1-2 is reproduced as Figure 24

[0810] The purpose of this procedure is to modify the PC5-RRC connection, for example to establish / modify / release a sidelink DRB or a PC5 relay RLC channel, to (re)configure NR sidelink measurements and reporting, to (re)configure sidelink CSI reference signal resources, to (re)configure CSI reporting latency constraints, to (re)configure sidelink DRX and (re)configure the latency constraints for SL UE-to-UE coordinated reporting.

[0811] In the following cases, the UE can initiate the sidelink RRC reconfiguration procedure and perform the operations in Clause 5.8.9.1.2 on the corresponding PC5-RRC connection:

[0812] - Release of a sidelink DRB associated with a peer UE, as specified in Clause 5.8.9.1a.1;

[0813] - Establishment of a sidelink DRB associated with a peer UE, as specified in Clause 5.8.9.1a.2;

[0814] - Modification of the parameters included in the SLRB-Config for a sidelink DRB associated with a peer UE, as specified in Clause 5.8.9.1a.2;

[0815] ​​- Release of PC5 relay RLC channels for L2 U2N / U2U relay UE and remote UE as specified in clause 5.8.9.7.1;

[0816] -Establishment of PC5 relay RLC channels for L2 U2N / U2U relay UE and remote UE as specified in clause 5.8.9.7.2;

[0817] - modification of the parameters contained in SL-RLC-ChannelConfigPC5 for the PC5 relay RLC channel for L2 U2N / U2U relay UE and remote UE as specified in clause 5.8.9.7.2;

[0818] -(re)configuration of peer UE to perform NR sidelink measurements and reporting.

[0819] -(Re)configuration of sidelink CSI reference signal resources and CSI reporting delay bounds;

[0820] -(re)configuration of a peer UE to perform sidelink DRX;

[0821] -(Re)configuration of delay bounds for coordinated reporting between SL UEs;

[0822] - (re)configure the local UE ID and split QoS of the L2 U2U remote UE by the L2 U2U relay UE.

[0823] 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 the 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.

[0824] Editor’s note: The two conclusions regarding the TX remote UE derivation for e2e SL-DRB do not exclude the inclusion of information from gNB / pre-configuration / specified configuration for further study.

[0825] Editor's note: How the relay UE derives the second hop configuration for SL-DRB is for further study.

[0826] ​​​5.8.9.1.2 Actions related to the transmission of the RRCReconfigurationSidelink message

[0827] The UE shall configure the content of the RRCReconfigurationSidelink message as follows:

[0828] 1> For each sidelink DRB to be released, due to the configuration of sl-ConfigDedicatedNR, SIB12, SidelinkPreconfigNR, or the upper layer according to Clause 5.8.9.1a.1.1:

[0829] 2> Set the entries included in the slrb-ConfigToReleaseList corresponding to the sidelink DRB;

[0830] 1> For each sidelink DRB to be established or modified, due to the reception of sl-ConfigDedicatedNR, SIB12, or SidelinkPreconfigNR according to Clause 5.8.9.1a.2.1:

[0831] 2> If a sidelink DRB is to be established:

[0832] 3> Assign the new logical channel identifier of the logical channel to be associated with the sidelink DRB and set the sl-MAC-LogicalChannelConfigPC5 in the SLRB-Config to include the new logical channel identifier;

[0833] 2> Set the SLRB-Config included in the slrb-ConfigToAddModList according to the received sl-RadioBearerConfig and the sl-RLC-BearerConfig corresponding to the sidelink DRB;

[0834] 1> Configure sl-MeasConfig as follows:

[0835] 2> If the frequency for NR sidelink communication is included in the sl-FreqInfoToAddModList in the sl-ConfigDedicatedNR within the RRCReconfiguration message or in the sl-ConfigCommonNR within SIB12:

[0836] 3> If the UE is in RRC_CONNECTED:

[0837] 4> Configure sl-MeasConfig according to the NR sidelink measurement configuration information stored for this destination;

[0838] 3> If the UE is in RRC_IDLE or RRC_INACTIVE:

[0839] 4> Set sl-MeasConfig according to the stored NR sidelink measurement configuration received from SIB12;

[0840] 2> Otherwise:

[0841] 3> Set sl-MeasConfig according to sl-MeasPreconfig in SidelinkPreconfigNR;

[0842] 1> Set sl-LatencyBoundIUC-Report;

[0843] 1> Start timer T400 for the destination;

[0844] 1> Set sl-CSI-RS-Config;

[0845] 1> Set sl-LatencyBoundCSI-Report;

[0846] 1> Set sl-ResetConfig;

[0847] Note 1: Whether / how to set the parameters included in sl-LatencyBoundIUC-Report, sl-CSI-RS-Config, sl-LatencyBoundCSI-Report, and sl-ResetConfig depends on the UE implementation.

[0848] 1> Set sl-DRX-ConfigUC-PC5 as follows:

[0849] 2> If the frequency for NR sidelink communication is included in sl-FreqInfoToAddModList in sl-ConfigDedicatedNR within the RRCReconfiguration message or in sl-ConfigCommonNR within SIB12:

[0850] 3> If the UE is in RRC_CONNECTED and if sl-ScheduledConfig is included in sl-ConfigDedicatedNR within RRCReconfiguration, then:

[0851] 4> Set sl-DRX-ConfigUC-PC5 according to the stored NR sidelink DRX configuration information for this destination.

