Method and apparatus for a relay ue to add a source ue for inter-ue relay communication

Abstract

A method and apparatus for a relay UE to add source UEs for inter-UE relay communication are disclosed. In one embodiment, a target user equipment establishes a PC5 connection with a relay user equipment to support inter-user equipment relay communication between a first source user equipment and the target user equipment via the relay user equipment. The target user equipment also receives a request message from the relay user equipment requesting to establish another PC5 connection with the relay user equipment to support inter-user equipment relay communication with a second source user equipment via the relay user equipment. Further, in response to receiving the request message, the target user equipment sends a reject message to the relay user equipment if the PC5 connection exists.

Description

Technical Field

[0001] This disclosure generally relates to wireless communication networks, and more specifically, to methods and apparatus in wireless communication systems for adding source UEs to relay user equipment (UEs) for inter-UE relay communication. Background Technology

[0002] 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 with Internet Protocol (IP) packets. This type of IP packet communication can provide users of mobile communication devices with IP-bearing voice, multimedia, multicast, and video-on-demand communication services.

[0003] 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 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

[0004] A method and apparatus for a target UE are disclosed. In one embodiment, the target UE establishes a PC5 connection with a relay UE to support inter-UE relay communication between a first source UE and the target UE via the relay UE. The target UE also receives from the relay UE a request message to establish another PC5 connection with the relay UE to support inter-UE relay communication with a second source UE via the relay UE. Furthermore, in response to receiving the request message, if a PC5 connection already exists, the target UE sends a rejection message to the relay UE. Attached Figure Description

[0005] Figure 1 A diagram illustrating a wireless communication system according to an exemplary embodiment is shown.

[0006] 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.

[0007] Figure 3 This is a functional block diagram of a communication system according to an exemplary embodiment.

[0008] Figure 4 This is based on an exemplary embodiment. Figure 3 Functional block diagram of the program code.

[0009] Figure 5 It is 3GPP TS23.304V18.2.0. Figure 4 Reproduction of .2.8-1.

[0010] Figure 6 It is 3GPP TS23.304V18.2.0. Figure 6 Reproduction of .3.2.4.2-1.

[0011] Figure 7 It is 3GPP TS23.304V18.2.0. Figure 6 Reproduction of .3.2.4.3-1.

[0012] Figure 8 It is 3GPP TS23.304V18.2.0. Figure 6 Reproduction of .4.3.1-1.

[0013] Figure 9 It is 3GPP TS23.304V18.2.0. Figure 6 Reproduction of .4.3.2-1.

[0014] Figure 10 It is 3GPP TS23.304V18.2.0. Figure 6 Reproduction of .4.3.4-1.

[0015] Figure 11 It is 3GPP TS23.304V18.2.0. Figure 6 Reproduction of .7.1.1-1.

[0016] Figure 12 It is 3GPP TS23.304V18.2.0. Figure 6 Reproduction of .7.1.4-1.

[0017] Figure 13 It is 3GPP TS23.304V18.2.0. Figure 6 Reproduction of .7.2-1.

[0018] Figure 14 It is 3GPP TS23.304V18.2.0. Figure 6 Reproduction of .7.3.2-1.

[0019] Figure 15 It is 3GPP TS23.304V18.2.0. Figure 6 Reproduction of .7.3.3-1.

[0020] Figure 16 It is 3GPP TS24.554V18.1.0. Figure 7 Reproduction of .2.2.2.1.

[0021] Figure 17 It is 3GPP TS24.554V18.1.0. Figure 7 Reproduction of .2.2.2.2.

[0022] Figure 18 It is 3GPP TS24.554V18.1.0. Figure 7 Reproduction of .2.3.2.1.

[0023] Figure 19 It is 3GPP TS24.554V18.1.0. Figure 7 Reproduction of .2.3.2.2.

[0024] Figure 20 It is 3GPP TS24.554V18.1.0. Figure 7 Reproduction of .2.10.2.1.

[0025] Figure 21 This is a flowchart based on an exemplary embodiment.

[0026] Figure 22 This is a flowchart based on an exemplary embodiment.

[0027] Figure 23 This is a flowchart based on an exemplary embodiment.

[0028] Figure 24 This is a flowchart based on an exemplary embodiment.

[0029] Figure 25 This is a flowchart based on an exemplary embodiment. Detailed Implementation

[0030] The exemplary wireless communication systems and apparatus described below employ wireless communication systems that support broadcast services. Wireless communication systems are widely deployed to provide various types of communication, such as voice, data, etc. These systems may be based on code division multiple access (CDMA), time division multiple access (TDMA), orthogonal frequency division multiple access (OFDMA), 3GPP Long Term Evolution (LTE) radio access, 3GPP LTE-A or LTE Advanced (LTE Advanced), 3GPP2 Ultra Mobile Broadband (UMB), WiMax, 3GPP New Radio (NR), or some other modulation techniques.

[0031] Specifically, the exemplary wireless communication system apparatus described below can be designed to support one or more standards, such as those provided by the association known herein as the "3rd Generation Partnership Project" (referred to herein as 3GPP), including: TS23.304V18.2.0, "Proximity-Based Service (ProSe) in 5G Systems (5GS) (Revision 18)"; and TS24.554V18.1.0, "Proximity-Based Service (ProSe) Protocol Aspects in 5G Systems (5GS); Phase 3 (Revision 18)". The standards and documents listed above are expressly incorporated herein by reference in their entirety.

[0032] 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, but each antenna group may utilize more or fewer antennas. Access terminal 116 (AT) communicates with antennas 112 and 114, where antennas 112 and 114 transmit information to access terminal 116 via forward link 120 and receive information from access terminal 116 via reverse link 118. Access terminal 122 communicates with antennas 106 and 108, where antennas 106 and 108 transmit information to access terminal 122 via forward link 126 and receive information from access terminal 122 via reverse link 124. In an FDD system, communication links 118, 120, 124, and 126 may use different frequencies for communication. For example, forward link 120 may use a different frequency than the frequency used by reverse link 118.

[0033] Each antenna group and / or the area in which they are designed to communicate is often referred to as a sector of the access network. In an embodiment, each antenna group is designed to communicate with an access terminal in a sector of the area covered by access network 100.

[0034] In communications 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 for different access terminals 116 and 122. Furthermore, compared to an access network that transmits to all its access terminals via a single antenna, an access network using beamforming to transmit to access terminals randomly distributed throughout its coverage area will cause less interference to access terminals in neighboring cells.

[0035] 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, Node B, base station, enhanced base station, evolved Node B (eNodeB), network node, network, or any other term. An access terminal (AT) may also be referred to as user equipment (UE), wireless communication device, terminal, access terminal, or any other term.

[0036] 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 several data streams is provided from the data source 212 to the transport (TX) data processor 214.

[0037] 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 of the data stream based on a specific decoding scheme selected for each data stream to provide decoded data.

[0038] OFDM technology can be used to multiplex the decoded data and pilot data of 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 and decoded data for said data streams are then modulated (i.e., symbol mapped) based on a specific modulation scheme (e.g., BPSK, QPSK, M-PSK, or M-QAM) selected for each data stream to provide modulated symbols. The data rate, decoding, and modulation for each data stream can be determined by instructions executed by processor 230.

[0039] The modulation symbols of all data streams are then provided to the TX MIMO processor 220, which can further process the modulation symbols (e.g., for OFDM). The TX MIMO processor 220 then... 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 transmitting said symbols therefrom.

[0040] Each transmitter 222 receives and processes a corresponding symbol stream to provide one or more analog signals, and further modulates (e.g., amplifies, filters, and up-converts) the analog signals to provide a modulated signal suitable for transmission via a MIMO channel. Then, from N... T Antennas 224a to 224t transmit N from transmitters 222a to 222t. T A modulated signal.

[0041] At receiver system 250, by N R Each antenna 252a to 252r receives the transmitted modulated signal and provides 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.

[0042] The RX data processor 260 then uses specific receiver processing technology from N R Each receiver receives and processes N data. R One received symbol stream to provide N TEach detected symbol stream is then demodulated, deinterleaved, and decoded by the RX data processor 260 to recover the service data of the data stream. The processing performed by the RX processor 260 is complementary to the processing performed by the TX MIMO processor 220 and the TX data processor 214 at the transmitter system 210.

[0043] Processor 270 periodically determines which pre-decoded matrix to use (discussed below). Processor 270 formulates a reverse link message including the matrix index portion and the rank portion.

[0044] The reverse link message may include various types of information related to the communication link and / or the received data stream. The reverse link message is then processed by the TX data processor 238 (which also receives service data from 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.

[0045] At transmitter system 210, the modulated signal from receiver system 250 is received via antenna 224, conditioned by receiver 222, demodulated by demodulator 240, and processed by RX data processor 242 to extract the reverse link message transmitted through receiver system 250. Next, processor 230 determines which pre-decoding matrix to use to determine beamforming weights and then processes the extracted message.

[0046] Turn 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 1 The communication device 300 includes 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 display or speaker). The transceiver 314 is used to receive and transmit wireless signals, to pass the received signals to the control circuit 306, and to wirelessly output signals generated by the control circuit 306. The communication device 300 in the wireless communication system can also be used to implement... Figure 1 AN 100 in the middle.

[0047] Figure 4 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 generally performs radio resource control. Layer 2 portion 404 generally performs link control. Layer 1 portion 406 generally performs physical connections.

[0048] 3GPP TS23.304 introduces the following:

[0049] 4.2.8 5G ProSe UE Inter-UE Relay Reference Architecture

[0050] 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.

[0051] The document titled "Reference Architecture for 5G ProSe Inter-UE Relay" in 3GPP TS23.304V18.2.0 Figure 4 .2.8-1 reproduced as Figure 5 ]

[0052] Each 5G ProSe end UE and 5G ProSe UE inter-relay can have reservations from the same PLMN or different PLMNs.

[0053] [...]

[0054] 5.8.4 Identifiers used for 5G ProSe UE-to-UE relay discovery

[0055] 5.8.4.1 Overview

[0056] The 5G ProSe UE-to-UE relay discovery message contains two sets of identifiers: the direct discovery group and the UE-to-UE relay discovery group.

[0057] - The Direct Discovery Identifier Group is part of the content of the 5G ProSe Direct Discovery Message, as defined in Section 5.8.1.

[0058] - The Inter-UE Relay Discovery Identifier Group contains extended information supporting the discovery and direct discovery of 5G ProSe Inter-UE Relay. 5G ProSe Inter-UE Relay should modify the Inter-UE Relay Discovery Identifier Group and forward the direct discovery group and the Inter-UE Relay Discovery Identifier Group during the discovery procedure.

[0059] 5.8.4.2 Common Identifiers for 5G ProSe Inter-UE Relay Discovery

[0060] The following parameters are used in 5G ProSe UE-to-UE relay discovery notification messages (Model A), 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:

[0061] - Source Layer 2 ID: The source layer 2 ID that 5G ProSe UE-to-UE relay selects for the 5G ProSe UE-to-UE relay discovery notification message.

[0062] - Destination Layer 2 ID: The destination layer 2 ID used for 5G ProSe inter-UE relay discovery notification messages is selected based on the configuration described in section 5.1.5.1.

[0063] -5G ProSe UE Inter-Relay User Information ID: Provides information about 5G ProSe UE Inter-Relay.

[0064] - List of user information IDs for 5G ProSe UEs: Provides information about 5G ProSe UEs.

[0065] - Relay Service Code: Information used to indicate the connectivity services provided by 5G ProSe UE-to-UE relay to 5G ProSe end UEs.

[0066] The following parameters are used in the 5GProSe UE-to-UE relay discovery request message (Model B) between the discoverer 5G ProSe UE and the 5G ProSe UE-to-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:

[0067] - Source Layer 2 ID: The source layer 2 ID selected by the discoverer 5G ProSe UE for use in 5G ProSe UE-to-UE relay discovery request messages.

[0068] - Destination Layer 2 ID: The destination layer 2 ID used for 5G ProSe UE-to-UE relay discovery request messages is selected based on the configuration described in section 5.1.5.1.

[0069] - Discoverer 5G ProSe UE User Information ID: Provides information about the Discoverer 5G ProSe UE.

[0070] - Discoverer 5G ProSe UE User Information ID: Provides information about the Discoverer 5G ProSe UE.

[0071] - Relay service code: Information about connectivity services that the discoverer 5G ProSe UE is interested in.

[0072] The following parameters are used in the 5GProSe UE-to-UE relay discovery response message (Model B) between the discoverer 5G ProSe UE and the 5G ProSe UE-to-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:

[0073] - Source Layer 2 ID: The source layer 2 ID that 5G ProSe UE-to-UE relay selects for the 5G ProSe UE-to-UE relay discovery response message.

[0074] - Destination Layer 2 ID: Set to the source Layer 2 ID of the received 5G ProSe UE-to-UE relay discovery request message.

[0075] - Discoverer 5G ProSe UE User Information ID: Provides information about the Discoverer 5G ProSe UE.

[0076] -5G ProSe UE Inter-Relay User Information ID: Provides information about 5G ProSe UE Inter-Relay.

[0077] - Relay Service Code: Identifies the connectivity service provided by the 5G ProSe UE-to-UE relay to the 5G ProSe end UE, and matches the relay service code from the corresponding discovery request message.

[0078] The following parameters are used for 5G ProSe UE-to-UE relay and 5G ProSe UE-to-UE relay discovery request messages (Model B), 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:

[0079] - Source Layer 2 ID: The source layer 2 ID that the 5G ProSe UE inter-relay chooses for the 5G ProSe UE inter-relay discovery request message.

[0080] - Destination Layer 2 ID: The destination layer 2 ID used for 5G ProSe UE-to-UE relay discovery request messages is selected based on the configuration described in section 5.1.5.1.

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

[0082] - Discoverer 5G ProSe UE User Information ID: Provides information about the Discoverer 5G ProSe UE.

[0083] -5G ProSe UE Inter-Relay User Information ID: Provides information about 5G ProSe UE Inter-Relay.

[0084] - Relay Service Code: Identifies the connectivity service provided by 5G ProSe UE-to-UE relay to the 5G ProSe end UE.

[0085] The following parameters are used in the 5G ProSe UE-to-UE relay and the 5G ProSe discoverer UE-to-UE relay discovery response message (Model B), 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:

[0086] - 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.

[0087] - Destination Layer 2 ID: Set to the source Layer 2 ID of the received 5G ProSe UE-to-UE relay discovery request message.

[0088] - Discoverer 5G ProSe UE User Information ID: Provides information about the Discoverer 5G ProSe UE.

[0089] - Discoverer 5G ProSe UE User Information ID: Provides information about the Discoverer 5G ProSe UE.

[0090] - Relay Service Code: Identifies the connectivity service provided by the 5G ProSe UE-to-UE relay to the 5G ProSe end UE, and matches the relay service code from the corresponding discovery request message.

[0091] Note: The UE implementation scheme needs to ensure that when the UE selects its own source 2ID, the source 2ID selected by the UE is different between 5G ProSe direct discovery (including 5G ProSe UE-to-network relay discovery and 5G ProSe UE-to-UE relay discovery) in Section 6.3.2 and 5G ProSe direct communication (including 5G ProSe UE-to-network relay communication and 5G ProSe UE-to-UE relay communication) in Sections 6.4, 6.5 and 6.7, and is different from any other supplied destination 2ID described in Section 5.1 and any other self-selected source 2ID used for 5G ProSe direct discovery (including 5G ProSe UE-to-network relay discovery and 5G ProSe UE-to-UE relay discovery) with different discovery models.

[0092] 5.8.5 Identifiers for integrated 5G ProSe UE-to-UE relay communication

[0093] For the broadcast direct communication request message at the first hop PC5 reference point, the source layer 2 ID is selected by the source 5GProSe UE itself, and the destination layer 2 ID is selected based on the configuration described in section 5.1.

[0094] For broadcast direct communication request messages at the second-hop PC5 reference point, the source layer 2 ID is selected by the 5GProSe UE inter-relay itself, and the destination layer 2 ID is selected based on the configuration described in section 5.1.

[0095] 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, which contains the received unicast destination layer 2 ID of the target 5G ProSe UE as specified in section 6.4.3.7. The source layer 2 ID is selected by the 5G ProSe UE-to-UE relay itself.

[0096] 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.

[0097] [...]

[0098] 6.3.2.4 5G ProSe UE Inter-Relay Discovery

[0099] 6.3.2.4.1 Overview

[0100] 5G ProSe UE-to-UE relay discovery is suitable for both 5G ProSe Layer 3 and Layer 2 UE-to-UE relay discovery for public safety purposes and commercial services. To perform 5G ProSe UE-to-UE relay discovery, the 5G ProSe end UE and the 5G ProSe UE-to-UE relay are pre-configured or supplied with the relevant information described in Section 5.1.

[0101] Relay Service Codes (RSCs) are 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 provisioned on both the 5G ProSe inter-UE relay and the 5G ProSe end-UE, as defined in Section 5.1. The 5G ProSe inter-UE relay and the 5G ProSe end-UE determine whether an RSC is providing 5G ProSe Layer 2 or Layer 3 inter-UE relay services based on the policies specified in Section 5.1. 5G ProSe inter-UE relays supporting multiple RSCs broadcast RSCs using multiple discovery messages, with one RSC per discovery message.

[0102] 6.3.2.4.2 Procedure for Relay Discovery between 5G ProSe UEs with Model A

[0103] Figure 6 Section 3.2.4.2-1 describes the procedure for discovery between 5G ProSe UEs with Model A.

[0104] The document titled "5G ProSe Inter-UE Relay Discovery with Model A" in 3GPP TS23.304V18.2.0 Figure 6 .3.2.4.2-1 reproduced as Figure 6 ]

[0105] 1.5G ProSe Inter-UE Relay has discovered other nearby UEs (e.g., via previous 5G ProSe Inter-UE Relay discovery or 5G ProSe Inter-UE Relay communication procedures). 5G ProSe Inter-UE Relay obtains the user information IDs of other nearby UEs for each RSC.

[0106] 2.5G ProSe Inter-UE Relay Transmits Inter-UE Relay Discovery Notification Message. The Inter-UE Relay Discovery Notification Message contains the discovery message type, the user information ID of the 5G ProSe Inter-UE Relay, the RSC, and a list of user information IDs of the 5G ProSe end UE, and is transmitted using the source layer 2 ID and the destination layer 2 ID, as described in section 5.8.4.

[0107] 5G ProSe UE relay will only notify the user information IDs of other nearby UEs, which provided relay_indication when they were previously discovered.

[0108] The 5G ProSe UE monitors notification messages from 5G ProSe inter-UE relays. The 5G ProSe UE determines the destination layer 2 ID for signaling reception, as specified in section 5.1.

[0109] 6.3.2.4.3 Procedure for Relay Discovery between 5G ProSeUEs with Model B

[0110] Figure 6 Section 3.2.4.3-1 describes the procedure for relay discovery between 5G ProSe UEs with Model B.

[0111] The document titled "5G ProSe UE-to-UE Relay Discovery with Model B" is from 3GPP TS23.304V18.2.0. Figure 6 .3.2.4.3-1 reproduced as Figure 7 ]

[0112] 1. The discoverer 5G ProSe UE (UE-1) sends a 5G ProSe Inter-UE Relay Discovery Request message. The 5G ProSe Inter-UE Relay Discovery Request message contains the discovery message type, its own user information ID, RSC, and the user information ID of the discoverer 5G ProSe UE (UE-2), and is sent using the source layer 2 ID and destination layer 2 ID, as described in section 5.8.4.

[0113] 5G ProSe UE-to-UE relay determines the destination layer 2 ID for signaling reception, as specified in section 5.1.

[0114] 2. The 5G ProSe UE-to-UE relay with matching RSC sends a 5G ProSe UE-to-UE relay discovery request message. The 5G ProSe UE-to-UE relay discovery request message contains the type of discovery message, the user information ID of the discoverer 5G ProSe UE (UE-1), the user information ID of the UE-to-UE relay, the RSC, and the user information ID of the discoverer 5G ProSe UE (UE-2), and is sent using the source layer 2 ID and the destination layer 2 ID, as described in section 5.8.4.

[0115] The 5G ProSe UE determines the destination layer 2 ID for signaling reception, as specified in section 5.1.

[0116] 3. The discoverer 5G ProSe UE (UE-2) responds to the 5G ProSe Inter-UE Relay with a 5G ProSe Inter-UE Relay Discovery Response Message, matching the RSC value and the discoverer 5G ProSe UE (UE-1) User Information ID. The 5G ProSe Inter-UE Relay Discovery Response Message contains the discovery message type, RSC, the discoverer 5G ProSe UE (UE-1) User Information ID, and its own User Information ID, and is sent using the source layer 2 ID and destination layer 2 ID, as described in section 5.8.4. If the discoverer 5G ProSe UE (UE-2) receives multiple Inter-UE Relay Discovery Request Messages from different 5G ProSe Inter-UE Relays, it can choose whether to respond to the 5G ProSe Inter-UE Relay (e.g., based on the PC5 signal strength of each received message).

[0117] 4.5G ProSe Inter-UE Relay Transmits 5G ProSe Inter-UE Relay Discovery Response Message. The 5G ProSe Inter-UE Relay Discovery Response Message contains the discovery message type, the user information ID of the inter-UE relay, the RSC, and the user information ID of the discovered 5G ProSe end UE (UE-2), and is transmitted using the source layer 2 ID and the destination layer 2 ID, as described in section 5.8.4.

