Method and relay user equipment for supporting inter-user equipment relay communication

Abstract

A method and a relay user equipment (UFO) for supporting inter-user equipment (UFO) relay communication are disclosed. The relay UFO supports UFO relay communication between a source UFO and a target UFO via the relay UFO. The relay UFO performs a user information update procedure for the target UFO according to the request of the source UFO. If the previous source UFO user information update procedure with the target UFO was successfully completed, the relay update request message sent from the relay UFO to the target UFO in the current update procedure includes the previous new user information of the source UFO as the old user information of the source UFO, even if the old user information provided by the source UFO to the relay UFO in this update is the previous old user information.

Description

[0001] Cross-references to related applications

[0002] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 669,617, filed July 10, 2024, the entire disclosure of 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 updating link identifiers in wireless communication systems to support inter-UE relay communication. Background Technology

[0004] With the rapid growth in demand for transmitting large amounts of data to and from mobile communication devices, traditional mobile voice communication networks have evolved into networks that communicate using Internet Protocol (IP) data packets. This IP data packet communication can provide users of mobile communication devices with IP-bearing voice, multimedia, multicast, and video-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-based voice and multimedia services. Currently, the 3GPP standards organization is discussing new next-generation (e.g., 5G) radio technologies. Therefore, changes to the current core of the 3GPP standards are currently being submitted and considered to facilitate their evolution and completion. Summary of the Invention

[0006] A method and apparatus for relaying user equipment (UE) are disclosed. In one embodiment, the relay UE establishes a first direct link with a source UE and a second direct link with a target UE, supporting UE-to-UE (U2U) relay communication between the source UE and the target UE via the relay UE. The relay UE also receives from the source UE a first link identifier update request message for updating the source UE's first user information to the source UE's second user information. Furthermore, in response to receiving the first link identifier update request message, the relay UE executes a first relay update procedure with the target UE, wherein the first relay update request message sent from the relay UE to the target UE in the first relay update procedure includes the source UE's first user information as the source UE's old user information and includes the source UE's second user information as the source UE's new user information. The relay UE also receives from the source UE a second link identifier update request message for updating the source UE's first user information to the source UE's third user information. In addition, in response to receiving the second link identifier update request message, the relay UE executes a second relay update procedure with the target UE. If the first relay update procedure with the target UE is successfully completed, the second relay update request message sent from the relay UE to the target UE in the second relay update procedure includes the second user information of the source UE as the old user information of the source UE and includes the third user information of the source UE as the new user information of the source UE. Attached Figure Description

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

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

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

[0010] Figure 4 This is based on an exemplary embodiment. Figure 3 Functional block diagram of the program code;

[0011] Figure 5 It is 3GPP TS 23.304 V18.6.0. Figure 4 Reproduction of .2.8-1;

[0012] Figure 6 It is 3GPP TS 23.304 V18.6.0. Figure 6Reproduction of .3.2.4.2-1;

[0013] Figure 7 It is 3GPP TS 23.304 V18.6.0. Figure 6 Reproduction of .3.2.4.3-1;

[0014] Figure 8 It is 3GPP TS 23.304 V18.6.0. Figure 6 Reproduction of 4.3.1-1;

[0015] Figure 9 It is 3GPP TS 23.304 V 18.6.0. Figure 6 Reproduction of .4.3.2-1;

[0016] Figure 10 It is 3GPP TS 23.304 V 18.6.0. Figure 6 Reproduction of .4.3.4-1;

[0017] Figure 11 It is 3GPP TS 23.304 V 18.6.0. Figure 6 Reproduction of 7.1.1-1;

[0018] Figure 12 It is 3GPP TS 23.304 V 18.6.0. Figure 6 Reproduction of .7.1.2-1;

[0019] Figure 13 It is 3GPP TS 23.304 V 18.6.0. Figure 6 Reproduction of .7.1.4-1;

[0020] Figure 14 It is 3GPP TS 23.304 V 18.6.0. Figure 6 Reproduction of .7.2-1;

[0021] Figure 15 It is 3GPP TS 23.304 V 18.6.0. Figure 6 Reproduction of .7.3.2-1;

[0022] Figure 16 It is 3GPP TS 23.304 V 18.6.0. Figure 6 Reproduction of 7.3.3-1;

[0023] Figure 17 It is 3GPP TS 24.554 V18.4.0. Figure 7 Reproduction of .2.2.2.1;

[0024] Figure 18 It is 3GPP TS 24.554 V18.4.0. Figure 7 Reproduction of .2.2.2.2;

[0025] Figure 19 It is 3GPP TS 24.554 V18.4.0. Figure 7 Reproduction of .2.4.2.1;

[0026] Figure 20 It is 3GPP TS 24.554 V18.4.0. Figure 7 Reproduction of .2.13.2.1;

[0027] Figure 21 This is a reproduction of Table 10.3.18.1.1 of 3GPP TS 24.554 V18.4.0;

[0028] Figure 22 This is a reproduction of Table 10.3.21.1.1 of 3GPP TS 24.554 V18.4.0;

[0029] Figure 23 This is a reproduction of Table 10.3.28.1.1 of 3GPP TS 24.554 V18.4.0;

[0030] Figure 24 This is a reproduction of Table 10.3.29.1.1 of 3GPP TS 24.554 V18.4.0;

[0031] Figure 25 This is a reproduction of Table 10.3.33.1.1 of 3GPP TS 24.554 V18.4.0;

[0032] Figure 26 This is a message flow diagram according to an exemplary embodiment;

[0033] Figure 27 This is a message flow diagram according to an exemplary embodiment;

[0034] Figure 28 This is a message flow diagram according to an exemplary embodiment;

[0035] Figure 29 This is a message flow diagram according to an exemplary embodiment;

[0036] Figure 30A and Figure 30B This is a message flow diagram according to an exemplary embodiment;

[0037] Figure 31 This is a flowchart based on an exemplary embodiment. Detailed Implementation

[0038] 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, and so on. 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 or LTE-Advanced), 3GPP2 Ultra Mobile Broadband (UMB), WiMax, 3GPP New Radio (NR), or some other modulation techniques.

[0039] 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 known herein as 3GPP, which is called the "3rd Generation Partnership Project," including: TS 23.304 v18.6.0, "Proximity-based Services (ProSe) in 5G Systems (5GS) (Revision 18)"; and TS 24.554 V18.4.0, "Proximity-services (ProSe) in Protocol Aspects of 5G Systems (5GS); Phase 3 (Revision 18)." The standards and documents listed above are expressly incorporated herein by reference in their entirety.

[0040] Figure 1 A multiple access wireless communication system according to an embodiment of the present invention is illustrated. Access network 100 (AN) includes multiple antenna groups, one antenna group comprising 104 and 106, another antenna group comprising 108 and 110, and yet another antenna group comprising 112 and 114. Figure 1In this diagram, only two antennas are shown for each antenna group; however, each antenna group can utilize more or fewer antennas. Access terminal 116 (AT) communicates with antennas 112 and 114, which transmit information to AT 116 via forward link 120 and receive information from AT 116 via reverse link 118. Access terminal (AT) 122 communicates with antennas 106 and 108, which 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 different frequency than the frequency used by reverse link 118.

[0041] Each antenna group and / or the area in which the antenna groups are designed to communicate is often referred to as a sector of the access network. In an embodiment, each antenna group is designed to communicate with an access terminal in a sector of the area covered by the access network 100.

[0042] In communication via forward links 120 and 126, the transmit antennas of access network 100 can utilize beamforming to improve the signal-to-noise ratio of the forward links used for different access terminals 116 and 122. Furthermore, compared to access networks that transmit to all their access terminals via a single antenna, access networks that use beamforming to transmit to access terminals randomly distributed within their coverage area cause less interference to access terminals in neighboring cells.

[0043] An access network (AN) can be a fixed station or base station used for communication with terminals, and may also be referred to as an access point, NodeB, base station, enhanced base station, evolved NodeB (eNB), network node, network, or any other term. An access terminal (AT) may also be referred to as a user equipment (UE), wireless communication device, terminal, access terminal, or any other term.

[0044] Figure 2 This is a simplified block diagram of an embodiment of the transmitter system 210 (also referred to as the access network) and receiver system 250 (also referred to as the access terminal (AT) or user equipment (UE)) in the MIMO system 200. At the transmitter system 210, service data for multiple data streams is provided from the data source 212 to the transmit (TX) data processor 214.

[0045] In one embodiment, each data stream is transmitted via a corresponding transmit antenna. The TX data processor 214 formats, decodes, and interleaves the service data for the data stream based on a specific decoding scheme selected for each data stream to provide decoded data.

[0046] OFDM technology can be used to multiplex the decoded data and pilot data for each data stream. 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. The multiplexed pilot data and decoded data for the data stream can then be modulated (i.e., symbol mapped) based on a specific modulation scheme (e.g., BPSK, QPSK, M-PK, or M-QAM) selected for each data stream to provide modulation symbols. The data rate, decoding, and modulation for each data stream can be determined by instructions executed by processor 230.

[0047] Next, modulation symbols for all data streams are provided to TX MIMO processor 220, which can further process the modulation symbols (e.g., for OFDM). Then, TX MIMO processor 220 will... T A modulation symbol stream is provided to N T Transmitters (TMTRs) 222a to 222t. In some embodiments, the TX MIMO processor 220 applies beamforming weights to symbols of the data stream and the antennas from which the symbols are transmitted.

[0048] 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., amplification, filtering, and up-conversion) to provide a modulated signal suitable for transmission over a MIMO channel. Then, from N... T Antennas 224a to 224t transmit N from transmitters 222a to 222t. T A modulated signal.

[0049] At receiver system 250, by N R Antennas 252a to 252r receive the transmitted modulated signal and provide the signal received from each antenna 252 to a corresponding receiver (RCVR) 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 a corresponding "received" symbol stream.

[0050] Next, the RX data processor 260 from N REach receiver 254 receives N R N symbol streams and process them based on specific receiver processing techniques. R Each received symbol stream provides N T Each detected symbol stream is then demodulated, deinterleaved, and decoded by the RX data processor 260 to recover the service data used 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.

[0051] Processor 270 periodically determines which pre-decoding matrix to use (discussed below). Processor 270 formulates a reverse link message including the matrix index part and the rank part.

[0052] 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 several 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.

[0053] 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. Next, processor 230 determines which pre-decoding matrix to use to determine beamforming weights and then processes the extracted message.

[0054] See also Figure 3 This figure illustrates an alternative simplified functional block diagram of a communication device according to an embodiment of the present invention. Figure 3 As shown, this can be achieved using the communication device 300 in a wireless communication system. Figure 1 UE (or AT) 116 and 122 or Figure 1The communication device 300 is a base station (or AN) 100, and the wireless communication system is preferably an NR system. The communication device 300 may include an input device 302, an output device 304, a control circuit 306, a central processing unit (CPU) 308, a memory 310, program code 312, and a transceiver 314. The control circuit 306 executes the program code 312 in the memory 310 via the CPU 308, thereby controlling the operation of the communication device 300. The communication device 300 can receive signals input by a 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. The communication device 300 in a wireless communication system can also be used for this purpose. Figure 1 AN 100 in the middle.

[0055] Figure 4 This is according to an embodiment of the present invention. Figure 3 The diagram shows a simplified block diagram of program code 312. In this embodiment, 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. Layer 3 portion 402 typically performs radio resource control. Layer 2 portion 404 typically performs link control. Layer 1 portion 406 typically performs physical connections.

[0056] 3GPP TS 23.304 introduced the following concepts:

[0057] 4.2.8 5G ProSe UE Inter-UE Relay Reference Architecture

[0058] Figure 4 Figure 2.8-1 illustrates a Layer 2 and Layer 3 5G ProSe UE-to-UE relay reference architecture. 5G ProSe UEs communicate with each other via the 5G ProSe UE-to-UE relay.

[0059] The name of 3GPP TS 23.304 V18.6.0 is "5G ProSe UE Inter-Relay Reference Architecture". Figure 4 .2.8-1 reproduced as Figure 5 ]

[0060] Each 5G ProSe end UE and 5G ProSe UE relay can have subscriptions from the same PLMN or different PLMNs.

[0061] [...]

[0062] 5.8.4 Identifiers used for 5G ProSe UE-to-UE relay discovery

[0063] 5.8.4.1 Overview

[0064] The 5G ProSe inter-UE relay discovery message contains two sets of identifiers: the direct discovery set and the inter-UE relay discovery set.

[0065] - The direct discovery identifier set is part of the content of the 5G ProSe direct discovery message, as defined in Clause 5.8.1. This identifier set provides information about the 5G ProSe end UE to be discovered via 5G ProSe UE-to-UE relay (e.g., user information (i.e., application layer ID)).

[0066] - The set of UE inter-relay discovery identifiers as defined in Clause 5.8.4.2 contains extended information supporting the discovery and direct discovery of 5G ProSe UE inter-relay.

[0067] 5G ProSe inter-UE relay should modify the inter-UE relay discovery identifier set and forward the direct discovery identifier set and the inter-UE relay discovery identifier set during the discovery procedure. According to TS 33.503

[29] , the direct discovery set can be protected using different keys used to protect the inter-UE relay discovery set.

[0068] 5.8.4.2 Common Identifiers for 5G ProSe Inter-UE Relay Discovery

[0069] The following parameters are used as the set of inter-UE relay discovery identifiers for the 5G ProSe inter-UE relay discovery notification message (Model A), where the source layer 2 ID and destination layer 2 ID are used for sending and receiving messages, and the user information ID and relay service code are included in the message:

[0070] - Source Layer 2 ID: The source layer 2 ID that 5G ProSe UE-to-UE relay automatically selects for the 5G ProSe UE-to-UE relay discovery notification message.

[0071] - Destination Layer 2 ID: Select the destination layer 2 ID for 5G ProSe UE-to-UE relay discovery notification messages based on the configuration described in Clause 5.1.5.1.

[0072] -5G ProSe UE Inter-Relay User Information ID: Provides information about 5G ProSe UE Inter-Relay.

[0073] - Relay Service Code: Information used to indicate the connectivity services provided by 5G ProSe UE-to-UE relay to 5G ProSe end UEs.

[0074] The following parameters are used as the set of inter-UE relay discovery identifiers for the 5G ProSe inter-UE relay discovery request message (Model B) between the discoverer 5G ProSe UE and the 5G ProSe inter-UE relay, where the source layer 2 ID and destination layer 2 ID are used to send and receive messages, and the user information ID and relay service code are included in the message:

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

[0076] - Destination Layer 2 ID: The destination layer 2 ID selected for 5G ProSe UE-to-UE relay discovery request messages based on the configuration described in Clause 5.1.5.1.

[0077] - Relay service code: Information about connectivity services that the discoverer 5G ProSe UE is interested in.

[0078] The following parameters are used as the set of UE inter-relay discovery identifiers in the 5G ProSe UE inter-relay discovery response message (Model B) between the discoverer 5G ProSe UE and the 5G ProSe UE inter-relay, where the source layer 2 ID and destination layer 2 ID are used for sending and receiving messages, and the user information ID and relay service code are included in the message:

[0079] - Source Layer 2 ID: The source layer 2 ID that 5G ProSe UE-to-UE relay automatically selects for the 5G ProSe UE-to-UE relay discovery response message.

[0080] - Destination Layer 2 ID: Set to the source Layer 2 ID of the received 5G ProSe UE-to-UE relay discovery request message.

[0081] -5G ProSe UE Inter-Relay User Information ID: Provides information about 5G ProSe UE Inter-Relay.

[0082] - Relay Service Code: Identifies the connectivity service provided by the 5G ProSe UE-to-UE relay to the 5G ProSe UE, and matches the relay service code from the corresponding discovery request message.

[0083] The following parameters are used as the set of inter-UE relay discovery identifiers for the 5G ProSe inter-UE relay discovery request message (Model B) between the 5G ProSe inter-UE relay and the discoverer 5G ProSe end UE, where the source layer 2 ID and destination layer 2 ID are used to send and receive messages, and the user information ID and relay service code are included in the message:

[0084] - Source Layer 2 ID: The source layer 2 ID that 5G ProSe UE-to-UE relay automatically selects for the 5G ProSe UE-to-UE relay discovery request message.

[0085] When a 5G ProSe inter-UE relay automatically selects the source layer 2 ID for a received 5G ProSe inter-UE relay discovery request message, it chooses a different source layer 2 ID value for each message. This allows the 5G ProSe inter-UE relay to associate the 5G ProSe inter-UE relay discovery response message with the 5G ProSe inter-UE relay discovery request message. The 5G ProSe inter-UE relay can then determine the discoverer 5G ProSe UE that triggered the 5G ProSe inter-UE relay discovery request based on the destination layer 2 ID of the received 5G ProSe inter-UE relay discovery response message.

[0086] - Destination Layer 2 ID: The destination layer 2 ID selected for 5G ProSe UE-to-UE relay discovery request messages based on the configuration described in Clause 5.1.5.1.

[0087] -5G ProSe UE Inter-Relay User Information ID: Provides information about 5G ProSe UE Inter-Relay.

[0088] - Relay Service Code: Identifies the connectivity service provided by 5G ProSe UE-to-UE relay to the 5G ProSe end UE.

[0089] The following parameters are used as the set of inter-UE relay discovery identifiers in the 5G ProSe inter-UE relay discovery response message (Model B) between the 5G ProSe inter-UE relay and the discoverer 5G ProSe end UE, where the source layer 2 ID and destination layer 2 ID are used for sending and receiving messages, and the user information ID and relay service code are included in the message:

[0090] - Source Layer 2 ID: The source layer 2 ID selected by the discoverer 5G ProSe UE for use in the 5G ProSe UE-to-UE relay discovery response message.

[0091] - Destination Layer 2 ID: Set to the source Layer 2 ID of the received 5G ProSe UE-to-UE relay discovery request message.

[0092] - Relay Service Code: Identifies the connectivity service provided by the 5G ProSe UE-to-UE relay to the 5G ProSe UE, and matches the relay service code from the corresponding discovery request message.

[0093] Note 1: The UE implementation scheme needs to ensure that when the UE selects its own source 2 ID, the self-selected source 2 ID is different between the 5G ProSe direct discovery (including 5G ProSe UE-to-network relay discovery and 5G ProSe UE-to-UE relay discovery) in Clause 6.3.2 and the 5G ProSe direct communication (including 5G ProSe UE-to-network relay communication and 5G ProSe UE-to-UE relay communication) in Clauses 6.4, 6.5 and 6.7, and is different from any other provisioned destination 2 ID as described in Clause 5.1 and any other self-selected source 2 ID used in 5G ProSe direct discovery (including 5G ProSe UE-to-network relay discovery and 5G ProSe UE-to-UE relay discovery) while having different discovery models.

[0094] Note 2: If a 5G ProSe UE relay and a 5G ProSe UE from a different PLMN discover each other, it means that the relay service code is associated with the same connectivity service and is provided based on the service level agreement between PLMNs.

[0095] 5.8.5 Identifiers for integrated 5G ProSe UE-to-UE relay communication

[0096] For the broadcast direct communication request message at the first hop PC5 reference point, the source layer 2 ID is selected by the source 5G ProSe UE, and the destination layer 2 ID is selected based on the configuration described in Clause 5.1.

[0097] For broadcast direct communication request messages at the second hop PC5 reference point, the source layer 2 ID is selected by the 5G ProSe UE inter-relay itself, and the destination layer 2 ID is selected based on the configuration described in Clause 5.1.

[0098] 5G ProSe UE-to-UE relay can send a unicast direct communication request message to the target 5G ProSe UE by setting the destination layer 2 ID using the unicast destination layer 2 ID of the received target 5G ProSe UE, as specified in Clause 6.4.3.7. The source layer 2 ID is selected by the 5G ProSe UE-to-UE relay itself.

[0099] For unicast direct communication message reception, the source layer 2 ID is selected by the target 5G ProSe UE or the relay between 5G ProSe UEs.

[0100] [...]

[0101] 6.3.2.4 5G ProSe UE Inter-Relay Discovery

[0102] 6.3.2.4.1 Overview

[0103] 5G ProSe UE-to-UE relay discovery applies to both 5G ProSe Layer 3 and Layer 2 UE-to-UE relay discovery for public safety use and commercial services. 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-equipped with the relevant information as described in Clause 5.1.

[0104] Relay Service Code (RSC) is used for 5G ProSe inter-UE relay discovery to indicate the connectivity services provided by the 5G ProSe inter-UE relay to the 5G ProSe end-UE. RSCs are pre-configured or pre-configured on both the 5G ProSe inter-UE relay and the 5G ProSe end-UE, as defined in Clause 5.1. The 5G ProSe inter-UE relay and the 5G ProSe end-UE determine whether the RSC provides 5G ProSe Layer 2 or Layer 3 inter-UE relay services based on the inter-UE relay layer indicator, as specified in Clause 5.1. 5G ProSe inter-UE relays supporting multiple RSCs announce the RSC using multiple discovery messages, one RSC per discovery message.

[0105] 6.3.2.4.2 Procedure for Relay Discovery between 5G ProSe UEs with Model A

[0106] Figure 6 Section 3.2.4.2-1 describes the procedure for discovery between 5G ProSe UEs with Model A.

[0107] The 3GPP TS 23.304 V18.6.0 specification is titled "5G ProSe UE Inter-Relay Discovery with Model A". Figure 6 .3.2.4.2-1 reproduced as Figure 6 ]

[0108] 1.5G ProSe UE-to-UE relay has discovered other nearby UEs and obtains a direct discovery set from other nearby UEs according to RSC. (e.g., via the previous 5G ProSe UE-to-UE relay or via a secure PC5 connection between a 5G ProSe end UE and a 5G ProSe U2U relay (refer to TS 33.503

[29] )).

[0109] 2.5G ProSe Inter-UE Relay Transmits an Inter-UE Relay Discovery Notification Message. The Inter-UE Relay Discovery Notification Message contains a discovery message type, the user information ID of the 5G ProSe Inter-UE Relay, RSC, and a direct discovery set, which contains a list of protected user information (i.e., application layer IDs) received from RSC-enabled 5G ProSe end UEs. The Inter-UE Relay Discovery Notification Message is transmitted using the source layer 2 ID and the destination layer 2 ID, as described in Clause 5.8.4.

[0110] 5G ProSe UE-to-UE relay should only notify user information (i.e., application layer ID) of other nearby UEs, and other nearby UEs should not include notification prohibition indication when they were previously discovered.

[0111] Note: 5G ProSe UE relay only notifies the direct discovery set of nearby UEs, as specified in TS 38.331

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

[0112] The 5G ProSe UE listens for notification messages from the 5G ProSe UE inter-relay. The 5G ProSe UE determines the destination layer 2 ID for signaling reception, as specified in Clause 5.1.

[0113] 6.3.2.4.3 Procedure for Relay Discovery between 5G ProSe UEs with Model B

[0114] Figure 6 Section 3.2.4.3-1 describes the procedure for relay discovery between 5G ProSe UEs with Model B.

