Method and apparatus for supporting multi-hop user equipment for inter-user equipment relay

Abstract

The invention discloses a method and equipment for supporting multi-hop user equipment for relay between user equipment. The second relay user equipment stores a maximum number of hops specific to the relay service code provided by the network. Further, the second relay user equipment receives a first PC5-S message from the first relay user equipment, where the first PC5-S message includes a user information identification of the first end user equipment, a relay service code, and an accumulated hop count. In addition, if the cumulative hop count plus 1 is less than the maximum hop count, the second relay user equipment transmits or broadcasts a second PC5-S message, where the second PC5-S message includes a user information identifier and a relay service code of the first end user equipment.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 528,307, filed on July 21, 2023, the entire disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0003] The present disclosure relates generally to wireless communication networks, and more particularly, to a method and apparatus for supporting multi-hop inter-UE relay in a wireless communication system, and more particularly to a method and apparatus for supporting multi-hop user equipment for inter-UE relay. Background Art

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

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

[0006] A method and apparatus for supporting multi-hop inter-UE relay is disclosed. In one embodiment, a second relay UE stores a maximum hop count specific to a relay service code (RSC) provided by a network. In addition, the second relay UE receives a first PC5-S message from a first relay UE, wherein the first PC5-S message includes a user information identifier (ID) of the first end UE, an RSC, and a first cumulative hop count. In addition, if the first cumulative hop count plus 1 is less than or equal to the maximum hop count, the second relay UE transmits or broadcasts a second PC5-S message, wherein the second PC5-S message includes the user information ID and RSC of the first end UE. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1A diagram illustrating a wireless communication system according to an exemplary embodiment;

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

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

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

[0011] Figure 5 For 3GPP TS23.304V18.2.0 Figure 4 .2.8-1 reappearance;

[0012] Figure 6 For 3GPP TS23.304V18.2.0 Figure 6 .3.2.1-1 reappearance;

[0013] Figure 7 For 3GPP TS23.304V18.2.0 Figure 6 .3.2.1-2 reappearance;

[0014] Figure 8 For 3GPP TS23.304V18.2.0 Figure 6 .3.2.4.2-1 reappearance;

[0015] Fig. 9 For 3GPP TS23.304V18.2.0 Figure 6 .3.2.4.3-1 reappearance;

[0016] Fig.10 For 3GPP TS23.304V18.2.0 Figure 6 .4.3.1-1 reappearance;

[0017] Fig.11 For 3GPP TS23.304V18.2.0 Figure 6 .7.3.2-1 reappearance;

[0018] Fig.12 For 3GPP TS23.304V18.2.0 Figure 6 .7.3.3-1 reappearance;

[0019] Fig.13 For 3GPP TS24.554V18.1.0 Fig.11 .2. Reappearance of y.1;

[0020] Fig.14 It is a reproduction of Table 11.2.y.1 of 3GPP TS24.554 V18.1.0;

[0021] Fig.15 illustrates an exemplary 3-hop inter-UE relay according to an exemplary embodiment;

[0022] Fig.16 illustrates multi-hop inter-UE relay according to an exemplary embodiment;

[0023] Fig.17 illustrates multi-route inter-UE relay according to an exemplary embodiment;

[0024] Fig.18 is a flow chart according to an exemplary embodiment;

[0025] Fig.19 is a flow chart according to an exemplary embodiment. DETAILED DESCRIPTION

[0026] The exemplary wireless communication systems and devices described below adopt wireless communication systems that support broadcast services. Wireless communication systems are widely deployed to provide various types of communications such as voice, data, etc. These systems can be based on code division multiple access (CDMA), time division multiple access (TDMA), orthogonal frequency division multiple access (OFDMA), 3GPP Long Term Evolution (LTE) wireless access, 3GPP Long Term Evolution Advanced (LTE-A or Advanced LTE), 3GPP2 Ultra Mobile Broadband (UMB), WiMax, 3GPP New Radio (NR) or some other modulation technology.

[0027] Specifically, the exemplary wireless communication systems and devices described below may be designed to support one or more standards, such as those provided by an alliance named “3rd Generation Partnership Project” referred to herein as 3GPP, including: TS23.304V18.2.0, “Proximity based Service (ProSe) in 5G System (5GS) (Release 18)”; TS24.554V18.1.0, “Proximity Service (ProSe) in 5G System (5GS) Protocol Aspects; Stage 3 (Release 18)”; and TS22.261V19.3.0, “Service Requirements for 5G System; Stage 1 (Release 19)”. The standards and documents listed above are expressly incorporated herein by reference in their entirety.

[0028] Figure 1 A multiple access wireless communication system according to an embodiment of the present invention is shown. An access network 100 (AN) includes multiple antenna groups, one group includes 104 and 106, another group includes 108 and 110, and an additional group includes 112 and 114. Figure 1 , only two antennas are shown for each antenna group, however, each antenna group may utilize more or fewer antennas. Access terminal 116 (AT) communicates with antennas 112 and 114, where antennas 112 and 114 transmit information to access terminal 116 via forward link 120 and receive information from access terminal 116 via reverse link 118. Access terminal (AT) 122 communicates with antennas 106 and 108, where antennas 106 and 108 transmit information to access terminal (AT) 122 via forward link 126 and receive information from access terminal (AT) 122 via reverse link 124. In a frequency division duplex (FDD) system, communication links 118, 120, 124, and 126 may use different frequencies for communication. For example, forward link 120 may use a different frequency than reverse link 118.

[0029] Each antenna group and / or the area in which the antenna group is designed to communicate is often referred to as a sector of the access network. In an embodiment, the antenna groups are each designed to communicate with access terminals in a sector of the area covered by the access network 100.

[0030] In communicating via forward links 120 and 126, the transmit antennas of access network 100 may utilize beamforming in order to improve the signal-to-noise ratio of the forward links for the different access terminals 116 and 122. Also, an access network using beamforming to transmit to access terminals randomly dispersed throughout its coverage area may cause less interference to access terminals in neighboring cells than if the access network transmitted to all of its access terminals via a single antenna.

[0031] An access network (AN) may be a fixed station or base station for communicating with a terminal, and may also be referred to as an access point, a Node B, a base station, an enhanced base station, an evolved Node B (eNB), a network node, a network, or some other terminology. An access terminal (AT) may also be referred to as a user equipment (UE), a wireless communication device, a terminal, an access terminal, or some other terminology.

[0032] Figure 2 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 multiple input multiple output (MIMO) system 200. At the transmitter system 210, traffic data for a number of data streams is provided from a data source 212 to a transmit (TX) data processor 214.

[0033] In one embodiment, each data stream is transmitted via a respective transmit antenna.TX data processor 214 formats, codes, and interleaves the traffic data for each data stream based on a particular coding scheme selected for that data stream to provide coded data.

[0034] The coded data for each data stream may be multiplexed with pilot data using OFDM techniques. The pilot data is typically a known data pattern that is processed in a known manner and may be used at the receiver system to estimate the channel response. The multiplexed pilot and coded data for each data stream are then modulated (i.e., symbol mapped) based on a specific modulation scheme selected for the data stream (e.g., Binary Phase Shift Keying (BPSK), Quadrature Phase Shift Keying (QPSK), Multiple Phase Shift Keying (M-PSK), or Quadrature Amplitude Modulation (M-QAM)) to provide modulation symbols. The data rate, coding, and modulation for each data stream may be determined by instructions executed by the processor 230.

[0035] The modulation symbols for all data streams are then provided to a TX MIMO processor 220, which may further process the modulation symbols (e.g., for OFDM). T The modulation symbol stream is provided to N T transmitters (TMTR) 222a through 222t. In certain embodiments, TX MIMO processor 220 applies beamforming weights to the symbols of the data streams and to the antenna from which the symbol is being transmitted.

[0036] Each transmitter 222 receives and processes a respective symbol stream to provide one or more analog signals, and further conditions (eg, amplifies, filters, and upconverts) the analog signals to provide a modulated signal suitable for transmission over the MIMO channel. T The antennas 224a to 224t transmit the N signals from the transmitters 222a to 222t. T a modulated signal.

[0037] At the receiver system 250, N R The transmitted modulated signals are received by each antenna 252a through 252r and the received signal from each antenna 252 is provided to a respective receiver (RCVR) 254a through 254r. Each receiver 254 conditions (e.g., filters, amplifies, and downconverts) a respective received signal, digitizes the conditioned signal to provide samples, and further processes the samples to provide a corresponding “received” symbol stream.

[0038] The RX data processor 260 then receives and processes the N R The N received by the receiver 254 R symbol streams to provide N T The RX data processor 260 then demodulates, deinterleaves, and decodes each detected symbol stream to recover the traffic data for the data stream. The processing by the RX data processor 260 is complementary to the processing performed by the TX MIMO processor 220 and the TX data processor 214 at the transmitter system 210.

[0039] Processor 270 periodically determines which pre-coding matrix to use (discussed below). Processor 270 formulates a reverse link message comprising a matrix index portion and a rank value portion.