[0852] Note 2: If the UE is in RRC_IDLE or in RRC_INACTIVE or out of coverage or in RRC_CONNECTED, and sl-UE-SelectedConfig is included in sl-ConfigDedicatedNR within RRCReconfiguration, then sl-DRX-ConfigUC-PC5 is set depending on the UE implementation.

[0853] 1> For each PC5 relay RLC channel to be released due to the configuration of sl-ConfigDedicatedNR:

[0854] 2> Set the SL-RLC-ChannelID corresponding to the PC5 relay RLC channel in sl-RLC-ChannelToReleaseListPC5;

[0855] 1> For each PC5 relay RLC channel to be established or modified due to receiving sl-ConfigDedicatedNR:

[0856] 2> If a PC5 relay RLC channel is to be established, then:

[0857] 3> Assign the new logical channel identifier of the logical channel to be associated with the PC5 relay RLC channel and set sl-MAC-LogicalChannelConfigPC5 in SL-RLC-ChannelConfigPC5 to include the new logical channel identifier;

[0858] 2> Set SL-RLC-ChannelConfigPC5 included in sl-RLC-ChannelToAddModListPC5 according to the received SL-RLC-ChannelConfig corresponding to the PC5 relay RLC channel, including setting sl-RLC-ChannelID-PC5 to the same value of the sl-RLC-ChannelID received in SL-RLC-ChannelConfig;

[0859] 1> If the UE acts as an L2 U2U relay UE:

[0860] 2> If both the PC5-RRC connection with the L2 U2U remote UE and the PC5-RRC connection with the peer L2U2U remote UE are successfully established, then:

[0861] 3>Assign a new local UE ID to the L2 U2U remote UE according to the association between the user information and the L2 ID specified in TS 23.304

[65] . And when necessary, set the sl-RemoteUE-LocalIdentity-config in SL-SRAP-ConfigPC5 to include the new local UE ID and the L2 ID of the L2 U2U remote UE;

[0862] 3>Allocate a new local UE ID to the peer L2 U2U remote UE according to the association between the user information and the L2 ID specified in TS 23.304

[65] , and when necessary, set the sl-RemoteUE-LocalIdentity-config in SL-SRAP-ConfigPC5 to include the new local UE ID and the L2 ID of the peer L2 U2U remote UE;

[0863] 3>Determine to submit an RRCReconfigurationSidelink message to the L2 U2U remote UE;

[0864] 3>Determine to submit an RRCReconfigurationSidelink message to the peer L2 U2U remote UE;

[0865] Editor's note: WA: Carry the L2 ID and the local ID in the RRCReconfigurationSidelink message, and assume that the association between the user information and the L2 ID is completed at the ProSe layer.

[0866] 2>If the sl-QoS-InfoListPC5 is included in the RRCReconfigurationSidelink message received from the source L2 U2U remote UE, then:

[0867] 3>Perform QoS splitting based on the sl-QoS-InfoListPC5 for each QoS flow to determine the split QoS for each PC5 hop, and set the sl-SplitQoS-InfoListPC5 to include the split QoS information on the second PC5 hop between the L2U2U relay UE and the target L2 U2U remote UE;

[0868] 3>Determine to submit an RRCReconfigurationSidelink message to the target L2 U2U remote UE;

[0869] 1>If the UE acts as the source L2 U2U remote UE, then:

[0870] 2> Set sl-QoS-InfoListPC5 to contain the end-to-end QoS attribute set of the sidelink QoS flow of the target L2 U2U remote UE, provided that it is configured by the upper layer;

[0871] 2> Set sl-DestinationIdentity to contain the associated destination of the target L2 U2U remote UE, provided that it is configured by the upper layer;

[0872] 2> Determine to submit an RRCReconfigurationSidelink message to the L2 U2U relay UE;

[0873] The UE shall submit the RRCReconfigurationSidelink message to the lower layer for transmission.

[0874] 5.8.9.1.3 UE receives RRCReconfigurationSidelink

[0875] The UE shall perform the following actions after receiving the RRCReconfigurationSidelink:

[0876] 1> If the RRCReconfigurationSidelink contains sl-ResetConfig:

[0877] 2> Execute the sidelink reset configuration procedure as specified in 5.8.9.1.10;

[0878] 1> If the RRCReconfigurationSidelink contains slrb-ConfigToReleaseList:

[0879] 2> For each entry value contained in the slrb-ConfigToReleaseList that is part of the current UE sidelink configuration;

[0880] 3> Execute the sidelink DRB release procedure according to Clause 5.8.9.1a.1;

[0881] 1> If the RRCReconfigurationSidelink contains slrb-ConfigToAddModList:

[0882] 2> For each slrb-PC5-ConfigIndex value contained in the slrb-ConfigToAddModList that is not part of the current UE sidelink configuration:

[0883] 3> If sl-MappedQoS-FlowsToAddList is included, then:

[0884] 4> Apply the SL-PQFIs included in sl-MappedQoS-FlowsToAddList;

[0885] 3> Execute the sidelink DRB addition procedure according to Clause 5.8.9.1a.2;