[0118] 6.3.2.4.4 Candidate 5G ProSe UE Inter-Relay Discovery

[0119] 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 section 6.7.4.

[0120] The procedure for relay discovery between 5G ProSe UEs with Model B (see Section 6.3.2.4.3) differs as follows:

[0121] - Step 1: In the 5G ProSe UE-to-UE relay discovery request message, the RSC is not included, and the user information ID of the discoverer 5G ProSe UE is replaced with the user information ID of the candidate 5G ProSe UE-to-UE relay. If the 5G ProSe UE receives the Layer 2 ID of the candidate 5G ProSe UE-to-UE relay in the Link Modification Request message, it can set the Layer 2 ID of the candidate 5G ProSe UE-to-UE relay as the destination Layer 2 ID.

[0122] Steps 2 and 3 are skipped because the RSC is not present in the received 5G ProSe UE-to-UE relay discovery request message.

[0123] - Step 4: If the 5G ProSe UE-to-UE relay matches the user information ID of the candidate 5G ProSe UE-to-UE relay received in the 5G ProSe UE-to-UE relay discovery request, then it sends a 5G ProSe UE-to-UE relay discovery response, which does not contain the user information ID of the discovered 5G ProSe end UE.

[0124] [...]

[0125] 6.4.3 Unicast Mode 5G ProSe Direct Communication

[0126] 6.4.3.1 Establishment of Layer 2 Links at PC5 Reference Point

[0127] In order to perform unicast mode ProSe direct communication on the PC5 reference point, the UE is configured with relevant information as described in section 5.1.3.

[0128] Figure 6 Section 4.3.1-1 illustrates the Layer 2 link establishment procedure for unicast mode ProSe direct communication on the PC5 reference point.

[0129] The section titled "Layer 2 Link Establishment Procedure" in 3GPP TS23.304V18.2.0 Figure 6 4.3.1-1 reproduced as Figure 8 ]

[0130] 1. The UE determines the destination layer 2 ID for signaling reception for PC5 unicast link establishment, as specified in section 5.8.2.4.

[0131] 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 target UE's application layer ID may be included in the application information.

[0132] 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 section 5.6.1.

[0133] If UE-1 decides to reuse an existing PC5 unicast link as specified in section 5.3.4, then the UE triggers the Layer 2 link modification procedure as specified in section 6.4.3.4.

[0134] 3. UE1 sends a Direct Communication Request message to initiate a unicast Layer 2 link establishment procedure. The Direct Communication Request message includes:

[0135] - Source user information: Application layer ID of the initiating UE (i.e., application layer ID of UE-1).

[0136] - If the ProSe application layer provides the target UE's application layer ID in step 2, then the following information is included:

[0137] - Target user information: Application layer ID of the target UE (i.e., application layer ID of UE-2).

[0138] -ProSe service information: Information about the ProSe identifier used to establish the request layer 2 link.

[0139] - Security information: Information used to establish security.

[0140] Note 1: The required protection of security information and source user information and target user information is defined in TS 33.503

[29] .

[0141] The source layer 2 ID and destination layer 2 ID used to send the direct communication request message are determined as specified in sections 5.8.2.1 and 5.8.2.4. The destination layer 2 ID can be a broadcast or unicast layer 2 ID. When using a unicast layer 2 ID, the target user information is included in the direct communication request message.

[0142] 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.

[0143] The default PC5 DRX configuration can be used to send and receive this message (see TS 38.300

[12] ).

[0144] 4. Establish UE-1's security as follows:

[0145] 4a. If the target user information is contained in the direct communication request message, then the target UE, i.e., UE-2, responds by establishing security with UE-1.

[0146] 4b. If the target user information is not included in the direct communication request message, then a UE that is interested in using the ProSe service of the notification via the PC5 unicast link with UE-1 responds by establishing security with UE-1.

[0147] Note 2: Signaling used for security procedures is defined in TS 33.503

[29] .

[0148] When security protection is enabled, UE-1 sends the following information to the target UE:

[0149] -If using IP communication:

[0150] - IP address configuration: For IP communication, this link requires an IP address configuration, which indicates one of the following values:

[0151] - "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

[0152] - "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

[0153] - "DHCPv4 server and IPv6 router", provided that both IPv4 and IPv6 address allocation mechanisms are supported by the initiating UE; or

[0154] - "Address allocation is not supported" if neither the IPv4 nor IPv6 address allocation mechanism is supported by the initiating UE.

[0155] - 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] .

[0156] - QoS Information: Information about PC5 QoS flows. For each PC5 QoS flow, the PFI and corresponding PC5 QoS parameters (i.e., PQI and other conditionally specified parameters, such as MFBR / GFBR, etc.) and an optional associated ProSe identifier.

[0157] - Optional PC5 QoS rules.

[0158] The source layer 2 ID used for the security establishment procedure is determined as specified in sections 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.

[0159] Upon receiving the security establishment procedure message, UE-1 obtains the Layer 2 ID of the peer UE for future communication, for signaling and data services used on this unicast link.

[0160] 5. The target UE that has successfully established security with UE-1 will directly communicate to receive messages sent to UE-1:

[0161] 5a. (Layer 2 Link Establishment for UE) If the direct communication request message contains target user information, then in the case of application layer ID matching for UE-2, the target UE, i.e., UE-2, responds with a direct communication receive message.

[0162] 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 ProSe service (in the notification) Figure 6 UE-2 and UE-4 in .4.3.1-1 respond to requests by sending a direct communication accept message.

[0163] Direct communication message reception includes:

[0164] - Source User Information: The application layer ID of the UE that sent the direct communication message.

[0165] - QoS Information: Information about PC5 QoS flows. For each PC5 QoS flow, the PFI and the corresponding PC5 QoS parameters requested by UE-1 (i.e., PQI and other parameters conditionally, such as MFBR / GFBR, etc.) and the optional associated ProSe identifier.

[0166] - Optional PC5 QoS rules.

[0167] -If using IP communication:

[0168] - IP address configuration: For IP communication, this link requires an IP address configuration, which indicates one of the following values:

[0169] - "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

[0170] - "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

[0171] - "DHCPv4 server and IPv6 router", provided that both IPv4 and IPv6 address allocation mechanisms are supported by the target UE; or

[0172] - "Address allocation not supported" means that neither the IPv4 nor IPv6 address allocation mechanisms are supported by the target UE.

[0173] - Link-local IPv6 address: If the target UE does not support the IPv6 IP address allocation mechanism, i.e., the IP address configuration indicates "address allocation not supported" and UE-1 includes a link-local IPv6 address in the direct communication request message, 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.

[0174] If two UEs (i.e., the initiating UE and the target UE) are selected to use the link-local IPv6 address, then the two UEs will disable dual address detection as defined in RFC 4862

[17] .

[0175] Note 3: When the initiating UE or the target UE indicates support for the IPv6 router, the corresponding address configuration procedure will be implemented after the Layer 2 link is established, and the link-local IPv6 address will be ignored.

[0176] The ProSe layer of a UE that has established a PC5 unicast link will pass the PC5 link identifier and PC5 unicast link-related information assigned to 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.

[0177] 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 / destination layer 2IDs in the AS layer.

[0178] 6. ProSe data is transmitted via the established unicast link as follows:

[0179] The PC5 link identifier and PFI, along with ProSe data, are provided to the AS layer.

[0180] Alternatively, layer 2 ID information (i.e., source layer 2 ID and destination layer 2 ID) may be provided to the AS layer.

[0181] Note 4: Providing Layer 2 ID information to the AS layer depends on the UE implementation plan.

[0182] 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).

[0183] 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.

[0184] [...]

[0185] 6.4.3.2 Link Identifier Update for Unicast Links

[0186] Figure 6Section 4.3.2-1 illustrates the link identifier update procedure for unicast links. When privacy requirements configure the ProSe identifier associated with a unicast link, the identifier for the unicast mode used for 5G ProSe communication on the PC5 reference point (e.g., application layer ID, source layer 2 ID, and IP address / prefix) will change over time, as specified in sections 5.8.2.1 and 5.8.2.4. The UE may decide to change the identifier for other reasons, such as application layer requirements. This procedure is used to update and exchange the new identifier between the source UE and peer UE for the unicast link before using it, in case of service interruption. When privacy requirements as noted above exist, this procedure is performed on security-protected unicast links.

[0187] If a UE has multiple unicast links using the same application layer ID or layer 2 ID, then the UE needs to update the procedure by executing the link identifier for each unicast link.

[0188] The document titled "Link Identifier Updater" in 3GPP TS23.304V18.2.0 Figure 6 4.3.2-1 Reproduced as Figure 9 ]

[0189] 0. UE-1 and UE-2 have unicast links established as described in section 6.4.3.1.

[0190] 1. UE-1 decides to change its identifier, for example, due to a change in the application layer ID or the expiration of a timer. UE-1 generates its new layer 2 ID and sends a link identifier update request message to UE-2 using the old identifier.

[0191] The Link Identifier Update Request message contains the new identifier to be used (including a new Layer 2 ID, security information, an optional new Application Layer ID, and an optional new IP address / prefix (if using IP communication)). If the security configuration is used for a unicast link, the new identifier will be encrypted to protect privacy. After sending the Link Identifier Update Request message, if UE-1 has data to send, UE-1 will continue to send data services to UE-2 using the old identifier until UE-1 sends a Link Identifier Update Confirmation message to UE-2.

[0192] Note 1: The timer runs for each source layer 2 ID.

[0193] Note 2: When one of the two UEs acts as an IPv6 router (as described in section 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.

[0194] 2. Upon receiving a Link Identifier Update Request message, UE-2 changes its identifier. UE-2 responds with a Link Identifier Update Response message containing the new identifier to be used (including a new Layer 2 ID, security information, an optional new Application Layer ID, and an optional new IP address / prefix (if using IP communication)). If the security configuration is for a unicast link, the new identifier will 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 with the old Layer 2 ID until UE-2 receives services from UE-1 with the new Layer 2 ID. After sending the Link Identifier Update Response message, if UE-2 has data to send, UE-2 continues to send data services to UE-1 using the old identifier until UE-2 receives a Link Identifier Update Confirmation message from UE-1.

[0195] 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 from UE-2, as received 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 with the old Layer 2 ID from UE-2 until UE-1 receives services with the new Layer 2 ID from UE-2.

[0196] 4. The ProSe layer of UE-1 passes the PC5 link identifier of the unicast link 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 allows the AS layer to update the Layer 2 ID provided for the unicast link.

[0197] For this unicast link, UE-1 began using its new identifier and UE-2's new identifier.

[0198] 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 ID for unicast links.

[0199] For this unicast link, UE-2 began using its new identifier and UE-1's new identifier.

[0200] 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] .

[0201] [...]

[0202] 6.4.3.4 Layer 2 Link Modification for Unicast Links

[0203] Figure 6 Section 4.3.4-1 illustrates a Layer 2 link modification procedure for unicast links. This procedure is used to:

[0204] - Add a new PC5 QoS stream to an existing PC5 unicast link.

[0205] This covers both adding new PC5 QoS streams to existing ProSe services and adding new PC5 QoS streams to new ProSe services.

[0206] - Modify existing PC5 QoS flows in existing PC5 unicast links.

[0207] - This covers cases where PC5 QoS parameters are modified for existing PC5 QoS flows.

[0208] 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.

[0209] - Remove existing PC5 QoS flows from existing PC5 unicast links.

[0210] The document titled "Layer 2 Link Modification Procedure" in 3GPP TS23.304V18.2.0 Figure 6 .4.3.4-1 Reproduced as Figure 10 ]

[0211] 0. UE-1 and UE-2 have unicast links established as described in section 6.4.3.1.

[0212] 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 layer ID of the target UE may be included in the application information. If UE-1 decides to reuse an existing PC5 unicast link, as specified in Section 5.3.4, and therefore decides to modify the unicast link established with UE-2, then UE-1 sends a link modification request to UE-2.

[0213] The link modification request message includes:

[0214] a) Add a new PC5 QoS stream to an existing PC5 unicast link:

[0215] - QoS Information: Information about the PC5 QoS flow to be added. For each PC5 QoS flow, this includes the PFI, the corresponding PC5 QoS parameters (i.e., PQI and other conditionally specified parameters such as MFBR / GFBR, etc.), and an optional associated ProSe identifier.

[0216] - Optional PC5 QoS rules.

[0217] b) Modify the PC5 QoS flow in the existing PC5 unicast link:

[0218] - QoS Information: Information about the PC5 QoS flow to be modified. For each PC5 QoS flow, this includes the PFI, the corresponding PC5 QoS parameters (i.e., PQI and other conditionally specified parameters such as MFBR / GFBR, etc.), and an optional associated ProSe identifier.

[0219] - Optional PC5 QoS rules.

[0220] c) Remove PC5 QoS flows from existing PC5 unicast links:

[0221] -PFI.

[0222] 2. UE-2 responds with a link modification acceptance message.

[0223] The link modification acceptance message includes:

[0224] -For cases a) and b) described in step 1:

[0225] - QoS Information: Information about the PC5 QoS flows requested by UE-1. For each PC5 QoS flow, this includes the PFI, the corresponding PC5 QoS parameters (i.e., PQI and other conditionally specified parameters such as MFBR / GFBR, etc.), and an optional associated ProSe identifier.

[0226] - Optional PC5 QoS rules.

[0227] Each UE's ProSe layer provides the AS layer with information about unicast link modifications. This enables the AS layer to update the context associated with the modified unicast link.

[0228] [...]

[0229] 6.4.3.7 Layer 2 Link Management on the PC5 Reference Point for 5G ProSe Inter-UE Relay

[0230] 6.4.3.7.1 Common components of Layer 2 link management on the PC5 reference point for 5G ProSe UE-to-UE relay

[0231] For 5G ProSe communication via 5G ProSe UE relay as described in Sections 6.7.1 and 6.7.2:

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

[0233] - User information ID of the source 5G ProSe UE: The identity (i.e., user information ID) of the source 5G ProSe UE requesting the relay operation.

[0234] -5G ProSe Inter-UE Relay User Information ID: The identity (i.e., user information ID) of the inter-UE relay provided to the source 5G ProSe UE during the 5G ProSe Inter-UE Relay discovery procedure.

[0235] - Target 5G ProSe UE User Information ID: The identity (i.e., user information ID) of the target 5G ProSe UE provided to the source 5G ProSe UE during the UE inter-relay discovery procedure.

[0236] - (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 section 5.8.2.4.

[0237] -ProSe service information: Information about the ProSe identifier used to establish the request layer 2 link.

[0238] -RSC: Connectivity service requested by the source 5G ProSe UE from the 5G ProSe UE-to-UE relay.

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

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

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

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

[0243] - Target 5G ProSe end UE user information ID.

[0244] -5G ProSe UE-to-UE relay user information ID.

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

[0246] -RSC: Connectivity service requested by the source 5G ProSe UE from the 5G ProSe UE-to-UE relay.

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

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

[0249] The direct communication received message at the second-hop PC5 reference point includes:

[0250] - Target 5G ProSe end UE user information ID.

[0251] The direct communication received message at the first hop PC5 reference point includes:

[0252] - Target 5G ProSe end UE user information ID.

[0253] -5G ProSe UE-to-UE relay user information ID.

[0254] The link modification request message on the first hop PC5 reference point includes:

[0255] -Target 5G ProSe UE User Information ID: The identity of the target 5G ProSe UE provided to the source 5G ProSe UE during the UE inter-relay discovery procedure.

[0256] - (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 section 5.8.2.4.

[0257] The link modification request message on the second hop PC5 reference point includes:

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

[0259] - Target 5G ProSe end UE user information ID.

[0260] The link modification acceptance message on the second hop PC5 reference point includes:

[0261] - Target 5G ProSe end UE user information ID.

[0262] The link modification acceptance message on the first hop PC5 reference point includes:

[0263] - Target 5G ProSe end UE user information ID.

[0264] 6.4.3.7.2 Layer 2 Link Management on PC5 Reference Point for 5G ProSe Layer 2 UE Inter-UE Relay

[0265] For 5G ProSe communication via 5G ProSe layer 2 UE relay as described in section 6.7.2, the description in section 6.4.3.7.1 applies.

[0266] The message content on the PC5 reference point for unicast mode 5G ProSe direct communication described in sections 6.4.3.1 to 6.4.3.5 is the same for end-to-end connections between peer 5G ProSe UEs.

[0267] Editor's Note: Whether the LIU between the two UEs in the peer layer has the same message content as the direct PC5 LIU message requires further investigation.

[0268] 6.4.3.7.3 Layer 2 Link Management on PC5 Reference Point for 5G ProSe Layer 3 UE Inter-UE Relay

[0269] For 5G ProSe communication via 5G ProSe layer 3-UE relay as described in Section 6.7.1, the description in Section 6.4.3.7.1 applies, but with the following differences and interpretations:

[0270] - In the security procedure at the first hop PC5 reference point, the source 5G ProSe Layer 3 UE provides the 5G ProSe Layer 3 UE inter-UE relay with IP address configuration or link-local IPv6 address and end-to-end QoS information. 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.

[0271] - In the security procedures at the second-hop PC5 reference point, the 5G ProSe Layer 3 UE-to-UE relay provides the target 5G ProSe UE with 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 5G ProSe Layer 3 UE-to-UE relay provides the Ethernet MAC address of the source 5G ProSe Layer 3 UE instead of IP-related information.

[0272] - 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.

[0273] - Considering the received second-hop QoS, the 5G ProSe layer 3 UE inter-relay determines the first-hop QoS information. The direct communication receive message on the first-hop PC5 reference point also includes the IP address configuration or link-local IPv6 address, the first-hop QoS information, 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 inter-relay provides the Ethernet MAC address of the target 5G ProSe layer 3 UE instead of IP-related information.

[0274] - In the link modification request message at the first-hop PC5 reference point, the source 5G ProSe UE also includes end-to-end QoS information. If the PC5 link is used to transmit Ethernet services, the source 5G ProSe Layer 3 UE can provide its Ethernet MAC address.

[0275] - In the link modification request message at the second-hop PC5 reference point, the 5G ProSe layer 3 UE inter-relay additionally includes QoS information for the second-hop QoS to the target 5G ProSe UE. If the PC5 link is used to transmit Ethernet services, then the 5G ProSe layer 3 UE inter-relay provides the Ethernet MAC address of the source 5G ProSe layer 3 UE.

[0276] - The link modification acceptance message on the second-hop PC5 reference point also 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.

[0277] - Taking into account the received second-hop QoS, the 5G ProSe layer 3 UE inter-relay determines the first-hop QoS information. The link modification receive message on the first-hop PC5 reference point also includes the first-hop QoS information and may include the IP address of the target 5G ProSe UE. If the PC5 link is used to transmit Ethernet services, then the 5G ProSe layer 3 UE inter-relay provides the Ethernet MAC address of the target 5G ProSe layer 3 UE instead of IP-related information.

[0278] 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.

[0279] 6.4.3.7.4 Layer 2 Link Management on PC5 Reference Point for Integrated Discovery-based 5G ProSe UE-to-UE Relay Communication

[0280] This section addresses 5G ProSe UE-to-UE relay communication with integrated discovery mechanisms, as described in section 6.7.3.

[0281] The direct communication request message on the first hop PC5 reference point includes:

[0282] - User information ID of the 5G ProSe terminal UE.

[0283] - (Optional) Target 5G ProSe UE User Information ID: The identity of the target 5G ProSe UE (if provided from the ProSe application layer).

[0284] - (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 section 5.8.2.4.

[0285] -ProSe service information: Information about the ProSe identifier used to establish the request layer 2 link.

[0286] -RSC: Connectivity service requested by the source 5G ProSe UE from the 5G ProSe UE-to-UE relay.

[0287] -Relay_indication: Indicates whether the direct communication request message can be relayed between 5G ProSe UEs.

[0288] - Security information: Information used to establish security for the first-hop PC5 link.

[0289] Note 1: Security information is defined by SA WG3.

[0290] The direct communication request message on the second hop PC5 reference point includes:

[0291] - User information ID of the 5G ProSe terminal UE.

[0292] -5G ProSe UE-to-UE relay user information ID.

[0293] - (Optional) Target 5G ProSe end UE user information ID.

[0294] -ProSe service information: Information about the ProSe identifier.

[0295] -RSC: Connectivity service requested by the source 5G ProSe UE from the 5G ProSe UE-to-UE relay.

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

[0297] Note 2: Security information is defined by SA WG3.

[0298] The direct communication received message at the second-hop PC5 reference point includes:

[0299] - Target 5G ProSe end UE user information ID.

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

[0301] - Target 5G ProSe end UE user information ID.

[0302] -5G ProSe UE-to-UE relay user information ID.

[0303] The following further clarifies the 5G ProSe communication relayed between 3 UEs via the 5G ProSe layer:

[0304] - In the security procedure at the second hop PC5 reference point, the 5G ProSe layer 3 UE inter-relay provides the target 5G ProSe end UE with an IP address configuration or a link-local IPv6 address.

[0305] - 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.

[0306] - In the security procedure at the first hop PC5 reference point, the source 5G ProSe UE provides the 5G ProSe Layer 3 UE inter-relay with IP address configuration, link-local IPv6 address and end-to-end QoS information.