[0040] The reverse link message may include various types of information about the communication link and / or the received data stream. The reverse link message is then processed by the TX data processor 238, which also receives traffic data for a number of data streams from the data source 236, modulated by the modulator 280, conditioned by the transmitters 254a to 254r, and transmitted back to the transmitter system 210.

[0041] At the transmitter system 210, the modulated signals from the receiver system 250 are received by the antenna 224, conditioned by the receiver 222, demodulated by the demodulator 240, and processed by the RX data processor 242 to extract the reverse link message transmitted by the receiver system 250. The processor 230 then determines which precoding matrix to use to determine the beamforming weights and then processes the extracted message.

[0042] Steering Figure 3 , this figure shows an alternative simplified functional block diagram of a communication device according to one embodiment of the present invention. Figure 3 As shown, the communication device 300 in the wireless communication system can be used to implement Figure 1 UE (or AT) 116 and 122 in or Figure 1 The base station (or AN) 100 in the wireless communication system is preferably an NR system. The communication device 300 may include an input device 302, an output device 304, a control circuit 306, a central processing unit (CPU) 308, a memory 310, a program code 312 and a transceiver 314. The control circuit 306 executes the program code 312 in the memory 310 through the CPU 308, thereby controlling the operation of the communication device 300. The communication device 300 can receive signals input by the user through the input device 302 (such as a keyboard or a keypad), and can output images and sounds through the output device 304 (such as a display or a speaker). The transceiver 314 is used to receive and transmit wireless signals, pass the received signals to the control circuit 306, and wirelessly output the signals generated by the control circuit 306. The communication device 300 in the wireless communication system can also be used to implement Figure 1 AN 100 in.

[0043] Figure 4 According to one embodiment of the present invention, Figure 3 4. In this embodiment, program code 312 includes application layer 400, layer 3 portion 402, and layer 2 portion 404, and is coupled to layer 1 portion 406. Layer 3 portion 402 typically performs radio resource control. Layer 2 portion 404 typically performs link control. Layer 1 portion 406 typically performs physical connectivity.

[0044] 3GPP TS 23.304 specifies procedures related to inter-UE relay as follows:

[0045] 4.2.8 5G ProSe Inter-UE Relay Reference Architecture

[0046] Figure 4.2.8-1 shows the layer 2 and layer 3 5G ProSe inter-UE relay reference architecture. 5G ProSe UEs communicate with each other via the 5G ProSe inter-UE relay.

[0047] [3GPP TS23.304 V18.2.0 titled "Reference architecture for 5G ProSe inter-UE relay" Figure 4 .2.8-1 reproduced as Figure 5 ]

[0048] Each 5G ProSe end UE and 5G ProSe inter-UE relay may have a subscription from the same PLMN or different PLMNs.

[0049] […]

[0050] 5.1.5.1 Policy / Parameter Provisioning for 5G ProSe Inter-UE Relay

[0051] The following information is provisioned in the UE to support UEs that assume the role of 5G ProSe inter-UE relay:

[0052] 1) Authorization policy for acting as 5G ProSe Layer 3 and / or Layer 2 Inter-UE Relay when the UE is “served by NG-RAN”:

[0053] -The PLMN to which the UE is authorized to relay traffic for 5G ProSe Layer 3 and / or Layer 2 end UEs accessing the 5G ProSe inter-UE relay over the PC5 reference point.

[0054] - Authorization for the UE to act as a 5G ProSe inter-UE relay also authorizes the use of 5G ProSe inter-UE relay discovery with Model A and Model B.

[0055] NOTE 1: The choice of discovery model or whether to perform both models simultaneously depends on the UE and application implementation.

[0056] 2) ProSe relay discovery strategy / parameters for 5G ProSe inter-UE relay:

[0057] - Contains parameters that enable the UE to perform 5G ProSe Inter-UE Relay Discovery when provided by the PCF or provisioned in the ME or configured in the UICC:

[0058] -5G ProSe inter-UE relay discovery parameters (user information ID, relay service code, inter-UE relay layer indicator). The inter-UE relay layer indicator indicates whether the associated RSC provides 5G ProSe layer 2 or layer 3 inter-UE relay service.

[0059] - The preset destination layer 2 ID for sending relay discovery notification messages and receiving relay discovery solicitation messages;

[0060] - a preset destination Layer 2 ID for sending / receiving a direct communication request message for ProSe inter-UE relay communication integrated with discovery;

[0061] - For 5G ProSe layer 3 inter-UE relay, the service type (IP, Ethernet, unstructured) of the relay service to be used for each relay service code;

[0062] -Contains security related content for relay discovery for each relay service code.

[0063] NOTE 2: SAWG3 will determine the security related aspects of 5G ProSe inter-UE relay.

[0064] 3) The validity time indicates the expiration time of the policy / parameters used for 5G ProSe inter-UE relay discovery and communication.

[0065] The following information is provisioned in the UE to support the UE assuming the role of 5G ProSe end UE and thereby enable the use of 5G ProSe inter-UE relay:

[0066] 1) Authorization policy for using 5G ProSe Layer 3 and / or Layer 2 inter-UE relay:

[0067] -Whether the UE is authorized to use 5G ProSe Layer 3 and / or Layer 2 inter-UE relay.

[0068] The authorization of the UE to act as a 5G ProSe end UE also authorizes the use of 5G ProSe inter-UE relay discovery with Model A and Model B.

[0069] NOTE 3: The choice of discovery model or whether to perform both models simultaneously depends on the UE and application implementation.

[0070] 2) 5G ProSe inter-UE relay discovery strategy / parameters:

[0071] - When provided by the PCF or provisioned in the ME or configured in the UICC, contains parameters for 5G ProSe Inter-UE Relay discovery as a 5G ProSe end UE and for enabling the UE to connect to the 5G ProSe Inter-UE Relay after discovery:

[0072] -5G ProSe inter-UE relay discovery parameters (user information ID, relay service code, inter-UE relay layer indicator). The inter-UE relay layer indicator indicates whether the associated RSC provides 5G ProSe layer 2 or layer 3 inter-UE relay service.

[0073] - A preset destination layer 2 ID for sending relay discovery solicitation messages and receiving relay discovery notification messages;

[0074] - a preset destination Layer 2 ID for sending / receiving a direct communication request message for ProSe inter-UE relay communication integrated with discovery;

[0075] - For 5G ProSe layer 3 inter-UE relay, the service type (IP, Ethernet, unstructured) of the relay service to be used for each relay service code;

[0076] -Contains security related content for relay discovery for each relay service code.

[0077] NOTE 4: SAWG3 will determine the security related aspects of 5G ProSe inter-UE relay.

[0078] 3) The validity time indicates the expiration time of the policy / parameters used for 5G ProSe inter-UE relay discovery and communication.

[0079] The following information is provisioned in the UE to support the UE assuming the role of 5G ProSe inter-UE relay, and the following information is provisioned in the UE to support the UE assuming the role of 5G ProSe end UE, and thereby enables the use of 5G ProSe inter-UE relay:

[0080] 1) Radio parameters for 5G ProSe inter-UE relay discovery when the UE is not “served by NG-RAN”:

[0081] -Contains radio parameters for NR PC5 with a geographical area, and an indication of whether the radio parameters are "operator managed" or "non-operator managed". The UE uses the radio parameters to perform 5G ProSe direct discovery over the PC5 reference point when "not served by NG-RAN" only if the UE can reliably locate itself in the corresponding geographical area. Otherwise, the UE is not authorized to transmit.

[0082] - Preset PC5 DRX configuration (see TS 38.331

[16] ).

[0083] NOTE 5: RAN WG2 will determine the default PC5 DRX configuration for 5G ProSe inter-UE relay scenarios.

[0084] NOTE 6: It is expected that the radio parameters used for 5G ProSe inter-UE relay discovery when the UE is not “served by NG-RAN” and the radio parameters used for 5G ProSe direct discovery in clause 5.1.2.1 when the UE is “not served by NG-RAN” are aligned for direct and relay discovery for inter-UE communication.

[0085] 2) Radio parameters for 5G ProSe inter-UE relay communications when the UE is not “served by NG-RAN”:

[0086] -Contains radio parameters for NR PC5 with a geographical area, and an indication of whether the radio parameters are "operator managed" or "non-operator managed". The UE uses the radio parameters to perform 5G ProSe direct communication over the PC5 reference point when "not served by NG-RAN" only if the UE can reliably locate itself in the corresponding geographical area. Otherwise, the UE is not authorized to transmit.

[0087] NOTE 7: It is expected that the radio parameters used for 5G ProSe inter-UE relay communication when the UE is not “served by NG-RAN” and the radio parameters used for 5G ProSe direct communication in clause 5.1.3.1 when the UE is “not served by NG-RAN” are aligned for direct and relay inter-UE communication.

[0088] […]

[0089] 6.3.2 5G ProSe direct discovery procedure over PC5 reference point

[0090] 6.3.2.1 Overview

[0091] The PC5 communication channel is used to carry discovery messages on the PC5, and the discovery messages on the PC5 are distinguished from other PC5 messages by the AS layer.