[0115] The 3GPP TS 23.304 V18.6.0 specification is titled "5G ProSe UE Inter-Relay Discovery with Model B". Figure 6 .3.2.4.3-1 reproduced as Figure 7 ]

[0116] 1. The discoverer 5G ProSe UE (UE-1) sends a 5G ProSe Inter-UE Relay Discovery Request message. The 5G ProSe Inter-UE Relay Discovery Request message contains a discovery message type, an RSC, and a direct discovery set, which includes the protected user information (i.e., application layer IDs) of both the discoverer 5G ProSe UE (UE-1) and the discoverer 5G ProSe UE (UE-2). The 5G ProSe Inter-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.

[0117] The 5G ProSe UE-to-UE relay determines the destination layer 2 ID for signaling reception, as specified in Clause 5.1.

[0118] The discoverer 5G ProSe UE may include a notification prohibition indication in the UE inter-relay discovery request message. If a 5G ProSe UE inter-relay receives a relay discovery request message with a notification prohibition indication, it will not consider the 5G ProSe UE discovered during that procedure as included in the 5G ProSe UE inter-relay discovery with Model A, see Clause 6.3.2.4.2, Step 1.

[0119] 2. If the RSC contained in the request message matches any of the (pre)configured RSCs of the 5G ProSe UE-to-UE relay, as specified in Clause 5.1.5.1, the 5G ProSe UE-to-UE relay 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, a direct discovery set, the user information ID of the UE-to-UE relay, and an RSC. The direct discovery set contains a list of protected user information (i.e., application layer IDs) of the discoverer 5G ProSe UE (UE-1) and the discoverer 5G ProSe 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.

[0120] The 5G ProSe UE determines the destination layer 2 ID for signaling reception, as specified in Clause 5.1.

[0121] 5G ProSe UE-to-UE relays automatically select the source layer 2 ID, as specified in Clause 5.8.4.2.

[0122] 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)'s user information (i.e., application layer ID) matches the discoverer 5G ProSe UE (UE-2)'s user information (i.e., application layer ID) contained in the request message, then the discoverer 5G ProSe UE (UE-2) responds to the 5G ProSe UE-to-UE relay with a 5G ProSe UE-to-UE relay discovery response message. The 5G ProSe UE-to-UE relay discovery response message contains a discovery message type, an RSC, and a direct discovery set, which contains the protected user information (i.e., application layer ID) of both the discoverer 5G ProSe UE (UE-1) and the discoverer 5G ProSe UE (UE-2). The 5G ProSe UE-to-UE relay discovery response message is sent using the source layer 2 ID and the destination layer 2 ID, as described in Clause 5.8.4. If the discoverer 5G ProSe UE (UE-2) receives multiple UE relay discovery request messages with the same RSC and the discoverer 5G ProSe UE (UE-2) user information (i.e., application layer ID) from different 5G ProSe UE relays, 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 UE relay.

[0123] The discovered 5G ProSe UE may contain a notification prohibition indication in the UE inter-relay discovery response message. If a 5G ProSe UE inter-relay receives a relay discovery response message with a notification prohibition indication, it will not consider the 5G ProSe UE discovered during this procedure as included in the 5G ProSe UE inter-relay discovery with Model A, see Clause 6.3.2.4.2, Step 1.

[0124] 4.5G ProSe Inter-UE Relay Transmits a 5G ProSe Inter-UE Relay Discovery Response Message. The 5G ProSe Inter-UE Relay Discovery Response Message contains a discovery message type, the user information ID of the inter-UE relay, RSC, and a direct discovery set, which contains a list of protected user information (i.e., application layer IDs) of the discoverer 5G ProSe UE (UE-1) and the discoverer 5G ProSe UE (UE-2). The 5G ProSe Inter-UE Relay Discovery Response Message is transmitted using the source layer 2 ID and the destination layer 2 ID, as described in Clause 5.8.4.

[0125] 6.3.2.4.4 Candidate 5G ProSe UE Inter-Relay Discovery

[0126] When the discoverer UE discovers a candidate 5G ProSe UE-to-UE relay, this procedure for discovering the candidate 5G ProSe UE-to-UE relay supports negotiated relay reselection, as described in Clause 6.7.4.

[0127] The procedure for relay discovery between 5G ProSe UEs with Model B (see Clause 6.3.2.4.3) differs as follows:

[0128] - Step 1: In the 5G ProSe Inter-UE Relay Discovery Request message, the RSC and the user information ID of the candidate 5G ProSe Inter-UE Relay are included in the Inter-UE Relay Discovery set, but not in the Direct Discovery set. If the 5G ProSe end UE receives the Layer 2 ID of the candidate 5G ProSe Inter-UE Relay in the Link Modification Request message, it can set the Layer 2 ID of the candidate 5G ProSe Inter-UE Relay as the destination Layer 2 ID.

[0129] Note: The user information ID of the candidate 5G ProSe UE relay and the user information (i.e., the application layer ID) of the discovered 5G ProSe UE can be distinguished as different IEs in the message through 5G ProSe UE relay.

[0130] - Skip steps 2 and 3 because there is no direct discovery set, and the user information ID of the candidate 5G ProSe UE-to-UE relay in the received 5G ProSe UE-to-UE relay discovery request message matches the user information ID of the 5G ProSe UE-to-UE relay.

[0131] - Step 4: If the 5G ProSe Inter-UE Relay matches the user information ID of the candidate 5G ProSe Inter-UE Relay received in the 5G ProSe Inter-UE Relay Discovery Request, it sends a 5G ProSe Inter-UE Relay Discovery Response (with the RSC received in Step 1) and does not contain a direct discovery set.

[0132] [...]

[0133] 6.4.3 Unicast Mode 5G ProSe Direct Communication

[0134] 6.4.3.1 Establishment of Layer 2 Links at PC5 Reference Point

[0135] In order to perform unicast mode ProSe direct communication at the PC5 reference point, the UE is configured with the relevant information as described in Clause 5.1.3.

[0136] Figure 6Section 4.3.1-1 illustrates the Layer 2 link establishment procedure for unicast mode ProSe direct communication on the PC5 reference point.

[0137] The 3GPP TS 23.304 V18.6.0 specification is named "Layer 2 Link Establishment Procedure". Figure 6 4.3.1-1 reproduced as Figure 8 ]

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

[0139] 2. The ProSe application layer in UE-1 provides application information for PC5 unicast communication. This application information includes ProSe service information and the UE's application layer ID. The application information may also include the target UE's application layer ID.

[0140] The ProSe application layer in UE-1 provides the ProSe application requirements for this unicast communication. UE-1 determines the PC5 QoS parameters and PFI as specified in Clause 5.6.1.

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

[0142] 3. UE-1 sends a Direct Communication Request message to initiate a unicast Layer 2 link establishment procedure. The Direct Communication Request message includes:

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

[0144] - If the ProSe application layer provides the target UE's application layer ID in step 2, then the following information is included:

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

[0146] -ProSe service information: Information about the ProSe identifier used to establish the request layer 2 link.

[0147] - Security information: Information used to establish security.

[0148] Note 1: Security information and necessary protection of source user information and target user information are defined in TS 33.503

[29] .

[0149] Determine the source tier 2 ID and destination tier 2 ID used to send the direct communication request message, as specified in clauses 5.8.2.1 and 5.8.2.4. The destination tier 2 ID can be a broadcast or unicast tier 2 ID. When using a unicast tier 2 ID, the target user information will be included in the direct communication request message.

[0150] UE-1 uses the source layer 2 ID and destination layer 2 ID to send a direct communication request message via PC5 broadcast or unicast.

[0151] The default PC5 DRX configuration can be used to send and receive this message (see TS 38.300

[12] ).

[0152] 4. Establish security with UE-1 as follows:

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

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

[0155] Note 2: Signaling used for security procedures is defined in TS 33.503

[29] .

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

[0157] -If using IP communication:

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

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

[0160] - "IPv6 router", provided that only the IPv6 address allocation mechanism is supported by the initiating UE, i.e., it acts as an IPv6 router; or

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

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

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

[17] .

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

[0165] - Optional PC5 QoS rules.

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

[0167] Upon receiving the security establishment procedure message, UE-1 obtains the Layer 2 ID of the peer UE for signaling and data services used for this unicast link for future communication.

[0168] 5. The target UE that has successfully established security with UE-1 will directly communicate to receive messages sent to UE-1:

[0169] 5a. (Layer 2 Link Establishment for UE) If the direct communication request message contains target user information, the target UE (i.e., UE-2) responds with a direct communication accept message in the case of application layer ID matching for UE-2.

[0170] 5b. (Layer 2 Link Establishment for ProSe Services) If the direct communication request message does not contain target user information, then the UE interested in using the notified ProSe service ( Figure 6 UE-2 and UE-4 in .4.3.1-1 respond to requests by sending a direct communication receive message.

[0171] Direct communication message reception includes:

[0172] - Source User Information: The application layer ID of the UE that sent the direct communication message.

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

[0174] - Optional PC5 QoS rules.

[0175] -If using IP communication:

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

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

[0178] - "IPv6 router", provided that only the IPv6 address allocation mechanism is supported by the target UE, i.e., it acts as an IPv6 router; or

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

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

[0181] - Link-local IPv6 address: If the target UE does not support the IPv6 IP address allocation mechanism, i.e., the IP address configuration indicates "address allocation not supported" and UE-1 contains the link-local IPv6 address established in step 4, then a link-local IPv6 address is formed locally based on RFC4862

[17] . The target UE will contain a non-conflicting link-local IPv6 address.

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

[17] will be disabled for both UEs.

[0183] Note 3: When the initiating UE or the target UE indicates support for IPv6 routing, the corresponding address configuration procedure will be performed after the Layer 2 link is established, and the link-local IPv6 address will be ignored.

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

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

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

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

[0188] Alternatively, layer 2 ID information (i.e., source layer 2 ID and destination layer 2 ID) may be provided to the AS layer.

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

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

[0191] Note 5: PC5 unicast links are bidirectional, so UE-1's peer UE can send ProSe data to UE-1 through the unicast link with UE-1.

[0192] 6.4.3.2 Link Identifier Update for Unicast Links

[0193] Figure 6 Section 4.3.2-1 illustrates the link identifier update procedure for unicast links. When privacy requirements are configured for the ProSe identifier associated with a unicast link, the identifiers used for unicast mode 5G ProSe communication via the PC5 reference point (e.g., application layer ID, source layer 2 ID, and IP address / prefix) should change over time as specified in clauses 5.8.2.1 and 5.8.2.4. For other reasons, such as application layer requirements, the UE may decide to change the identifier. This procedure is used to update and exchange the new identifier between the source and peer UEs for the unicast link before using it, thereby avoiding service interruption. This procedure is performed over a security-protected unicast link when privacy requirements as noted above exist.

[0194] If a UE has multiple unicast links using the same application layer ID or layer 2 ID, the UE needs to execute the link identifier update procedure for each unicast link.

[0195] The 3GPP TS 23.304 V 18.6.0 specification is titled "Link Identifier Updater". Figure 6 4.3.2-1 Reproduced as Figure 9 ]

[0196] 0. UE-1 and UE-2 have unicast links established as described in Clause 6.4.3.1.

[0197] 1. For example, UE-1 decides to change its identifier due to a change in the application layer ID or after a timer expires. UE-1 generates its new layer 2 ID using the old identifier and sends a link identifier update request message to UE-2.

[0198] The Link Identifier Update Request message contains the new identifier to be used (including a new Layer 2 ID, security information, optionally a new Application Layer ID, and optionally a new IP address / prefix if IP communication is used). If security is configured for the unicast link, the new identifier should be encrypted to protect privacy. After sending the Link Identifier Update Request message, if UE-1 has data to send, UE-1 will continue to use the old identifier to send data services to UE-2 until UE-1 sends the Link Identifier Update Confirmation message to UE-2.

[0199] Note 1: The timer runs based on the source layer 2 ID.

[0200] Note 2: When one of the two UEs acts as an IPv6 router as described in Clause 5.5.1.1 and its IP address / prefix also needs to be changed, the corresponding address configuration procedure will be performed after the link identifier update procedure.

[0201] 2. Upon receiving a Link Identifier Update Request message, UE-2 changes its identifier. UE-2 responds with a Link Identifier Update Response message, which includes the new identifier to be used (containing a new Layer 2 ID, security information, optionally a new Application Layer ID, and optionally a new IP address / prefix if IP communication is used). If security is configured for the unicast link, the new identifier should be encrypted to protect privacy. The Link Identifier Update Response message is sent using the old identifier. UE-2 continues to receive services from UE-1 using the old Layer 2 ID until UE-2 receives services from UE-1 using the new Layer 2 ID. After sending the Link Identifier Update Response message, if UE-2 has data to send, UE-2 continues to send data services to UE-1 using the old identifier until UE-2 receives a Link Identifier Update Confirmation message from UE-1.

[0202] 3. Upon receiving the Link Identifier Update Response Message, UE-1 responds with a Link Identifier Update Confirmation Message. The Link Identifier Update Confirmation Message contains the new identifier received from UE-2 in the Link Identifier Update Response Message. The Link Identifier Update Confirmation Message is sent using the old identifier. UE-1 continues to receive services from UE-2 using the old Layer 2 ID until UE-1 receives services from UE-2 using the new Layer 2 ID.

[0203] 4. The ProSe layer of UE-1 passes the PC5 link identifier and the updated Layer 2 ID (i.e., the new Layer 2 ID for the source UE-1 and the new Layer 2 ID for the destination UE-2) down to the AS layer. This enables the AS layer to update the provided Layer 2 ID for the unicast link.

[0204] For this unicast link, UE-1 began using its new identifier, as did UE-2.

[0205] 5. Upon receiving the link identifier update confirmation message, the ProSe layer of UE-2 passes the PC5 link identifier used for unicast links and the updated Layer 2 ID (i.e., the new Layer 2 ID for the source UE-2 and the new Layer 2 ID for the destination UE-1) down to the AS layer. This enables the AS layer to update the provided Layer 2 IDs used for unicast links.

[0206] For this unicast link, UE-2 began using its new identifier, as well as UE-1's new identifier.

[0207] Note 3: The security information in the above message also needs to be updated simultaneously with the Layer 2 ID. This is defined in TS 33.503

[29] .

[0208] [...]

[0209] 6.4.3.4 Layer 2 Link Modification for Unicast Links

[0210] Figure 6 Section 4.3.4-1 illustrates a Layer 2 link modification procedure for unicast links. This procedure is used to:

[0211] - Add a new PC5 QoS stream to an existing PC5 unicast link.

[0212] This covers both adding new PC5 QoS streams to existing ProSe services and adding new PC5 QoS streams to new ProSe services.

[0213] - Modify existing PC5 QoS flows in existing PC5 unicast links.

[0214] - This covers cases where PC5 QoS parameters are modified for existing PC5 QoS flows.

[0215] This also covers cases where associated ProSe services are removed from existing PC5 QoS flows, as well as cases where new ProSe services are associated with existing PC5 QoS flows.

[0216] - Remove existing PC5 QoS flows from existing PC5 unicast links.

[0217] The title of 3GPP TS 23.304 V 18.6.0 is "Layer 2 Link Modification Procedure". Figure 6 .4.3.4-1 Reproduced as Figure 10 ]

[0218] 0. UE-1 and UE-2 have unicast links established as described in Clause 6.4.3.1.

[0219] 1. The ProSe application layer in UE-1 provides application information for PC5 unicast communication. This application information includes ProSe service information and the application layer ID of the initiating UE. The application information may also include the application layer ID of the target UE. If UE-1 decides to reuse an existing PC5 unicast link as specified in Clause 5.3.4, and therefore decides to modify the unicast link established with UE-2, UE-1 sends a link modification request to UE-2.

[0220] The link modification request message includes:

[0221] a) Add a new PC5 QoS stream to an existing PC5 unicast link:

[0222] - QoS Information: Information about the PC5 QoS flow to be added. For each PC5 QoS flow, the PFI, the corresponding PC5 QoS parameter (i.e., PQI and conditionally other parameters such as MFBR / GFBR), and optionally the associated ProSe identifier.

[0223] - Optional PC5 QoS rules.

[0224] b) Modify the PC5 QoS flow in the existing PC5 unicast link:

[0225] - QoS Information: Information about the PC5 QoS flow to be modified. For each PC5 QoS flow, this includes the PFI, the corresponding PC5 QoS parameter (i.e., PQI and conditionally other parameters such as MFBR / GFBR), and optionally the associated ProSe identifier.

[0226] - Optional PC5 QoS rules.

[0227] c) Modify the PC5 QoS flow in the existing PC5 unicast link:

[0228] -PFI.

[0229] 2. UE-2 responds with a link modification receive message.

[0230] The link modification acceptance message includes:

[0231] -For cases a) and b) described in step 1:

[0232] - QoS Information: Information about the PC5 QoS flows requested by UE-1. For each PC5 QoS flow, the PFI, the corresponding PC5 QoS parameters (i.e., PQI and conditionally other parameters such as MFBR / GFBR), and optionally the associated ProSe identifier.

[0233] - Optional PC5 QoS rules.

[0234] The ProSe layer of each UE provides information about unicast link modifications to the AS layer. This enables the AS layer to update the context associated with the modified unicast link.

[0235] [...]

[0236] 6.4.3.7 Layer 2 Link Management on the PC5 Reference Point for 5G ProSe Inter-UE Relay

[0237] 6.4.3.7.1 Common components of Layer 2 link management on the PC5 reference point for 5G ProSe UE-to-UE relay

[0238] For 5G ProSe communication via 5G ProSe UE-to-UE relay as described in Clauses 6.7.1 and 6.7.2:

[0239] -The direct communication request message on the first hop PC5 reference point contains:

[0240] - User information of the source 5G ProSe UE (i.e., application layer ID): Identifier of the source 5G ProSe UE requesting relay operation.

[0241] -5G ProSe Inter-UE Relay User Information ID: Provides an identifier for the inter-UE relay to the source 5G ProSe UE during the 5G ProSe Inter-UE Relay discovery process.

[0242] - User information of the target 5G ProSe UE (i.e., application layer ID): The identifier of the target 5G ProSe UE provided during the inter-UE relay discovery procedure to the source 5G ProSe UE.

[0243] - (Optional) Destination Layer 2 ID of the target 5G ProSe UE: The unicast destination Layer 2 ID of the target 5G ProSe UE determined by the source 5G ProSe UE, as specified in Clause 5.8.2.4.

[0244] -ProSe service information: Information about the ProSe identifier used to establish the request layer 2 link.

[0245] -RSC: Connectivity service requested by the source 5G ProSe UE from the 5G ProSe UE-to-UE relay.

[0246] - Security information: Security information used to establish the first hop PC5 link (see TS 33.503

[29] ).

[0247] The direct communication request message on the second hop PC5 reference point includes:

[0248] - User information of the source 5G ProSe terminal UE (i.e., application layer ID).

[0249] - User information (i.e., application layer ID) of the target 5G ProSe terminal UE.

[0250] -5G ProSe UE-to-UE relay user information ID.

[0251] -ProSe service information: Information about the ProSe identifier.

[0252] -RSC: Connectivity service requested by the source 5G ProSe UE from the 5G ProSe UE-to-UE relay.

[0253] - Security information: Information used to establish the security of the second-hop PC5 link (see TS 33.503

[29] ).

[0254] The direct communication received message at the second-hop PC5 reference point includes:

[0255] - User information (i.e., application layer ID) of the target 5G ProSe terminal UE.

[0256] The direct communication received message at the first hop PC5 reference point includes:

[0257] - User information (i.e., application layer ID) of the target 5G ProSe terminal UE.

[0258] -5G ProSe UE-to-UE relay user information ID.

[0259] The link modification request message on the first hop PC5 reference point includes:

[0260] - User information of the target 5G ProSe UE (i.e., application layer ID): The identifier of the target 5G ProSe UE provided during the inter-UE relay discovery procedure to the source 5G ProSe UE.

[0261] - (Optional) Destination Layer 2 ID of the target 5G ProSe UE: The unicast destination Layer 2 ID of the target 5G ProSe UE determined by the source 5G ProSe UE, as specified in Clause 5.8.2.4.

[0262] The link modification request message on the second hop PC5 reference point includes:

[0263] - User information of the source 5G ProSe terminal UE (i.e., application layer ID).

[0264] - User information (i.e., application layer ID) of the target 5G ProSe terminal UE.

[0265] The link modification acceptance message on the second hop PC5 reference point includes:

[0266] - User information (i.e., application layer ID) of the target 5G ProSe terminal UE.

[0267] The link modification acceptance message on the first hop PC5 reference point includes:

[0268] - User information (i.e., application layer ID) of the target 5G ProSe terminal UE.

[0269] 6.4.3.7.2 Layer 2 Link Management on PC5 Reference Point for 5G ProSe Layer 2 UE Inter-UE Relay

[0270] For 5G ProSe communication via 5G ProSe layer 2 UE relay as described in Clause 6.7.2, the description in Clause 6.4.3.7.1 applies:

[0271] The message content on the PC5 reference point for unicast mode 5G ProSe direct communication described in Clauses 6.4.3.1 to 6.4.3.5 is the same for end-to-end connections between peer 5G ProSe UEs.

[0272] 6.4.3.7.3 Layer 2 Link Management on PC5 Reference Point for 5G ProSe Layer 3 UE Inter-UE Relay

[0273] For 5G ProSe communication via 5G ProSe layer 3UE relay as described in Clause 6.7.1, the description in Clause 6.4.3.7.1 applies, but with the following differences and interpretations:

[0274] - In the security procedure at the first hop PC5 reference point, the source 5G ProSe Layer 3 UE provides its IP address configuration or link-local IPv6 address and end-to-end QoS information to the 5G ProSe Layer 3 UE inter-relay. If the PC5 link is used to transmit Ethernet services, the source 5G ProSe Layer 3 UE provides its Ethernet MAC address instead of IP-related information.

[0275] - In the security procedures at the second-hop PC5 reference point, the 5G ProSe Layer 3 UE-to-UE relay provides the IP address configuration or link-local IPv6 address and the QoS information of the second-hop QoS to the target 5G ProSe end UE. If the PC5 link is used to transmit Ethernet services, the 5G ProSe Layer 3 UE-to-UE relay provides the Ethernet MAC address of the source 5G ProSe Layer 3 end UE instead of IP-related information.

[0276] - The direct communication receive message on the second-hop PC5 reference point also includes IP address configuration or link-local IPv6 address and QoS information for the second-hop QoS. If the PC5 link is used to transmit Ethernet services, the target 5G ProSe Layer 3 UE provides its Ethernet MAC address instead of IP-related information.

[0277] - 5G ProSe Layer 3 UE-to-UE relay determines the QoS information of the first hop by considering the received second-hop QoS. The direct communication received message on the first-hop PC5 reference point also includes the IP address configuration or link-local IPv6 address, the QoS information of the first hop QoS, and may include the IP address of the target 5G ProSe UE. If the PC5 link is used to transmit Ethernet services, the 5G ProSe Layer 3 UE-to-UE relay provides the Ethernet MAC address of the target 5G ProSe Layer 3 UE instead of IP-related information.

[0278] - To add a new end-to-end QoS flow or modify an existing end-to-end QoS flow, the source 5G ProSe UE additionally includes end-to-end QoS information in the link modification request message at the first-hop PC5 reference point, as described in Clause 6.4.3.4. To remove an end-to-end QoS flow, the source 5G ProSe UE includes the PFI of the first-hop QoS flow in the link modification request message at the first-hop PC5 reference point, as described in Clause 6.4.3.4. If the PC5 link is used to transmit Ethernet services, the source 5G ProSe Layer 3 UE can provide its Ethernet MAC address.