[0307] -5G ProSe Layer 3 UE inter-relay uses Layer 2 link modification to provide second-hop QoS information to the target 5G ProSe UE, as described in Section 6.4.3.4.

[0308] - The QoS information of the first hop is determined by the 5G ProSe layer 3 UE inter-UE relay, which considers 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).

[0309] 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 sections 6.4.3.1 to 6.4.3.5 is the same for end-to-end connections between peer 5G ProSe end UEs.

[0310] [...]

[0311] 6.7 5G ProSe UE-to-UE Relay Communication

[0312] 6.7.1 5G ProSe Communication via 5G ProSe Layer Inter-UE Relay

[0313] 6.7.1.1 Layer 2 Link Establishment for PC5 Communication via 5G ProSe Layer 3 UE Inter-UE Relay

[0314] Figure 6 .7.1.1-1 illustrates the procedure for establishing a Layer 2 link via 5G ProSe Layer 3 UE relay.

[0315] The document titled "Establishment of Layer 2 Links via 5G ProSe Layer 3 UE Inter-UE Relay" in 3GPP TS23.304V18.2.0 Figure 6 .7.1.1-1 reproduced as Figure 11 ]

[0316] 1. Service authorization and provisioning are performed 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 Section 6.2.

[0317] 2. The source 5G ProSe layer 3 end UE performs the discovery of 5G ProSe layer 3 UE inter-UE relay, as described in section 6.3.2.4.

[0318] 3. The source 5G ProSe Layer 3 UE sends a Direct Communication Request message to initiate a unicast Layer 2 link establishment procedure for relaying with the 5G ProSe Layer 3 UE. The parameters included in the Direct Communication Request message are described in Section 6.4.3.7.

[0319] 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.

[0320] 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 an RSC supported by the relay, 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 Section 6.4.3.7 to the 5G ProSe Layer 3 UE-to-UE relay.

[0321] If the Ethernet MAC address of the source 5G ProSe Layer 3 UE is already in use by another 5G ProSe Layer 3 UE, then the 5G ProSe Layer 3 UE relay can send a message to the source 5G ProSe Layer 3 UE indicating that there is an Ethernet MAC address conflict.

[0322] 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.

[0323] 5G ProSe layer 3UE inter-relay will select different source layer 2 IDs for PC5 links for different types of services, namely IP services, Ethernet services, and unstructured services.

[0324] If the PC5 link is used to transmit unstructured services, then the 5G ProSe layer 3 UE relay will select different source layer 2 IDs for different pairs of source and target 5G ProSe layer 3 end UEs.

[0325] Upon receiving the security establishment procedure message, the source 5G ProSe Layer 3 UE obtains the Layer 2 ID of the 5G ProSe Layer 3 UE relay for future communication, thereby enabling signaling and data services for this unicast link.

[0326] 5. After the security establishment procedure in step 4 is completed, the 5G ProSe Layer 3 UE-to-UE relay sends a direct communication request message to initiate a unicast Layer 2 link establishment procedure with the target 5G ProSe Layer 3 UE. The parameters included in the direct communication request message are described in section 6.4.3.7.

[0327] 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 is the unicast layer 2 ID of the target 5G ProSe layer 3 UE associated with the user information ID of the target 5G ProSe layer 3 UE.

[0328] 5G ProSe layer 3UE inter-relay will select different source layer 2 IDs for PC5 links for different types of services, namely IP services, Ethernet services, and unstructured services.

[0329] If the PC5 link is used to transmit unstructured services, then the 5G ProSe layer 3 UE relay will select different source layer 2 IDs for different pairs of source and target 5G ProSe layer 3 end UEs.

[0330] 6. If the target 5G ProSe Layer 3 UE's user information ID and the RSC included in the direct communication request match the target UE's user information ID and the RSC supported by the target UE, then the target 5G ProSe Layer 3 UE responds by establishing security with the 5G ProSe Layer 3 UE inter-relay. When security protection is enabled, the 5G ProSe Layer 3 UE inter-relay sends the parameters described in Section 6.4.3.7 to the target 5G ProSe Layer 3 UE.

[0331] 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.

[0332] 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 future communication, thereby enabling signaling and data services on this unicast link.

[0333] 7. The target 5G ProSe Layer 3 UE sends a direct communication accept message to the 5G ProSe Layer 3 UE inter-UE relay that has successfully established security. The parameters included in the direct communication accept message are described in Section 6.4.3.7.

[0334] 8. For IP services, assign an IPv6 prefix or IPv4 address to the target 5G ProSe Layer 3 UE, as defined in section 5.5.1.4.

[0335] 9. After receiving the 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 where security has been successfully established. The parameters included in the direct communication accept message are described in Section 6.4.3.7.

[0336] 10. For IP services, assign an IPv6 prefix or IPv4 address to the source 5G ProSe Layer 3 UE, as defined in section 5.5.1.4.

[0337] 11. For IP communication, the 5G ProSe Layer 3 UE inter-relay can store the association between the user information ID and the IP address of the target 5G ProSe Layer 3 UE in its DNS entries, and the 5G ProSe Layer 3 UE inter-relay can act as a DNS server for other UEs. If the IP address of the target 5G ProSe Layer 3 UE is not received in step 9, then after step 10, the source 5G ProSe Layer 3 UE can send a DNS query to the 5G ProSe Layer 3 UE inter-relay to request the IP address of the target 5G ProSe Layer 3 UE, and the 5G ProSe Layer 3 UE inter-relay will return the IP address of the target 5G ProSe Layer 3 UE to the source 5G ProSe Layer 3 UE.

[0338] 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.

[0339] For unstructured service communications, 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 with the source 5G ProSe layer 3 UE and the PC5 link with the target 5G ProSe layer 3 UE.

[0340] 12. The source 5G ProSe layer 3 UE communicates with the target 5G ProSe layer 3 UE via 5G ProSe layer 3 UE relay.

[0341] In the scenario where a source 5G ProSe Layer 3 UE communicates with multiple target 5G ProSe Layer 3 UEs, the PC5 link between the source 5G ProSe Layer 3 UE and the 5G ProSe Layer 3 UE inter-relay can be shared by multiple target 5G ProSe Layer 3 UEs for each RSC. Simultaneously, a separate PC5 link can be established between the 5G ProSe Layer 3 UE inter-relay and the target 5G ProSe Layer 3 UEs for each RSC. For shared PC5 links, a Layer 2 link modification procedure will be used.

[0342] When multiple source 5G ProSe Layer 3 UEs communicate with one target 5G ProSe Layer 3 UE, the PC5 link between the 5G ProSe Layer 3 UE relay and the target 5G ProSe Layer 3 UE can be shared for each RSC. Simultaneously, a separate PC5 link can be established between the source 5G ProSe Layer 3 UEs and the 5G ProSe Layer 3 UE relay for each RSC. For shared PC5 links, a Layer 2 link modification procedure will be used.

[0343] [...]

[0344] 6.7.1.4 Layer 2 Link Modification for PC5 Communication via 5G ProSe Layer 3 UE Inter-UE Relay

[0345] Figure 6 Section 7.1.4-1 illustrates the 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 Section 6.4.3.7.3.

[0346] The 3GPP TS23.304V18.2.0 standard includes a section titled "Modification Procedure for Layer 2 Links via Layer 3 Inter-UE Relays". Figure 6 .7.1.4-1 reproduced as Figure 12 ]

[0347] 0. UE-1 and UE-2 established a unicast link, as described in section 6.7.1.1.

[0348] 1. UE-1 sends a link modification request to the UE inter-relay, as described in section 6.4.3.7.3.

[0349] 2. After receiving the link modification request message from UE-1, the UE inter-relay sends the link modification request to UE-2, as described in section 6.4.3.7.3.

[0350] 3. UE-2 responds to the inter-UE relay with a link modification accept message, as described in section 6.4.3.7.3.

[0351] 4. After receiving the Link Modification Acceptance Message from UE-2, the UE Inter-Relay responds to UE-1 with the Link Modification Acceptance Message, as described in Section 6.4.3.7.3.

[0352] [...]

[0353] 6.7.2 5G ProSe Communication via 5G ProSe Layer 2 UE Inter-UE Relay

[0354] This program is applicable to 5G ProSe layer 2UE inter-UE relay.

[0355] The document titled "5G ProSe Communication via 5G ProSe Layer 2UE Inter-UE Relay" in 3GPP TS23.304V18.2.0... Figure 6 .7.2 -1 reproduced as Figure 13 ]

[0356] 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 section 6.2.

[0357] 1. Perform 5G ProSe UE inter-relay discovery as described in Section 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.

[0358] 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 Section 6.4.3.7 is used for inter-UE relay towards 5G ProSe; otherwise, the Layer 2 link establishment procedure is used for inter-UE relay towards 5G ProSe.

[0359] This procedure is directed toward the selected 5G ProSe UE inter-relay, and for Layer 2 link establishment, security establishment is performed before initiating step 3.

[0360] The 3.5G ProSe Layer 2 UE relay determines whether to use the existing PC5 link between the 5G ProSe UE 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 Section 6.4.3.7.

[0361] The target 5G ProSe end UE uses unicast layer 2 ID to execute this procedure.

[0362] 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.

[0363] 4. The source 5G ProSe UE establishes an end-to-end connection for unicast mode communication with the target 5G ProSe UE, as described in section 6.4.3.7.

[0364] Data is relayed between the source 5G ProSe UE and the target 5G ProSe UE via 5G ProSe Layer 2 UE relay. 5G ProSe Layer 2 UE relay forwards all data messages between the source 5G ProSe UE and the target 5G ProSe UE as specified in TS 38.300

[12] .

[0365] 6.7.3 integrates 5G ProSe UE-to-UE relay communication discovery.

[0366] 6.7.3.1 Overview

[0367] Supports integrated 5G ProSe communication via 5G ProSe UE relay with discovery.

[0368] For 5G ProSe inter-UE relay communication with integrated discovery, when a UE allows direct communication requests to other UEs involving inter-UE relay, the UE indicates this by including relay_indication in the broadcast direct communication request message.

[0369] When an inter-UE relay receives a direct communication request containing relay_indication, it determines whether to forward the message based on factors such as the relay service code (if present), application ID, operator policy for each relay service code, signal strength, and local policy.

[0370] 6.7.3.2 Procedure for communication via Layer 3 UE inter-relay

[0371] The document titled "Integrated Discovery 5G ProSe UE Inter-Relay Communication via Layer 3 UE Inter-Relay" is from 3GPP TS23.304V18.2.0. Figure 6 7.3.2-1 reproduced as Figure 14 ]

[0372] The 0.5G ProSe UE is authorized and supplied with parameters to use services provided by 5G ProSe UE-to-UE relay. The 5G ProSe UE-to-UE relay is authorized and supplied with parameters to provide relay services among 5G ProSe UEs.

[0373] 1. The source 5G ProSe UE (i.e., UE-1) wants to establish unicast communication with the target 5G ProSe UE (i.e., UE-2) and broadcasts a direct communication request. The parameters included in the direct communication request message are described in section 6.4.3.7.

[0374] The relay_indication in the direct communication request is used to indicate whether the 5G ProSe UE-to-UE relay can forward the direct communication request message. It is also used to limit the hop count of the 5G ProSe UE-to-UE relay by removing the relay_indication from the direct communication request message from the 5G ProSe UE-to-UE relay.

[0375] The source layer 2 ID and destination layer 2 ID used for direct communication request messages are defined in section 5.8.5.

[0376] Note 1: The data type of relay_indication can be determined in stage 3.

[0377] 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 included in the direct communication request message are described in section 6.4.3.7.

[0378] The source layer 2 ID and destination layer 2 ID used for direct communication request messages are defined in section 5.8.5.

[0379] 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).

[0380] 4. If necessary, security setup occurs between UE-2 and the selected 5G ProSe UE relay (relay-1 in this case).

[0381] If the existing PC5 link can be reused, then use the link modification request and link modification accept message.

[0382] Note 2: Conflicts between link modification requests and direct communication requests can be identified in phase 3.

[0383] 5. UE-2 replies to Relay-1 with a Direct Communication Acceptance Message. The parameters included in the Direct Communication Acceptance Message are described in Section 6.4.3.7.

[0384] 6. For IP services, assign an IPv6 prefix or IPv4 address to the target 5G ProSe Layer 3 UE, as defined in section 5.5.1.4.

[0385] 7. If necessary, security setup occurs between UE-1 and Relay-1.

[0386] 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.

[0387] 9. For 5G ProSe UE-to-UE relay communication with integrated discovery, UE-2 responds with a link modification acceptance message.

[0388] 10. Relay-1 responds to UE-1 using direct communication acceptance. The parameters included in the direct communication acceptance message are described in section 6.4.3.7.

[0389] 11. For IP services, assign an IPv6 prefix or IPv4 address to the source 5G ProSe Layer 3 UE, as defined in section 5.5.1.4.

[0390] 12. For IP communication, the 5G ProSe Layer 3 UE inter-relay can store the association between the user information ID and the IP address of the target 5G ProSe Layer 3 UE in its DNS entries, and the 5G ProSe Layer 3 UE inter-relay can act as a DNS server for other UEs. If the IP address of the target 5G ProSe Layer 3 UE is not received in step 10, then after step 11, the source 5G ProSe Layer 3 UE can send a DNS query to the 5G ProSe Layer 3 UE inter-relay to request the IP address of the target 5G ProSe Layer 3 UE, and the 5G ProSe Layer 3 UE inter-relay will return the IP address of the target 5G ProSe Layer 3 UE to the source 5G ProSe Layer 3 UE.

[0391] 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.

[0392] For unstructured service communications, 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 with the source 5G ProSe layer 3 UE and the PC5 link with the target 5G ProSe layer 3 UE.

[0393] The source 5G ProSe layer 3 UE communicates with the target 5G ProSe layer 3 UE via 5G ProSe layer 3 UE relay.

[0394] 6.7.3.3 Procedure for communication via Layer 2 UE inter-relay

[0395] The document titled "Integrated Discovery 5G ProSe UE Inter-Relay Communication via Layer 2 UE Inter-Relay" is from 3GPP TS23.304V18.2.0. Figure 6 .7.3.3 -1 reproduced as Figure 15 ]

[0396] Steps 0-5 and Figure 6 Steps 0-5 of .7.3.2-1 are the same. Step 6 is the same. Figure 6 Step 7 of .7.3.2-1 is the same.

[0397] Step 7 and Figure 6 Step 10 of .7.3.2-1 is the same. The parameters included in the message are described in section 6.4.3.7.

[0398] 8. For 5G ProSe UE-to-UE relay communication via Layer 2 UE-to-UE relay, UE-1 establishes an end-to-end connection for unicast mode communication with UE-2, as described in Section 6.4.3.7.

[0399] Editor's Note: This section will include any additional updates to procedures relayed between Layer 2 UEs, such as updates based on RAN decisions.

[0400] 3GPP TS24.554 introduces the following:

[0401] 7.2.2 5G ProSe Direct Link Establishment Procedure

[0402] 7.2.2.1 Overview

[0403] 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 TS23.304[2]), the 5G ProSe direct link establishment procedure is used to establish a 5G ProSe direct link between two UEs, or between a UE and multiple target UEs. The UE that sends the request message is called the “initiating UE”, and the other UEs are called “target UEs”. If the request message does not indicate a specific target UE (i.e., the target user information is not included in the request message) and multiple target UEs are interested in the ProSe application indicated in the request message, then 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 will not exceed the maximum number specified in the implementation scheme of the established 5G ProSe direct links.

[0404] Note 1: The maximum number of 5G ProSe direct links to be established is recommended to be 8.

[0405] When the 5G ProSe direct link establishment procedure for a 5G ProSe layer 3 remote UE is successfully completed, and if there is a PDU session established for relaying a 5G ProSe remote UE, the 5G ProSe layer 3 UE to the network relay UE shall perform the remote UE reporting procedure as specified in 3GPP TS24.501

[11] .

[0406] 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] .

[0407] 7.2.2.2 5G ProSe direct link establishment procedure initiated by the initiating UE

[0408] The following prerequisites must be met before initiating this procedure:

[0409] a) Requests from the upper layer transmit data packets for ProSe applications via PC5, or requests from the lower layer trigger the establishment of a ProSe direct link;

[0410] b) The communication mode is unicast (e.g., pre-configured as specified in section 5.2.4 or indicated by the upper layer);

[0411] c) The link layer identifier (i.e., the layer 2 ID for unicast communication) used to initiate the UE is available (e.g., pre-configured or self-assigned) and is not used by other existing 5G ProSe direct links within the initiating UE;

[0412] 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 section 5.2, known via previous ProSe direct communication, or indicated by the lower layer);

[0413] Note 1: In cases where different ProSe applications are mapped to different preset destination layer 2 IDs, when the initiating UE wishes to establish a single unicast link that can be used for more than one ProSe identifier, the UE can select any preset destination layer 2 ID for unicast initial signaling.

[0414] e) The UE is authorized to perform 5G ProSe direct communication on PC5 of NR-PC5 within the serving PLMN, has valid authorization for 5G ProSe direct communication on PC5 of NR-PC5 when not served by NG-RAN, is authorized to use 5GProSe UE-to-network relay UE, is authorized to use 5G ProSe inter-UE relay UE, or is authorized to act as a 5G ProSe inter-UE relay UE. The UE considers itself not to be served by NG-RAN if the following conditions are met:

[0415] 1) Direct ProSe communication on PC5 is not provided by NG-RAN service;

[0416] 2) The UE is in a limited service state as specified in 3GPP TS23.122

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

[0417] i) The UE cannot find a suitable cell in the selected PLMN, as specified in 3GPP TS 38.304

[15] ;

[0418] ii) The UE receives a registration rejection message or service rejection message with 5GMM reason #11 "PLMN not allowed", as specified in 3GPP TS24.501

[11] ; or

[0419] iii) The UE receives a registration rejection message or service rejection message with 5GMM reason #7 “5GS service not allowed”, as specified in 3GPP TS24.501

[11] ; or

[0420] 3) For reasons other than i), ii) or iii) above, the UE is in a limited service state as specified in 3GPP TS23.122

[14] and is located in a geographic area where the UE has “non-operator-managed” radio parameters as specified in section 5.2;

[0421] Editor's Note: The UE characteristics in the case of the 5G ProSe direct link establishment procedure for direct communication between the 5G ProSe terminal UE and the relay UE between the 5G ProSe UEs need to be re-discussed, which will be determined through SA2.

[0422] 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:

[0423] 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;

[0424] 2) The security policy (signaling security policy or user plane security policy) corresponding to the ProSe identifier is not compatible with the existing 5G ProSe direct link security policy; or

[0425] 3) In the case 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 relay UE in the network, the existing 5G ProSe direct link established for the peer UE has different RSCs, 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 relay UE in the network.

[0426] 4) In cases 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 relay UE in the network, an existing 5G ProSe direct link for the peer UE is established but not used for direct communication between the 5G ProSe Layer 2 remote UE and the 5G ProSe Layer 2 UE to a relay UE in the network; or;

[0427] 5) In the case where the 5G ProSe direct link establishment procedure is used for direct communication between 5G ProSe layer 3 end UE and 5G ProSe layer 3 UE relay UE, the existing 5G ProSe direct link established for peer UE has different RSCs, or is established but not used for direct communication between 5G ProSe layer 3 end UE and 5G ProSe layer 3 UE relay UE.

[0428] g) The number of 5G ProSe direct links established is less than the maximum number of 5G ProSe direct links allowed in the UE each time, as specified in the implementation scheme.

[0429] 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.

[0430] i) In the following situations: the UE acts as a 5G ProSe layer 3 inter-UE relay UE, a 5G ProSe direct link modification procedure is initiated on an existing 5G ProSe direct link for direct communication between the 5G ProSe layer 3 end UE and the 5G ProSe layer 3 inter-UE relay UE, and there is no existing 5G ProSe direct link between the 5G ProSe layer 3 inter-UE relay UE and the additional target 5G ProSe layer 3 end UE, a ProSe direct link modification request message is received from the 5G ProSe layer 3 end UE to establish 5G ProSe inter-UE relay communication with the additional 5G ProSe layer 3 end UE, as specified in section 7.2.3.2; and

[0431] j) The initiating UE has received a ProSe direct link establishment request message containing a relay indication, and the initiating UE acts as a 5G ProSe inter-UE relay UE. The 5G ProSe direct link establishment procedure is used for direct communication between the 5G ProSe inter-UE relay UE and the 5G ProSe terminal UE.

[0432] 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 Section 7.2.7.

[0433] 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, then the UE will apply either DUCK or DUSK, where an associated encrypted bitmask is used for UE-to-network relay discovery, and a UTC-based counter is used for encryption.

[0434] a) Relay service code; and

[0435] b) UP-PRUK ID or CP-PRUK ID (if available)

[0436] As specified in section 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.

[0437] Note 2: If the UE is neither configured to use DUCK nor DUSK, then the relay service code and UP-PRUK ID or CP-PRUK ID are not encrypted.