[0886] 2> For each slrb-PC5-ConfigIndex value included in slrb-ConfigToAddModList that is part of the current UE sidelink configuration:

[0887] 3> If sl-MappedQoS-FlowsToAddList is included, then:

[0888] 4> Add the SL-PQFIs included in sl-MappedQoS-FlowsToAddList to the corresponding sidelink DRB;

[0889] 3> If sl-MappedQoS-FlowsToReleaseList is included:

[0890] 4> Remove the SL-PQFIs included in sl-MappedQoS-FlowsToReleaseList from the corresponding sidelink DRB;

[0891] 3> If the sidelink DRB release conditions described in Clause 5.8.9.1a.1.1 are met, then:

[0892] 4> Execute the sidelink DRB release procedure according to Clause 5.8.9.1a.1.2;

[0893] 3> Otherwise if the sidelink DRB modification conditions described in Clause 5.8.9.1a.2.1 are met, then:

[0894] 4> Execute the sidelink DRB modification procedure according to Clause 5.8.9.1a.2.2;

[0895] 1> If the RRCReconfigurationSidelink message contains sl-MeasConfig:

[0896] 2> Execute the sidelink measurement configuration procedure as specified in 5.8.10;

[0897] 1> If the RRCReconfigurationSidelink message contains sl-CSI-RS-Config:

[0898] 2> Apply the sidelink CSI-RS configuration;

[0899] 1> If the RRCReconfigurationSidelink message contains sl-LatencyBoundCSI-Report:

[0900] 2> Apply the configured sidelink CSI report latency bound;

[0901] 1> If RRCReconfigurationSidelink contains sl-RLC-ChannelToReleaseListPC5:

[0902] 2> For each SL-RLC-ChannelID value included in sl-RLC-ChannelToReleaseListPC5 that is part of the current UE sidelink configuration;

[0903] 3> Execute the PC5 relay RLC channel release procedure according to Clause 5.8.9.7.1;

[0904] 1> If RRCReconfigurationSidelink contains sl-RLC-ChannelToAddModListPC5:

[0905] 2> For each sl-RLC-ChannelID-PC5 value included in sl-RLC-ChannelToAddModListPC5 that is not part of the current UE sidelink configuration:

[0906] 3> Execute the PC5 relay RLC channel addition procedure according to Clause 5.8.9.7.2;

[0907] 2> For each sl-RLC-ChannelID-PC5 value included in sl-RLC-ChannelToAddModListPC5 that is part of the current UE sidelink configuration:

[0908] 3> Execute the PC5 relay RLC channel modification procedure according to Clause 5.8.9.7.2;

[0909] 1> If the RRCReconfigurationSidelink message contains sl-DRX-ConfigUC-PC5, and

[0910] 1> If the UE accepts sl-DRX-ConfigUC-PC5:

[0911] 2> Configure the lower layer to perform sidelink DRX operations according to sl-DRX-ConfigUC-PC5 for the associated destination as defined in TS 38.321 [3];

[0912] 1> If the RRCReconfigurationSidelink message contains sl-LatencyBoundIUC-Report:

[0913] 2> Apply the configured sidelink IUC reporting latency bound;

[0914] 1> If the RRCReconfigurationSidelink message contains sl-RemoteUE-LocalIdentity-config and sl-PeerRemoteUE-LocalIdentity-Config, then:

[0915] 2> Configure the lower layer to perform NR sidelink U2U relay operations according to sl-RemoteUE-LocalIdentity-config for the L2 U2U remote UE and sl-PeerRemoteUE-LocalIdentity-config for the peer L2 U2U remote UE as defined in TS 38.351

[65] ;

[0916] 1> If the RRCReconfigurationSidelink contains sl-QoS-InfoListPC5, then:

[0917] 2> Perform the actions related to the transmission of the RRCReconfigurationSidelink as specified in 5.8.9.1.2;

[0918] 1> If the UE is unable to comply with the (partial) configuration included in the RRCReconfigurationSidelink (i.e., sidelink RRC reconfiguration fails):

[0919] 2> Continue to use the configuration used before the reception of the RRCReconfigurationSidelink message;

[0920] 2> Set the content of the RRCReconfigurationFailureSidelink message;

[0921] 3> Submit the RRCReconfigurationFailureSidelink message to the lower layer for transmission;

[0922] 1> Otherwise:

[0923] 2> Set the content of the RRCReconfigurationCompleteSidelink message;

[0924] 3> If the UE rejects the sidelink DRX configuration sl-DRX-ConfigUC-PC5 received from the peer UE, then:

[0925] 4> Include sl-DRX-ConfigReject in the RRCReconfigurationCompleteSidelink message;

[0926] 4> Do not consider the sidelink DRX to be applied to the corresponding sidelink unicast communication;

[0927] 3> If sl-SplitQoS-InfoListPC5 is included in the RRCReconfigurationSidelink message received from the L2 U2U relay UE, then:

[0928] 4> Set sl-AcceptQoS-InfoListPC5 to include the accepted QoS information on the second PC5 hop between the L2 U2U relay UE and the target L2 U2U remote UE, considering the received sl-SplitQoS-InfoListPC5;

[0929] 4> Determine to submit the RRCReconfigurationCompleteSidelink message to the L2 U2U relay UE;

[0930] 3> Submit the RRCReconfigurationCompleteSidelink message to the lower layer for transmission;

[0931] Note 1: When the same logical channel is configured with different RLC modes by another UE, the UE treats the situation as a sidelink RRC reconfiguration failure.