[0092] Supports both Model A and Model B discovery as defined in TS 23.303 [3]:

[0093] - Model A uses a single discovery protocol message (Notify).

[0094] - Model B uses two discovery protocol messages (solicit and response).

[0095] Figure 6 The procedure for 5G ProSe direct discovery with Model A is described in .3.2.1-1.

[0096] [3GPP TS 23.304 V18.2.0 titled "5G ProSe direct discovery with Model A" Figure 6 .3.2.1-1 Reproduced as Figure 6 ]

[0097] 1. Notify the UE to send a notification message. The notification message may include the type of discovery message, ProSe application code or ProSe restricted code, relay_Indication, security protection element, and [metadata information]. The application layer metadata information may be included in the notification message as metadata.

[0098] The destination Layer 2 ID and source Layer 2 ID used to send the notification message are specified in clauses 5.8.1.2 and 5.8.1.3.

[0099] If the 5G ProSe inter-UE relay can broadcast its user information ID during 5G ProSe inter-UE discovery, the notification UE includes relay_Indication.

[0100] The listening UE determines the destination Layer 2 ID for signaling reception. The destination Layer 2 ID is configured with the UE as specified in clause 5.8.2.1.

[0101] Figure 6 The procedure for 5G ProSe direct discovery with Model B is described in .3.2.1-2.

[0102] [3GPP TS TS23.304 V18.2.0 titled "5G ProSe Direct Discovery with Model B" Figure 6 .3.2.1-2 is reproduced as Figure 7 ]

[0103] 1. The discoverer UE sends a request message. The request message may include the type of discovery message, ProSe query code, relay_Indication, and security protection element.

[0104] The destination Layer 2 ID and source Layer 2 ID used to send the solicitation message are specified in clauses 5.8.1.2 and 5.8.1.3.

[0105] How the discoverer UE determines the destination Layer 2 ID for signalling reception is specified in clause 5.8.1.2.

[0106] If the 5G ProSe inter-UE relay can broadcast its user information ID during 5G ProSe inter-UE discovery, the discoverer UE includes relay_Indication.

[0107] 2. The discoverer UE that matches the solicitation message responds to the discoverer UE using a response message. The response message may include the type of discovery message, ProSe response code, relay_Indication, security protection element, and [metadata information]. The application layer metadata information may be included in the response message as metadata.

[0108] If the 5G ProSe inter-UE relay can broadcast its user information ID during 5G ProSe inter-UE discovery, the discovered UE includes relay_Indication.

[0109] The source Layer 2ID used to send the response message is specified in clause 5.8.1.3. The destination Layer 2ID is set to the source Layer 2ID of the received solicitation message.

[0110] NOTE: Details of security protection elements are specified in TS 33.503

[29] .

[0111] […]

[0112] 6.3.2.4 5G ProSe Inter-UE Relay Discovery

[0113] 6.3.2.4.1 Overview

[0114] 5G ProSe inter-UE relay discovery is applicable to both 5G ProSe layer 3 and layer 2 inter-UE relay discovery for public safety use and commercial services. To perform 5G ProSe inter-UE relay discovery, the 5G ProSe-side UE and the 5G ProSe inter-UE relay are pre-configured or provisioned with relevant information as described in clause 5.1.

[0115] A Relay Service Code (RSC) is used for 5G ProSe inter-UE relay discovery to indicate the connectivity service provided by the 5G ProSe inter-UE relay to the 5G ProSe end UE. The RSC is pre-configured or provisioned on the 5G ProSe inter-UE relay and the 5G ProSe end UE as defined in clause 5.1. The 5G ProSe inter-UE relay and the 5G ProSe end UE know whether the RSC is providing 5G ProSe layer 2 or layer 3 inter-UE relay service based on the policy as specified in clause 5.1. A 5G ProSe inter-UE relay supporting multiple RSCs advertises the RSCs using multiple discovery messages with one RSC per discovery message.

[0116] 6.3.2.4.2 Procedure for 5G ProSe inter-UE relay discovery with Model A

[0117] Figure 6 The procedure for 5G ProSe inter-UE discovery with Model A is described in .3.2.4.2-1.

[0118] [3GPP TS 23.304 V18.2.0 titled "5G ProSe Inter-UE Relay Discovery with Model A" Figure 6.3.2.4.2-1 Reproduced as Figure 8 ]

[0119] 1. The 5G ProSe inter-UE relay has discovered other neighboring UEs (eg, via a previous 5G ProSe inter-UE relay discovery or 5G ProSe inter-UE relay communication procedure). The 5G ProSe inter-UE relay obtains the user information ID of other neighboring UEs according to the RSC.

[0120] 2.5G ProSe Inter-UE Relay sends Inter-UE Relay Discovery Notification message. The Inter-UE Relay Discovery Notification message contains the type of discovery message, the user information ID of the 5G ProSe Inter-UE Relay, the RSC and the user information ID list of the 5G ProSe end UE, and is sent using the source layer 2 ID and the destination layer 2 ID, as described in clause 5.8.4.

[0121] 5G ProSe inter-UE relay will only notify the user information ID of other UEs in the vicinity that provided relay_indication when previously discovered.

[0122] The 5G ProSe UE listens to the notification message from the 5G ProSe inter-UE relay. The 5G ProSe UE determines the destination layer 2 ID for signaling reception as specified in clause 5.1.

[0123] 6.3.2.4.3 Procedure for 5G ProSe inter-UE relay discovery with Model B

[0124] Figure 6 The procedure for 5G ProSe inter-UE relay discovery with Model B is described in .3.2.4.3-1.

[0125] [3GPP TS 23.304 V18.2.0 entitled "5G ProSe Inter-UE Relay Discovery with Model B" Figure 6 .3.2.4.3-1 Reproduced as Fig. 9 ]

[0126] 1. The discoverer 5G ProSe UE (UE-1) sends a 5G ProSe inter-UE relay discovery request message. The 5G ProSe inter-UE relay discovery request message contains the type of discovery message, its own user information ID, RSC and the user information ID of the discoverer 5G ProSe UE (UE-2), and is sent using the source layer 2 ID and the destination layer 2 ID, as described in clause 5.8.4.

[0127] The 5G ProSe Inter-UE Relay determines the destination Layer 2 ID for signaling reception as specified in clause 5.1.

[0128] 2. The 5G ProSe inter-UE relay matching the RSC sends a 5G ProSe inter-UE relay discovery solicitation message. The 5G ProSe inter-UE relay discovery solicitation message contains the type of discovery message, the user information ID of the discoverer 5G ProSe end UE (UE-1), the user information ID of the inter-UE relay, the RSC and the user information ID of the discoverer 5G ProSe end UE (UE-2), and is sent using the source layer 2 ID and the destination layer 2 ID, as described in clause 5.8.4.

[0129] The 5G ProSe-side UE determines the destination Layer 2 ID for signaling reception as specified in clause 5.1.

[0130] 3. The discoverer 5G ProSe end UE (UE2) matching the value of RSC and the user information ID of the discoverer 5G ProSe end UE (UE2) responds to the 5G ProSe inter-UE relay with a 5G ProSe inter-UE relay discovery response message. The 5G ProSe inter-UE relay discovery response message contains the type of discovery message, RSC, the user information ID of the discoverer 5G ProSe end UE (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 discoverer 5G ProSe end UE (UE2) receives multiple inter-UE relay discovery solicitation messages from different 5G ProSe inter-UE relays, it may choose to respond or not to respond to the 5G ProSe inter-UE relay (e.g., based on the PC5 signal strength of each message received).

[0131] 4.5G ProSe Inter-UE Relay sends a 5G ProSe Inter-UE Relay Discovery Response message. The 5G ProSe Inter-UE Relay Discovery Response message contains the type of discovery message, the user information ID of the Inter-UE Relay, the RSC and the user information ID of the discovered 5G ProSe end UE (UE-2), and is sent using the source layer 2 ID and the destination layer 2 ID, as described in clause 5.8.4.

[0132] […]

[0133] 6.4.3.1 Layer 2 link establishment over PC5 reference point

[0134] To perform unicast mode of ProSe direct communication over PC5 reference point, the UE is configured with relevant information as described in clause 5.1.3.

[0135] Figure 6 .4.3.1-1 shows the Layer 2 link establishment procedure for unicast mode of ProSe direct communication over PC5 reference point.

[0136] [3GPP TS 23.304 V18.2.0 entitled "Layer 2 Link Establishment Procedure" Figure 6 .4.3.1-1 Reproduced as Fig.10 ]

[0137] 1. The UE determines the destination Layer 2 ID for signalling reception for PC5 unicast link establishment as specified in clause 5.8.2.4.

[0138] 2. 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 UE. The application information may include the application layer ID of the target UE.

[0139] The ProSe application layer in UE-1 may provide the ProSe application requirements for this unicast communication.UE-1 determines the PC5 QoS parameters and PFI as specified in clause 5.6.1.

[0140] If UE-1 decides to reuse the existing PC5 unicast link as specified in clause 5.3.4, the UE triggers the Layer 2 Link Modification procedure as specified in clause 6.4.3.4.