[0438] If the 5G ProSe direct link establishment procedure is used for direct communication between a 5G ProSe UE-to-UE relay UE and a target 5G ProSe end UE, and the initiating UE cannot identify an existing 5G ProSe direct link established between the initiating UE and the target UE after receiving the ProSe direct link establishment request message using integrated discovery (i.e., where the destination L2ID is set to the broadcast value specified in section 5.2.4 and a relay indication is included), then the initiating UE, acting as a 5G ProSe UE-to-UE relay UE, initiates a 5G ProSe direct link establishment procedure to the target 5G ProSe end UE.

[0439] If the 5G ProSe direct link establishment procedure is used for direct communication between a 5G ProSe UE relay UE and a target 5G ProSe UE, then without integration of discovery, after successfully completing the 5G ProSe direct link security mode control procedure with the source 5G ProSe UE, the initiating UE acting as the 5G ProSe UE relay UE initiates the 5G ProSe direct link establishment procedure to the target 5G ProSe UE.

[0440] Editor's Note: Further research is needed on when the direct link modification procedure can be used between the relay UE and the target 5G ProSe UE.

[0441] To initiate the 5G ProSe direct link establishment procedure, the initiating UE will create a ProSe direct link establishment request message. Initiating UE:

[0442] 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 ID of the source 5G ProSe end UE.

[0443] b) It will include the ProSe identifier received from the upper layer if 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.

[0444] c) The target user information, which is received from the upper layer or, if known based on the unicast layer 2 ID (i.e., destination layer 2 ID) of the target UE as described in section 5.8.2.4 of 3GPP TS23.304[3], is set to the application layer ID of the target UE, the user information ID of the 5G ProSe UE to network relay UE obtained during the 5G ProSe UE to network relay discovery procedure, or the user information ID of the target 5G ProSe terminal UE:

[0445] 1) If the initiating UE acts as the source 5G ProSe UE, and the target 5G ProSe UE's user information ID is obtained during the 5G ProSe UE inter-relay discovery procedure; or

[0446] 2) If the initiating UE acts as a 5G ProSe inter-UE relay UE, and the user information ID of the target 5G ProSe end UE is obtained in the ProSe direct link establishment request message or ProSe direct link modification request message from the source 5G ProSe end UE;

[0447] ca) will contain the inter-UE relay UE user information, including the user information ID set as a 5G ProSe inter-UE relay UE:

[0448] 1) If obtained during the 5G ProSe UE-to-UE relay discovery procedure, and the 5G ProSe direct link establishment procedure is used for 5G ProSe direct communication between the source 5G ProSe UE and the 5G ProSe UE-to-UE relay UE; or

[0449] 2) If the initiating UE acts 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 section 5.2.7;

[0450] cb) If the initiating UE acts as the source 5G ProSe end UE, and the layer 2 ID of the target 5G ProSe end UE is available in the source 5G ProSe end UE via previous direct communication, then the target end UE layer 2 ID will be included as the layer 2 ID of the target 5G ProSe end UE.

[0451] d) If the 5G ProSe direct link is not used for direct communication between the 5G ProSe remote UE and the 5G ProSe UE to the network relay UE:

[0452] 1) If the UE PC5 unicast signaling integrity protection policy is set to "need signaling integrity protection" or "prefer signaling integrity protection", then a key establishment information container will be included; and if the UE PC5 unicast signaling integrity protection policy is set to "do not require signaling integrity protection", then a key establishment information container may be included.

[0453] Note 3: The key establishment information container is provided by the upper layer.

[0454] e) will include:

[0455] 1) Nonce_1, provided that direct communication is not between the 5G ProSe remote UE and the 5G ProSe UE to the network relay UE, or provided that direct communication is between the 5G ProSe remote UE and the 5G ProSe UE to the network relay UE and the security procedures on the control plane are used as specified in 3GPP TS 33.503

[34] ;

[0456] 2)K NRP Freshness parameter 1, provided that direct communication is between a 5G ProSe remote UE and a 5G ProSe UE to a relay UE in the network and that the security procedures on the user plane are used as specified in 3GPP TS 33.503

[34] ;

[0457] If the UE PC5 unicast signaling integrity protection policy is set to "need signaling integrity protection" or "prefer signaling integrity protection", then for the purpose of establishing the session key through this 5G ProSe direct link, it is set to a 128-bit temporary value generated by the initiating UE.

[0458] Note 4: The Nonce_1IE in the ProSe direct link establishment request message is used to maintain the value of Nonce_1 or K. NRP Freshness parameter 1.

[0459] f) It will include its UE security capabilities, instructing the initiating UE to establish a list of supported algorithms for the security of this 5G ProSe direct link;

[0460] g) Will include the K selected by the initiating UE NRP-sess The MSB of the ID, as specified in 3GPP TS 33.503

[34] , is provided that the UE PC5 unicast signaling integrity protection policy is set to "requires signaling integrity protection" or "prefers signaling integrity protection";

[0461] Note 5: If the direct communication is not between the 5G ProSe remote UE and the 5G ProSe UE to the network relay UE, then K NRP-sessID remains corresponding to K NRP-sess The ID. If direct communication is between the 5G ProSe remote UE and the 5G ProSe UE to the network relay UE, then K NRP-sess ID remains corresponding to K NRP-sess (If a security program on the user plane is being used) or K relay-sess (If a security procedure on the control plane is used) ID.

[0462] h) may contain K NRP ID, provided that the initiating UE has an existing K for the target UE. NRP Furthermore, direct communication does not occur between the 5GProSe remote UE and the 5G ProSe UE to the network relay UE;

[0463] i) It will include its UE PC5 unicast signaling security policy. In cases where different ProSe applications are mapped to different PC5 unicast signaling security policies, when the initiating UE wants to establish a single unicast link usable for more than one ProSe application, each signaling security policy of these ProSe applications should be compatible; for example, "No signaling integrity protection required" and "Signaling integrity protection required" are incompatible. 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 relay UE in the network, the signaling integrity protection policy will be set to "Signaling integrity protection required."

[0464] j) Include a relay service code IE, which is set as the relay service code of the target relay UE in the case of direct communication between a 5G ProSe remote UE and a 5G ProSe UE to a relay UE in the network in the case of direct communication between a 5G ProSe remote UE and a 5G ProSe UE to a relay UE in the case of direct communication between a (source or target) 5G ProSe end UE and a 5G ProSe UE inter-relay UE in the case of direct communication between a 5G ProSe end UE and a 5G ProSe UE inter-relay UE;

[0465] 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 the 5G ProSe direct link establishment procedure for direct communication between 5G ProSe remote UE and 5G ProSe UE to network relay UE.

[0466] l) The IE containing the UE identity is set as the SUCI that initiated the UE in the following cases:

[0467] 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; and

[0468] 2) Security for 5G ProSe UE to network 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 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] ;

[0469] m) will contain the user security key ID IE, which is set as follows:

[0470] 1) Initiate UE's UP-PRUK ID, under the following conditions:

[0471] i) The 5G ProSe direct link establishment procedure is used for direct communication between 5G ProSe remote UEs and 5G ProSe UEs to network relay UEs;

[0472] ii) The initiating UE has a valid UP-PRUK; and

[0473] iii) Security for 5G ProSe UE-to-network relay uses user plane security procedures as specified in 3GPP TS 33.503

[34] ; or

[0474] 2) The CP-PRUK ID of the initiating UE associated with the relay service code of the target UE, provided that:

[0475] i) The 5G ProSe direct link establishment procedure is used for direct communication between 5G ProSe remote UEs and 5G ProSe UEs to network relay UEs;

[0476] ii) The initiating UE has a valid CP-PRUK associated with the relay service code of the target UE; and

[0477] iii) Security for 5G ProSe UE to network relay uses security procedures on the control plane, as specified in 3GPP TS 33.503

[34] ;

[0478] 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] );

[0479] 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 the 5G ProSe remote UE and the 5G ProSe UE to the network relay UE and the UE having a DUIK, as specified in section 6.3.5.3 of 3GPP TS 33.503

[34] ; and

[0480] p) will include a relay indication that the ProSe direct link establishment request message can be forwarded by a 5G ProSe UE-to-UE relay UE, provided that the 5G ProSe direct link establishment procedure is used for direct communication between the source 5G ProSe UE and the 5G ProSe UE-to-UE relay UE.

[0481] Editor's Note: The security parameters for 5G ProSe inter-UE relay and the parameters for 5G ProSe layer 2 inter-UE relay require further investigation.

[0482] After the ProSe direct link establishment request message is generated, the initiating UE transmits this message along with the source stratum 2ID and destination stratum 2ID to the lower layer for transmission, as follows:

[0483] a) If 5G ProSe direct communication is due to 5G ProSe direct discovery as defined in Sections 6.2.14, 6.2.15, 8.2.1 and 8a.2.1:

[0484] Assign source layer 2 ID yourself, and

[0485] 1) Destination Layer 2 ID, which is set to the target UE Layer 2 ID received in the ProSe Direct Link Establishment Request Message or ProSe Direct Link Modification Request Message from the source 5G ProSe UE, provided that the initiating UE acts as a 5G ProSe inter-UE relay UE.

[0486] 2) Otherwise, set the destination layer 2 ID to the source layer 2 ID in the received ProSe PC5 discovery message used for the discovery procedure;

[0487] b) If the initiating UE acts as the source 5G ProSe UE, and the 5G ProSe direct link establishment procedure for integration between the source 5G ProSe UE and the relay UE between the 5G ProSe UEs has discovered direct communication:

[0488] Assign a source layer 2 ID and set the destination layer 2 ID to the broadcast destination layer 2 ID configured as specified in section 5.2.4; or

[0489] c) If the initiating UE acts as a 5G ProSe inter-UE relay UE, and the 5G ProSe direct link establishment procedure for integration between the 5G ProSe inter-UE relay UE and the target 5G ProSe end UE has discovered direct communication:

[0490] Assign a source layer 2 ID and set the destination layer 2 ID as follows:

[0491] 1) Target UE Layer 2 ID, if received in the ProSe direct link establishment request message from the source 5G ProSe UE; otherwise

[0492] 2) Broadcast destination layer 2 ID configured as specified in section 5.2.4; or

[0493] d) Otherwise:

[0494] Assign a source layer 2 ID and a destination layer 2 ID set to be used for the unicast initiation signaling specified in section 5.2.4.

[0495] Note 6: The UE implementation ensures that any value of the self-assigned source layer 2 ID in a) and b) is different from any other self-assigned source layer 2 ID used for direct discovery of 5G ProSe as specified in Sections 6.2.14, 6.2.15 and 8.2.1, and different from any other destination layer 2 ID provided as specified in Section 5.2.

[0496] Note 6A: The UE implementation scheme ensures that any value of the source layer 2 ID assigned by the user in a) and b) is different from any source layer 2 ID assigned by the user when using 5G ProSe direct communication with a data unit type different from the data unit type of the established 5G ProSe direct link, if the 5G ProSe direct link establishment procedure is used for 5G ProSe direct communication between a 5G ProSe layer 3 UE relay UE and a target 5G ProSe layer 3 end UE.

[0497] Note 6B: The UE implementation scheme ensures that any value of the source layer 2 ID assigned in a) and b) is different from any other self-assigned source layer 2 ID and different user information ID of the source 5G ProSe end UE and the target 5G ProSe end UE when using 5G ProSe direct link establishment procedure for 5G ProSe layer 3 UE inter-UE relay UE and target 5G ProSe layer 3 end UE for unstructured services.

[0498] 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 IDs of the source 5G ProSe UE and the target 5G ProSe UE are different, and 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 with a data unit type different from the data unit type of the previous 5G ProSe direct link.

[0499] And start timer T5080.

[0500] 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] .

[0501] When 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), then the initiating UE will process multiple ProSe direct link establishment acceptance messages (if any) received from different target UEs to establish multiple 5G ProSe direct links before timer T5080 expires.

[0502] 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.

[0503] The document titled "5G ProSe Direct Link Establishment Procedure for UE" in 3GPP TS24.554V18.1.0 Figure 7 2.2.2.1 Reproduced as Figure 16 ]

[0504] The document titled "5G ProSe Direct Link Establishment Procedure for ProSe Services" in 3GPP TS24.554V18.1.0 Figure 7 2.2.2.2 Reproduced as Figure 17 ]

[0505] 7.2.2.3 5G ProSe Direct Link Establishment Procedure Accepted by the Target UE

[0506] 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.

[0507] 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] .

[0508] If the ProSe direct link establishment request message is for 5G ProSe direct communication between a 5G ProSe remote UE and a 5G ProSe UE to a relay UE in the network, then the target UE will verify the MIC field in the received ProSe direct link establishment request with DUIK (if present) and decrypt the encrypted message using DUCK or DUSK.

[0509] a) Relay service code; and

[0510] b) UP-PRUK ID or CP-PRUK ID (if received),

[0511] The associated encrypted bitmask is used for relay discovery of the 5G ProSe UE to the network (see section 6.3.5.2 of 3GPP TS33.503

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

[0512] Note 2: If the UE is neither configured to use DUCK nor DUSK, then the relay service code and UP-PRUK ID or CP-PRUK ID are not encrypted.

[0513] If the target UE acts as the target 5G ProSe end UE, and the 5G ProSe direct link establishment procedure is used for the integration discovery of 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 one of the 5G ProSe inter-UE relay UEs to communicate with the source 5G ProSe end UE, as specified in section 6.7.3.2 of TS23.304.

[0514] If the 5G ProSe direct link establishment procedure is not used for direct communication between the 5G ProSe remote UE and the 5G ProSe UE to the network relay UE, then the target UE may initiate the 5G ProSe direct link authentication procedure specified in section 7.2.12 and will initiate the 5G ProSe direct link security mode control procedure specified in section 7.2.10.

[0515] 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 a relay UE in the network, then the target UE will continue:

[0516] a) Authentication and key negotiation procedures, as specified in section 5.5.4 of 3GPP TS24.501

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

[34] are used; or

[0517] b) A key request procedure, as specified in section 8.2.10.2.4, provided that a security procedure on the user plane as specified in 3GPP TS 33.503

[34] is used;

[0518] And will initiate the 5G ProSe direct link security mode control procedure, as specified in section 7.2.10.

[0519] In the 5G ProSe direct link context, the target UE will set the source 2ID and destination 2ID as specified in Sections 7.2.12 and 7.2.10, and store the corresponding source 2ID for unicast communication and the destination 2ID for unicast communication.

[0520] if:

[0521] 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

[0522] 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;

[0523] Next, the target UE will:

[0524] a) If direct communication is not between a 5G ProSe remote UE and a 5G ProSe UE to a network relay UE:

[0525] 1) Based on K contained in the ProSe direct link establishment request message NRP ID, identifying existing K NRP ;or

[0526] 2) If K NRP If the ID is not included in the ProSe direct link establishment request message, then the target UE targets the K included in the ProSe direct link establishment request message. NRP ID does not have an existing K NRP Or the target UE wants to export a new K NRP This may require performing one or more 5G ProSe direct link authentication procedures, as specified in section 7.2.12;

[0527] b) If the direct communication is between a 5G ProSe remote UE and a 5G ProSe UE to a network relay UE and uses the security procedures on the control plane specified in 3GPP TS 33.503

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

[34] . NR_ProSe ;or

[0528] c) If the direct communication is between a 5G ProSe remote UE and a 5G ProSe UE to a network relay UE and uses the user plane security procedure specified in 3GPP TS 33.503

[34] , then request a new K according to the user plane security procedure. NRP .

[0529] Note 3: 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.

[0530] In identifying existing K NRP Or export a new K NRP Afterwards, or upon receiving a new K NRP or K NR_ProSe Subsequently, the target UE will initiate the 5G ProSe direct link security mode control procedure, as specified in section 7.2.10.

[0531] 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 verifies whether there is at least one public IP address configuration option supported by both the initiating UE and the target UE.

[0532] Before sending the ProSe direct link establishment accept message to the 5G ProSe remote UE, the target UE, acting as a relay UE from the 5G ProSe layer 3 UE to the network, initiates the PDU session establishment procedure requested by the UE, as specified in 3GPP TS24.501

[11] , under the following conditions:

[0533] 1) The PDU session for relaying services associated with RSC has not yet been established; or

[0534] 2) A PDU session for relaying services associated with RSC has been established, but the PDU session type is unstructured.

[0535] If the target UE accepts the 5G ProSe direct link establishment procedure, then the target UE will create a ProSe direct link establishment accept message. Target UE:

[0536] a) The source user information is set as the application layer ID of the target UE received from the upper layer, or as the user information ID of the target 5G ProSe UE in the case of 5G ProSe direct link establishment procedure used for 5G ProSe end UE and 5G ProSe UE inter-relay UE 5G ProSe direct communication.

[0537] aa) The UE user information contained in the UE inter-relay UE will be set as the 5G ProSe UE inter-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-relay UE.

[0538] b) Includes PQFI, the corresponding PC5 QoS parameters, and the optional ProSe identifier accepted by the target UE if the target UE does not act as a relay UE to the network for 5G ProSe layer 2 UE, and the 5G ProSe direct link establishment procedure does not integrate discovery and is not used for 5G ProSe direct communication between the target 5G ProSe end UE and the 5G ProSe UE relay UE.

[0539] c) It may include PC5 QoS rules, provided that the target UE does not act as a relay UE from the 5G ProSe layer 2 UE to the network, and the 5G ProSe direct link establishment procedure is not integrated with discovery and is not used for 5G ProSe direct communication between the target 5G ProSe end UE and the 5G ProSe UE relay UE.

[0540] Editor's Note: Further research is needed on how to forward PC5 QoS streams between 5G ProSe Layer 3 UEs, specifically the PC5 QoS parameters and PQFI.

[0541] d) If IP communication is used and the target UE does not act as a relay UE to the network in a 5G ProSe Layer 2 UE, then the IE will be configured with an IP address set to one of the following values:

[0542] 1) "DHCPv4 server", provided that only the IPv4 address allocation mechanism is supported by the target UE, that is, it acts as a DHCPv4 server;

[0543] 2) "IPv6 router", provided that only the IPv6 address allocation mechanism is supported by the target UE, that is, it acts as an IPv6 router;

[0544] 3) "DHCPv4 server and IPv6 router", provided that both IPv4 and IPv6 address allocation mechanisms are supported by the target UE; or

[0545] 4) Address allocation is not supported, provided that neither IPv4 nor IPv6 address allocation mechanisms are supported by the target UE and the target UE does not act as a relay UE from a 5G ProSe layer 3 UE to the network;

[0546] Note 4: If communication uses Ethernet or unstructured data unit type, then the UE does not include an IP address configuration IE, nor does it include a link-local IPv6 address IE.

[0547] e) If 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 is neither a 5G ProSe layer 2 UE to network relay UE nor a 5G ProSe layer 3 relay UE, then it will contain the link-local IPv6 address IE formed locally based on IETF RFC 4862

[25] .

[0548] 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] ;

[0549] Editor's Note: The security parameters for 5G ProSe inter-UE relay and the parameters for 5G ProSe layer 2 inter-UE relay require further investigation.

[0550] g) If the 5G ProSe direct link establishment procedure is used for 5G ProSe direct communication between a source or target 5G ProSe Layer 3 UE and a relay UE between 5G ProSe Layer 3 UEs and for Ethernet services, then it will include the MAC address of the target 5G ProSe Layer 3 UE; and

[0551] 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, if 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.

[0552] Editor's Note: The security parameters for 5G ProSe inter-UE relay and the parameters for 5G ProSe layer 2 inter-UE relay require further investigation.

[0553] After the ProSe direct link establishment accept message is generated, 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, under the condition that:

[0554] a) At least one ProSe identifier used for the 5G ProSe direct link satisfies the privacy requirements specified in section 5.2.4; or

[0555] b) Configure the T5090 as specified in section 5.2.5.

[0556] Note 5: 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 / destination layer 2ID configurations in the AS layer, as specified in 3GPP TS 38.300

[21] .

[0557] 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:

[0558] a) The PC5 link identifier assigned by the user for this 5G ProSe direct link;

[0559] b) PQFI and its corresponding PC5 QoS parameters (if available); and

[0560] c) Instructions to activate PC5 unicast user plane security protection for 5G ProSe direct links (if applicable).

[0561] 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 a network relay UE, and not used for 5G ProSe direct communication between a 5G ProSe end UE and a 5G ProSe UE inter-relay UE, then the target UE can perform PC5 QoS flow establishment on the 5G ProSe direct link, as specified in section 7.2.7. If the 5G ProSe direct link is established for 5G ProSe layer 3 remote UE and a 5G ProSe layer 3 UE to a network relay UE, then the target UE can perform PC5 QoS flow establishment on the 5G ProSe direct link, as specified in section 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 inter-relay UE, then the target UE can perform PC5 QoS flow establishment on the 5G ProSe direct link, as specified in section 8a.2.7.

[0562] 7.2.2.4 The 5G ProSe direct link establishment procedure initiated by the UE is completed.

[0563] 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.

[0564] For each received ProSe direct link establishment accept message, 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 will store the source layer 2 ID and destination layer 2 ID in the 5G ProSe direct link context for transmitting this message provided by the lower layer, thus completing the establishment of the 5G ProSe direct link with the target UE. From then on, the initiating UE will use the established link for ProSe direct communication on PC5 and for additional PC5 signaling messages to the target UE.

[0565] If the initiating UE acts as a 5G ProSe inter-UE relay and the 5G ProSe direct link establishment procedure is used for the integration between the 5G ProSe inter-UE relay UE and the target 5G ProSe end UE with direct communication discovery, then after receiving the ProSe direct link establishment accept 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, and 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 accept message as specified in section 7.2.2.3 to send to the source 5G ProSe end UE.