[0932] Note 2: It depends on the UE implementation to decide whether to indicate to the peer UE the rejection of the received sidelink DRX configuration.

[0933] […]

[0934] 5.8.9.1.9 UE Reception of RRCReconfigurationCompleteSidelink

[0935] The UE will perform the following actions after receiving RRCReconfigurationCompleteSidelink:

[0936] 1> Stop timer T400 for the destination (if it is running);

[0937] 1> Consider applying the configuration in the corresponding RRCReconfigurationSidelink message.

[0938] 2> If the RRCReconfigurationCompleteSidelink message contains sl-DRX-ConfigReject:

[0939] 3> Do not consider sidelink DRX to be applied to the corresponding sidelink unicast communication;

[0940] 2> If the RRCReconfigurationCompleteSidelink message received from the target L2 U2U remote UE contains sl-AcceptQoS-InfoListPC5, then:

[0941] 3> Set the content of the RRCReconfigurationCompleteSidelink message:

[0942] 4> Set sl-SplitQoS-InfoListPC5 to contain the split QoS information on the first PC5 hop between the source L2 U2U remote UE and the L2 U2U relay UE, considering the received sl-AcceptQoS-InfoListPC5;

[0943] 4> Set the set sl-DestinationIdentity to contain the associated destination of the target L2 U2U remote UE;

[0944] 3> Determine to submit the RRCReconfigurationCompleteSidelink message to the source L2 U2U remote UE;

[0945] 3> Submit the RRCReconfigurationCompleteSidelink message to the lower layer for transmission;

[0946] […]

[0947] -SL-SRAP-ConfigPC5

[0948] The IE SL-SRAP-ConfigPC5 is used to configure the configurable SRAP parameters used by the L2 U2U relay UE and the L2 U2U remote UE, as specified in TS 38.351

[66] .

[0949] SL-SRAP-ConfigPC5 information element

[0950] […]

[0951]

[0952]

[0953] […]

[0954]

[0955] […]

[0956] -RRCReconfigurationSidelink

[0957] The RRCReconfigurationSidelink message is a command for the AS configuration of the PC5 RRC connection. It is only applicable to unicast of NR sidelink communication.

[0958] Signaling radio bearer: SL-SRB3

[0959] RLC-SAP: AM

[0960] Logical channel: SCCH

[0961] Direction: UE-to-UE RRCReconfigurationSidelink message

[0962]

[0963]

[0964]

[0965]

[0966]

[0967] -RRCReconfigurationCompleteSidelink

[0968] The RRCReconfigurationCompleteSidelink message is used to confirm the successful completion of the PC5 RRC AS reconfiguration. It is only applicable to unicast for NR sidelink communication.

[0969] Signaling radio bearer: SL-SRB3

[0970] RLC-SAP: AM

[0971] Logical channel: SCCH

[0972] Direction: UE to UE

[0973] RRCReconfigurationCompleteSidelink message

[0974]

[0975]

[0976] 3GPP TS23.304 describes the support for relay between UEs. That is, a relay UE can be used to support communication between two (layer 2 or layer 3) ProSe end UEs, provided that the two UEs cannot communicate directly with each other. The relay UE between UEs establishes a PC5 link with each of the two ProSe end UEs containing the source ProSe end UE (e.g., on the first PC5 hop) and the target ProSe end UE (e.g., on the second PC5 hop) for forwarding traffic of the ProSe service of interest between the two ProSe end UEs. If the source 5G ProSe end UE wishes to communicate with multiple target 5G ProSe end UEs, the (first-hop) PC5 link between the source 5G ProSe layer 3 end UE and the 5G ProSe UE relay UE can be shared for multiple target 5G ProSe end UEs, while the (second-hop) PC5 link can be established separately between the 5G ProSe UE relay UE and the target 5G ProSe end UEs.

[0977] To establish a PC5 link, the layer 2 link establishment procedure without discovery specified in clause 6.7.1 of 3GPP TS23.304 or the layer 2 link establishment procedure with discovery specified in clause 6.7.3 of 3GPP TS23.304 can be used (i.e., the former can be used if the layer 2 link establishment procedure is initiated towards a relay UE or the source UE has selected a specific relay UE, and the latter can be used if the layer 2 link establishment procedure is initiated towards any relay UE or the source UE has not discovered any relay UE). For a shared PC5 link, the layer 2 link modification procedure shall be used. According to 3GPP TS23.304, the PC5 link can be associated with a relay service code and can support one or more services identified by one or more ProSe identifiers.

[0978] Clause 6.4.3.7.4 of 3GPP TS23.304 states that the user information ID of the target 5G ProSe end UE can optionally be included in the first-hop direct communication request (DCR) message and the second-hop DCR message. This implies that the service-oriented link establishment procedure introduced in clause 6.4.3.1 of 3GPP TS23.304 can also be supported for UE-to-UE relay communication. The source UE can send a first-hop DCR message that does not contain any user information of the target 5G ProSe end UE to the relay UE. In response to receiving the first-hop DCR message, the relay UE can send a second-hop DCR message that also does not contain any user information of the target 5G ProSe end UE. Both the first-hop DCR message and the second-hop DCR message can contain a relay service code for identifying the connectivity service. It is possible that more than one target 5G ProSe end UE can receive the second-hop DCR message from the relay UE, and these target 5G ProSe end UEs may be interested in the connectivity service or they can match the relay service code.

