Method and apparatus for target end ue supporting candidate u2u relay discovery

Abstract

The invention provides a method and equipment for supporting relay discovery of target-end user equipment between candidate user equipment. The method for target-end user equipment comprises: establishing a connection with relay user equipment to support inter-user equipment relay communication between source-end user equipment and target-end user equipment via the relay user equipment; receiving, from the relay user equipment, a link modification request message indicating a list of candidate relay user equipment for performing agreed relay reselection; determining to transmit a discovery solicitation message to candidate relay user equipment in the list of candidate relay user equipment, wherein the discovery solicitation message indicates that the discovery solicitation message is used for relay discovery between candidate user equipment by at least setting an application layer identity indicated in the discovery solicitation message to a specific value; receiving, from the candidate relay user equipment, a discovery response message for relay discovery between the candidate user equipment; and transmitting a link modification accept message indicating the candidate relay user equipment to the relay user equipment.

Description

(19) State Intellectual Property Office (12) Invention Patent Application (10) Application Publication Number (43) Application Publication Date (21) Application Number 202510817023.X (22) Application Date 2025.06.18 (30) Priority Data 63 / 664,131 2024.06.25 US (71) Applicant ASUS Technology Licensing Co., Ltd. Address Taipei, Taiwan (72) Inventors Hung Chen-hsiang, Pan Li-te, Kuo Yu-hsuan (74) Patent Agency Beijing Liu Shen Law Firm 11105 Patent Attorney Hsu Hsieh-cheng (51) Int.Cl. H04W 40 / 22 (2009.01) H04W 76 / 10 (2018.01) H04W 88 / 04 (2009.01) H04W 8 / 00 (2009.01) (54) Invention Title: Method and Apparatus for Target User Equipment Supporting Inter-User Equipment Relay Discovery (57) Abstract: A method and apparatus are provided for a target user equipment supporting inter-user equipment relay discovery. The method for the target user equipment includes: establishing a connection with a relay user equipment to support inter-user equipment relay communication between the source user equipment and the target user equipment via the relay user equipment; receiving from the relay user equipment a link modification request message indicating a list of candidate relay user equipments for performing agreed relay reselection; determining to transmit a discovery request message to a candidate relay user equipment in the list of candidate relay user equipments, wherein the discovery request message indicates that the discovery request message is used for inter-user equipment relay discovery by setting at least an application layer identifier indicated in the discovery request message to a specific value; receiving from the candidate relay user equipment a discovery response message for inter-user equipment relay discovery; and transmitting to the relay user equipment a link modification acceptance message indicating the candidate relay user equipment. Claims 2 pages, Description 68 pages, Drawings 22 pages, CN 121218295 A 2025.12.26 CN 1 21 21 82 95 A 1. A method for a target user equipment, characterized in that it comprises: establishing a connection with a relay user equipment to support inter-user equipment relay communication between a source user equipment and the target user equipment via the relay user equipment; receiving from the relay user equipment a link modification request message indicating a list of candidate relay user equipments for performing agreed relay reselection; determining to transmit a discovery request message to a candidate relay user equipment in the list of candidate relay user equipments, wherein the discovery request message indicates that the discovery request message is used for inter-user equipment relay discovery by setting at least an application layer identifier indicated in the discovery request message to a specific value; receiving from the candidate relay user equipment a discovery response message for inter-user equipment relay discovery; and1. The method of claim 1, wherein the specific value is 0. 2. The method of claim 1, wherein the application layer identifier is included in the user information field. 3. The method of claim 3, wherein the user information field is included in the direct discovery set. 4. The method of claim 4, wherein the discovery request message further indicates that the discovery request message is used for inter-user equipment relay discovery by the number of user information entries in the direct discovery set being 1. 6. The method of claim 4, wherein the direct discovery set is mandatory in the discovery request message. 7. The method of claim 1, wherein the discovery response message received from the candidate relay user equipment is a PROSE PC5 DISCOVERY message for inter-user equipment relay discovery response, and the discovery request message transmitted by the target user equipment is a PROSE PC5 DISCOVERY message for inter-user equipment relay discovery request. 8. The method of claim 1, wherein the discovery response message indicates that the discovery response message is used for inter-user equipment relay discovery by setting at least the second application layer identifier indicated in the discovery response message to the specific value. 9. The method of claim 8, further comprising: determining that the discovery response message is used for inter-user equipment relay discovery based on the second application layer identifier being set to the specific value. 10. The method of claim 1, wherein the agreed relay reselection is triggered by the source user equipment. 11. A target user equipment, characterized in that it comprises: a memory; and a processor operatively coupled to the memory, wherein the processor is configured to execute program code to: establish a connection with a relay user equipment to support inter-user equipment relay communication between a source user equipment and the target user equipment via the relay user equipment; receive from the relay user equipment a link modification request message indicating a list of candidate relay user equipments for performing agreed relay reselection; determine to transmit a discovery request message to a candidate relay user equipment in the list of candidate relay user equipments, wherein the discovery request message indicates that the discovery request message is used for inter-user equipment relay discovery by setting at least an application layer identifier indicated in the discovery request message to a specific value; receive from the candidate relay user equipment a discovery response message for inter-user equipment relay discovery; and transmit to the relay user equipment a link modification acceptance message indicating the candidate relay user equipment.12. The target user equipment according to claim 11, wherein the specific value is 0. 13. The target user equipment according to claim 11, wherein the application layer identifier is included in the user information field. 14. The target user equipment according to claim 13, wherein the user information field is included in the direct discovery set. 15. The target user equipment according to claim 14, wherein the discovery request message further indicates that the discovery request message is used for inter-user equipment relay discovery by the number of user information in the direct discovery set being 1. 16. The target user equipment according to claim 14, wherein the direct discovery set is mandatory in the discovery request message. 17. The target user equipment according to claim 11, wherein the discovery response message received from the candidate relay user equipment is a PROSE PC5 DISCOVERY message for inter-user equipment relay discovery response, and the discovery request message transmitted by the target user equipment is a PROSE PC5 DISCOVERY message for inter-user equipment relay discovery request. 18. The target user equipment of claim 11, wherein the discovery response message indicates that the discovery response message is used for inter-user equipment relay discovery by setting at least a second application layer identifier indicated in the discovery response message to the specific value. 19. The target user equipment of claim 18, wherein the processor is further configured to execute the program code to: determine, based on the second application layer identifier being set to the specific value, that the discovery response message is used for inter-user equipment relay discovery. 20. The target user equipment of claim 11, wherein the agreed relay reselection is triggered by the source user equipment. Claims 2 / 2 Page 3 CN 121218295 A Method and apparatus for a target user equipment supporting inter-user equipment relay discovery

[0001] Cross-reference to related applications

[0002] This application claims priority and benefit to U.S. Provisional Patent Application No. 63 / 664,131, filed June 25, 2024, which is incorporated herein by reference in its entirety. Technical Field

[0003] This disclosure generally relates to wireless communication networks, and more specifically, to methods and apparatus for supporting relay UEs for supporting relay discovery between candidate User Equipment (UE) (UE-to-UE, U2U) in wireless communication systems. Background Art

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

[0005] An exemplary network architecture is the Evolved Universal Terrestrial Radio Access Network (E-UTRAN). E-UTRAN systems can provide high data throughput to enable the aforementioned IP-bearing voice and multimedia services. Currently, the 3GPP standards organization is discussing next-generation (e.g., 5G) new air interface technologies. Therefore, modifications to the current body of the 3GPP standard are currently being submitted, and these modifications are being considered for the evolution and finalization of the 3GPP standard. Summary of the Invention

[0006] Methods, systems, and devices are provided for supporting target UEs in candidate user equipment (UE) inter-user equipment (U2U) relay discovery in wireless communication systems.

[0007] In various embodiments, a method for a target UE includes: establishing a connection with a relay UE to support U2U relay communication between a source UE and a target UE via the relay UE; receiving from the relay UE a link modification request message indicating a list of candidate relay UEs for performing an agreed relay reselection; determining to transmit a discovery request message to a candidate relay UE in the candidate relay UE list, wherein the discovery request message indicates that the discovery request message is used for candidate U2U relay discovery by setting at least an application layer identifier (ID) indicated in the discovery request message to a specific value; receiving from the candidate relay UE a discovery response message for candidate U2U relay discovery; and transmitting to the relay UE a link modification acceptance message indicating the candidate relay UE. Brief Description of the Drawings

[0008] FIG1 illustrates a diagram of a wireless communication system according to an embodiment of the present invention.

[0009] FIG2 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 embodiment of the present invention.

[0010] FIG3 is a functional block diagram of a communication system according to an embodiment of the present invention. Specification 1 / 68 page 4 CN 121218295 A

[0011] FIG4 is a functional block diagram of the program code of FIG3 according to an embodiment of the present invention.

[0012] FIG5 is a reproduction of FIG6.3.2.4.2-1 of 3GPP TS 23.304 v18.5.1: 5G ProSe UE inter-relay discovery using model A.

[0013] FIG6 is a reproduction of FIG6.3.2.4.3-1 of 3GPP TS 23.304 v18.5.1: 5G ProSe UE inter-relay discovery using model B.

[0014] Figure 7 is a reproduction of Figure 6.7.1.1-1 of 3GPP TS 23.304 v18.5.1: Layer 2 link establishment via 5G ProSe Layer 3 UE inter-relay.

[0015] Figure 8 is a reproduction of Figure 6.7.2-1 of 3GPP TS 23.304 v18.5.1: 5G ProSe communication via 5G ProSe Layer 2 UE inter-relay.

[0016] Figure 9 is a reproduction of Figure 6.7.4.2-1 of 3GPP TS 23.304 v18.5.1: Agreeing on 5G ProSe Layer 2 UE inter-relay reselection.

[0017] Figure 10 is a reproduction of Figure 6.7.4.3-1 of 3GPP TS 23.304 v18.5.1: Agreeing on 5G ProSe Layer 3 UE inter-relay reselection.

[0018] Figure 11 is a reproduction of Figure 7.2.3.2.1 of 3GPP TS 24.554 v18.4.0: the 5G ProSe direct link modification process.

[0019] Figure 12 is a reproduction of Figure 7.2.3.2.2 of 3GPP TS 24.554 v18.4.0: the 5G ProSe layer 3 UE inter-relay reselection 5G ProSe direct link modification process.

[0020] Figure 13 is a reproduction of Figure 8a.2.1.3.2.2.1 of 3GPP TS 24.554 v18.4.0: the discoverer UE process for inter-UE relay discovery.

[0021] Figure 14 is a reproduction of Figure 8a.2.1.3.3.2.1 of 3GPP TS 24.554 v18.4.0: the relay UE process for inter-UE relay discovery with the discoverer UE.

[0022] Figure 15 is a reproduction of Figure 8a.2.1.3.3.2.2 of 3GPP TS 24.554 v18.4.0: the relay UE process for inter-UE relay discovery with the discoverer UE.

[0023] Figure 16 is a reproduction of Figure 8a.2.1.3.4.2.1 of 3GPP TS 24.554 v18.4.0: the discoverer UE process for inter-UE relay discovery.

[0024] Figure 17 is a reproduction of Figure 11.2.1.1 of 3GPP TS 24.554 v18.4.0: the ProSe direct discovery PC5 message type parameters.

[0025] Figure 18 is a reproduction of Figure 11.2.15.1 of 3GPP TS 24.554 v18.4.0: the application layer ID information element.

[0026] Figure 19 is a reproduction of Figure 11.2.17.1 of 3GPP TS 24.554 v18.4.0: Direct Discovery Set Information Elements.

[0027] Figure 20 is a reproduction of Figure 11.2.17.2 of 3GPP TS 24.554 v18.4.0: List of Protected User Information IDs.

[0028] Figure 21 is Figure 11.2.17.3 of 3GPP TS 24.554 v18.4.0: Reproduction of Protected User Information.

[0029] Figure 22 is an example diagram illustrating 5G ProSe UE-to-UE relay reselection according to an embodiment of the present invention, wherein the second UE can perform a candidate U2U relay discovery process.

[0030] Figure 23 is an example diagram illustrating 5G ProSe UE-to-UE relay reselection according to an embodiment of the present invention, wherein the PROSE PC5 DISCOVERY message for the UE-to-UE relay discovery response message may include an indication of whether the PROSE PC5 DISCOVERY message for the UE-to-UE relay discovery response message is used for candidate 5G ProSe UE-to-UE relay discovery.

[0031] FIG24 is an example diagram illustrating 5G ProSe UE inter-relay reselection according to an embodiment of the present invention, wherein the content of the Direct Discovery Set IE in the PROSE PC5 DISCOVERY message for the UE inter-relay discovery response message can indicate that the PROSE PC5 DISCOVERY message for the UE inter-relay discovery response message is for candidate 5G ProSe UE inter-relay discovery.

[0032] FIG25 is an example diagram illustrating 5G ProSe UE inter-relay reselection according to an embodiment of the present invention, wherein a candidate relay UE can consider the PROSE PC5 DISCOVERY message for the UE inter-relay discovery request message as being for candidate U2U relay discovery based on the L2ID associated with the PROSE PC5 DISCOVERY message for the UE inter-relay discovery request message.

[0033] FIG26 is an example diagram illustrating the interaction of UEs during the notification process of UE inter-relay discovery according to an embodiment of the present invention (FIG8a.2.1.2.2.2.1).

[0034] FIG27 is a new table diagram (FIG. 11.2.x.1) showing candidate discovery support indication information elements according to an embodiment of the present invention.

[0035] FIG28 is a new table diagram (FIG. 11.2.z.1) showing candidate discovery indication information elements according to an embodiment of the present invention.

[0036] FIG29 is a table diagram (FIG. 11.2.17.1) showing direct discovery set information elements according to an embodiment of the present invention.

[0037] FIG30 is a table diagram (FIG. 11.2.17.2) showing a list of protected user information IDs according to an embodiment of the present invention.

[0038] FIG31 is a table diagram (FIG. 11.2.17.3) showing protected user information according to an embodiment of the present invention.

[0039] FIG32 is a flowchart of a method for a relay UE in a wireless communication system according to an embodiment of the present invention, wherein...The method includes: receiving a discovery request message from a target UE; and in response to receiving the discovery request message containing information, the relay UE transmits a discovery response message to the target UE, and does not perform a U2U relay discovery process.

[0040] FIG33 is a flowchart of a method for a target UE in a wireless communication system according to an embodiment of the present invention, the method including: establishing a connection with a relay UE to support inter-UE relay communication between a source UE and a target UE via the relay UE; receiving from the source UE a link modification request message indicating at least one candidate relay UE for performing agreed relay reselection; transmitting a discovery request message to the candidate relay UE; receiving a discovery response message from the candidate relay UE; and transmitting a link modification acceptance message to the source UE indicating the candidate relay UE.

[0041] FIG34 is a flowchart of a method for a relay UE in a wireless communication system according to an embodiment of the present invention. The method includes: receiving a first discovery request message from a first target UE; performing a U2U relay discovery process in response to receiving the first discovery request message addressed to a default Layer 2 ID; receiving a second discovery request message from a second target UE; and not performing a U2U relay discovery process in response to receiving the second discovery request message addressed to the Layer 2 ID of the relay UE.

[0042] FIG35 is a flowchart of a method for a second-end UE in a wireless communication system according to an embodiment of the present invention. The method includes: sending a first discovery request message; and sending a second discovery request message, wherein if the second discovery request message is for candidate U2U relay discovery, the second discovery request message is sent or addressed to the Layer 2 ID of the candidate relay UE by using the Layer 2 ID of the candidate relay UE as the destination Layer 2 ID.

[0043] FIG36 is a flowchart of a method for a target UE in a wireless communication system according to an embodiment of the present invention, the method comprising: establishing a connection with a relay UE to support U2U relay communication between a source UE and a target UE via the relay UE; receiving from the relay UE a link modification request message indicating a list of candidate relay UEs for performing agreed relay reselection; determining to transmit a discovery request message to a candidate relay UE in the candidate relay UE list; receiving from the candidate relay UE a discovery response message for candidate U2U relay discovery; and transmitting to the relay UE a link modification acceptance message indicating the candidate relay UE. Detailed Description

[0044] The invention described herein can be applied to, or implemented in, the exemplary wireless communication systems and apparatus described below. Furthermore, the invention is described primarily in the context of the 3GPP architecture reference model. However, it should be understood that, using the disclosed information, those skilled in the art can readily adapt it to 3GPP2 networks.The invention is used and implemented in network architectures and other network architectures.

[0045] The exemplary wireless communication systems and apparatus described below employ wireless communication systems that support broadcast services. Wireless communication systems are widely deployed to provide various types of communication, such as voice, data, etc. These systems may 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) radio access, 3GPP2 Ultra Mobile Broadband (UMB), 3GPP New Radio (NR), or some other modulation techniques.

[0046] Specifically, the exemplary wireless communication systems and apparatus described below can be designed to support one or more standards, such as those provided by the association referred to herein as 3GPP, which is named the “3rd Generation Partnership Project”, including: [1] [TS 23.304] 3GPP TS 23.304 v18.5.1, “Proximity-based Services (ProSe) in 5G Systems (5GS) (Revision 18)”; and [2] [TS 24.554] 3GPP TS 24.554 v18.4.0, “Proximity-services (ProSe) in Protocol Aspects of 5G Systems (5GS) (Revision 18)”. The standards and documents listed above are expressly and entirely incorporated herein by reference.

[0047] FIG1 illustrates a multiple access wireless communication system according to an embodiment of the present invention. Access network 100 (AN) includes multiple antenna groups, one of which contains antennas 104 and 106, another contains antennas 108 and 110, and additional antenna groups contain antennas 112 and 114. In Figure 1, only two antennas are shown for each antenna group; however, more or fewer antennas may be used for each antenna group. Access terminal 116 (AT) communicates with antennas 112 and 114, wherein antennas 112 and 114 transmit information to access terminal 116 via forward link 120, and...Information is received from access terminal 116 via reverse link 118. AT 122 communicates with antennas 106 and 108, wherein antennas 106 and 108 transmit information to AT 122 via forward link 126 and receive information from AT 122 via reverse link 124. In an FDD system, communication links 118, 120, 124, and 126 can communicate using different frequencies. For example, forward link 120 can use a frequency different from that used by reverse link 118.

[0048] Each antenna group and / or the area in which said antenna groups are designed to communicate is generally referred to as a sector of the access network. In an embodiment, each antenna group is designed to communicate with an access terminal in a sector of the area covered by access network 100.

[0049] In communication via forward links 120 and 126, the transmit antennas of access network 100 can use beamforming to improve the signal-to-noise ratio of the forward links used for different access terminals 116 and 122. Furthermore, compared to an access network that transmits to all its access terminals via a single antenna, an access network that uses beamforming to transmit to access terminals randomly distributed within its coverage area causes less interference to access terminals in adjacent cells.

[0050] AN can be a fixed station or base station for communicating with terminals, and can also be referred to as an access point, NodeB, base station, enhanced base station, eNodeB, or some other term. AT can also be referred to as user equipment (UE), wireless communication device, terminal, access terminal, or some other term.

[0051] FIG2 is a simplified block diagram of an embodiment of a transmitter system 210 (also referred to as an access network) and a receiver system 250 (also referred to as an access terminal (AT) or user equipment (UE)) in a MIMO system 200. At the transmitter system 210, service data for multiple data streams is provided from a data source 212 to a transmit (TX) data processor 214.

[0052] In one embodiment, each data stream is transmitted via a corresponding transmit antenna. The Tx data processor 214 formats, decodes, and passes the service data for each data stream based on a specific decoding scheme selected for each data stream, to provide decoded data.

[0053] The decoded data of each data stream can be multiplexed with pilot data using OFDM technology. The pilot data is typically a known data pattern processed in a known manner and can be used at the receiver system to estimate the channel response. Then, the multiplexed pilot data and decoded data for the data stream are modulated (i.e., symbol mapped) based on a specific modulation scheme selected for each data stream (e.g., BPSK, QPSK, M-PSK, or M-QAM) to provide...Modulation symbols are provided. The data rate, decoding, and modulation for each data stream can be determined by instructions executed by processor 230. Memory 232 is coupled to processor 230.

[0054] Modulation symbols for all data streams are then provided to TX MIMO processor 220, which can further process the modulation symbols (e.g., for OFDM). TX MIMO processor 220 then provides NT modulation symbol streams to NT transmitters (TMTRs) 222a to 222t. In some embodiments, TX MIMO processor 220 applies beamforming weights to the symbols of the data streams and to the antennas from which the symbols are transmitted.

[0055] Each transmitter 222 receives and processes a corresponding symbol stream to provide one or more analog signals, and further modulates the analog signals (e.g., amplifies, filters, and up-converts) to provide a modulated signal suitable for transmission through the MIMO channel. Next, NT modulated signals from transmitters 222a to 222t are transmitted from NT antennas 224a to 224t respectively.

[0056] At receiver system 250, the transmitted modulated signals are received by NR antennas 252a to 252r, and the signals received from each antenna 252 are provided to the corresponding receivers (RCVRs) 254a to 254r. Each receiver 254 modulates (e.g., filters, amplifies, and down-converts) the corresponding received signal, digitizes the modulated signal to provide a sample, and further processes the sample to provide the corresponding "received" symbol stream.

[0057] Next, RX data processor 260 receives NR symbol streams from NR receivers 254 and processes the NR received symbol streams based on specific receiver processing techniques to provide NT "detected" symbol streams. Then, RX data processor 260 demodulates, deinterleaves, and decodes each detected symbol stream to recover the service data for the data stream. The processing performed by the RX data processor 260 is complementary to the processing performed by the TX MIMO processor 220 and TX data processor 214 at the transmitter system 210.

[0058] The processor 270 periodically determines which pre-decoding matrix (discussed below) to use. The processor 270 formulates a reverse link message including a matrix index portion and a rank portion.

[0059] 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 service data for multiple data streams from the data source 236), modulated by the modulator 280, regulated by the transmitters 254a to 254r, and transmitted back to the transmitter system 210.

[0060] At transmitter system 210, the modulated signal from receiver system 250 is 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. Then, processor 230 determines which pre-decoding matrix to use to determine beamforming weights and then processes the extracted message.

[0061] Memory 232 can be used by processor 230 to temporarily store some buffered / computational data from 240 or 242, some buffered data from 212, or some specific program code. Additionally, memory 272 can be used by processor 270 to temporarily store some buffered / computational data from 260, some buffered data from 236, or some specific program code.

[0062] Turning to FIG3, this figure shows an alternative simplified functional block diagram of a communication device according to an embodiment of the present invention. As shown in Figure 3, the UE (or AT) 116 and 122 in Figure 1 can be implemented using a communication device 300 in a wireless communication system, 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 via the CPU 308, thereby controlling the operation of the communication device 300. The communication device 300 can receive signals input by the user via the input device 302 (e.g., a keyboard or keypad) and can output images and sounds via the output device 304 (e.g., a monitor or speaker). The transceiver 314 is used to receive and transmit wireless signals, pass the received signals to the control circuit 306, and wirelessly output signals generated by the control circuit 306.

[0063] FIG4 is a simplified block diagram of the program code 312 shown in FIG3 according to an embodiment of the present invention. In this embodiment, the program code 312 includes an application layer 400, a layer 3 portion 402, and a layer 2 portion 404, and is coupled to a layer 1 portion 406. The layer 3 portion 402 typically performs radio resource control. The layer 2 portion 404 typically performs link control. The layer 1 portion 406 typically performs physical connection.

[0064] For LTE, LTE-A, or NR systems, the layer 2 portion 404 may include a radio link control (RLC) layer and a medium access control (MAC) layer. The layer 3 portion 402 may include a radio resource control (RRC) layer.

[0065] Any two or more of the following paragraphs, (sub)bullets, points, actions, or claims described in each of the following inventive paragraphs or sections may be logically, reasonably, and appropriately combined to form a particular method.

[0066] Any sentence, paragraph, (sub)bullet, point, action, or claim described in each of the following inventive paragraphs or sections may be implemented independently and separately to form a particular method or apparatus. In the following inventive disclosure, reliances such as “based on,” “more specifically,” “example,” etc., are merely one possible embodiment and do not limit the particular method or apparatus.

[0067] 3GPP TS 23.304 ([1][TS 23.304]3GPP TS 23.304 v18.5.1) specifies the procedures related to inter-UE relay in version 18, as referenced below:

[0068] = ... As described in Clause 5.1, in order to perform 5G ProSe UE-to-UE relay discovery, the 5G ProSe end UE and the 5G ProSe UE-to-UE relay are pre-configured or pre-configured with relevant information.

[0072] A Relay Service Code (RSC) is used in 5G ProSe UE-to-UE relay discovery to indicate the connectivity services provided by the 5G ProSe UE-to-UE relay to the 5G ProSe end UE. As defined in Clause 5.1, the RSC is pre-configured or pre-configured on the 5G ProSe UE-to-UE relay and the 5G ProSe end UE. As specified in Clause 5.1, the 5G ProSe UE-to-UE relay and the 5G ProSe end UE determine whether the RSC provides 5G ProSe Layer 2 or Layer 3 UE-to-UE relay services based on the UE-to-UE relay layer indicator. 5G ProSe UE-to-UE relays that support multiple RSCs use multiple discovery messages to announce the RSC, with each discovery message containing one RSC.

[0073] 6.3.2.4.2 Process of 5G ProSe UE Inter-Relay Discovery Using Model A

[0074] Figure 6.3.2.4.2-1 depicts the process of 5G ProSe UE Inter-Relay Discovery using Model A.

[0075] Figure 5 is a reproduction of Figure 6.3.2.4.2-1 of 3GPP TS 23.304 v18.5.1: 5G ProSe UE Inter-Relay Discovery using Model A.Instruction manual 6 / 68 pages 9 CN 121218295 A

[0076] 1. The 5G ProSe UE inter-relay has discovered other neighboring UEs and obtains a direct discovery set from the other neighboring UEs according to RSC. (e.g., via a previous 5G ProSe UE inter-relay discovery or via a secure PC5 connection between a 5G ProSe U2U relay and a 5G ProSe end UE (refer to TS 33.503

[29] )).

[0077] 2. The 5G ProSe UE inter-relay sends an UE inter-relay discovery announcement message. The UE inter-relay discovery announcement message contains the discovery message type, the user information ID of the 5G ProSe UE inter-relay, RSC, and a list of direct discovery sets received from the 5G ProSe end UE that supports RSC. The UE inter-relay discovery announcement message is sent using the source layer 2 ID and the destination layer 2 ID as described in clause 5.8.4.

[0078] The 5G ProSe UE relay should only announce the user information ID of other nearby UEs, which did not include an announcement prohibition indication when previously discovered.

[0079] Note: As specified in TS 38.331

[16] , the 5G ProSe UE relay only announces the direct discovery set from other nearby UEs if the PC5 signal strength of other nearby UEs measured by the 5G ProSe UE relay is higher than the configured signal strength threshold.

[0080] The 5G ProSe end UE listens for announcement messages from the 5G ProSe UE relay. As specified in Clause 5.1, the 5G ProSe end UE determines the destination layer 2 ID for signaling reception.

[0081] 6.3.2.4.3 5G ProSe UE Relay Discovery Process Using Model B

[0082] Figure 6.3.2.4.3-1 depicts the 5G ProSe UE relay discovery process using Model B.

[0083] Figure 6 is a reproduction of Figure 6.3.2.4.3-1 of 3GPP TS 23.304 v18.5.1: 5G ProSe UE-to-UE relay discovery using Model B.

[0084] 1. The discoverer 5G ProSe end UE (UE-1) sends a 5G ProSe UE-to-UE relay discovery request message. The 5G ProSe UE-to-UE relay discovery request message contains a discovery message type, RSC, and a direct discovery set, which contains the user information IDs of the discoverer 5G ProSe end UE (UE-1) and the discoverer 5G ProSe end UE (UE-2). The 5G ProSe UE-to-UE relay discovery request message is sent using the source layer 2 ID and the destination layer 2 ID as described in Clause 5.8.4.