[0566] 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:

[0567] a) The PC5 link identifier assigned by the user for this 5G ProSe direct link;

[0568] b) PQFI and its corresponding PC5 QoS parameters (if available); and

[0569] c) Instructions to activate PC5 unicast user plane security protection for 5G ProSe direct links (if applicable).

[0570] The UE will initiate timer T5090 under the following conditions:

[0571] a) At least one ProSe identifier used for the 5G ProSe direct link satisfies the privacy requirements specified in section 5.2.4; or

[0572] b) Configure the T5090 as specified in section 5.2.5.

[0573] In addition, the initiating UE can perform PC5QoS flow establishment on the 5G ProSe direct link as specified in section 7.2.7.

[0574] If, after timer T5080 expires, the ProSe direct link establishment request message does not contain the target user information IE and the initiating UE receives at least one ProSe direct link establishment acceptance message, then whether to consider the 5G ProSe direct link establishment procedure as completed or to restart timer T5080 is determined by the UE implementation plan.

[0575] 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 section 7.2.3.2, then when the initiating UE acts as a relay UE between 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 section 7.2.3.3.

[0576] 7.2.2.5 5G ProSe direct link establishment procedure not accepted by the target UE

[0577] If the ProSe direct link establishment request message cannot be accepted, the target UE will send a ProSe direct link establishment rejection message. The ProSe direct link establishment rejection message contains a PC5 signaling protocol reason IE, which is set to one of the following reason values:

[0578] #1 Direct communication with the target UE is not allowed;

[0579] #3 A collision of Layer 2 IDs used for unicast communication was detected;

[0580] #5 Lack of resources for 5G ProSe direct links;

[0581] #13 Congestion situation;

[0582] #15 Security procedure failure in 5G ProSe UE to network relay;

[0583] #20 Fault originating from the 5G ProSe UE; or

[0584] #111 Unspecified protocol error.

[0585] If the target UE is not permitted to accept ProSe direct link establishment request messages, for example, based on operator policies or configuration parameters for ProSe direct communication on PC5 as specified in section 5.2, or if the target UE acts as a relay UE to the network for a 5G ProSe layer 3 UE, in an unacceptable area of ​​its serving PLMN and the corresponding relay service code is not associated with high priority access, as defined in section 5.3.5 of 3GPP TS 24.501

[11] , then the target UE will send a ProSe direct link establishment denial message containing the PC5 signaling protocol reason value #1 "Direct communication with the target UE is not permitted".

[0586] Note 1: When a target UE acting as a relay UE to the network is involved in its own emergency service as specified in 3GPP TS 24.501

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

[0587] For a ProSe direct link establishment request message (used for unicast communication) received from a Layer 2 ID, if the target UE has already established an existing link to the UE using this Layer 2 ID or is currently processing a ProSe direct link establishment request message from the same Layer 2 ID and one of the following parameters differs from an existing link or a link establishment in progress:

[0588] a) Source user information;

[0589] b) The type of data (e.g., IP, Ethernet, or unstructured); or

[0590] c) Security strategy

[0591] The target UE will send a ProSe direct link establishment rejection message containing the PC5 signaling protocol reason value #3 "A conflict was detected with the Layer 2 ID used for unicast communication".

[0592] Note 2: If the UE is processing a ProSe Direct Discovery message with the same source stratum 2 ID from a received ProSe Direct Link Establishment Request message, then avoiding destination stratum 2 ID conflicts depends on the UE implementation scheme (e.g., sending a ProSe Direct Link Establishment Reject message containing the PC5 signaling protocol reason value #3 "Conflict detected in stratum 2 ID for unicast communication" or ignoring the ProSe Direct Discovery message).

[0593] Note 3: The data type (e.g., IP, Ethernet, or unstructured) is indicated by an optional IP address configuration IE included in the corresponding direct link security mode completion message. That is, if this IE is included, the data type of the requested link is IP, and if this IE is not included, the data type of the requested link is Ethernet or unstructured.

[0594] If the establishment of a 5G ProSe direct link fails due to the maximum number of 5G ProSe direct links being reached as specified in the implementation scheme or other temporary lower-layer issues causing resource constraints, the target UE should send a ProSe direct link establishment rejection message containing the PC5 signaling protocol reason value #5 "Lack of resources for 5G ProSe direct link".

[0595] If the 5G ProSe direct link establishment request is for relaying from the 5G ProSe UE to the network and:

[0596] a) Activate NAS-level mobility management congestion control as specified in section 5.3.9 of TS24.501

[11] at the target UE acting as a relay UE from the 5G ProSe UE to the network; or

[0597] b) The target UE acting as a relay UE to the network for the 5G ProSe UE is under congestion;

[0598] The target UE will send a ProSe direct link establishment rejection message containing the PC5 signaling protocol reason value #13 "Congestion Situation". The target UE may provide a backoff timer value to the initiating UE in the ProSe direct link establishment rejection message. If the backoff timer used for NAS-level mobility management congestion control is running, the target UE will not accept any 5G ProSe direct link establishment requests for relay.

[0599] If a 5G ProSe direct link establishment request is used for a 5G ProSe UE to network relay, and NAS-level session management congestion as specified in sections 6.2.7 and 6.2.8 of TS24.501

[11] is activated at the target UE acting as the relay UE for the 5G ProSe layer 3 UE to network, the relay service code for 5G ProSe direct link establishment corresponds to the DNN and / or S-NSSAI in which NAS-level session management congestion is activated, and the target UE needs to execute a PDU session establishment procedure for the DNN and / or S-NSSAI or a PDU session modification procedure for the DNN and / or S-NSSAI, then the target UE will send a ProSe direct link establishment rejection message containing the PC5 signaling protocol reason value #13 "Congestion Situation". The target UE may provide a backoff timer value to the initiating UE in the ProSe direct link establishment rejection message.

[0600] Note 4: How the target UE determines that it is under congestion is implementation-specific (e.g., any relay-related operational overhead, etc.).

[0601] Note 5: When the target UE is under NAS-level mobility management congestion control, setting the backoff timer value provided to the initiating UE to the remaining time of the mobility management backoff timer T3346 or with an additional offset value is an implementation option.

[0602] If the 5G ProSe direct link establishment request is for a 5G ProSe layer 3 UE to network relay, the request requires the 5G ProSe layer 3 UE to establish a PDU session as a relay UE to the network, and the PDU session establishment fails due to receiving 5GSM reasons #8 "Maximum number of PDU sessions reached", #27 "DNN missing or unknown", #28 "PDU session type unknown", #29 "User authentication or authorization failed", #31 "Unspecified rejection request", #32 "Service option not supported", #33 "Requested service option not subscribed" or #65 "Maximum number of PDU sessions reached", as specified in 3GPP TS24.501

[11] , then the target UE will send a ProSe direct link establishment rejection message containing the PC5 signaling protocol reason value #111 "Unspecified protocol error".

[0603] If the 5G ProSe direct link establishment request is for 5G ProSe UE-to-UE relay, and:

[0604] a) The target UE, acting as the target 5G ProSe terminal UE, is under congestion;

[0605] The target UE will send a ProSe direct link establishment rejection message containing the PC5 signaling protocol reason value #13 "Congestion Situation". The target UE can provide a backoff timer value to the initiating UE in the ProSe direct link establishment rejection message.

[0606] After receiving a ProSe direct link establishment rejection message from the target 5G ProSe UE, the initiating UE acts as a 5GProSe inter-UE relay UE, and the 5G ProSe direct link establishment procedure is used for direct communication between the source 5G ProSe UE and the 5G ProSe inter-UE relay UE. The target 5G ProSe UE has rejected the 5G ProSe direct link establishment procedure or the 5G ProSe direct link modification procedure. The rejection message contains a backoff value. The initiating UE has not yet reached the maximum number of allowed retransmissions. The initiating UE will notify (message TBD) the source 5G ProSe UE that the target 5G ProSe UE has rejected the link establishment or link modification request, and will provide a reason value from the target 5G ProSe UE.

[0607] Editor's Note: Further research is needed on how the target 5G ProSe end UE should notify the 5G ProSe UE relay UE that has rejected the link establishment or link modification request.

[0608] After receiving a ProSe direct link establishment rejection message from the target 5G ProSe UE, the initiating UE acts as a 5GProSe inter-UE relay UE. The 5G ProSe direct link establishment procedure is used for direct communication between the source 5G ProSe UE and the 5G ProSe inter-UE relay UE. If the target 5G ProSe UE has rejected the 5G ProSe direct link establishment procedure or the 5G ProSe direct link modification procedure, the rejection message contains a backoff value, and the initiating UE has reached the maximum allowed number of retransmissions, the initiating UE can send a ProSe direct link establishment rejection message with an appropriate PC5 signaling protocol reason value to the source 5G ProSe UE. The initiating UE will include the PC5 protocol reason value #xx "Fault from 5G ProSe UE" in the ProSe direct link establishment rejection message, and will also include the PC5 UE fault reason IE set to #13 "Congestion Condition" received from the target 5G ProSe UE that has rejected the 5G ProSe direct link establishment or the 5G ProSe direct link modification procedure. The initiating UE can include the target UE information IE, which is set as the user information ID of the target 5G ProSe UE, in the ProSe direct link establishment rejection message.

[0609] If the 5G ProSe direct link establishment request is for 5G ProSe UE-to-UE relay, and:

[0610] a) The target UE acting as a relay UE between 5G ProSe UEs is under congestion;

[0611] The target UE will send a ProSe direct link establishment rejection message containing the PC5 signaling protocol reason value #13 "Congestion Situation". The target UE can provide a backoff timer value to the initiating UE in the ProSe direct link establishment rejection message.

[0612] 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 a network relay UE and fails due to a security procedure failure on the control plane or user plane, as specified in 3GPP TS 33.503

[34] , then the target UE will send a ProSe direct link establishment rejection message containing the PC5 signaling protocol cause value #15 "5G ProSe UE to network relay security procedure failure". The target UE will provide an EAP message (if received from the network) according to the security procedure on the control plane as specified in 3GPP TS 33.503

[34] .

[0613] If the target UE acts as the target 5G ProSe end UE and the 5G ProSe direct link establishment procedure is between the 5G ProSe UE relay UE and the target 5G ProSe end UE, then the target 5G ProSe end UE may include the following in the ProSe direct link establishment rejection message:

[0614] a) Set the source UE information IE to the user information ID of the source 5G ProSe UE;

[0615] b) Target UE information IE set as the user information ID of the target 5G ProSe terminal UE; and

[0616] c) Set as the UE information IE of the user information ID of the 5G ProSe UE-to-UE relay UE.

[0617] If the target UE acts as a 5G ProSe inter-UE relay UE, the 5G ProSe direct link establishment procedure is between the source 5G ProSe UE and the 5G ProSe inter-UE relay UE, and the target 5G ProSe UE has rejected the 5G ProSe direct link establishment procedure or the 5G ProSe direct link modification procedure, then the 5G ProSe inter-UE relay UE will send a ProSe direct link establishment rejection message with the PC5 signaling protocol reason value #20 "Fault from 5G ProSe UE" to the source 5G ProSe UE. The 5G ProSe inter-UE relay UE may include the PC5 UE fault reason IE in the ProSe direct link establishment rejection message, which is set to the PC5 signaling protocol reason received from the target 5G ProSe UE that has rejected the 5G ProSe direct link establishment procedure. The 5G ProSe inter-UE relay UE may include the following in the ProSe direct link establishment rejection message:

[0618] a) Set the source UE information IE to the user information ID of the source 5G ProSe UE;

[0619] b) Target UE information IE set as the user information ID of the target 5G ProSe terminal UE; and

[0620] c) Set as the UE information IE of the user information ID of the 5G ProSe UE-to-UE relay UE.

[0621] Note 6: When CP-PRUK or UP-PRUK is not found in the network, the cause value #15 "5GProSe UE to network relay security procedure failure" is also used.

[0622] If the 5G ProSe direct link establishment fails for other reasons, the target UE will send a ProSe direct link establishment rejection message containing the PC5 signaling protocol reason value #111 "Unspecified protocol error".

[0623] After sending the ProSe direct link establishment rejection message, the target UE will provide the following information to the lower layer, as well as the Layer 2 ID of the initiating UE for unicast communication and the Layer 2 ID of the target UE for unicast communication:

[0624] a) Instructions for revoking activation of PC5 unicast security protection and deleting security contexts for 5G ProSe direct links (if applicable).

[0625] Upon receiving a ProSe direct link establishment rejection message, the initiating UE will stop timer T5080 and abort the 5G ProSe direct link establishment procedure. If the PC5 signaling protocol reason value in the ProSe direct link establishment rejection message is #1 "Direct communication with the target UE is not allowed" or #5 "Lack of resources for 5G ProSe direct link", then the initiating UE will not attempt to initiate a 5G ProSe direct link establishment procedure with the same target UE for at least time period T. If the PC5 signaling protocol reason value in the ProSe direct link establishment rejection message is #13 "Congestion" and a backoff timer value is provided in the ProSe direct link establishment rejection message, then the initiating UE will start timer T5088 associated with the target UE's Layer 2 ID and set its value to the provided timer value. If the PC5 signaling protocol reason value in the ProSe direct link establishment rejection message is #15 "5G ProSe UE to Network Relay Security Procedure Failure", and the initiating UE has included a UE identity IE set to SUCI in the ProSe direct link establishment request message, then the initiating UE will initiate a UE to network relay reselection procedure as specified in Section 8.2.3. If the PC5 signaling protocol reason value in the ProSe direct link establishment rejection message is #15 "5G ProSe UE to Network Relay Security Procedure Failure", and the initiating UE has included a user security key ID IE set to UP-PRUK ID or CP-PRUK ID in the ProSe direct link establishment request message, then the initiating UE may initiate a UE to network relay reselection procedure as specified in Section 8.2.3, and the UE will further:

[0626] a) If the same 5G ProSe UE-to-network relay UE is selected, then discard the previously used CP-PRUK and associated CP-PRUK ID, or UP-PRUK and associated UP-PRUK ID (if present), and include the UE identity IE set to SUCI in the ProSe direct link establishment request when initiating subsequent 5G ProSe direct link establishment procedures, as specified in section 7.2.2.2; or

[0627] b) If a different 5G ProSe UE to network relay UE is selected, the ProSe direct link establishment request message includes the user security key ID IE set to the previously used UP-PRUK ID or CP-PRUK ID.

[0628] Note 7: The length of time period T is specific to the UE implementation scheme and may differ when the UE receives PC5 signaling protocol cause value #1 "Direct communication with the target UE is not allowed" or when the UE receives PC5 signaling protocol cause value #5 "Lack of resources for 5GProSe direct link".

[0629] Editor's Note: Security-related content requires further research and depends on SA3 requirements.

[0630] Upon receiving the ProSe direct link establishment rejection message, the initiating UE will provide the following information to the lower layer, as well as the Layer 2 ID of the initiating UE for unicast communication and the Layer 2 ID of the target UE for unicast communication:

[0631] a) Instructions for revoking activation of PC5 unicast security protection and deleting security contexts for 5G ProSe direct links (if applicable).

[0632] 7.2.2.6 Abnormal situations

[0633] 7.2.2.6.1 Initiating Abnormal Situations at the UE

[0634] If timer T5080 expires and the target user information IE is included in the ProSe direct link establishment request message, the initiating UE will retransmit the ProSe direct link establishment request message and restart timer T5080. After reaching the maximum allowed number of retransmissions, the initiating UE will abort the 5G ProSe direct link establishment procedure and may notify the upper-layer target UE that it is unreachable.

[0635] If, after timer T5080 expires, the ProSe direct link establishment request message does not contain the target user information (IE) and the initiating UE does not receive any ProSe direct link establishment acceptance messages, the initiating UE can retransmit the ProSe direct link establishment request message and restart timer T5080. If the ProSe direct link establishment request message does not contain the target user information (IE) and the initiating UE does not receive any ProSe direct link establishment acceptance messages, the initiating UE will terminate the 5G ProSe direct link establishment procedure after reaching the maximum allowed number of retransmissions and can notify the upper-layer target UE that the 5G ProSe direct link establishment procedure is unavailable.

[0636] Note: The maximum number of retransmissions allowed is specific to the UE implementation scheme.

[0637] If a link is no longer needed before the procedure is completed, the initiating UE will terminate the procedure.

[0638] When the initiating UE terminates the 5G ProSe direct link establishment procedure, the initiating UE will provide the following information to the lower layer, as well as the Layer 2 ID of the initiating UE for unicast communication and the Layer 2 ID of the target UE for unicast communication:

[0639] a) Instructions for revoking activation of PC5 unicast security protection and deleting security contexts for 5G ProSe direct links (if applicable).

[0640] 7.2.2.6.2 Abnormal situations at the target UE

[0641] For a ProSe direct link establishment request message (used for unicast communication) received from a source layer 2 ID, if the target UE already has an existing link to a known UE using the same source layer 2 ID, the same source user information, the same data type (IP, Ethernet, or unstructured), and the same security policy, then the UE will process the new request. However, the target UE will only delete the existing 5G ProSe direct link context after the new link establishment procedure is successful.

[0642] Note: The data type (e.g., IP, Ethernet, or unstructured) is indicated by the optional IP address configuration included in the corresponding ProSe direct link security mode completion message. That is, if this IE is included, the data type of the requested link is IP, and if this IE is not included, the data type of the requested link is Ethernet or unstructured.

[0643] 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, then after the target UE decrypts the encrypted relay service code (where the associated encrypted bitmask is used for 5G ProSe UE-to-network relay discovery) using DUIK, DUSK, or DUCK, if the relay service code does not match the relay service code sent by the target UE during the 5G ProSe UE-to-network relay discovery procedure, then the target UE will abort the 5G ProSe direct link establishment procedure.

[0644] If a 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 a relay UE in the network, message integrity is protected, and message integrity verification fails at the target UE, then the target UE will abort the 5G ProSe direct link establishment procedure.

[0645] 7.2.3 5G ProSe Direct Link Modification Program

[0646] 7.2.3.1 Overview

[0647] The purpose of the 5G ProSe direct link modification procedure is to modify the existing ProSe direct link to:

[0648] a) Add new PC5 QoS flows to existing 5G ProSe direct links;

[0649] b) Modify existing PC5 QoS flows to update the PC5 QoS parameters of existing PC5 QoS flows;

[0650] c) Modify existing PC5 QoS flows to associate the new ProSe application with existing PC5 QoS flows;

[0651] d) Modify an existing PC5 QoS stream to remove the associated ProSe application from the existing PC5 QoS stream;

[0652] e) Remove existing PC5 QoS flows from existing 5G ProSe direct links;

[0653] f) Negotiate new 5G ProSe UE-to-UE relay UEs on existing 5G ProSe direct links;

[0654] g) Establish 5G ProSe UE-to-UE relay communication with additional 5G ProSe UEs using the existing 5G ProSe direct link between 5G ProSe Layer 3 UEs and 5G ProSe Layer 3 UE-to-UE relay UEs; or

[0655] h) Use the shared 5G ProSe direct link between the 5G ProSe Layer 3 end UE and the 5G ProSe Layer 3 inter-UE relay UE to release 5G ProSe inter-UE relay communication with one of the peer 5G ProSe Layer 3 end UEs.

[0656] In this procedure, the UE that sends the ProSe direct link modification request message is called the "initiating UE", and the other UE is called the "target UE".

[0657] Note: The 5G ProSe direct link modification procedure is not applicable to the case of 5G ProSe layer 2 UE to network relay.

[0658] 7.2.3.2 5G ProSe Direct Link Modification Procedure Initiated by the UE

[0659] Before initiating this procedure to add a new ProSe application to an existing 5G ProSe direct link, the following prerequisites must be met:

[0660] a) A 5G ProSe direct link exists between the initiating UE and the target UE;

[0661] b) The pair of application layer IDs and network layer protocols of this 5G ProSe direct link are the same as those required by the application layer in the initiating UE of this ProSe application.

[0662] c) The security policy corresponding to the ProSe identifier is consistent with the existing security policy for 5G ProSe direct links;

[0663] d) Timer T5091 is not running; and

[0664] e) The UE does not execute the 5G ProSe direct link key update procedure initiated by the target UE.

[0665] Before initiating this procedure for negotiating a new 5G ProSe UE-to-UE relay UE on an existing 5G ProSe direct link, the following prerequisites must be met:

[0666] a) The initiating UE is the source 5G ProSe UE that communicates with the target 5G ProSe UE via a 5G ProSe UE-to-UE relay UE;

[0667] b) Initiating UE-based trunk reselection, for example, based on PC5 signal strength; and

[0668] c) The UE initiates a process to obtain a list of candidate UE relays via the UE discovery procedure.

[0669] After receiving service data or requests from the upper layer, the initiating UE will perform PC5 QoS flow matching, as specified in section 7.2.8. If no matching PC5 QoS flow exists, the initiating UE will export PC5 QoS parameters and assign a PQFI to the PC5 QoS flow to be established, as specified in section 7.2.7.