[0979] In this case, each of these target 5G ProSe end UEs can continue with the corresponding link establishment procedure with the relay UE to establish the respective second-hop PC5 link between the relay UE and each target 5G ProSe end UE. For example, there is a first target end UE and a second target end UE and they receive the second-hop DCR message from the relay UE. The first target end UE can then establish a first second-hop PC5 link with the relay UE, and the second target end UE can then also establish a second second-hop PC5 link with the relay UE. The first target end UE can send a first second-hop DCA message to the relay UE to complete the establishment of the first second-hop PC5 link. The second target end UE can send a second second-hop DCA message to the relay UE to complete the establishment of the second second-hop PC5 link. Thereafter, the relay UE can respond to the source UE with a first-hop direct communication acceptance (DCA) message.

[0980] According to 3GPP TS24.554, if the 5G ProSe direct link establishment procedure is for 5G ProSe direct communication between the 5G ProSe end UE and the 5G ProSe UE (U2U) relay UE among 5G ProSe UEs, the source user information IE included in the ProSe direct link establishment acceptance message (i.e., the direct communication acceptance message) is set to the user information identifier (ID) of the target 5G ProSe end UE. That is, the relay UE can send a first-hop DCA message including only the user information of the first target end UE or the second target end UE, because such source user information IE of the ProSe direct link establishment acceptance message is designated to indicate only one user information ID or one application layer ID. For example, the first-hop DCA message can include the user information of the first target end UE. Since the second target end UE is also involved in the U2U relay communication with the source end UE via the relay UE, the relay UE can additionally initiate, for example, a link modification procedure with the source end UE to modify the first-hop PC5 link for adding the second target end UE.

[0981] In addition, item number h) in clause 7.2.2.3 of 3GPP TS24.554 is designated for the relay UE to include in the ProSe direct link establishment acceptance message the target 5G ProSe layer 3 end UE IP address information element (IE) set to the IP address of the target 5G ProSe layer 3 end UE, provided that the 5G ProSe direct link establishment procedure is for 5G ProSe direct communication between the source 5G ProSe layer 3 end UE and the relay UE among 5G ProSe layer 3 UEs, and the data unit type for communication is IP. Similarly, following the above example, the relay UE can also include the IP address of the first target end UE in the first-hop DCA message. The relay UE may need to initiate a link modification procedure with the source end UE to modify the first-hop PC5 link for adding the second target end UE together with the IP address of the second target end UE. The concept can be shown in Figure 25 shown.

[0982] In terms of reducing latency and signaling overhead, it is beneficial for the relay UE to indicate / include the user information of the second target end UE in addition to the user information of the first target end UE in the first-hop direct communication acceptance (DCA) message, and thus the source end UE can understand through receiving the first-hop DCA message that the first-hop PC5 link is established to communicate with both the first target end UE and the second target end UE via the relay UE. The relay UE can also include the IP address of the first target end UE and the IP address of the second target end UE for communication with the source end UE in the first-hop DCA message.

[0983] Thus, the source user information IE in the ProSe direct link establishment acceptance message can be further specified and thus include one or more application layer IDs or user information IDs of the target 5G ProSe end UE. Alternatively, a new IE (different from the existing source user information IE) in the ProSe direct link establishment acceptance message can be specified for the case of U2U relay communication and thus include one or more application layer IDs or user information IDs of the target 5G ProSe end UE.

[0984] In addition, the target 5G ProSe layer 3 end UE IP address IE or a similar purpose IE in the ProSe direct link establishment acceptance message can be specified and thus include one or more IP addresses of the target 5G ProSe end UE.

[0985] The above solutions can be shown in Figure 26 this.

[0986] More specifically, the PC5 link can be a PC5 connection, a unicast link, a direct link, a layer 2 link, etc. The source end UE can be a source 5G proximity service (ProSe) end UE. The target end UE can be a target 5G ProSe end UE. The relay UE can be a 5G ProSe UE - to - UE relay UE. The user information can be a user information ID, an application layer ID, or an upper layer ID.

[0987] More specifically, the first - hop direct communication request (DCR) message can be sent by using the source layer 2 ID of the source end UE and the destination layer 2 ID. The destination layer 2 ID can be a broadcast layer 2 ID associated with a relay service code or a connectivity service.

[0988] More specifically, the second - hop DCR message can be sent by using the source layer 2 ID and the destination layer 2 ID of the relay UE. The destination layer 2 ID can be a broadcast layer 2 ID associated with a relay service code or a connectivity service.

[0989] More specifically, the first second - hop DCA message can be sent by using the layer 2 ID of the first target end UE as the source and the layer 2 ID of the relay UE as the destination. The second second - hop DCA message can be sent by using the layer 2 ID of the second target end UE as the source and the layer 2 ID of the relay UE as the destination.