[0085] As specified in Clause 5.1, 5G ProSeThe UE inter-relay determines the destination layer 2 ID for signaling reception.

[0086] The discoverer 5G ProSe end UE may include a notification prohibition indication in the UE inter-relay discovery request message. If the 5G ProSe UE inter-relay receives a relay discovery request message with a notification prohibition indication, it will not consider the 5G ProSe end UE discovered during this process as included in the 5G ProSe UE inter-relay discovery using model A, see step 1 of clause 6.3.2.4.2.

[0087] 2. If the RSC contained in the request message matches any of the (pre)configured RSCs of the 5G ProSe UE inter-relay, as specified in clause 5.1.5.1, the 5G ProSe UE inter-relay sends a 5G ProSe UE inter-relay discovery request message. The 5G ProSe UE-to-UE relay discovery request message includes a discovery message type, a direct discovery set, the user information ID of the UE-to-UE relay, and an RSC. The direct discovery set includes the user information IDs of the discoverer 5G ProSe UE (UE-1) and the discoverer 5G ProSe UE (UE-2). As described in Clause 5.8.4, the 5G ProSe UE-to-UE relay discovery request message is sent using a source layer 2 ID and a destination layer 2 ID.

[0088] As specified in Clause 5.1, the 5G ProSe UE determines the destination layer 2 ID for signaling reception.

[0089] As specified in Clause 5.8.4.2, the 5G ProSe UE-to-UE relay selects its own source layer 2 ID.

[0090] 3. If the RSC contained in the request message matches any of the (pre)configured RSCs of the discoverer 5G ProSe UE (UE-2), as specified in Clause 5.1.5.1, and the discoverer 5G ProSe UE (UE-2) matches the user information ID of the discoverer 5G ProSe UE (UE-2) contained in the request message, then the discoverer 5G ProSe UE (UE-2) responds to the 5G ProSe UE Inter-Relay with a 5G ProSe UE Inter-Relay Discovery Response Message. The response message contains a discovery message type, an RSC, and a direct discovery set, which contains the user information ID of the discoverer 5G ProSe UE (UE-1) and the user information ID of the discoverer 5G ProSe UE (UE-2). As described in Clause 5.8.4, a 5G ProSe UE-to-UE relay discovery response message is sent using the source layer 2 ID and destination layer 2 ID. If the discovered 5G ProSe end UE (UE-2) is from a different 5G ProSe...If an inter-UE relay receives multiple inter-UE relay discovery request messages with the same RSC and the user information ID of the discoverer 5G ProSe end UE (UE-2), it may (e.g., based on the PC5 signal strength of each received message) choose to respond to or not respond to the 5G ProSe inter-UE relay.

[0091] The discoverer 5G ProSe end UE may include an announcement prohibition indication in the inter-UE relay discovery response message. If the 5G ProSe inter-UE relay receives a relay discovery response message with an announcement prohibition indication, it will not consider the 5G ProSe end UE discovered during this process as included in the 5G ProSe inter-UE relay discovery using Model A, see step 1 of clause 6.3.2.4.2.

[0092] 4. The 5G ProSe inter-UE relay sends a 5G ProSe inter-UE relay discovery response message. The 5G ProSe UE-to-UE relay discovery response message includes the discovery message type, the user information ID of the UE-to-UE relay, RSC, the user information ID of the discoverer 5G ProSe UE (UE-1), and the user information ID of the discoverer 5G ProSe UE (UE-2). As described in Clause 5.8.4, the 5G ProSe UE-to-UE relay discovery response message is sent using the source layer 2 ID and the destination layer 2 ID.

[0093] 6.3.2.4.4 Candidate 5G ProSe UE-to-UE Relay Discovery

[0094] When the discoverer UE discovers a candidate 5G ProSe UE-to-UE relay, this process of candidate 5G ProSe UE-to-UE relay discovery supports the agreed relay reselection described in Clause 6.7.4.

[0095] The method of using the 5G ProSe UE inter-relay discovery process (see Clause 6.3.2.4.3) using Model B differs as follows:

[0096] - Step 1: In the 5G ProSe UE inter-relay discovery request message, the RSC and the user information ID of the candidate 5G ProSe UE inter-relay are included in the UE inter-relay discovery set, and the message does not include the direct discovery set. If the 5G ProSe end UE receives the layer 2 ID of the candidate 5G ProSe UE inter-relay in the link modification request message, it can set the layer 2 ID of the candidate 5G ProSe UE inter-relay as the destination layer 2 ID.

[0097] Note: The user information ID of the candidate 5G ProSe UE inter-relay and the user information ID of the discovered 5G ProSe end UE can be distinguished as different IEs in the message by the 5G ProSe UE inter-relay.

[0098] - Skip steps 2 and 3 because there is no direct discovery set, and the candidate 5G ProSe in the received 5GProSe UE inter-relay discovery request message.The user information ID of the UE inter-relay matches the user information ID of the 5G ProSe UE inter-relay.

[0099] - Step 4: If the 5G ProSe UE inter-relay matches the user information ID of the candidate 5G ProSe UE inter-relay received in the 5G ProSe UE inter-relay discovery request, it sends a 5G ProSe UE inter-relay discovery response (with the RSC received in step 1) and does not contain a direct discovery set.

[0100] ...

[0101] 6.7.1.1 Layer 2 Link Establishment for PC5 Communication via 5G ProSe Layer 3 UE Inter-relay

[0102] Figure 6.7.1.1-1 illustrates the process of establishing a Layer 2 link via 5G ProSe Layer 3 UE inter-relay.

[0103] Figure 7 is a reproduction of Figure 6.7.1.1-1 of 3GPP TS 23.304 v18.5.1: Establishment of a Layer 2 Link via 5G ProSe Layer 3 UE inter-relay.

[0104] 1. Service authorization and pre-configuration are performed for the source 5G ProSe Layer 3 UE, the target 5G ProSe Layer 3 UE, and the 5G ProSe Layer 3 UE inter-relay as described in Clause 6.2.

[0105] 2. The source 5G ProSe Layer 3 UE performs the discovery of the 5G ProSe Layer 3 UE inter-relay as described in Clause 6.3.2.4.

[0106] 3. The source 5G ProSe Layer 3 UE sends a direct communication request message to initiate a unicast Layer 2 link establishment process using the 5G ProSe Layer 3 UE inter-relay. The parameters included in the direct communication request message are described in Clause 6.4.3.7.

[0107] The source Layer 2 ID of the direct communication request message is assigned by the source 5G ProSe Layer 3 UE itself, and the destination Layer 2 ID is set to the source Layer 2 ID of the discovery message of the 5G ProSe Layer 3 UE inter-relay.

[0108] As described in Clause 5.6.3.1, the source 5G ProSe Layer 3 UE obtains application information and optional ProSe application requirements from the ProSe application layer and determines the inter-terminal QoS parameters.

[0109] 4. If the user information ID of the 5G ProSe Layer 3 UE inter-relay in the direct communication request message matches the user information ID of the 5G ProSe UE inter-relay, and the RSC in the direct communication request matches an RSC (pre-)configured by the relay, as specified in Clause 5.1.5.1, then the 5G ProSe Layer 3 UE inter-relay responds by establishing security with the source 5G ProSe Layer 3 UE. When security protection is enabled, the source 5G ProSe Layer 3 UE sends the parameters described in Clause 6.4.3.7 to the 5G...ProSe Layer 3 UE Inter-Relay.

[0110] If the Ethernet MAC address of the source 5G ProSe Layer 3 UE is already used by another 5G ProSe Layer 3 UE, the 5G ProSe Layer 3 UE Inter-Relay refuses to establish a direct link, indicating that the MAC address is not unique.

[0111] The source layer 2 ID used for the security establishment process is assigned by the 5G ProSe Layer 3 UE Inter-Relay itself, and the destination layer 2 ID is set to the source layer 2 ID of the received direct communication request message.

[0112] The 5G ProSe Layer 3 UE Inter-Relay will select different source layer 2 IDs for PC5 links of different types of services (i.e., IP services, Ethernet services, and unstructured services).

[0113] If the PC5 link is used to transmit unstructured services, the 5G ProSe Layer 3 UE Inter-Relay will select different source layer 2 IDs for different pairs of source and destination 5G ProSe Layer 3 UEs.

[0114] Upon receiving the security establishment process message, the source 5G ProSe Layer 3 UE obtains the Layer 2 ID of the 5G ProSe Layer 3 UE inter-relay for signaling and data services used for this unicast link for future communication.

[0115] 5. After the security establishment process in step 4 is completed, the 5G ProSe Layer 3 UE inter-relay decides whether to use its existing unicast Layer 2 link with the target 5G ProSe UE for the required service. If there is no existing unicast Layer 2 link between the required RSC and the target 5G ProSe Layer 3 UE, the 5G ProSe Layer 3 UE inter-relay sends a direct communication request message to initiate a unicast Layer 2 link establishment process with the target 5G ProSe Layer 3 UE. The parameters included in the direct communication request message are described in clause 6.4.3.7.

[0116] The source Layer 2 ID of the direct communication request message is assigned by the 5G ProSe Layer 3 UE inter-relay itself, and the destination Layer 2 ID can be a broadcast or unicast Layer 2 ID. Unicast Layer 2 IDs are used only when the Layer 2 ID of the target 5G ProSe Layer 3 UE associated with the User Information ID is known to the 5G ProSe Layer 3 UE inter-relay.

[0117] The 5G ProSe Layer 3 UE inter-relay will select different source Layer 2 IDs for PC5 links of different types of services (i.e., IP services, Ethernet services, and unstructured services).

[0118] If the PC5 link is used to transmit unstructured services, the 5G ProSe Layer 3 UE inter-relay will select different source Layer 2 IDs for different pairs of source and target 5G ProSe Layer 3 UEs.

[0119] 6. If the User Information ID and RSC of the target 5G ProSe Layer 3 UE contained in the direct communication request match the User Information ID of the target UE and the (pre-)configured RSC of the target UE, as in Clause 5.1As specified in .5.1, the target 5G ProSe Layer 3 UE responds by establishing security with the 5G ProSe Layer 3 UE inter-relay. When security protection is enabled, the 5G ProSe Layer 3 UE inter-relay sends the parameters described in clause 6.4.3.7 to the target 5G ProSe Layer 3 UE.

[0120] The source Layer 2 ID used for the security establishment process is assigned by the target 5G ProSe Layer 3 UE itself, and the destination Layer 2 ID is set to the source Layer 2 ID of the received direct communication request message.

[0121] Upon receiving the security establishment process message, the 5G ProSe Layer 3 UE inter-relay obtains the Layer 2 ID of the target 5G ProSe Layer 3 UE for signaling and data services for this unicast link for future communication.

[0122] 7. The target 5G ProSe Layer 3 UE sends a direct communication accept message to the 5G ProSe Layer 3 UE inter-relay with which it has successfully established security. The parameters included in the direct communication accept message are described in Clause 6.4.3.7.

[0123] Note: When the 5G ProSe Layer 3 UE inter-relay receives the direct communication accept message, it can detect that the Ethernet MAC address of the target 5G ProSe Layer 3 UE is already being used by another 5G ProSe Layer 3 UE.

[0124] 8. As defined in Clause 5.5.1.4, for IP services, an IPv6 prefix or IPv4 address is assigned to the target 5G ProSe Layer 3 UE.

[0125] 9. After receiving the direct communication accept message from the target 5G ProSe Layer 3 UE, the 5G ProSe Layer 3 UE inter-relay sends the direct communication accept message to the source 5G ProSe Layer 3 UE with which it has successfully established security. The parameters included in the direct communication accept message are described in Clause 6.4.3.7.

[0126] 10. As defined in Clause 5.5.1.4, for IP services, an IPv6 prefix or IPv4 address is assigned to the source 5G ProSe Layer 3 UE.

[0127] 11. For IP communication, the 5G ProSe layer 3 UE inter-relay can store the association between 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 inter-relay can 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, the source 5G ProSe layer 3 UE can send a DNS query to the 5G ProSe layer 3 UE inter-relay after step 10 to request the IP address of the target 5G ProSe layer 3 UE, and the 5G ProSe layer 3 UE inter-relay will send the target 5G ProSe layer 3 UE's IP address to the 5G ProSe layer 3 UE inter-relay.The IP address of the ProSe layer 3 end UE is transmitted back to the source 5G ProSe layer 3 end UE.

[0128] For Ethernet communication, the 5G ProSe layer 3 UE inter-relay maintains the association between the PC5 link and the Ethernet MAC address received from the 5G ProSe layer 3 end UE.

[0129] For unstructured service communication, for each pair of source and target 5G ProSe layer 3 end UEs, the 5G ProSe layer 3 UE inter-relay maintains a 1:1 mapping between the PC5 link and the source 5G ProSe layer 3 end UE and between the PC5 link and the target 5G ProSe layer 3 end UE.

[0130] 12. The source 5G ProSe layer 3 end UE communicates with the target 5G ProSe layer 3 end UE via the 5G ProSe layer 3 UE inter-relay.

[0131] …

[0132] 6.7.2 5G ProSe communication via 5G ProSe layer 2 UE inter-relay

[0133] This procedure applies to 5G ProSe layer 2 UE inter-relay.

[0134] Figure 8 is Figure 6.7.2-1 of 3GPP TS 23.304 v18.5.1: a reproduction of 5G ProSe communication via 5G ProSe Layer 2 UE Inter-Relay.

[0135] As described in Clause 6.2, service authorization and provisioning have been performed for the 5G ProSe Layer 2 UE Inter-Relay and the 5G ProSe end UE prior to this procedure.

[0136] 1. Perform Model A or Model B 5G ProSe UE Inter-Relay discovery as described in Clause 6.3.2.4, and the source 5G ProSe end UE selects a suitable 5G ProSe Layer 2 UE Inter-Relay for communication with the target 5G ProSe end UE.

[0137] 2. The source 5G ProSe end UE decides whether to use the existing PC5 link with the 5G ProSe UE Inter-Relay to obtain the required service. If an existing PC5 link is used, the Layer 2 link modification procedure specified in Clause 6.4.3.7 is used for the 5G ProSe UE-to-UE relay; otherwise, the Layer 2 link establishment procedure is used for the 5G ProSe UE-to-UE relay.

[0138] This procedure is for the selected 5G ProSe UE-to-UE relay, and for Layer 2 link establishment, security establishment is performed before initiating step 3.

[0139] 3. The 5G ProSe Layer 2 UE-to-UE relay determines whether to use the existing PC5 link between the 5G ProSe UE-to-UE relay and the target 5G ProSe UE to obtain the required service, and initiates the Layer 2 link establishment procedure or Layer 2 link modification procedure with the target 5G ProSe UE as specified in Clause 6.4.3.7.

[0140] If for the target 5GWhen the ProSe end UE performs a Layer 2 link establishment procedure, it uses either a broadcast or unicast Layer 2 ID as the destination Layer 2 ID. If the Layer 2 ID of the target 5G ProSe Layer 2 end UE associated with the user information ID of the target 5G ProSe Layer 2 end UE is known to the 5G ProSe Layer 2 UE inter-relay, the unicast Layer 2 ID is used.

[0141] If a Layer 2 link modification procedure is performed for the target 5G ProSe end UE, the procedure uses the unicast Layer 2 ID of the target 5G ProSe end UE as the destination Layer 2 ID.

[0142] After step 3 is completed, the 5G ProSe Layer 2 UE inter-relay sends a direct communication acceptance message or a link modification acceptance message to the source 5G ProSe end UE.

[0143] 4. As described in Clause 6.4.3.7, the source 5G ProSe end UE and the target 5G ProSe end UE establish an inter-end connection for unicast mode communication.

[0144] Data and inter-terminal PC5-S signaling are transmitted between the source 5G ProSe UE and the target 5G ProSe UE via the 5G ProSe Layer 2 UE-to-UE relay. As specified in TS 38.300

[12] , the 5G ProSe Layer 2 UE-to-UE relay forwards all data services and inter-terminal PC5-S signaling between the source 5G ProSe UE and the target 5G ProSe UE.

[0145] …

[0146] 6.7.4 5G ProSe UE-to-UE Relay Reselection

[0147] 6.7.4.1 General

[0148] After connecting to the 5G ProSe UE-to-UE relay, the 5G ProSe UE may trigger 5G ProSe UE-to-UE relay reselection based on the conditions specified in TS 38.300

[12] (e.g., the measured signal strength of the PC5 unicast link with the 5G ProSe UE-to-UE relay).

[0149] For 5G ProSe inter-UE relay reselection, 5G ProSe inter-UE relays can be discovered through the discovery process defined in Clause 6.3.2.4 or through the agreed 5G ProSe inter-UE relay reselection process defined in Clause 6.7.4.2 or Clause 6.7.4.3.

[0150] In the agreed inter-UE relay reselection process defined in Clause 6.7.4.2 or Clause 6.7.4.3, a 5G ProSe end UE initiates an inter-UE relay reselection process. The 5G ProSe end UE can use the existing connection to negotiate a new 5G ProSe inter-UE relay and establish communication via the reselected 5G ProSe inter-UE relay before releasing communication via the current 5G ProSe inter-UE relay.

[0151] 6.7.4.2 Agreed 5G ProSe Layer 2 Inter-UE Relay Reselection

[0152] Figure 6.7.4.2-1 depicts the agreed 5G...The process of ProSe layer 2 UE inter-relay reselection.

[0153] Figure 9 is Figure 6.7.4.2-1 of 3GPP TS 23.304 v18.5.1: Agreed 5G ProSe layer 2 UE inter-relay reselection.

[0154] 1. Based on the process defined in clause 6.7.2, a PC5 unicast link is established between 5G ProSe end UEs via 5G ProSe UE inter-relay.

[0155] 2. The initiating 5G ProSe end UE determines to perform UE inter-relay reselection, for example, based on PC5 signal strength, and obtains a list of candidate UE inter-relays according to RSC. The initiating 5G ProSe end UE can receive UE inter-relay discovery announcement messages from 5G ProSe UE inter-relays, or initiate a 5G ProSe UE inter-relay discovery process to find candidate 5G ProSe UE inter-relays. The initiating 5G ProSe UE determines candidate 5G ProSe inter-UE relays based, for example, on the PC5 signal strength of the received inter-UE relay discovery announcement message and the RSC in the announcement message (page 11 / 68 of the Inter-UE Relay Discovery Specification, CN 121218295 A). The candidate 5G ProSe inter-UE relays support the same RSC associated with the PC5 unicast link between the initiating 5G ProSe UE and the 5G ProSe inter-UE relay.

[0156] 3. The initiating 5G ProSe UE sends a link modification request message to the responding 5G ProSe UE, the link modification request message containing a relay reselection indication, the user information ID of the candidate 5G ProSe inter-UE relay, and the Layer 2 ID and security information of the optional candidate 5G ProSe inter-UE relay.

[0157] 4. The responding 5G ProSe UE selects a new 5G ProSe inter-UE relay from the candidate 5G ProSe inter-UE relays based on the relay reselection indication in the link modification request message and according to the RSC. If the responding 5G ProSe UE has not yet received an inter-UE relay discovery announcement message from a candidate 5G ProSe inter-UE relay (e.g., during a previous 5G ProSe inter-UE relay discovery process) or does not have a PC5 connection with a candidate 5G ProSe inter-UE relay associated with the same RSC, the responding 5G ProSe UE may perform the candidate 5G ProSe inter-UE relay discovery process as defined in Clause 6.3.2.4.4. The responding 5G ProSe UE sets the candidate relay user information ID to the relay user information ID of the candidate 5G ProSe inter-UE relay in the discovery message, and may set the layer 2 ID of the candidate 5G ProSe inter-UE relay (if received in step 3) to carry...The destination layer 2 ID of the discovery message. The PC5 signal strength of the inter-UE relay discovery announcement message or inter-UE relay discovery response message can be used to select the new 5G ProSe inter-UE relay.

[0158] 5. The 5G ProSe end UE sends a link modification accept message to the initiating 5G ProSe end UE, containing the user information ID and security information of the new 5G ProSe inter-UE relay.

[0159] 6. The 5G ProSe end UE establishes a PC5 unicast link with the new 5G ProSe inter-UE relay (if it has not yet been established) by reusing the procedure defined in clause 6.7.2, and the PC5 unicast is a link established between 5G ProSe end UEs via the new 5G ProSe inter-UE relay. The 5G ProSe end UE switches data services via the new 5G ProSe inter-UE relay. The security information is used to verify that the new link has been successfully established.

[0160] 6.7.4.3 Agreeing on 5G ProSe Layer 3 UE Inter-Relay Reselection

[0161] Figure 6.7.4.3-1 depicts the process of agreeing on 5G ProSe Layer 3 UE Inter-Relay Reselection.

[0162] Figure 10 is a reproduction of Figure 6.7.4.3-1 of 3GPP TS 23.304 v18.5.1: Agreeing on 5G ProSe Layer 3 UE Inter-Relay Reselection.

[0163] 1. Based on the process defined in Clause 6.7.1, the 5G ProSe end UE has established a PC5 unicast link with the 5G ProSe UE Inter-Relay.

[0164] 2. Based on the process defined in Clause 6.7.1, the 5G ProSe end UE has further established a PC5 unicast link with the 5G ProSe UE Inter-Relay.

[0165] 3. The 5G ProSe end UE transmits services via the 5G ProSe UE Inter-Relay.

[0166] 4. The 5G ProSe initiating UE determines the inter-UE relay reselection based, for example, on PC5 signal strength, and obtains a list of candidate inter-UE relays according to RSC. The 5G ProSe initiating UE can receive an inter-UE relay discovery announcement message from the 5G ProSe inter-UE relay, or initiate a 5G ProSe inter-UE relay discovery process to find candidate 5G ProSe inter-UE relays. The 5G ProSe initiating UE determines the candidate 5G ProSe inter-UE relays based, for example, on the PC5 signal strength of the received inter-UE relay discovery announcement message and the RSC in the inter-UE relay discovery announcement message. The candidate 5G ProSe inter-UE relays support the same RSC associated with the PC5 unicast link between the 5G ProSe initiating UE and the 5G ProSe inter-UE relay.

[0167] 5. The 5G ProSe initiating UE sends a response to the 5G ProSe...The UE-to-UE relay sends a link modification request message, which includes a relay reselection indication, a user information ID of a candidate 5G ProSe UE-to-UE relay, the IP address of the responding 5G ProSe UE, and a Layer 2 ID of an optional candidate 5G ProSe UE-to-UE relay.

[0168] When the initiating 5G ProSe UE communicates with multiple 5G ProSe UEs via a 5G ProSe UE-to-UE relay, the IP addresses of multiple 5G ProSe UEs can be included as described on page 12 / 68 of the specification, CN 121218295 A.

[0169] 6. The 5G ProSe UE-to-UE relay determines the responding 5G ProSe UE based on the IP address received from the initiating 5G ProSe UE and sends a link modification request message to the responding 5G ProSe UE. The link modification request message includes a relay reselection indication, a user information ID of a candidate 5G ProSe UE-to-UE relay, the IP address of the initiating 5G ProSe UE, and a Layer 2 ID of an optional candidate 5G ProSe UE-to-UE relay.

[0170] If multiple 5G ProSe UEs are specified in the link modification request message received from the initiating 5G ProSe UE, the 5G ProSe UE-to-UE relay sends a PC5 link modification request to each 5G ProSe UE.

[0171] 7. The responding 5G ProSe UE selects a new 5G ProSe UE-to-UE relay from the candidate 5G ProSe UE-to-UE relays according to the RSC based on the relay reselection indication in the link modification request message. If the responding 5G ProSe UE has not yet received an inter-UE relay discovery announcement message from a candidate 5G ProSe UE-to-UE relay (e.g., during a previous 5G ProSe UE-to-UE relay discovery process) or does not have a PC5 connection with a candidate 5G ProSe UE-to-UE relay associated with the same RSC, the responding 5G ProSe UE may perform the candidate 5G ProSe UE-to-UE relay discovery process as defined in Clause 6.3.2.4.4. The 5G ProSe end UE sets the candidate relay user information ID to the relay user information ID of the candidate 5G ProSe inter-UE relay in the discovery message, and can set the layer 2 ID of the candidate 5G ProSe inter-UE relay (if received in step 6) to the destination layer 2 ID carrying the discovery message. The 5G ProSe end UE can initiate the process of establishing a PC5 unicast link with the new 5G ProSe inter-UE relay by reusing the procedure defined in clause 6.7.1. The PC5 signal strength of the inter-UE relay discovery announcement message or the inter-UE relay discovery response message can be used to select the new 5G ProSe inter-UE relay.

[0172] 8. Response 5GThe ProSe UE sends a link modification acceptance message to the 5G ProSe UE inter-relay. The link modification acceptance message includes the user information ID of the new 5G ProSe UE inter-relay, the IP address of the initiating 5G ProSe UE, the IP address of the responding 5G ProSe UE for communication via the newly selected 5G ProSe UE inter-relay, and a relay reselection indication.

[0173] 9. The 5G ProSe UE inter-relay sends a link modification acceptance message to the initiating 5G ProSe UE. The link modification acceptance message includes the user information ID of the new 5G ProSe UE inter-relay, the IP address of the responding 5G ProSe UE, the IP address of the responding 5G ProSe UE for communication via the newly selected 5G ProSe UE inter-relay, and a relay reselection indication.

[0174] 10-11. A link modification confirmation is sent from the initiating 5G ProSe UE to the responding 5G ProSe UE via a 5G ProSe UE inter-relay, the link modification confirmation including the IP address of the initiating 5G ProSe UE, the IP address of the responding 5G ProSe UE, and a relay reselection indication for communication via the newly selected 5G ProSe UE inter-relay.

[0175] 12. The 5G ProSe UE transmits services via the newly selected 5G ProSe UE inter-relay.

[0176] === ... The purpose of the ProSe direct link modification process is to modify the existing ProSe direct link as follows:

[0182] a) Add a new PC5 QoS flow to the existing 5G ProSe direct link; Specification 13 / 68 pages 16 CN 121218295 A

[0183] b) Modify the existing PC5 QoS flow to update the PC5 QoS parameters of the existing PC5 QoS flow;

[0184] c) Modify the existing PC5 QoS flow to associate the new ProSe application with the existing PC5 QoS flow;

[0185] d) Modify the existing PC5 QoS flow to transfer the new ProSe application from the existing PC5 QoS flow.Remove associated ProSe applications from QoS flows;

[0186] e) Remove existing PC5 QoS flows from existing 5G ProSe direct links;

[0187] f) Negotiate new 5G ProSe UE-to-UE relay UEs via existing 5G ProSe direct links;

[0188] g) Establish 5G ProSe UE-to-UE relay communication with an additional 5G ProSe UE using existing 5G ProSe direct links between 5G ProSe layer 3 UEs and 5G ProSe layer 3 UE-to-UE relay UEs;

[0189] h) Release 5G ProSe UE-to-UE relay communication with one of the peer 5G ProSe layer 3 UEs using shared 5G ProSe direct links between 5G ProSe layer 3 UEs and 5G ProSe layer 3 UE-to-UE relay UEs; or

[0190] i) Establish 5G ProSe UE-to-UE communication with an additional 5G ProSe layer 2 UE using existing 5G ProSe direct links between 5G ProSe layer 2 UEs and 5G ProSe layer 2 UE-to-UE relay UEs. Inter-UE relay communication.

[0191] In this process, 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".

[0192] 7.2.3.2 5G ProSe Direct Link Modification Process Initiated by the Initiating UE

[0193] Before initiating this process of adding a new ProSe application to an existing 5G ProSe direct link, the initiating UE will meet the following prerequisites:

[0194] a) There is a 5G ProSe direct link between the initiating UE and the target UE;

[0195] b) The pair of application layer IDs and network layer protocols of this 5G ProSe direct link are the same as the application layer IDs and network layer protocols required by the application layer in the initiating UE for this ProSe application;

[0196] c) The security policy corresponding to the ProSe identifier is consistent with the security policy of the existing 5G ProSe direct link;

[0197] d) Timer T5091 is not running; and

[0198] e) The initiating UE has not performed the 5G ProSe direct link key update process initiated by the target UE.