[0279] To add a new end-to-end QoS flow or modify an existing end-to-end QoS flow, the 5G ProSe Layer 3 UE-to-UE relay in the link modification request message at the second-hop PC5 reference point additionally includes the second-hop QoS information for the target 5G ProSe end UE. To remove an end-to-end QoS flow, the 5G ProSe Layer 3 UE-to-UE relay in the link modification request message at the second-hop PC5 reference point includes the PFI of the second-hop QoS flow. If the PC5 link is used to transmit Ethernet services, the 5G ProSe Layer 3 UE-to-UE relay provides the Ethernet MAC address of the source 5G ProSe Layer 3 end UE.

[0280] - To add new end-to-end QoS flows or modify existing end-to-end QoS flows, the link modification accept message at the second-hop PC5 reference point additionally includes QoS information for the second-hop QoS. If the PC5 link is used to transmit Ethernet services, the target 5G ProSe layer 3 UE can provide its Ethernet MAC address.

[0281] To add new end-to-end QoS flows or modify existing end-to-end QoS flows, the 5G ProSe Layer 3 UE-to-UE relay determines the QoS information of the first hop by considering the received second-hop QoS. The link modification receive message at the first-hop PC5 reference point also contains the first-hop QoS information and may include the IP address of the target 5G ProSe end UE. If the PC5 link is used to transmit Ethernet services, the 5G ProSe Layer 3 UE-to-UE relay provides the Ethernet MAC address of the target 5G ProSe Layer 3 end UE instead of IP-related information.

[0282] When the PC5 link between a 5G ProSe layer 3 UE and a 5G ProSe layer 3 UE relay is released, the 5G ProSe layer 3 UE relay can initiate the release of the PC5 link to the peer 5G ProSe layer 3 UE, or notify the peer 5G ProSe layer 3 UE that the peer PC5 link has been released.

[0283] 6.4.3.7.4 Layer 2 Link Management on PC5 Reference Point for Integrated Discovery-based 5G ProSe UE-to-UE Relay Communication

[0284] This clause applies to 5G ProSe UE-to-UE relay communication with integrated discovery procedures, as described in Clause 6.7.3.

[0285] The direct communication request message on the first hop PC5 reference point includes:

[0286] - User information of the source 5G ProSe terminal UE (i.e., application layer ID).

[0287] - (Optional) Target 5G ProSe UE User Information ID (i.e., Application Layer ID): Identifier of the target 5G ProSe UE (if provided from the ProSe application layer).

[0288] - (Optional) Destination Layer 2 ID of the target 5G ProSe UE: The unicast destination Layer 2 ID of the target 5G ProSe UE determined by the source 5G ProSe UE, as specified in Clause 5.8.2.4.

[0289] -ProSe service information: Information about the ProSe identifier used to establish the request layer 2 link.

[0290] -RSC: Connectivity service requested by the source 5G ProSe UE from the 5G ProSe UE-to-UE relay.

[0291] -Relay_indication: Indicates whether the direct communication request message can be relayed between 5G ProSe UEs.

[0292] - Security information: Security information used to establish the first hop PC5 link (see TS 33.503

[29] ).

[0293] The direct communication request message on the second hop PC5 reference point includes:

[0294] - User information of the source 5G ProSe terminal UE (i.e., application layer ID).

[0295] -5G ProSe UE-to-UE relay user information ID.

[0296] - (Optional) User information for the target 5G ProSe end UE.

[0297] -ProSe service information: Information about the ProSe identifier.

[0298] -RSC: Connectivity service requested by the source 5G ProSe UE from the 5G ProSe UE-to-UE relay.

[0299] - Security information: Information used to establish the security of the second-hop PC5 link (see TS 33.503

[29] ).

[0300] The direct communication received message at the second-hop PC5 reference point includes:

[0301] - User information (i.e., application layer ID) of the target 5G ProSe terminal UE.

[0302] The direct communication received message at the first hop PC5 reference point includes:

[0303] - User information (i.e., application layer ID) of the target 5G ProSe terminal UE.

[0304] -5G ProSe UE-to-UE relay user information ID.

[0305] The following further clarifies the 5G ProSe communication relayed between 3 UEs via the 5G ProSe layer:

[0306] - In the security procedure at the second hop PC5 reference point, the 5G ProSe layer 3 UE inter-relay provides the IP address configuration or link-local IPv6 address to the target 5G ProSe end UE.

[0307] - The direct communication accept message at the second-hop PC5 reference point also includes the IP address configuration or link-local IPv6 address (if IP communication is used) and the Ethernet MAC address of the target 5G ProSe UE (if Ethernet communication is used). QoS information is not included in the security procedures or direct communication accept message at the second-hop PC5 reference point.

[0308] - In the security procedure at the first hop PC5 reference point, the source 5G ProSe UE provides IP address configuration, link-local IPv6 address, and end-to-end QoS information to the 5G ProSe layer 3 UE inter-relay.

[0309] -5G ProSe Layer 3 UE inter-relay uses Layer 2 link modification to provide the second-hop QoS information to the target 5G ProSe end UE, as described in Clause 6.4.3.4.

[0310] -5G ProSe Layer 3 UE relay determines the QoS information of the first hop QoS by considering the second hop QoS received from the target 5G ProSe UE. The direct communication receive message on the first hop PC5 reference point also includes the IP address configuration or link-local IPv6 address, the QoS information of the first hop QoS, and may include the IP address of the target 5G ProSe UE (if using IP communication) or the Ethernet MAC address of the target 5G ProSe UE (if using Ethernet communication).

[0311] For 5G ProSe communication via 5G ProSe layer 2 UE relay, the message content on the PC5 reference point for unicast mode 5G ProSe direct communication described in Clauses 6.4.3.1 to 6.4.3.5 is the same for end-to-end connections between peer 5G ProSe end UEs.

[0312] [...]

[0313] 6.7 5G ProSe UE-to-UE Relay Communication

[0314] 6.7.1 5G ProSe Communication via 5G ProSe Layer Inter-UE Relay

[0315] 6.7.1.1 Layer 2 Link Establishment for PC5 Communication via 5G ProSe Layer 3 UE Inter-UE Relay

[0316] Figure 6 .7.1.1-1 illustrates the procedure for establishing a Layer 2 link via 5G ProSe Layer 3 UE relay.

[0317] The 3GPP TS 23.304 V 18.6.0 standard is titled "Establishment of Layer 2 Links via 5G ProSe Layer 3 UE Inter-UE Relay". Figure 6 .7.1.1-1 reproduced as Figure 11 ]

[0318] 1. Perform service authorization and provisioning for the source 5G ProSe Layer 3 UE, the target 5G ProSe Layer 3 UE, and the relay between 5G ProSe Layer 3 UEs, as described in Clause 6.2.

[0319] 2. The source 5G ProSe layer 3 end UE performs the discovery of 5G ProSe layer 3 UE inter-UE relay, as described in clause 6.3.2.4.

[0320] 3. The source 5G ProSe Layer 3 UE sends a direct communication request message to initiate a unicast Layer 2 link establishment procedure utilizing 5G ProSe Layer 3 UE-to-UE relay. The parameters included in the direct communication request message are described in Clause 6.4.3.7.

[0321] The source layer 2 ID of the direct communication request message is assigned by the source 5G ProSe layer 3 UE, and the destination layer 2 ID is set to the source layer 2 ID of the discovery message for 5G ProSe layer 3 UE inter-UE relay.

[0322] The 5G ProSe layer 3 UE obtains application information and optional ProSe application requirements from the ProSe application layer and determines end-to-end QoS parameters as described in Clause 5.6.3.1.

[0323] 4. If the user information ID of the 5G ProSe Layer 3 UE-to-UE relay in the direct communication request message matches the user information ID of the 5G ProSe Layer 3 UE-to-UE relay, and the RSC in the direct communication request matches one of the (pre-)configured RSCs of the relay, as specified in Clause 5.1.5.1, then the 5G ProSe Layer 3 UE-to-UE 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-to-UE relay.

[0324] If the Ethernet MAC address of the source 5G ProSe Layer 3 UE is already in use 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.

[0325] The source layer 2 ID used for the security establishment procedure 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.

[0326] 5G ProSe Layer 3 UE inter-relay will select different source layer 2 IDs for PC5 links for different types of services (i.e., IP services, Ethernet services, and unstructured services).

[0327] If the PC5 link is used to transmit unstructured services, the 5G ProSe layer 3 UE relay will select different source layer 2 IDs for different pairs of source and target 5G ProSe layer 3 end UEs.

[0328] Upon receiving the security establishment procedure message, the source 5G ProSe Layer 3 UE obtains the Layer 2 ID for 5G ProSe Layer 3 UE relay for signaling and data services used for this unicast link for future communication.

[0329] 5. After the security establishment procedure in step 4 is completed, the 5G ProSe Layer 3 UE inter-relay determines whether to use its existing unicast Layer 2 link with the target 5G ProSe UE for the required service. If no existing unicast Layer 2 link exists 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 the unicast Layer 2 link establishment procedure 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.

[0330] 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 either a broadcast or unicast layer 2 ID. The unicast layer 2 ID is used only if the layer 2 ID of the target 5G ProSe layer 3 end UE associated with the user information (i.e., the application layer ID) is known to the 5G ProSe layer 3 UE inter-relay.

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

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

[0333] 6. If the RSC contained in the direct communication request matches the RSC of the target UE (pre-)configured as specified in Clause 5.1.5.1, and if the user information contained in the direct communication request matches the user information of the target UE, 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 parameters as described in Clause 6.4.3.7 to the target 5G ProSe Layer 3 UE.

[0334] The source layer 2 ID used for the security establishment procedure is assigned by the target 5G ProSe layer 3 UE, and the destination layer 2 ID is set to the source layer 2 ID of the received direct communication request message.

[0335] Upon receiving the security establishment procedure 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 used for this unicast link for future communication.

[0336] 7. The target 5G ProSe Layer 3 UE sends a direct communication accept message to the 5G ProSe Layer 3 UE with which it has successfully established security. The parameters contained in the direct communication accept message are described in Clause 6.4.3.7.

[0337] Note: When a 5G ProSe Layer 3 UE relay receives a direct communication accept message, it can detect that the Ethernet MAC address of the target 5G ProSe Layer 3 UE has been used by another 5G ProSe Layer 3 UE.

[0338] 8. For IP services, assign an IPv6 prefix or IPv4 address to the target 5G ProSe Layer 3 UE as defined in Clause 5.5.1.4.

[0339] 9. After receiving a direct communication accept message from the target 5G ProSe Layer 3 UE, the 5G ProSe Layer 3 UE relay sends a 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.

[0340] 10. For IP services, assign an IPv6 prefix or IPv4 address to the source 5G ProSe Layer 3 UE as defined in Clause 5.5.1.4.

[0341] 11. For IP communication, the 5G ProSe Layer 3 UE inter-relay can store the association between user information (i.e., application layer 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 transmit the IP address of the target 5G ProSe Layer 3 UE back to the source 5G ProSe Layer 3 UE.

[0342] 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 UE.

[0343] For unstructured service communication, for each pair of source and target 5G ProSe layer 3 UEs, the 5G ProSe layer 3 UE relay maintains a 1:1 mapping between the PC5 link and the source 5G ProSe layer 3 UE, as well as between the PC5 link and the target 5G ProSe layer 3 UE.

[0344] 12. The source 5G ProSe layer 3 UE communicates with the target 5G ProSe layer 3 UE via 5G ProSe layer 3 UE relay.

[0345] In the scenario where a source 5G ProSe Layer 3 UE communicates with multiple target 5G ProSe Layer 3 UEs, according to the RSC, the PC5 link between the source 5G ProSe Layer 3 UE and the inter-UE relay can be shared among the multiple target 5G ProSe Layer 3 UEs. Simultaneously, according to the RSC, the PC5 link can be established individually between the inter-UE relay and the target 5G ProSe Layer 3 UEs. For shared PC5 links, a Layer 2 link modification procedure should be used to replace... Figure 6 Steps 3 to 4 and 9 to 10 of the procedure in .7.1.1-1. The parameters used in the Layer 2 link modification procedure are described in Clause 6.4.3.7.

[0346] In situations where multiple source 5G ProSe Layer 3 UEs communicate with a single target 5G ProSe Layer 3 UE, according to the RSC, the PC5 link between the 5G ProSe Layer 3 UE inter-relay and the target 5G ProSe Layer 3 UE can be shared. Simultaneously, according to the RSC, the PC5 link can be established individually between the source 5G ProSe Layer 3 UEs and the 5G ProSe Layer 3 UE inter-relay. For shared PC5 links, a Layer 2 link modification procedure should be used to replace... Figure 6 Steps 5 to 8 of the procedure in .7.1.1-1. The parameters used in the Layer 2 link modification procedure are described in Clause 6.4.3.7.

[0347] 6.7.1.2 Link Identifier Update for PC5 Communication via 5G ProSe Layer 3 UE Inter-UE Relay

[0348] The link identifier update procedure as defined in Clause 6.4.3.2 is repeatedly used between the source 5G ProSe Layer 3 UE and the relay between the 5G ProSe Layer 3 UE to perform the link identifier update. When the IP address / prefix changes, the new IP address / prefix is ​​shared between the source 5G ProSe Layer 3 UE and the target 5G ProSe Layer 3 UE, as follows: Figure 6 As described in .7.1.2-1.

[0349] The title of 3GPP TS 23.304 V 18.6.0 is "Link Identifier Update and IP Address / Prefix Sharing via 5G ProSe Layer 3UE Inter-UE Relay". Figure 6 .7.1.2-1 reproduced as Figure 12 ]

[0350] 0. Establish a PC5 link between the source 5G ProSe Layer 3 UE (i.e., UE1) and the 5G ProSe Layer 3 UE-to-UE relay (i.e., UE-to-UE relay). Establish another PC5 link between the UE-to-UE relay and the target 5G ProSe Layer 3 UE (i.e., UE2). IP data can be exchanged between UE1 and UE2 via the UE-to-UE relay on the PC5 link. During link establishment, UE1 notifies the UE-to-UE relay that the link requires privacy.

[0351] 1. As described in Clause 6.4.3.2, UE1 may trigger a link identifier update procedure for privacy requirements. UE1 sends a link identifier update request message to the inter-UE relay containing the following parameters:

[0352] - UE1's new Layer 2 ID, new security information, and new application layer ID (if provided by the upper layer).

[0353] -If UE1's IP address / prefix needs to be changed:

[0354] - If the IP address / prefix of UE1 is assigned by an inter-UE relay, then UE1 contains a "New IP address required" indication.

[0355] - If UE1 assigns its own IP address / prefix, then UE1 includes its new IP address / prefix.

[0356] - Information about the peer UE of UE1 (e.g., the IP address of UE2, the application layer ID of UE2), so that the inter-UE relay can notify the peer UE of UE1 (e.g., UE2) of the newly assigned IP address / prefix of UE1.

[0357] 2. The UE-to-UE relay automatically assigns a new L2 ID, new security information, and a possible new IP address / prefix for the PC5 link with UE1.

[0358] a. If a "new IP address required" instruction is received, the UE-to-UE relay assigns a new IP address / prefix to UE1 and saves it locally.

[0359] Based on the information of the peer UE, the inter-UE relay then sends a PC5 relay update request message to each peer UE (e.g., UE2) containing: UE1's old IP address / prefix, UE1's old and new application layer IDs, and UE1's new IP address / prefix.

[0360] 3. UE2 receives the PC5 trunk update request message and saves UE1's new IP address / prefix. UE2 sends a PC5 trunk update response message to the inter-UE trunk, containing all the parameters received in the PC5 trunk update request message.

[0361] UE2 continues to receive IP data with UE1's old IP address (transfer packets sent before UE1 receives its new IP address) until it receives IP packets using UE1's new IP address. At this point, UE2 starts using UE1's new IP address and can ignore UE1's old IP address.

[0362] 4. The UE-to-UE relay sends a link identifier update response message to UE1, which includes UE1's new IP address / prefix, the UE-to-UE relay's new Layer 2 ID, new security information, and possibly a new IP address / prefix and / or a new application layer ID.

[0363] 5. UE1 saves its new IP address / prefix and the new parameters of the inter-UE relay, and sends a Link Identifier Update ACK message to the inter-UE relay, containing its new IP address received in the Link Identifier Update Response message. UE1 and the inter-UE relay begin using the new Layer 2 ID and new security information for PC5 communication. UE1 begins using its new IP address for IP data exchange with UE2.

[0364] [...]

[0365] 6.7.1.4 Layer 2 Link Modification for PC5 Communication via 5G ProSe Layer 3 UE Inter-UE Relay

[0366] Figure 6 Section 7.1.4-1 illustrates a procedure for modifying a Layer 2 link via Layer 3 inter-UE relay. This procedure is used to add / modify / remove PC5 QoS flows in an existing PC5 unicast link, as described in Clause 6.4.3.7.3.

[0367] The 3GPP TS 23.304 V 18.6.0 standard is titled "Layer 2 Link Modification Procedure via Layer 3 UE Inter-Relay". Figure 6 .7.1.4-1 reproduced as Figure 13 ]

[0368] 0. UE-1 and UE-inter-relay, as well as UE-inter-relay and UE-2, have unicast links established as described in Clause 6.7.1.1.

[0369] 1. UE-1 sends a link modification request to the inter-UE relay, as described in Clause 6.4.3.7.3.

[0370] 2. After receiving the link modification request message from UE-1, the inter-UE relay sends the link modification request to UE-2 as described in Clause 6.4.3.7.3.

[0371] 3. UE-2 responds to inter-UE relay with a link modification accept message, as described in Clause 6.4.3.7.3.

[0372] 4. After receiving a link modification accept message from UE-2, the inter-UE relay responds to UE-1 with a link modification accept message as described in Clause 6.4.3.7.3.

[0373] [...]

[0374] 6.7.2 5G ProSe Communication via 5G ProSe Layer 2 UE Inter-UE Relay

[0375] This procedure is applicable to 5G ProSe layer 2UE inter-relay.

[0376] The 3GPP TS 23.304 V 18.6.0 standard is titled "5G ProSe Communication via 5G ProSe Layer 2 UE Inter-UE Relay". Figure 6 .7.2-1 reproduced as Figure 14 ]

[0377] Prior to this procedure, service authorization and provisioning had been performed for 5G ProSe layer 2 UE inter-relay and 5G ProSe end UE, as described in Clause 6.2.

[0378] 1. Perform 5G ProSe UE inter-relay discovery as described in Clause 6.3.2.4, and the source 5G ProSe UE selects an appropriate 5G ProSe Layer 2 UE inter-relay for communication with the target 5G ProSe UE.

[0379] 2. The source 5G ProSe UE decides whether to use the existing PC5 link for inter-UE relay to obtain the required service. If the existing PC5 link is used, the Layer 2 link modification procedure as specified in Clause 6.4.3.7 is used for inter-UE relay; otherwise, the Layer 2 link establishment procedure is used for inter-UE relay.

[0380] This procedure targets selected 5G ProSe UE-to-UE relays and, for Layer 2 link establishment, performs security establishment before initiating step 3.

[0381] Note: The source 5G ProSe layer 2 end UE will not initiate any layer 2 link establishment or layer 2 link modification procedures for different target 5G ProSe layer 2 end UEs for the same 5G ProSe layer 2 UE inter-relay, unless the current layer 2 link establishment or layer 2 link modification procedure has been completed, including receiving a PC5-RRC message from the 5G ProSe layer 2 UE inter-relay, as specified in TS 38.300

[12] . Therefore, the source 5G ProSe layer 2 end UE can identify the target 5G ProSe layer 2 end UE with the layer 2 ID provided by the 5G ProSe layer 2 UE inter-relay.

[0382] 3.5G ProSe Layer 2 UE Inter-Relay determines whether to use the existing PC5 link between the 5G ProSe UE Inter-Relay and the target 5G ProSe UE to obtain the required service, and initiates a 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.

[0383] If a Layer 2 link establishment procedure is performed for a target 5G ProSe UE, the broadcast or unicast Layer 2 ID is used as the destination Layer 2 ID. When the Layer 2 ID of the target 5G ProSe Layer 2 UE associated with the user information (i.e., application layer ID) of the target 5G ProSe Layer 2 UE is known for 5G ProSe Layer 2 UE inter-relay, the unicast Layer 2 ID is used.

[0384] If a Layer 2 link modification procedure is executed for the target 5G ProSe UE, the procedure uses the unicast Layer 2 ID of the target 5G ProSe UE as the destination Layer 2 ID.

[0385] After step 3 is completed, the 5G ProSe layer 2 UE inter-relay sends a direct communication accept message or a link modification accept message to the source 5G ProSe UE.

[0386] 4. The source 5G ProSe UE and the target 5G ProSe UE establish an end-to-end connection for unicast mode communication, as described in Clause 6.4.3.7.

[0387] Data and end-to-end PC5-S signaling are transmitted between the source 5G ProSe UE and the target 5G ProSe UE via 5G ProSe Layer 2 UE relay. The 5G ProSe Layer 2 UE relay forwards all data services and end-to-end PC5-S signaling between the source 5G ProSe UE and the target 5G ProSe UE as specified in TS 38.300

[12] .

[0388] 6.7.3 Integrated 5G ProSe UE-to-UE relay communication with discovery functionality

[0389] 6.7.3.1 Overview

[0390] Supports 5G ProSe communication via 5G ProSe UE-to-UE relay with integrated discovery.

[0391] For 5G ProSe inter-UE relay communication with integrated discovery, when a UE allows an inter-UE relay to participate in a direct communication request to another UE, the UE indicates the inter-UE relay by including relay_indication in the broadcast direct communication request message.

[0392] When an inter-UE relay receives a direct communication request containing relay_indication, it decides whether to forward the message based on factors such as the relay service code (if any), application ID, operator policy for each relay service code, signal strength, and local policy.

[0393] 6.7.3.2 Procedure for communication via Layer 3 UE inter-relay

[0394] The 3GPP TS 23.304 V 18.6.0 standard is titled "Integrated Discovery 5G ProSe UE Inter-Relay Communication via Layer 3 UE Inter-Relay". Figure 6 7.3.2-1 reproduced as Figure 15 ]

[0395] The 0.5G ProSe UE is authorized and pre-configured with parameters to use the services provided by 5G ProSe UE-to-UE relay. 5G ProSe UE-to-UE relay is authorized and pre-configured with parameters to provide relay services among 5G ProSe UEs.

[0396] 1. A source 5G ProSe UE (i.e., UE-1) wants to establish unicast communication with a target 5G ProSe UE (i.e., UE-2) and broadcasts a direct communication request. The parameters contained in the direct communication request message are described in Clause 6.4.3.7.

[0397] The relay_indication in the direct communication request is used to indicate whether the 5G ProSe inter-UE relay can forward the direct communication request message. It is also used to limit the hop count of the 5G ProSe inter-UE relay by removing the relay_indication from the direct communication request message from the 5G ProSe inter-UE relay.

[0398] The source layer 2 ID and destination layer 2 ID used for direct communication request messages are defined in clause 5.8.5.