[0141] 3. UE-1 sends a direct communication request message to initiate the unicast layer 2 link establishment procedure. The direct communication request message contains:

[0142] - Source user information: the application layer ID of the originating UE (ie, the application layer ID of UE-1).

[0143] - If the ProSe application layer provides the application layer ID of the target UE in step 2, the following information is included:

[0144] - Target user information: Application layer ID of the target UE (ie, the application layer ID of UE-2).

[0145] -ProSe service information: Information about the ProSe identifier requesting Layer 2 link establishment.

[0146] - Security information: information used to establish security.

[0147] NOTE 1 Security information and the necessary protection of source and destination user information are defined by SAWG3.

[0148] Determine the source layer 2 ID and destination layer 2 ID used to send the direct communication request message, as specified in clauses 5.8.2.1 and 5.8.2.4. The destination layer 2 ID can be a broadcast or unicast layer 2 ID. When a unicast layer 2 ID is used, the target user information shall be included in the direct communication request message.

[0149] UE-1 transmits a direct communication request message through PC5 which is broadcast or unicast using the source layer 2 ID and the destination layer 2 ID.

[0150] The default PC5 DRX configuration may be used to transmit and receive this message (see TS 38.300

[12] ).

[0151] 4. Establish security for UE-1 as follows:

[0152] 4a. If the target user information is included in the direct communication request message, the target UE, ie, UE-2, responds by establishing security with UE-1.

[0153] 4b. If the target user information is not included in the direct communication request message, the UE interested in using the notified ProSe service over the PC5 unicast link with UE-1 responds by establishing security with UE-1.

[0154] NOTE 2 Signalling for security procedures is defined by SAWG3.

[0155] When security protection is enabled, UE-1 sends the following information to the target UE:

[0156] - If using IP communication, then:

[0157] -IP address configuration: For IP communication, this link requires an IP address configuration, and the IP address configuration indicates one of the following values:

[0158] - "DHCPv4 server", if only IPv4 address allocation mechanism is supported by the initiating UE, i.e. acting as a DHCPv4 server; or

[0159] - "IPv6 router", if only the IPv6 address allocation mechanism is supported by the originating UE, i.e. acting as an IPv6 router; or

[0160] - "DHCPv4 server and IPv6 router", if both IPv4 and IPv6 address allocation mechanisms are supported by the initiating UE; or

[0161] - "Address allocation not supported" if both IPv4 and IPv6 address allocation mechanisms are not supported by the originating UE.

[0162] - 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", a link-local IPv6 address is formed locally based on RFC 4862

[17] .

[0163] - QoS Information: Information about PC5 QoS flows. For each PC5 QoS flow, the PFI and corresponding PC5 QoS parameters (ie, PQI and conditionally other parameters such as MFBR / GFBR) and the associated ProSe identifier.

[0164] -Optional PC5 QoS rules.

[0165] Determine the Source Layer 2 ID for the security establishment procedure 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.

[0166] Upon receiving the Security Setup Procedure message, UE-1 obtains the Layer 2 ID of the peer UE for future communications for signaling and data traffic for this unicast link.

[0167] 5. The target UE, which has successfully established security with UE-1, sends a direct communication acceptance message to UE-1:

[0168] 5a. (Layer 2 link establishment towards UE) If the target user information is contained in the direct communication request message, the target UE (ie, UE-2) responds with a direct communication accept message if the application layer ID for UE-2 matches.

[0169] 5b. (Layer 2 Link Establishment for ProSe Services) If the direct communication request message does not contain target user information, the UE interested in using the notified ProSe service (in Figure 6 .UE-2 and UE-4 in 4.3.1-1) respond to the request by sending a direct communication accept message.

[0170] The direct communication acceptance message contains:

[0171] -Source user information: the application layer ID of the UE that sends the direct communication acceptance message.

[0172] - QoS Information: Information about PC5 QoS flows. For each PC5 QoS flow, the PFI requested by UE-1 and the corresponding PC5 QoS parameters (ie PQI and conditionally other parameters such as MFBR / GFBR) and optionally the associated ProSe identifier.

[0173] -Optional PC5 QoS rules.

[0174] - If using IP communication, then:

[0175] -IP address configuration: For IP communication, this link requires an IP address configuration, and the IP address configuration indicates one of the following values:

[0176] - "DHCPv4 Server", if only IPv4 address allocation mechanism is supported by the target UE, i.e. act as a DHCPv4 server; or

[0177] - "IPv6 router", if the IPv6 address allocation mechanism is supported by the target UE, i.e. act as an IPv6 router; or

[0178] - "DHCPv4 server and IPv6 router", if both IPv4 and IPv6 address allocation mechanisms are supported by the target UE; or

[0179] - "Address allocation not supported" if both IPv4 and IPv6 address allocation mechanisms are not supported by the target UE.

[0180] - Link-local IPv6 address: 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 a link-local IPv6 address in the Direct Communication Request message, a link-local IPv6 address is formed locally based on RFC4862

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

[0181] If both UEs (ie, the initiating UE and the target UE) are selected to use link-local IPv6 addresses, they shall disable dual address detection as defined in RFC4862

[17] .

[0182] NOTE 3: When the initiating UE or the target UE indicates support for IPv6 routing, the corresponding address configuration procedure shall be performed after the Layer 2 link is established and the link-local IPv6 address shall be ignored.

[0183] The ProSe layer of the UE that establishes the PC5 unicast link passes the PC5 link identifier and PC5 unicast link related information allocated for the unicast link downward to the AS layer. The PC5 unicast link related information includes layer 2ID information (i.e., source layer 2ID and destination layer 2ID). This enables the AS layer to save the PC5 link identifier and PC5 unicast link related information.

[0184] Two UEs may negotiate the PC5 DRX configuration in the AS layer, and the PC5 DRX parameter value may be configured according to a pair of source / destination layer 2 IDs in the AS layer.

[0185] 6. ProSe data is transmitted over the established unicast link as follows:

[0186] The PC5 link identifier and PFI are provided to the AS layer together with the ProSe data.

[0187] Additionally, layer 2 ID information (ie, source layer 2 ID and destination layer 2 ID) is optionally provided to the AS layer.

[0188] NOTE 4: Providing the Layer 2 ID information to the AS layer is up to the UE implementation.

[0189] UE-1 sends ProSe data using a source Layer 2 ID (ie, the Layer 2 ID of UE-1 for this unicast link) and a destination Layer 2 ID (ie, the Layer 2 ID of the peer UE for this unicast link).

[0190] NOTE 5: The PC5 unicast link is bidirectional, so UE-1's peer UE can send ProSe data to UE-1 via the unicast link with UE-1.

[0191] […]

[0192] 6.4.3.7 Layer 2 Link Management over PC5 Reference Point for 5G ProSe Inter-UE Relay

[0193] 6.4.3.7.1 Common part for Layer 2 link management over PC5 reference point for 5G ProSe inter-UE relay

[0194] For 5G ProSe communication via 5G ProSe inter-UE relay as described in clauses 6.7.1 and 6.7.2:

[0195] -The direct communication request message on the first hop PC5 reference point contains:

[0196] -User information ID of the source 5G ProSe UE: the identity of the source 5G ProSe UE requesting the relay operation (i.e., the user information ID).

[0197] - User Information ID of 5G ProSe Inter-UE Relay: The identity of the Inter-UE Relay (i.e., User Information ID) provided to the source 5G ProSe end UE during the 5G ProSe Inter-UE Relay discovery procedure.

[0198] - User Information ID of target 5G ProSe UE: The identity of the target 5G ProSe UE (i.e., User Information ID) provided to the source 5G ProSe UE during the inter-UE relay discovery procedure.

[0199] - (Optional) Destination Layer 2 ID of 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.

[0200] -ProSe service information: Information about the ProSe identifier requesting Layer 2 link establishment.

[0201] -RSC: Connectivity service requested by the source 5G ProSe UE and provided by the 5G ProSe inter-UE relay.

[0202] - Security information: Information used to establish security for first-hop PC5 link establishment.

[0203] NOTE 1 Security information is defined by SAWG3.

[0204] The direct communication request message on the second hop PC5 reference point contains:

[0205] -User information ID of the source 5G ProSe UE.

[0206] -User information ID of the target 5G ProSe UE.

[0207] -User information ID relayed between 5G ProSe UEs.

[0208] -ProSe service information: information about the ProSe identifier.

[0209] -RSC: Connectivity service requested by the source 5G ProSe UE and provided by the 5G ProSe inter-UE relay.

[0210] - Security information: information used to establish security for the second hop PC5 link establishment.

[0211] NOTE 2 Security information is defined by SAWG3.

[0212] The direct communication acceptance message on the second hop PC5 reference point contains:

[0213] -User information ID of the target 5G ProSe UE.

[0214] The direct communication acceptance message on the first hop PC5 reference point contains:

[0215] -User information ID of the target 5G ProSe UE.

[0216] -User information ID relayed between 5G ProSe UEs.