[0199] Before initiating the process of negotiating a new 5G ProSe UE-to-UE relay UE via an existing 5G ProSe direct link, the initiating UE must meet the following prerequisites:

[0200] a) A 5G ProSe direct link exists between the initiating UE and the target UE;

[0201] b) The initiating UE is a source 5G ProSe UE that communicates with the target 5G ProSe UE via a 5G ProSe UE-to-UE relay UE;

[0202] c) Initiating UE to perform inter-UE relay reselection, for example, based on PC5 signal strength; and

[0203] d) Initiating UE to obtain a list of candidate inter-UE relays via an inter-UE discovery process.

[0204] Before initiating the process of establishing 5G ProSe UE-to-UE relay communication with an additional 5G ProSe Layer 3 UE via an existing 5G ProSe direct link, the initiating UE will meet the following prerequisites:

[0205] a) There is a 5G ProSe direct link between the initiating UE and the target UE;

[0206] b) The initiating UE acts as a 5G ProSe Layer 3 UE, and the target UE acts as a 5G ProSe Layer 3 UE-to-UE relay UE, and vice versa;

[0207] c) If the initiating UE acts as a 5G ProSe Layer 3 UE, it determines to communicate with the additional 5G ProSe Layer 3 UE using the same RSC as the existing 5G ProSe direct link; and

[0208] d) If the initiating UE acts as a 5G ProSe Layer 3 UE-to-UE relay UE, it receives a request from another 5G ProSe Layer 3 UE to communicate with the target UE using the same RSC as the existing 5G ProSe direct link.

[0209] After receiving service data or requests from the upper layer, the initiating UE will perform flow matching as specified in Clause 7.2.8 (PC5 QoS Specification, page 14 / 68, 17 CN 121218295 A). If no matching PC5 QoS flow exists, the initiating UE will export the PC5 QoS parameters and assign a PQFI to the PC5 QoS flow to be established as specified in Clause 7.2.7.

[0210] If the 5G ProSe direct link modification procedure is to add a new PC5 QoS flow to an existing 5G ProSe direct link, the initiating UE will create a PROSE DIRECT LINK MODIFICATION REQUEST message. In this message, the initiating UE:

[0211] a) will include PQFI, corresponding PC5 QoS parameters, and an optional ProSe identifier;

[0212] b) will include a link modification operation code set to "add a new PC5 QoS flow to an existing 5G ProSe direct link";

[0213] c) may include PC5 QoS rules to indicate the packet filter for the PC5 QoS flow;

[0214] d) if the UE is acting as a 5G ProSe layer 3 UE inter-relay UE, the 5G ProSe direct link is between the 5G ProSe layer 3 UE inter-relay UE and the target 5G ProSe layer 3 end UE, and multiple source 5G ProSe layer 3 end UEs have already used the same 5G ProSe direct link via the 5G ProSe layer 3 UE inter-relay UE to the target 5G ProSe layer 3 end UE.If a ProSe layer 3 end UE establishes direct communication, then the source UE information, which includes user information set as the source 5G ProSe layer 3 end UE, will be included;

[0215] e) If the UE acts as a 5G ProSe inter-UE relay UE, the 5G ProSe direct link is between the 5G ProSe inter-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 inter-UE relay UE using the 5G ProSe direct link, then the source UE information, which includes user information set as the source 5G ProSe end UE, will be included;

[0216] f) 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 inter-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 same 5G ProSe direct link using the 5G ProSe layer 3 UE inter-UE relay UE, then the source UE information, which includes user information set as the target 5G ProSe layer 3 end UE, will be included.

[0217] g) If the following conditions exist, the target UE information of the user information of the target 5G ProSe UE may be included:

[0218] 1) The UE acts as the source 5G ProSe UE, the 5G ProSe direct link is between the source 5G ProSe UE and the 5G ProSe UE inter-relay UE, and the source 5G ProSe UE has established direct communication with only one target 5G ProSe UE via the 5G ProSe UE inter-relay UE using the 5G ProSe direct link; or

[0219] 2) The UE acts as the 5G ProSe UE inter-relay UE, and the 5G ProSe direct link is between the 5G ProSe UE inter-relay UE and the target 5G ProSe UE; and

[0220] h) If the UE acts as the source 5G ProSe UE and the 5G ProSe direct link is between the source 5G ProSe UE and the 5G ProSe UE inter-relay UE, the target UE information of the user information of the target 5G ProSe UE may be included. The target UE's Layer 2 ID is the Layer 2 ID of the ProSe UE.

[0221] If the 5G ProSe direct link modification process modifies 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:

[0222] a) includes PQFI and the corresponding PC5QoS parameters, including ProSe identifier;

[0223] b) will include a link modification operation code set to "modify PC5 QoS parameters of existing PC5 QoS flow";

[0224] c) may include PC5 QoS rules to indicate packet filters for PC5 QoS flow;

[0225] d) if the UE acts as a 5G ProSe layer 3 UE relay UE, and the 5G ProSe direct link is between the 5G ProSe layer 3 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, then source end UE information set as user information of the source 5G ProSe layer 3 end UE will be included;

[0226] e) if the UE acts as a 5G ProSe UE relay UE, and the 5G ProSe direct link is between the 5G ProSe layer 3 UE relay UE and the target 5G ProSe layer 3 end UE, then source end UE information set as user information of the source 5G ProSe layer 3 end UE will be included; If a UE acts as a source 5G ProSe layer 3 UE, and a 5G ProSe direct link has been established between the source 5G ProSe layer 3 UE and the target 5G ProSe layer 3 UE via the 5G ProSe layer 3 UE relay UE, and only one source 5G ProSe layer 3 UE has established direct communication with the target 5G ProSe layer 3 UE via the 5G ProSe layer 3 UE relay UE using the same 5G ProSe direct link, then the target UE information containing the user information of the target 5G ProSe layer 3 UE will be included;

[0228] g) If the following conditions exist, the target UE information containing the user information of the target 5G ProSe layer 3 UE can be included:

[0229] 1) The UE acts as a source 5G ProSe layer 3 UE, and a 5G ProSe direct link has been established between the source 5G ProSe layer 3 UE and the 5G ProSe layer 3 UE relay UE, and the source 5G ProSe layer 3 UE has established direct communication with multiple target 5G ProSe layer 3 UEs via the 5G ProSe layer 3 UE relay UE using the same 5G ProSe direct link, then the target UE information containing the user information of the target 5G ProSe layer 3 UE will be included;

[0228] g) If the following conditions exist, the target UE information containing the user information of the target 5G ProSe layer 3 UE can be included:

[0229] 1) The UE acts as a source 5G ProSe layer 3 UE, and a 5G ProSe direct link has been established between the source 5G ProSe layer 3 UE and the target 5G ProSe layer 3 UE via the 5G ProSe layer 3 UE relay UE. The ProSe direct link is between the source 5G ProSe UE and the 5G ProSe UE inter-relay UE, and the source 5G ProSe UE has already established direct communication with only one target 5G ProSe UE via the 5G ProSe UE inter-relay UE using the 5G ProSe direct link; or

[0230] 2) The UE acts as a 5G ProSe UE inter-relay UE, and the 5G ProSe direct link is between the 5G ProSe UE inter-relay UE and the target 5G ProSe UE.Between ProSe end UEs; and

[0231] h) 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 relay UE between the 5G ProSe UEs, then the target end UE layer 2 ID set as the destination layer 2 ID of the target 5G ProSe end UE may be included.

[0232] If the 5G ProSe direct link modification process is to associate a new ProSe application with an existing PC5 QoS flow, then the initiating UE will create a PROSE DIRECT LINK MODIFICATION REQUEST message. In this message, the initiating UE:

[0233] a) will include PQFI and corresponding PC5 QoS parameters, including the ProSe identifier;

[0234] b) will include a link modification operation code set to "associate the new ProSe application with an existing PC5 QoS flow";

[0235] c) may include PC5 QoS rules to indicate the packet filter of the PC5 QoS flow;

[0236] d) if the UE acts as a 5G ProSe layer 3 UE relay UE, the 5G ProSe direct link is between the 5G ProSe layer 3 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 relay UE, then the source end UE information set as the user information of the source 5G ProSe layer 3 end UE will be included;

[0237] e) if the UE acts as a 5G ProSe UE relay UE, the 5G ProSe direct link is between the 5G ProSe layer 3 UE relay UE and the target 5G ProSe layer 3 end UE, then the source end UE information set as the user information of the source 5G ProSe layer 3 end UE will be included;

[0237] e) if the UE acts as a 5G ProSe UE relay UE, the 5G ProSe direct link is between the 5G ProSe layer 3 UE relay UE and the target 5G ProSe layer 3 end UE via the same 5G ProSe direct link through the 5G ProSe layer 3 UE relay UE, then the source end UE information set as the user information of the source 5G ProSe layer 3 end UE will be included; If a UE is a source 5G ProSe layer 3 UE, and a 5G ProSe direct link has been established between the source 5G ProSe layer 3 UE and the target 5G ProSe layer 3 UE via the 5G ProSe layer 3 UE relay UE, and only one source 5G ProSe layer 3 UE has established direct communication with the target 5G ProSe layer 3 UE via the 5G ProSe layer 3 UE relay UE using the same 5G ProSe direct link, then the source UE information, which includes the user information of the source 5G ProSe layer 3 UE, can be included;

[0238] f) If the UE acts as a source 5G ProSe layer 3 UE, and a 5G ProSe direct link is established between the source 5G ProSe layer 3 UE and the 5G ProSe layer 3 UE relay UE, and the source 5G ProSe layer 3 UE has established direct communication with multiple target 5G ProSe layer 3 UEs via the 5G ProSe layer 3 UE relay UE using the same 5G ProSe direct link, then the target UE information, which includes the user information of the target 5G ProSe layer 3 UE, can be included;

[0239] g) If the following conditions exist, then the user information of the target 5G ProSe layer 3 UE can be included.Target Specification for User Information of ProSe End UE 16 / 68 pages 19 CN 121218295 A End UE Information:

[0240] 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 5G ProSe UE inter-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 inter-relay UE using the 5G ProSe direct link; or

[0241] 2) The UE acts as the 5G ProSe UE inter-relay UE, and the 5G ProSe direct link is between the 5G ProSe UE inter-relay UE and the target 5G ProSe end UE; and

[0242] h) 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 5G ProSe UE inter-relay UE, then the target end UE layer 2 ID set as the layer 2 ID of the target 5G ProSe end UE may be included.

[0243] If the PC5 5G ProSe direct link modification process removes an associated ProSe application from an existing PC5 QoS flow, the initiating UE will create a PROSE DIRECT LINK MODIFICATION REQUEST message. In this message, the initiating UE:

[0244] a) will include a PQFI and corresponding PC5 QoS parameters, including a ProSe identifier; and

[0245] b) will include a link modification operation code set to "remove ProSe application from existing PC5 QoS flow".

[0246] If the direct link modification process removes any PC5 QoS flow from an existing 5G ProSe direct link, the initiating UE will create a PROSE DIRECT LINK MODIFICATION REQUEST message. In this message, the initiating UE:

[0247] a) will include a PQFI; and

[0248] b) will include a link modification operation code set to "remove existing PC5 QoS flow from existing 5G ProSe direct link".

[0249] If the 5G ProSe direct link modification process uses the existing 5G ProSe direct link between the 5G ProSe layer 3 end UE and the 5G ProSe layer 3 UE inter-relay UE to establish 5G ProSe UE inter-relay communication with the additional 5G ProSe layer 3 end UE, the initiating UE will create a PROSE DIRECT LINK MODIFICATION REQUEST message. In this message, the initiating UE:

[0250] a) If the UE acts as a 5G ...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 and the target 5G ProSe layer 3 UE, then the source UE information and the target UE information, which are set as user information of the source 5G ProSe layer 3 UE, received in the PROSE DIRECT LINK ESTABLISHMENT REQUEST message, will be included;

[0251] b) For Ethernet services, 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 and the target 5G ProSe layer 3 UE, then the MAC address of the source 5G ProSe layer 3 UE will be included, and the MAC address of the source 5G ProSe layer 3 UE will be included if the following conditions exist:

[0252] 1) The UE acts as a relay UE between 5G ProSe layer 3 UEs;

[0253] 2) The source 5G ProSe layer 3 UE is a relay UE between 5G ProSe layer 3 UEs; The MAC address of the ProSe layer 3 end UE changes; and

[0254] 3) The 5G ProSe direct link is between the 5G ProSe layer 3 UE relay UE and the source 5G ProSe layer 3 end UE;

[0255] c) 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 relay UE, then the target end UE information will be included, which is set to request additional target 5G ProSe layer 3 end UE user information for 5G ProSe inter-UE relay communication;

[0256] d) The link modification operation code will be included, which is set to "add the new 5G ProSe layer 3 end UE to the existing 5G ProSe direct link";

[0257] e) It may include PQFI and corresponding PC5 QoS parameters, including the ProSe identifier; Specification 17 / 68 pages 20 CN 121218295 A

[0258] f) It may include PC5 QoS rules to indicate PC5 Packet filtering for QoS flows; and

[0259] g) If 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 the 5G ProSe layer 3 UE, then the target end UE layer 2 ID, which is set as the layer 2 ID of the target 5G ProSe layer 3 end UE, may be included.

[0260] If the 5G ProSe direct link modification procedure is to use the existing 5G ProSe direct link between the 5G ProSe layer 2 end UE and the relay UE between the 5G ProSe layer 2 UE to establish a 5G connection with an additional 5G ProSe layer 2 end UE.For ProSe inter-UE relay communication, the initiating UE will create a PROSE DIRECT LINK MODIFICATION REQUEST message. In this message, the initiating UE:

[0261] a) If the UE acts as a 5G ProSe layer 2 UE inter-relay UE and the 5G ProSe direct link is between the 5G ProSe layer 2 UE inter-relay UE and the target 5G ProSe layer 2 end UE, then the source UE information, which is set as the user information of the source 5G ProSe layer 2 end UE, and the target UE information, which is set as the user information of the target 5G ProSe layer 2 end UE, received in the PROSE DIRECT LINK ESTABLISHMENT REQUEST message;

[0262] b) If the UE acts as a source 5G ProSe layer 2 end UE and the 5G ProSe direct link is between the source 5G ProSe layer 2 end UE and the 5G ProSe layer 2 UE inter-relay UE, then the target UE information, which is set as the user information of the additional target 5G ProSe layer 2 end UE requesting 5G ProSe inter-UE relay communication, will be included; and

[0263] c) A link modification operation code set as "add a new 5G ProSe layer 2 end UE to the existing 5G ProSe direct link" will be included.

[0264] If the 5G ProSe direct link modification process uses the shared 5G ProSe direct link between the 5G ProSe layer 3 end UE and the 5G ProSe layer 3 inter-relay UE to release the 5G ProSe inter-UE relay communication with one of the peer 5G ProSe layer 3 end UEs, then the initiating UE will create a PROSE DIRECT LINK MODIFICATION REQUEST message. In this message, the initiating UE:

[0265] a) If the UE acts as a 5G ProSe layer 3 UE inter-relay UE and the 5G ProSe direct link is between the 5G ProSe layer 3 UE inter-relay UE and the 5G ProSe layer 3 end UE, then the source end UE information, which is set as the source user information of the 5G ProSe layer 3 end UE received in the PROSE DIRECT LINK RELEASE REQUEST message, will be included;

[0266] b) 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 layer 3 UE inter-relay UE, then the target end UE information, which is set as the user information of the peer 5G ProSe layer 3 end UE to release the 5G ProSe inter-UE relay communication, will be included; and

[0267] c) The message will include information set as "remove 5G from the existing 5G ProSe direct link".The link modification operation code for the ProSe layer 3 end UE.

[0268] If the 5G ProSe direct link modification process triggers an agreed 5G ProSe layer 3 UE inter-relay reselection, the initiating UE will create a PROSE DIRECT LINK MODIFICATION REQUEST message. In this message:

[0269] a) If the initiating 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 inter-relay UE, the initiating UE:

[0270] 1) will contain a relay reselection indication;

[0271] 2) will contain a list of user information IDs of candidate 5G ProSe UE inter-relay UEs that support the same RSC for existing 5G ProSe direct links;

[0272] 3) if IP communication is used, will contain a list of target 5G ProSe end UE IP addresses / prefixes; and

[0273] 4) may contain support for existing 5G A list of Layer 2 IDs for candidate 5G ProSe UE-to-UE relay UEs with the same RSC for the ProSe direct link; or, as per specification page 18 / 68, 21 CN 121218295 A

[0274] b) If the initiating 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 target 5G ProSe end UE, then the initiating UE:

[0275] 1) will include a relay reselection indication;

[0276] 2) will include a list of user information IDs for candidate 5G ProSe UE-to-UE relay UEs with the same RSC for the existing 5G ProSe direct link;

[0277] 3) if IP communication is used, will include the originating 5G ProSe UE IP address / prefix; and

[0278] 4) may include a list of Layer 2 IDs for candidate 5G ProSe UE-to-UE relay UEs with the same RSC for the existing 5G ProSe direct link.

[0279] If 5G The ProSe direct link modification process triggers an agreed 5G ProSe layer 3 UE inter-relay reselection and the initiating UE acts as a 5G ProSe layer 3 UE inter-relay UE. The initiating UE will then create a ProSe direct link modification request message for each IP address / prefix of the target 5G ProSe layer 3 UE received on the associated ProSe direct link modification request message from the source 5G ProSe layer 3 UE.

[0280] If the 5G ProSe direct link modification process triggers an agreed 5G...In the event of a ProSe layer 2 UE inter-relay reselection, the initiating UE will create a PROSE DIRECT LINK MODIFICATION REQUEST message. This message will contain:

[0281] a) a relay reselection indication;

[0282] b) a list of candidate 5G ProSe inter-UE relay UE user information IDs;

[0283] c) a new MSB containing a KNRP ID; and

[0284] d) a list of candidate 5G ProSe inter-UE relay UE layer 2 IDs.

[0285] After generating the PROSE DIRECT LINK MODIFICATION REQUEST message, the initiating UE passes this message to the lower layer, along 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, and starts timer T5081. When timer T5081 runs, the UE will not send new PROSE DIRECT LINK MODIFICATION REQUEST messages to the same target UE.

[0286] Figure 11 is a reproduction of Figure 7.2.3.2.1 of 3GPP TS 24.554 v18.4.0: 5G ProSe direct link modification process.

[0287] Figure 12 is a reproduction of Figure 7.2.3.2.2 of 3GPP TS 24.554 v18.4.0: 5G ProSe direct link modification process for agreeing on 5G ProSe layer 3 UE inter-relay reselection.

[0288] 7.2.3.3 5G ProSe Direct Link Modification Process Accepted by Target UE

[0289] If the PROSE DIRECT LINK MODIFICATION REQUEST message is accepted, the target UE will respond with the PROSE DIRECT LINK MODIFICATION ACCEPT message.

[0290] If the PROSE DIRECT LINK MODIFICATION REQUEST message is for adding a new ProSe application, adding a new PC5 QoS flow, or modifying any existing PC5 QoS flow in a 5G ProSe direct link, then the target UE:

[0291] a) will include PQFI, the corresponding PC5 QoS parameters, and an optional ProSe identifier accepted by the target UE;

[0292] b) may include PC5 QoS rules to indicate packet filters for PC5 QoS flows;

[0293] c) if the UE acts as the target 5G ProSe layer 3 UE, the 5G ProSe direct link relays the UE and the target 5G ProSe layer 3 UE between 5G ProSe layer 3 UEs.If a UE acts as the target 5G ProSe UE, and the 5G ProSe UE has established direct communication with multiple source 5G ProSe UEs via the same 5G ProSe direct link through a 5G ProSe UE inter-UE relay UE, then the source UE information containing the user information of the source 5G ProSe UE will be included;

[0294] d) If the UE acts as the target 5G ProSe UE, the 5G ProSe direct link is between the 5G ProSe UE inter-UE relay UE and the target 5G ProSe UE, and the target 5G ProSe UE has established direct communication with only one source 5G ProSe UE via the 5G ProSe UE inter-UE relay UE through the same 5G ProSe direct link, then the source UE information containing the user information of the source 5G ProSe UE will be included;

[0295] e) If the UE acts as the 5G ProSe UE inter-UE relay UE, and the 5G ProSe direct link is between the source 5G ProSe UE and the 5G ProSe UE inter-UE relay UE, then the source UE information containing the user information of the source 5G ProSe UE will be included; Between UE inter-relay 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 same 5G ProSe direct link through the 5G ProSe layer 3 UE inter-relay UE, then the target end UE information containing the user information set as the target 5G ProSe end UE will be included; and

[0296] f) If the UE acts as a 5G ProSe UE inter-relay UE, the 5G ProSe direct link is between the source 5G ProSe end UE and the 5G ProSe UE inter-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 inter-relay UE using the 5G ProSe direct link through the 5G ProSe UE inter-relay UE, then the target end UE information containing the user information set as the target 5G ProSe end UE can be included;

[0297] The above are included in the PROSE DIRECT LINK MODIFICATION ACCEPT message.

[0298] If the PROSE DIRECT LINK MODIFICATION REQUEST message removes an existing ProSe application from the 5G ProSe direct link, the target UE will remove the ProSe identifier and corresponding PQFI and PC5 QoS parameters received in the PROSE DIRECT LINK MODIFICATION REQUEST message from the profile associated with the 5G ProSe direct link.

[0299] If the PROSE DIRECT LINKThe MODIFICATION REQUEST message removes an existing PC5 QoS flow from the PC5 5G ProSe direct link. The target UE will then remove the PQFI and corresponding PC5 QoS parameters from the profile associated with the 5G ProSe direct link.

[0300] 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, the target UE will provide the added or modified PQFI and corresponding PC5 QoS parameters, along with the PC5 link identifier, to the lower layer after sending the PROSE DIRECT LINK MODIFICATION ACCEPT message.

[0301] 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 will provide the removed PQFI, along with the PC5 link identifier, to the lower layer after sending the PROSE DIRECT LINK MODIFICATION ACCEPT message.

[0302] If the PROSE DIRECT LINK MODIFICATION REQUEST message is used to establish 5G ProSe inter-UE relay communication with an additional 5G ProSe layer 3 UE using an existing 5G ProSe layer 3 end UE and a 5G ProSe layer 3 inter-UE relay UE, then the target UE:

[0303] a) If acting as a 5G ProSe layer 3 inter-UE relay UE, it will perform the 5G ProSe direct link establishment procedure for the target 5G ProSe layer 3 end UE as specified in Clause 7.2.2.2; and after receiving the PROSE DIRECT LINK ESTABLISHMENT ACCEPT message from the target 5G ProSe layer 3 end UE, it will create a PROSE DIRECT LINK MODIFICATION ACCEPT message;

[0304] b) If acting as the target 5G ProSe layer 3 end UE, it will create a PROSE DIRECT LINK MODIFICATION ACCEPT message; and

[0305] c) In the PROSE DIRECT LINK In the MODIFICATION ACCEPT message, the target UE:

[0306] 1) If the UE acts as the target 5G ProSe layer 3 end UE:

[0307] i) will include the source 5GThe source UE information of the user information of the ProSe layer 3 terminal UE and the target UE information of the user information of the target 5G ProSe layer 3 terminal UE; and

[0308] ii) For Ethernet services, if the MAC address of the target 5G ProSe layer 3 terminal UE changes, the MAC address of the target 5G ProSe layer 3 terminal UE will be included; Specification 20 / 68 pages 23 CN 121218295 A

[0309] 2) If the UE acts as a 5G ProSe layer 3 UE inter-UE relay UE:

[0310] i) The target UE information of the user information of the target 5G ProSe layer 3 terminal UE will be included;

[0311] ii) For IP services, the target 5G ProSe layer 3 terminal UE IP address IE that is set as the IP address of an additional target 5G ProSe layer 3 terminal UE may be included; and

[0312] iii) For Ethernet services, the MAC address of the target 5G ProSe layer 3 terminal UE will be included.

[0313] 3) May include PQFI and corresponding PC5 QoS parameters, and optionally include the ProSe identifier of the PC5 QoS flow accepted by the target 5G ProSe layer 3 UE; and

[0314] 4) May include PC5 QoS rules to indicate the packet filter of the PC5 QoS flow.

[0315] If the PROSE DIRECT LINK MODIFICATION REQUEST message is used to establish 5G ProSe inter-UE relay communication with an additional 5G ProSe layer 2 UE using an existing 5G ProSe direct link between the 5G ProSe layer 2 end UE and the 5G ProSe layer 2 inter-UE relay UE, then the target UE:

[0316] a) If acting as a 5G ProSe layer 2 inter-UE relay UE, it will perform the 5G ProSe direct link establishment procedure for the target 5G ProSe layer 2 end UE as specified in Clause 7.2.2.2; and after receiving the PROSE DIRECT LINK ESTABLISHMENT ACCEPT message from the target 5G ProSe layer 2 end UE, it will create a PROSE DIRECT LINK MODIFICATION ACCEPT message;

[0317] b) If acting as the target 5G ProSe layer 2 end UE, it will create a PROSE DIRECT LINK MODIFICATION ACCEPT message; and

[0318] c) In the PROSE DIRECT LINK In the MODIFICATION ACCEPT message, the target UE:

[0319] 1) If the UE acts as the target 5G ProSe layer 2 UE:

[0320] i) Source UE information containing user information set as source 5G ProSe layer 2 end UE and target UE information containing user information set as target 5G ProSe layer 2 end UE; or

[0321] 2) If the UE acts as a 5G ProSe layer 2 UE inter-UE relay UE:

[0322] i) Target UE information containing user information set as target 5G ProSe layer 2 end UE.

[0323] If the PROSE DIRECT LINK MODIFICATION REQUEST message is to release 5G ProSe inter-UE relay communication with one of the peer 5G ProSe layer 3 UEs using a shared 5G ProSe direct link between the 5G ProSe layer 3 end UE and the 5G ProSe layer 3 inter-UE relay UE, then the target UE:

[0324] a) If acting as a 5G ProSe layer 3 inter-UE relay UE, it may initiate one of the following procedures to the target 5G ProSe layer 3 end UE:

[0325] 1) Release the 5G ProSe direct link with the peer 5G ProSe layer 3 end UE as specified in Clause 7.2.6.2; or

[0326] 2) If the UE determines to maintain the 5G ProSe direct link with the peer 5G ProSe layer 3 end UE, remove the corresponding PC5 QoS flow as specified in Clause 7.2.3.2; and

[0327] b) A PROSE DIRECT LINK MODIFICATION ACCEPT message will be created, and in this message, the target UE:

[0328] 1) If the UE acts as the target 5G ProSe layer 3 end UE, then the source end UE information will be included, which is set as the user information of the source 5G ProSe layer 3 end UE; or

[0329] 2) If the UE acts as the 5G ProSe layer 3 UE inter-UE relay UE, then the target end UE information will be included, which is set as the user information of the target 5G ProSe layer 3 end UE.

[0330] If the 5G ProSe direct link is used for 5G ProSe direct communication between the 5G ProSe remote UE and the 5G ProSe layer 3 UE to the network relay UE as specified on page 21 / 68 of the specification, CN 121218295 A, and if the initiating UE is a 5G ProSe remote UE, then the target UE (as the 5G ProSe layer 3 UE to the network relay UE) performs the QoS flow processing procedures as specified in clauses 8.2.6.3.3 and 8.2.6.4.2.