[0399] The source 5G ProSe end UE obtains application information and optional ProSe application requirements from the ProSe application layer and determines end-to-end QoS parameters as described in Clause 5.6.3.1.

[0400] Note 1: The data type of relay_indication can be determined in stage 3.

[0401] 2. When a direct communication request with relay_indication is received from UE-1, the 5G ProSe inter-UE relays (i.e., relay-1 and relay-2) may decide to participate in the procedure and broadcast a direct communication request message in their vicinity without relay_indication. The parameters contained in the direct communication request message are described in Clause 6.4.3.7.

[0402] The source layer 2 ID and destination layer 2 ID used for direct communication request messages are defined in clause 5.8.5.

[0403] 3. When UE-2 receives a direct communication request from one or more 5G ProSe inter-UE relays, UE-2 selects the 5G ProSe inter-UE relay to which UE-2 will respond. UE-2 may select the 5G ProSe inter-UE relay based on factors such as signal strength, local policies, and operator policies for each relay service code (if applicable).

[0404] 4. If necessary, security setup occurs between UE-2 and the selected 5G ProSe UE relay (relay-1 in this case).

[0405] If the existing PC5 link can be reused, then use the link modification request and link modification accept message.

[0406] Note 2: Conflicts between link modification requests and direct communication requests can be identified in phase 3.

[0407] 5. UE-2 replies to Relay-1 with a Direct Communication Acceptance Message. The parameters contained in the Direct Communication Acceptance Message are described in Clause 6.4.3.7.

[0408] 6. For IP services, assign an IPv6 prefix or IPv4 address to the target 5G ProSe Layer 3 UE as defined in Clause 5.5.1.4.

[0409] 7. If necessary, security setup occurs between UE-1 and relay-1.

[0410] 8. For 5G ProSe UE-to-UE relay communication with integrated discovery, after receiving end-to-end QoS information from UE-1, relay-1 uses a link modification request message to provide second-hop QoS information to UE-2.

[0411] 9. For 5G ProSe UE-to-UE relay communication with integrated discovery, UE-2 responds with a link modification receive message.

[0412] 10. Relay-1 responds to UE-1 using direct communication acceptance. The parameters contained in the direct communication acceptance message are described in Clause 6.4.3.7.

[0413] 11. For IP services, assign an IPv6 prefix or IPv4 address to the source 5G ProSe Layer 3 UE as defined in Clause 5.5.1.4.

[0414] 12. For IP communication, the 5G ProSe Layer 3 UE inter-relay can store the association between user information (i.e., application layer 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 10, the source 5G ProSe Layer 3 UE can send a DNS query to the 5G ProSe Layer 3 UE inter-relay after step 11 to request the IP address of the target 5G ProSe Layer 3 UE, and the 5G ProSe Layer 3 UE inter-relay will transmit the IP address of the target 5G ProSe Layer 3 UE back to the source 5G ProSe Layer 3 UE.

[0415] For Ethernet communication, the 5G ProSe Layer 3 UE inter-relay acts as an Ethernet switch by maintaining the association between the PC5 link and the Ethernet MAC address received from the 5G ProSe Layer 3 UE.

[0416] For unstructured service communication, for each pair of source and target 5G ProSe layer 3 UEs, the 5G ProSe layer 3 UE relay maintains a 1:1 mapping between the PC5 link and the source 5G ProSe layer 3 UE, as well as between the PC5 link and the target 5G ProSe layer 3 UE.

[0417] The source 5G ProSe layer 3 UE communicates with the target 5G ProSe layer 3 UE via 5G ProSe layer 3 UE relay.

[0418] 6.7.3.3 Procedure for communication via Layer 2 UE inter-relay

[0419] The 3GPP TS 23.304 V 18.6.0 standard is titled "Integrated Discovery 5G ProSe Inter-UE Relay Communication via Layer 2 Inter-UE Relay". Figure 6 7.3.3-1 reproduced as Figure 16 ]

[0420] 0-5. Its relationship with Figure 6 Steps 0 through 5 of .7.3.2-1 are the same.

[0421] 6. Its relationship with Figure 6 Step 7 of .7.3.2-1 is the same.

[0422] 7. Its relationship with Figure 6 Step 10 of .7.3.2-1 is the same.

[0423] The parameters contained in the above message are described in Clause 6.4.3.7.4.

[0424] 8. For 5G ProSe UE-to-UE relay communication via Layer 2 UE-to-UE relay, UE-1 establishes an end-to-end connection for unicast mode communication with UE-2.

[0425] 3GPP TS 24.554 introduced the following concepts:

[0426] 7.2.2 5G ProSe Direct Link Establishment Procedure

[0427] 7.2.2.1 Overview

[0428] Depending on the type of 5G ProSe direct link establishment procedure (i.e., UE-oriented Layer 2 link establishment or ProSe service-oriented Layer 2 link establishment in 3GPP TS 23.304[2]), the 5G ProSe direct link establishment procedure is used to establish a 5G ProSe direct link between two UEs or to establish multiple 5G ProSe direct links between a UE and multiple target UEs. The UE that sends the request message is referred to as the “initiating UE” and the other UE is referred to as the “target UE”. If the request message does not indicate a specific target UE (i.e., the request message does not contain target user information) and multiple target UEs are interested in the ProSe application indicated in the request message, the initiating UE will process the corresponding response messages received from those target UEs. The maximum number of 5G ProSe direct links established in a UE at any given time should not exceed the maximum number specified in the implementation scheme of the established 5G ProSe direct links.

[0429] Note 1: The maximum number of 5G ProSe direct links to be established is recommended to be 8.

[0430] When the 5G ProSe direct link establishment procedure for the 5G ProSe layer 3 remote UE is successfully completed, and if there is a PDU session established for the relay of the 5G ProSe remote UE, the 5G ProSe layer 3 UE to the network relay UE will execute the remote UE reporting procedure as specified in 3GPP TS 24.501

[11] .

[0431] Note 2: A single PC5 unicast link is established between the 5G ProSe Layer 2 UE and the network relay UE and the 5G ProSe Layer 2 remote UE to support the PDU session of the 5G ProSe Layer 2 remote UE, as specified in 3GPP TS 38.300

[21] .

[0432] 7.2.2.2 5G ProSe direct link establishment procedure initiated by the initiating UE

[0433] The following prerequisites must be met before initiating this procedure:

[0434] a) UE reception

[0435] 1) A request from the upper layer to transmit data packets for ProSe applications on PC5;

[0436] 2) A request from the lower layer to trigger the establishment of a 5G ProSe direct link;

[0437] 3) A ProSe direct link establishment request message that triggers the establishment of a 5G ProSe direct link in the case of 5G ProSe inter-UE relay; or

[0438] 4) ProSe direct link modification request message that triggers the establishment of 5G ProSe direct link in the case of 5G ProSe UE inter-relay;

[0439] b) The communication mode is unicast (e.g., pre-configured as specified in Clause 5.2.4 or indicated by an upper layer);

[0440] c) The link layer identifier used to initiate the UE (i.e., the layer 2 ID used for unicast communication) is available (e.g., pre-configured or self-assigned) and is not used by other existing 5G ProSe direct links within the initiating UE;

[0441] d) The link layer identifier for the destination UE (i.e., the unicast layer 2 ID or broadcast layer 2 ID of the target UE) can be used by the initiating UE (e.g., pre-configured, obtained as specified in Clause 5.2, known via previous ProSe direct communication, or indicated by the lower layer);

[0442] Note 1: When different ProSe applications are mapped to different preset destination layer 2 IDs, when the initiating UE wants to establish a single unicast link that can be used for more than one ProSe identifier, the UE can choose any of the preset destination layer 2 IDs for unicast initial signaling.

[0443] e) The initiating UE is authorized to perform 5G ProSe direct communication on PC5 of NR-PC5 in the serving PLMN, has a valid authorization to perform 5G ProSe direct communication on PC5 of NR-PC5 when not served by NG-RAN, is authorized to use 5G ProSe UE to network relay UE, is authorized to use 5G ProSe UE-to-UE relay UE, or is authorized to act as 5G ProSe UE-to-UE relay UE. The UE considers itself not to be served by NG-RAN if the following conditions are met:

[0444] 1) Not used by NG-RAN services for direct ProSe communication on PC5;

[0445] 2) The UE is in a restricted service state as specified in 3GPP TS 23.122

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

[0446] i) The UE cannot find a suitable cell in the selected PLMN as specified in 3GPP TS 38.304

[15] ;

[0447] ii) The UE receives a registration rejection message or service rejection message with 5GMM reason #11 “PLMN not allowed” as specified in 3GPP TS 24.501

[11] ;

[0448] iii) The UE receives a registration rejection message or service rejection message with 5GMM reason #7 "5GS service not allowed" as specified in 3GPP TS 24.501

[11] ; or

[0449] iv) The UE does not have a valid USIM. The 5G ProSe direct link establishment procedure is used for direct communication between the 5G ProSe remote UE and the 5G ProSe UE-to-network relay UE, and the RSC is dedicated to emergency services; or

[0450] 3) Being in a restricted service state as specified in 3GPP TS 23.122

[14] for reasons other than i), ii), iii) or iv) above, and located in a geographic area where the UE is equipped with “non-operator-managed” radio parameters as specified in Clause 5.2;

[0451] f) There is no existing 5G ProSe direct link for a pair of peering application layer IDs, or there is an existing 5G ProSe direct link for a pair of peering application layer IDs, and:

[0452] 1) The existing 5G ProSe direct link network layer protocol is not the same as the network layer protocol required by the upper layer for this ProSe application in the UE;

[0453] 2) The security policy (signaling security policy or user plane security policy) corresponding to the ProSe identifier is not compatible with the existing security policy for 5G ProSe direct links; or

[0454] 3) In cases where the 5G ProSe direct link establishment procedure is used for direct communication between a 5G ProSe layer 3 remote UE and a 5G ProSe layer 3 UE to a network relay UE, the existing 5G ProSe direct link for the peer UE is established using a different RSC, or is established but not used for direct communication between a 5G ProSe layer 3 remote UE and a 5G ProSe layer 3 UE to a network relay UE.

[0455] 4) In the case where the 5G ProSe direct link establishment procedure is used for direct communication between a 5G ProSe layer 2 remote UE and a 5G ProSe layer 2 UE to a network relay UE, the existing 5G ProSe direct link for the peer UE is established but not used for direct communication between a 5G ProSe layer 2 remote UE and a 5G ProSe layer 2 UE to a network relay UE.

[0456] 5) In the case where the 5G ProSe direct link establishment procedure is used for direct communication between the source 5G ProSe layer 3 UE and the relay UE between 5G ProSe layer 3 UEs, the initiating UE acts as the source 5G ProSe UE and is used to establish the existing 5G ProSe direct link of the peer UE using different RSCs, or is established but not used for direct communication between the source 5G ProSe layer 3 UE and the relay UE between 5G ProSe layer 3 UEs.

[0457] 6) In the case where the 5G ProSe direct link establishment procedure is used for direct communication between the 5G ProSe UE-to-UE relay UE and the target 5G ProSe UE without integration discovery, the initiating UE acts as the 5G ProSe UE-to-UE relay UE, the 5G ProSe direct link security mode control procedure between the source 5G ProSe UE and the initiating UE has been successfully completed, and no 5G ProSe direct link has been established between the initiating UE and the target 5G ProSe UE, wherein RSC is received in the ProSe direct link establishment request message used for 5G ProSe UE-to-UE relay;

[0458] 7) In the case where the 5G ProSe direct link establishment procedure is used for direct communication between the 5G ProSe layer 3 UE relay UE and the target 5G ProSe layer 3 end UE, the initiating UE acting as the 5G ProSe layer 3 UE relay UE receives a ProSe direct link establishment request message containing a relay indication, and no 5G ProSe direct link is established between the initiating UE and the target 5G ProSe end UE, wherein an RSC is received in the ProSe direct link establishment request message used for 5G ProSe UE relay; or

[0459] 8) In the case of a 5G ProSe direct link establishment procedure used for direct communication between a 5G ProSe layer 3 UE inter-UE relay UE and a target 5G ProSe layer 3 end UE, the initiating UE acting as the 5G ProSe layer 3 UE inter-UE relay UE receives a ProSe direct link modification request message for establishing 5G ProSe UE inter-UE relay communication with an additional 5G ProSe layer 3 end UE as specified in Clause 7.2.3.2, and no 5G ProSe direct link is established between the initiating UE and the additional target 5G ProSe end UE, wherein an RSC is received in the ProSe direct link modification request message for 5G ProSe UE inter-UE relay;

[0460] g) The number of 5G ProSe direct links established is less than the implementation-specific maximum number of 5G ProSe direct links allowed in the UE each time; and

[0461] h) Timer T5088 is not associated with the link layer identifier of the destination UE, or Timer T5088 associated with the link layer identifier of the destination UE has expired or stopped.

[0462] After receiving service data or requests from the upper layer, the initiating UE will export PC5 QoS parameters and assign PQFI for the PC5 QoS flow established as specified in Clause 7.2.7.

[0463] If the 5G ProSe direct link establishment procedure is used for direct communication between a 5G ProSe remote UE and a 5G ProSe UE-to-network relay UE, the UE will use the DUCK or DUSK for UE-to-network relay discovery along with a UTC-based counter for encryption:

[0464] a) Relay service code; and

[0465] b) UP-PRUK ID or CP-PRUK ID (if available)

[0466] As specified in Clause 6.3.5.2 of 3GPP TS 33.503

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

[0467] Note 2: If the UE is neither configured to use DUCK nor DUSK, the relay service code and UP-PRUK ID or CP-PRUK ID will not be encrypted.

[0468] If the 5G ProSe direct link establishment procedure is used for direct communication between a 5G ProSe end UE and a relay UE, the UE will apply the DUCK or DUSK associated with the relay service code along with a UTC-based counter for encryption:

[0469] a) Relay service code; and

[0470] b) UP-PRUK ID or CP-PRUK ID (if available and the UE is not acting as a 5G ProSe UE-to-UE relay UE),

[0471] As specified in Clause 6.3.5.2 of 3GPP TS 33.503

[34] , the UE will use a security-protected relay service code and (if available and the UE is not acting as a 5G ProSe inter-UE relay UE) a security-protected UP-PRUK ID or a security-protected CP-PRUK ID to create a ProSe direct link establishment request message.

[0472] Note 2A: If the UE is neither configured to use DUCK nor DUSK, the relay service code and UP-PRUK ID or CP-PRUK ID are not encrypted.

[0473] If the 5G ProSe direct link establishment procedure uses the ProSe identifier for ranging and sidelink positioning, the UE will apply the DUCK or DUSK used for UE discovery for ranging and sidelink positioning, along with a UTC-based counter, to encryption:

[0474] a) ProSe identifiers for ranging and side-link localization; and

[0475] b) SLPK ID (if available)

[0476] As specified in 3GPP TS 33.533

[55] , the UE will use a security-protected ProSe identifier and a security-protected SLPK ID for ranging and side-link positioning to create a ProSe direct link establishment request message.

[0477] Note 2B: If the UE is neither configured with DUCK nor DUSK, the ProSe identifier and SLPK ID for ranging and sidelink positioning are not encrypted.

[0478] In order to initiate the 5G ProSe direct link establishment procedure, the initiating UE will create a ProSe direct link establishment request message.

[0479] Initiating UE:

[0480] a) The source user information is set to the application layer ID of the initiating UE received from the upper layer, or, in the case of 5G ProSe direct link establishment procedure used for 5G ProSe direct communication between 5G ProSe end UE and 5G ProSe UE relay UE, it is set to the user information of the source 5G ProSe end UE.

[0481] b) It will include the ProSe identifier received from the upper layer, provided that the 5G ProSe direct link establishment procedure is not used for 5G ProSe direct communication between the 5G ProSe remote UE and the 5G ProSe UE to the network relay UE.

[0482] c) The target user information is set to the application layer ID of the target UE when it is received from the upper layer or when it is known based on the unicast layer 2 ID (i.e., destination layer 2 ID) of the target UE as described in Clause 5.8.2.4 of 3GPP TS 23.304[3], to the user information ID of the 5G ProSe UE to network relay UE obtained during the 5G ProSe UE to network relay UE discovery procedure when the initiating UE acts as a 5G ProSe remote UE, or to the user information ID of the target 5G ProSe end UE in the following cases:

[0483] 1) The initiating UE acts as the source 5G ProSe UE, and the user information of the target 5G ProSe UE is obtained during the 5G ProSe UE inter-relay discovery procedure or received from the upper layer in the case of the establishment of a 5G ProSe direct link with integrated discovery; or

[0484] 2) The UE initiates the 5G ProSe UE relay UE, and the user information of the target 5G ProSe UE is obtained from the ProSe direct link establishment request message or ProSe direct link modification request message from the source 5G ProSe UE;

[0485] ca) will contain inter-UE relay UE user information, which is set to the 5G ProSe inter-UE relay UE user information ID in the following cases:

[0486] 1) Obtained during the 5G ProSe UE-to-UE relay discovery procedure, and used for 5G ProSe direct link establishment procedures for direct 5G ProSe communication between the source 5G ProSe UE and the 5G ProSe UE-to-UE relay UE; or

[0487] 2) The UE initiates the UE to act as a 5G ProSe inter-UE relay UE, and the user information ID is configured under the configuration parameters for 5G ProSe inter-UE relay as specified in Clause 5.2.7;

[0488] cb) will include the target UE's Layer 2 ID, which is set to the target 5G ProSe UE's Layer 2 ID if the initiating UE acts as the source 5G ProSe UE and the target 5G ProSe UE's Layer 2 ID is available in the source 5G ProSe UE via previous direct communication.

[0489] d) If the 5G ProSe direct link is not used for direct communication between a 5G ProSe remote UE and a 5G ProSe UE-to-network relay UE, nor for direct communication between a 5G ProSe end UE and a 5G ProSe UE-to-network relay UE using network-assisted security procedures:

[0490] 1) If the UE PC5 unicast signaling integrity protection policy is set to "need signaling integrity protection" or "prefer signaling integrity protection", it will include a key establishment information container; and if the UE PC5 unicast signaling integrity protection policy is set to "do not require signaling integrity protection", it may include a key establishment information container.

[0491] Note 3: The key establishment information container is provided by the upper layer.

[0492] e) will include:

[0493] 1) Nonce_1, provided that the direct communication is not between the 5G ProSe remote UE and the 5G ProSe UE to network relay UE, nor between the 5G ProSe end UE and the 5G ProSe UE between relay UEs, and the direct communication is not used for the ProSe identifier for ranging and sidelink positioning, or provided that the direct communication is between the 5G ProSe remote UE and the 5G ProSe UE to network relay UE or between the source 5G ProSe end UE and the 5G ProSe UE between relay UEs, and the security procedures on the control plane are used as specified in 3GPP TS 33.503

[34] ;

[0494] 2)K NRP Freshness parameter 1, provided that direct communication occurs between a 5G ProSe remote UE and a 5G ProSe UE-to-network relay UE, or between a source 5G ProSe end UE and a 5G ProSe UE-to-network relay UE, and using a user plane security procedure as specified in 3GPP TS 33.503

[34] ; or

[0495] 3)K SLP Freshness parameter 1, provided that the ProSe identifier used for direct communication for ranging and side-link positioning is specified as in 3GPP TS 33.533

[55] ;

[0496] If the UE PC5 unicast signaling integrity protection policy is set to "requires signaling integrity protection" or "prefers signaling integrity protection", then for the purpose of establishing the session key on the 5G ProSe direct link, it is set to a 128-bit random value generated by the initiating UE.

[0497] Note 4: The Nonce_1IE in the ProSe direct link establishment request message is used to maintain Nonce_1 or K. NRP The value of freshness parameter 1.

[0498] f) It will include its UE security capabilities, instructing the initiating UE to establish a list of supported algorithms for security of this 5G ProSe direct link;

[0499] g) will include K selected by the initiating UE NRP-sess The MSB of the ID, as specified in 3GPP TS 33.503

[34] , is subject to the following conditions:

[0500] 1) ProSe identifiers not used for direct communication in ranging and side-link positioning;

[0501] 2) Direct communication does not occur between the target 5G ProSe terminal UE and the 5G ProSe UE relay UE using network-assisted security procedures; and

[0502] 3) The UE PC5 unicast signaling integrity protection policy is set to "requires signaling integrity protection" or "prefers signaling integrity protection";

[0503] Note 5: If direct communication is neither between a 5G ProSe remote UE and a 5G ProSe UE-to-network relay UE, nor between a 5G ProSe end UE using network-assisted security procedures and a 5G ProSe UE-to-network relay UE, then K NRP-sess ID storage corresponds to K NRP-sess The ID. If direct communication occurs between a 5G ProSe remote UE and a 5G ProSe UE-to-network relay UE, or between a 5G ProSe end UE and a 5G ProSe UE-to-network relay UE using network-assisted security procedures, then K NRP-sess ID storage corresponds to K NRP-sess (If using a security procedure on the user plane) or K relay-sess (If using a security procedure on the control plane) ID.

[0504] g1) will include K selected by the initiating UE. SLP-sess The MSB of the ID, as specified in 3GPP TS 33.533

[55] , is subject to the following conditions:

[0505] 1) ProSe identifiers used for direct communication in ranging and side-link positioning;

[0506] 2) Direct communication does not occur between the target 5G ProSe terminal UE and the 5G ProSe UE relay UE using network-assisted security procedures; and

[0507] 3) The UE PC5 unicast signaling integrity protection policy is set to "requires signaling integrity protection" or "prefers signaling integrity protection";

[0508] h) may contain K NRP ID, provided that the initiating UE has an existing K for the target UE. NRP Furthermore, direct communication occurs neither between a 5G ProSe remote UE and a 5G ProSe UE-to-network relay UE, nor between a 5G ProSe end UE using network-assisted security procedures and a 5G ProSe UE-to-network relay UE.

[0509] i) Include its UE PC5 unicast signaling security policy. Where different ProSe applications are mapped to different PC5 unicast signaling security policies, when the initiating UE wishes to establish a single unicast link usable for more than one ProSe application, each signaling security policy for those ProSe applications should be compatible; for example, "No signaling integrity protection required" and "Signaling integrity protection required" are incompatible. When the 5G ProSe direct link establishment procedure is used for direct communication between a 5G ProSe remote UE and a 5G ProSe UE to a network relay UE, and the RSC is not dedicated to emergency services, the signaling integrity protection policy should be set to "Signaling integrity protection required." When the 5G ProSe direct link establishment procedure is used for direct communication between a 5G ProSe remote UE and a 5G ProSe UE to a network relay UE, and the RSC is not dedicated to emergency services and the initiating UE has a valid USIM, the signaling integrity protection policy should be set to "Preferred signaling integrity protection." In cases where the 5G ProSe direct link establishment procedure is used for direct communication between a 5G ProSe remote UE and a 5G ProSe UE to a network relay UE, and the RSC is not dedicated to emergency services and the initiating UE does not have a valid USIM, the signaling integrity protection policy should be set to "no signaling integrity protection required".