[0670] If the 5G ProSe direct link modification procedure needs to add a new PC5QoS flow to an existing 5G ProSe direct link, the initiating UE will create a ProSe direct link modification request message. In this message, the initiating UE:

[0671] a) Will include PQFI, corresponding PC5 QoS parameters, and optional ProSe identifier;

[0672] b) Include link modification operation code set to "Add new PC5 QoS flow to existing 5G ProSe direct link";

[0673] c) Packet filters may include PC5 QoS rules to indicate PC5 QoS flows;

[0674] d) Source UE information containing the user information ID set as the source 5G ProSe layer 3 UE. If the UE acts as a 5G ProSe layer 3 UE relay UE, the 5G ProSe direct link is between the 5G ProSe layer 3 UE relay UE and the target 5G ProSe layer 3 UE, and multiple source 5G ProSe layer 3 UEs use the same 5G ProSe direct link to establish direct communication with the target 5G ProSe layer 3 UE via the 5G ProSe layer 3 UE relay UE.

[0675] e) It may include source UE information set as the user information ID of the source 5G ProSe UE. If the UE acts as a 5G ProSe inter-UE relay UE, the 5G ProSe direct link is between the 5G ProSe inter-UE relay UE and the target 5G ProSe UE, and only one source 5G ProSe UE uses the 5G ProSe direct link to establish direct communication with the target 5G ProSe UE via the 5G ProSe inter-UE relay UE.

[0676] f) Include the target UE information containing the user information ID set as the target 5G ProSe layer 3 UE. If the UE acts as the source 5G ProSe layer 3 UE, the 5G ProSe direct link is between the source 5G ProSe layer 3 UE and the 5G ProSe layer 3 UE relay UE, and the source 5G ProSe layer 3 UE uses the same 5G ProSe direct link to establish direct communication with multiple target 5G ProSe layer 3 UEs via the 5G ProSe layer 3 UE relay UE.

[0677] g) Target UE information may include the user information ID set as the target 5G ProSe UE, provided that:

[0678] 1) The UE acts as the source 5G ProSe UE, and the 5G ProSe direct link is between the source 5G ProSe UE and the 5G ProSe UE inter-relay UE. Furthermore, the source 5G ProSe UE establishes direct communication with only one target 5G ProSe UE via the 5G ProSe UE inter-relay UE using the 5G ProSe direct link; or

[0679] 2) The UE acts as a 5G ProSe inter-UE relay UE, and the 5G ProSe direct link is between the 5G ProSe inter-UE relay UE and the target 5G ProSe end UE; and

[0680] h) may include the target UE layer 2 ID set as the layer 2 ID of the target 5G ProSe UE, if the UE acts as the source 5G ProSe UE and the 5G ProSe direct link is between the source 5G ProSe UE and the relay UE between the 5G ProSe UE.

[0681] If the 5G ProSe direct link modification procedure needs to modify the PC5 QoS parameters used for existing PC5 QoS flows in the existing 5G ProSe direct link, then the initiating UE will create a ProSe direct link modification request message. In this message, the initiating UE:

[0682] a) It will include PQFI and corresponding PC5 QoS parameters, including the ProSe identifier;

[0683] b) Include link modification operation code set to "Modify PC5 QoS parameters of existing PC5 QoS flows";

[0684] c) Packet filters may include PC5 QoS rules to indicate PC5 QoS flows;

[0685] d) Source UE information containing the user information ID set as the source 5G ProSe layer 3 UE. If the UE acts as a 5G ProSe layer 3 UE relay UE, the 5G ProSe direct link is between the 5G ProSe layer 3 UE relay UE and the target 5G ProSe layer 3 UE, and multiple source 5G ProSe layer 3 UEs use the same 5G ProSe direct link to establish direct communication with the target 5G ProSe layer 3 UE via the 5G ProSe layer 3 UE relay UE.

[0686] e) It may include source UE information set as the user information ID of the source 5G ProSe UE. If the UE acts as a 5G ProSe inter-UE relay UE, the 5G ProSe direct link is between the 5G ProSe inter-UE relay UE and the target 5G ProSe UE, and only one source 5G ProSe UE uses the 5G ProSe direct link to establish direct communication with the target 5G ProSe UE via the 5G ProSe inter-UE relay UE.

[0687] f) Include the target UE information containing the user information ID set as the target 5G ProSe layer 3 UE. If the UE acts as the source 5G ProSe layer 3 UE, the 5G ProSe direct link is between the source 5G ProSe layer 3 UE and the 5G ProSe layer 3 UE relay UE, and the source 5G ProSe layer 3 UE uses the same 5G ProSe direct link to establish direct communication with multiple target 5G ProSe layer 3 UEs via the 5G ProSe layer 3 UE relay UE.

[0688] g) Target UE information may include the user information ID set as the target 5G ProSe UE, provided that:

[0689] 1) The UE acts as the source 5G ProSe UE, and the 5G ProSe direct link is between the source 5G ProSe UE and the 5G ProSe UE inter-relay UE. Furthermore, the source 5G ProSe UE establishes direct communication with only one target 5G ProSe UE via the 5G ProSe UE inter-relay UE using the 5G ProSe direct link; or

[0690] 2) The UE acts as a 5G ProSe inter-UE relay UE, and the 5G ProSe direct link is between the 5G ProSe inter-UE relay UE and the target 5G ProSe end UE; and

[0691] h) may include the target UE layer 2 ID set as the destination layer 2 ID of the target 5G ProSe UE, if the UE acts as the source 5G ProSe UE and the 5G ProSe direct link is between the source 5G ProSe UE and the relay UE between the 5G ProSe UE.

[0692] If the 5G ProSe direct link modification procedure needs to associate a new ProSe application with an existing PC5 QoS flow, the initiating UE will create a ProSe direct link modification request message. In this message, the initiating UE:

[0693] a) It will include PQFI and corresponding PC5 QoS parameters, including the ProSe identifier;

[0694] b) Include link modification operation code set to "Associate the new ProSe application with an existing PC5 QoS flow";

[0695] c) Packet filters may include PC5 QoS rules to indicate PC5 QoS flows;

[0696] d) Source UE information containing the user information ID set as the source 5G ProSe layer 3 UE. If the UE acts as a 5G ProSe layer 3 UE relay UE, the 5G ProSe direct link is between the 5G ProSe layer 3 UE relay UE and the target 5G ProSe layer 3 UE, and multiple source 5G ProSe layer 3 UEs use the same 5G ProSe direct link to establish direct communication with the target 5G ProSe layer 3 UE via the 5G ProSe layer 3 UE relay UE.

[0697] e) It may include source UE information set as the user information ID of the source 5G ProSe UE. If the UE acts as a 5G ProSe inter-UE relay UE, the 5G ProSe direct link is between the 5G ProSe inter-UE relay UE and the target 5G ProSe UE, and only one source 5G ProSe UE uses the 5G ProSe direct link to establish direct communication with the target 5G ProSe UE via the 5G ProSe inter-UE relay UE.

[0698] f) Include the target UE information containing the user information ID set as the target 5G ProSe layer 3 UE. If the UE acts as the source 5G ProSe layer 3 UE, the 5G ProSe direct link is between the source 5G ProSe layer 3 UE and the 5G ProSe layer 3 UE relay UE, and the source 5G ProSe layer 3 UE uses the same 5G ProSe direct link to establish direct communication with multiple target 5G ProSe layer 3 UEs via the 5G ProSe layer 3 UE relay UE.

[0699] g) Target UE information may include the user information ID set as the target 5G ProSe UE, provided that:

[0700] 1) The UE acts as the source 5G ProSe UE, and the 5G ProSe direct link is between the source 5G ProSe UE and the 5G ProSe UE inter-relay UE. Furthermore, the source 5G ProSe UE establishes direct communication with only one target 5G ProSe UE via the 5G ProSe UE inter-relay UE using the 5G ProSe direct link; or

[0701] 2) The UE acts as a 5G ProSe inter-UE relay UE, and the 5G ProSe direct link is between the 5G ProSe inter-UE relay UE and the target 5G ProSe end UE; and

[0702] h) may include the target UE layer 2 ID set as the layer 2 ID of the target 5G ProSe UE, if the UE acts as the source 5G ProSe UE and the 5G ProSe direct link is between the source 5G ProSe UE and the relay UE between the 5G ProSe UE.

[0703] If the PC5 5G ProSe direct link modification procedure aims to remove an associated ProSe application from an existing PC5 QoS flow, the initiating UE will create a ProSe direct link modification request message. In this message, the initiating UE:

[0704] a) Will include PQFI and corresponding PC5 QoS parameters, including the ProSe identifier; and

[0705] b) Include link modification operation code set to "Remove ProSe application from existing PC5 QoS flow".

[0706] If the direct link modification procedure aims to remove any PC5 QoS flows from an existing 5G ProSe direct link, the initiating UE will create a ProSe direct link modification request message. In this message, the initiating UE:

[0707] a) Will include PQFI; and

[0708] b) Include link modification operation code set to "Remove existing PC5 QoS flows from existing 5G ProSe direct links".

[0709] If the 5G ProSe direct link modification procedure needs to establish 5G ProSe UE-to-UE relay communication with an additional 5G ProSe layer 3 UE using the existing 5G ProSe layer 3 end UE and the 5G ProSe layer 3 UE-to-UE relay UE, then the initiating UE will create a ProSe direct link modification request message. In this message, the initiating UE:

[0710] a) Source UE information containing the source user information ID of the 5G ProSe layer 3 UE received in the ProSe direct link establishment request message, if the UE acts as a 5G ProSe layer 3 inter-UE relay UE and the 5G ProSe direct link is between the 5G ProSe layer 3 inter-UE relay UE and the target 5G ProSe layer 3 UE.

[0711] b) For Ethernet services, the MAC address of the source 5G ProSe layer 3 UE will be included if the UE acts as a 5G ProSe layer 3 UE inter-relay UE and the 5G ProSe direct link is between the 5G ProSe layer 3 UE inter-relay UE and the target 5G ProSe layer 3 UE.

[0712] c) Include the target UE information containing the user information ID of the additional target 5G ProSe layer 3 end UE that is set to request 5G ProSe inter-UE relay communication, if the UE acts as the source 5G ProSe layer 3 end UE and the 5G ProSe direct link is between the source 5G ProSe layer 3 end UE and the 5G ProSe layer 3 inter-UE relay UE.

[0713] d) The ProSe identifier included in the ProSe identifier received from the upper layer when the UE is acting as a source 5G ProSe layer 3 end UE or when the UE is acting as a relay UE between 5G ProSe layer 3 UEs and is set to the ProSe direct link establishment request message.

[0714] Editor's Note: Whether PQFI and the corresponding PC5 QoS parameters containing the ProSe identifier are included, rather than just the ProSe identifier, requires further investigation.

[0715] Editor's Note: Whether and how to include the ProSe identifier for the 5G ProSe direct link between the source 5G ProSe layer 3 UE and the relay UE between 5G ProSe layer 3 UEs, and the 5G ProSe direct link between the relay UE between 5G ProSe layer 3 UEs and the target 5G ProSe layer 3 UE, requires further research.

[0716] e) Includes link modification operation code configured to "add a new 5G ProSe layer 3 UE to an existing 5G ProSe direct link"; and

[0717] f) May include the target UE layer 2 ID set as the layer 2 ID of the target 5G ProSe layer 3 UE, if the UE acts as the source 5G ProSe layer 3 UE and the 5G ProSe direct link is between the source 5G ProSe layer 3 UE and the relay UE between the 5G ProSe layer 3 UE and the 5G ProSe layer 3 UE.

[0718] If the 5G ProSe direct link modification procedure needs to release the shared 5G ProSe direct link between a 5G ProSe Layer 3 end UE and a 5G ProSe Layer 3 inter-UE relay UE, and release the 5G ProSe inter-UE relay communication with one of the peer 5G ProSe Layer 3 end UEs, then the initiating UE will create a ProSe direct link modification request message. In this message, the initiating UE:

[0719] a) Source UE information containing the source user information ID of the 5G ProSe layer 3 end UE received in the ProSe direct link release request message, if the UE acts as a 5G ProSe layer 3 inter-UE relay UE and the 5G ProSe direct link is between the 5G ProSe layer 3 inter-UE relay UE and the 5G ProSe layer 3 end UE.

[0720] b) Include the target UE information containing the user information ID of the peer 5G ProSe layer 3 end UE configured to release 5G ProSe inter-UE relay communication with it, if the UE acts as a 5G ProSe layer 3 end UE and the 5G ProSe direct link is between the 5G ProSe layer 3 end UE and the 5G ProSe layer 3 inter-UE relay UE; and

[0721] c) Include link modification operation code set to "Remove 5G ProSe Layer 3 UE from existing 5G ProSe direct link".

[0722] If the 5G ProSe direct link modification procedure is to trigger inter-UE relay reselection, then the initiating UE will create a ProSe direct link modification request message. In this message:

[0723] 1) If the initiating UE acts as the source 5G ProSe UE, and the 5G ProSe direct link is between the source 5G ProSe UE and the relay UE between the 5G ProSe UE, then the initiating UE:

[0724] a) Will include a relay reselection instruction;

[0725] b) A list containing candidate 5G ProSe UE-to-UE relay UE user information IDs;

[0726] c) A list containing the target 5G ProSe end-UE IP address / prefix, if IP communication is used; and

[0727] d) May contain a list of candidate 5G ProSe UE inter-UE relay UE layer 2 IDs.

[0728] 2) If the initiating UE acts as a 5G ProSe inter-UE relay UE, and the 5G ProSe direct link is between the 5G ProSe inter-UE relay UE and the target 5G ProSe end UE, then the initiating UE:

[0729] a) Will include a relay reselection instruction;

[0730] b) A list containing candidate 5G ProSe UE-to-UE relay UE user information IDs;

[0731] c) Will include the originating 5G ProSe UE IP address / prefix, if IP communication is used; and

[0732] d) May contain a list of candidate 5G ProSe UE inter-UE relay UE layer 2 IDs.

[0733] Editor's Note: ProSe direct link modification request messages need to be updated.

[0734] If the 5G ProSe direct link modification procedure is to trigger a relay reselection and the initiating UE acts as a 5GProSe inter-UE relay UE, then the initiating UE will create a ProSe direct link modification request message for each IP address / prefix of the target 5G ProSe UE received from the 5G ProSe source UE on the associated ProSe direct link modification request message.

[0735] After the ProSe direct link modification request message is generated, the initiating UE transmits this message, along with the Layer 2 ID of the initiating UE used for 5G ProSe direct communication and the Layer 2 ID of the target UE used for 5G ProSe direct communication, to the lower layer for transmission, and starts timer T5081. While timer T5081 is running, the UE will not send new ProSe direct link modification request messages to the same target UE.

[0736] The document titled "5G ProSe Direct Link Modifier" in 3GPP TS24.554V18.1.0 Figure 7 2.3.2.1 Reproduced as Figure 18 ]

[0737] The 3GPP TS24.554V18.1.0 document titled "5G ProSe Direct Link Modification for Layer 3 UE Inter-UE Relay Reselection" Figure 7 2.3.2.2 Reproduced as Figure 19 ]

[0738] 7.2.3.3 5G ProSe Direct Link Modification Procedure Accepted by the Target UE

[0739] If the ProSe Direct Link Modification Request message is accepted, the target UE will respond with a ProSe Direct Link Modification Accept message.

[0740] If the ProSe direct link modification request message is to add a new ProSe application, add a new PC5 QoS stream, or modify any existing PC5 QoS stream in the 5G ProSe direct link, then the target UE:

[0741] a) It will include PQFI, corresponding PC5 QoS parameters, and optional ProSe identifiers accepted by the target UE;

[0742] b) May contain PC5 QoS rules for indicating packet filters for PC5 QoS flows;

[0743] c) Source UE information, including the user information ID set as the source 5G ProSe layer 3 UE, where the UE acts as the target 5G ProSe layer 3 UE, the 5G ProSe direct link is between the 5G ProSe layer 3 UE relay UE and the target 5G ProSe layer 3 UE, and the target 5G ProSe layer 3 UE has already established direct communication with multiple source 5G ProSe layer 3 UEs using the same 5G ProSe direct link by the 5G ProSe layer 3 UE relay UE; and

[0744] d) May include source UE information set as the user information ID of the source 5G ProSe UE, where the UE acts as the target 5G ProSe UE, the 5G ProSe direct link is between the 5G ProSe UE relay UE and the target 5G ProSe UE, and the target 5G ProSe UE has already established direct communication with only one source 5G ProSe UE via the 5G ProSe direct link through the 5G ProSe UE relay UE; and

[0745] e) Include the target UE information containing the user information ID set as the target 5G ProSe UE. If the UE acts as a 5G ProSe inter-UE relay UE, the 5G ProSe direct link is between the source 5G ProSe UE and the 5G ProSe inter-UE relay UE, and the source 5G ProSe layer 3 UE has already established direct communication with multiple target 5G ProSe layer 3 UEs using the same 5G ProSe direct link by the 5G ProSe layer 3 inter-UE relay UE.

[0746] f) May include target UE information set as the user information ID of the target 5G ProSe UE. If the UE acts as a 5G ProSe inter-UE relay UE, the 5G ProSe direct link is between the source 5G ProSe UE and the 5G ProSe inter-UE relay UE, and the source 5G ProSe UE has already established direct communication with only one target 5G ProSe UE using the 5G ProSe direct link through the 5G ProSe inter-UE relay UE.

[0747] In the ProSe direct link modification accept message.

[0748] If the ProSe direct link modification request message removes an existing ProSe application from the 5G ProSe direct link, then the target UE will remove the ProSe identifier and the corresponding PQFI and PC5 QoS parameters received in the ProSe direct link modification request message from the attribute set associated with the 5G ProSe direct link.

[0749] If the ProSe direct link modification request message removes an existing PC5 QoS flow from the PC5 5G ProSe direct link, then the target UE will remove the PQFI and the corresponding PC5 QoS parameters from the attribute set associated with the 5G ProSe direct link.

[0750] If the ProSe direct link modification request message is to add a new ProSe application, add a new PC5 QoS flow, or modify any existing PC5 QoS flow in the 5G ProSe direct link, then after sending the ProSe direct link modification accept message, the target UE will provide the added or modified PQFI, the corresponding PC5 QoS parameters, and the PC5 link identifier to the lower layer.

[0751] If the ProSe direct link modification request message is to remove an existing ProSe application or remove an existing PC5 QoS flow from the 5G ProSe direct link, then after sending the ProSe direct link modification acceptance message, the target UE will provide the removed PQFI and PC5 link identifier to the lower layer.

[0752] If the ProSe direct link modification request message establishes 5G ProSe UE-to-UE relay communication with an additional 5G ProSe UE using the existing 5G ProSe layer 3 end UE and 5G ProSe layer 3 UE-to-UE relay UE using the existing 5G ProSe direct link between the 5G ProSe layer 3 end UE and the 5G ProSe layer 3 UE-to-UE relay UE, then the target UE:

[0753] a) If acting as a 5G ProSe Layer 3 UE inter-UE relay UE, a 5G ProSe direct link establishment procedure toward the target 5G ProSe Layer 3 UE will be executed as specified in section 7.2.2.2; and after receiving the ProSe direct link establishment acceptance message from the target 5G ProSe Layer 3 UE, a ProSe direct link modification acceptance message will be created.

[0754] b) If acting as a target 5G ProSe layer 3 UE, a ProSe direct link modification accept message will be created; and

[0755] c) In the ProSe direct link modification acceptance message, the target UE:

[0756] 1) If the UE acts as the target 5G ProSe layer 3 UE, it will contain source UE information set as the user information ID of the source 5G ProSe layer 3 UE; or

[0757] 2) If the UE acts as a 5G ProSe layer 3 inter-UE relay UE:

[0758] i) Include the target UE information containing the user information ID set as the target 5G ProSe layer 3 UE;

[0759] ii) For IP services, it may include the target 5G ProSe layer 3 UE IP address IE, which is set as the IP address of the additional target 5G ProSe layer 3 UE; and

[0760] iii) For Ethernet services, the MAC address of the target 5G ProSe layer 3 UE will be included.

[0761] If the ProSe direct link modification request message releases 5G ProSe inter-UE relay communication with one of the peer 5G ProSe layer 3 end UEs using the shared 5G ProSe direct link between the 5G ProSe layer 3 end UE and the 5G ProSe layer 3 inter-UE relay UE, then the target UE:

[0762] a) If acting as a relay UE between 5G ProSe layer 3 UEs, one of the following procedures toward the target 5G ProSe layer 3 UE can be initiated:

[0763] 1) A 5G ProSe direct link release procedure, as specified in section 7.2.6.2, is used to release the 5G ProSe direct link with the peer 5G ProSe Layer 3 UE; or

[0764] 2) The 5G ProSe direct link modification procedure, as specified in section 7.2.3.2, is used to remove the corresponding PC5 QoS flow if the UE determines to maintain a 5G ProSe direct link with its peer 5G ProSe Layer 3 UE; and

[0765] b) A ProSe direct link modification accept message will be created, and in this message, the target UE:

[0766] 1) Source UE information, including the user information ID set as the source 5G ProSe layer 3 UE, if the UE acts as the target 5G ProSe layer 3 UE; or

[0767] 2) Include the target UE information containing the user information ID set as the target 5G ProSe layer 3 UE, if the UE acts as a 5G ProSe layer 3 UE relay UE.