[0990] More specifically, the first - hop DCA message can be sent by using the layer 2 ID of the relay UE as the source and the layer 2 ID of the source end UE as the destination.

[0991] According to 3GPP R2-2312029, the relay UE can allocate / assign a local UE ID for each end UE after the U2U relay communication is established. According to 3GPP R2-2311934, the local UE ID and layer 2 ID of the end UE are sent to the peer UE together with the local UE ID and layer 2 ID of the peer UE by using a PC5 radio resource control (RRC) message (i.e., RRCReconfigurationSidelink). In 3GPP R2-2311934, the SL-SRAP-ConfigPC5 IE used to provide the mapping of the local UE ID and layer 2 ID is included in the RRCReconfigurationSidelink message. It should be noted that the format in which the SL-SRAP-ConfigPC5 IE is constructed allows the mapping of the local UE ID and layer 2 ID for the end UE and the mapping of the local UE ID and layer 2 ID for the peer UE to be provided at one time (i.e., given in a single RRCReconfigurationSidelink message). Since one-to-many U2U relay communication can be established (such as Figure 26 shown), so the source UE may need a first mapping of the local UE ID and layer 2 ID for the target UE1 and a second mapping of the local UE ID and layer 2 ID for the target UE2.

[0992] Since the RRCReconfigurationSidelink message carries a single mapping of the local UE ID and layer 2 ID for the peer UE at one time, such as Figure 27 As shown in , the relay UE needs to send multiple RRCReconfigurationSidelink messages to the source UE in order to provide the source UE with all the required mappings of the local UE ID and layer 2 ID for the target UE. In terms of efficiency, the structure of the SL-SRAP-ConfigPC5 IE can be considered again, so that the relay UE can send a single RRCReconfigurationSidelink message to the source UE to carry all the mappings of the local UE ID and layer 2 ID for the target UE required by the source UE. The concept of the solution can be found in Figure 28 is shown in .

[0993] Another concept of solution can be found in Figure 29is shown, where a single RRCReconfigurationSidelink message may indicate or contain a list, where each entry of the list may indicate a pair or mapping of a local ID and a layer 2 ID for a target UE (whose local ID is assigned, modified, or updated). The local ID update associated with the one or more target UEs may be performed in response to a change or update of the (one or more) destination IDs or local IDs associated with the one or more target UEs. The relay UE may update the first local ID of the first target UE in response to a change or update of the second local ID of the second target UE.

[0994] The following textual proposal may be an illustration of the above solution.

[0995]

[0996]

[0997] More specifically, maxNrofSL-Dest-r16 may be a multiplicity and type constraint and represents an integer (i.e., 32) indicating the maximum number of destinations for NR sidelink communication. For U2U relay communication, this constraint may be used to indicate the maximum number of target UEs communicating with the source UE.

[0998] More specifically, the IE sl-PeerRemoteUE-LocalIdentity-ConfigList in the above textual proposal may contain one or more IEs of SL-PeerRemoteUE-LocalIdentity-Config.

[0999] Additionally or alternatively, the source UE may be an L2 (U2U) remote UE. The peer UE and / or the target UE may be a peer (L2 U2U) remote UE. The mapping of the local UE ID and the layer 2 ID may be an entry or pair of the local UE ID and the layer 2 ID in the RRCReconfigurationSidelink message.

[1000] Figure 30It is a flowchart 3000 for a relay UE. In step 3005, the relay UE establishes a first UE - to - UE (U2U) relay communication between the source UE and the first target UE and a second U2U relay communication between the source UE and the second target UE. In step 3010, the relay UE sends a PC5 radio resource control (RRC) message to the source UE, where the PC5 RRC message contains list information indicating at least one of a first mapping of a first local UE identifier (ID) and a first layer 2 ID for the first target UE and a second mapping of a second local UE ID and a second layer 2 ID for the second target UE.

[1001] In one embodiment, the information may indicate a third mapping of a third local UE ID and a third layer 2 ID for the source UE. The relay UE may send the PC5 RRC message in response to the configuration or re - configuration of the first local UE ID and / or the second local UE ID and / or the third local UE ID. The PC5 RRC message may be an RRCReconfigurationSidelink.

[1002] In one embodiment, the first mapping of the first local UE ID and the first layer 2 ID for the first target UE may be indicated in a first SL - SRAP - ConfigPC5, and the second mapping of the second local UE ID and the second layer 2 ID for the second target UE may be indicated in a second SL - SRAP - ConfigPC5.

[1003] In one embodiment, the information may include a first entry indicating the first mapping of the first local UE ID and the first layer 2 ID for the first target UE, or a second entry indicating the second mapping of the second local UE ID and the second layer 2 ID for the second target UE.

[1004] In one embodiment, the source UE may be an L2 U2U remote UE. The first target UE and the second target UE may be peer L2 U2U remote UEs.

[1005] In one embodiment, the relay UE may receive a first message from the source UE, where the first message will establish a first-hop PC5 connection with the relay UE for communication with any destination UE. The relay UE may establish at least a first second-hop PC5 connection with a first destination UE and a second second-hop PC5 connection with a second destination UE for communication with the source UE. The relay UE may send a second message to the source UE, where the second message will complete the establishment of the first-hop PC5 connection and include the user information of the first destination UE and the user information of the second destination UE. The second message may include the layer 2 ID of the first destination UE and the layer 2 ID of the second destination UE.