[0510] j) An IE containing the relay service code will be provided, wherein the relay service code IE is set to:

[0511] 1) The relay service code for the target relay UE, provided that the 5G ProSe direct link establishment procedure is used for direct communication between the 5G ProSe remote UE and the 5G ProSe UE to the network relay UE; or

[0512] 2) Indicates the relay service code for the connectivity service requested by the source 5G ProSe UE, provided that the 5G ProSe direct link establishment procedure is used for direct communication between the (source or target) 5G ProSe UE and the 5G ProSe UE relay UE:

[0513] k) Includes a UTC-based counter LSB, which is set to the four least significant bits of the UTC-based counter in the case of direct communication between a 5G ProSe remote UE and a 5G ProSe UE to a network relay UE or between a 5G ProSe end UE and a 5G ProSe UE inter-relay UE in the 5G ProSe direct link establishment procedure.

[0514] l) The IE containing the UE identifier is set as the SUCI that initiates the UE in the following cases:

[0515] 1) The 5G ProSe direct link establishment procedure is used for direct communication between a 5G ProSe remote UE and a 5G ProSe UE to a network relay UE, or between a source 5G ProSe UE and a 5G ProSe UE relay UE.

[0516] 2) The RSC is not dedicated to emergency services, or the initiating UE has a valid USIM; and

[0517] 3) Security for 5G ProSe UE to network relay or 5G ProSe UE to relay uses a security procedure on the control plane and the initiating UE does not have a valid CP-PRUK, as specified in 3GPP TS 33.503

[34] , or security for 5G ProSe UE to network relay or 5G ProSe UE to relay uses a security procedure on the user plane and the initiating UE does not have a valid UP-PRUK, as specified in 3GPP TS 33.503

[34] ;

[0518] la) will contain the UE identifier IE, which is set as the PEI of the initiating UE in the following cases:

[0519] 1) The 5G ProSe direct link establishment procedure is used for direct communication between the 5G ProSe remote UE and the 5G ProSe UE to the network relay UE;

[0520] 2) RSC is dedicated to emergency services; and

[0521] 3) The initiating UE does not have a valid USIM;

[0522] m) will contain the user security key ID IE, which is set as follows:

[0523] 1) Initiate UE's UP-PRUK ID, under the following conditions:

[0524] i) The 5G ProSe direct link establishment procedure is used for direct communication between a 5G ProSe remote UE and a 5G ProSe UE to a network relay UE, or for direct communication between a source 5G ProSe UE and a 5G ProSe UE relay UE.

[0525] ii) The initiating UE has a valid UP-PRUK; and

[0526] iii) Security for 5G ProSe UE to network relay or 5G ProSe UE to relay uses security procedures on the user plane, as specified in 3GPP TS 33.503

[34] ;

[0527] 2) The CP-PRUK ID of the initiating UE associated with the relay service code of the target UE, provided that:

[0528] i) The 5G ProSe direct link establishment procedure is used for direct communication between a 5G ProSe remote UE and a 5G ProSe UE to a network relay UE, or for direct communication between a source 5G ProSe UE and a 5G ProSe UE relay UE.

[0529] ii) The initiating UE has a valid CP-PRUK associated with the relay service code of the target UE; and

[0530] iii) Security for 5G ProSe UE to network relay or 5G ProSe UE to relay uses security procedures on the control plane, as specified in 3GPP TS 33.503

[34] ;

[0531] 3) The SLPK ID of the initiating UE associated with the ProSe identifier for ranging and side-link positioning, provided that:

[0532] i) Direct communication of ProSe identifiers for ranging and sidelink positioning using the 5G ProSe direct link establishment procedure; and

[0533] ii) The initiating UE has a valid SLPK associated with the ProSe identifier for ranging and sidelink positioning;

[0534] n) will include the HPLMN ID of the initiating UE, provided that the UP-PRUK ID of the initiating UE is included and is not in NAI format (see 3GPP TS 33.503

[34] );

[0535] o) will include a MIC IE, which is set to the calculated MIC value in the case of the 5G ProSe direct link establishment procedure for direct communication between a 5G ProSe remote UE and a 5G ProSe UE to a network relay UE or between a 5G ProSe end UE and a 5G ProSe UE inter-relay UE and the UE having a DUIK, as specified in Clause 6.3.5.3 of 3GPP TS 33.503

[34] ;

[0536] o1) Includes the MIC IE, which is set to the calculated MIC value in the case of the ProSe identifier used for ranging and sidelink positioning in the 5G ProSe direct link establishment procedure and the UE having a DUIK, as specified in 3GPP TS 33.533

[55] ; and

[0537] p) will include a relay indication that the ProSe direct link establishment request message can be forwarded by the 5G ProSe UE-to-UE relay UE, provided that the 5G ProSe direct link establishment procedure is used for integrated discovery direct communication between the source 5G ProSe UE and the 5G ProSe UE-to-UE relay UE.

[0538] After generating the ProSe direct link establishment request message, the initiating UE should pass this message, along with the source stratum 2 ID and destination stratum 2 ID, to the lower layer for transmission, as follows:

[0539] a) If 5G ProSe direct communication is the result of 5G ProSe direct discovery as defined in Clause 6.2.14, Clause 6.2.15, Clause 8.2.1, Clause 8a.2.1 or Clause 6.2 of 3GPP TS 24.514

[56] :

[0540] Assign source layer 2 ID yourself, and

[0541] 1) Set as the destination layer 2 ID of the target UE layer 2 ID, provided that the UE receives and initiates the UE to act as a 5G ProSe inter-UE relay UE in a ProSe direct link establishment request message or ProSe direct link modification request message from the source 5G ProSe UE; or

[0542] 2) Otherwise, set it to the destination layer 2 ID of the source layer 2 ID in the received ProSe PC5 discovery message used for discovery notification or discovery response;

[0543] b) If the initiating UE acts as the source 5G ProSe UE, and the 5G ProSe direct link establishment procedure is used for direct communication between the source 5G ProSe UE and the relay UE for 5G ProSe UE integration:

[0544] Assign a source layer 2 ID and set the destination layer 2 ID to the broadcast destination layer 2 ID configured as specified in Clause 5.2.4;

[0545] c) If the initiating UE acts as a 5G ProSe inter-UE relay UE, and the 5G ProSe direct link establishment procedure is used for integrated discovery direct communication between the 5G ProSe inter-UE relay UE and the target 5G ProSe end UE:

[0546] Assign a source layer 2 ID and set the destination layer 2 ID as follows:

[0547] 1) Target UE Layer 2 ID, provided it is received in a ProSe direct link establishment request message from the source 5G ProSe UE; otherwise

[0548] 2) Broadcast destination layer 2 ID configured as specified in Clause 5.2.4; or

[0549] d) Otherwise:

[0550] Assign a source layer 2 ID and a destination layer 2 ID set for use in unicast initiation signaling as specified in Clause 5.2.4.

[0551] Note 6: The UE implementation scheme ensures that any value of the source layer 2 ID assigned in a), b), c) and d) is different from any other self-assigned source layer 2 ID used for 5G ProSe direct discovery as specified in Clauses 6.2.14, 6.2.15, 8.2.1 and 8a.2.1, and different from any other pre-configured destination layer 2 ID as specified in Clause 5.2.

[0552] Note 6A: If the 5G ProSe direct link establishment procedure is used for 5G ProSe direct communication between a 5G ProSe layer 3 UE relay UE and a target 5G ProSe layer 3 end UE, the UE implementation scheme ensures that any value of the source layer 2 ID assigned by the user in a), b), and c) is different from any self-assigned source layer 2 ID used for 5G ProSe direct communication whose data unit type is different from the data unit type of the established 5G ProSe direct link.

[0553] Note 6B: If the 5G ProSe direct link establishment 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 and is used for unstructured services, the UE implementation scheme ensures that any value of the source layer 2 ID assigned by the user in a), b), and c) is different from any other self-assigned source layer 2 ID used for 5G ProSe direct communication for unstructured services and different pairs of user information of the source 5G ProSe UE and the target 5G ProSe UE.

[0554] Note 7: The initiating UE may reuse the Layer 2 ID of the initiating UE in a previous 5G ProSe direct link with the same peer UE, except in cases where the 5G ProSe direct link establishment 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 unstructured services, and in cases where the user information of the source 5G ProSe UE and the user information of the target 5G ProSe UE are different from those of the previous 5G ProSe direct link establishment procedure, and in cases where the 5G ProSe direct link establishment 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 with a data unit type different from that of the previous 5G ProSe direct link.

[0555] And start timer T5080.

[0556] Note 8: The default PC5 DRX configuration is used to transmit ProSe direct link establishment request messages, as specified in 3GPP TS 38.300

[21] .

[0557] While timer T5080 is running, the UE should not send new ProSe direct link establishment request messages to the same target UE identified by the same application layer ID. If the target user information IE is not included in the ProSe direct link establishment request message (i.e., the 5G ProSe direct link establishment procedure for ProSe applications), the initiating UE will process multiple ProSe direct link establishment acceptance messages (if any) received from different target UEs before timer T5080 expires to establish multiple 5G ProSe direct links.

[0558] Note 9: To ensure successful 5G ProSe direct link establishment, T5080 should be set to a value greater than the sum of T5089 and T5092.

[0559] The 3GPP TS 24.554 V18.4.0 is titled "5G ProSe Direct Link Establishment Procedure for UE". Figure 7 2.2.2.1 Reproduced as Figure 17 ]

[0560] The 3GPP TS 24.554 V18.4.0 specification is titled "5G ProSe Direct Link Establishment Procedure for ProSe Services". Figure 7 2.2.2.2 Reproduced as Figure 18 ]

[0561] 7.2.2.3 5G ProSe Direct Link Establishment Procedure Accepted by the Target UE

[0562] Upon receiving the ProSe direct link establishment request message, if the target UE accepts the request, the target UE will uniquely assign a PC5 link identifier and create a 5G ProSe direct link context.

[0563] Note 1: The default PC5 DRX configuration is used to receive ProSe direct link establishment request messages, as specified in 3GPP TS 38.300

[21] .

[0564] If the ProSe direct link establishment request message is used for 5G ProSe direct communication between a 5G ProSe remote UE and a 5G ProSe UE-to-network relay UE, the target UE will use the DUIK (if present) to verify the MIC field in the received ProSe direct link establishment request and use DUCK or DUSK to decrypt the encrypted message.

[0565] a) Relay service code; and

[0566] b) UP-PRUK ID or CP-PRUK ID (if received),

[0567] The DUCK or DUSK is used for 5G ProSe UE-to-Network Relay Discovery (see Clause 6.3.5.2 of 3GPP TS 33.503

[34] ), and the target UE verifies whether the relay service code matches the code sent by the target UE during the 5G ProSe UE-to-Network Relay Discovery procedure. In order to retrieve the DUIK for integrity verification and the DUCK or DUSK for decryption, the target UE will use the destination layer 2 ID of the received ProSe direct link establishment request message. The target UE shall match the destination layer 2 ID with the source layer 2 ID stored in the maintenance association of the UE-to-Network Relay Discovery procedure, as described in Clauses 8.2.1.2.2.2 and 8.2.1.3.2.2. For a matching source layer 2 ID, the target UE will use the associated relay service code to identify the provisioned DUIK, DUCK, or DUSK.

[0568] Note 2: If the UE is neither configured to use DUCK nor DUSK, the relay service code and UP-PRUK ID or CP-PRUK ID will not be encrypted.

[0569] If the ProSe direct link establishment request message is used for 5G ProSe direct communication between a 5G ProSe end UE and a 5G ProSe relay UE, the target UE will use DUIK (if present) to verify the MIC field in the received ProSe direct link establishment request and use DUCK or DUSK to decrypt the encrypted message.

[0570] a) Relay service code; and

[0571] b) UP-PRUK ID or CP-PRUK ID (if received),

[0572] The DUCK or DUSK is used for 5G ProSe UE-to-UE relay discovery (see Clause 6.3.5.2 of 3GPP TS 33.503

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

[0573] Note 2A: If the UE is neither configured to use DUCK nor DUSK, the relay service code and UP-PRUK ID or CP-PRUK ID are not encrypted.

[0574] If the ProSe direct link establishment request message uses the ProSe identifier for ranging and sidelink positioning, the target UE will use the DUIK (if present) to verify the MIC field in the received ProSe direct link establishment request and use DUCK or DUSK to decrypt the encrypted message.

[0575] a) ProSe identifiers for ranging and side-link localization; and

[0576] b) SLPK ID (if available)

[0577] The DUCK or DUSK is used for ranging and sidelink localization during UE discovery, and the target UE verifies whether the ProSe identifier for ranging and sidelink localization matches the ProSe identifier sent by the target UE during ranging and sidelink localization during UE discovery.

[0578] Note 2B: If the UE is neither configured with DUCK nor DUSK, the ProSe identifier and SLPK ID for ranging and sidelink positioning are not encrypted.

[0579] If the target UE acts as the target 5G ProSe end UE, and the 5G ProSe direct link establishment procedure is used for integrated discovery direct communication between the 5G ProSe inter-UE relay UE and the target 5G ProSe end UE, then upon receiving a ProSe direct link establishment request message containing the same source user information, ProSe identifier, and relay service code received from multiple 5G ProSe inter-UE relay UEs, the target UE selects the 5G ProSe inter-UE relay UE used to communicate with the source 5G ProSe end UE, as specified in Clause 6.7.3.2 of TS 23.304.

[0580] If the 5G ProSe direct link establishment procedure is not used for direct communication between a 5G ProSe remote UE and a 5G ProSe UE-to-network relay UE, nor for direct communication between a 5G ProSe end UE and a 5G ProSe UE-to-network relay UE using a network-assisted security procedure, and the 5G ProSe direct link establishment procedure is not used for direct communication of ProSe identifiers for ranging and sidelink positioning, then the target UE may initiate the 5G ProSe direct link authentication procedure as specified in Clause 7.2.12, and shall initiate the 5G ProSe direct link security mode control procedure as specified in Clause 7.2.10.

[0581] If the 5G ProSe direct link establishment procedure is used for direct communication between a 5G ProSe remote UE and a 5G ProSe UE-to-network relay UE, or for direct communication between a source 5G ProSe UE using a network-assisted security procedure and a 5G ProSe UE-to-network relay UE, then after receiving the ProSe direct link establishment request message and the initiating UE being identified by SUCI, CP-PRUK ID, or UP-PRUK ID, the target UE will continue with:

[0582] a) Authentication and key negotiation procedures, as specified in Clause 5.5.4 of 3GPP TS 24.501

[11] , provided that security procedures on the control plane as specified in 3GPP TS 33.503

[34] are used; or

[0583] b) A key request procedure, as specified in Clause 8.2.10.2.4, provided that a security procedure on the user plane as specified in 3GPP TS 33.503

[34] is used;

[0584] And if:

[0585] a) The security procedures on the control plane or user plane, as specified in 3GPP TS 33.503

[34] , are successfully completed; or

[0586] b) If the security procedure on the control plane or the security procedure on the user plane as specified in 3GPP TS 33.503

[34] fails, the RSC is dedicated to emergency services and the target UE is configured to provide 5G ProSe direct link for emergency services without 5G ProSe direct link security.

[0587] The 5G ProSe direct link security mode control procedure will be initiated, as specified in Clause 7.2.10.

[0588] Note 3: The configuration of the target UE is based on rules and operator policies to indicate whether 5G ProSe direct link is required for emergency services in the absence of 5G ProSe direct link security. How the target UE is aware of this information depends on the implementation plan.

[0589] If the 5G ProSe direct link establishment procedure is used for direct communication between a 5G ProSe UE-to-UE relay UE and a target 5G ProSe terminal UE using a network-assisted security procedure, the target UE will continue the 5G ProSe direct link security request procedure as specified in Clause 8a.2.10 after receiving the ProSe direct link establishment request message.

[0590] If the 5G ProSe direct link establishment procedure is used for direct communication of the ProSe identifier for ranging and side link positioning, the target UE will continue with the SLP key request procedure as specified in Clause 8.3.1.1.2 of 3GPP TS 24.514

[56] and will initiate the 5G ProSe direct link security mode control procedure as specified in Clause 7.2.10.

[0591] If the 5G ProSe direct link establishment procedure is used for direct communication between a 5G ProSe remote UE and a 5G ProSe UE-to-network relay UE, the RSC is dedicated to emergency services, the initiating UE is identified by the PEI, and the target UE is configured to provide a 5G ProSe direct link for emergency services without 5G ProSe direct link security, then the target UE will initiate the 5G ProSe direct link security mode control procedure as specified in Clause 7.2.10.

[0592] In the 5G ProSe direct link context, the target UE will set the source 2ID and destination 2ID as specified in Clauses 7.2.12 and 7.2.10, and store the corresponding source 2ID for unicast communication and the destination 2ID for unicast communication.

[0593] if:

[0594] a) The target user information IE is included in the ProSe direct link establishment request message, and this IE contains the application layer ID of the target UE; or

[0595] b) The target user information IE is not included in the ProSe direct link establishment request message, and the target UE is interested in the ProSe application identified by the ProSe identifier IE in the ProSe direct link establishment request message;

[0596] The target UE will then:

[0597] a) If direct communication is not used between a 5G ProSe remote UE and a 5G ProSe UE-to-network relay UE, nor for direct communication between a 5G ProSe end UE and a 5G ProSe UE-to-network relay UE using network-assisted security procedures, the 5G ProSe direct link establishment procedure is not used for direct communication of ProSe identifiers for ranging and sidelink positioning:

[0598] 1) The K contained in the ProSe direct link establishment request message NRP ID identifier existing K NRP ;or

[0599] 2) If the ProSe direct link establishment request message does not contain K NRP If the target UE does not have the K ID contained in the ProSe direct link establishment request message, then the target UE does not have the K ID contained in the ProSe direct link establishment request message. NRP The existing K of ID NRP Or the target UE wants to export a new K NRP So, export the new K. NRP This may require performing one or more 5G ProSe direct link authentication procedures as specified in Clause 7.2.12;

[0600] b) If direct communication occurs between a 5G ProSe remote UE and a 5G ProSe UE-to-network relay UE, or between a 5G ProSe end UE and a 5G ProSe UE-to-relay UE, and the initiating UE is identified by a SUCI or CP-PRUK ID and uses the security procedures on the control plane as specified in 3GPP TS 33.503

[34] , then a new K is requested according to the security procedures on the user plane as specified in 3GPP TS 33.503

[34] . NR_ProSe ;

[0601] c) If direct communication occurs between a 5G ProSe remote UE and a 5G ProSe UE-to-network relay UE, or between a 5G ProSe end UE and a 5G ProSe UE-to-relay UE, and the initiating UE is identified by a SUCI or UP-PRUK ID and uses the user plane security procedure specified in 3GPPTS 33.503

[34] , then a new K is requested according to the user plane security procedure. NRP ;as well as

[0602] Note 4: How many times does the 5G ProSe direct link authentication procedure need to be executed to export a new K? NRP It depends on the authentication method used.

[0603] d) If direct communication is between a 5G ProSe remote UE and a 5G ProSe UE-to-network relay UE, RSC is dedicated to emergency services, the initiating UE is identified by PEI, and the target UE's configuration requires providing a 5G ProSe direct link for emergency services without 5G ProSe direct link security, then a new K is generated in the manner defined in the implementation scheme. NRP .

[0604] e) If the 5G ProSe direct link establishment procedure is used for direct communication of the ProSe identifier for ranging and sidelink positioning, then the new K is requested according to the security procedure specified in 3GPP TS 33.533

[55] . SLP .

[0605] If direct communication is between the 5G ProSe remote UE and the 5G ProSe UE-to-network relay UE, and the RSC is dedicated to emergency services, such as the security procedure on the control plane or the security procedure on the user plane as specified in 3GPP TS 33.503

[34] fails, and the target UE is configured to provide a 5G ProSe direct link for emergency services without 5G ProSe direct link security, then the target UE will generate a new K in the manner defined in the implementation scheme. NR_ProSe or K NRP .

[0606] In the existing K NRP or K SLP Identified or new K NRP or K SLP After being exported, or in the new K NRP or K NR_ProSe or K SLP Received or new K NR_ProSe or K NRP Once generated, the target UE will initiate the 5G ProSe direct link security mode control procedure as specified in Clause 7.2.10.

[0607] After the 5G ProSe direct link security mode control procedure is successfully completed, in order to determine whether the ProSe direct link establishment request message is acceptable, in the case of IP communication, the target UE checks whether there is at least one public IP address configuration option supported by both the initiating UE and the target UE.

[0608] If direct communication is between a 5G ProSe remote UE and a 5G ProSe UE-to-network relay UE, and the RSC is dedicated to emergency services, and the security procedure on the control plane or user plane as specified in 3GPP TS 33.503

[34] fails, and the target UE is configured to provide a 5G ProSe direct link for emergency services without 5G ProSe direct link security, then the target UE will execute the 5G ProSe direct link remote identification procedure to obtain the PEI before sending the ProSe direct link establishment accept message to the 5G ProSe remote UE.

[0609] Before sending the ProSe direct link establishment accept message to the 5G ProSe remote UE, the target UE acting as the 5G ProSe layer 3 UE to the network relay UE initiates the PDU session establishment procedure requested by the UE, as specified in 3GPP TS 24.501

[11] , under the following conditions:

[0610] 1) The PDU session for relaying services associated with RSC has not yet been established; or

[0611] 2) A PDU session for relaying services associated with RSC has been established, but the PDU session type is unstructured.

[0612] If the target UE accepts the 5G ProSe direct link establishment procedure, the target UE will create a ProSe direct link establishment accept message. Target UE:

[0613] a) Include source user information, which is set to the application layer ID of the target UE received from the upper layer, or, in the case of 5G ProSe direct link establishment procedure used for 5G ProSe direct communication between 5G ProSe end UE and 5G ProSe UE relay UE, is set to the user information of the target 5G ProSe end UE.

[0614] aa) The UE user information containing the UE inter-UE relay UE information is set as the 5G ProSe UE inter-UE relay UE user information ID in the case of 5G ProSe direct link establishment procedure used for 5G ProSe direct communication between the source 5G ProSe UE and the 5G ProSe UE inter-UE relay UE.

[0615] b) Includes PQFI, corresponding PC5 QoS parameters, and optionally the ProSe identifier accepted by the target UE, provided that the target UE does not act as a 5G ProSe Layer 2 UE to network relay UE and the 5G ProSe direct link establishment procedure does not integrate discovery;

[0616] c) May include PC5 QoS rules, provided that the target UE does not act as a 5G ProSe layer 2 UE to network relay UE and the 5G ProSe direct link establishment procedure does not integrate discovery;

[0617] d) Configure the IE with an IP address set to one of the following values, provided that IP communication is used and the target UE is not acting as a 5G ProSe Layer 2 UE-to-network relay UE, a 5G ProSe Layer 2 UE-to-network relay UE using network-assisted security procedures, or a 5G ProSe Layer 3 UE-to-network relay UE:

[0618] 1) "DHCPv4 server", provided that only the IPv4 address allocation mechanism is supported by the target UE, i.e., it acts as a DHCPv4 server;

[0619] 2) "IPv6 router", provided that only the IPv6 address allocation mechanism is supported by the target UE, i.e., it acts as an IPv6 router;

[0620] 3) "DHCPv4 server and IPv6 router", provided that both IPv4 and IPv6 address allocation mechanisms are supported by the target UE; or

[0621] 4) "Address allocation is not supported" is provided that neither the IPv4 nor IPv6 address allocation mechanism is supported by the target UE and the target UE does not act as a 5G ProSe layer 3 UE to network relay UE.