[0331] If the target 5G ProSe end UE accepts PROSE DIRECT LINK MODIFICATIONIf a REQUEST message is sent to trigger inter-UE relay reselection, and a 5G PC5 direct link exists between the 5G ProSe inter-UE relay UE and the target 5G ProSe end UE, then the target UE acting as the target 5G ProSe end UE can perform the candidate 5G ProSe inter-UE relay discovery procedure as specified in Clause 8a.2.3.3. If no such PC5 unicast link exists, the target UE will establish a PC5 unicast link with the selected new 5G ProSe inter-UE relay UE.

[0332] If a PROSE DIRECT LINK MODIFICATION REQUEST message is accepted to trigger agreed 5G ProSe layer 3 inter-UE relay reselection, the target UE will respond with a PROSE DIRECT LINK MODIFICATION ACCEPT message. In this message:

[0333] a) If the target UE acts as the target 5G ProSe layer 3 end UE and the 5G ProSe direct link is between the target 5G ProSe layer 3 end UE and the 5G ProSe layer 3 inter-UE relay UE, then the target UE:

[0334] 1) will contain a relay reselection indication;

[0335] 2) will contain the user information ID of the newly selected 5G ProSe inter-UE relay UE;

[0336] 3) will contain the IP address of the initiating 5G ProSe end UE; and

[0337] 4) if IP communication is used, will contain the IP address of the target 5G ProSe end UE to be used with the newly selected 5G ProSe inter-UE relay UE; and

[0338] b) If the target UE acts as the 5G ProSe layer 3 inter-UE relay UE and the 5G ProSe direct link is between the 5G ProSe layer 3 inter-UE relay UE and the source 5G ProSe layer 3 end UE, then upon receiving a PROSE DIRECT LINK from the target 5G ProSe layer 3 end UE... Following the MODIFICATION ACCEPT message, the target UE will:

[0339] 1) contain a relay reselection indication;

[0340] 2) contain the user information ID of the newly selected 5G ProSe inter-UE relay UE;

[0341] 3) contain the IP address of the target 5G ProSe end UE; and

[0342] 4) if IP communication is used, contain the IP address of the target 5G ProSe end UE to be used with the newly selected 5G ProSe inter-UE relay UE.

[0343] If the PROSE DIRECT LINK MODIFICATION REQUEST message is accepted to trigger the agreed 5G ProSe layer 2 inter-UE relay reselection, the target UE acting as the target 5G ProSe layer 2 end UE will use PROSE...The target UE responds with a PROSE DIRECT LINK MODIFICATION ACCEPT message. In this message:

[0344] a) a new 5G ProSe inter-UE relay UE user information ID is included; and

[0345] b) a new LBS is included with a KNRP ID.

[0346] After generating the PROSE DIRECT LINK MODIFICATION ACCEPT message, the target UE passes this message along with the Layer 2 ID for 5G ProSe direct communication of the initiating UE and the Layer 2 ID for 5G ProSe direct communication of the target UE to the lower layer for transmission.

[0347] If this procedure is performed for an agreed 5G ProSe Layer 3 inter-UE relay reselection, the target UE starts a timer T5096. While timer T5096 is running, the target UE does not send a new PROSE DIRECT LINK MODIFICATION ACCEPT message to the same initiating UE.

[0348] If the target UE accepts the 5G ProSe direct link modification request, the target UE may perform PC5 QoS flow establishment via the 5G ProSe direct link as specified in Clause 7.2.7, and perform PC5 QoS flow matching via the 5G ProSe direct link as specified in Clause 7.2.8. Specification 22 / 68 pages 25 CN 121218295 A

[0349] The target UE will form a new KNRP ID based on the new MSB of the KNRP ID received in the PROSE DIRECT LINK MODIFICATION REQUEST message and the new LSB of the KNRP ID included in the PROSE DIRECT LINK MODIFICATION ACCEPT message. The target UE will replace the existing KNRP ID with the new KNRP ID. The target UE may include the new KNRP ID in the DIRECT LINK ESTABLISHMENT REQUEST message with the initiating UE as specified in Clause 7.2.2.2.

[0350] 7.2.3.4 Initiating the UE to complete the 5G ProSe direct link modification process

[0351] After receiving the PROSE DIRECT LINK MODIFICATION ACCEPT message, the initiating UE will stop timer T5081.

[0352] When receiving the PROSE DIRECT LINK MODIFICATION ACCEPT message, if the PROSE DIRECT LINK MODIFICATION REQUEST message is about adding a new ProSe application or adding a new PC5 in the 5G ProSe direct link...If a QoS flow is added or modified, or any existing PC5 QoS flow is modified, the initiating UE will provide the added or modified PQFI and corresponding PC5 QoS parameters, along with the PC5 link identifier, to the lower layer.

[0353] After receiving the PROSE DIRECT LINK MODIFICATION ACCEPT 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 initiating UE will provide the removed PQFI, along with the PC5 link identifier, to the lower layer.

[0354] Upon receiving the PROSE DIRECT LINK MODIFICATION ACCEPT message, if the initiating UE acts as a 5G ProSe layer 3 UE inter-relay UE, and the PROSE DIRECT LINK MODIFICATION REQUEST message uses the existing 5G ProSe direct link between the 5G ProSe layer 3 end UE and the 5G ProSe layer 3 UE inter-relay UE to establish 5G ProSe layer 3 end UE inter-relay communication, then the initiating UE will send a PROSE DIRECT LINK ESTABLISHMENT ACCEPT message to the source 5G ProSe layer 3 end UE, as specified in Clause 7.2.2.3.

[0355] Upon receiving the PROSE DIRECT LINK MODIFICATION ACCEPT message, if the initiating UE acts as a 5G ProSe layer 3 UE inter-UE relay UE, and the PROSE DIRECT LINK MODIFICATION REQUEST message adds a new PC5 QoS flow or modifies any existing PC5 QoS flow in the existing 5G ProSe direct link, or removes any PC5 QoS flow from the existing 5G ProSe direct link between the 5G ProSe layer 3 end UE and the 5G ProSe layer 3 UE inter-UE relay UE, then the initiating UE will send the PROSE DIRECT LINK MODIFICATION ACCEPT message to the source 5G ProSe layer 3 end UE, as specified in Clause 7.2.3.3.

[0356] When the 5G ProSe direct link is between the source 5G ProSe UE and the relay UE between the 5G ProSe UE, after receiving the PROSE DIRECT LINK MODIFICATION ACCEPT message containing a relay reselection indication, and the PROSE DIRECT LINK MODIFICATION REQUEST message is used to negotiate the 5G ProSe...During inter-UE relay reselection, the initiating UE acting as the source 5G ProSe UE will establish a PC5 unicast link with the newly selected 5G ProSe inter-UE relay UE whose user information ID is included in the PROSE DIRECT LINK MODIFICATION ACCEPT message (if such a PC5 unicast link does not already exist). If the initiating UE acting as the source 5G ProSe Layer 3 UE, the initiating UE will create a PROSE DIRECT LINK MODIFICATION ACK message. In this message, the initiating UE:

[0357] a) If using IP communication, will include a relay reselection indication, a new source UE IP address IE set to the IP address of the source 5G ProSe Layer 3 UE to be used with the newly selected 5G ProSe Layer 3 inter-UE relay UE, and a target UE IP address IE set to the IP address of the target 5G ProSe Layer 3 UE.

[0358] When a 5G ProSe direct link is between a 5G ProSe layer 3 UE relay UE and a target 5G ProSe layer 3 end UE, and the 5G ProSe layer 3 UE relay UE receives a PROSE DIRECT LINK MODIFICATION ACK message containing a relay reselection indication from the source 5G ProSe end UE, the 5G ProSe layer 3 UE relay UE will create a PROSE DIRECT LINK MODIFICATION ACK message. In this message, the 5G ProSe layer 3 UE relay UE: Specification 23 / 68 pages 26 CN 121218295 A

[0359] a) If IP communication is used, the new relay source UE IP address IE, which is set to the IP address of the source 5G ProSe layer 3 end UE to be used with the newly selected 5G ProSe layer 3 UE relay UE, and the source UE IP address IE, which is set to the IP address of the source 5G ProSe layer 3 end UE.

[0360] Upon receiving a PROSE DIRECT LINK MODIFICATION ACCEPT message containing a relay reselection indication, if the PROSE DIRECT LINK MODIFICATION REQUEST message is used for relay reselection, the initiating UE will form a new KNRP ID based on the MSB of the KNRP ID included in the PROSE DIRECT LINK MODIFICATION REQUEST message and the LSB of the KNRP ID received in the PROSE DIRECT LINK MODIFICATION ACCEPT message. The initiating UE will use the new KNRP ID...The new KNRP ID replaces the existing KNRP ID. When the initiating UE reconnects with the same target UE, the initiating UE may include the new KNRP ID in the DIRECT LINK ESTABLISHMENT REQUEST message with the target UE as specified in Clause 7.2.2.2.

[0361] After generating the PROSE DIRECT LINK MODIFICATION ACK message, the initiating UE transmits this message along 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.

[0362] If the source UE confirms acceptance of the 5G ProSe direct link modification, the source UE begins to receive and / or transmit services via the newly selected 5G ProSe inter-UE relay UE.

[0363] If the 5G ProSe direct link modification procedure is used for 5G ProSe direct communication between a 5G ProSe layer 3 UE relay UE and a target 5G ProSe layer 3 UE, for Ethernet services, the PROSE DIRECT LINK MODIFICATION ACCEPT message contains the MAC address of the target 5G ProSe layer 3 UE, and the initiating UE acting as the 5G ProSe layer 3 UE relay detects that the MAC address of the target 5G ProSe layer 3 UE is not unique, that is, the MAC address of the target 5G ProSe layer 3 UE is also provided by another 5G ProSe layer 3 UE in the existing ProSe 5G direct link, then the 5G ProSe layer 3 UE relay UE will execute the 5G ProSe direct link release procedure specified in Clause 7.2.6.

[0364] 7.2.3.4a Target UE completes 5G ProSe direct link modification process

[0365] Upon receiving the PROSE DIRECT LINK MODIFICATION ACK message, the target Layer 3 5G ProSe end UE begins receiving services, transmitting services, or both via the newly selected 5G ProSe inter-UE relay UE, and will stop T5096.

[0366] Upon receiving the PROSE DIRECT LINK MODIFICATION ACK message, the Layer 3 5G ProSe inter-UE relay UE will stop T5096.

[0367] 7.2.3.5 Target UE does not accept 5G ProSe direct link modification process

[0368] If the 5G ProSe direct link modification request cannot be accepted, the target UE will send a PROSE DIRECT LINK MODIFICATION REJECT message.The REJECT message contains a PC5 signaling protocol reason IE, which is set to one of the following reason values:

[0369] #5 Lack of resources for 5G ProSe direct link;

[0370] #6 Required service not allowed;

[0371] #12 Inconsistent security policy;

[0372] #16 Lack of local capability;

[0373] #20 5G ProSe end UE failure;

[0374] #23 MAC address not unique;

[0375] #24 Relay UE not selected for link establishment with integrated discovery; or

[0376] #111 Protocol error, not specified.

[0377] 8a.2.1.3 Using Model B for UE Relay Discovery via PC5 Interface

[0378] 8a.2.1.3.1 General Specification 24 / 68 pages 27 CN 121218295 A

[0379] In the following process, the 5G ProSe end UE that sends the PROSE PC5 DISCOVERY message for the UE relay discovery request is referred to as the "discoverer end UE", and the other 5G ProSe end UE is referred to as the "discoverer end UE".

[0380] 8a.2.1.3.2 Discoverer UE Procedure for Inter-UE Relay Discovery

[0381] 8a.2.1.3.2.1 General

[0382] The purpose of the discoverer UE procedure for inter-UE relay discovery is:

[0383] a) to enable a ProSe-enabled UE to request proximity of a connection service provided by a 5G ProSe inter-UE relay UE, based on a request from an upper layer; or

[0384] b) to enable a ProSe-enabled UE to measure the PROSE PC5 DISCOVERY message signal strength between the ProSe-enabled UE and the 5G ProSe inter-UE relay UE for inter-UE relay selection / reselection.

[0385] 8a.2.1.3.2.2 Discoverer UE Procedure for Inter-UE Relay Discovery

[0386] The UE is authorized to perform the discoverer UE procedure for inter-UE relay discovery if the following conditions exist:

[0387] a) One of the following is true:

[0388] 1) The UE is not served by NG-RAN, is authorized to act as a 5G ProSe end UE for 5G ProSe inter-UE relay UE, and is configured with radio parameters for ProSe inter-UE relay discovery when not served by NG-RAN;

[0389] 2) The UE is served by NG-RAN, is authorized to act as a 5G ProSe end UE toward 5G ProSe inter-UE relay UE; or

[0390] 3) The UE is:

[0391] i) In 5GMM-IDLE mode, is in a limited service state as specified in 3GPP TS 23.122

[14] , and the UEThe reason for being in a limited service state is one of the following:

[0392] A) The UE cannot find a suitable cell in the selected PLMN as specified in 3GPP TS 38.304

[15] ;

[0393] B) The UE receives a REGISTRATION REJECT message or SERVICE REJECT message with 5GMM reason #11 "PLMN not allowed" as specified in 3GPP TS 24.501

[11] ; or

[0394] C) The UE receives a REGISTRATION REJECT message or SERVICE REJECT message with 5GMM reason #7 "5GS service not allowed" as specified in 3GPP TS 24.501

[11] ; and

[0395] ii) When the UE is not served by NG-RAN, the 5G ProSe end UE is authorized to act as a 5G ProSe inter-UE relay UE and is configured with radio parameters for ProSe inter-UE relay discovery when not served by NG-RAN; and

[0396] b) The UE is configured with:

[0397] 1) the relay service code parameters for the connection service to be requested by the 5G ProSe inter-UE relay as specified in Clause 5.2.7, and the UE supports the security procedure for the indicated relay service code;

[0398] Otherwise, the UE is not authorized to perform the discoverer-side UE procedure for inter-UE relay discovery.

[0399] Figure 8a.2.1.3.2.2.1 illustrates the interaction of the UE in the discoverer-side UE procedure for inter-UE relay discovery.

[0400] Figure 13 is a reproduction of Figure 8a.2.1.3.2.2.1: Discoverer-side UE procedure for inter-UE relay discovery in 3GPP TS 24.554 v18.4.0.

[0401] For PROSE PC5 DISCOVERY message signal strength measurement, the UE manages a periodic measurement timer T5111, which is used to trigger periodic PROSE PC5 DISCOVERY message signal strength measurement between the UE and a 5G ProSe inter-UE relay UE with which the UE has established a link. The timer is started whenever the UE has established a direct link with the 5G ProSe inter-UE relay UE, and is restarted whenever the UE receives a PROSE PC5 DISCOVERY message in response to inter-UE relay discovery from a 5G ProSe inter-UE relay UE with which the UE has established a link.

[0402] The timer is also restarted when the UE is triggered by an upper layer to request proximity of the connection service provided by the 5G ProSe inter-UE relay UE to communicate with the target discoverer UE, or when the periodic measurement timer T5111 expires and if the UE is authorized to perform inter-UE relay operations (page 25 / 68, CN).When UE discovers the discoverer's process, the UE:

[0403] a) If the UE is served by NG-RAN and is in 5GMM-IDLE mode, and needs to request resources for sending a PROSE PC5 DISCOVERY message for relay discovery as specified in 3GPP TS 38.331

[13] , the service request process specified in 3GPP TS 24.501

[11] will be executed;

[0404] b) The valid UTC time for discovery transmission will be obtained from the lower layer, and a UTC-based counter corresponding to this UTC time will be generated;

[0405] c) A PROSE PC5 DISCOVERY message for the UE inter-relay discovery request will be generated.

[0406] In the PROSE PC5 DISCOVERY message for a UE-to-UE relay discovery request, the UE:

[0407] 1) will include a direct discovery set IE, which includes:

[0408] i) a discoverer user information parameter set to the application layer ID of the discoverer UE provided by the upper layer, the corresponding MIC field calculated for the direct discovery set as described in 3GPP TS 33.503

[34] , and the corresponding UTC-based counter LSB parameter set to the four least significant bits of the UTC-based counter; and;

[0409] ii) a discoverer user information parameter set to the application layer ID of the discoverer UE provided by the upper layer, the corresponding MIC field calculated for the direct discovery set as described in 3GPP TS 33.503

[34] , and the corresponding UTC-based counter LSB parameter set to the four least significant bits of the UTC-based counter;

[0410] And apply the associated encryption bitmask (see Clause 6.2) in the security parameters of the ProSe service code sent from the DDNMF along with the UTC-based counter to the Direct Discovery Set IE as specified in 3GPP TS 33.503

[34] ;

[0411] 2) Invalid;

[0412] 3) Set the relay service code parameter to the relay service code parameter configured in Clause 5.2.7 that identifies the connection service to be requested. The security procedure selection is based on the relay service code configured at the UE.

[0413] 4) Include the MIC field calculated as described in 3GPP TS 33.503

[34] ;

[0414] 5) Set the UTC-based counter LSB parameter to the four least significant bits of the UTC-based counter;

[0415] 6) Set the ProSe direct discovery PC5 message type parameters as specified in Table 10.2.1.13;

[0416] 7) If, for example, in a previous 5G ProSe UE inter-relay discovery or 5G ProSeIf it is known during the inter-UE relay communication process, the inter-UE relay UE information parameter can be set to the user information ID of the 5G ProSe inter-UE relay UE; and

[0417] 8) If the discoverer UE needs to instruct the 5G ProSe inter-UE relay UE to prohibit broadcasting user information of the discoverer UE included in the direct discovery set during the process of 5G ProSe inter-UE relay discovery via the PC5 interface using Model A, a notification prohibition indication whose value is set to "prohibit broadcasting user information" will be included in the PC5 discovery message for the inter-UE relay discovery request;

[0418] d) Apply the DUIK, DUSK, or DUCK together with the associated encryption bitmask of the relay service code used for 5G ProSe inter-UE relay discovery and the UTC-based counter to the PROSE PC5DISCOVERY message for any security mechanism configured to be applied, such as integrity protection, message scrambling, or confidentiality protection of one or more of the above parameters, as specified in 3GPP TS 33.503

[34] ;

[0419] e) Set the destination layer 2 ID to the default destination layer 2 ID as specified in Clause 5.2.7, and assign a self-assigned source layer 2 ID for sending the UE inter-relay discovery request message; and

[0420] Note 1: The UE implementation ensures that the value of the self-assigned source layer 2 ID is different from any other self-assigned source layer 2 ID for 5G ProSe direct communication as specified in Clause 7.2, different from any other pre-configured destination layer 2 ID as specified in Clause 5.2, and different from any other self-assigned source layer 2 ID for simultaneous 5G ProSe direct discovery process via PC5 using different discovery models as specified in Clauses 6.2.14.2.1.2, 6.2.15.2.1.2, 8.2.1.2.2.2, Clause 8.2.1.2.4.2, and Clause 8a.2.1.2.2.2.

[0421] f) The obtained PROSE PC5 DISCOVERY message for inter-UE relay discovery request, together with the source layer 2 ID, destination layer 2 ID, and the indication of the message for 5G ProSe direct discovery, is passed to the lower layer for transmission via the PC5 interface.

[0422] If the PROSE PC5 DISCOVERY message for inter-UE relay discovery request is for requesting proximity of connection services provided by a 5G ProSe inter-UE relay UE, the UE should ensure that it continues to transmit the PROSE PC5 DISCOVERY message for inter-UE relay discovery request until the UE is triggered by the upper layer to stop requesting proximity of the 5G ProSe inter-UE relay UE.The discovery process continues until the UE stops being authorized to perform the discoverer-side UE procedure for inter-UE relay discovery, which is adjacent to the connection service provided by the UE. How this is achieved depends on the UE implementation scheme.

[0423] Note 2: The discoverer-side UE can stop the discoverer-side UE procedure for inter-UE relay discovery in an implementation-specific manner (e.g., the maximum number of implementation-specific 5G ProSe direct links configured in the UE, or the implementation-specific timer expiring) to save power.

[0424] If the PROSE PC5 DISCOVERY message for inter-UE relay discovery request is used to trigger a PROSE PC5 DISCOVERY message signal strength measurement between the UE and a 5G ProSe inter-UE relay UE with which the UE has established a link, the UE will start a retransmission timer T5110. If the retransmission timer T5110 expires, the UE will retransmit the PROSE PC5 DISCOVERY message for inter-UE relay discovery request and restart timer T5110. If no response is received from a 5G ProSe inter-UE relay UE with which the UE has established a link after the maximum allowed retransmission count is reached, the UE will trigger an inter-UE relay reselection process.

[0425] Note 3: The maximum allowed retransmission count is specific to the UE implementation scheme.

[0426] Upon receiving a PROSE PC5 DISCOVERY message in response to an inter-UE relay discovery, for the target relay service code of the connection service authorized for discovery by the UE, the UE will obtain a valid UTC time from the lower layer and generate a UTC-based counter corresponding to this UTC time, and use the counter to restore the UTC-based counter associated with the PROSE PC5 DISCOVERY message and the UTC-based counter associated with the direct discovery set. If an associated DUSK (if using a security procedure on the user plane for 5G ProSe UE-to-UE relay) and a UTC-based counter associated with the PROSE PC5 DISCOVERY message are received from 5G DDNMF or 5G PKMF, the UE will use the associated DUSK to descramble the PROSE PC5 DISCOVERY message, as described in 3GPP TS 33.503

[34] . Then, if a DUCK (if using a security procedure on the user plane for 5G ProSe UE-to-UE relay) is received from 5G DDNMF or 5G PKMF, the UE will use the DUCK and the UTC-based counter associated with the PROSE PC5 DISCOVERY message to decrypt the configured message-specific confidentiality protection portion, as described in 3GPP TS 33.503

[34] . Finally, if a DUIK (if using a security procedure on the user plane for 5G ProSe UE-to-UE relay) is received from 5G DDNMF or 5G PKMF, the UE will use the DUCK and the UTC-based counter associated with the PROSE PC5 DISCOVERY message to decrypt the configured message-specific confidentiality protection portion, as described in 3GPP TS 33.503

[34] .If the UE uses the DUIK and a UTC-based counter associated with the PROSE PC5 DISCOVERY message to verify the MIC field in the unscrambled PROSE PC5 DISCOVERY message in response to the UE inter-relay discovery, the UE will then use the DUIK and a UTC-based counter associated with the PROSE PC5 DISCOVERY message.

[0427] The UE will further use the DUSK (see Clause 6.2.7) in the code reception security parameters for the ProSe service authorized for UE discovery and a UTC-based counter associated with the direct discovery set to descramble the direct discovery set IE in the PROSE PC5 DISCOVERY message, as described in 3GPP TS 33.503

[34] . Then, if the code reception security parameters contain the DUIK, the UE will use the DUCK and a UTC-based counter associated with the direct discovery set to decrypt the direct discovery set IE, as described in 3GPP TS 33.503

[34] . The UE will verify whether the application layer ID of the discoverer UE in the decrypted direct discovery set matches the application layer ID of the target discoverer UE provided by the upper layer; if they do not match, the UE will discard the direct discovery set. Finally, if the application layer ID matches and the code reception security parameters contain the DUIK (page 27 / 68 of the specification, 30 CN 121218295 A), the UE will use the DUIK and the UTC-based counter associated with the direct discovery set to verify the MIC of the direct discovery set IE in the PROSE PC5 DISCOVERY message for the inter-UE relay discovery response.

[0428] Note 4: The UE can determine whether the received PROSE PC5 DISCOVERY message for the inter-UE relay discovery response is for 5G ProSe direct discovery based on the indication from the lower layer.

[0429] Then, if:

[0430] a) the relay service code parameters of the PROSE PC5 DISCOVERY message in response to the inter-UE relay discovery are the same as the relay service code parameters of the PROSE PC5 DISCOVERY message in response to the inter-UE relay discovery request; and

[0431] b) the application layer ID of the discoverer UE received in the PROSE PC5 DISCOVERY message in response to the inter-UE relay discovery is the same as the application layer ID of the target discoverer UE provided by the upper layer for the requested connection service,

[0432] then the UE will consider that the connection service sought by the UE has been discovered. Additionally, the UE can measure the signal strength of the PROSE PC5 DISCOVERY message in response to the inter-UE relay discovery for relay selection or reselection. If the UE has already established a link with a 5G ProSe...When the inter-UE relay UE receives a PROSE PC5 DISCOVERY message in response to the inter-UE relay discovery, the UE will stop the retransmission timer T5110 and start the periodic measurement timer T5111.

[0433] 8a.2.1.3.2.3 Discoverer UE procedure for inter-UE relay discovery

[0434] When the UE is triggered by the upper layer to stop requesting proximity of the connection service provided by the 5G ProSe inter-UE relay UE, or when the UE stops being authorized to perform the discoverer UE procedure for inter-UE relay discovery, the UE will instruct the lower layer to stop the discoverer operation.

[0435] Note: The discoverer UE can stop the discoverer UE procedure for inter-UE relay discovery in an implementation-specific manner (e.g., the implementation-specific maximum number of 5G ProSe direct links configured in the UE, or the implementation-specific timer expiration) to save power.

[0436] When the UE stops the discoverer operation, if the UE is in 5GMM-CONNECTED mode, the UE will trigger the corresponding procedure in the lower layer as specified in 3GPP TS 38.331

[13] .

[0437] 8a.2.1.3.3 Relay UE procedure for inter-UE relay discovery

[0438] 8a.2.1.3.3.1 General

[0439] The purpose of the inter-UE relay discovery relay UE procedure is to enable a ProSe-enabled UE with inter-UE relay to respond to requests from other ProSe-enabled UEs for proximity of connection services provided by the 5G ProSe inter-UE relay UE when requested from the upper layer.

[0440] 8a.2.1.3.3.2 Relay UE Procedure Initiated by Inter-UE Relay Discovery

[0441] A UE is authorized to perform the relay UE procedure for inter-UE relay discovery if the following conditions exist:

[0442] a) The UE is authorized to act as a 5G ProSe inter-UE relay UE in the PLMN indicated by the serving cell, and

[0443] 1) The UE is served by NG-RAN; or

[0444] 2) The UE is not served by NG-RAN and intends to use the pre-configured radio resources for 5G ProSe inter-UE relay discovery;

[0445] b) The UE is configured with:

[0446] 1) Relay service code parameters as specified in Clause 5.2.7 to identify the connection service to be responded to, and the UE supports the security procedure of the indicated relay service code; and

[0447] 2) User information ID for 5G ProSe inter-UE relay discovery, as specified in Clause 5.2.7. Otherwise, the UE is not authorized to perform the relay UE discovery procedure for inter-UE relays. Specification 28 / 68 pages 31 CN 121218295 A

[0448] Figure 8a.2.1.3.3.2.1 illustrates the interaction between the 5G ProSe inter-UE relay UE and the discoverer UE during the inter-UE relay discovery process.

[0449] Figure 14 is a reproduction of Figure 8a.2.1.3.3.2.1 of 3GPP TS 24.554 v18.4.0: the relay UE process of inter-UE relay discovery with the discoverer UE.

[0450] When the UE is triggered by the upper layer to begin responding to a request for proximity of connection services provided by the inter-UE relay, and if the UE is authorized to perform the relay UE discovery procedure of the inter-UE relay, then the UE:

[0451] a) if the UE is served by NG-RAN and is in 5GMM-IDLE mode and needs to request the resources specified in 3GPP TS 38.331

[13] for sending the PROSE PC5 DISCOVERY message, then the UE will perform the service request procedure specified in 3GPP TS 24.501

[11] ; and

[0452] b) will instruct the lower layer to begin listening for the PROSE PC5 DISCOVERY message.