[0768] If the 5G ProSe direct link is used for 5G ProSe direct communication between a 5G ProSe remote UE and a 5G ProSe layer 3 UE to a relay UE in the network, and if the initiating UE is a 5G ProSe remote UE, then the target UE (as a 5G ProSe layer 3 UE to a relay UE in the network) performs the QoS flow processing procedure as specified in sections 8.2.6.3.3 and 8.2.6.4.2.

[0769] If the ProSe direct link modification request message is for UE reselection of inter-UE relay, the target UE can execute the 5G ProSe inter-UE relay discovery procedure, in which the discovery message contains the user information ID of the candidate 5G ProSe inter-UE relay, and can set the layer 2 ID of the candidate 5G ProSe inter-UE relay to the destination layer 2 ID to carry the discovery message, if it is received in the ProSe direct link modification request message.

[0770] If the ProSe direct link modification request message is accepted to trigger inter-UE relay reselection, the target UE will establish a PC5 unicast link with the selected 5G ProSe inter-UE relay UE (if such a PC5 unicast link does not already exist), and the 5G ProSe direct link is between the target 5G ProSe end UE and the 5G ProSe inter-UE relay UE.

[0771] If the ProSe Direct Link Modification Request message is accepted to trigger relay reselection, the target UE will respond with a ProSe Direct Link Modification Accept message. In this message:

[0772] 1) If the target UE acts as the target 5G ProSe end UE and the 5G ProSe direct link is between the target 5G ProSe end UE and the relay UE between the 5G ProSe UE, then the target UE:

[0773] a) Will include a relay reselection instruction;

[0774] b) Will include the new 5G ProSe UE-to-UE relay UE user information ID;

[0775] c) Will include the IP address of the UE initiating the 5G ProSe; and

[0776] d) Includes the target 5GProSe end UE IP address (if using IP communication) to be used with the latest selected 5G ProSe UE-to-UE relay UE.

[0777] 2) If the target UE acts as a 5G ProSe inter-UE relay UE and the 5G ProSe direct link is between the 5G ProSe inter-UE relay UE and the source 5G ProSe UE, then the target UE:

[0778] a) Will include a relay reselection instruction;

[0779] b) Will include the new 5G ProSe UE-to-UE relay UE user information ID;

[0780] c) Will include the target 5G ProSe end-UE IP address; and

[0781] d) Includes the target 5GProSe end UE IP address (if using IP communication) to be used with the latest selected 5G ProSe UE-to-UE relay UE.

[0782] Editor's Note: ProSe direct link modifications to message reception require updates.

[0783] If the target UE accepts the 5G ProSe direct link modification request, then the target UE may perform PC5 QoS flow establishment on the 5G ProSe direct link as specified in section 7.2.7, and perform PC5 QoS flow matching on the 5G ProSe direct link as specified in section 7.2.8.

[0784] 7.2.3.4 The 5G ProSe direct link modification procedure initiated by the UE is completed.

[0785] Upon receiving the ProSe direct link modification accept message, the initiating UE will stop timer T5081.

[0786] Upon receiving the ProSe direct link modification acceptance message, if the ProSe direct link modification request message is to add a new ProSe application, add a new PC5 QoS flow, or modify any existing PC5 QoS flow in the 5G ProSe direct link, then the initiating UE will provide the added or modified PQFI, the corresponding PC5 QoS parameters, and the PC5 link identifier to the lower layer.

[0787] Upon receiving a ProSe direct link modification acceptance message, if the ProSe direct link modification request message is to remove an existing ProSe application or remove an existing PC5 QoS flow from the 5G ProSe direct link, then the initiating UE will provide the removed PQFI and PC5 link identifier to the lower layer.

[0788] Upon receiving the ProSe direct link modification accept message, if the ProSe direct link modification request message is to establish 5G ProSe inter-UE relay communication with an additional 5G ProSe layer 3 UE using the existing 5G ProSe direct link between the 5G ProSe layer 3 end UE and the 5G ProSe layer 3 inter-UE relay UE, then the initiating UE will send a ProSe direct link establishment accept message to the source 5G ProSe layer 3 end UE, as specified in section 7.2.2.3, if the initiating UE acts as a 5G ProSe layer 3 inter-UE relay UE.

[0789] Editor's Note: Whether and how to include the ProSe identifier for the 5G ProSe direct link between the source 5G ProSe layer 3 UE and the relay UE between 5G ProSe layer 3 UEs, and the 5G ProSe direct link between the relay UE between 5G ProSe layer 3 UEs and the target 5G ProSe layer 3 UE, requires further research.

[0790] Upon receiving a ProSe direct link modification accept message containing a relay reselection indication, if the ProSe direct link modification request message was for Layer 3 inter-UE relay reselection, the initiating UE will establish a PC5 unicast link with the selected 5G ProSe inter-UE relay UE (if such a PC5 unicast link does not yet exist) and will create a ProSe direct link modification confirmation message. In this message, the initiating UE:

[0791] a) Include the relay reselection instruction, the IP address of the initiating 5G ProSe UE to be used with the newly selected 5G ProSe UE, and the IP address of the target 5G ProSe UE, if IP communication is used, and if:

[0792] 1) The UE acts as the source 5G ProSe UE, and the 5G ProSe direct link is between the source 5G ProSe UE and the relay UE between the 5G ProSe UE; or

[0793] b) Include the relay reselection instruction, the IP address of the target 5G ProSe UE to be used with the newly selected inter-5G ProSe UE, and the IP address of the source 5G ProSe UE, if IP communication is used, and if:

[0794] 1) The UE acts as a 5G ProSe inter-UE relay UE, and the 5G ProSe direct link is between the 5G ProSe inter-UE relay UE and the target 5G ProSe end UE.

[0795] After the ProSe direct link modification confirmation message is generated, the initiating UE will pass this message along with the Layer 2 ID of the initiating UE for 5G ProSe direct communication and the Layer 2 ID of the target UE for 5G ProSe direct communication to the lower layer for transmission.

[0796] If the source UE confirms acceptance of the 5G ProSe direct link modification, then the source UE begins receiving and / or transmitting services via the newly selected 5G ProSe inter-UE relay UE.

[0797] 7.2.3.5 5G ProSe direct link modification procedure not accepted by the target UE

[0798] If the 5G ProSe direct link modification request cannot be accepted, the target UE will send a ProSe direct link modification rejection message. The ProSe direct link modification rejection message contains a PC5 signaling protocol reason IE, which is set to one of the following reason values:

[0799] #5 Lack of resources for 5G ProSe direct links;

[0800] #6 The required service is not allowed;

[0801] #12 Misaligned security policy;

[0802] #16 Lack of local capabilities;

[0803] #20 Fault originating from the 5G ProSe UE;

[0804] #yy relay UE was not selected for link establishment with integrated discovery; or

[0805] #111 Unspecified protocol error.

[0806] If the target UE is not allowed to accept this request, for example because the ProSe application to be added is not allowed according to the operator policy or configuration parameters for ProSe communication on PC5 as specified in Section 5.2.4, then the target UE will send a ProSe direct link modification rejection message with PC5 signaling protocol reason value #6 "Required service not allowed".

[0807] If the 5G ProSe direct link modification fails due to congestion issues or other temporary lower-layer issues causing resource constraints, the target UE will send a ProSe direct link modification rejection message with PC5 signaling protocol reason value #5 "Lack of resources for 5G ProSe direct link".

[0808] If the target UE, acting as the target 5G ProSe end UE, receives one or more direct link modification requests or direct link establishment requests for establishing an end-to-end connection with the source 5G ProSe end UE and using integration discovery, then the target UE will select a 5G ProSe inter-UE relay UE and send a ProSe direct link modification rejection message with the PC5 signaling protocol reason value #yy "Relay UE not selected for link establishment with integration discovery" to the 5G ProSe inter-UE relay UE that was not selected and has sent a ProSe direct link modification request message.

[0809] If the link modification operation code is set to "Associate the new ProSe application with the existing PC5 QoS flow", and the security policy corresponding to the ProSe identifier is not aligned with the security policy applied to the existing 5G ProSe direct link, then the target UE will send a ProSe direct link modification rejection message with the PC5 signaling protocol reason value #12 "Unaligned security policy".

[0810] If a link modification operation requires the addition of a new PC5 QoS flow, but the target UE cannot support the additional packet filters required on the target UE's existing PDU session, then the target UE will send a ProSe direct link modification rejection message with the PC5 signaling protocol reason value #16 "lack of local capability".

[0811] If the target UE acts as the target 5G ProSe end UE, and the 5G ProSe direct link modification procedure is between the 5G ProSe UE relay UE and the target 5G ProSe end UE, then the target 5G ProSe end UE can include the source UE information IE, which is set to the user information ID of the source 5G ProSe end UE that initiated the 5G ProSe direct link establishment procedure, in the ProSe direct link modification rejection message.

[0812] If the target UE acts as a 5G ProSe inter-UE relay UE, the 5G ProSe direct link modification procedure is between the source 5G ProSe UE and the 5G ProSe inter-UE relay UE, and the target 5G ProSe UE has rejected the 5G ProSe direct link establishment procedure or the 5G ProSe direct link modification procedure, then the 5G ProSe inter-UE relay UE will send a ProSe direct link modification rejection message with the PC5 signaling protocol reason value #20 "Fault from 5G ProSe UE" to the source 5G ProSe UE. The 5G ProSe inter-UE relay UE may include in the ProSe direct link modification rejection message a PC5 UE fault reason IE set to the PC5 signaling protocol reason received from the target 5G ProSe UE that has rejected the 5G ProSe direct link establishment procedure, as specified in section 7.2.2.5. The 5G ProSe inter-UE relay UE may include in the ProSe direct link modification rejection message a target UE information IE set to the user information ID of the target 5G ProSe UE that has rejected the 5G ProSe direct link establishment procedure.

[0813] For other reasons that cause link establishment failure, the target UE will send a ProSe direct link modification rejection message with PC5 signaling protocol reason value #111 "Unspecified protocol error".

[0814] Upon receiving a ProSe direct link modification rejection message, the initiating UE will stop timer T5081 and abort the 5G ProSe direct link modification procedure. If the PC5 signaling protocol reason value in the ProSe direct link modification rejection message is #11 "Required service not allowed", #5 "Lack of resources for 5G ProSe direct link", or #12 "Security policy not aligned", then the initiating UE will not attempt to initiate 5G ProSe direct link modification for the same target UE to add the same ProSe application or add or modify the same PC5 QoS flow for at least time period T.

[0815] Note: The length of time period T is specific to the UE implementation scheme and may differ when the UE receives PC5 signaling protocol reason value #11 "Required service not allowed", or when the UE receives PC5 signaling protocol reason value #5 "Lack of resources for 5G ProSe direct link", or when the UE receives PC5 signaling protocol reason value #12 "Security policy not aligned". The length of time period T is not less than 30 minutes.

[0816] 7.2.3.6 Abnormal situations

[0817] 7.2.3.6.1 Abnormal situations at the UE initiation point

[0818] The following abnormal conditions can be identified:

[0819] a) If timer T5081 expires, the initiating UE will retransmit the ProSe direct link modification request message and restart timer T5081. After reaching the maximum allowed number of retransmissions, the initiating UE will abort the 5GProSe direct link modification procedure and may notify the upper-layer target UE that it is unreachable.

[0820] Note 1: The maximum number of retransmissions allowed is specific to the UE implementation scheme.

[0821] Note 2: Whether the initiating UE releases this 5G ProSe direct link after the maximum number of allowed retransmissions has been reached depends on its implementation scheme.

[0822] b) For the same 5G ProSe direct link, if the initiating UE receives a ProSe direct link release request message after initiating the 5GProSe direct link modification procedure, the initiating UE will stop timer T5081, terminate the 5GProSe direct link modification procedure, and continue the 5GProSe direct link release procedure.

[0823] c) For the same 5G ProSe direct link, if the initiating UE receives a ProSe direct link modification request message during the 5G ProSe direct link modification procedure, the initiating UE will stop timer T5081 and abort the 5G ProSe direct link modification procedure. Subsequent processing depends on the implementation scheme; for example, the initiating UE may wait for a time depending on the implementation scheme before initiating a new 5G ProSe direct link modification procedure (if still necessary).

[0824] Note 3: Timer values ​​need to be set depending on the implementation scheme to avoid further conflicts (e.g., random timer values).

[0825] 7.2.3.6.2 Abnormal situations at the target UE

[0826] The following abnormal conditions can be identified:

[0827] a) 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 modification procedure, the target UE will stop all running timers for this 5G ProSe direct link, terminate the 5G ProSe direct link modification procedure, and continue the 5G ProSe direct link release procedure.

[0828] 7.2.3.7 The 5G ProSe direct link modification procedure performed by the target UE is completed.

[0829] Upon receiving confirmation of the ProSe direct link modification, the target 5G ProSe UE begins to receive services, transmit services, or perform both via the newly selected 5G ProSe UE relay UE.

[0830] [...]

[0831] 7.2.10 5G ProSe Direct Link Security Mode Control Procedure

[0832] 7.2.10.1 Overview

[0833] The 5G ProSe direct link security mode control procedure is used to establish security between two UEs during the 5G ProSe direct link establishment procedure or the 5G ProSe direct link key update procedure. Security is not established if UE PC5 signaling integrity protection is not activated. After successfully completing the 5G ProSe direct link security mode control procedure, the selected security algorithm and its non-empty associated key are used to protect the integrity of all PC5 signaling messages exchanged on this 5G ProSe direct link between the UEs and encrypt them. The security context is also used to protect all PC5 user plane data exchanged on this 5G ProSe direct link between the UEs. The UE that sends the ProSe direct link security mode command message is called the "initiating UE," and the other UEs are called the "target UE."

[0834] 7.2.10.2 5G ProSe direct link security mode control procedure initiated by the initiating UE

[0835] Before initiating the 5G ProSe direct link security mode control procedure, the UE must meet the following prerequisites:

[0836] a) The target UE has initiated a 5G ProSe direct link establishment procedure towards the initiating UE by sending a ProSe direct link establishment request message, and:

[0837] 1) ProSe direct link establishment request message:

[0838] i) An IE containing target user information, which includes the application layer ID of the initiating UE; or

[0839] ii) The UE does not contain the target user information IE, and the UE initiating the request is interested in the ProSe service identified by the ProSe identifier in the ProSe direct link establishment request message; and

[0840] 2) Initiate UE:

[0841] i) If the direct communication is not between a 5G ProSe remote UE and a 5G ProSe UE-to-network relay UE, then based on the K included in the ProSe direct link establishment request message. NRP ID identifier existing K NRP Or export a new K NRP ;

[0842] ii) If direct communication is between a 5G ProSe remote UE and a 5G ProSe UE-to-network relay UE, where a user plane security procedure is used, then the new K is received according to the user plane security procedure specified in 3GPP TS 33.503

[34] . NRP ;

[0843] iii) If direct communication is between a 5G ProSe remote UE and a 5G ProSe UE to a network relay UE, where a security procedure on the control plane is used, then the new K is received according to the security procedure on the control plane specified in 3GPP TS 33.503

[34] . NR_ProSe ;or

[0844] iv) It has been decided not to activate security protection based on its UE 5G ProSe direct signaling security policy and the target UE's 5G ProSe direct signaling security policy; or

[0845] b) The target UE has initiated a 5G ProSe direct link key update procedure toward the initiating UE by sending a ProSe direct link key update request message and the following:

[0846] 1) If the target UE has included a re-authentication indication in the ProSe direct link key update request message, the initiating UE has exported a new key. NRP .

[0847] when:

[0848] a) Direct communication is not between the 5G ProSe remote UE and the 5G ProSe UE to the network relay UE, if the new K NRP It has been exported by the initiating UE; or

[0849] b) Direct communication is between the 5G ProSe remote UE and the 5G ProSe UE to the network relay UE, if the initiating UE receives the new K according to the security procedure on the user plane or the security procedure on the control plane respectively. NRP or K NR_ProSe As specified in 3GPP TS 33.503

[34] ;

[0850] The UE will generate KNRP The two MSBs of ID ensure that the obtained K NRP The ID will be unique in the UE that initiates the process.

[0851] Note 1: If the direct communication is not between the 5G ProSe remote UE and the 5G ProSe UE to the network relay UE, then K NRP ID remains corresponding to K NRP The ID. If direct communication is between the 5G ProSe remote UE and the 5G ProSe UE to the network relay UE, then K NRP ID remains corresponding to K NRP (If a security program on the user plane is being used) or K NR_ProSe (If a security procedure on the control plane is used) ID.

[0852] The initiating UE will select a security algorithm based on its UE 5G ProSe direct signaling security policy and the target UE's 5G ProSe direct signaling security policy. If the 5G ProSe direct link security mode control procedure is triggered during the 5G ProSe direct link establishment procedure, then if the 5G ProSe direct signaling integrity protection policy of either the initiating UE or the target UE is set to "requires signaling integrity protection," the initiating UE will not select an empty integrity protection algorithm. If the 5G ProSe direct link security mode control procedure is triggered during the 5G ProSe direct link key update procedure, then the initiating UE:

[0853] a) If the integrity protection algorithm currently used for 5G ProSe direct links is different from the empty integrity protection algorithm, then the empty integrity protection algorithm will not be selected;

[0854] b) If the encryption protection algorithm currently used for the 5G ProSe direct link is different from the empty encryption protection algorithm, then the empty encryption protection algorithm will not be selected;

[0855] c) If the currently used integrity protection algorithm is the empty integrity protection algorithm, then the empty integrity protection algorithm will be selected; and

[0856] d) If the current encryption protection algorithm is the empty encryption protection algorithm, then the empty encryption protection algorithm will be selected.

[0857] Next, the UE will initiate:

[0858] a) If direct communication is not between a 5G ProSe remote UE and a 5G ProSe UE to a network relay UE:

[0859] 1) Generate a 128-bit Nonce_2 value;

[0860] 2) Nonce_1 and K received from the ProSe direct link establishment request message NRP Exporting K from Nonce_2 NRP-sess As specified in 3GPP TS 33.536

[37] ; and

[0861] 3) From K NRP-sess The selected security algorithm is used to derive the NR PC5 encryption key NRPEK and the NR PC5 integrity key NRPIK, as specified in 3GPP TS 33.536

[37] ;

[0862] b) If the direct communication is between a 5G ProSe remote UE and a 5G ProSe UE to a network relay UE, and the security procedures on the control plane specified in 3GPP TS 33.503

[34] are used:

[0863] 1) K received from the ProSe direct link establishment request message NR_ProSe Nonce_2 and Nonce_1 derive K relay-sess As specified in 3GPP TS 33.503

[34] ; and

[0864] 2) From K relay-sess The selected security algorithm is used to derive the NR PC5 encryption key K. relay-enc and NR PC5 integrity key K relay-int As specified in 3GPP TS 33.503

[34] ; or

[0865] c) If the direct communication is between a 5G ProSe remote UE and a 5G ProSe UE to a network relay UE and uses the user plane security procedures specified in 3GPP TS 33.503

[34] :

[0866] 1) K received from the ProSe direct link establishment request message NRP K NRP Freshness parameters 2 and K NRP Freshness parameter 1 exported K NRP-sess As specified in 3GPP TS 33.503

[34] ; and

[0867] 2) From K NRP-sess The selected security algorithm is used to derive the NR PC5 encryption key NRPEK and the NR PC5 integrity key NRPIK, as specified in 3GPP TS 33.503

[34] ; and

[0868] d) Create a ProSe direct link security mode command message. In this message, the UE initiates:

[0869] 1) The key-containing information container IE will be used, provided that the 5G ProSe direct link is not used for direct communication between the 5G ProSe remote UE and the relay UE from the 5G ProSe UE to the network, and a new key has been derived at the initiating UE. NRP And used to generate K NRP The authentication method requires sending information to complete the 5G ProSe direct link authentication procedure;

[0870] Note 2: The key establishment information container is provided by the upper layer.

[0871] 2) Will contain K NRP The MSB of ID IE, provided that a new key has already been exported. NRP Or the new K has already been received at the initiating UE. NRP or K NR_ProSe ;

[0872] 3) Will include Nonce_2IE, which:

[0873] i) When the direct communication is not between a 5G ProSe remote UE and a 5G ProSe UE to a relay UE in the network, set it to a 128-bit temporary value generated by the initiating UE;

[0874] ii) When direct communication is between a 5G ProSe remote UE and a 5G ProSe UE-to-network relay UE and uses a security procedure on the user plane as specified in 3GPP TS 33.503

[34] , the K is set to be received by the initiating UE. NRP Freshness parameter 2 value; or

[0875] iii) When direct communication is between a 5G ProSe remote UE and a 5G ProSe UE to a network relay UE and a security procedure on the control plane specified in 3GPP TS 33.503

[34] is used, set to the Nonce_2 value received by the initiating UE;

[0876] For the purpose of establishing a session key on this 5GProSe direct link when the selected integrity protection algorithm is not an empty integrity protection algorithm;

[0877] 4) It will include the selected security algorithm;

[0878] 5) Include the UE security capabilities received from the target UE in the ProSe direct link establishment request message or ProSe direct link key update request message;

[0879] 6) The UE 5GProSe direct signaling security policy received from the target UE will be included in the ProSe direct link establishment request message;

[0880] 7) If the selected integrity protection algorithm is not a null integrity protection algorithm, then it will include the K selected by the initiating UE as specified in 3GPP TS33.536

[37] . NRP-sess LSB of ID;

[0881] Note 3: If the direct communication is not between the 5G ProSe remote UE and the 5G ProSe UE to the network relay UE, then K NRP-sess ID remains corresponding to K NRP-sess The ID. If direct communication is between the 5G ProSe remote UE and the 5G ProSe UE to the network relay UE, then K NRP-sess ID remains corresponding to K NRP-sess (If a security program on the user plane is being used) or K relay-sess (If a security procedure on the control plane is used) ID.