[0622] Note 5: If communication uses Ethernet or unstructured data unit type, the UE does not include an IP address configuration IE, nor does it include a link-local IPv6 address IE.

[0623] e) The received ProSe direct link security mode completion message contains the link-local IPv6 address IE formed locally based on IETF RFC 4862

[25] , provided that the IP address configuration IE is set to "address allocation not supported", the received ProSe direct link security mode completion message contains the link-local IPv6 address IE and the target UE does not act as a 5G ProSe layer 2 UE to network relay UE, 5G ProSe layer 3 UE to network relay UE or a 5G ProSe layer 2 UE to network relay UE or a 5G ProSe layer 3 UE to network relay UE using a security procedure with network assistance;

[0624] f) Include the configuration of UE PC5 unicast user plane security protection based on the agreed user plane security policy, as specified in 3GPP TS 33.503

[34] . If direct communication is between a 5G ProSe remote UE and a 5G ProSe UE-to-network relay UE, RSC is dedicated to emergency services, and:

[0625] 1) The security procedure on the control plane or the security procedure on the user plane, as specified in 3GPP TS 33.503

[34] , fails; or

[0626] 2) The initiating UE is identified by PEI;

[0627] The target UE will include user plane integrity protection configuration set to "off" and user plane encryption configuration set to "off";

[0628] g) Include the MAC address of the target 5G ProSe layer 3 UE, provided that the 5G ProSe direct link establishment procedure is used for 5G ProSe direct communication between the source or target 5G ProSe layer 3 UE and the relay UE between the 5G ProSe layer 3 UE and for Ethernet services; and

[0629] h) May contain the target 5G ProSe layer 3 UE IP address IE, which is set to the IP address of the target 5G ProSe layer 3 UE, provided that the 5G ProSe direct link establishment procedure is used for 5G ProSe direct communication between the source 5G ProSe layer 3 UE and the relay UE between the 5G ProSe layer 3 UE and the data unit type of the communication is IP.

[0630] After generating the ProSe direct link establishment accept message, the target UE will pass this message, along with the Layer 2 ID of the initiating UE for unicast communication and the Layer 2 ID of the target UE for unicast communication, to the lower layer for transmission and will start timer T5090 in the following cases:

[0631] a) At least one ProSe identifier used for the 5G ProSe direct link satisfies the privacy requirements specified in Clause 5.2.4; or

[0632] b) T5090 is configured as specified in Clause 5.2.5.

[0633] Note 6: The two UEs negotiate the PC5 DRX configuration in the AS layer, and the PC5 DRX parameter values ​​are based on a pair of source and destination layer 2ID configurations in the AS layer, as specified in 3GPP TS 38.300

[21] .

[0634] After sending the ProSe direct link establishment accept message, the target UE provides the following information, along with the Layer 2 ID, to the lower layer, enabling the lower layer to process incoming PC5 signaling or service data:

[0635] a) The PC5 link identifier assigned by the user for this 5G ProSe direct link;

[0636] b) PQFI and its corresponding PC5 QoS parameters (if available);

[0637] c) Activation indication for PC5 unicast user plane security protection for 5G ProSe direct links (if applicable); and

[0638] d) Instructions for emergency services on 5G ProSe direct links, provided that a 5G ProSe direct link has been established between a 5G ProSe Layer 2 remote UE and a 5G ProSe Layer 2 UE to a network relay UE and an RSC dedicated to emergency services.

[0639] If the target UE accepts a 5G ProSe direct link establishment request and the 5G ProSe direct link is established but not used for 5G ProSe direct communication between a 5G ProSe remote UE and a 5G ProSe UE-to-network relay UE, or for 5G ProSe direct communication between a 5G ProSe end UE and a 5G ProSe UE-to-inter-relay UE, then the target UE may perform PC5 QoS flow establishment on the 5G ProSe direct link, as specified in Clause 7.2.7. If the 5G ProSe direct link is established for 5G ProSe direct communication between a 5G ProSe layer 3 remote UE and a 5G ProSe layer 3 UE-to-network relay UE, then the target UE may perform PC5 QoS flow establishment on the 5G ProSe direct link, as specified in Clause 8.2.6. If the 5G ProSe direct link is established for 5G ProSe direct communication between a 5G ProSe layer 3 end UE and a 5G ProSe layer 3 UE-to-inter-relay UE, then the target UE may perform PC5 QoS flow establishment on the 5G ProSe direct link, as specified in Clause 8a.2.7.

[0640] 7.2.2.4 The 5G ProSe direct link establishment procedure initiated by the UE is completed.

[0641] If the target user information IE is included in the ProSe direct link establishment request message, the initiating UE will stop timer T5080 after receiving the ProSe direct link establishment acceptance message. If the target user information IE is not included in the ProSe direct link establishment request message, the initiating UE can keep timer T5080 running and continue processing multiple response messages (i.e., ProSe direct link establishment acceptance messages) from multiple target UEs.

[0642] For each ProSe direct link establishment accept message received, the initiating UE will uniquely assign a PC5 link identifier and create a 5G ProSe direct link context for each 5G ProSe direct link. Then, the initiating UE stores the source stratum 2 ID and destination stratum 2 ID used in the transmission of this message provided by the lower layer in the 5G ProSe direct link context to complete the establishment of a 5G ProSe direct link with the target UE. From then on, the initiating UE will use the established link for ProSe direct communication via PC5, along with additional PC5 signaling messages reaching the target UE.

[0643] If the initiating UE acts as a 5G ProSe inter-UE relay UE, and the 5G ProSe direct link establishment procedure is used for direct communication and integration discovery between the 5G ProSe inter-UE relay UE and the target 5G ProSe end UE, then after receiving the ProSe direct link establishment acceptance message from the target 5G ProSe end UE, the initiating UE will initiate a 5G ProSe direct link security mode control procedure with the source 5G ProSe end UE. After successfully completing the 5G ProSe direct link security mode control procedure with the source 5G ProSe end UE, the initiating UE will create a ProSe direct link establishment acceptance message as specified in Clause 7.2.2.3 and send it to the source 5G ProSe end UE. If the ProSe direct link establishment request message does not contain target user information (IE), the initiating UE acting as a 5G ProSe inter-UE relay UE may initiate a 5G ProSe direct link security mode control procedure with the source 5G ProSe end UE after processing multiple response messages (i.e., ProSe direct link establishment acceptance messages) from multiple target end UEs.

[0644] After receiving the ProSe direct link establishment accept message, the initiating UE provides the following information, along with the Layer 2 ID, to the lower layer, enabling the lower layer to process the incoming PC5 signaling or service data:

[0645] a) The PC5 link identifier assigned by the user for this 5G ProSe direct link;

[0646] b) PQFI and its corresponding PC5 QoS parameters (if available); and

[0647] c) Activation indication for PC5 unicast user plane security protection for 5G ProSe direct links (if applicable).

[0648] The UE will initiate timer T5090 under the following conditions:

[0649] a) At least one ProSe identifier used for the 5G ProSe direct link satisfies the privacy requirements specified in Clause 5.2.4; or

[0650] b) T5090 is configured as specified in Clause 5.2.5.

[0651] Additionally, the initiating UE can perform PC5 QoS flow establishment on the 5G ProSe direct link, as specified in Clause 7.2.7.

[0652] If, after timer T5080 expires, the ProSe direct link establishment request message does not contain target user information (IE) and the initiating UE receives at least one ProSe direct link establishment acceptance message, then the UE implementation scheme will consider the 5G ProSe direct link establishment procedure as completed or restart timer T5080.

[0653] If the 5G ProSe direct link establishment procedure is triggered by a ProSe direct link modification request message from the source 5G ProSe layer 3 UE, as specified in Clause 7.2.3.2, then when the initiating UE acts as a relay UE among 5G ProSe layer 3 UEs, after receiving the ProSe direct link establishment acceptance message, the initiating UE will send a ProSe direct link modification acceptance message to the source 5G ProSe layer 3 UE, as specified in Clause 7.2.3.3.

[0654] If the 5G ProSe direct link establishment 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, and the initiating UE acting as the 5G ProSe layer 3 UE relay UE detects that the MAC address of the target 5G ProSe layer 3 UE in the ProSe direct link establishment acceptance message 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 as specified in Clause 7.2.6.

[0655] [...]

[0656] 7.2.4 5G ProSe Direct Link Identifier Updater

[0657] 7.2.4.1 Overview

[0658] The 5G ProSe Direct Link Identifier Update procedure is used to update and exchange new identifiers (e.g., application layer ID, layer 2 ID, security information, and IP address / prefix) between two UEs before using the new identifier. The UE that sends the ProSe Direct Link Identifier Update Request message is called the "initiating UE," and the other UE is called the "target UE."

[0659] 7.2.4.2 5G ProSe Direct Link Identifier Update Procedure Initiated by the Initiating UE

[0660] The UE will initiate the procedure under the following conditions:

[0661] a) The UE initiates a request to change the application layer ID from the upper layer, and there exists an existing 5G ProSe direct link associated with this application layer ID; or

[0662] b) The privacy timer for the UE’s Layer 2 ID (see Clauses 5.2.4 and 5.2.5) expires for existing 5G ProSe direct links.

[0663] The following prerequisites must be met before initiating this procedure:

[0664] a) Timer T5091 is not running; and

[0665] b) The initiating UE does not execute the 5G ProSe direct link key update procedure initiated by the target UE.

[0666] If the 5G ProSe Direct Link Identifier update procedure is triggered by a change in the application layer ID of the initiating UE, the initiating UE will generate a ProSe Direct Link Identifier Update Request message. In this message, the initiating UE:

[0667] a) It will include the new application layer ID of the initiating UE received from the upper layer;

[0668] b) Will include the new Layer 2 ID assigned by the initiating UE itself;

[0669] c) will include K NRP-sess The new MSB for the ID;

[0670] d) The new IP address / prefix of the initiating UE will be included, provided that IP communication is used, the IP address / prefix of the initiating UE needs to be changed and assigned by the initiating UE, and the 5G ProSe direct link is not used for 5G ProSe layer 2 remote UE and 5G ProSe layer 2 UE to network relay UE 5G ProSe direct communication and the target UE is not a 5G ProSe layer 3 UE inter-relay UE.

[0671] e) It will include the new IP address / prefix of the initiating UE, provided that IP communication is used, the IP address / prefix of the initiating UE needs to be changed and assigned by the initiating UE, and the target UE is a 5G ProSe layer 3 UE inter-UE relay UE;

[0672] f) will include an indication that an IP address / prefix is ​​required, provided that IP communication is used, the target UE is a 5G ProSe Layer 3 inter-UE relay UE, and the initiating UE's IP address / prefix needs to be changed and assigned by the 5G ProSe inter-UE relay UE; and

[0673] g) Include a list of target UE IP addresses / prefixes or a list of target UE user information or both, provided that IP communication is used, the initiating UE's IP address / prefix needs to be changed, and the target UE is a 5G ProSe Layer 3 UE-to-UE relay UE.

[0674] If the 5G ProSe Direct Link Identifier Update procedure is triggered by the expiration of the initiating UE's privacy timer T5090, as specified in Clauses 5.2.4 and 5.2.5, the initiating UE will create a ProSe Direct Link Identifier Update Request message. In this message, the initiating UE:

[0675] a) It will include the new Layer 2 ID assigned by the UE itself;

[0676] b) Will include K NRP-sess The new MSB for the ID;

[0677] c) May contain the new application layer ID of the initiating UE (if received from the upper layer);

[0678] d) The new IP address / prefix of the initiating UE will be included, provided that IP communication is used, the IP address / prefix of the initiating UE needs to be changed and assigned by the initiating UE, and the 5G ProSe direct link is not used for 5G ProSe layer 2 remote UE and 5G ProSe layer 2 UE to network relay UE 5G ProSe direct communication and the target UE is not a 5G ProSe layer 3 UE inter-relay UE.

[0679] e) It will include the new IP address / prefix of the initiating UE, provided that IP communication is used, the IP address / prefix of the initiating UE needs to be changed and assigned by the initiating UE, and the target UE is a 5G ProSe layer 3 UE inter-UE relay UE;

[0680] f) will include an indication that an IP address / prefix is ​​required, provided that IP communication is used, the target UE is a 5G ProSe layer 3-UE inter-relay UE, and the initiating UE's IP address / prefix needs to be changed and assigned by the 5G ProSe layer 3-UE inter-relay UE; and

[0681] g) Include a list of target UE IP addresses / prefixes or a list of target UE user information or both, provided that IP communication is used, the initiating UE's IP address / prefix needs to be changed, and the target UE is a 5G ProSe Layer 3 UE-to-UE relay UE.

[0682] After generating the ProSe Direct Link Identifier Update Request message, the initiating UE transmits this message, along with the initiating UE's old Layer 2 ID for 5G ProSe direct communication and the target UE's Layer 2 ID for 5G ProSe direct communication, to the lower layer for transmission, and starts timer T5082. While timer T5082 is running, the UE should not send the new ProSe Direct Link Identifier Update Request message to the same target UE.

[0683] The 3GPP TS 24.554 V18.4.0 is titled "5G ProSe Direct Link Identifier Updater". Figure 7 2.4.2.1 Reproduced as Figure 19 ]

[0684] 7.2.4.3 5G ProSe Direct Link Identifier Update Procedure Accepted by the Target UE

[0685] Upon receiving the ProSe direct link identifier update request message, if the target UE determines:

[0686] a) The 5G ProSe direct link associated with this request message remains valid; and

[0687] b) Timer T5083, used to identify the 5G ProSe direct link via this request message, is not running.

[0688] The target UE then accepts the request and responds with a ProSe direct link identifier update accept message.

[0689] If the target UE is a 5G ProSe layer 3 inter-UE relay UE and the required IP address / prefix indication is received from the initiating UE in the ProSe direct link identifier update request message, then the target UE assigns a new IP address / prefix to the initiating UE.

[0690] If the target UE is a 5G ProSe layer 3 inter-UE relay UE, the 5G ProSe layer 3 inter-UE relay UE will initiate a 5G ProSe inter-UE relay update procedure as specified in Clause 7.2.13.

[0691] The target UE will generate a ProSe Direct Link Identifier Update Accept Message. In this message, the target UE:

[0692] a) Include the new Layer 2 ID assigned by the target UE itself;

[0693] b) Will include K NRP-sess The new LSB for ID;

[0694] c) Include the K that initiated the UENRP-sess The new MSB for the ID;

[0695] d) Will include the new Layer 2 ID of the initiating UE;

[0696] e) Include the new application layer ID of the target UE (if received from the upper layer), provided that the target UE is not a 5G ProSe layer 3 UE inter-UE relay UE;

[0697] f) The new IP address / prefix of the initiating UE will be included if it is received from the initiating UE and IP communication is used, or if it is received from the initiating UE and an IP address / prefix indication is required and IP communication is used.

[0698] g) will include the new application layer ID of the initiating UE (if received from the initiating UE); and

[0699] h) Include the new IP address / prefix of the target UE, provided that IP communication is used, the IP address / prefix of the target UE needs to be changed, and the 5G ProSe direct link is not used for 5G ProSe Layer 2 remote UE and 5G ProSe Layer 2 UE to network relay UE 5G ProSe direct communication.

[0700] After generating the ProSe Direct Link Identifier Update Accept Message, the target UE transmits this message along with the initiating UE's old Layer 2 ID for 5G ProSe direct communication and the target UE's old Layer 2 ID for 5G ProSe direct communication to the lower layer for transmission, and starts timer T5083. While timer T5083 is running, the UE should not send the new ProSe Direct Link Identifier Update Accept Message to the same initiating UE.

[0701] Before the target UE uses the new Layer 2 ID to receive services, the target UE will continue to receive services with the old Layer 2 ID from the initiating UE (i.e., the old Layer 2 ID of the initiating UE and the old Layer 2 ID of the target UE).

[0702] Before the target UE receives the ProSe direct link identifier update ACK message from the initiating UE, the target UE will continue to send services to the initiating UE using the old Layer 2 ID (i.e., the old Layer 2 ID of the initiating UE for 5G ProSe direct communication and the old Layer 2 ID of the target UE for 5G ProSe direct communication).

[0703] 7.2.4.4 5G ProSe Direct Link Identifier Update Procedure Confirmed by the Initiating UE

[0704] Upon receiving the ProSe Direct Link Identifier Update Accept message, the initiating UE will save its new IP address / prefix (if received on the ProSe Direct Link Identifier Update Accept message), stop timer T5082, and respond with a ProSe Direct Link Identifier Update ACK message. In this message, the initiating UE:

[0705] a) Include the new Layer 2 ID of the target UE;

[0706] b) Include the target UE in K NRP-sess The new LSB for ID;

[0707] c) Include the target UE's new application layer ID (if received);

[0708] d) Include the target UE's new IP address / prefix (if received); and

[0709] e) will include the new IP address / prefix of the initiating UE (if received on the ProSe direct link identifier update accept message).

[0710] After generating the ProSe direct link identifier update ACK message, the initiating UE passes this message together with the initiating UE's old Layer 2 ID for 5G ProSe direct communication and the target UE's old Layer 2 ID for 5G ProSe direct communication to the lower layer for transmission, and stops timer T5090 (if it is running) and starts timer T5090, which is configured if at least one of the ProSe identifiers for 5G ProSe direct link satisfies the privacy requirements specified in Clause 5.2.4 or the privacy requirements specified in Clause 5.2.5.

[0711] After sending the ProSe direct link identifier update ACK message, the initiating UE will update the associated 5G ProSe direct link context using the new identifier and pass the new Layer 2 ID (i.e., the new Layer 2 ID of the initiating UE for 5G ProSe direct communication and the new Layer 2 ID of the target UE for 5G ProSe direct communication) along with the PC5 link identifier down to the lower layer. Then, the initiating UE will use the new Layer 2 ID (i.e., the new Layer 2 ID of the initiating UE for 5G ProSe direct communication and the new Layer 2 ID of the target UE for 5G ProSe direct communication) to transmit PC5 signaling messages and PC5 user plane data.

[0712] The initiating UE will continue to receive services with the old Layer 2 ID (i.e., the old Layer 2 ID of the initiating UE for 5G ProSe direct communication and the old Layer 2 ID of the target UE for 5G ProSe direct communication) from the target UE until it receives services with the new Layer 2 ID (i.e., the new Layer 2 ID of the initiating UE and the new Layer 2 ID of the target UE) from the target UE.

[0713] 7.2.4.5 The 5G ProSe direct link identifier update procedure performed by the target UE is completed.

[0714] Upon receiving the ProSe direct link identifier update ACK message, the target UE will update the associated 5G ProSe direct link context using the new identifier, pass the new Layer 2 ID (i.e., the new Layer 2 ID of the initiating UE and the new Layer 2 ID of the target UE) down to the lower layer, stop timer T5083 and timer T5090 (if running), and start timer T5090, which is configured if at least one of the ProSe identifiers used for the 5G ProSe direct link satisfies the privacy requirements specified in Clause 5.2.4 or as specified in Clause 5.2.5. Then, the target UE will use the new Layer 2 ID (i.e., the new Layer 2 ID of the initiating UE for 5G ProSe direct communication and the new Layer 2 ID of the target UE for 5G ProSe direct communication) to transmit PC5 signaling messages and PC5 user plane data.

[0715] 7.2.4.6 5G ProSe Direct Link Identifier Update Procedure Not Accepted by the Target UE

[0716] If the ProSe Direct Link Identifier Update Request message cannot be accepted, the target UE will send a ProSe Direct Link Identifier Update Reject message. The ProSe Direct Link Identifier Update Reject message contains a PC5 signaling protocol reason IE set to one of the following reason values:

[0717] #3 A conflict with the Layer 2 ID used for 5G ProSe direct communication was detected;

[0718] #16 Unknown target UE IP address / prefix or target UE application layer ID; or

[0719] #111 Unspecified protocol error.

[0720] For a ProSe direct link identifier update request message received from a Layer 2 ID (for 5G ProSe direct communication), if the target UE already has an existing link using this Layer 2 ID or is currently processing a ProSe direct link identifier update request message from the same Layer 2 ID but whose user information is different from the user information IE contained in this new incoming message, the target UE will send a ProSe direct link identifier update rejection message with PC5 signaling protocol reason value #3 "Conflict detected in Layer 2 ID for 5G ProSe direct communication".

[0721] Note: After receiving the ProSe direct link identifier update rejection message, whether the initiating UE initiates a 5G ProSe direct link release procedure or another 5G ProSe direct link identifier update procedure with a new layer 2 ID depends on the UE implementation scheme.

[0722] For a ProSe Direct Link Identifier Update Request message received from a source 5G ProSe UE, if the target UE is a 5G ProSe Layer 3 Inter-UE Relay UE and receives PC5 signaling protocol reason value #17 "Unknown IP address / prefix or application layer ID of the initiating UE" in a ProSe Inter-UE Relay Update Reject message from the target 5G ProSe UE, as specified in Clause 7.2.13.5, then the target UE will send a ProSe Direct Link Identifier Update Reject message with PC5 signaling protocol reason value #16 "Unknown IP address / prefix or application layer ID of the target UE".

[0723] For other reasons that cause the link identifier update to fail, the target UE will send a ProSe direct link identifier update rejection message with the PC5 signaling protocol reason value #111 "Unspecified protocol error".

[0724] Upon receiving the ProSe Direct Link Identifier Update Rejection Message, the initiating UE will stop timer T5082 and abort this 5G ProSe Direct Link Identifier Update procedure.

[0725] 7.2.4.7 Abnormal situations

[0726] 7.2.4.7.1 Abnormal situations at the UE initiation point

[0727] The following abnormal conditions can be identified:

[0728] a) If timer T5082 expires, the initiating UE will retransmit the ProSe Direct Link Identifier Update Request message and restart timer T5082. After reaching the maximum allowed number of retransmissions, the initiating UE will abort the 5G ProSe Direct Link Identifier Update procedure and may notify the upper layer that the target UE is unreachable.

[0729] Note 1: The maximum number of retransmissions allowed is specific to the UE implementation scheme.

[0730] Note 2: Whether the initiating UE releases the 5G ProSe direct link after the maximum number of allowed retransmissions has been reached depends on its implementation scheme.

[0731] (b) For the same 5G ProSe direct link, if the initiating UE receives a ProSe direct link identifier update request message during the 5G ProSe direct link identifier update procedure, the initiating UE will stop timer T5082 and abort the 5G ProSe direct link identifier update procedure. Subsequent processing depends on the implementation scheme; for example, if still necessary, the initiating UE may wait for a time depending on the implementation scheme to initiate a new 5G ProSe direct link identifier update procedure.

[0732] Note 3: Timer values ​​need to be set depending on the implementation scheme to avoid further conflicts (e.g., random timer values).

[0733] c) For the same 5G ProSe direct link, if the initiating UE receives a ProSe direct link key update request message after initiating the 5G ProSe direct link identifier update procedure, the initiating UE will ignore the ProSe direct link key update request message and continue with the 5G ProSe direct link identifier update procedure.