[1006] In one embodiment, the relay UE may send a third message in response to receiving the first message, where the third message will establish a second-hop PC5 connection with any destination UE for communication with the source UE. The relay UE may receive a fourth message from the first destination UE, where the fourth message will complete the establishment of the first second-hop PC5 connection with the relay UE for communication with the source UE. The relay UE may receive a fifth message from the second destination UE, where the fifth message will complete the establishment of the second second-hop PC5 connection with the relay UE for communication with the source UE.

[1007] In one embodiment, the first message may include the user information of the source UE, the user information of the relay UE, the relay service code, etc., and may not include the user information of any destination UE. The second message may further include the user information of the source UE, the user information of the relay UE, the relay service code, the IP address of the first destination UE, the IP address of the second destination UE, etc. The third message may include the layer 3 ID of the source UE, the user information of the source UE, the user information of the relay UE, the relay service code, etc., and may not include the user information of any destination UE. The fourth message may include the layer 3 ID of the source UE, the user information of the source UE, the user information of the relay UE, the relay service code, the user information of the first destination UE, etc. The fifth message may include the layer 3 ID of the source UE, the user information of the source UE, the user information of the relay UE, the relay service code, the user information of the second destination UE, etc.

[1008] In one embodiment, the first / third message may be a direct communication request message or a ProSe direct link establishment request message. The second / fourth / fifth message may be a direct communication acceptance message or a ProSe direct link establishment acceptance message.

[1009] In one embodiment, the user information may be a user information ID or an application layer ID. The PC5 RRC message may include list information indicating a mapping of a third local UE ID and a third layer 2 ID for a source UE.

[1010] In one embodiment, the list information indicating at least a first mapping of a first local UE ID and a first layer 2 ID for a first target UE and / or a second mapping of a second local UE ID and a second layer 2 ID for a second target UE may be a list of local UE ID and layer 2 ID mappings, where an entry in the list indicates the first mapping of the first local UE ID and the first layer 2 ID, and another entry in the list indicates the second mapping of the second local UE ID and the second layer 2 ID.

[1011] Now refer to Figure 3 and 4 , in an exemplary embodiment from the perspective of a relay UE. The relay UE 300 includes program code 312 stored in a memory 310. The CPU 308 may execute the program code 312 to enable the relay UE to: (i) establish a first U2U relay communication between a source UE and a first target UE and a second U2U relay communication between the source UE and a second target UE, and (ii) send a PC5 RRC message to the source UE, where the PC5 RRC message includes list information indicating at least one of a first mapping of a first local UE ID and a first layer 2 ID for the first target UE and a second mapping of a second local UE ID and a second layer 2 ID for the second target UE. In addition, the CPU 308 may execute the program code 312 to perform all of the above actions and steps or other actions and steps described herein.

[1012] The various aspects of the present disclosure have been described above. It should be understood that the teachings herein may be implemented in a wide variety of forms, and any specific structure, function, or both disclosed herein are merely representative. Based on the teachings herein, those skilled in the art should understand that the aspects disclosed herein may be implemented independently of any other aspect, and two or more of these aspects may be combined in various ways. For example, any number of the aspects set forth herein may be used to implement a device or practice a method. Additionally, such a device may be implemented or such a method may be practiced using other structures, functionality, or a combination of structures and functionality other than one or more of the aspects set forth herein. As an example of some of the above concepts, in some aspects, parallel channels may be established based on a pulse repetition frequency. In some aspects, parallel channels may be established based on a pulse position or offset. In some aspects, parallel channels may be established based on a hopping sequence. In some aspects, parallel channels may be established based on a pulse repetition frequency, a pulse position or offset, and a time hopping sequence.

[1013] Those skilled in the art will understand that any one of a variety of different technologies and techniques can be used to represent information and signals. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referred to throughout the above description can be represented by voltage, current, electromagnetic waves, magnetic fields or magnetic particles, optical fields or optical particles, or any combination thereof.

[1014] Those skilled in the art will further understand that the various illustrative logical blocks, modules, processors, components, circuits, and algorithmic steps described in connection with the various aspects disclosed herein can be implemented as electronic hardware (e.g., digital implementation, analog implementation, or a combination of both that can be designed using source decoding or some other technique), incorporated into various forms of program or design code with instructions (for convenience, which may be referred to herein as "software" or "software modules"), or a combination of both. To clearly illustrate the interchangeability of hardware and software, the various illustrative components, blocks, modules, circuits, and steps have been generally described above in terms of their functionality. Whether this functionality is implemented as hardware or software depends on the particular application and the design constraints imposed on the overall system. Those skilled in the art can implement the described functionality in different ways for each particular application, but such implementation decisions should not be construed as departing from the scope of the present disclosure.

[1015] In addition, the various illustrative logical blocks, modules, and circuits described in connection with the aspects disclosed herein can be implemented within or performed by an integrated circuit ("IC"), an access terminal, or an access point. The IC can 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 can execute code or instructions residing within the IC, outside the IC, or in both cases. The general-purpose processor can be a microprocessor, but in the alternative, the processor can be any conventional processor, controller, microcontroller, or state machine. The processor can also be implemented as a combination of computing devices, such as a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

[1016] It should be understood that any particular 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 appended method claims present the elements of the various steps in a sample order and are not intended to be limited to the specific order or hierarchy presented.