[0217] The link modification request message on the first hop PC5 reference point contains:

[0218] - User Information ID of target 5G ProSe UE: The identity of the target 5G ProSe UE provided to the source 5G ProSe UE during the inter-UE relay discovery procedure.

[0219] - (Optional) Destination Layer 2 ID of 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.

[0220] The link modification request message on the second hop PC5 reference point contains:

[0221] -User information ID of the source 5G ProSe UE.

[0222] -User information ID of the target 5G ProSe UE.

[0223] The link modification acceptance message on the second hop PC5 reference point contains:

[0224] -User information ID of the target 5G ProSe UE.

[0225] The link modification acceptance message on the first hop PC5 reference point contains:

[0226] -User information ID of the target 5G ProSe UE.

[0227] 6.4.3.7.2 Layer 2 Link Management over PC5 Reference Point for 5G ProSe Layer 2 Inter-UE Relay

[0228] For 5G ProSe communication via 5G ProSe layer 2 inter-UE relay as described in section 6.7.2, the description in clause 6.4.3.7.1 applies.

[0229] The message contents over the PC5 reference point for unicast mode 5G ProSe direct communication described in clauses 6.4.3.1 to 6.4.3.5 are the same for end-to-end connections between peer 5G ProSe end UEs.

[0230] […]

[0231] 6.4.3.7.4 Layer 2 link management over PC5 reference point for 5G ProSe inter-UE relay communication integrated with discovery This clause targets 5G ProSe inter-UE relay communication integrated with discovery procedure, as described in clause 6.7.3.

[0232] The direct communication request message on the first hop PC5 reference point contains:

[0233] -User information ID of the source 5G ProSe UE.

[0234] - (Optional) User Information ID of target 5G ProSe UE: the identity of the target 5G ProSe UE (if provided from the ProSe application layer).

[0235] - (Optional) Destination Layer 2 ID of 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.

[0236] -ProSe service information: Information about the ProSe identifier requesting Layer 2 link establishment.

[0237] -RSC: Connectivity service requested by the source 5G ProSe UE and provided by the 5G ProSe inter-UE relay.

[0238] -Relay_indication: indicates whether the direct communication request message can be forwarded by the 5G ProSe inter-UE relay.

[0239] - Security information: Information used to establish security for first-hop PC5 link establishment.

[0240] NOTE 1 Security information is defined by SA WG3.

[0241] The direct communication request message on the second hop PC5 reference point contains:

[0242] -User information ID of the source 5G ProSe UE.

[0243] -User information ID relayed between 5G ProSe UEs.

[0244] -(Optional) User information ID of the target 5G ProSe UE.

[0245] -ProSe service information: information about the ProSe identifier.

[0246] -RSC: Connectivity service requested by the source 5G ProSe UE and provided by the 5G ProSe inter-UE relay.

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

[0248] NOTE 2 Security information is defined by SA WG3.

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

[0250] -User information ID of the target 5G ProSe UE.

[0251] The direct communication acceptance message on the first hop PC5 reference point contains:

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

[0253] -User information ID relayed between 5G ProSe UEs.

[0254] For 5G ProSe communication via 5G ProSe layer 3 inter-UE relay, additional explanations are as follows:

[0255] -In the security procedure of the second-hop PC5 reference point, the 5G ProSe layer 3 inter-UE relay provides the IP address configuration or link-local IPv6 address to the target 5G ProSe end UE.

[0256] - The Direct Communication Accept message over the second hop PC5 reference point additionally includes the IP address configuration or link-local IPv6 address (if IP communication is used), the Ethernet MAC address of the target 5G ProSe end UE (if Ethernet communication is used). QoS information is not included in the security procedures or the Direct Communication Accept message over the second hop PC5 reference point.

[0257] - In the security procedure of the first-hop PC5 reference point, the source 5G ProSe end UE provides the 5G ProSe layer 3 inter-UE relay with IP address configuration, link-local IPv6 address and QoS information of end-to-end QoS.

[0258] -5G ProSe Layer 3 Inter-UE Relay provides QoS information of the second-hop QoS to the target 5G ProSe end UE using Layer 2 Link Modification as described in clause 6.4.3.4.

[0259] - Considering that the second-hop QoS is received from the target 5G ProSe end UE, the 5G ProSe layer 3 inter-UE relay determines the QoS information of the first-hop QoS, and the direct communication accept message on the first-hop PC5 reference point additionally includes the IP address configuration or link-local IPv6 address, the QoS information of the first-hop QoS, and may include the IP address of the target 5G ProSe end UE (if IP communication is used) or the Ethernet MAC address of the target 5G ProSe end UE (if Ethernet communication is used).

[0260] For 5G ProSe communication via 5G ProSe layer 2 inter-UE relay, the message contents over the PC5 reference point for unicast mode 5G ProSe direct communication described in clauses 6.4.3.1 to 6.4.3.5 are the same for end-to-end connections between peer 5G ProSe end UEs.

[0261] […]

[0262] 6.7.3 5G ProSe Inter-UE Relay Communication with Integrated Discovery

[0263] 6.7.3.1 Overview

[0264] Supports 5G ProSe communication via 5G ProSe inter-UE relay with integrated discovery.

[0265] For 5G ProSe inter-UE relay communication integrated with discovery, when the UE allows inter-UE relay to be involved in direct communication requests for other UEs, the UE indicates this by including relay_indication in the broadcast direct communication request message.

[0266] 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), application ID, operator policy for each relay service code, signal strength, and local policy.

[0267] 6.7.3.2 Procedures for communication via layer 3 inter-UE relay

[0268] [3GPP TS 23.304 V18.2.0 entitled "5G ProSe inter-UE relay communication with integrated discovery via Layer 3 inter-UE relay" Figure 6 .7.3.2-1 Reproduced as Fig.11 ]

[0269] 0.5G ProSe end UE is authorized and equipped with parameters to use the service provided by 5G ProSe inter-UE relay. 5G ProSe inter-UE relay is authorized and equipped with parameters to provide the service of relaying traffic among 5G ProSe end UEs.

[0270] 1. The source 5G ProSe end UE (ie, UE1) wants to establish unicast communication with the target 5G ProSe end UE (ie, UE2) and broadcasts a direct communication request. The parameters included in the direct communication request message are described in clause 6.4.3.7.

[0271] The relay_indication in the direct communication request is used to indicate whether the 5G ProSe inter-UE relay can forward the direct communication request message. It is also used to limit the number of hops of the 5G ProSe inter-UE relay by removing the relay_indication in the direct communication request message from the 5G ProSe inter-UE relay.

[0272] The source layer 2 ID and destination layer 2 ID for the direct communication request message are defined in clause 5.8.5.

[0273] NOTE 1: The data type of relay_indication can be determined in phase 3.

[0274] 2. When receiving a direct communication request with relay_indication from UE-1, the 5G ProSe inter-UE relays (i.e., Relay 1 and Relay 2) may decide to participate in the procedure and broadcast a direct communication request message in its vicinity without relay_indication. The parameters included in the direct communication request message are described in clause 6.4.3.7.

[0275] The source layer 2 ID and destination layer 2 ID for the direct communication request message are defined in clause 5.8.5.

[0276] 3. When UE-2 receives a direct communication request from one or more 5G ProSe inter-UE relays, UE-2 selects a 5G ProSe inter-UE relay to which UE-2 will respond. UE-2 may select a 5G ProSe inter-UE relay based on, for example, signal strength, local policy, operator policy for each relay service code (if any).

[0277] 4. If required, security establishment occurs between UE-2 and the selected 5G ProSe Inter-UE Relay (here Relay 1).

[0278] If an existing PC5 link can be reused, Link Modification Request and Link Modification Accept messages are used.

[0279] NOTE 2: Conflicts between link modification requests and direct communication requests may be determined in Phase 3.

[0280] 5. UE-2 replies a direct communication accept message to Relay 1. The parameters included in the direct communication accept message are described in clause 6.4.3.7.

[0281] 6. For IP services, an IPv6 prefix or IPv4 address is allocated to the target 5G ProSe layer 3 end UE as defined in clause 5.5.1.4.

[0282] 7. If required, security establishment occurs between UE-1 and Relay 1.

[0283] 8. For 5G ProSe inter-UE relay communication with integrated discovery, after receiving the QoS information of end-to-end QoS from UE-1, Relay 1 provides QoS information of second-hop QoS to UE-2 using a Link Modification Request message.

[0284] 9. For 5G ProSe inter-UE relay communication with integrated discovery, UE-2 responds with a Link Modification Accept message.

[0285] 10. Relay 1 responds to UE-1 with a Direct Communication Accept. The parameters included in the Direct Communication Accept message are described in clause 6.4.3.7.

[0286] 11. For IP services, an IPv6 prefix or IPv4 address is allocated to the source 5G ProSe layer 3 end UE as defined in clause 5.5.1.4.