[0453] Upon receiving a PROSE PC5 DISCOVERY message for an inter-UE relay discovery request, for the relay service code of the connection service authorized for the UE's response, if an associated DUSK is received from 5G DDNMF or 5GPKMF (if using a security procedure on the user plane for 5G ProSe inter-UE relay), the UE will use the associated DUSK and a UTC-based counter obtained during the receive operation to descramble the PROSE PC5 DISCOVERY message, as described in 3GPP TS 33.503

[34] . Then, if a DUCK is received from 5G DDNMF or 5G PKMF (if using a security procedure on the user plane for 5G ProSe inter-UE relay), the UE will use the DUCK and a UTC-based counter to decrypt the configured message-specific confidentiality protection portion, as described in 3GPP TS 33.503

[34] . Finally, if a DUIK is received from 5G DDNMF or 5G PKMF (if a security procedure on the user plane for 5G ProSe inter-UE relay is used), the UE will use the DUIK and a UTC-based counter to verify the MIC field in the unscrambled PROSE PC5 DISCOVERY message for the inter-UE relay discovery request.

[0454] Note 1: The UE can determine that the received PROSE PC5 DISCOVERY message for the 5G ProSe inter-UE relay discovery request is for 5G ProSe direct discovery based on indications from the lower layer.

[0455] If the UE receives a PROSE PC5 message for the inter-UE relay discovery request...If the UE is not served by NG-RAN, and the message contains a relay service code associated with a network-assisted security instruction indicating the use of a network-assisted security procedure, the UE will ignore the PROSE PC5 DISCOVERY message.

[0456] If:

[0457] a) The UE receives a PROSE PC5 DISCOVERY message for an inter-UE relay discovery request, and in that message:

[0458] 1) The relay service code parameters are the same as the relay service code parameters configured for connection service as specified in Clause 5.2.7; and

[0459] i) The UE is served by NG-RAN; or

[0460] ii) The UE is not served by NG-RAN, and the relay service code is associated with a network-assisted security indication indicating that a security procedure without network assistance will be used; or

[0461] 2) It does not contain inter-UE relay UE information parameters, or it contains inter-UE relay UE information parameters and the parameters are the same as the user information ID configured for inter-UE relay discovery as specified in Clause 5.2.7; or

[0462] b) The periodic measurement timer T5113 expires,

[0463] then the UE:

[0464] a) If the received PROSE PC5 message for an inter-UE relay discovery request... If the DISCOVERY message does not contain a notification prohibition indication, or if it does contain a notification prohibition indication and its value is set to "Do not prohibit broadcasting user information", then the protected user information of the discoverer UE, its validity time, and the relay service code will be stored.

[0465] b) The valid UTC time for discovery transmission will be obtained from the lower layer, and a UTC-based counter corresponding to this UTC time will be generated;

[0466] c) A PROSE PC5DISCOVERY message for the inter-UE relay discovery request will be generated for the discoverer UE. In the PROSE PC5 DISCOVERY message for inter-UE relay discovery request, the UE:

[0467] 1) sets the direct discovery set IE to the direct discovery set included in the PROSE PC5 DISCOVERY message for inter-UE relay discovery request received from the discoverer UE;

[0468] 2) sets the inter-UE relay UE information parameter to the user information ID configured for 5G ProSe inter-UE relay discovery, as specified in Clause 5.2.7;

[0469] 3) sets the relay service code parameter to the relay service code parameter of the PROSE PC5 DISCOVERY message for inter-UE relay discovery request received from the discoverer UE;

[0470] 4) Set the resource status indicator bit of the status indicator parameter to indicate whether the UE has resources available to provide connectivity services for additional ProSe-supporting UEs;

[0471] 5) Include the MIC field calculated as described in 3GPP TS 33.503

[34] ;

[0472] 6) Set the UTC-based counter LSB parameter to the four least significant bits of the UTC-based counter; and

[0473] 7) Set the ProSe direct discovery PC5 message type parameter as specified in Table 10.2.1.14;

[0474] d) Apply the DUIK, DUSK, or DUCK along with the associated encryption bitmask of the relay service code used for 5G ProSe UE-to-UE relay discovery and the UTC-based counter to the PROSE PC5DISCOVERY message for any security mechanisms configured to be applied, such as integrity protection, message scrambling, or confidentiality protection of one or more of the above parameters, as specified in 3GPP TS 33.503

[34] ;

[0475] e) Set the destination layer 2 ID to the default destination layer 2 ID as specified in Clause 5.2.7, and assign a self-assigned source layer 2 ID for sending the UE inter-relay discovery request message; and

[0476] Note 2: The UE implementation ensures that the value of the self-assigned source layer 2 ID is different from any other self-assigned source layer 2 ID for 5G ProSe direct communication as specified in Clause 7.2, different from any other pre-configured destination layer 2 ID as specified in Clause 5.2, and different from any other self-assigned source layer 2 ID for simultaneous 5G ProSe discovery process via PC5 using different discovery models as specified in Clauses 6.2.14.2.1.2, 6.2.15.2.1.2, 8.2.1.2.2.2, 8.2.1.2.4.2 and 8a.2.1.2.2.2.

[0477] Note 3: The UE implementation scheme ensures that the value of the self-assigned source layer 2 ID is also different from any other self-assigned source layer 2 ID used for simultaneous 5G ProSe UE inter-relay discovery via PC5 using Model B. The source layer 2 ID is used to associate the PROSE PC5 DISCOVERY message for the UE inter-relay discovery response with the PROSE PC5 DISCOVERY message for the UE inter-relay discovery request, so that the UE can correctly send the PROSE PC5 DISCOVERY message for the UE inter-relay discovery response to the discoverer UE that initiated the Model B PROSE PC5 DISCOVERY procedure.

[0478] f) The obtained PROSE PC5 DISCOVERY message for the UE inter-relay discovery request, together with the source layer 2 ID, destination layer 2 ID, and the message, is used for 5GThe ProSe direct discovery indication is passed to the lower layer for transmission via the PC5 interface.

[0479] For the PROSE PC5 DISCOVERY message signal strength measurement, the UE manages a periodic measurement timer T5113, which is used to trigger periodic PROSE PC5 DISCOVERY message signal strength measurement between the UE and the discoverer UE with which the UE has established a link. The timer is started whenever the UE has established a direct link with the discoverer UE, and is restarted whenever the UE receives a PROSE PC5 DISCOVERY message in response to the inter-UE relay discovery from the discoverer UE with which the UE has established a link.

[0480] If the PROSE PC5 DISCOVERY message in response to the inter-UE relay discovery request is used to trigger the PROSE PC5 DISCOVERY message signal strength measurement between the UE and the discoverer UE with which the UE has established a link, the UE will start the retransmission timer T5112. If retransmission timer T5112 expires, the UE will retransmit the PROSE PC5DISCOVERY message for the inter-UE relay discovery request and restart timer T5112. If no response is received from the discoverer UE with which the UE has established a link after the maximum allowed retransmission count is reached, the UE should trigger the 5GProSe direct link release procedure.

[0481] Note 4: The maximum allowed retransmission count is UE-specific.

[0482] The UE should instruct the lower layer to start listening for PROSE PC5 DISCOVERY messages for inter-UE relay discovery responses from the discoverer UE.

[0483] Upon receiving a PROSE PC5 DISCOVERY message in response to an inter-UE relay discovery, for the target relay service code of the connection service authorized for the UE's response, if an associated DUSK is received from 5G DDNMF or 5G PKMF (if using a security procedure on the user plane for 5G ProSe inter-UE relay), the UE will use the associated DUSK and a UTC-based counter obtained during the receive operation to descramble the PROSE PC5 DISCOVERY message, as described in 3GPP TS 33.503

[34] . Then, if a DUCK is received from 5G DDNMF or 5G PKMF (if using a security procedure on the user plane for 5G ProSe inter-UE relay), the UE will use the DUCK and a UTC-based counter to decrypt the configured message-specific confidentiality protection portion, as described in 3GPP TS 33.503

[34] . Finally, if a DUCK is received from 5G DDNMF or 5G PKMF (if using a security procedure on the user plane for 5G ProSe inter-UE relay), the UE will use the DUCK and a UTC-based counter to decrypt the configured message-specific confidentiality protection portion, as described in 3GPP TS 33.503

[34] .If the PKMF receives a DUIK (if using a security procedure on the user plane for 5G ProSe inter-UE relay), the UE will use the DUIK and a UTC-based counter to verify the MIC field in the unscrambled PROSE PC5 DISCOVERY message in response to the inter-UE relay discovery.

[0484] Note 5: The UE can determine that the received PROSE PC5 DISCOVERY message in response to the 5G ProSe inter-UE relay discovery is for 5G ProSe direct discovery based on indications from the lower layer.

[0485] The relay service code parameters of the PROSE PC5 DISCOVERY message in response to the inter-UE relay discovery are the same as those of the PROSE PC5 DISCOVERY message in response to the inter-UE relay discovery request.

[0486] Then the UE:

[0487] a) If the received PROSE PC5 DISCOVERY message for the inter-UE relay discovery response does not contain a notification prohibition indication, or if it contains a notification prohibition indication with a value set to "Do not prohibit broadcasting user information", then the protected user information of the discoverer UE, its validity time, and the relay service code will be stored.

[0488] b) The valid UTC time for discovery transmission will be obtained from the lower layer, and a UTC-based counter corresponding to this UTC time will be generated;

[0489] c) A PROSE PC5 DISCOVERY message for the inter-UE relay discovery response will be generated.

[0490] In the PROSE PC5 DISCOVERY message in response to the inter-UE relay discovery, the UE:

[0491] 1) sets the direct discovery set IE to the direct discovery set included in the PROSE PC5 DISCOVERY message in response to the inter-UE relay discovery received from the discoverer UE;

[0492] 2) sets the inter-UE relay UE information parameter to the configured user information ID for 5G ProSe inter-UE relay discovery, as specified in Clause 5.2.7;

[0493] 3) sets the relay service code parameter to the relay service code parameter of the PROSE PC5 DISCOVERY message in response to the inter-UE relay discovery received from the discoverer UE;

[0494] 4) sets the resource status indicator bit of the status indicator parameter to indicate whether the UE has resources available to provide connectivity services for 5G ProSe inter-UE relay for additional ProSe-supporting UEs; Specification 31 / 68 pages 34 CN 121218295 A

[0495] 5) Include the MIC field calculated as described in 3GPP TS 33.503

[34] ;

[0496] 6) Set the UTC-based counter LSB parameter to the four least significant bits of the UTC-based counter; and

[0497] 7) Set the ProSe direct discovery PC5 message type parameters as specified in Table 10.2.1.14;

[0498] d) Apply the DUIK, DUSK, or DUCK along with the associated encryption bitmask of the relay service code used for 5G ProSe UE inter-relay discovery and the UTC-based counter to the PROSE PC5DISCOVERY message for any security mechanisms configured to be applied, such as integrity protection, message scrambling, or confidentiality protection of one or more of the above parameters, as specified in 3GPP TS 33.503

[34] ;

[0499] e) Set the destination layer 2ID to the source layer 2ID from the discoverer UE for transmitting the PROSE PC5 DISCOVERY message for the UE inter-relay discovery request, and self-assign the source layer 2ID for sending the UE inter-relay discovery response message; and

[0500] Note 6: The UE implementation ensures that the value of the self-assigned source layer 2 ID is different from any other self-assigned source layer 2 ID for 5G ProSe direct communication as specified in Clause 7.2, and different from any other pre-configured destination layer 2 ID as specified in Clause 5.2.

[0501] f) The obtained PROSE PC5 DISCOVERY message for the inter-UE relay discovery response, together with the source layer 2 ID, the destination layer 2 ID, and the indication of the message for 5G ProSe direct discovery, is passed to the lower layer for transmission via the PC5 interface.

[0502] Note 7: If the UE is processing a PROSE DIRECT LINK ESTABLISHMENT REQUEST message with the same source Layer 2 ID as the received PROSE PC5 DISCOVERY message for inter-UE relay discovery request, then depending on the UE implementation, a conflict of destination Layer 2 ID is avoided (e.g., sending a PROSE DIRECT LINK ESTABLISHMENT REJECT message containing the PC5 signaling protocol cause value #3 "Conflict of Layer 2 ID for unicast communication detected", or ignoring the PROSE DIRECT DISCOVERY message for inter-UE relay discovery request).

[0503] Figure 8a.2.1.3.3.2.2 illustrates the interaction between the 5G ProSe inter-UE relay UE and the discoverer UE during the inter-UE relay discovery process.

[0504] Figure 15 is a reproduction of Figure 8a.2.1.3.3.2.2 of 3GPP TS 24.554 v18.4.0: the relay UE process of inter-UE relay discovery with the discoverer UE.

[0505] 8a.2.1.3.3.3 Relay UE Procedure for Inter-UE Relay Discovery Completed

[0506] When a UE is triggered by an upper layer to stop responding to requests for proximity of connection services provided by a 5G ProSe Inter-UE Relay UE, or when a UE stops being authorized to perform the Inter-UE Relay Discovery relay UE procedure, the UE will instruct the lower layer to stop listening.

[0507] Note: A 5G ProSe Inter-UE Relay UE can stop the Inter-UE Relay Discovery relay UE procedure to save power by means of an implementation-specific method (e.g., the implementation-specific maximum number of 5G ProSe direct links configured in the UE, or the implementation-specific timer expiring).

[0508] When the UE stops listening, if the UE is in 5GMM-CONNECTED mode, the UE will trigger the corresponding procedure in the lower layer as specified in 3GPP TS 38.331

[13] .

[0509] 8a.2.1.3.4 Discoverer UE Procedure for Inter-UE Relay Discovery

[0510] 8a.2.1.3.4.1 General

[0511] The purpose of the discoverer UE procedure for inter-UE relay discovery is to enable ProSe-enabled UEs to respond to requests from other ProSe-enabled UEs regarding proximity of connection services via 5G ProSe inter-UE relay UE when a request comes from an upper layer. Instruction manual 32 / 68 pages 35 CN 121218295 A

[0512] 8a.2.1.3.4.2 Discoverer UE procedure initiated by inter-UE relay discovery

[0513] The UE is authorized to perform the discoverer UE procedure for inter-UE relay discovery if the following conditions exist:

[0514] a) The UE is authorized to act as a 5G ProSe end UE in the PLMN indicated by the serving cell, and

[0515] 1) The UE is served by NG-RAN; or

[0516] 2) The UE is not served by NG-RAN and intends to use the pre-configured radio resources for 5G ProSe inter-UE relay discovery; and

[0517] b) The UE is configured with:

[0518] 1) Relay service code parameters for identifying the connection service to be responded to as specified in Clause 5.2.7, and the UE supports the security procedure of the indicated relay service code;

[0519] Otherwise, the UE is not authorized to perform the discoverer UE procedure for inter-UE relay discovery.

[0520] Figure 8a.2.1.3.4.2.1 illustrates the interaction of the discoverer UE during the inter-UE relay discovery process.

[0521] Figure 16 is a reproduction of Figure 8a.2.1.3.4.2.1: the discoverer UE process during inter-UE relay discovery in 3GPP TS 24.554 v18.4.0.

[0522] When the UE is triggered by the upper layer to begin responding regarding the 5G ProSeWhen a neighboring UE requests a connection service provided by an inter-UE relay UE, and if the UE is authorized to perform the discoverer UE procedure for inter-UE relay discovery, then the UE:

[0523] a) if the UE is served by NG-RAN and is in 5GMM-IDLE mode and needs to request the resources specified in 3GPP TS 38.331

[13] for sending a PROSE PC5 DISCOVERY message, then the UE will perform the service request procedure specified in 3GPP TS 24.501

[11] ; and

[0524] b) will instruct the lower layer to start listening for PROSE PC5 DISCOVERY messages.

[0525] Upon receiving a PROSE PC5 DISCOVERY message for an inter-UE relay discovery request, for the relay service code of the connection service authorized for the UE's response, the UE obtains a valid UTC time from the lower layer and generates a UTC-based counter corresponding to this UTC time, and uses the counter to restore the UTC-based counter associated with the PROSE PC5 DISCOVERY message and the UTC-based counter associated with the direct discovery set. If an associated DUSK (if using a security procedure on the user plane for 5G ProSe inter-UE relay) and a UTC-based counter associated with the PROSE PC5 DISCOVERY message are received from 5G DDNMF or 5G PKMF, the UE will use the associated DUSK to descramble the PROSE PC5 DISCOVERY message, as described in 3GPP TS 33.503

[34] . Then, if a DUCK is received from 5G DDNMF or 5G PKMF (if a security procedure on the user plane for 5G ProSe UE-to-UE relay is used), the UE will use the DUCK and a UTC-based counter associated with the PROSE PC5 DISCOVERY message to decrypt the configured message-specific confidentiality protection portion, as described in 3GPP TS 33.503

[34] . Finally, if a DUIK is received from 5G DDNMF or 5G PKMF (if a security procedure on the user plane for 5G ProSe UE-to-UE relay is used), the UE will use the DUIK and a UTC-based counter associated with the PROSE PC5 DISCOVERY message to verify the MIC field in the unscrambled PROSE PC5 DISCOVERY message for the UE-to-UE relay discovery request.

[0526] The UE will further use the DUSK (see Clause 6.2.6) in the code reception security parameters of the ProSe service used for UE authorized discovery and the UTC-based counter associated with the direct discovery set to descramble PROSE PC5.The Direct Discovery Set (IE) in the DISCOVERY message is as described in 3GPP TS 33.503

[34] . Then, if the Code Receive Security Parameters contain a DUIK, the UE will use the DUCK and a UTC-based counter associated with the Direct Discovery Set to decrypt the Direct Discovery Set (IE), as described in 3GPP TS 33.503

[34] . The UE will verify whether the application layer ID of the discoverer UE in the decrypted Direct Discovery Set matches the application layer ID of the UE provided by the upper layer; if they do not match, the UE will discard the Direct Discovery Set. Finally, if the application layer ID matches and the Code Receive Security Parameters contain a DUIK, the UE will use the DUIK and a UTC-based counter associated with the Direct Discovery Set to verify the MIC of the Direct Discovery Set (IE) in the PROSE PC5DISCOVERY message for the inter-UE relay discovery request.

[0527] Note 1: The UE can determine, based on the indication from the lower layer, that the received PROSE PC5 DISCOVERY message for the 5G ProSe inter-UE relay discovery request is for 5G ProSe direct discovery.

[0528] Then, if:

[0529] a) the relay service code parameters of the received PROSE PC5 DISCOVERY message for the inter-UE relay discovery request are the same as the relay service code parameters configured as specified for the connection service in Clause 5.2.7; and

[0530] b) the application layer ID of the discoverer UE in the received PROSE PC5 DISCOVERY message for the inter-UE relay discovery request is the same as the application layer ID of the UE provided by the upper layer;

[0531] then the UE:

[0532] a) obtains the valid UTC time for the discovery transmission from the lower layer and generates a UTC-based counter corresponding to this UTC time;

[0533] b) generates a PROSE PC5 DISCOVERY message for the inter-UE relay discovery response.

[0534] In the PROSE PC5 DISCOVERY message in response to the inter-UE relay discovery request, the UE:

[0535] 1) will include a direct discovery set IE, which includes:

[0536] i) a discoverer user information parameter set to the application layer ID of the UE provided by the upper layer (which is the same as the application layer ID of the discoverer UE received in the PROSE PC5 DISCOVERY message in response to the inter-UE relay discovery request), a corresponding MIC field for the discoverer user information calculated as described in 3GPP TS 33.503

[34] , and a corresponding UTC-based counter LSB parameter set to the four least significant bits of the UTC-based counter; and;

[0537] ii) The discoverer user information parameter of the discoverer UE's application layer ID received in the PROSE PC5 DISCOVERY message for inter-UE relay discovery request from the 5G ProSe inter-UE relay UE, the corresponding MIC field for the discoverer user information calculated as described in 3GPP TS 33.503

[34] , and the corresponding UTC-based counter LSB parameter of the four least significant bits of the UTC-based counter are set;

[0538] and the DUIK, DUSK or DUCK is applied together with the associated encryption bitmask (see Clause 6.2) in the code transmission security parameter of the ProSe service received from DDNMF and the UTC-based counter to each user information as specified in 3GPP TS 33.503

[34] ;

[0539] 2) Invalid;

[0540] 3) The relay service code parameter is set to the relay service code parameter of the PROSE PC5 DISCOVERY message for inter-UE relay discovery request;

[0541] 4) Include the MIC field calculated as described in 3GPP TS 33.503

[34] ;

[0542] 5) Set the UTC-based counter LSB parameter to the four least significant bits of the UTC-based counter; and

[0543] 6) Set the ProSe direct discovery PC5 message type parameter as specified in Table 10.2.1.14; and

[0544] 7) If the discoverer UE needs to instruct the 5G ProSe UE inter-relay UE to prohibit broadcasting user information of the discoverer UE included in the direct discovery set during the process of 5G ProSe UE inter-relay discovery via the PC5 interface using Model A, a notification prohibition indication whose value is set to "prohibit broadcasting user information" will be included in the PC5 discovery message for the UE inter-relay discovery response;

[0545] c) Apply the DUIK, DUSK, or DUCK together with the associated encryption bitmask of the relay service code used for 5G ProSe UE inter-relay discovery and the UTC-based counter to PROSE. The PC5DISCOVERY message is configured for use with any security mechanism of the application, such as integrity protection, message scrambling, or confidentiality protection of one or more of the above parameters, as specified in specification 34 / 68, page 37, CN 121218295 A, 3GPP TS 33.503

[34] ;

[0546] d) Set the destination layer 2ID to the source layer 2ID of the 5G ProSe inter-UE relay UE for transmitting the PROSE PC5 DISCOVERY message in response to the inter-UE relay discovery request, and self-assign the source layer 2ID for sending the inter-UE relay discovery response message; and

[0547] Note 2: The UE implementation ensures that the value of the self-assigned source layer 2 ID is different from any other self-assigned source layer 2 ID for 5G ProSe direct communication as specified in Clause 7.2, and different from any other pre-configured destination layer 2 ID as specified in Clause 5.2.

[0548] e) The obtained PROSE PC5 DISCOVERY message for the inter-UE relay discovery response, together with the source layer 2 ID, the destination layer 2 ID, and the indication of the message for 5G ProSe direct discovery, is passed to the lower layer for transmission via the PC5 interface.

[0549] 8a.2.1.3.4.3 Discoverer-side UE procedure for inter-UE relay discovery completion

[0550] When the UE is triggered by the upper layer to stop responding to requests for proximity of connection services via the 5G ProSe inter-UE relay UE, or when the UE stops being authorized to perform the discoverer-side UE procedure for inter-UE relay discovery, the UE will instruct the lower layer to stop listening.

[0551] When the UE stops listening, if the UE is in 5GMM-CONNECTED mode, the UE will trigger the corresponding procedure in the lower layer as specified in 3GPP TS 38.331

[13] .

[0552] …

[0553] 8a.2.3 5G ProSe UE Inter-Relay Reselection Procedure

[0554] 8a.2.3.1 General

[0555] The purpose of the 5G ProSe UE Inter-Relay Reselection Procedure is to enable the 5G ProSe end UE to reselect the 5G ProSe UE Inter-Relay UE so as to obtain the connection service of another 5G ProSe end UE when the service 5G ProSe UE Inter-Relay UE is no longer suitable.

[0556] 8a.2.3.2 Initiation of Inter-UE Relay Reselection Procedure

[0557] The 5G ProSe UE shall trigger the inter-UE relay reselection procedure if one of the following conditions is met:

[0558] a) The UE has received from the lower layer an indication that the serving 5G ProSe inter-UE relay UE no longer meets the lower layer standard specified in 3GPP TS 38.300

[21] ;

[0559] b) The parameters related to 5G ProSe inter-UE relay in the configuration parameters (e.g., relay service code, etc.) of 5G ProSe inter-UE relay as specified in Clause 5.2.7 have been updated, and the serving 5G ProSe inter-UE relay UE no longer meets the conditions specified in Clause 8a.2.2.2;

[0560] c) The UE has received from the 5G ProSe inter-UE relay UE a PROSE DIRECT LINK ESTABLISHMENT REJECT message with PC5 signaling protocol reason value #1 "Direct communication with the target UE is not allowed";

[0561] d) The UE has been transferred from 5G ProSeThe UE receiving the PROSE DIRECT LINK RELEASE REQUEST message with PC5 signaling protocol reason value #1 "Direct communication with the target UE is not allowed";

[0562] d) The UE has received the PROSE DIRECT LINK RELEASE REQUEST message with PC5 signaling protocol reason value #4 "Direct connection is no longer available" from the 5G ProSe UE inter-relay UE;

[0563] f) After M consecutive retransmissions of the PROSE DIRECT LINK ESTABLISHMENT REQUEST or PROSE DIRECT LINK KEEPALIVE REQUEST message, the UE has not received any response from the 5G ProSe UE inter-relay UE;

[0564] g) After M consecutive retransmissions of the PROSE PC5 DISCOVERY message for the UE inter-relay discovery request (used to trigger the PROSE PC5 DISCOVERY message signal between the UE and the 5G ProSe UE inter-relay UE with which the UE has established a link, the UE receives the PROSE PC5 DISCOVERY message signal (page 35 / 68, CN). After 121218295 A strength measurement), the UE has not received any response from the 5G ProSe UE-to-UE relay UE;

[0565] Note 1: The value of M is implementation-specific and is less than or equal to the maximum number of retransmissions allowed by the PC5 signaling protocol.

[0566] h) The UE has received a PROSE DIRECT LINK ESTABLISHMENT REJECT message with PC5 signaling protocol reason value #13 "Congestion" from the 5G ProSe inter-UE relay UE;

[0567] i) The UE has received a PROSE DIRECT LINK RELEASE REQUEST message with PC5 signaling protocol reason value #13 "Congestion" from the 5G ProSe inter-UE relay UE;

[0568] j) The UE has received a PROSE DIRECT LINK ESTABLISHMENT REJECT message with PC5 signaling protocol reason value #22 "5G ProSe inter-UE relay security procedure failed" from the 5G ProSe inter-UE relay UE;

[0569] In cases c), d), h), i), and j), the 5G ProSe end UE will exclude the 5G ProSe UE that sent the message specified in case c), d), h), i), or j) from the inter-UE relay reselection process described below. Inter-UE relay UE (if provided from ProSe inter-UE relay UE in cases h) and i), at least for the indicated backoff period.

[0570] In order to perform the inter-UE relay reselection process, the UE will first initiate one or both of the following procedures:

[0571] a) a listening UE relay discovery as specified in Clause 8a.2.1.2.3; or

[0572] b) a discoverer-side UE procedure as specified in Clause 8a.2.1.3.2.

[0573] After performing the above discovery procedures, the 5G ProSe end UE may, based on the UE implementation scheme, perform a 5G ProSe direct link modification procedure for agreed 5G ProSe inter-UE relay reselection, or may perform a 5G ProSe direct link establishment procedure with the selected 5G ProSe inter-UE relay UE.