[1017] The steps of a method or algorithm described in connection with the various aspects disclosed herein can be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. Software modules (e.g., including executable instructions and related data) and other data can reside in a data memory, such as RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, a hard disk, a removable disk, a CD-ROM, or any other form of computer-readable storage medium known in the art. A sample storage medium can be coupled to a machine such as a computer / processor (for convenience, the machine may be referred to herein as a "processor") such that the processor can read information (e.g., code) from the storage medium and write information to the storage medium. The sample storage medium can be integral with the processor. The processor and the storage medium can reside in an ASIC. The ASIC can reside in a user device. In an alternative, the processor and the storage medium can reside in the user device as discrete components. Additionally, in some aspects, any suitable computer program product can include a computer-readable medium that includes code associated with one or more of the aspects of the present disclosure. In some aspects, the computer program product can include packaging material.

[1018] Although the invention has been described in connection with various aspects, it is to be understood that the invention is capable of further modification. This application is intended to cover any variations, uses, or adaptations of the invention, which generally follow the principles of the invention and include such departures from the present disclosure as come within the known and customary practice within the art to which the invention pertains.

Claims

1. A method for relaying user equipment, characterized in that: The method comprises: The relay user equipment establishes a first inter-user equipment relay communication between the source user equipment and the first target user equipment and a second inter-user equipment relay communication between the source user equipment and the second target user equipment; and The relay user equipment sends a PC5 radio resource control message to the source user equipment, wherein the PC5 radio resource control message includes list information indicating at least one of a first mapping of a first local user equipment identifier and a first layer 2 identifier for the first target user equipment and a second mapping of a second local user equipment identifier and a second layer 2 identifier for the second target user equipment.

2. The method according to claim 1, characterized in that The list information indicates a third mapping between a third local user equipment identifier and a third layer 2 identifier for the source user equipment.

3. The method according to claim 2, characterized in that The relay user equipment sends the PC5 radio resource control message in response to configuration or reconfiguration of the first local user equipment identity and / or the second local user equipment identity and / or the third local user equipment identity.

4. The method according to claim 1, characterized in that: The PC5 radio resource control message is RRCReconfigurationSidelink.

5. The method according to claim 1, characterized in that The first mapping of the first local user equipment identifier and the first layer 2 identifier for the first target end user equipment is indicated in the first SL-SRAP-ConfigPC5, and the second mapping of the second local user equipment identifier and the second layer 2 identifier for the second target end user equipment is indicated in the second SL-SRAP-ConfigPC5.

6. The method according to claim 1, characterized in that The list information includes a first entry indicating the first mapping of the first local user equipment identifier and the first layer 2 identifier for the first target end user equipment, or includes a second entry indicating the second mapping of the second local user equipment identifier and the second layer 2 identifier for the second target end user equipment.

7. The method according to claim 1, characterized in that The source user equipment is a remote user equipment between L2 user equipments.

8. The method according to claim 1, characterized in that The first target end user equipment and the second target end user equipment are peer L2 inter-user equipment remote user equipment.

9. A relay user equipment, characterized in that: The relay user equipment comprises: Control circuit; a processor installed in the control circuit; and 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 inter-user equipment relay communication between a source-end user equipment and a first target-end user equipment and a second inter-user equipment relay communication between the source-end user equipment and a second target-end user equipment; and A PC5 radio resource control message is sent to the source end user equipment, wherein the PC5 radio resource control message includes list information indicating at least one of a first mapping of a first local user equipment identifier and a first layer 2 identifier for the first target end user equipment and a second mapping of a second local user equipment identifier and a second layer 2 identifier for the second target end user equipment.

10. The relay user equipment according to claim 9, characterized in that: The list information indicates a third mapping between a third local user equipment identifier and a third layer 2 identifier for the source user equipment.

11. The relay user equipment according to claim 10, characterized in that: The processor is further configured to execute program code stored in the memory to: The PC5 radio resource control message is sent in response to configuration or reconfiguration of the first local user equipment identity and / or the second local user equipment identity and / or the third local user equipment identity.

12. The relay user equipment according to claim 9, characterized in that: The PC5 radio resource control message is RRCReconfigurationSidelink.

13. The relay user equipment according to claim 9, characterized in that: The first mapping of the first local user equipment identifier and the first layer 2 identifier for the first target end user equipment is indicated in the first SL-SRAP-ConfigPC5, and the second mapping of the second local user equipment identifier and the second layer 2 identifier for the second target end user equipment is indicated in the second SL-SRAP-ConfigPC5.

14. The relay user equipment according to claim 9, characterized in that: The list information includes a first entry indicating the first mapping of the first local user equipment identifier and the first layer 2 identifier for the first target end user equipment, or includes a second entry indicating the second mapping of the second local user equipment identifier and the second layer 2 identifier for the second target end user equipment.

15. The relay user equipment according to claim 9, characterized in that: The source user equipment is a remote user equipment between L2 user equipments.

16. The relay user equipment according to claim 9, characterized in that: The first target end user equipment and the second target end user equipment are peer L2 inter-user equipment remote user equipment.

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