[0287] 12. For IP communication, the 5G ProSe layer 3 inter-UE relay may store the association of the user information ID with the IP address of the target 5G ProSe layer 3 end UE in its DNS entry, and the 5G ProSe layer 3 inter-UE relay may 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, the source 5G ProSe layer 3 end UE may send a DNS query to the 5G ProSe layer 3 inter-UE relay after step 11 to request the IP address of the target 5G ProSe layer 3 end UE, and the 5G ProSe layer 3 inter-UE relay returns the IP address of the target 5G ProSe layer 3 end UE to the source 5G ProSe layer 3 end UE.

[0288] For Ethernet communication, the 5G ProSe Layer 3 inter-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.

[0289] For unstructured traffic communications, for each pair of source and target 5G ProSe layer 3 end UEs, the 5G ProSe layer 3 inter-UE relay maintains a 1:1 mapping between the PC5 link with the source 5G ProSe layer 3 end UE and the PC5 link with the target 5G ProSe layer 3 end UE.

[0290] The source 5G ProSe layer 3 end UE communicates with the target 5G ProSe layer 3 end UE via a 5G ProSe layer 3 inter-UE relay.

[0291] 6.7.3.3 Procedures for communication via layer 2 inter-UE relay

[0292] [3GPP TS 23.304 V18.2.0 entitled "5G ProSe inter-UE relay communication with integrated discovery via Layer 2 inter-UE relay" Figure 6 .7.3.3-1 Reproduced as Fig.12 ]

[0293] Step 0-Step 5 and Figure 6 .7.3.2-1 steps 0 to 5 are the same. Step 6 is the same as Figure 6 .7.3.2-1 step 7 is the same as Figure 6 .7.3.2-1, step 10. The parameters contained in the message are described in clause 6.4.3.7.

[0294] 8. For 5G ProSe inter-UE relay communication via Layer 2 inter-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.

[0295] Editor's Note: Any additional updates on procedures via Layer 2 Inter-UE Relay, such as updates based on RAN decisions, will be included here.

[0296] Section 6.2.14.2 of 3GPP TS24.554 specifies that the UE may include a relay indication in a PROSE PC5 DISCOVERY message (e.g., direct discovery notification, direct discovery solicitation, direct discovery response) to indicate whether the 5G ProSe inter-UE relay UE may broadcast its user information ID during the procedure of 5G ProSe inter-UE relay discovery over the PC5 interface if the UE may act as a 5G ProSe end UE. In addition, according to section 7.2.2.2 of 3GPP TS24.554, if the UE may act as a 5G ProSe end UE, the relay indication may be included in the PROSE DIRECT LINK ESTABLISHMENT REQUEST message to indicate whether the 5G ProSe inter-UE relay UE may broadcast its user information ID during the procedure of 5G ProSe direct link establishment procedure (with discovery integrated) over the PC5 interface. The Relay Indication (RI) contained in these messages is a one-bit value as described in section 11.2.16 of 3GPP TS 24.554 as follows:

[0297] 11.2.16 Relay Instructions

[0298] The Relay Indication parameter is used to indicate whether the 5G ProSe inter-UE relay UE can re-broadcast the user information ID of the UE that generates the corresponding message containing the relay indication during the 5G ProSe inter-UE relay discovery procedure performed through the PC5 interface.

[0299] The Relay Indication is a Type 1 information element with a length of 1 octet.

[0300] Relay Indication IE Fig.11 .2.y.1 and the encoding shown in Table 11.2.y.1.

[0301] [3GPP TS 24.554 V18.1.0 entitled "Relay Indication Information Element" Fig.11 .2.y.1 reproduces as Fig.13 ]

[0302] [Table 11.2.y.1 entitled "Relay Indication Information Element" in 3GPP TS 24.554 V18.1.0 is reproduced as Fig.14 ]

[0303] 3GPP TS22.261 specifies the connectivity model and KPIs for UE to network relay in 5G systems as follows:

[0304] 6.9 Connectivity Model

[0305] 6.9.1 Description

[0306] A UE (remote UE) can be connected directly to the network (direct network connection), connected using another UE as a relay UE (indirect network connection), or connected using both direct and indirect connections. Relay UEs can be used in many different scenarios and verticals (inHome, SmartFarming, SmartFactories, public safety, etc.). In these cases, the use of relay UEs can be used to improve the energy efficiency and coverage of the system.

[0307] The remote UE can be anything from a simple wearable, such as a sensor embedded in clothing, to a more complex wearable UE listening to biometrics. It can also be a non-wearable UE communicating in a personal area network, such as a group of home appliances (e.g., a smart thermostat and input keys), or an electronic UE in an office environment (e.g., a smart printer), or a smart flower pot that can be remotely activated to water a plant.

[0308] When a remote UE attempts to establish an indirect network connection, there may be several available relay UEs in the vicinity, and a procedure for selecting a suitable relay UE among the available relay UEs needs to be supported.

[0309] Indirect network connection covers the use of relay UEs for connecting remote UEs to the 3GPP network. There may be one or more relay UEs (more than one hop) between the network and the remote UE.

[0310] The ProSe Inter-UE Relay may also be used to connect two remote Public Safety UEs using a direct device connection.There may be one or more ProSe Inter-UE Relays (more than one hop) between two remote Public Safety UEs.

[0311] 6.9.2 Requirements

[0312] The following set of requirements supplements the requirements listed in 3GPP TS 22.278 [5], clauses 7B and 7C.

[0313] 6.9.2.1 Overview

[0314] The 5G system will support the use of one or more relay UEs to relay services between remote UEs and gNBs.

[0315] The 5G system will support the same traffic flow of remote UEs to be relayed via different indirect network connection paths.

[0316] The 5G system will support different service flows of remote UEs to be relayed via different indirect network connection paths.

[0317] The connection between the remote UE and the relay UE will be able to use 3GPP RAT or non-3GPP RAT and use licensed or unlicensed frequency bands.

[0318] The connection between the remote UE and the relay UE will be able to use fixed broadband technology.

[0319] When the remote UE and the relay UE subscribe to different PLMNs and both PLMNs have roaming agreements with the VPLMN, the 5G system will support the indirect network connection mode in the VPLMN.

[0320] The 5G system will be able to support UEs using simultaneous indirect and direct network connection modes.

[0321] When using relay UEs, network operators will be able to define the maximum number of hops supported in their network.

[0322] The 5G system will be able to manage communications between remote UEs and the 5G network across multi-path indirect network connections.

[0323] 3GPP TS23.304 introduced inter-UE relay in Release 18. For single-hop inter-UE relay, the inter-UE relay can be used to support data communication between two remote UEs when the two remote UEs cannot communicate directly with each other. The inter-UE relay needs to establish a PC5 unicast link (or PC5 RRC connection) with each of the source remote UE and the target remote UE. In the case of layer 2 inter-UE relay, after the first two PC5 unicast links have been established between the inter-UE relay and the two remote UEs, an end-to-end link (or connection) for unicast communication can be established between the two remote UEs.

[0324] According to 3GPP TS22.261, multi-hop inter-UE relay may be supported in Release 19. Fig.15 An exemplary 3-hop inter-UE relay according to an exemplary embodiment is shown. Also, when using relay UEs, network operators will be able to define the maximum number of hops supported in their network.

[0325] Considering that the more hops are used, the more delay is incurred, it is not suitable for the network to configure one value of the maximum number of hops for services with different quality of service (QoS) requirements. Therefore, it is advantageous that the network configures the maximum number of hops on a service basis. For example, the network may provide the maximum number of hops for each (ProSe) Relay Service Code (RSC) or each (ProSe) service to the relay UE in order to limit the maximum number of hops for multi-hop inter-UE relay. Alternatively, the network may provide a mapping of the maximum number of hops to the (ProSe) RSC or (ProSe) service to the relay UE. It is possible that one or more (ProSe) services may be mapped to one (ProSe) RSC, where the RSC indicates the connectivity service provided by the inter-UE relay to the remote UE. In addition, each (ProSe) service may be identified by an application ID.

[0326] Section 6.7.3 of 3GPP TS23.204 V18.2.0 describes 5G ProSe communication via 5G ProSe inter-UE relay integrated with discovery for single-hop inter-UE relay. Basically, when a remote UE (e.g., UE-1) allows inter-UE relays to be involved in direct communication requests for other remote UEs, the remote UE (UE-1) indicates it by including relay_indication in a broadcasted direct communication request message. When the inter-UE relay receives the direct communication request message including relay_indication, it decides whether to forward the message (more precisely, whether to broadcast the user information of UE-1 in another direct communication request message) based on, for example, a relay service code (if present), an application ID, an operator policy for each relay service code, signal strength, and a local policy. When UE-2 receives a direct communication request message from one or more inter-UE relays, UE-2 can select an inter-UE relay based on signal strength, local policy, and / or an operator policy for each relay service code (if present). UE-2 may then reply to the selected inter-UE relay with a direct communication accept message (after security establishment (if required) between UE-2 and the selected inter-UE relay). Before replying to the direct communication accept message, UE-2 may first initiate a security establishment procedure by transmitting a security mode command to the selected inter-UE relay.