[0574] 8a.2.3.3 Candidate 5G ProSe UE Inter-Relay Discovery Procedure

[0575] The purpose of the candidate 5G ProSe UE Inter-Relay Discovery Procedure is to support the target 5G ProSe UE in discovering candidate 5G ProSe UE Inter-Relay UEs when the target 5G ProSe UE needs to discover candidate 5G ProSe UE Inter-Relay UEs for negotiating 5G ProSe layer 3 UE inter-relay reselection, as specified in Clause 6.7.4 of 3GPP TS 23.304[2]. This process is based on the UE inter-relay discovery process using Model B via the PC5 interface, as specified in Clause 8a.2.1.3, with the following modifications:

[0576] a) When the target 5G ProSe end UE, acting as the discoverer UE, generates a PROSE PC5 DISCOVERY message for the UE inter-relay discovery request, in the PROSE PC5 DISCOVERY message for the UE inter-relay discovery request, the UE will:

[0577] 1) Set the relay service code parameter to the relay service code parameter currently used with the serving 5G UE inter-relay UE that requires UE inter-relay reselection;

[0578] 2) Set the UE inter-relay UE information parameter to the user information ID of the candidate 5G ProSe UE inter-relay UE; and

[0579] 3) Not include the direct discovery set parameter,

[0580] and set the destination layer 2 ID to the PROSE DIRECT LINK MODIFICATION during the agreed 5G ProSe layer 3 UE inter-relay reselection process. The destination layer 2 ID of the candidate 5G ProSe inter-UE relay UE received in the REQUEST message. If the layer 2 ID of the candidate 5G ProSe inter-UE relay UE is not received in the PROSE DIRECT LINK MODIFICATION REQUEST message during the agreed 5G ProSe layer 3 inter-UE relay reselection process, the UE sets the destination layer 2 ID to the default layer 2 ID used for discovery, as specified in clause 5.2.7;

[0581] b) When the 5G ProSe inter-UE relay UE receives a PROSE PC5 DISCOVERY message for inter-UE relay discovery request, the 5G ProSe inter-UE relay will not perform the relay UE discovery process if the following conditions exist:

[0582] 1) The PROSE PC5 DISCOVERY message for inter-UE relay discovery request does not contain direct discovery set parameters; and the specification page 36 / 68 39 CN 121218295 A

[0583] 2) The inter-UE relay UE information parameters in the PROSE PC5 DISCOVERY message for inter-UE relay discovery request match the user information ID used by the 5G ProSe inter-UE relay UE;

[0584] c) After b), the 5G ProSe inter-UE relay UE will send a PROSE PC5 DISCOVERY message for inter-UE relay discovery response to the discoverer UE. In the PROSE PC5 DISCOVERY message responding to the inter-UE relay discovery, the UE will:

[0585] 1) set the relay service code parameter to the relay service code parameter of the PROSE PC5 DISCOVERY message for the inter-UE relay discovery request received from the target 5G ProSe UE; and

[0586] 2) not include the direct discovery set parameter; and

[0587] d) after c), when the target 5G ProSe UE receives the PROSE PC5 DISCOVERY message responding to the inter-UE relay discovery, and if

[0588] 1) the relay service code parameter of the PROSE PC5 DISCOVERY message responding to the inter-UE relay discovery is the same as the relay service code parameter of the PROSE PC5 DISCOVERY message for the inter-UE relay discovery request;

[0589] b) not include the direct discovery set parameter of the PROSE PC5 DISCOVERY message responding to the inter-UE relay discovery; and

[0590] c) If the UE information parameters of the PROSE PC5 DISCOVERY message in response to the UE inter-relay discovery are the same as the user information ID of the candidate 5G ProSe UE inter-relay UE in the PROSE PC5 DISCOVERY message in response to the UE inter-relay discovery request,

[0591] then the 5G ProSe UE will consider discovering the candidate 5G ProSe UE inter-relay UE and perform the 5G ProSe direct link modification process for UE inter-relay UE reselection.

[0592] …

[0593] 10.2.1 Message Definition

[0594] This message is sent by the UE through the PC5 interface and is used to open 5GProSe direct discovery and restricted 5G ProSe direct discovery. See Tables 10.2.1.1, 10.2.1.2, 10.2.1.3, 10.2.1.4, 10.2.1.5, 10.2.1.6, 10.2.1.7, 10.2.1.8, 10.2.1.9, 10.2.1.10, 10.2.1.11, 10.2.1.12, 10.2.1.13, and 10.2.1.14.

[0595] Message type: PROSE PC5 DISCOVERY

[0596] Meaning: Dual

[0597] Direction: UE to peer UE

[0598] …

[0599] Table 10.2.1.13: PROSE PC5 DISCOVERY message description for UE inter-relay discovery request 37 / 68 pages 40 CN 121218295 A

[0600]

[0601] Table 10.2.1.14: PROSE PC5 DISCOVERY message description for UE inter-relay discovery response 38 / 68 pages 41 CN 121218295 A

[0602]

[0603] …

[0604] 11.2.1 ProSe direct discovery PC5 message type

[0605] This parameter is used to indicate the type of ProSe direct discovery message on the PC5 interface.

[0606] The encoding method of this parameter is shown in Figure 11.2.1.1 and Table 11.2.1.1.

[0607] The ProSe Direct Discovery PC5 message type is a type 1 information element with a length of 1 octet.

[0608] Figure 17 is a reproduction of Figure 11.2.1.1 of 3GPP TS 24.554 v18.4.0: ProSe Direct Discovery PC5 message type parameter.

[0609] Table 11.2.1.1: ProSe Direct Discovery PC5 message type parameter specification 39 / 68 pages 42 CN 121218295 A

[0610] Specification 40 / 68 pages 43 CN 121218295 A

[0611]

[0612] Note 1: Content type '0000' (announcement / response) is used for Model A announcements and Model B discoverer operations.

[0613] Note 2: Content type '0100' (UE to Network Relay Discovery Announcement or UE to Network Relay Discovery Response) is used for Model A announcements and Model B discoverer operations.

[0614] Note 3: Content type '0110' (Group Membership Discovery Announcement or Group Membership Discovery Response) is used for Model A announcements and Model B discoverer operations.

[0615] Note 4: Content type '1001' (ranging and sidelink positioning UE discovery announcement / ranging and sidelink positioning UE discovery response) is used for Model A announcement and Model B discoverer operation.

[0616] Note 5: Content type '1011' (group member discovery announcement for ranging and sidelink positioning / group member discovery response for ranging and sidelink positioning) is used for Model A announcement and Model B discoverer operation.

[0617] …

[0618] 11.2.15 Application Layer ID

[0619] The purpose of the Application Layer ID parameter information element is to carry the Application Layer ID, as specified in 3GPP TS 23.304[2].

[0620] The Application Layer ID information element is encoded as shown in Figure 11.2.15.1 and Table 11.2.15.1.

[0621] The Application Layer ID is a Type 4 information element.

[0622] Figure 18 is a reproduction of Figure 11.2.15.1 of 3GPP TS 24.554 v18.4.0: Application Layer ID Information Elements.

[0623] Table 11.2.15.1: Application Layer ID Information Elements

[0624]

[0625] …

[0626] 11.2.17 Direct Discovery Set

[0627] The purpose of the Direct Discovery Set Information Elements is to carry the Direct Discovery Set, as specified in 3GPP TS 33.503

[34] . Specification 41 / 68 pages 44 CN 121218295 A

[0628] The Direct Discovery Set Information Elements are Type 6 information elements with a minimum length of 12 octets and a maximum length of 520 octets.

[0629] The Direct Discovery Set Information Elements are encoded as shown in Figure 11.2.17.1 and Table 11.2.17.1.

[0630] Figure 19 is a reproduction of Figure 11.2.17.1 of 3GPP TS 24.554 v18.4.0: Direct Discovery Set Information Elements.

[0631] Figure 20 is a reproduction of Figure 11.2.17.2 of 3GPP TS 24.554 v18.4.0: List of Protected User Information IDs.

[0632] Figure 21 is a reproduction of Figure 11.2.17.3 of 3GPP TS 24.554 v18.4.0: Protected User Information.

[0633] Table 11.2.17.1: Direct Discovery Set Information Elements

[0634]

[0635] ====================== End of Reference ======== =============

[0636] User Equipment (UE) Inter-User Equipment (U2U) relay is specified in version 18. If the end UE cannot communicate directly with the peer UE, the relay UE can be used to support connectivity between the end UE and the peer UE. In order to find the peer end UE, the end UE can first sendThe U2U relay discovery process is initiated. According to [1][TS23.304] 3GPP TS23.304 v18.5.1, two discovery models are supported for U2U relay discovery, namely Model A and Model B. For Model A, the PROSE PC5 DISCOVERY message for inter-UE relay discovery announcement is used. The 5G Proximity Service (ProSe) inter-UE relay announcement contains a direct discovery set of user information of other end UEs near the relay UE, and the 5G ProSe end UE listens for the announcement message and saves the user information of the UEs near the relay UE. For Model B, the discoverer 5G ProSe inter-UE end UE sends a PROSE PC5 DISCOVERY message for inter-UE relay discovery request with a direct discovery set, which contains the discoverer 5G ProSe end UE and the user information of the discovered 5G ProSe end UE. In response to receiving a PROSE PC5 DISCOVERY message for an inter-UE relay discovery request from the discoverer 5G ProSe inter-UE relay, the 5G ProSe inter-UE relay can then send another PROSE PC5 DISCOVERY message for the inter-UE relay discovery request. In response to receiving a PROSE PC5 DISCOVERY message for an inter-UE relay discovery request from the 5G ProSe inter-UE relay, the discoverer 5G ProSe UE can send a PROSE PC5 DISCOVERY message for the inter-UE relay discovery response back to the 5G ProSe inter-UE. Then, the 5G ProSe inter-UE can send another PROSE PC5 DISCOVERY message for the inter-UE relay discovery response back to the discoverer 5G ProSe UE. (See page 42 / 68 of the specification, CN 121218295 A).

[0637] After performing U2U relay discovery, the first end UE (i.e., the source (5G ProSe UE-to-UE) end UE) can then trigger a Layer 2 link establishment procedure (e.g., as described in Clause 6.7.1.1 or Clause 6.7.2 of [1][TS23.304]) to support U2U relay communication between the first end UE and the second end UE (i.e., the target (5G ProSe UE-to-UE) end UE) via the relay UE. When the relay UE becomes unsuitable (e.g., the measured signal strength of the PC5 unicast link with the relay UE), the first end UE can trigger an agreed relay reselection procedure to determine another suitable relay UE for maintaining the connection service with the target end UE. The first end UE can first discover / find other nearby relay UEs, determine candidate relay UEs, and then, via the current relay UE, forward the connection to the second end UE.The second-end UE sends a link modification request message to indicate the candidate relay UE list. It should be noted that the candidate relay UE list may indicate only one candidate relay UE.

[0638] After receiving the candidate relay UE list, the second-end UE may initiate candidate U2U relay discovery to find which candidate relay UE listed in the candidate relay UE list is adjacent to the second-end UE. As specified in [1][TS23.304], candidate U2U relay discovery reuses the U2U relay discovery process using Model B, with some modifications. That is, the second-end UE may send a 5G ProSe UE inter-relay discovery request message to one of the candidate relay UEs listed in the candidate relay UE list. It should be noted that in this case, the 5G ProSe Inter-UE Relay Discovery Request message does not contain a direct discovery set, and therefore the candidate relay UE can know that this 5G ProSe Inter-UE Relay Discovery Request message is for candidate U2U relay discovery (as described in Clause 6.3.2.4.4 in [1][TS23.304]) rather than general U2U relay discovery (as described in Clause 6.3.2.4.3 in [1][TS23.304]). If the candidate relay UE matches the Inter-UE Relay Discovery set (the value of this candidate relay UE, such as the user information ID, is indicated in the Inter-UE Relay Discovery set), then the candidate relay UE can then respond to the second UE with a 5G ProSe Inter-UE Relay Discovery Response message. The 5G ProSe Inter-UE Relay Discovery Response message also does not contain a direct discovery set. Clause 8a.2.3.3 of [2][TS24.554] further specifies that a PROSE PC5 DISCOVERY message for an inter-UE relay discovery request and a PROSE PC5 DISCOVERY message for an inter-UE relay discovery response are sent without including the direct discovery set parameter. However, in section 10.2.1 of [2][TS24.554], the presence of a direct discovery set information element (IE) is mandatory in both the PROSE PC5 DISCOVERY message for an inter-UE relay discovery request and the PROSE PC5 DISCOVERY message for an inter-UE relay discovery response. The mandatory presence of the IE in the message means that the receiving side expects to decode the IE when processing the message, and therefore the transmitting side must include the IE in the message. If the second-end UE follows this concept, the second-end UE can still include the direct discovery set IE in the PROSE PC5 DISCOVERY message for an inter-UE relay discovery request (in response to receiving a list of candidate relay UEs from the first-end UE). According to Clause 8a.2.3.3 of [2][TS24.554], 5G ProSe UE-to-UE relay will not perform UE-to-UE relay if the following conditions exist.The relay UE discovery process is as follows: 1) The PROSE PC5 DISCOVERY message for the inter-UE relay discovery request does not contain the direct discovery set parameter, and 2) the inter-UE relay UE information parameter in the PROSE PC5 DISCOVERY message for the inter-UE relay discovery request matches the user information ID used for 5G ProSe inter-UE relay UE. Therefore, if the second-end UE still contains the direct discovery set IE in the PROSE PC5 DISCOVERY message for the inter-UE relay discovery request (because condition 1 is not met), then each candidate relay UE can perform the inter-UE relay discovery relay UE procedure and then respond to the second-end UE with the PROSE PC5 DISCOVERY message for the inter-UE relay discovery response message. On the other hand, according to clause 8a.2.3.3 of [2] [TS24.554], if at least the direct discovery set parameter of the PROSE PC5DISCOVERY message for the inter-UE relay discovery response message is not included, the 5G ProSe end UE will consider discovering candidate 5G ProSe inter-UE relay UEs and continue the 5G ProSe direct link modification process for inter-UE relay UE reselection. Therefore, if each candidate relay UE follows the above concept to include the direct discovery set in the PROSE PC5 DISCOVERY message for the inter-UE relay discovery response message, and the second end UE receives the PROSE PC5 DISCOVERY message for the inter-UE relay discovery response message from this candidate relay UE, then the second end UE will not consider discovering any candidate relay UEs. For this reason, the second end UE can respond to the first end UE with a link modification rejection message, and thus agree that the relay reselection will fail, and then the U2U relay communication will be interrupted. To address this issue, several potential solutions can be considered.

[0639] A new type of ProSe direct discovery PC5 message that does not contain a direct discovery set IE (or whose existence is optional) can be considered. The new type of ProSe direct discovery PC5 message may be or may contain a new PROSE PC5 DISCOVERY message for inter-UE candidate relay discovery request messages. The new type of ProSe direct discovery PC5 message may be or may contain a new PROSE PC5 DISCOVERY message for inter-UE candidate relay discovery response messages.

[0640] For example, the difference between the new PROSE PC5 DISCOVERY message for inter-UE candidate relay discovery request messages and the old PROSE PC5 DISCOVERY message for inter-UE candidate relay discovery request messages may be: for inter-UE candidate relay discovery request messages, the new PROSE PC5 DISCOVERY message for inter-UE candidate relay discovery request messages may be:The new PROSE PC5DISCOVERY message for the inter-UE candidate relay discovery request message may not contain the direct discovery set IE (or the presence of the direct discovery set IE is optional). The remainder of the new PROSE PC5DISCOVERY message for the inter-UE candidate relay discovery request message may be the same as the old PROSE PC5 DISCOVERY message for the inter-UE candidate relay discovery request message.

[0641] For example, the difference between the new PROSE PC5 DISCOVERY message for the inter-UE candidate relay discovery response message and the old PROSE PC5 DISCOVERY message for the inter-UE candidate relay discovery response message may be: the new PROSE PC5DISCOVERY message for the inter-UE candidate relay discovery response message may not contain the direct discovery set IE (or the presence of the direct discovery set IE is optional). The remainder of the new PROSE PC5DISCOVERY message for the inter-UE candidate relay discovery response message may be the same as the old PROSE PC5 DISCOVERY message for the inter-UE candidate relay discovery response message.

[0642] Because the transmission and reception of the new type of ProSe direct discovery PC5 message may have backward compatibility issues, the first-end UE may (only) include candidate relay UEs that support the new type of ProSe direct discovery PC5 message in the candidate relay UE list (in the link modification request message). The first-end UE may not include candidate relay UEs that support the new type of ProSe direct discovery PC5 message in the candidate relay UE list (in the link modification request message). Candidate relay UEs may indicate whether they support the transmission and reception of the new type of ProSe direct discovery PC5 message. Whether a candidate relay UE supports the transmission and reception of the new type of ProSe direct discovery PC5 message can be indicated by the PROSE PC5 DISCOVERY message for inter-UE relay discovery announcement (e.g., adding a new IE, indicating supported candidate discoveries). Additionally and / or alternatively, whether a candidate relay UE supports the transmission and reception of the new type of ProSe direct discovery PC5 message can be indicated by a PROSE PC5 DISCOVERY message in response to an inter-UE relay discovery (e.g., adding a new IE, indicating supported candidate discoveries). After identifying these new relay UEs, the first UE can send a link modification request message with a list of candidate relay UEs to the second UE. The link modification request message can indicate which or all of the candidate relay UEs in the candidate relay UE list support the transmission and reception of the new type of ProSe direct discovery PC5 message.

[0643] The second-end UE can perform the candidate U2U relay discovery process. The second-end UE can transmit a new PROSE PC5 DISCOVERY message for the inter-UE candidate relay discovery request message (to a candidate relay UE in the candidate relay UE list). For example, in response to receiving a new PROSE PC5 DISCOVERY message for the inter-UE candidate relay discovery request message, a candidate relay UE (in the candidate relay UE list) can transmit a new PROSE PC5 DISCOVERY message for the inter-UE candidate relay discovery response message (to the second-end UE). An example is shown in Figure 22.

[0644] Additionally and / or alternatively, the PROSE PC5 DISCOVERY message for the inter-UE relay discovery request message may include an indication of whether the PROSE PC5 DISCOVERY message for the inter-UE relay discovery request message is used for candidate 5G ProSe inter-UE relay discovery. Additionally and / or alternatively, the indication may indicate that the PROSE PC5DISCOVERY message for the inter-UE relay discovery request message (page 44 / 68, CN 121218295 A) is for candidate 5G ProSe inter-UE relay discovery. The indication may be a new IE (named, for example, a candidate discovery indication IE), and the presence of the new IE is optional. Based on the indication (set to a specific value or its presence), the candidate relay UE can determine (received from the second-end UE) that the PROSE PC5 DISCOVERY message for the inter-UE relay discovery request message is for candidate U2U relay discovery. Therefore, the candidate relay UE may not perform the relay UE procedure for inter-UE relay discovery. The candidate relay UE may ignore the direct discovery set IE included in the PROSE PC5 DISCOVERY message for the inter-UE relay discovery request message.

[0645] Additionally and / or alternatively, the PROSE PC5DISCOVERY message for the inter-UE relay discovery response message may include an indication of whether the PROSE PC5DISCOVERY message for the inter-UE relay discovery response message is used for candidate 5G ProSe inter-UE relay discovery. Additionally and / or alternatively, the indication may indicate that the PROSE PC5DISCOVERY message for the inter-UE relay discovery response message is used for candidate 5G ProSe inter-UE relay discovery. Based on the indication (set to a specific value or present), the second-end UE can determine that the PROSE PC5 DISCOVERY message for the inter-UE relay discovery response message is used for candidate U2U relay discovery. Therefore, the second-end UE may consider that a candidate relay UE has been discovered (sending the PROSE PC5DISCOVERY message for the inter-UE relay discovery response message).PC5DISCOVERY message). The second-end UE may ignore the Direct Discovery Set IE contained in the PROSE PC5 DISCOVERY message for the inter-UE relay discovery response message. An example is shown in Figure 23.

[0646] Additionally and / or alternatively, the contents of the Direct Discovery Set IE in the PROSE PC5DISCOVERY message for the inter-UE relay discovery request message may indicate that the PROSE PC5 DISCOVERY message for the inter-UE relay discovery request message is for candidate 5G ProSe inter-UE relay discovery. [2] Section 11.2.17 of TS 24.554 specifies the structure of the Direct Discovery Set IE. One or more fields in the Direct Discovery Set IE set to a specific value may indicate that the PROSE PC5 DISCOVERY message for the inter-UE relay discovery request message is for candidate 5G ProSe inter-UE relay discovery.

[0647] Additionally and / or alternatively, the contents of the Direct Discovery Set IE in the PROSE PC5 DISCOVERY message for the inter-UE relay discovery response message can indicate that the PROSE PC5 DISCOVERY message for the inter-UE relay discovery response message is for candidate 5G ProSe inter-UE relay discovery. [2] Section 11.2.17 of TS 24.554 specifies the structure of the Direct Discovery Set IE. One or more fields in the Direct Discovery Set IE set to a specific value can indicate that the PROSE PC5 DISCOVERY message for the inter-UE relay discovery response message is for candidate 5G ProSe inter-UE relay discovery. An example is shown in Figure 24.

[0648] One or more fields may contain one or more of the following fields:

[0649] - Length of the direct discovery set content,

[0650] - List of protected user information,

[0651] - Protected user information,

[0652] - Length of protected user information,

[0653] - Least Significant Bit (LSB) content of the counter based on Coordinated Universal Time (UTC),

[0654] - Message Integrity Check (MIC),

[0655] - User information,

[0656] - Length of the application layer ID content, and / or

[0657] - Application layer ID content.

[0658] Specific values ​​may be or contain zero (all bits are set to zero). Specific values ​​for the length of the direct discovery set content may be less than 12 (octet) or less than 9 (octet). Specific values ​​for the length of the protected user information may be less than 9.(Octave) or less than 7 (octaves). Specification 45 / 68 pages 48 CN 121218295 A

[0659] (Candidate UE may assume) when or if the content of the Direct Discovery IE is used to indicate that the PROSE PC5 DISCOVERY message (received by the candidate UE) for the Inter-UE Relay Discovery Request message is for candidate 5G ProSe Inter-UE Relay Discovery, the length of the Direct Discovery Set IE may be fixed (e.g., 12 octaves). (Second-end UE may assume) when or if the content of the Direct Discovery IE is used to indicate that the PROSE PC5 DISCOVERY message (received by the second-end UE) for the Inter-UE Relay Discovery Response message is for candidate 5G ProSe Inter-UE Relay Discovery, the length of the Direct Discovery Set IE may be fixed (e.g., 12 octaves).

[0660] For example, there may be only one protected user information in the protected user information list. The user information field may be set to a specific one-byte length value (e.g., 0), while the UTC-based counter LSB and MIC remain the same. Once the user information field in the protected user information matches a pre-configured specific value, the candidate UE and the second-end UE can consider the discovery message as being used for candidate relay discovery. Alternatively, the length of the protected user information field can be set to 0, and the remaining protected user information field can be filled with 0. Once the length of the protected user information field in the protected user information is 0, the UE can consider the message as being used for candidate relay discovery. The UE decodes the remaining bytes according to the length of the direct discovery set content field.

[0661] For another example, the candidate relay UE and / or the second-end UE can determine whether the PROSE PC5 DISCOVERY message for the inter-UE relay discovery request / response message is used for candidate U2U relay discovery based on the length of the direct discovery set contained in the PROSE PC5 DISCOVERY message for the inter-UE relay discovery request / response message. According to [2] [TS24.554], the minimum length of the direct discovery set IE is 12 bytes. Therefore, if the length of the Direct Discovery Set IE included in the PROSE PC5 DISCOVERY message for the inter-UE relay discovery request / response message is at least 12 bytes, the candidate relay UE and / or the second-end UE can determine that the PROSE PC5 DISCOVERY message for the inter-UE relay discovery request / response message is for candidate U2U relay discovery. In this solution, a protected user information field can be included. Within the user information field of the protected user information field, the application layer ID content field can be set to...Specific value (e.g., 0). The length field of the application layer ID content can indicate one byte (i.e., the field length of the application layer ID content is one byte). Apart from the application layer ID content field set to a specific value, the second-end UE can normally set the content of the PROSE PC5 DISCOVERY message for the inter-UE relay discovery request message.

[0662] For another example, the candidate relay UE and / or the second-end UE can determine whether the PROSE PC5 DISCOVERY message for the inter-UE relay discovery request / response message is used for candidate U2U relay discovery based on the amount of user information contained in the direct discovery set. Typically, for U2U relay discovery using Model B (i.e., not candidate U2U relay discovery), the direct discovery set IE contains user information for both UEs (including, for example, user information for the discoverer UE and user information for the found UE). In the case of candidate U2U relay discovery, such a PROSE PC5 DISCOVERY message, for example, for the inter-UE relay discovery request message, is primarily used to check whether a specific candidate relay UE is nearby, rather than being used by the second-end UE to discover the first-end UE. Therefore, it is feasible to consider that if the direct discovery set contained in the PROSE PC5 DISCOVERY message for the inter-UE relay discovery request / response message contains user information of one end UE, then the candidate relay UE and / or the second end UE can determine whether this PROSE PC5 DISCOVERY message for the inter-UE relay discovery request / response message is used for candidate U2U relay discovery. More specifically, if the length field of the direct discovery set content indicates a protected user information, then the candidate relay UE and / or the second end UE can determine whether the PROSE PC5 DISCOVERY message for the inter-UE relay discovery request / response message is used for candidate U2U relay discovery. More specifically, if the field of the protected user information list indicates a protected user information, then the candidate relay UE and / or the second end UE can determine whether the PROSE PC5 DISCOVERY message for the inter-UE relay discovery request / response message is used for candidate U2U relay discovery. Using this solution, in a field of user information within a protected user information field, the field containing the layer ID content, as per specification page 46 / 68, 49 CN 121218295 A, can be set to a specific value (e.g., 0) or the user information of the end UE (e.g., the user information of the first end UE or the user information of the second end UE).

[0663] For another example, if the user information contained in the direct discovery set is set to a specific value, the candidate relay UE and / or the second end UE can determine the PROSE for the inter-UE relay discovery request / response message.The PC5 DISCOVERY message is used for candidate U2U relay discovery. More specifically, the length field of the direct discovery set content can indicate one or two protected user information (containing, for example, user information of the first-end UE and / or user information of the second-end UE). For each protected user information, the field of the application layer ID content in the user information field can be set to a specific value (e.g., 0).

[0664] Additionally and / or alternatively, candidate relay UEs can consider the PROSE PC5 DISCOVERY message for inter-UE relay discovery request messages as being suitable for candidate U2U relay discovery based on the (destination) layer-2 ID (L2ID) associated with the PROSE PC5 DISCOVERY message for inter-UE relay discovery request messages. For example, if (at least) the PROSE PC5 DISCOVERY message for an inter-UE relay discovery request is addressed to the L2ID of the candidate relay UE, then the candidate relay UE may consider that the PROSE PC5 DISCOVERY message for an inter-UE relay discovery request can be used for candidate U2U relay discovery. If (at least) the PROSE PC5 DISCOVERY message for an inter-UE relay discovery request is received using the candidate relay UE's L2ID as the destination L2ID, then the candidate relay UE can know that the PROSE PC5 DISCOVERY message for an inter-UE relay discovery request is for candidate U2U relay discovery. If (at least) the PROSE PC5 DISCOVERY message for the inter-UE relay discovery request is addressed to the candidate relay UE's L2ID or to the default L2ID, then the candidate relay UE may consider that the PROSE PC5 DISCOVERY message for the inter-UE relay discovery request may not be used for candidate U2U relay discovery, or may be used for U2U relay discovery using Model B. If (at least) the PROSE PC5 DISCOVERY message for the inter-UE relay discovery request is not received using the candidate relay UE's L2ID as the destination L2ID, or is received using the default L2ID (as the destination L2ID), then the candidate relay UE may know that the PROSE PC5 DISCOVERY message for the inter-UE relay discovery request is not used for candidate U2U relay discovery or for U2U relay discovery using Model B. More specifically, the PROSE PC5 DISCOVERY message for the UE-to-UE relay discovery request can be received by using the L2ID of the second-end UE as the source L2ID. This solution would be feasible because the discovery request / response message used in U2U relay discovery using Model B (i.e., not candidate U2U relay discovery)The information is addressed to the default L2ID, and the second-end UE can know the L2ID of the candidate relay UE indicated in the link modification request message received from the first-end UE. The candidate relay UE can ignore the direct discovery set IE included in the PROSE PC5 DISCOVERY message for the inter-UE relay discovery request message. After sending the PROSE PC5 DISCOVERY message for the inter-UE relay discovery request message addressed to the candidate relay UE's L2ID, if the corresponding PROSE PC5 DISCOVERY message for the inter-UE relay discovery response message is received from the candidate relay UE (e.g., based on the candidate relay UE's upper-layer ID or the candidate relay UE's L2ID as the source L2ID) / at this time / after this time, then the second-end UE can consider that the candidate relay UE has been discovered. The second-end UE can ignore the direct discovery set IE included in the PROSE PC5 DISCOVERY message for the inter-UE relay discovery response message. The upper-layer ID can be an application layer ID or a user information ID. An example is shown in Figure 25.