[0734] d) For the same 5G ProSe direct link, if the initiating UE receives a ProSe direct link release request message after initiating the 5G ProSe direct link identifier update procedure, the initiating UE will stop timer T5082 and terminate the 5G ProSe direct link identifier update procedure and continue the 5G ProSe direct link release procedure.

[0735] e) After sending a ProSe direct link identifier update confirmation message to the target UE, if another ProSe direct link identifier update acceptance message is received from the target UE before receiving a service from the target UE with the new Layer 2 ID, the initiating UE will retransmit the ProSe direct link identifier update confirmation message along with the initiating UE's old Layer 2 ID and the target UE's old Layer 2 ID.

[0736] Note 4: If this service has been sent before the UE retransmits the ProSe direct link identifier update confirmation message, the implementation scheme shall handle the failure of service delivery for the new layer 2 ID.

[0737] f) After sending the ProSe direct link identifier update confirmation message to the target UE, if the initiating UE continues to receive services from the target UE with the old Layer 2 ID, and does not receive services from the target UE with the new Layer 2 ID during a specific time period greater than the value of timer T5083, the initiating UE will terminate the 5G ProSe direct link identifier update procedure and may release the 5G ProSe direct link.

[0738] 7.2.4.7.2 Abnormal situations at the target UE

[0739] The following abnormal conditions can be identified:

[0740] a) If timer T5083 expires, the target UE will retransmit the ProSe Direct Link Identifier Update Accept Message and restart timer T5083. After reaching the maximum allowed number of retransmissions, the target UE will abort the 5G ProSe Direct Link Identifier Update procedure and may notify the upper layer that the UE is unreachable.

[0741] Note 1: The maximum number of retransmissions allowed is specific to the UE implementation scheme.

[0742] Note 2: Whether the target UE releases the 5G ProSe direct link after the maximum number of allowed retransmissions has been reached depends on its implementation scheme.

[0743] (b) If a ProSe direct link identifier update request is received during the operation of timer T5083, the target UE will stop timer T5083 and abort the ongoing 5G ProSe direct link identifier update procedure. The target UE will then process the new ProSe direct link identifier update request as specified in clause 7.2.4.3.

[0744] c) For the same 5G ProSe direct link, if the target UE receives a ProSe direct link release request message during the 5G ProSe direct link identifier update procedure, the target UE will stop timer T5083, abort the 5G ProSe direct link identifier update procedure, and continue the 5G ProSe direct link release procedure.

[0745] [...]

[0746] 7.2.13 5G ProSe UE Inter-Relay Update Procedure

[0747] 7.2.13.1 Overview

[0748] The 5G ProSe UE-to-UE relay update procedure is used to update the target 5G ProSe UE with the new IP address / prefix or new application layer ID, or both, of the source 5G ProSe UE during the 5G ProSe direct link identifier update procedure between the source 5G ProSe UE and the 5G ProSe Layer 3 UE-to-UE relay UE. The 5G ProSe Layer 3 UE-to-UE relay UE initiates a 5G ProSe UE-to-UE update procedure with each target UE as indicated by the source 5G ProSe UE during the 5G ProSe direct link identifier update procedure.

[0749] The relay UE between 3 UEs in the 5G ProSe layer is referred to as the initiating UE in this procedure and the target 5G ProSe end UE is referred to as the target UE.

[0750] 7.2.13.2 5G ProSe Inter-UE Relay Update Procedure Initiated by the Initiating UE

[0751] If, as part of a 5G ProSe direct link identifier update procedure, the initiating UE receives a ProSe direct link identifier update request message from a source 5G ProSe UE, then the initiating UE will initiate a 5G ProSe UE-to-UE relay update procedure with the target UE.

[0752] The initiating UE retrieves the target UE's entry from its local table based on the target 5G ProSe end UE user information received in the ProSe Direct Link Identifier Update Request message. The initiating UE initiates a 5G ProSe relay update procedure with each 5G ProSe target end UE.

[0753] To initiate a 5G ProSe inter-UE relay update procedure, the initiating UE will generate a ProSe inter-UE relay update request message. In this message, the initiating UE:

[0754] a) It will include the new Layer 2 ID assigned by the UE itself;

[0755] b) A new MSB containing the KNRP-sess ID;

[0756] c) Include the old IP address / prefix of the source 5G ProSe UE, provided that the IP address / prefix of the source 5G ProSe UE has changed or will change (i.e., assigned by the initiating UE);

[0757] d) Include the old application layer ID of the source 5G ProSe UE, provided that the application layer ID of the source 5G ProSe UE has changed;

[0758] e) Includes the new application layer ID of the source 5G ProSe UE, provided that the new application layer ID of the source 5G ProSe UE is received in the ProSe direct link identifier update request message; and

[0759] f) The new IP address / prefix of the source 5G ProSe UE will be included if the new IP address / prefix of the source 5G ProSe UE is received in the ProSe Direct Link Identifier Update Request message, or if the IP address / prefix indication is received in the ProSe Direct Link Identifier Update Request message and the new IP address / prefix of the source 5G ProSe UE is assigned by the initiating UE.

[0760] The initiating UE should pass this message, along with the initiating UE's old Layer 2 ID for 5G ProSe direct communication and the target UE's Layer 2 ID for 5G ProSe direct communication, to the lower layer for transmission, and start timer T5097. While timer T5097 is running, the initiating UE should not send the new ProSe inter-UE relay update request message to the same target UE.

[0761] The 3GPP TS 24.554 V18.4.0 is named "5G ProSe Direct Relay Update". Figure 7 2.13.2.1 Reproduced as Figure 20 ]

[0762] 7.2.13.3 5G ProSe Inter-UE Relay Update Procedure Accepted by the Target UE

[0763] Upon receiving a ProSe inter-UE relay update request message, if the target UE determines that the 5G ProSe direct link associated with the request message is still valid, the target UE accepts the request.

[0764] If the target UE determines that it can accept the ProSe Inter-UE Relay Update Request message, the target UE will replace the original IP address / prefix of the source 5G ProSe UE with the new IP address / prefix for unicast communication received in the message. The target UE will also replace the original application ID of the source 5G ProSe UE with the new application ID for unicast communication (if received in the ProSe Inter-UE Relay Update Request message). The target UE will then create a ProSe Inter-UE Relay Update Accept message. In this message, the target UE:

[0765] a) Include the new Layer 2 ID assigned by the target UE itself;

[0766] b) Create a new LSB containing the KNRP-sess ID;

[0767] c) A new MSB containing the KNRP-sess ID of the initiating UE;

[0768] d) Will include the new Layer 2 ID of the initiating UE;

[0769] e) Includes the old IP address / prefix of the source 5G ProSe UE (if received from the initiating UE);

[0770] f) Include the old application layer ID of the source 5G ProSe UE (if received from the initiating UE);

[0771] g) will include the new application layer ID of the source 5G ProSe UE (if received from the initiating UE); and

[0772] h) will include the new IP address / prefix of the source 5G ProSe UE (if received from the initiating UE).

[0773] After generating the ProSe UE inter-UE relay update accept message, the target UE passes this message, along with the target UE's old Layer 2 ID for 5G ProSe direct communication and the initiating UE's old Layer 2 ID for 5G ProSe direct communication, to the lower layer for transmission.

[0774] Before the target UE uses the new Layer 2 ID to receive services, the target UE will continue to receive services with the old Layer 2 ID from the initiating UE (i.e., the old Layer 2 ID of the initiating UE and the old Layer 2 ID of the target UE).

[0775] Before the target UE uses the new IP address / prefix to receive services, the target UE will continue to receive services with the old IP address / prefix (i.e., the old IP address / prefix of the source 5G ProSe UE and the old IP address / prefix of the target 5G ProSe UE) from the source 5G ProSe UE.

[0776] 7.2.13.4 The 5G ProSe inter-UE relay update procedure initiated by the UE is completed.

[0777] Upon receiving the ProSe Inter-UE Relay Update Accept Message, if the initiating UE determines that it can accept the ProSe Inter-UE Relay Update Accept Message, the initiating UE will stop timer T5097.

[0778] If the received ProSe UE-to-UE relay update request message contains more than one target 5G ProSe UE, the initiating UE can wait for responses from all target UEs and then stop timer T5097.

[0779] 7.2.13.5 5G ProSe Inter-UE Relay Update Procedure Not Accepted by the Target UE

[0780] If the ProSe Inter-UE Relay Update Request message cannot be accepted, the target UE will generate a ProSe Inter-UE Relay Update Reject message. In this message, the target UE will include a PC5 signaling protocol reason IE, indicating one of the following reason values:

[0781] #17: Unknown initiating UE's IP address / prefix or initiating UE's application layer ID;

[0782] After generating the ProSe Inter-UE Relay Update Rejection Message, the target UE passes this message, along with the Layer 2 ID of the initiating UE for unicast communication and the Layer 2 ID of the target UE for unicast communication, to the lower layer for transmission.

[0783] Upon receiving a ProSe inter-UE relay update rejection message, the initiating UE will stop timer T5097 and continue the ongoing procedure, which triggers the initiation of a 5G ProSe inter-UE relay update procedure to indicate the failed target UE to the source 5G ProSe UE, as specified in Clause 7.2.4.6.

[0784] 7.2.13.6 Abnormal situations

[0785] 7.2.13.6.1 Initiating Abnormal Situations at the UE

[0786] a) Timer T5097 expired.

[0787] The initiating UE will retransmit the ProSe Inter-UE Relay Update Request message and restart timer T5097. After the maximum number of allowed retransmissions is reached, the initiating UE will abort the 5G ProSe Inter-UE Relay Update procedure and continue the ongoing procedure that triggers the initiation of the 5G ProSe Inter-UE Relay Update procedure, indicating the failed target UE to the source 5G ProSe UE, as specified in Clause 7.2.4.6.

[0788] Note 1: The maximum number of retransmissions allowed is specific to the UE implementation scheme.

[0789] [...]

[0790] 10.3.18 ProSe Direct Link Identifier Update Request

[0791] 10.3.18.1 Message Definition

[0792] This message is sent by the UE to another peer UE to initiate a direct link identifier update procedure. See Table 10.3.18.1.1.

[0793] Message type: ProSe direct link identifier update request

[0794] Meaning: Dual

[0795] Direction: UE to peer UE

[0796] Table 10.3.18.1.1 of 3GPP TS 24.554 V18.4.0, entitled "ProSe Direct Link Identifier Update Request Message Content", is reproduced as follows: Figure 21 ]

[0797] 10.3.18.2 Source User Information

[0798] When the UE receives a new application layer ID, it includes this IE.

[0799] 10.3.18.3 Source Link Local IPv6 Address

[0800] This IE is included when the link-local IPv6 address changes at the UE and the 5G ProSe direct link is not used for 5G ProSe Layer 2 remote UE and 5G ProSe Layer 2 UE to network relay UE direct communication.

[0801] Version 10.3.18.4 requires an IP address / prefix indicator.

[0802] This IE is included when the initiating UE, acting as a 5G ProSe Layer 3 UE, requires a new IP address / prefix allocated by a 5G ProSe Layer 3 UE-to-relay UE.

[0803] 10.3.18.5 Blank

[0804] 10.3.18.6 List of Target UE User Information

[0805] The IE is included when a UE acting as a 5G ProSe Layer 3 end UE changes its IP address / prefix and its peer UE (i.e., the target 5G ProSe end UE) needs to be notified of the new IP address / prefix.

[0806] List of target IP addresses in 10.3.18.7

[0807] The IE is included when a UE acting as a 5G ProSe Layer 3 end UE changes its IP address / prefix and its peer UE (i.e., the target 5G ProSe end UE) needs to be notified of the new IP address / prefix.

[0808] 10.3.18.8 Source UE IP address

[0809] This IE is included when a UE acting as a 5G ProSe layer 3 terminal UE changes its IP address / prefix.

[0810] [...]

[0811] 10.3.21 ProSe Direct Link Identifier Update Rejected

[0812] 10.3.21.1 Message Definition

[0813] This message is sent by the target UE to the initiating UE to indicate that the link identifier update request is not accepted. See Table 10.3.21.1.1.

[0814] Message type: ProSe direct link identifier update rejection

[0815] Meaning: Dual

[0816] Direction: UE to peer UE

[0817] Table 10.3.21.1.1 of 3GPP TS 24.554 V18.4.0, entitled "ProSe Direct Link Identifier Update Rejection Message Content", is reproduced as follows: Figure 22 ]

[0818] [...]

[0819] 10.3.28 ProSe Inter-UE Relay Update Request

[0820] 10.3.28.1 Message Definition

[0821] This message is sent by the 5G ProSe Layer 3 inter-UE relay UE that handles communication between the source UE and the target UE to initiate a relay update procedure. See Table 10.3.28.1.1.

[0822] Message type: ProSe Inter-UE Relay Update Request

[0823] Meaning: Dual

[0824] Direction: UE to peer UE

[0825] Table 10.3.28.1.1 of 3GPP TS 24.554 V18.4.0, entitled "ProSe Inter-UE Relay Update Request Message Content", is reproduced as follows: Figure 23 ]

[0826] 10.3.28.2 Legacy source UE IP address

[0827] If IP communication is used and the IP address changes at the source UE, then the IE will be included.

[0828] 10.3.28.3 New Source UE IP Address

[0829] If IP communication is used and the IP address changes at the source UE, then the IE will be included.

[0830] 10.3.28.4 Old Source UE User Information

[0831] If the source UE application layer ID changes, then the IE will be included.

[0832] 10.3.28.5 New Source UE User Information

[0833] If the source UE application layer ID changes, then the IE will be included.

[0834] 10.3.28.6 Old Source UE User Information

[0835] When a 5G ProSe Layer 3 inter-UE relay UE receives the source user information IE in a ProSe direct link identifier update request message, it includes this IE. This IE contains user information of the initiating UE associated with the direct link of the 5G ProSe Layer 3 inter-UE relay UE.

[0836] 10.3.28.7 New Source UE User Information

[0837] When a 5G ProSe Layer 3 inter-UE relay UE receives the source user information IE in the ProSe Direct Link Identifier Update Request message, it includes this IE. This IE contains the user information of the newly initiating UE specified in the source user information IE in the ProSe Direct Link Identifier Update Request message.

[0838] 10.3.29 ProSe UE Inter-Relay Update Acceptance

[0839] 10.3.29.1 Message Definition

[0840] This message is sent by the target UE to the 5G ProSe layer 3 inter-UE relay UE to complete the relay update procedure. See Table 10.3.29.1.1.

[0841] Message type: ProSe UE-to-UE relay update acceptance

[0842] Meaning: Dual

[0843] Direction: UE to peer UE

[0844] Table 10.3.29.1.1 of 3GPP TS 24.554 V18.4.0, entitled "ProSe UE Inter-Relay Update Accept Message Content", is reproduced as follows: Figure 24 ]

[0845] 10.3.29.2 Legacy source UE IP address

[0846] If the 5G ProSe target UE receives the old source UE IP address IE in the ProSe UE inter-UE relay update request message, then the IE will be included.

[0847] 10.3.29.3 New Source UE IP Address

[0848] If the 5G ProSe target UE receives a new source UE IP address IE in the ProSe UE inter-UE relay update request message, then that IE will be included.

[0849] 10.3.29.4 Old Source UE User Information

[0850] If the 5G ProSe target UE receives the old source UE user information IE in the ProSe UE inter-UE relay update request message, then the IE will be included.

[0851] 10.3.29.5 New Source UE User Information

[0852] If the 5G ProSe target UE receives the new source UE user information IE in the ProSe UE inter-UE relay update request message, then the IE will be included.

[0853] 10.3.29.6 Old Source UE User Information

[0854] When the target UE receives the old source user information IE in the ProSe UE inter-UE relay update request message, it will include the IE.

[0855] 10.3.29.7 New Source UE User Information

[0856] When the target UE receives a new source user information IE in the ProSe UE inter-UE relay update request message, it will include that IE.

[0857] [...]

[0858] 10.3.33 ProSe UE Inter-UE Relay Update Rejection

[0859] 10.3.33.1 Message Definition

[0860] This message is sent by the target 5G ProSe end UE to the relay UE between 5G ProSe layer 3 UEs to reject the relay update procedure. See Table 10.3.33.1.1.

[0861] Message type: ProSe UE-to-UE relay update rejection

[0862] Meaning: Dual

[0863] Direction: UE to peer UE

[0864] Table 10.3.33.1.1 of 3GPP TS 24.554 V18.4.0, entitled "ProSe Inter-UE Relay Update Rejection Message Content", is reproduced as follows: Figure 25 ]

[0865] [...]

[0866] 3GPP TS 23.304 describes support for inter-UE relay. That is, when two UEs cannot communicate directly with each other, a relay UE can be used to support communication between two (Layer 2 or Layer 3) ProSe end UEs. The inter-UE relay UE establishes a PC5 link with each of the two ProSe end UEs containing a source ProSe end UE (e.g., on the first PC5 hop) and a target ProSe end UE (e.g., on the second PC5 hop) to forward services of interest for the ProSe service between the two ProSe end UEs. If the source ProSe end UE wishes to communicate with multiple target ProSe end UEs, the (first hop) PC5 link between the source ProSe end UE and the ProSe inter-UE relay UE can be shared among the multiple target ProSe end UEs, while the (second hop) PC5 link can be established individually between the ProSe inter-UE relay UE and the target ProSe end UEs.

[0867] To establish a PC5 link, a Layer 2 link establishment procedure without discovery can be used as specified in Clause 6.7.1 of 3GPP TS 23.304, or a Layer 2 link establishment procedure with discovery can be used as specified in Clause 6.7.3 of 3GPP TS 23.304 (i.e., a Layer 2 link establishment procedure without discovery can be used if the Layer 2 link establishment procedure is initiated for a relay UE or the source UE has selected a specific relay UE, and a Layer 2 link establishment procedure with discovery can be used if the Layer 2 link establishment procedure is initiated for any relay UE or the source UE has not yet discovered any relay UE). For shared PC5 links, a Layer 2 link modification procedure should be used. According to 3GPP TS 23.304, a PC5 link can be associated with a relay service code and can support one or more services / applications identified by one or more ProSe identifiers.

[0868] According to Clause 6.7.1.2 of 3GPP TS 23.304, the Link Identifier Update (LIU) procedure, as defined in Clause 6.4.3.2 of 3GPP TS 23.304, is repeatedly used to perform link identifier updates between the source ProSe UE and the relay UE between the ProSe UE, and when the IP address / prefix needs to be changed, the LIU procedure is similar to that in 3GPP TS 23.304. Figure 6 7.1.2-1 (reproduced as) Figure 7 The relay update procedure collaboration is described in [2] ). Details of the LIU procedure are provided in Clause 7.2.4 of [2] and details of the relay update procedure are provided in Clause 7.2.13 of [2].

[0869] The LIU procedure is used to update and exchange new identifiers (e.g., application layer ID, layer 2 ID, security information, and IP address / prefix) between two UEs for 5G ProSe direct links before using the new identifier. The source ProSe UE can change its user information. Typically, when user information changes, the corresponding IP address / prefix should also change. The source ProSe UE can initiate the LIU procedure for the U2U relay UE by sending a ProSe Direct Link Identifier Update Request message to the U2U relay UE. The ProSe Direct Link Identifier Update Request message may contain a list of the target UE's user information and / or a list of the target UE's IP address / prefix. In response to receiving the ProSe Direct Link Identifier Update Request message, the U2U relay UE can initiate a 5G ProSe Inter-UE Relay Update procedure, as specified in Clause 7.2.13 of 3GPP TS 24.554. U2U relay UEs can individually initiate a relay update procedure for each of the target ProSe UEs indicated in the list of target UE user information, to update those target ProSe UEs with the new identifier of the source ProSe UE.

[0870] According to clause 7.2.13.3 of 3GPP TS 24.554, upon receiving a ProSe Inter-UE Relay Update Request message, the target UE (acting as the target ProSe UE in the 5G ProSe Inter-UE Relay Update procedure) will replace the original IP address / prefix of the source 5G ProSe UE with the new IP address / prefix of the source 5G ProSe UE, and replace the original application ID of the source 5G ProSe UE with the new application ID of the source 5G ProSe UE. Then, if the target UE determines that it can accept the ProSe Inter-UE Relay Update Request message, it will initiate a UE reply ProSe Inter-UE Relay Update Accept message to the UE (acting as the inter-UE relay UE in the same 5G ProSe Inter-UE Relay Update procedure). Subsequently, the U2U relay UE can continue the LIU procedure with the source ProSe UE by sending a ProSe Direct Link Identifier Update Accept message to the source ProSe UE. If more than one target ProSe UE is involved, the initiating UE can wait for responses from all target UEs (in the 5G ProSe UE-to-UE relay update procedure) before continuing the LIU procedure with the source ProSe UE.

[0871] In one embodiment, from the perspective of a target ProSe UE, the new IP address / prefix of the source ProSe UE may be unacceptable to the target ProSe UE due to conflicts, for example, with IP addresses / prefixes known / used by other ProSe-capable UEs communicating with this target ProSe UE. As specified in Clause 7.2.13.5 of 3GPP TS 24.554, if the ProSe Inter-UE Relay Update Request message is unacceptable, the target UE will reply with a ProSe Inter-UE Relay Update Rejection message to the initiating UE. If the U2U relay UE receives the ProSe Inter-UE Relay Update Rejection message, the U2U relay UE will continue its ongoing LIU procedure, which triggers the initiation of a relay update procedure, indicating the failed target UE to the source ProSe UE, as specified in Clause 7.2.4.6 of 3GPP TS 24.554. In other words, if a U2U relay UE receives a ProSe inter-UE relay update rejection message from one or more target ProSe end UEs, the U2U relay UE can reply to the source ProSe end UE with a ProSe direct link identifier update rejection message.

[0872] For example, the source UE can send a first-hop DCR message (containing user information, such as source UE ID1) to the relay UE. In response to receiving the first-hop DCR message, the relay UE can send a second-hop DCR message (containing user information, such as source UE ID1). Both the first-hop and second-hop DCR messages can contain a relay service code to identify the connectivity service. It is possible that more than one target 5G ProSe UE can receive the second-hop DCR message from the relay UE, and these target 5G ProSe UEs may be interested in the connectivity service or they may match the relay service code. In this case, each of these target 5G ProSe UEs can continue with the corresponding link establishment procedure with the relay UE to establish an individual second-hop PC5 link between the relay UE and each target 5G ProSe UE.

[0873] For example, there exists a first target UE and a second target UE, and they receive a second-hop DCR message from a relay UE. The first target UE can subsequently establish a first second-hop PC5 link with the relay UE, and the second target UE can subsequently establish a second second-hop PC5 link with the relay UE. The first target UE can send a first second-hop DCA message to the relay UE to complete the establishment of the first second-hop PC5 link. The second target UE can send a second second-hop DCA message to the relay UE to complete the establishment of the second second-hop PC5 link. Afterward, the relay UE can reply with a first-hop Direct Communication Accept (DCA) message to the source UE. In inter-UE relay communication, the source UE can use its IP address / prefix (e.g., IP-S1), the IP address / prefix of the first target UE (e.g., IP-T1), and the IP address / prefix of the second target UE (e.g., IP-T2) to communicate with the first / second target UE via the relay UE.