[0327] After receiving the direct communication accept message from UE-2, the inter-UE relay may then transmit another direct communication accept message to UE-1. In the case of a single-hop inter-UE relay, the direct communication request message sent by the inter-UE relay may not include relay_indication. Alternatively, relay_indication may be set to a value indicating that broadcasting of the source UE's user information (or user information ID) is not allowed.

[0328] 3GPP TS.23.304V18.2.0 Figure 6 .Step 1 in 7.3.2-1 also mentions that in the case of multi-hop inter-UE relay, the relay_indication in the direct communication request message can be used to limit the number of hops of the inter-UE relay by removing the relay_indication in the direct communication request message broadcast from the inter-UE relay. To support this, the inter-UE relay is required to include information in the direct communication request message to indicate the cumulative number of hops or relays involved in the multi-hop inter-UE relay. When the maximum (cumulative) number of hops or relays is reached, the receiving inter-UE relay can remove the relay_indication or set the relay_indication to a value indicating that the user information (or user information ID) of the source UE is not allowed to be broadcast.

[0329] This can be a new information element (IE) that indicates the cumulative number of hops or relays involved in a multi-hop inter-UE relay. When transmitting a direct communication request message, the first inter-UE relay may set the cumulative number to 1. And, the second inter-UE relay may set the cumulative number to "2". If the maximum (cumulative) number of hops or relays is 3, the third inter-UE relay may remove relay_indication or set relay_indication to a value (e.g., 0) indicating that broadcasting of the user information (or user information ID) of the source UE is not allowed. In this case, the third inter-UE relay may not include the cumulative number in the direct communication request message. It is also feasible to determine whether to allow broadcasting of the user information (or user information ID) of the source UE only by relying on the cumulative number of hops of the inter-UE relay. For example, if the current cumulative number of hops (i.e., the received cumulative number of hops plus 1) is less than or equal to the maximum number of hops, broadcasting of the user information (or user information ID) of the source UE is allowed. Otherwise, it is not allowed. In the solution, the source UE may not include the cumulative number in the direct communication request message for transmission. Alternatively, the source UE may set the cumulative number to "0" for transmitting the direct communication request message.

[0330] It is also feasible to redefine relay_indication to additionally indicate the cumulative number of hops or relays involved in multi-hop inter-UE relays. More specifically, relay_indication may have two functions:

[0331] (1) One function is to indicate in another direct communication request message whether the inter-UE relay can broadcast the user information of the source UE. For example, relay_indication can be set to a specific value "x" (eg, "0") to indicate that broadcasting of user information (or user information ID) is not allowed.

[0332] (2) Another is to indicate the cumulative number of hops or relays involved in the multi-hop inter-UE relay. For example, relay_indication may be set to a value other than "x" (e.g., "1", "2", "3", etc.) to indicate that broadcasting of user information (or user information ID) is allowed, and considering receiving inter-UE relays, this value also indicates the cumulative number of hops or relays. In this case, when transmitting a direct communication request message, the source UE may first set relay_indication to "1". And, the first inter-UE relay may set the cumulative number to "2".

[0333] When transmitting a direct communication request message, the source UE may also set relay_indication to "0", and if a value other than "0" (for example, value "15", assuming that 4 bits are used to represent relay_indication) is used to indicate that broadcasting of user information (or user information ID) is not allowed, the first inter-UE relay sets the cumulative number to "1".

[0334] Fig.16 An example of the above concept for multi-hop inter-UE relay is shown.

[0335] The above concept can also be applied to inter-UE relay discovery with Model B for a source remote UE to discover a target remote UE. For example, the inter-UE relay can also include information indicating the cumulative number of hops or relays involved in multi-hop inter-UE relay in the inter-UE relay discovery solicitation message.

[0336] Fig.17 An exemplary multi-route UE-to-UE relay is shown. Fig.17 As shown in , for the source remote UE, there may be multiple routes to reach the target remote UE via different relay UEs. Respectively, route A has 3 hops and route B has 2 hops. In this case, it is beneficial to consider the cumulative hop count for relay UE (or route) selection in terms of the transmission delay of the target remote UE. For example, the target remote UE may select relay 4 (i.e., route B) for communication with the source remote UE. In other words, the target remote UE may select a relay UE indicating fewer (or smaller) cumulative hops when receiving a direct communication request message or an inter-UE relay discovery solicitation message from multiple relay UEs. Subsequently, the target remote UE may transmit a security mode command or a direct communication acceptance message to the selected relay UE in response to receiving a direct communication request message from the selected relay UE, or transmit an inter-UE relay discovery response message to the selected relay UE in response to receiving an inter-UE relay discovery solicitation message from the selected relay UE. For relay UE selection, other factors such as the signal strength (e.g., RSRP) of the relay UE may also be considered.

[0337] Fig.18Flowchart 1800 of a method for supporting multi-hop inter-UE relay. In step 1805, the second relay UE stores the maximum number of hops specific to the relay service code (RSC) provided by the network. In step 1810, the second relay UE receives a first PC5-S message from the first relay UE, wherein the first PC5-S message includes a user information identifier (ID) of the first-end UE, the RSC, and the accumulated number of hops. In step 1815, the second relay UE transmits or broadcasts a second PC5-S message, wherein the second PC5-S message includes the user information ID of the first-end UE and a first relay indication, and the first relay indication is used to indicate that at least the user information ID of the first-end UE is allowed to be broadcast when the accumulated number of hops plus 1 is less than the maximum number of hops.

[0338] In one embodiment, the second PC5-S message may include a second relay indication, and when the cumulative number of hops plus 1 is equal to the maximum number of hops, the second relay indication is used to indicate that at least the user information ID of the first end UE is not allowed to be broadcast. In another embodiment, if the cumulative number of hops plus 1 is equal to the maximum number of hops, the second PC5-S message may not include the first relay indication.

[0339] In one embodiment, the first PC5-S message may include another relay indication, and the another relay indication is used to indicate that at least the user information ID of the first end UE is allowed to be broadcast. The first PC5-S message may include the user information identifier of the second end UE, the user information identifier of the first relay UE and / or the ProSe identifier (ID).

[0340] In one embodiment, the second PC5-S message may include user information of the second end UE, user information identifier of the second relay UE, ProSe ID and / or RSC. The first PC5-S message or the second PC5-S message may be a direct communication request message or an inter-UE relay discovery solicitation message.

[0341] Return to reference Figure 3 and Figure 4, in an exemplary embodiment from the perspective of the second relay UE. In one embodiment, the second relay UE stores the maximum number of hops specific to the RSC provided by the network. The second relay UE 300 includes a program code 312 stored in a memory 310. The CPU 308 can execute the program code 312 to enable the second relay UE to (i) store the maximum number of hops specific to the RSC, (ii) receive a first PC5-S message from the first relay UE, wherein the first PC5-S message includes the user information ID of the first end UE, the RSC and the cumulative number of hops, and (iii) transmit or broadcast a second PC5-S message, wherein the second PC5-S message includes the user information ID of the first end UE and a first relay indication, and the first relay indication is used to indicate that at least the user information ID of the first end UE is allowed to be broadcast when the cumulative number of hops plus 1 is less than the maximum number of hops. In addition, the CPU 308 can execute the program code 312 to perform all of the above actions and steps or other actions and steps described herein.

[0342] Fig.19 1900 is a flow chart of a method for supporting multi-hop inter-UE relay. In 1905, the second relay UE stores the maximum hop count specific to the relay service code (RSC) provided by the network. In 1910, the second relay UE receives a first PC5-S message from the first relay UE, wherein the first PC5-S message includes the user information ID of the first end UE, the RSC, and the first cumulative hop count. In 1915, if the first cumulative hop count plus 1 is less than or equal to the maximum hop count, the second relay UE transmits or broadcasts a second PC5-S message, wherein the second PC5-S message includes the user information ID and RSC of the first end UE.

[0343] In one embodiment, the second PC5-S message may include a second accumulated hop count set to the first accumulated hop count plus 1. If the first accumulated hop count plus 1 is greater than the maximum hop count, the second relay UE may not transmit or broadcast the second PC5-S message.

[0344] In one embodiment, the first PC5-S message may include a user information identifier of the second-end UE, a user information identifier of the first relay UE, and / or a ProSe identifier (ID). After a connection is established between the first-end UE and the second-end UE, the first-end UE may communicate with the second-end UE at least via the first relay UE and the second relay UE. In other words, after a connection is established between the first-end UE and the second-end UE, communication between the first-end UE and the second-end UE is performed at least via the first relay UE and the second relay UE.

[0345] In one embodiment, the second PC5-S message may include a user information identifier of the second end UE, a user information identifier of the second relay UE and / or a ProSe ID. According to the method as claimed in claim 1, the first PC5-S message or the second PC5-S message may be a direct communication request message or an inter-UE relay discovery solicitation message.