[0665] More specifically, the user information of the terminal UE may be the upper layer ID, application layer ID or upper layer ID of the terminal UE.

[0666] For example, a textual proposal that surpasses these related solutions of [2]TS 24.554 can be shown below, where changes and edits are shown with underscores and strikethroughs:

[0667] ******Change Start******

[0668] 8a.2.1.2.2 Announcement of Inter-UE Relay Discovery UE Relay Discovery Specification 47 / 68 pages 50 CN 121218295 A

[0669] 8a.2.1.2.2.1 General

[0670] The purpose of the UE announcement process for inter-UE relay discovery is to:

[0671] a) enable a ProSe-enabled UE to announce to other ProSe-enabled UEs the availability of connectivity services provided by the inter-UE relay of a ProSe-enabled UE, in accordance with a request from an upper layer as defined in 3GPP TS 23.304; or

[0672] b) enable a ProSe-enabled UE to measure the PROSE PC5 between the ProSe-enabled UE and the 5G ProSe inter-UE relay UE. DISCOVERY message signal strength for use in inter-UE relay selection / reselection.

[0673] 8a.2.1.2.2.2 UE-initiated notification procedure for inter-UE relay discovery

[0674] The authorized UE performs the notification procedure for inter-UE relay discovery if the following conditions exist:

[0675] a) The authorized UE acts as a 5G ProSe inter-UE relay UE in the PLMN indicated by the serving cell, as specified in Clause 5.2.7, and

[0676] 1) As specified in Clause 5, the UE is served by NG-RAN and the UE is authorized to perform 5G ProSe UE-to-UE relay discovery in the PLMN; or

[0677] 2) As specified in Clause 5, the UE is authorized to perform 5G ProSe UE-to-UE relay discovery when not served by NG-RAN and intends to use pre-configured radio resources for 5G ProSe UE-to-UE relay discovery; and

[0678] b) The UE is configured with:

[0679] 1) Relay service code parameters identifying the connection service to be advertised as specified in Clause 5.2.7, and the UE supports the security procedure for 5G ProSe UE-to-UE relay indicated for the relay service code according to 3GPP TS 33.503; and

[0680] 2) User information ID for 5G ProSe UE-to-UE relay discovery as specified in Clause 5.2.7;

[0681] Otherwise, the UE is not authorized to perform the UE-to-UE relay discovery notification procedure.

[0682] The protected user information of the 5G ProSe UE will be available in the notifying UE to perform the notifying UE procedure for inter-UE relay discovery. The protected user information of the 5G ProSe UE can be retrieved from previous 5G ProSe inter-UE relay discovery response messages or from previous 5G ProSe inter-UE relay communications. The notifying UE will store a list of protected user information of the 5G ProSe UE based on an validity timer derived from the bit length of the UTC-based counter LSB content of the UTC-based counter LSB IE associated with the protected user information of the 5G ProSe UE as specified in Clause 6.1.3.3 of 3GPP TS 33.503. If the validity timer associated with the protected user information of the 5G ProSe UE expires, the notifying UE will remove the protected user information of the 5G ProSe UE from the stored list of protected user information of the 5G ProSe UE.

[0683] Editor's note: Whether and how the protected user information of the 5G ProSe end UE can be retrieved via the existing direct link between the end UE and the relay UE requires further investigation.

[0684] Figure 8a.2.1.2.2.2.1 depicted in Figure 26 illustrates the interaction of the UE in the notification process of the UE in the UE inter-relay discovery.

[0685] When the UE is triggered by the upper layer to notify the availability of the connectivity service provided by the 5G ProSe UE inter-relay, if the UE is authorized to perform the notification process of the UE in the UE inter-relay discovery, then the UE:

[0686] a) If the UE is served by NG-RAN and is in 5GMM-IDLE mode, the UE needs to request resources for sending the PROSE PC5 DISCOVERY message for 3GPP TS.The 5G ProSe UE-to-UE relay discovery as specified in 38.331 will execute the service request procedure or mobility registration procedure as specified in 3GPP TS 24.501;

[0687] b) As specified in clause 11.2.5, the valid UTC time for discovery transmission will be obtained from the lower layer, and a UTC-based counter corresponding to this UTC time will be generated; Specification 48 / 68 pages 51 CN 121218295 A

[0688] c) A PROSE PC5DISCOVERY message for UE-to-UE relay discovery announcement will be generated in accordance with clause 10.2.1. In the PROSE PC5 DISCOVERY message for UE-to-UE relay discovery notification, the UE:

[0689] 1) sets the announcer information parameter to the user information ID configured for 5G ProSe UE-to-UE relay discovery, as specified in Clause 5.2.7;

[0690] 2) sets the relay service code parameter to the relay service code configured for the connection service to be announced, as specified in Clause 5.2.7. If the UE is not served by NG-RAN, the security procedure selection is based on the relay service code configured at the UE. Otherwise, the selected relay service code configured at the UE will be associated with a network-assisted security indication, indicating that a security process without network assistance will be used;

[0691] 3) Set the direct discovery set parameter to the list of protected user information of the stored 5G ProSe terminal UE, wherein the associated relay service code of the 5G ProSe terminal UE is the same as the relay service code to be announced;

[0692] Note 0: The 5G ProSe UE relay UE will only announce the protected user information of the neighboring 5G ProSe terminal UE when the PC5 signal strength of the neighboring UE measured by the 5G ProSe UE relay is higher than the configured signal strength threshold specified in 3GPP TS 38.331.

[0693] 4) Include the MIC field calculated as described in 3GPP TS 33.503;

[0694] 5) Set the UTC-based counter LSB parameter to the four least significant bits of the UTC-based counter;

[0695] 6) Set the resource status indicator bit of the status indicator parameter to indicate whether the UE has resources available to provide connectivity services for 5G ProSe UE-to-UE relay for additional ProSe-supported UEs; and

[0696] 7) Set the ProSe direct discovery PC5 message type parameter as specified in Table 10.2.1.12;

[0697] 8) Set the candidate discovery support indicator as specified in Table 10.2.1.12.

[0698] d) Associate the DUIK, DUSK, or DUCK with the relay service code used for 5G ProSe UE-to-UE relay discovery.The encryption bitmask and the UTC-based counter are applied together to the PROSE PC5DISCOVERY message for use with any security mechanisms configured for the application, such as integrity protection, message scrambling, or confidentiality protection of one or more of the above parameters, as specified in 3GPP TS 33.503;

[0699] e) Set the destination layer 2 ID to the default destination layer 2 ID as specified in Clause 5.2.7, and self-assign a source layer 2 ID for sending 5G ProSe UE inter-relay discovery notices; and

[0700] Note 1: The UE implementation ensures that the value of the self-assigned source layer 2 ID is different from that specified in Clause 7.2 for 5G Any other self-assigned source layer 2 ID for ProSe direct communication, different from any other pre-configured destination layer 2 ID as specified in Clause 5.2, and different from any other self-assigned source layer 2 ID for simultaneous 5G ProSe direct discovery process via PC5 using different discovery models as specified in Clauses 6.2.14.2.2.2, 6.2.15.2.2.2, 8.2.1.3.1.2 and 8a.2.1.3.1.2.

[0701] f) Pass the resulting PROSE PC5 DISCOVERY message for inter-UE relay discovery announcement to the lower layer for transmission via the PC5 interface, the message having a source layer 2 ID, a destination layer 2 ID and an indication that the message is for 5G ProSe direct discovery.

[0702] Until the UE is triggered by the upper layer to stop announcing the availability of the connection service provided by the 5G ProSe inter-UE relay UE, or until the UE stops being authorized to perform the UE-to-UE relay discovery announcement process,

[0703] a) If the protected user information list of the 5G ProSe end UE with the associated relay service code is the same as the relay service code to be announced, the UE will ensure that it continues to pass the same PROSE PC5 DISCOVERY message together with the same source layer 2 ID, destination layer 2 ID and indication of the message for 5G ProSe direct discovery to the lower layer for transmission, and specification pages 49 / 68 52 CN 121218295 A

[0704] b) If the protected user information list of the 5G ProSe end UE with the associated relay service code is the same as the relay service code to be announced in the UE is updated, for example, 5G When new protected user information is available for the 5G ProSe UE, or when one or more protected user information entries for the 5G ProSe UE are removed due to the expiration of the associated validity timer, the UE will generate and protect a new PROSE PC5 DISCOVERY message (the message contains the associated relay service code, which is the same as the relay service code to be advertised for the 5G ProSe UE).The protected user information list of the UE), and pass the PR O SE PC5DISCOVERY message together with the source layer 2 ID, destination layer 2 ID and the indication of the message for 5G ProSe direct discovery to the lower layer for transmission.

[0705] Note 2: The notifying UE can stop the notification UE process of inter-UE relay discovery in an implementation-specific manner (e.g., the maximum number of implementation-specific 5G ProSe direct links configured in the UE, or the implementation-specific timer expiration) to save power.

[0706] 8a.2.1.2.2.3 Notification UE process of inter-UE relay discovery completion

[0707] When the notifying UE is triggered by the upper layer to stop the notification of the availability of 5G ProSe inter-UE relay, when the notifying UE stops being authorized to perform the notification UE process of inter-UE relay discovery, or when there is no set of direct discoveries to be notified available, the UE will instruct the lower layer to stop the notification.

[0708] Note: The notifying UE can stop the notification UE procedure for inter-UE relay discovery in an implementation-specific manner (e.g., the implementation-specific maximum number of 5G ProSe direct links configured in the UE, or the implementation-specific timer expiration) to save power.

[0709] When the UE stops the notification, if the UE is in 5GMM-CONNECTED mode, the UE will trigger the corresponding procedure in the lower layer as specified in 3GPP TS 38.331.

[0710] …

[0711] 8a.2.3.3 Candidate 5G ProSe Inter-UE Relay Discovery Procedure

[0712] The purpose of the candidate 5G ProSe Inter-UE Relay Discovery Procedure is to support the target 5G ProSe UE in discovering candidate 5G ProSe Inter-UE Relay UEs when the target 5G ProSe end UE needs to discover candidate 5G ProSe Inter-UE Relay UEs for negotiating 5G ProSe layer 3 inter-UE relay reselection, as specified in Clause 6.7.4 of 3GPP TS 23.304. This process is based on the PROSE PC5 DISCOVERY message for the inter-UE candidate relay discovery request and the PROSE PC5 DISCOVERY message for the inter-UE candidate relay discovery response.

[0713] a) When the target 5G ProSe end UE, which is the discoverer UE, generates the PROSE PC5 DISCOVERY message for the inter-UE candidate relay discovery request, in the PROSE PC5 DISCOVERY message for the inter-UE candidate relay discovery request, the UE will:

[0714] 1) Set the relay service code parameter to the relay service code parameter currently used with the service 5G inter-UE relay UE that needs inter-UE relay reselection;

[0715] 2) Set the inter-UE relay UE information parameter to the candidate 5GThe user information ID of the ProSe inter-UE relay UE; and

[0716] 3) does not include the direct discovery set parameter,

[0717] and sets the destination layer 2 ID to the destination layer 2 ID of the candidate 5G ProSe inter-UE relay UE received in the PROSE DIRECT LINK MODIFICATION REQUEST message during the agreed 5G ProSe layer 3 inter-UE relay reselection process. If the Layer 2 ID of the candidate 5G ProSe inter-UE relay UE is not received in the PROSE DIRECT LINK MODIFICATION REQUEST message during the agreed 5G ProSe Layer 3 UE relay reselection process, the UE sets the destination Layer 2 ID to the default Layer 2 ID used for discovery, as specified in Clause 5.2.7;

[0718] b) When the 5G ProSe inter-UE relay UE receives the PROSE PC5 DISCOVERY message for the inter-UE candidate relay discovery request, the 5G ProSe inter-UE relay will not perform the relay UE discovery process if the following conditions exist:

[0719] 2) The inter-UE relay UE information parameters in the PROSE PC5 DISCOVERY message for the inter-UE candidate relay discovery request match the user information ID used for the 5G ProSe inter-UE relay UE;

[0720] c) After b), the 5G ProSe The inter-UE relay UE will send a PROSE PC5 DISCOVERY message to the discoverer UE in response to the inter-UE candidate relay discovery. In the PROSE PC5 DISCOVERY message responding to the inter-UE candidate relay discovery, the UE will:

[0721] 1) set the relay service code parameter to the relay service code parameter of the PROSE PC5 DISCOVERY message for inter-UE relay discovery request received from the target 5G ProSe UE; and

[0722] 2) not include the direct discovery set parameter; and

[0723] d) after c), when the target 5G ProSe UE receives the PROSE PC5 DISCOVERY message responding to the inter-UE relay discovery, and if

[0724] 1) the relay service code parameter of the PROSE PC5 DISCOVERY message responding to the inter-UE relay discovery is the same as the relay service code parameter of the PROSE PC5 DISCOVERY message for inter-UE relay discovery request;

[0725] c) the inter-UE relay UE information parameter of the PROSE PC5 DISCOVERY message responding to the inter-UE relay discovery is the same as the relay service code parameter of the PROSE PC5 DISCOVERY message for inter-UE relay discovery request;If the user information ID of the candidate 5G ProSe inter-UE relay UE is the same as that of the PROSE PC5 DISCOVERY message requesting inter-UE relay discovery,

[0726] then the 5G ProSe end UE will consider discovering the candidate 5G ProSe inter-UE relay UE and perform the 5G ProSe direct link modification process for inter-UE relay UE reselection.

[0727] …

[0728] 10.2.1 Message Definition

[0729] This message is sent by the UE through the PC5 interface and is used to enable 5G ProSe direct discovery and restrict 5G ProSe direct discovery. See Tables 10.2.1.1, 10.2.1.2, 10.2.1.3, 10.2.1.4, 10.2.1.5, 10.2.1.6, 10.2.1.7, 10.2.1.8, 10.2.1.9, 10.2.1.10, 10.2.1.11, 10.2.1.12, 10.2.1.13, and 10.2.1.14.

[0730] Message Type: PROSE PC5 DISCOVERY

[0731] Meaning: Dual

[0732] Direction: UE to peer UE

[0733] ​​…

[0734] Table 10.2.1.12: PROSE PC5 DISCOVERY Message Description for Inter-UE Relay Discovery Announcement 51 / 68 pages 54 CN 121218295 A

[0735]

[0736]

[0737] Table 10.2.1.13: PROSE PC5 DISCOVERY Message Description for Inter-UE Relay Discovery Request 52 / 68 pages 55 CN 121218295 A

[0738]

[0739]

[0740] Table 10.2.1.14: PROSE PC5 DISCOVERY Message Description for Inter-UE Relay Discovery Response 53 / 68 pages 56 CN 121218295 A

[0741]

[0742] Table 10.2.1.x: PROSE PC5 DISCOVERY message for UE-to-UE candidate relay discovery request, specification 54 / 68 pages, 57 CN 121218295 A

[0743]

[0744] Table 10.2.1.y: PROSE PC5 DISCOVERY message for UE-to-UE candidate relay discovery response

[0745] Specification 55 / 68 pages, 58 CN 121218295 A

[0746]

[0747] …

[0748] 11.2.x Candidate discovery support indication

[0749] The Candidate Discovery Support Indication parameter is used to indicate whether a relay UE supports transmitting and receiving the new type of ProSe Direct Discovery PC5 message during the candidate relay discovery process between 5G ProSe UEs.

[0750] The Candidate Discovery Support Indication is a Type 1 information element with a length of 1 octet.

[0751] The Candidate Discovery Support Indication is encoded as shown in Figure 11.2.x.1 and Table 11.2.x.1.

[0752] Figure 27 depicts the new Figure 11.2.x.1: Candidate Discovery Support Indication information element.

[0753] Table 11.2.x.1: Candidate Discovery Support Indication Information Elements

[0754]

[0755] ******End of Change******

[0756] For example, a text proposal that surpasses the relevant solution in [2]TS 24.554 can be shown below, where changes and edits are indicated by underscores and strikethroughs:

[0757] ******Start of Change****** Specification 56 / 68 pages 59 CN 121218295 A

[0758] 8a.2.3.3 Candidate 5G ProSe UE Inter-Relay Discovery Procedure

[0759] The purpose of the candidate 5G ProSe UE Inter-Relay Discovery Procedure is to support the target 5G ProSe UE in discovering candidate 5G ProSe UE Inter-Relay UEs when the target 5G ProSe end UE needs to discover candidate 5G ProSe UE Inter-Relay UEs for negotiating 5G ProSe layer 3 UE inter-relay reselection, as specified in Clause 6.7.4 of 3GPP TS 23.304. This process is based on the UE inter-relay discovery process using Model B via the PC5 interface, as specified in Clause 8a.2.1.3, with the following modifications:

[0760] a) When the target 5G ProSe end UE, acting as the discoverer UE, generates a PROSE PC5 DISCOVERY message for the UE inter-relay discovery request, in the PROSE PC5 DISCOVERY message for the UE inter-relay discovery request, the UE will:

[0761] 1) set the relay service code parameter to the relay service code parameter currently used with the service 5G UE inter-relay UE that requires UE inter-relay reselection;

[0762] 2) set the UE inter-relay UE information parameter to the user information ID of the candidate 5G ProSe UE inter-relay UE; and

[0763] 3) set the candidate discovery indication.

[0764] And the destination layer 2 ID is set to the destination layer 2 ID of the candidate 5G ProSe UE-to-UE relay UE received in the PROSE DIRECT LINK MODIFICATION REQUEST message during the agreed 5G ProSe layer 3 UE-to-UE relay reselection process. If during the agreed 5GIf the Layer 2 ID of the candidate 5G ProSe inter-UE relay UE is not received in the PROSE DIRECT LINK MODIFICATION REQUEST message during the ProSe Layer 3 UE relay reselection process, the UE sets the destination Layer 2 ID to the default Layer 2 ID used for discovery, as specified in Clause 5.2.7;

[0765] b) When the 5G ProSe inter-UE relay UE receives a PROSE PC5 DISCOVERY message for inter-UE relay discovery request, the 5G ProSe inter-UE relay will not perform the relay UE discovery process if the following conditions exist:

[0766] 1) It contains a candidate discovery indication; and

[0767] 2) The inter-UE relay UE information parameters in the PROSE PC5 DISCOVERY message for inter-UE relay discovery request match the user information ID used for the 5G ProSe inter-UE relay UE;

[0768] c) After b), the 5G ProSe The UE relaying UE will send a PROSE PC5 DISCOVERY message to the discoverer UE in response to the UE relay discovery. In the PROSE PC5 DISCOVERY message for the inter-UE relay discovery response, the UE will:

[0769] 1) set the relay service code parameter to the relay service code parameter of the PROSE PC5 DISCOVERY message for the inter-UE relay discovery request received from the target 5G ProSe UE; and

[0770] 2) set a candidate discovery indication; and

[0771] d) after c), when the target 5G ProSe UE receives the PROSE PC5 DISCOVERY message for the inter-UE relay discovery response, and if

[0772] 1) the relay service code parameter of the PROSE PC5 DISCOVERY message for the inter-UE relay discovery response is the same as the relay service code parameter of the PROSE PC5 DISCOVERY message for the inter-UE relay discovery request; and

[0773] b) include a candidate discovery indication; and

[0774] c) the PROSE PC5 DISCOVERY message for the inter-UE relay discovery response... If the UE information parameters of the DISCOVERY message are the same as the user information ID of the candidate 5G ProSe UE-to-UE relay UE in the PROSE PC5 DISCOVERY message requesting UE-to-UE relay discovery,

[0775] then the 5G ProSe UE will consider discovering the candidate 5G ProSe UE-to-UE relay UE and perform the 5G ProSe direct link modification process for UE-to-UE relay UE reselection.

[0776] … Specification pages 57 / 68 60 CN 121218295 A

[0777] 10.2.1 Message Definition

[0778] This message is sent by the UE through the PC5 interface and is used to enable 5G ProSe direct discovery and restrict 5G ProSe direct discovery. See Tables 10.2.1.1, 10.2.1.2, 10.2.1.3, 10.2.1.4, 10.2.1.5, 10.2.1.6, 10.2.1.7, 10.2.1.8, 10.2.1.9, 10.2.1.10, 10.2.1.11, 10.2.1.12, 10.2.1.13 and 10.2.1.14.

[0779] Message type: PROSE PC5 DISCOVERY

[0780] Meaning: Dual

[0781] Direction: UE to peer UE

[0782] …

[0783] Table 10.2.1.13: PROSE PC5 DISCOVERY message for inter-UE relay discovery request

[0784]

[0785] Table 10.2.1.14: PROSE PC5 DISCOVERY message for inter-UE relay discovery response Specification 58 / 68 pages 61 CN 121218295 A

[0786]

[0787]

[0788] …

[0789] 11.2.z Candidate discovery indication

[0790] The candidate discovery support indication parameter is used to indicate whether the message is used in the 5G ProSe inter-UE candidate relay discovery process.

[0791] The candidate discovery indication is a type 1 information element with a length of 1 octet.

[0792] The candidate discovery indication IE is encoded as shown in Figure 11.2.z.1 and Table 11.2.z.1.

[0793] Figure 28 depicts the new Figure 11.2.z.1: Candidate discovery indication information element.

[0794] Table 11.2.z.1: Candidate Discovery Indication Information Element Specification 59 / 68 pages 62 CN 121218295 A

[0795]

[0796] ******End of Change******

[0797] For example, a text proposal that surpasses the relevant solution of [2]TS 24.554 can be shown below, where changes and edits are shown with underscores and strikethroughs:

[0798] ******Start of Change******

[0799] 8a.2.3.3 Candidate 5G ProSe UE Inter-Relay Discovery Procedure

[0800] The purpose of the candidate 5G ProSe UE inter-relay discovery procedure is to support the target 5G ProSe UE in discovering candidate 5G ProSe UE inter-relay UEs when the target 5G ProSe end UE needs to discover candidate 5G ProSe UE inter-relay UEs for negotiating 5G ProSe layer 3 UE inter-relay reselection.Inter-UE relay UE, as specified in Clause 6.7.4 of 3GPP TS 23.304. This process is based on the inter-UE relay discovery process using Model B via the PC5 interface, as specified in Clause 8a.2.1.3, with the following modifications:

[0801] a) When the target 5G ProSe end UE, acting as the discoverer UE, generates a PROSE PC5 DISCOVERY message for an inter-UE relay discovery request, in the PROSE PC5 DISCOVERY message for the inter-UE relay discovery request, the UE will:

[0802] 1) Set the relay service code parameter to the relay service code parameter currently used with the service 5G inter-UE relay UE that requires inter-UE relay reselection;

[0803] 2) Set the inter-UE relay UE information parameter to the user information ID of the candidate 5G ProSe inter-UE relay UE; and

[0804] 3) Set one or more fields in the direct discovery set IE to specific values.

[0805] And the destination layer 2 ID is set to the destination layer 2 ID of the candidate 5G ProSe UE-to-UE relay UE received in the PROSE DIRECT LINK MODIFICATION REQUEST message during the agreed 5G ProSe layer 3 UE-to-UE relay reselection process. If the Layer 2 ID of the candidate 5G ProSe inter-UE relay UE is not received in the PROSE DIRECT LINK MODIFICATION REQUEST message during the agreed 5G ProSe Layer 3 UE relay reselection process, the UE sets the destination Layer 2 ID to the default Layer 2 ID used for discovery, as specified in Clause 5.2.7;

[0806] b) When the 5G ProSe inter-UE relay UE receives a PROSE PC5 DISCOVERY message for inter-UE relay discovery request, the 5G ProSe inter-UE relay UE does not perform the inter-UE relay discovery relay UE process if the following conditions exist:

[0807] 1) One or more fields in the Direct Discovery Set IE match the pre-configured values; and

[0808] 2) The inter-UE relay UE information parameters in the PROSE PC5 DISCOVERY message for inter-UE relay discovery request match the user information ID used for the 5G ProSe inter-UE relay UE;

[0809] c) After b), the 5G ProSe The inter-UE relay UE will send a PROSE PC5 DISCOVERY message in response to the inter-UE relay discovery to the discovering UE. In the PROSE PC5 DISCOVERY message in response to the inter-UE relay discovery, the UE will:

[0810] 1) Set the relay service code parameter to the target 5GThe relay service code parameters received by the ProSe UE in the PROSE PC5 DISCOVERY message requesting inter-UE relay discovery (pages 60 / 68, CN 121218295 A); and

[0811] 2) setting one or more fields in the Direct Discovery Set IE to specific values; and

[0812] d) after c), when the target 5G ProSe UE receives the PROSE PC5 DISCOVERY message in response to inter-UE relay discovery, and if

[0813] 1) the relay service code parameters of the PROSE PC5 DISCOVERY message in response to inter-UE relay discovery are the same as the relay service code parameters of the PROSE PC5 DISCOVERY message in requesting inter-UE relay discovery; and

[0814] b) one or more fields in the Direct Discovery Set IE match the pre-configured values; and

[0815] c) the PROSE PC5 DISCOVERY message in response to inter-UE relay discovery... The UE information parameters of the DISCOVERY message are the same as the user information ID of the candidate 5G ProSe UE inter-relay UE in the PROSE PC5 DISCOVERY message for the UE inter-relay discovery request.

[0816] Then the 5G ProSe end UE will consider discovering the candidate 5G ProSe UE inter-relay UE and perform the 5G ProSe direct link modification process for UE inter-relay UE reselection.

[0817] …

[0818] 11.2.17 Direct Discovery Set

[0819] The purpose of the direct discovery set information element is to carry the direct discovery set, as specified in 3GPP TS 33.503.

[0820] The direct discovery set information element is a Type 6 information element with a minimum length of 12 octets and a maximum length of 520 octets.

[0821] The direct discovery set information element is encoded as shown in Figure 11.2.17.1 and Table 11.2.17.1.

[0822] If the IE is included in a PROSE PC5DISCOVERY message for an inter-UE relay discovery request message and the message is used for candidate U2U relay discovery, one or more fields will be set to specific values.

[0823] If the IE is included in a PROSE PC5DISCOVERY message for an inter-UE relay discovery response message and the message is used for candidate U2U relay discovery, one or more fields should be set to specific values.

[0824] Figure 29 depicts Figure 11.2.17.1: Direct Discovery Set Information Elements.

[0825] Figure 30 depicts Figure 11.2.17.2: List of Protected User Information IDs.

[0826] Figure 31 depicts Figure 11.2.17.3: Protected User Information.