[0874] Later, as Figure 26 As described, the source UE can send a LIU request message to the relay UE to update its current user information (e.g., from source UE ID1 to source UE ID2). In response to receiving the LIU request message, the relay UE can then initiate a first relay update procedure with a first target UE and a second relay update procedure with a second target UE. The relay UE can send a first relay update request message for the first relay update procedure to the first target UE. The first relay update request message may contain an identifier of the source UE, and includes at least one of, for example, old / current / original user information (e.g., source UE ID1), old / current / original IP address / prefix (e.g., IP-S1), new user information (e.g., source UE ID2), and new IP address / prefix (e.g., IP-S2). Similarly, the relay UE can send a second relay update request message for the second relay update procedure to the second target UE. The second relay update request message may contain an identifier of the source UE, which includes at least one of the following: old / current / original user information (e.g., source UEID1), old / current / original IP address / prefix (e.g., IP-S1), new user information (e.g., source UEID2), new IP address / prefix (e.g., IP-S2).

[0875] For the first target UE, it can accept the first relay update request message and send a first relay update accept message (corresponding to the first relay update request message) to the relay UE. Therefore, the first target UE can replace the old / current / original user information and IP address / prefix of the source UE with the new user information and IP address / prefix of the source UE. However, for the second target UE, it may not accept the second relay update request message (due to, for example, IP address / prefix conflict), and therefore the second target UE can send a relay update reject message (corresponding to the second relay update request message) to the relay UE. Therefore, the relay UE can send a LIU reject message to the source UE. Upon receiving the LIU reject message, it is assumed that the source UE can send a new LIU request message to the relay UE to update its current user information (e.g., from source UE ID1 to source UE ID3).

[0876] In response to receiving a new LIU request message, the relay UE can then initiate a third relay update procedure with the first target UE and a fourth relay update procedure with the second target UE. The relay UE can send a third relay update request message for the third relay update procedure to the first target UE. The third relay update request message may contain an identifier of the source UE, which includes at least one of, for example, old / current / original user information (e.g., source UE ID1), old / current / original IP address / prefix (e.g., IP-S1), new user information (e.g., source UE ID3), and new IP address / prefix (e.g., IP-S3). Similarly, the relay UE can send a fourth relay update request message for the fourth relay update procedure to the second target UE.

[0877] The fourth relay update request message may contain an identifier of the source UE, including at least one of, for example, old / current / original user information (e.g., source UE ID1), old / current / original IP address / prefix (e.g., IP-S1), new user information (e.g., source UE ID3), and new IP address / prefix (e.g., IP-S3). In this case, the first target UE may be unable to accept the third relay update request message because it cannot identify the source UE based on the source UE ID1 indicated in the third relay update request message, since the first target UE has already replaced source UE ID1 with source UE ID2 during the first relay update procedure. The relay UE may then still reply to the source UE with another LIU rejection message (corresponding to a new LIU request message). Therefore, user information updates on the source UE cannot be achieved because the first target UE, implemented using the procedure text in 3GPP TS 24.554, can no longer identify the source UE in subsequent relay update procedures. User information update failure will result in the release or termination of U2U relay communication.

[0878] To address this issue, when / after the relay UE detects that the second relay update procedure is not accepted by the second target UE, the relay UE can initiate another relay update procedure with the first target UE to roll back the identifier of the source UE (e.g., to have the first target UE replace the source UE ID2 with the source UE ID1). That is, in response to receiving a relay update rejection message corresponding to the second relay update request message from the second target UE, the relay UE can send another relay update request message to the first target UE to roll back the original identifier of the source UE. The relay update request message to roll back the original identifier of the source UE may contain the identifier of the source UE, including at least one of the following: user information for rollback (e.g., source UE ID1), IP address / prefix for rollback (e.g., IP-S1), user information for revocation (e.g., source UE ID2), and IP address / prefix for revocation (e.g., IP-S2). In one embodiment, the relay update request message for backing up the original identifier of the source UE may include a back-up indication, such that the first target UE understands that the user information of the source UE is backed up to source UE ID1 and the IP address / prefix of the source UE is backed up to IP-S1. In another embodiment, the relay update request message for backing up the original identifier of the source UE may include a revocation indication, such that the first target UE understands that source UE ID2 and IP-S2 are revoked. The concept of this solution can be found in... Figure 27 This will be explained in more detail.

[0879] On the other hand, if the new IP address / prefix of the source UE is assigned by the relay UE, and if the relay update rejection message from the second target UE can contain information indicating that the second target UE cannot accept the new IP address / prefix of the source UE (e.g., IP-S2), then the relay UE can initiate another relay update procedure with the first target UE. The relay UE can send another relay update request message to the first target UE, and this relay update request message can contain at least one of, for example, old / current / original user information (e.g., source UE ID1), old / current / original IP address / prefix (e.g., IP-S1), new user information (e.g., source UE ID2), and a second new IP address / prefix (e.g., IP-S3). The relay UE can then initiate another relay update procedure with the second target UE. The relay UE may send another relay update request message to the second target UE, and this relay update request message may contain at least one of the following: old / current / original user information (e.g., source UEID1), old / current / original IP address / prefix (e.g., IP-S1), new user information (e.g., source UE ID2), second new IP address / prefix (e.g., IP-S3).

[0880] The concept of the above solution can also be applied to situations where a single source UE communicates with a single target UE via a single relay UE.

[0881] Based on the first relay update accept message received from the first target UE, the relay UE can know that the first target UE has replaced the old / current / original user information of the source UE with the new user information of the source UE. Therefore, when the relay UE sends a third relay update request message to the first target UE in response to receiving a new LIU request message from the source UE, it is also feasible for the relay UE to modify the old / current / original user information of the source UE by changing the source UE ID1 to the source UE ID2 in the third relay update request message, so that the first target UE can identify the source UE based on the applied source UE ID2. The relay UE can also modify the old / current / original IP address / prefix of the source UE by changing IP-S1 to IP-S2 in the third relay update request message. On the other hand, based on the relay update reject message received from the second target UE, the relay UE can know that the second target UE cannot apply the new user information of the source UE. Therefore, when a relay UE sends a fourth relay update request message to a second target UE in response to receiving a new LIU request message from the source UE, the relay UE may not modify the old / current / original user information of the source UE in the fourth relay update request message. Furthermore, the relay UE may not modify the old / current / original IP address / prefix of the source UE in the fourth relay update request message. This alternative concept can be understood in… Figure 28 This will be explained in more detail.

[0882] Figure 30A and Figure 30B This is flowchart 3000 for relay UEs. In step 3005, the relay UE establishes a Layer 2 link with the source UE, a Layer 2 link with the first target UE, and a Layer 3 link with the second target UE, enabling the source UE to communicate with the first and second target UEs via the relay UE. The old user information of the source UE is used to identify the source UE. In step 3010, the relay UE receives a first link identifier update request message from the source UE to update the identifiers of the source UE for the first and second target UEs. The first link identifier update request message contains the first new user information of the source UE. In step 3015, the relay UE sends a first relay update request message to the first target UE and a second relay update request message to the second target UE. The first and second relay update request messages contain the old user information and the first new user information of the source UE.

[0883] In step 3020, the relay UE receives a relay update accept message corresponding to the first relay update request message from the first target UE and a relay update reject message corresponding to the second target UE. In step 3025, the relay UE sends a link identifier update reject message corresponding to the first link identifier update request message to the source UE. In step 3030, the relay UE receives a second link identifier update request message from the source UE for updating the identifiers of the source UE for the first and second target UEs, wherein the second link identifier update request message contains the second new user information of the source UE. In step 3035, the relay UE sends a third relay update request message to the first target UE and a fourth relay update request message to the second target UE, wherein the third relay update request message contains the first new user information and the second new user information of the source UE, and wherein the fourth relay update request message contains the old user information and the second new user information of the source UE.

[0884] In one embodiment, the old IP address / prefix of the source UE can be used before receiving the first link identifier update request message from the source UE. The first link identifier update request message may further include the first new IP address / prefix of the source UE. The first trunk update request message may further include both the old IP address / prefix of the source UE and the first new IP address / prefix of the source UE.

[0885] In one embodiment, the second relay update request message may further include the old IP address / prefix of the source UE and the first new IP address / prefix of the source UE. The relay update rejection message may include information indicating that the second target UE cannot accept the second relay update request message. The second link identifier update request message may further include the second new IP address / prefix of the source UE.

[0886] In one embodiment, the third relay update request message may further include the source UE's first new IP address / prefix and the source UE's second new IP address / prefix. The fourth relay update request message may further include the source UE's old IP address / prefix and the source UE's second new IP address / prefix. User information may be an upper-layer ID, a user information ID, or an application-layer ID.

[0887] Return to reference Figure 3 and Figure 4In an exemplary embodiment from the perspective of the relay UE, the relay UE 300 includes program code 312 stored in memory 310. CPU 308 can execute program code 312 to enable the relay UE to: (i) establish a first Layer 2 link with a source UE, establish a second Layer 2 link with a first target UE, and establish a third Layer 2 link with a second target UE, such that the source UE can communicate with the first and second target UEs via the relay UE, wherein old user information of the source UE is used to identify the source UE; (ii) receive from the source UE a first link identifier update request message for updating the identifiers of the source UE for the first and second target UEs, wherein the first link identifier update request message contains first new user information of the source UE; (iii) send a first relay update request message to the first target UE and a second relay update request message to the second target UE, wherein the first and second relay update request messages contain old user information of the source UE and first new user information of the source UE; (iv) receive from the first... The target UE receives a relay update accept message corresponding to the first relay update request message and a relay update reject message corresponding to the second relay update request message from the second target UE; (v) sends a link identifier update reject message corresponding to the first link identifier update request message to the source UE; (vi) receives a second link identifier update request message from the source UE for updating the identifiers of the source UE for the first target UE and the second target UE, wherein the second link identifier update request message contains the second new user information of the source UE; and (vii) sends a third relay update request message to the first target UE and a fourth relay update request message to the second target UE, wherein the third relay update request message contains the first new user information and the second new user information of the source UE, and wherein the fourth relay update request message contains the old user information and the second new user information of the source UE. Furthermore, the CPU 308 can execute program code 312 to perform all the actions and steps described above or other actions and steps described herein.

[0888] Alternatively, the first target UE may apply the source UE's new IP address / prefix (i.e., IP-S2), and continue to use the source UE's old / current / original IP address / prefix (i.e., IP-S1) when / after the first target UE accepts the first relay update request message or sends a relay update accept message corresponding to the first relay update request message to the relay UE. Then, when / after the first target UE receives the (first) IP packet from the source UE via the relay UE using the source UE's new IP address / prefix (i.e., IP-S2), the first target UE may replace the source UE's old / current / original user information (i.e., source UE ID1) with the source UE's new user information (i.e., source UE ID2).

[0889] Based on the above example, if the first target UE receives a third relay update request message before receiving the (first) IP packet using IP-S2, the first target UE can apply the second-newest IP address / prefix of the source UE (i.e., IP-S3), and continue to use the old / current / original IP address / prefix of the source UE (i.e., IP-S1) when / after the first target UE accepts the third relay update request message or sends a relay update accept message corresponding to the third relay update request message to the relay UE. Then, when / after the first target UE receives the (first) IP packet from the source UE via the relay UE using the second-newest IP address / prefix of the source UE (i.e., IP-S3), the first target UE can replace the old / current / original user information (i.e., source UE ID1) of the source UE with the second-newest user information (i.e., source UE ID3). This solution concept can be found in... Figure 29 This will be explained in more detail.

[0890] More specifically, the PC5 link can be a PC5 connection, a unicast link, a direct link, a Layer 2 link, etc. The source UE can be a source 5G ProSe UE. The target UE can be a target 5G ProSe UE. The relay UE can be a 5G ProSe UE-to-UE relay UE. The user information can be a user information ID, an application layer ID, or an upper layer ID.

[0891] More specifically, the first-hop DCR message can be sent using the source tier 2 ID and destination tier 2 ID of the source UE. The destination tier 2 ID can be a broadcast tier 2 ID associated with a relay service code or connectivity service.

[0892] More specifically, the second-hop DCR message can be sent using the source tier 2 ID and destination tier 2 ID of the relay UE. The destination tier 2 ID can be a broadcast tier 2 ID associated with the relay service code or connectivity service.

[0893] More specifically, a first second-hop DCA message can be sent using the Layer 2 ID of the first target UE as the source and the Layer 2 ID of the relay UE as the destination. A second second-hop DCA message can be sent using the Layer 2 ID of the second target UE as the source and the Layer 2 ID of the relay UE as the destination. A first-hop DCA message can be sent using the Layer 2 ID of the relay UE as the source and the Layer 2 ID of the source UE as the destination.

[0894] More specifically, the ProSe Direct Link Identifier Update Rejection Message corresponding to the ProSe Inter-UE Relay Update Rejection Message may contain information about which target UE(s) cannot apply one or more new identifiers of the source UE. Based on this information, the source UE can remove the target UE(s) from the U2U relay communication from which one or more new identifiers of the source UE(s) cannot be applied (e.g., by initiating a link modification procedure with the relay UE).

[0895] More specifically, a first / third relay update request message can be sent using the Layer 2 ID of the first target UE as the destination and the Layer 2 ID of the relay UE as the source. A second / fourth relay update request message can be sent using the Layer 2 ID of the second target UE as the destination and the Layer 2 ID of the relay UE as the source. A LIU request message can be sent using the Layer 2 ID of the relay UE as the destination and the Layer 2 ID of the source UE as the source.

[0896] More specifically, it is feasible for the source UE to re-initiate the LIU procedure to update its identifier, where the new user information can be the same, but a different IP address / prefix can be reassigned. Therefore, the source UE ID3 included in the third / fourth relay update request message can be the same as the source UE ID2 included in the first / second relay update request message, and the IP-S2 included in the first / second relay update request message can be different from the IP-S3 included in the third / fourth relay update request message.

[0897] More specifically, the relay update request message can be a ProSe inter-UE relay update request message or a similar message with different terminology. The relay update acceptance message can be a ProSe inter-UE relay update acceptance message or a similar message with different terminology. The relay update rejection message can be a ProSe inter-UE relay update rejection message or a similar message with different terminology. The link identifier update request message can be a ProSe direct link identifier update request message or a similar message with different terminology. The link identifier update acceptance message can be a ProSe direct link identifier update acceptance message or a similar message with different terminology. The link identifier update rejection message can be a ProSe direct link identifier update rejection message or a similar message with different terminology.

[0898] Figure 31 This is flowchart 1300 for relay UE. In step 3105, the relay UE establishes a first direct link with the source UE and a second direct link with the target UE to support UE-to-UE (U2U) relay communication between the source UE and the target UE via the relay UE. In step 3110, the relay UE receives a first link identifier update request message from the source UE to update the source UE's first user information to the source UE's second user information. In step 3115, in response to receiving the first link identifier update request message, the relay UE executes a first relay update procedure with the target UE, wherein the first relay update request message sent from the relay UE to the target UE in the first relay update procedure includes the source UE's first user information as the source UE's old user information and includes the source UE's second user information as the source UE's new user information. In step 3120, the relay UE receives a second link identifier update request message from the source UE to update the source UE's first user information to the source UE's third user information. In step 3125, in response to receiving the second link identifier update request message, the relay UE executes a second relay update procedure with the target UE. If the first relay update procedure with the target UE is successfully completed, the second relay update request message sent from the relay UE to the target UE in the second relay update procedure includes the second user information of the source UE as the old user information of the source UE and includes the third user information of the source UE as the new user information of the source UE.

[0899] In one embodiment, if the first relay update procedure with the target UE is successfully completed, the relay UE can receive a relay update acceptance message from the target UE during the first relay update procedure. This relay update acceptance message includes the source UE's first user information as the source UE's old user information and includes the source UE's second user information as the source UE's new user information. The method for sending the first link identifier update request message or the second link identifier update request message can be a ProSe direct link identifier update request message. The first relay update request message or the second relay update request message is a ProSe inter-UE relay update request message, and / or the relay update acceptance message is a ProSe inter-UE relay update acceptance message. If the first relay update procedure with the target UE is not successfully completed, the second relay update request message can include the source UE's first user information as the source UE's old user information and include the source UE's third user information as the source UE's new user information.

[0900] In one embodiment, if the first relay update procedure with the target UE fails to complete successfully, the relay UE may receive a relay update rejection message from the target UE during the first relay update procedure. The relay update rejection message may be a ProSe inter-UE relay update rejection message.

[0901] Return to reference Figure 3 and Figure 4 In an exemplary embodiment from the perspective of the relay UE, the relay UE 300 includes program code 312 stored in memory 310. The CPU 308 can execute program code 312 to enable the relay UE to (i)... and (ii)... Furthermore, the CPU 308 can execute program code 312 to perform all the actions and steps described above or other actions and steps described herein.

[0902] 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.

[0903] 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 foregoing description can be represented by voltage, current, electromagnetic waves, magnetic fields or magnetic particles, light fields or light particles, or any combination thereof.

[0904] Those skilled in the art will further appreciate 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 a combination of both, which may be designed using source decoding or some other technique) and have instructions in various forms of program or design code (which, for convenience, may be referred to herein as "software" or "software module"), or a combination of both. 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 may implement the described functionality in different ways for each specific application, but such implementation decisions should not be construed as causing a departure from the scope of this disclosure.

[0905] Furthermore, the various illustrative logic blocks, modules, and circuits described in conjunction with the aspects disclosed herein can be implemented within or executed by an integrated circuit (“IC”), access terminal, or access point. An IC may include a general-purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, electrical components, optical components, mechanical components, or any combination thereof designed to perform the functions described herein and to execute code or instructions residing within the IC, outside the IC, or both. A 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.

[0906] 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 appended method claims present elements of various steps in a sample order and are not intended to be limited to any particular order or hierarchy presented.

[0907] The steps of the methods or algorithms described in conjunction with the aspects disclosed herein can be implemented directly in hardware, with a software module executed by a processor, or a combination of both. The software module (e.g., containing executable instructions and associated data) and other data can reside in a data memory, such as RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, removable disk, CD-ROM, or any other form of computer-readable storage medium known in the art. The sample storage medium can be coupled to a machine such as a computer / processor (for convenience, the machine may be referred to herein as a "processor"), such that the processor can read information (e.g., code) from the storage medium and write information to the storage medium. The sample storage medium can be 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 a user equipment. Furthermore, in some aspects, any suitable computer program product may include a computer-readable medium comprising code associated with one or more aspects of this disclosure. In some aspects, the computer program product may include packaging material.

[0908] While the invention has been described in conjunction with various aspects, it should be understood that further modifications are possible. This application is intended to cover any variations, uses, or adaptations of the invention that generally follow the principles of the invention and fall within the scope of known and customary practice in the to which this invention pertains.

Claims

1. A method for relaying a user equipment (UE), comprising: The relay UE establishes a first direct link with the source UE and a second direct link with the target UE to support inter-UE (U2U) relay communication between the source UE and the target UE via the relay UE; The relay UE receives from the source UE a first link identifier update request message for updating the first user information of the source UE to the second user information of the source UE; In response to receiving the first link identifier update request message, the relay UE executes a first relay update procedure with the target UE, wherein the first relay update request message sent from the relay UE to the target UE in the first relay update procedure includes the first user information of the source UE as the old user information of the source UE and includes the second user information of the source UE as the new user information of the source UE. The relay UE receives a second link identifier update request message from the source UE for updating the first user information of the source UE to the third user information of the source UE; as well as In response to receiving the second link identifier update request message, the relay UE executes a second relay update procedure with the target UE. If the first relay update procedure with the target UE is successfully completed, the second relay update request message sent from the relay UE to the target UE in the second relay update procedure includes the second user information of the source UE as the old user information of the source UE and includes the third user information of the source UE as the new user information of the source UE.

2. The method according to claim 1, further comprising: If the first relay update procedure with the target UE is successfully completed, the relay UE receives a relay update acceptance message from the target UE in the first relay update procedure, wherein the relay update acceptance message includes the first user information of the source UE as the old user information of the source UE and includes the second user information of the source UE as the new user information of the source UE.

3. The method according to claim 2, wherein the first or second link identifier update request message is a PROSEDIRECT LINK IDENTIFIER UPDATE REQUEST message, the first or second relay update request message is a PROSE UE TO UE RELAY UPDATE REQUEST message, and / or the relay update acceptance message is a PROSE UE TO UE RELAY UPDATE ACCEPT message.

4. The method according to claim 1, wherein if the first relay update procedure with the target UE fails to complete successfully, the second relay update request message includes the first user information of the source UE as the old user information of the source UE and includes the third user information of the source UE as the new user information of the source UE.

5. The method of claim 4, further comprising: If the first relay update procedure with the target UE fails to complete successfully, the relay UE receives a relay update rejection message from the target UE during the first relay update procedure.

6. The method of claim 5, wherein the relay update rejection message is a PROSE UE TO UE RELAYUPDATE REJECT message.

7. A relay user equipment (UE), comprising: Control circuit; A processor, which is installed in the control circuit; as well as A memory, which is installed in the control circuit and operatively coupled to the processor; The processor is configured to execute program code stored in the memory to: Establish a first direct link with the source UE and a second direct link with the target UE to support inter-UE (U2U) relay communication between the source UE and the target UE via the relay UE; Receives a first link identifier update request message from the source UE for updating the first user information of the source UE to the second user information of the source UE; In response to receiving the first link identifier update request message, a first relay update procedure is executed with the target UE, wherein the first relay update request message sent from the relay UE to the target UE in the first relay update procedure includes the first user information of the source UE as the old user information of the source UE and includes the second user information of the source UE as the new user information of the source UE. The source UE receives a second link identifier update request message for updating the first user information of the source UE to the third user information of the source UE; and In response to receiving the second link identifier update request message, a second relay update procedure with the target UE is executed, wherein if the first relay update procedure with the target UE is successfully completed, the second relay update request message sent from the relay UE to the target UE in the second relay update procedure includes the second user information of the source UE as the old user information of the source UE and includes the third user information of the source UE as the new user information of the source UE.

8. The relay UE of claim 7, wherein the processor is further configured to execute program code stored in the memory to: If the first relay update procedure with the target UE is successfully completed, a relay update acceptance message is received from the target UE in the first relay update procedure, wherein the relay update acceptance message includes the first user information of the source UE as the old user information of the source UE and includes the second user information of the source UE as the new user information of the source UE.

9. The relay UE according to claim 8, wherein the first or second link identifier update request message is a PROSE DIRECT LINK IDENTIFIER UPDATE REQUEST message, the first or second relay update request message is a PROSE UE TO UE RELAY UPDATE REQUEST message, and / or the relay update acceptance message is a PROSEUE TO UE RELAY UPDATE ACCEPT message.

10. The relay UE according to claim 7, wherein if the first relay update procedure with the target UE fails to complete successfully, the second relay update request message includes the first user information of the source UE as the old user information of the source UE and includes the third user information of the source UE as the new user information of the source UE.

11. The relay UE of claim 10, wherein the processor is further configured to execute program code stored in the memory to: If the first relay update procedure with the target UE fails to complete successfully, a relay update rejection message is received from the target UE during the first relay update procedure.

12. The relay UE according to claim 11, wherein the relay update rejection message is a PROSE UE TO UERELAY UPDATE REJECT message.

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