[0346] Return to reference Figure 3 and Figure 4 , in an exemplary embodiment from the perspective of the second relay UE. In one embodiment, the second relay UE stores the maximum number of hops specific to the RSC provided by the network. The second relay UE 300 includes a program code 312 stored in a memory 310. The CPU 308 can execute the program code 312 to enable the second relay UE to (i) store the maximum number of hops specific to the RSC, (ii) receive a first PC5-S message from the first relay UE, wherein the first PC5-S message includes the user information ID, RSC and the first cumulative number of hops of the first end UE, and (iii) if the first cumulative number of hops plus 1 is less than or equal to the maximum number of hops, transmit or broadcast a second PC5-S message, wherein the second PC5-S message includes the user information ID and RSC of the first end UE. In addition, the CPU 308 can execute the program code 312 to perform all of the above actions and steps or other actions and steps described herein.

[0347] Various aspects of the present disclosure have been described above. It should be understood that the teachings herein can be embodied in a wide variety of forms, and any specific structure, function, or both disclosed herein are only representative. Based on the teachings herein, it should be understood by those skilled in the art that the aspects disclosed herein can be implemented independently of any other aspects, and two or more of these aspects can be combined in various ways. For example, any number of aspects described herein can be used to implement a device or practice a method. In addition, other structures, functions, or structures and functions different from the aspects described in addition to one or more aspects described herein can be used to implement such devices or practice such methods. As an example of some of the above concepts, in some aspects, parallel channels can be established based on pulse repetition frequencies. In some aspects, parallel channels can be established based on pulse positions or offsets. In some aspects, parallel channels can be established based on time hopping sequences. In some aspects, parallel channels can be established based on pulse repetition frequencies, pulse positions or offsets, and time hopping sequences.

[0348] Those skilled in the art will understand that information and signals may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the above description may be represented by voltage, current, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.

[0349] Those skilled in the art will further appreciate that the various illustrative logical blocks, modules, processors, components, circuits, and algorithm steps described in conjunction with the aspects disclosed herein may be implemented as electronic hardware (e.g., digital implementations, analog implementations, or a combination of both, which may be designed using source decoding or some other techniques), and various forms of programs or design codes with instructions (for convenience, which may be referred to herein as "software" or "software modules"), or a combination of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functions. Whether such functions are implemented as hardware or software depends on the specific application and the design constraints imposed on the overall system. Those skilled in the art may implement the described functions in different ways for each specific application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present disclosure.

[0350] In addition, the various illustrative logical blocks, modules, and circuits described in conjunction with the aspects disclosed herein may be implemented within or performed by an integrated circuit ("IC"), an access terminal, or an access point. An IC may include a general purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, electrical components, optical components, mechanical components, or any combination thereof designed to perform the functions described herein, and may execute code or instructions residing within the IC, outside the IC, or both. A general purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, for example, a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

[0351] It should be understood that any specific order or hierarchy of steps in any disclosed process is an example of an exemplary method. It should be understood that based on design preferences, the specific order or hierarchy of steps in a process can be rearranged while remaining within the scope of the present disclosure. The accompanying method claims present elements of the various steps in an exemplary order and are not meant to be limited to the specific order or hierarchy presented.

[0352] The steps of the method or algorithm described in conjunction with the various aspects disclosed herein may be implemented directly in hardware, software modules executed by a processor, or a combination of the two. Software modules (e.g., including executable instructions and related data) and other data may reside in a data memory, such as a RAM memory, a flash memory, a ROM memory, an EPROM memory, an EEPROM memory, a register, a hard disk, a removable disk, a CD-ROM, or any other form of computer-readable storage medium known in the art. An example storage medium may be coupled to a machine such as a computer / processor (which may be referred to herein as a "processor" for convenience), such a processor may read information (e.g., code) from a storage medium and write the information to the storage medium. An example storage medium may be integrated with a processor. The processor and storage medium may reside in an ASIC. The ASIC may reside in a user device. In an alternative, the processor and storage medium may reside in a user device as discrete components. In addition, in some aspects, any suitable computer program product may include a computer-readable medium, which includes code related to one or more aspects of the present disclosure. In some aspects, a computer program product may include packaging materials.

[0353] Although the present invention has been described in conjunction with various aspects, it will be appreciated that the present invention is capable of further modifications. This application is intended to cover any changes, uses or adaptations of the present invention that generally follow the principles of the present invention and include such deviations from the present disclosure that are within the scope of known and customary practice in the field to which the present invention relates.

Claims

1. A method for supporting multi-hop user equipment relay, characterized in that: include: The second relay user equipment stores a maximum hop count specific to the relay service code provided by the network; The second relay user equipment receives a first PC5-S message from the first relay user equipment, wherein the first PC5-S message includes a user information identifier of the first end user equipment, the relay service code and a first accumulated hop count; as well as If the first cumulative hop count plus 1 is less than or equal to the maximum hop count, the second relay user equipment transmits or broadcasts a second PC5-S message, wherein the second PC5-S message includes the user information identifier of the first end user equipment and the relay service code.

2. The method according to claim 1, characterized in that The second PC5-S message includes a second accumulated hop count which is set to be the first accumulated hop count plus 1.

3. The method according to claim 1, characterized in that If the first cumulative hop count plus 1 is greater than the maximum hop count, the second relay user equipment does not transmit or broadcast the second PC5-S message.

4. The method according to claim 1, characterized in that: The first PC5-S message includes the user information identifier of the second end user equipment, the user information identifier of the first relay user equipment, or a proximity-based service identifier.

5. The method according to claim 4, characterized in that After a connection is established between the first end user equipment and the second end user equipment, communication between the first end user equipment and the second end user equipment is performed at least via the first relay user equipment and the second relay user equipment.

6. The method according to claim 1, characterized in that The second PC5-S message includes a user information identifier of the second end user equipment, a user information identifier of the second relay user equipment, or a proximity-based service identifier.

7. The method according to claim 1, characterized in that The first PC5-S message or the second PC5-S message is a direct communication request message or a relay discovery request message between user devices.

8. A method for supporting multi-hop user equipment relay, characterized in that: include: The second relay user equipment is provided by the network with a maximum hop count specific to the relay service code; The second relay user equipment receives a first PC5-S message from the first relay user equipment, wherein the first PC5-S message includes a user information identifier of the first end user equipment, the relay service code and the accumulated hop count; and The second relay user equipment transmits or broadcasts a second PC5-S message, wherein the second PC5-S message includes the user information identifier and the first relay indication of the first-end user equipment, and when the cumulative number of hops plus 1 is less than the maximum number of hops, the first relay indication is used to indicate that at least the user information identifier of the first-end user equipment is allowed to be broadcast.

9. The method according to claim 8, characterized in that The second PC5-S message includes a second relay indication. When the cumulative number of hops plus 1 is equal to the maximum number of hops, the second relay indication is used to indicate that at least the user information identifier of the first end user equipment is not allowed to be broadcasted.

10. The method according to claim 8, characterized in that If the accumulated hop count plus 1 is equal to the maximum hop count, the second PC5-S message does not include the first relay indication.

11. The method according to claim 8, characterized in that The first PC5-S message includes another relay indication, where the other relay indication is used to indicate that at least the user information identifier of the first end user equipment is allowed to be broadcasted.

12. The method according to claim 8, characterized in that The first PC5-S message includes the user information identifier of the second end user equipment, the user information identifier of the first relay user equipment, or a proximity-based service identifier.

13. The method according to claim 8, characterized in that The second PC5-S message includes the user information identifier of the second end user equipment, the user information identifier of the second relay user equipment, a proximity-based service identifier or the relay service code.

14. The method according to claim 8, characterized in that The first PC5-S message or the second PC5-S message is a direct communication request message or a relay discovery request message between user devices.

15. A second relay user equipment supporting relaying between multi-hop user equipments, characterized in that: include: Control circuit; a processor installed in the control circuit; as well as a memory installed in the control circuit and operatively coupled to the processor; wherein the processor is configured to execute program code stored in the memory to: Stores the maximum number of hops specific to the relay service code provided by the network; receiving a first PC5-S message from a first relay user device, wherein the first PC5-S message includes a user information identifier of the first end user device, the relay service code, and a first accumulated hop count; as well as If the first cumulative hop count plus 1 is less than or equal to the maximum hop count, a second PC5-S message is transmitted or broadcasted, wherein the second PC5-S message includes the user information identifier of the first end user equipment and the relay service code.

16. The second relay user equipment according to claim 15, characterized in that: The second PC5-S message includes a second accumulated hop count which is set to be the first accumulated hop count plus 1.

17. The second relay user equipment according to claim 15, characterized in that: If the first cumulative hop count plus 1 is greater than the maximum hop count, the second relay user equipment does not transmit or broadcast the second PC5-S message.

18. The second relay user equipment according to claim 15, characterized in that: The first PC5-S message includes the user information identifier of the second end user equipment, the user information identifier of the first relay user equipment, or a proximity-based service identifier.

19. The second relay user equipment according to claim 15, characterized in that: The second PC5-S message includes a user information identifier of the second end user equipment, a user information identifier of the second relay user equipment, or a proximity-based service identifier.

20. The second relay user equipment according to claim 15, characterized in that: The first PC5-S message or the second PC5-S message is a direct communication request message or a relay discovery request message between user devices.

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