[0827] Table 11.2.17.1: Direct Discovery Set Information Element Specification 61 / 68 pages 64 CN 121218295 A

[0828]

[0829] ******End of Change******

[0830] For example, a text proposal that surpasses the relevant solution in [2]TS 24.554 can be shown below, where changes and edits are shown with underscores and strikethroughs:

[0831] ******Start of Change******

[0832] 8a.2.3.3 Candidate 5G ProSe UE Inter-Relay Discovery Procedure

[0833] The purpose of the candidate 5G ProSe UE inter-relay discovery procedure is to support the target 5G ProSe UE in discovering candidate 5G ProSe UE inter-relay UEs when the target 5G ProSe end UE needs to discover candidate 5G ProSe UE inter-relay UEs for negotiating 5G ProSe layer 3 UE inter-relay reselection, as specified in Clause 6.7.4 of 3GPP TS 23.304. This process is based on the UE inter-relay discovery process using Model B via the PC5 interface, as specified in Clause 8a.2.1.3, with the following modifications:

[0834] a) When the target 5G ProSe end UE, acting as the discoverer UE, generates a PROSE PC5 DISCOVERY message for the UE inter-relay discovery request, in the PROSE PC5 DISCOVERY message for the UE inter-relay discovery request, the UE will:

[0835] 1) set the relay service code parameter to the relay service code parameter currently used with the serving 5G UE inter-relay UE that requires UE inter-relay reselection; and

[0836] 2) set the UE inter-relay UE information parameter to the user information ID of the candidate 5G ProSe UE inter-relay UE;

[0837] and set the destination layer 2 ID to the candidate 5G ProSe UE inter-relay UE received in the PROSE DIRECT LINK MODIFICATION REQUEST message during the agreed 5G ProSe layer 3 UE inter-relay reselection process. If the destination layer 2 ID of the inter-UE relay UE is agreed upon;

[0838] b) When the 5G ProSe inter-UE relay UE receives a PROSE PC5 DISCOVERY message for inter-UE relay discovery request, the 5G ProSe inter-UE relay will not perform the relay UE discovery process if the following conditions exist:

[0839] 1) The destination layer 2 ID of the PROSE PC5 DISCOVERY message for inter-UE relay discovery request is set to the destination layer 2 ID of the candidate 5G ProSe inter-UE relay UE; and

[0840] 2) The PROSE PC5 message for inter-UE relay discovery request is set to the destination layer 2 ID of the candidate 5G ProSe inter-UE relay UE;The UE information parameters of the DISCOVERY message are matched with the user information ID used for the 5G ProSe UE inter-relay UE; Specification 62 / 68 pages 65 CN 121218295 A

[0841] c) After b), the 5G ProSe UE inter-relay UE will send a PROSE PC5 DISCOVERY message for the UE inter-relay discovery response to the discoverer UE. In the PROSE PC5 DISCOVERY message responding to the inter-UE relay discovery request, the UE will:

[0842] 1) set the relay service code parameter to the relay service code parameter of the PROSE PC5 DISCOVERY message for the inter-UE relay discovery request received from the target 5G ProSe UE;

[0843] d) after c), when the target 5G ProSe UE receives the PROSE PC5 DISCOVERY message responding to the inter-UE relay discovery request, and if

[0844] 1) the relay service code parameter of the PROSE PC5 DISCOVERY message responding to the inter-UE relay discovery request is the same as the relay service code parameter of the PROSE PC5 DISCOVERY message for the inter-UE relay discovery request; and

[0845] b) the destination layer 2ID of the corresponding PROSE PC5 DISCOVERY message for the inter-UE relay discovery request is set to the destination layer 2ID of the candidate 5G ProSe inter-UE relay UE; and

[0846] c) If the UE information parameters of the PROSE PC5 DISCOVERY message in response to the inter-UE relay discovery are the same as the user information ID of the candidate 5G ProSe inter-UE relay UE in the PROSE PC5 DISCOVERY message in response to the inter-UE relay discovery request,

[0847] then the 5G ProSe end UE will consider discovering the candidate 5G ProSe inter-UE relay UE and perform the 5G ProSe direct link modification process for inter-UE relay UE reselection.

[0848] ******End of Change******

[0849] Various examples and embodiments of the present invention are described below. The following aspects and embodiments are possible with respect to the methods, alternatives, concepts, examples, and embodiments detailed above and herein.

[0850] Referring to FIG. 32, utilizing this concept and other concepts, systems, and methods of the present invention, a method 1000 for a relay UE in a wireless communication system includes: receiving a discovery request message from a target UE, wherein the discovery request message contains information indicating that the discovery request message is used for candidate U2U relay discovery (step 1002); and responding to receiving the message containing information indicating that the discovery request message is used for candidate U2U relay discovery (step 1002).The relay UE sends a discovery request message to the target UE and does not perform the U2U relay discovery process (step 1004).

[0851] In various embodiments, not performing the U2U relay discovery process means that the relay UE does not send another discovery request message to the other UE in response to receiving the discovery request message.

[0852] In various embodiments, the discovery response message contains information indicating that the discovery response message is used for candidate U2U relay discovery.

[0853] In various embodiments, the discovery response message sent by the relay UE is a PROSE PC5 DISCOVERY message for inter-UE relay discovery response messages.

[0854] In various embodiments, the discovery request message sent by the target UE is a PROSE PC5 DISCOVERY message for inter-UE relay discovery request messages.

[0855] In various embodiments, the information is an information element.

[0856] In various embodiments, the information is an indication IE or a candidate discovery indication IE.

[0857] In various embodiments, the information is at least user information set to a specific value, for example, 0.

[0858] In various embodiments, the information is a specific number of protected user information.

[0859] In various embodiments, the information is a specific length of the Direct Discovery Set (IE).

[0860] In various embodiments, the connection is a PC5 connection, a PC5-S connection, a PC5-Radio Resource Control (RRC) connection, a Layer 2 link, a unicast link, or a direct link. Specification 63 / 68 pages 66 CN 121218295 A

[0861] Referring back to Figures 3 and 4, in one or more embodiments from the perspective of a relay UE in a wireless communication system, apparatus 300 includes program code 312 stored in memory 310 of a transmitter. CPU 308 can execute program code 312 to: (i) receive a discovery request message from a target UE, wherein the discovery request message contains information indicating that the discovery request message is used for candidate U2U relay discovery; and (ii) in response to receiving a discovery request message containing the information, the relay UE transmits a discovery response message to the target UE and does not perform the U2U relay discovery process. Furthermore, CPU 308 can execute program code 312 to perform all the actions, steps, and methods described above, below, or otherwise herein.

[0862] Various examples and embodiments of the invention are described below. The following aspects and embodiments are possible with respect to the methods, alternatives, concepts, examples, and embodiments detailed above and herein.

[0863] Referring to FIG33, utilizing this and other concepts, systems, and methods of the invention, a wireless communication system...The method 1010 for the target UE includes: establishing a connection with a relay UE to support inter-UE relay communication between the source UE and the target UE via the relay UE (step 1012); receiving from the source UE a link modification request message indicating at least one candidate relay UE for performing agreed relay reselection (step 1014); transmitting a discovery request message to the candidate relay UE, wherein the discovery request message includes information indicating that the discovery request message is used for candidate U2U relay discovery (step 1016); receiving a discovery response message from the candidate relay UE (step 1018); and transmitting a link modification acceptance message to the source UE indicating the candidate relay UE (step 1020).

[0864] In various embodiments, the discovery response message includes information indicating that the discovery request message is used for candidate U2U relay discovery.

[0865] In various embodiments, the target UE considers that a candidate relay UE has been discovered in response to receiving a discovery response message containing information indicating that the discovery request message is for candidate U2U relay discovery.

[0866] In various embodiments, the discovery response message sent by the relay UE is a PROSE PC5 DISCOVERY message for an inter-UE relay discovery response message.

[0867] In various embodiments, the discovery request message sent by the target UE is a PROSE PC5 DISCOVERY message for an inter-UE relay discovery request message.

[0868] In various embodiments, the information is an information element.

[0869] In various embodiments, the information is an indication IE or a candidate discovery indication IE.

[0870] In various embodiments, the information is at least user information set to a specific value, for example, 0.

[0871] In various embodiments, the information is a specific number of protected user information.

[0872] In various embodiments, the information is a specific length of a direct discovery set IE.

[0873] In various embodiments, the connection is a PC5 connection, a PC5-S connection, a PC5-RRC connection, a Layer 2 link, a unicast link, or a direct link.

[0874] Referring back to Figures 3 and 4, in one or more embodiments from the perspective of a target UE in a wireless communication system, apparatus 300 includes program code 312 stored in memory 310 of the transmitter. CPU 308 can execute program code 312 to: (i) establish a connection with a relay UE to support inter-UE relay communication between a source UE and a target UE via the relay UE; (ii) receive from the source UE a link modification request message indicating at least one candidate relay UE for performing an agreed relay reselection; and (iii) transmit a discovery request message to the candidate relay UE, wherein the discovery request message includes an indication of a discovery request.The message is used for information on candidate U2U relay discovery; (iv) receiving a discovery response message from the candidate relay UE; and (v) transmitting a link modification acceptance message indicating the candidate relay UE to the source UE. Furthermore, CPU 308 can execute program code 312 to perform all the actions, steps, and methods described above, below, or otherwise herein. Specification 64 / 68 pages 67 CN 121218295 A

[0875] Various examples and embodiments of the invention are described below. The following aspects and embodiments are possible with respect to the methods, alternatives, concepts, examples, and embodiments detailed above and herein.

[0876] Referring to FIG34, utilizing this and other concepts, systems, and methods of the present invention, a method 1030 for a relay UE in a wireless communication system includes: receiving a first discovery request message from a first target UE, wherein the first discovery request message is received or addressed to a default layer 2 ID for discovery using a default layer 2 ID for discovery as the destination layer 2 ID (step 1032); in response to receiving the first discovery request message addressed to the default layer 2 ID, performing a U2U relay discovery process (step 1034); receiving a second discovery request message from a second target UE, wherein the second discovery request message is received or addressed to a layer 2 ID of the relay UE using a layer 2 ID of the relay UE as the destination layer 2 ID (step 1036); and in response to receiving the second discovery request message addressed to the layer 2 ID of the relay UE, not performing the U2U relay discovery process (step 1038).

[0877] In various embodiments, the relay UE transmits a third discovery request message during the U2U relay discovery process.

[0878] In various embodiments, not performing the U2U relay discovery process means that the relay UE does not transmit another discovery request message.

[0879] In various embodiments, the discovery request message sent by the relay UE is a PROSE PC5 DISCOVERY message for an inter-UE relay discovery request message.

[0880] Referring back to Figures 3 and 4, in one or more embodiments from the perspective of a relay UE in a wireless communication system, apparatus 300 includes program code 312 stored in memory 310 of a transmitter. CPU 308 can execute program code 312 to: (i) receive a first discovery request message from a first target UE, wherein the first discovery request message is received or addressed to a default 2ID for discovery using a default 2ID for discovery as the destination 2ID; (ii) in response to receiving the first discovery request message addressed to the default 2ID, perform the U2U relay discovery process; (iii) receive a second discovery request message from a second target UE, wherein the second discovery request message is received using the 2ID of the relay UE.(iv) The Layer 2 ID to be received or addressed to the relay UE as the destination Layer 2 ID; and (iv) in response to receiving a second discovery request message to the Layer 2 ID addressed to the relay UE, the U2U relay discovery process is not performed. Furthermore, CPU 308 may execute program code 312 to perform all the actions, steps, and methods described above, below, or otherwise herein.

[0881] Various examples and embodiments of the invention are described below. The following aspects and embodiments are possible with respect to the methods, alternatives, concepts, examples, and embodiments detailed above and herein.

[0882] Referring to FIG. 35, utilizing this and other concepts, systems, and methods of the present invention, a method 1040 for a second-end UE in a wireless communication system includes: sending a first discovery request message, wherein if the first discovery request message is used for U2U relay discovery, the first discovery request message is sent or addressed to the default layer 2 ID used for discovery using a default layer 2 ID for discovery as the destination layer 2 ID (step 1042); and sending a second discovery request message, wherein if the second discovery request message is used for candidate U2U relay discovery, the second discovery request message is sent or addressed to the layer 2 ID of the candidate relay UE using the layer 2 ID of the candidate relay UE as the destination layer 2 ID (step 1044).

[0883] In various embodiments, the second-end UE establishes a connection with a relay UE to support first U2U relay communication between the first-end UE and the second-end UE via the relay UE.

[0884] In various embodiments, the second-end UE receives a link modification request message from the first-end UE via a relay UE, indicating a candidate relay UE to perform agreed relay reselection.

[0885] In various embodiments, the link modification request message includes the Layer 2 ID of the candidate relay UE.

[0886] In various embodiments, the second-end UE receives a first discovery response message from the candidate relay UE.

[0887] In various embodiments, in response to receiving the first discovery response message, the second-end UE sends a link modification acceptance message indicating the candidate relay UE to the source end specification page 65 / 68, CN 121218295 A UE via a relay UE.

[0888] In various embodiments, the first discovery request message includes user information of the third-end UE and user information of the second-end UE.

[0889] In various embodiments, the second-end UE receives a second discovery response message from the second relay UE.

[0890] In various embodiments, the second-end UE establishes a connection with the second relay UE based on the second discovery response message to support second U2U relay communication between the third-end UE and the second-end UE via the second relay UE.

[0891] In various embodiments, the first / second discovery request message sent by the second-end UE is a PROSE PC5 response to the inter-UE relay discovery request message.DISCOVERY message.

[0892] In various embodiments, the first / second discovery request message sent by the second-end UE is a PROSE PC5 DISCOVERY message in response to the inter-UE relay discovery request message.

[0893] In various embodiments, the first / second discovery response message sent by the second-end UE is a PROSE PC5 DISCOVERY message in response to the inter-UE relay discovery response message.

[0894] In various embodiments, in the first U2U relay communication, the first-end UE is the source UE, and the second-end UE is the target UE.

[0895] In various embodiments, in the second U2U relay communication, the third-end UE is the target UE, and the second-end UE is the source UE.

[0896] Referring back to Figures 3 and 4, in one or more embodiments viewed from the perspective of the second-end UE in the wireless communication system, the apparatus 300 includes program code 312 stored in the memory 310 of the transmitter. CPU 308 may execute program code 312 to: (i) send a first discovery request message, wherein if the first discovery request message is used for U2U relay discovery, the first discovery request message is sent or addressed to the default tier 2 ID used for discovery using the default tier 2 ID used for discovery as the destination tier 2 ID; and (ii) send a second discovery request message, wherein if the second discovery request message is used for candidate U2U relay discovery, the second discovery request message is sent or addressed to the tier 2 ID of the candidate relay UE using the tier 2 ID of the candidate relay UE. Furthermore, CPU 308 may execute program code 312 to perform all the actions, steps, and methods described above, below, or otherwise herein.

[0897] Referring to FIG. 36, utilizing this and other concepts, systems, and methods of the present invention, a method 1050 for a target UE in a wireless communication system includes: establishing a connection with a relay UE to support U2U relay communication between a source UE and a target UE via the relay UE (step 1052); receiving from the relay UE a link modification request message indicating a list of candidate relay UEs for performing an agreed relay reselection (step 1054); determining to transmit a discovery request message to a candidate relay UE in the candidate relay UE list, wherein the discovery request message indicates that the discovery request message is used for candidate U2U relay discovery by setting at least the application layer ID indicated in the discovery request message to a specific value (step 1056); receiving from the candidate relay UE a discovery response message for candidate U2U relay discovery (step 1058); and transmitting to the relay UE a link modification acceptance message indicating the candidate relay UE (step 1060).

[0898] In various embodiments, the specific value is 0.

[0899] In various embodiments, the application layer ID is included in the user information field.

[0900] In various embodiments, the user information field is included in the direct discovery set.

[0901] In various embodiments, the discovery request message further indicates that the discovery request message is used for candidate U2U relay discovery by the number of user information in the direct discovery set being 1.

[0902] In various embodiments, the direct discovery set is mandatory in the discovery request message.

[0903] In various embodiments, the discovery response message received from the candidate relay UE is a PROSE PC5 DISCOVERY message for U2U relay discovery response (pages 66 / 68, CN 121218295 A), and the discovery request message transmitted by the target UE is a PROSE PC5 DISCOVERY message for U2U relay discovery request.

[0904] In various embodiments, the discovery response message indicates that the discovery response message is used for candidate U2U relay discovery by setting at least the second application layer ID indicated in the discovery response message to a specific value.

[0905] In various embodiments, the method further includes: determining, based on the second application layer ID being set to a specific value, that a discovery response message is used for candidate U2U relay discovery.

[0906] In various embodiments, the agreed relay reselection is triggered by the source UE.

[0907] Referring back to Figures 3 and 4, in one or more embodiments from the perspective of the target UE in the wireless communication system, apparatus 300 includes program code 312 stored in the transmitter's memory 310. CPU 308 may execute program code 312 to: (i) establish a connection with a relay UE to support U2U trunk communication between a source UE and a target UE via the relay UE; (ii) receive from the relay UE a link modification request message indicating a list of candidate relay UEs for performing an agreed trunk reselection; (iii) determine to transmit a discovery request message to a candidate relay UE in the candidate relay UE list, wherein the discovery request message indicates that the discovery request message is used for candidate U2U trunk discovery by setting at least the application layer ID indicated in the discovery request message to a specific value; (iv) receive a discovery response message from a candidate relay UE for candidate U2U trunk discovery; and (v) transmit a link modification acceptance message to the relay UE indicating the candidate relay UE. Furthermore, CPU 308 may execute program code 312 to perform all the actions, steps, and methods described above, below, or otherwise herein.

[0908] It should be noted that any methods, alternatives, steps, examples, and embodiments presented herein may be applied independently, alone, and / or in combination with multiple methods, alternatives, steps, examples, and embodiments.

[0909] Various aspects of this disclosure have been described above. It should be understood that the teachings herein can be embodied in a wide variety of forms, and any particular structure, function, or both disclosed herein are merely representative. Based on the teachings herein, those skilled in the art will understand 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, an apparatus or method can be implemented using any number of aspects set forth herein. Furthermore, this apparatus or method can be implemented using structures, functions, or structures and functions other than or different from one or more of the aspects set forth herein. As examples of some of the foregoing concepts, in some aspects, a parallel channel can be established based on the pulse repetition frequency. In some aspects, a parallel channel can be established based on the pulse position or offset. In some aspects, a parallel channel can be established based on a time-hopping sequence. In some aspects, a parallel channel can be established based on the pulse repetition frequency, the pulse position or offset, and the time-hopping sequence.

[0910] Those skilled in the art will understand that information and signals can be represented using any of a variety of different techniques and methods. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the above description can be represented by voltage, current, electromagnetic waves, magnetic fields or magnetic particles, light fields or light particles, or any combination thereof.

[0911] Those skilled in the art will further understand that the various illustrative logic blocks, modules, processors, components, circuits, and algorithm steps described in conjunction with the aspects disclosed herein can be implemented as electronic hardware (e.g., digital implementations, analog implementations, or combinations thereof, which may be designed using source decoding or some other technique) and have various forms of process or design code with instructions (which may be referred to herein as "software" or "software module"), or combinations thereof. To clearly illustrate this interchangeability between hardware and software, the various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends on the specific application and the design constraints imposed on the system as a whole. Those skilled in the art can implement the described functions in different ways for each specific application, but such implementation decisions should not be construed as causing a deviation from the scope of this disclosure. Specification 67 / 68 pages 70 CN 121218295 A

[0912] Furthermore, the various illustrative logic blocks, modules, and circuits described in connection with aspects of this disclosure can be implemented within an integrated circuit (“IC”), access terminal, or access point, or derived from an integrated circuit, access terminal, or access point.Entry point execution. The 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 to execute code or instructions residing within the IC, outside the IC, or both. The general-purpose processor may be a microprocessor, but alternatively, the processor may be any conventional processor, controller, microcontroller, or state machine. The processor may 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 incorporating a DSP core, or any other such configuration.

[0913] It should be understood that any particular order or hierarchy of steps in any disclosed process is an instance of a sample method. It should be understood that a particular order or hierarchy of steps in the process may be rearranged based on design preferences while remaining within the scope of this disclosure. The accompanying method claims present the elements of the various steps in sample order, and are not intended to limit them to any particular order or hierarchy.

[0914] The steps of the methods or algorithms described in conjunction with the aspects disclosed herein can be implemented directly in hardware, with software modules executed by a processor, or with a combination of both. Software modules (e.g., containing executable instructions and associated data) and other data can reside in data memory, such as RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disks, removable disks, CD-ROMs, or any other form of computer-readable storage medium known in the art. Sample storage media can be coupled to a machine such as a computer / processor (for convenience, the machine 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. Sample storage media can be integrated with the processor. The processor and storage medium can reside in an ASIC. The ASIC can reside in a user equipment. Alternatively, the processor and storage medium can reside as discrete components in the user equipment. Furthermore, in some aspects, any suitable computer process product may include a computer-readable medium comprising code relating to one or more aspects of this disclosure. In some aspects, the computer process product may include packaging material.

[0915] While the invention has been described in conjunction with various aspects and examples, it should be understood that the invention is capable of further modifications.Modifications. This application is intended to cover any changes, uses, or adaptations of the invention that generally follow the principles of the invention and are included within the scope of known and customary practice in the to which this invention pertains. Instruction manual page 68 / 68, page 71, CN 121218295 A, Figure 1; Instruction manual figure 1 / 22 page, page 72, CN 121218295 A, Figure 2; Instruction manual figure 2 / 22 page, page 73, CN 121218295 A, Figure 3; Instruction manual figure 3 / 22 page, page 74, CN 121218295 A, Figure 4; Instruction manual figure 4 / 22 page, page 75, CN 121218295 A, Figure 6; Instruction manual figure 5 / 22 page, page 76, CN 121218295 A, Figure 7; Instruction manual figure 6 / 22 page, page 77, CN 121218295 A, Figure 8; Instruction manual figure 7 / 22 page, page 78, CN 121218295 A, Figure 9; Instruction manual figure 10; Instruction manual figure 8 / 22 page, page 79, CN 121218295 A, Figure 11; Instruction manual figure 12; Instruction manual figure 9 / 22 page, page 80, CN 121218295 Figure 13 Figure 14 Figure 15 Figure 16 Instruction Manual Drawings, Page 10 / 22, 81 CN 121218295 Figure 17 Figure 18 Figure 19 Figure 20 Instruction Manual Drawings, Page 11 / 22, 82 CN 121218295 Figure 21 Instruction Manual Drawings, Page 12 / 22, 83 CN 121218295 Figure 22 Instruction Manual Drawings, Page 13 / 22, 84 CN 121218295 Figure 23 Instruction Manual Drawings, Page 14 / 22, 85 CN 121218295 Figure 24 Instruction Manual Drawings, Page 15 / 22, 86 CN 121218295 Figure 25 Figure 26 Instruction Manual Drawings, Page 16 / 22, 87 CN 121218295 Figure 27 Figure 28 Figure 29 Figure 30 Instruction Manual Drawings, Page 17 / 22, 88 CN 121218295 Figure 31 Figure 32 Figure 33 of the instruction manual, page 18 / 22, 89 CN 121218295 A; Figure 34 of the instruction manual, page 19 / 22, 90 CN 121218295 A; Figure 35 of the instruction manual, page 20 / 22, 91 CN 121218295 A; Figure 36 of the instruction manual, page 21 / 22, 92 CN 121218295 A; (Instruction manual illustrations)Page 22 / 22 93 CN 121218295 A Abstract Abdominal ultrasound examination method, system and device P20260153HK00 Abstract METHOD AND APPARATUS FOR TARGET END UE SUPPORTING CANDIDATE U2U RELAY DISCOVERY Methods and apparatuses are provided for target end User Equipment (UE) supporting candidate UE-to-UE (U2U) relay discovery. A method for a target end UE comprises establishing a connection with a relay UE for supporting U2U relay communication between a source end UE and the target end UE via the relay UE, receiving a link modification request message indicating a list of candidate relay UEs from the relay UE for performing negotiated relay reselection, determining to transmit a discovery solicitation message to a candidate relay UE among the list of candidate relay UEs, wherein the discovery solicitation message indicates the discovery solicitation message being used for candidate U2U relay discovery by at least setting an application layer Identification (ID) indicated in the discoverysolicitation message to a specific value, receiving, from the candidate relay UE, a discovery response message for candidate U2U relay discovery, and transmitting a link modification accept message, indicating the candidate relay UE, to the relay UE. FIG. 36

Claims

1. A method for a target end user device, characterized by, comprises: establishing a connection with a relay user equipment to support inter-user equipment relay communication between a source user equipment and the target user equipment via the relay user equipment; receiving, from the relay user equipment, a link modification request message indicating a list of candidate relay user equipments for performing a negotiated relay reselection; determining to transmit a discovery solicitation message to a candidate relay user equipment in the list of candidate relay user equipments, wherein the discovery solicitation message indicates that the discovery solicitation message is used for candidate inter-user equipment relay discovery by at least setting an application layer identity indicated in the discovery solicitation message to a specific value; receiving, from the candidate relay user equipment, a discovery response message for candidate inter-user equipment relay discovery; and transmitting, to the relay user equipment, a link modification accept message indicating the candidate relay user equipment.

2. The method of claim 1, wherein, The specific value is 0.

3. The method of claim 1, wherein, The application layer identity is contained in a user information field.

4. The method of claim 3, wherein, The user information field is contained in a direct discovery set.

5. The method of claim 4, wherein, The discovery solicitation message further indicates that the discovery solicitation message is used for candidate inter-user equipment relay discovery by a number of user information in the direct discovery set being 1.

6. The method of claim 4, wherein, The direct discovery set is mandatory in the discovery solicitation message.

7. The method of claim 1, wherein, The discovery response message received from the candidate relay user equipment is a PROSE PC5 DISCOVERY message for inter-user equipment relay discovery response, and the discovery solicitation message transmitted by the target user equipment is a PROSE PC5 DISCOVERY message for inter-user equipment relay discovery solicitation.

8. The method of claim 1, wherein, The discovery response message indicates that the discovery response message is used for candidate inter-user equipment relay discovery by at least setting a second application layer identity indicated in the discovery response message to the specific value.

9. The method of claim 8, wherein, Further comprising: determining that the discovery response message is used for candidate inter-user equipment relay discovery based on the second application layer identity being set to the specific value.

10. The method of claim 1, wherein, The negotiated relay reselection is triggered by the source user equipment.

11. A target end user device, characterized by, comprises: a memory; and a processor operatively coupled with the memory, wherein the processor is configured to execute program code to: establish a connection with a relay user equipment to support inter-user equipment relay communication between a source user equipment and the target user equipment via the relay user equipment; receive, from the relay user equipment, a link modification request message indicating a list of candidate relay user equipments for performing a negotiated relay reselection; determine to transmit a discovery solicitation message to a candidate relay user equipment in the list of candidate relay user equipments, wherein the discovery solicitation message indicates that the discovery solicitation message is used for candidate inter-user equipment relay discovery by at least setting an application layer identity indicated in the discovery solicitation message to a specific value; receive, from the candidate relay user equipment, a discovery response message for candidate inter-user equipment relay discovery; and transmit, to the relay user equipment, a link modification accept message indicating the candidate relay user equipment. The specific value is 0.

12. The target end user device of claim 11, wherein, The application layer identity is contained in a user information field.

13. The target end user device of claim 11, wherein, ​ 14. The target end user device of claim 13, wherein, The user information field is included in a direct discovery set.

15. The target end user device of claim 14, wherein, The discovery solicitation message further indicates that the discovery solicitation message is used for candidate inter-user equipment relay discovery by a number of user information in the direct discovery set being 1.

16. The target end user device of claim 14, wherein, The direct discovery set is mandatory in the discovery solicitation message.

17. The target end user device of claim 11, wherein, The discovery response message received from the candidate relay user equipment is a PROSE PC5 DISCOVERY message for inter-user equipment relay discovery response, and the discovery solicitation message transmitted by the target end user equipment is a PROSE PC5 DISCOVERY message for inter-user equipment relay discovery solicitation.

18. The target end user device of claim 11, wherein, The discovery response message indicates that the discovery response message is used for candidate inter-user equipment relay discovery by at least setting a second application layer identity indicated in the discovery response message to the specific value.

19. The target end user device of claim 18, wherein, The processor is further configured to execute the program code to determine that the discovery response message is used for candidate inter-user equipment relay discovery based on the second application layer identity being set to the specific value.

20. The target end user device of claim 11, wherein, The agreed relay reselection is triggered by the source end user equipment. The discovery response message received from the candidate relay user equipment is a PROSE PC5 DISCOVERY message for inter-user equipment relay discovery response, and the discovery solicitation message transmitted by the target end user equipment is a PROSE PC5 DISCOVERY message for inter-user equipment relay discovery solicitation. The discovery response message indicates that the discovery response message is used for candidate inter-user equipment relay discovery by at least setting a second application layer identity indicated in the discovery response message to the specific value. The processor is further configured to execute the program code to determine that the discovery response message is used for candidate inter-user equipment relay discovery based on the second application layer identity being set to the specific value. The agreed relay reselection is triggered by the source end user equipment.

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