[0882] 8) When direct communication is between a 5G ProSe remote UE and a 5G ProSe UE to a network relay UE, if it is received from a 5G PKMF according to the security procedures on the user plane specified in 3GPP TS 33.503

[34] , then it will contain GPI; and

[0883] 9) When direct communication is between a 5G ProSe remote UE and a 5G ProSe UE to a network relay UE, if it is received from the network according to the security procedures on the control plane specified in 3GPP TS 33.503

[34] , then it will contain an EAP message.

[0884] If the security protection of this 5G ProSe direct link is activated by using a non-empty integrity protection algorithm or a non-empty encryption protection algorithm, then the initiating UE will receive the K from the ProSe direct link establishment request message or the ProSe direct link key update request message. NRP-sess The MSB of the ID and the K contained in the ProSe direct link security mode command message. NRP-sess ID's LSB formation K NRP-sess ID. The initiating UE will use K. NRP-sess The ID is used to identify the new security context.

[0885] The initiating UE will set the source layer 2 ID and destination layer 2 ID as follows:

[0886] 1) If the initiating UE acts as a relay UE to the network for a 5G ProSe layer 3 UE, and uses the EAP-AKA-based authentication method as specified in section 6.3.3.3 of 3GPP TS 33.503

[34] ,

[0887] Set the source layer 2 ID to the source layer 2 ID used for the ProSe AA message transmission request message, and set the destination layer 2 ID to the destination layer 2 ID used for the ProSe AA message transmission request message;

[0888] 2) If the initiating UE does not act as a relay UE for the 5G ProSe UE to the network, and the 5G ProSe direct link authentication procedure has already been initiated:

[0889] Set the source layer 2 ID to the source layer 2 ID used for the ProSe direct link authentication request message, and set the destination layer 2 ID to the destination layer 2 ID used for the ProSe direct link authentication request message.

[0890] 3) Otherwise, assign a source layer 2 ID and set the destination layer 2 ID to the source layer 2 ID in the ProSe direct link establishment request message.

[0891] Note 4: The UE implementation ensures that any value of the self-assigned source layer 2 ID is different from any other self-assigned source layer 2 ID used for direct discovery of 5G ProSe as specified in Sections 6.2.14, 6.2.15 and 8.2.1, and different from any other destination layer 2 ID provided as specified in Section 5.2.

[0892] Note 5: The target UE can reuse the Layer 2 ID that the target UE previously used in a 5GProSe direct link with the same peer UE.

[0893] After the ProSe direct link security mode command message is generated, the initiating UE passes this message along with the following to the lower layer for transmission: source layer 2ID and destination layer 2ID, NRPIK (or K relay-Int (where applicable), NRPEK (or K) relay-enc (where applicable) K NRP-sess ID, the selected security algorithm as specified in TS 33.536

[37] ; an indication (if applicable) of activation of 5G ProSe direct signaling security protection for 5G ProSe direct links with new security contexts; and start timer T5089. While timer T5089 is running, the initiating UE will not send new ProSe direct link security mode command messages to the same target UE.

[0894] Note 6: The ProSe direct link security mode command message is protected for integrity (and is not encrypted) at the lower layer using the new security context. If the 5G ProSe direct link security mode control procedure is triggered during the 5G ProSe direct link key update procedure, the initiating UE will provide the lower layer with an indication (if applicable) of the activation of 5GProSe direct user plane security protection for the 5G ProSe direct link with the new security context, as well as the Layer 2 ID of the initiating UE for 5G ProSe direct communication and the Layer 2 ID of the target UE for 5G ProSe direct communication.

[0895] The document titled "5G ProSe Direct Link Security Mode Control Procedure" in 3GPP TS24.554V18.1.0 Figure 7 2.10.2.1 Reproduced as Figure 20 ]

[0896] 7.2.10.3 5G ProSe Direct Link Security Mode Control Procedure Accepted by the Target UE

[0897] Upon receiving the ProSe direct link security mode command message, if the Layer 2 ID of the newly assigned initiating UE is included and if the 5G ProSe direct link authentication procedure has not yet been executed, the target UE will replace the original initiating UE's Layer 2 ID with the newly assigned initiating UE's Layer 2 ID to perform 5G ProSe direct communication. The target UE will verify the selected security algorithm IE included in the ProSe direct link security mode command message. If "empty integrity algorithm" is included in the selected security algorithm IE, then no integrity protection is provided for this 5G ProSe direct link, and signaling messages are transmitted without protection. If "empty encryption algorithm" and integrity algorithms other than "empty integrity algorithm" are included in the selected algorithm IE, then no encryption protection is provided for this 5G ProSe direct link, and signaling messages are transmitted without protection. If the target UE's 5GProSe direct signaling integrity protection policy is set to "requires signaling integrity protection," then the target UE will verify that the selected security algorithm IE in the ProSe direct link security mode command message does not contain an empty integrity protection algorithm. If the selected integrity protection algorithm is not an empty integrity protection algorithm, then the target UE will:

[0898] a) If direct communication is not between a 5G ProSe remote UE and a 5G ProSe UE to a network relay UE:

[0899] 1) K received from the ProSe direct link security mode command message NRP Nonce_1 and Nonce_2 derive K NRP-sessAs specified in 3GPP TS 33.536

[37] ;

[0900] 2) From K NRP-sess The selected integrity algorithm is used to derive NRPIK, as specified in 3GPP TS 33.536

[37] ; and

[0901] 3) If exporting K NRP-sess Furthermore, if the selected encryption protection algorithm is not an empty encryption protection algorithm, then the target UE will be from K NRP-sess The selected encryption algorithm is used to derive NRPEK, as specified in 3GPP TS 33.536

[37] ; or

[0902] b) If direct communication is between a 5G ProSe remote UE and a 5G ProSe UE to a relay UE in the network:

[0903] 1) If the security procedure on the control plane specified in 3GPP TS 33.503

[34] is used, then K is derived from the security procedure on the control plane. relay-sess And from K relay-sess Derivation of K from the selected integrity algorithm relay-int , as specified in 3GPP TS 33.503

[34] . If K relay-sess If the exported and selected encryption protection algorithm is not an empty encryption protection algorithm, then the target UE will start from K. relay-sess Derivation of K using the selected encryption algorithm relay-enc As specified in 3GPP TS 33.503

[34] ; or

[0904] 2) If the user plane security procedure specified in 3GPP TS 33.503

[34] is used, then K is derived from the user plane security procedure. NRP-sess And from K NRP-sess The selected integrity algorithm is used to derive NRPIK, as specified in 3GPP TS 33.503

[34] . If K NRP-sess If the exported and selected encryption protection algorithm is not an empty encryption protection algorithm, then the target UE will start from K. NRP-sess The selected encryption algorithm is used to derive NRPEK, as specified in 3GPP TS 33.503

[34] .

[0905] The target UE will determine whether it can accept the ProSe direct link security mode command message through the following operations:

[0906] a) If the target UE's 5G ProSe direct signaling integrity protection policy is set to "signaling integrity protection required", then the selected security algorithm IE in the ProSe direct link security mode command message does not contain an empty integrity protection algorithm.

[0907] b) If the selected integrity protection algorithm is not an empty integrity protection algorithm, then the lower layer is required to use NRPIK (or K... relay-int (where applicable) and the selected integrity protection algorithm to verify the integrity of ProSe direct link security mode command messages;

[0908] c) Verify that the received UE security capabilities have not changed compared to the values ​​sent by the target UE to the initiating UE in the ProSe direct link establishment request message or ProSe direct link key update request message;

[0909] d) If the 5G ProSe direct link security mode control procedure is triggered during the 5G ProSe direct link establishment procedure,

[0910] 1) Verify that the received UE 5G ProSe direct signaling security policy has not changed compared to the value sent by the target UE to the initiating UE in the ProSe direct link establishment request message; and

[0911] 2) Verify the K contained in the ProSe direct link security mode command message. NRP-sess The LSB of the ID is not set to the same value as those received from another UE in response to the ProSe direct link establishment request message from the target UE; and

[0912] e) If the 5G ProSe direct link security mode control procedure is triggered during the 5G ProSe direct link key update procedure and the integrity protection algorithm currently used for the 5G ProSe direct link is different from the null integrity protection algorithm, then the security algorithm selected in the ProSe direct link security mode command message IE does not include the null integrity protection algorithm.

[0913] If the target UE does not contain K in the ProSe direct link establishment request message NRP ID, the target UE contains a re-authentication indication in the ProSe direct link key update request message or the initiating UE has selected to export:

[0914] a) New K NRP If the direct communication is not between the 5G ProSe remote UE and the 5G ProSe UE to the network relay UE, then the target UE will export K. NRP As specified in 3GPP TS 33.536

[37] ;

[0915] b) New K NRP If the direct communication is between a 5G ProSe remote UE and a 5G ProSe UE-to-network relay UE, and uses the security procedures on the user plane specified in 3GPP TS 33.503

[34] , then the target UE will export K NRP As specified in 3GPP TS 33.536

[37] ; or

[0916] c) New K NR_ProSe If the direct communication is between the 5G ProSe remote UE and the 5G ProSe UE to the network relay UE and uses the security procedures on the control plane specified in 3GPP TS 33.503

[34] , then the target UE will export K NR_ProSe As specified in 3GPP TS 33.536

[37] ; and

[0917] The target UE will select K NRP The two LSBs of ID ensure that the resulting K NRP The ID will be unique within the target UE. NRP The MSB of the ID and its selected K NRP The two LSBs of ID form K NRP ID, and will store with K NRP / K NR_ProSe The complete K NRP ID.

[0918] Note 1: If the direct communication is not between the 5G ProSe remote UE and the 5G ProSe UE to the network relay UE, then K NRP ID remains corresponding to K NRP The ID. If direct communication is between the 5G ProSe remote UE and the 5G ProSe UE to the network relay UE, then K NRP ID remains corresponding to K NRP (If a security program on the user plane is being used) or K NR_ProSe (If a security procedure on the control plane is used) ID.

[0919] If the GPI is included in the ProSe direct link security mode command message, and the direct communication is between the 5G ProSe remote UE and the 5G ProSe UE to the network relay UE, then according to the security procedures on the user plane specified in 3GPP TS 33.503

[34] , the target UE will derive the UP-PRUK from the GPI and obtain the UP-PRUK ID, and use the UP-PRUK to derive the KNRP .

[0920] If the target UE accepts the ProSe Direct Link Secure Mode Command message, then the target UE will create a ProSe Direct Link Secure Mode Completion message. In this message, the target UE:

[0921] a) If the 5G ProSe direct link security mode control procedure is triggered during the 5G ProSe direct link establishment procedure:

[0922] 1) If the 5G ProSe direct link is not used for 5G ProSe direct communication between 5G ProSe remote UEs and 5G ProSe UEs to network relay UEs, then it will include PQFI and the corresponding PC5QoS parameters; or

[0923] 2) If the 5G ProSe direct link is used for 5G ProSe Layer 3 remote UE and 5G ProSe Layer 3 UE to network relay UE, then it may include PQFI and corresponding PC5 QoS parameters.

[0924] Note 2: If the 5G ProSe direct link is used for 5G ProSe Layer 2 remote UE and 5G ProSe Layer 2 UE to network relay UE, then PQFI and the corresponding PC5 QoS parameters are not included.

[0925] b) If IP communication is used, and the 5G ProSe direct link security mode control procedure is triggered during the 5G ProSe direct link establishment procedure, then the IE will contain an IP address configured with one of the following values:

[0926] 1) "IPv6 router", provided that only the IPv6 address allocation mechanism is supported by the target UE, i.e., it acts as an IPv6 router;

[0927] 2) "DHCPv4 server", provided that only the IPv4 address allocation mechanism is supported by the target UE, that is, it acts as a DHCPv4 server;

[0928] 3) "DHCPv4 server and IPv6 router", provided that both IPv4 and IPv6 address allocation mechanisms are supported by the target UE; or

[0929] 4) Address allocation is not supported, provided that neither the IPv4 nor IPv6 address allocation mechanisms are supported by the target UE;

[0930] Note 3: If Ethernet or unstructured data unit type is used for communication, then the UE does not contain an IP address configuration IE or a link-local IPv6 address IE.

[0931] c) If IP communication is used, the IP address configuration IE is set to “address allocation not supported” and the 5G ProSe direct link security mode control procedure is triggered during the 5G ProSe direct link establishment procedure, then the link-local IPv6 address IE formed locally based on IETF RFC4862

[25] will be included.

[0932] d) If exporting a new K NRP Or receive a new K NRP or K NR_ProSe Then it will contain K NRP The two LSBs of the ID; and

[0933] e) If the 5G ProSe direct link security mode control procedure is triggered during the 5G ProSe direct link establishment procedure, then it will contain the UE 5G ProSe direct user plane security policy for this 5G ProSe direct link. In cases where different ProSe services are mapped to different 5G ProSe direct user plane security policies, when more than one ProSe identifier is included in the ProSe direct link establishment request message, each of the user plane security policies for those ProSe services will be compatible; for example, "No user plane integrity protection required" and "User plane integrity protection required" are incompatible.

[0934] If the selected integrity protection algorithm is not the empty integrity protection algorithm, then the target UE will use the K key it has already sent in the ProSe direct link establishment request message or the ProSe direct link key update request message. NRP-sess The MSB of the ID and the K received in the ProSe direct link security mode command message. NRP-sess ID's LSB formation K NRP-sess ID. The target UE will use K. NRP-sess The ID is used to identify the new security context.

[0935] After the ProSe direct link security mode completes message generation, the target UE transmits this message along with the following to the lower layer for transmission: the target UE's Layer 2 ID for 5G ProSe direct communication and the initiating UE's Layer 2 ID and NRPIK (or K) for 5G ProSe direct communication. relay-int (where applicable), NRPEK (or K) relay-enc (where applicable) K NRP-sessID, the selected security algorithm as specified in 3GPP TS 33.536

[37] , and an indication of activation of 5G ProSe direct signaling security protection for 5G ProSe direct links with new security contexts (if applicable).

[0936] Note 4: ProSe direct link security mode completion messages and other 5G ProSe direct signaling messages are protected for integrity and encrypted (if applicable) at the lower layer using a new security context.

[0937] If the 5G ProSe direct link security mode control procedure is triggered during the 5G ProSe direct link key update procedure, the target UE will provide the lower layer with an indication (if applicable) of the activation of 5G ProSe direct user plane security protection for the 5G ProSe direct link with the new security context, as well as the Layer 2 ID of the initiating UE for 5G ProSe direct communication and the Layer 2 ID of the target UE for 5G ProSe direct communication.

[0938] 7.2.10.4 The 5G ProSe direct link security mode control procedure initiated by the UE is completed.

[0939] Upon receiving the ProSe direct link security mode completion message, the initiating UE will stop timer T5089. If the selected integrity protection algorithm is not an empty integrity protection algorithm, the UE verifies the integrity of the ProSe direct link security mode completion message. If the integrity verification passes, the initiating UE will continue triggering the 5G ProSe direct link security mode control procedure. If the selected integrity protection algorithm is an empty integrity protection algorithm, the UE continues the procedure without verifying integrity protection.

[0940] Upon receiving the ProSe direct link security mode completion message, the initiating UE will delete its old security context (if it exists) for the target UE.

[0941] 7.2.10.5 5G ProSe direct link security mode control procedure not accepted by the target UE

[0942] If the ProSe direct link secure mode command message cannot be accepted, the target UE will send a ProSe direct link secure mode rejection message, and the target UE will abort any ongoing procedures that triggered the 5G ProSe direct link secure mode control procedure, unless the ongoing procedure is a 5G ProSe direct link establishment procedure and the target user information is not included in the ProSe direct link establishment request message. The ProSe direct link secure mode rejection message contains a PC5 signaling protocol reason IE, which indicates one of the following reason values:

[0943] #5: Lack of resources for 5G ProSe direct links;

[0944] #7: Integrity failure;

[0945] #8: UE security capability mismatch;

[0946] #9: K NRP-sess LSB conflict for ID;

[0947] #10: UE PC5 unicast signaling security policy mismatch;

[0948] #14: Authentication synchronization error; or

[0949] #111: Unspecified protocol error.

[0950] If this 5G ProSe direct link security mode control procedure is triggered during the 5G ProSe direct link establishment procedure and the maximum number of NR 5G ProSe direct links established has been reached, then the target UE will send a ProSe direct link security mode rejection message containing the PC5 signaling protocol reason value #5 "Lack of resources for 5G ProSe direct link".

[0951] If the ProSe direct link security mode command message cannot be accepted because the 5G ProSe direct link security mode control procedure is triggered during the 5G ProSe direct link establishment procedure, and the selected security algorithm IE in the ProSe direct link security mode command message includes the null integrity protection algorithm, and the target UE's 5G ProSe direct signaling integrity protection policy is set to "signaling integrity protection required", then the target UE will include PC5 signaling protocol reason #10 "UE PC5 unicast signaling security policy mismatch" in the ProSe direct link security mode rejection message.

[0952] If the ProSe direct link security mode command message cannot be accepted because the 5G ProSe direct link security mode control procedure is triggered during the 5G ProSe direct link key update procedure, the integrity protection algorithm currently used for the 5G ProSe direct link is different from the empty integrity protection algorithm, and the selected security algorithm IE in the ProSe direct link security mode command message includes the empty integrity protection algorithm, then the target UE will include PC5 signaling protocol reason #10 "UE PC5 unicast signaling security policy mismatch" in the ProSe direct link security mode rejection message.

[0953] If the target UE detects that the UE security capabilities received in the ProSe direct link security mode command message have changed compared to the most recent value sent by the target UE to the initiating UE in the ProSe direct link establishment request message or the ProSe direct link key update request message, then the target UE will include PC5 signaling protocol reason #8 "UE security capability mismatch" in the ProSe direct link security mode rejection message.

[0954] If the target UE detects K contained in the ProSe direct link security mode command message NRP-sess If the LSB of the ID is set to the same value as those received from another UE in response to the ProSe Direct Link Establishment Request message from the target UE, then the target UE will include the PC5 signaling protocol reason #9"K in the ProSe Direct Link Security Mode Reject message. NRP-sess LSB conflict of ID.

[0955] If the 5G ProSe direct link security mode control procedure is used for direct communication between a 5G ProSe remote UE and a 5G ProSe UE-to-network relay UE, and the ProSe direct link security mode command message cannot be accepted due to a synchronization error when processing the authentication vector (if present) contained in the GPI sent by the 5G ProSe UE-to-network relay UE to the 5G ProSe remote UE, then the target UE will include PC5 signaling protocol reason #14 "Authentication synchronization error" in the ProSe direct link security mode rejection message, and will include the RAND and AUTS parameters in the ProSe direct link security mode rejection message.

[0956] After the ProSe direct link security mode rejection message is generated, the target UE will pass this message along with the Layer 2 ID of the initiating UE for 5G ProSe direct communication and the Layer 2 ID of the target UE for 5G ProSe direct communication to the lower layer for transmission.

[0957] Upon receiving the ProSe direct link security mode rejection message, the initiating UE will stop timer T5089 and provide the lower layer with an indication to revoke the activation of 5G ProSe direct security protection and delete the security context used for the 5G ProSe direct link (if applicable):

[0958] a) If the PC5 signaling protocol reason in the ProSe direct link security mode rejection message is set to #9"K" NRP-sess "ID LSB conflict", then retransmit K NRP-sess ProSe direct link security mode command message with different values ​​for LSB of ID, and restart timer T5089;

[0959] b) If the PC5 signaling protocol reason IE in the ProSe direct link security mode rejection message is set to #14 "Authentication synchronization error", the message contains RAND and AUTS, and the 5G ProSe direct link security mode control procedure is used for direct communication between the 5G ProSe remote UE and the 5G ProSe UE to the network relay UE, then a fresh GPI can be retrieved from the PKMF by sending a key request message containing RAND and AUTS, as specified in 3GPP TS 33.503

[34] ; or

[0960] c) If the PC5 signaling protocol is the cause, IE is set to anything other than #9 "K". NRP-sess If the value is other than "ID LSB conflict" and "#14 Authentication synchronization error", then the ongoing process that triggered the 5G ProSe direct link security mode control procedure will be terminated.

[0961] 7.2.10.6 Abnormal situations

[0962] 7.2.10.6.1 Initiating Abnormal Situations at the UE

[0963] a) Timer T5089 expired.

[0964] The initiating UE will retransmit the ProSe direct link security mode command message and restart timer T5089. After reaching the maximum allowed number of retransmissions, the initiating UE will abort the 5GProSe direct link security mode control procedure, provide the lower layer with instructions to revoke the activation of 5G ProSe direct security protection and delete the security context used for 5G ProSe direct link (if applicable), and abort the ongoing procedure that triggered the initiation of the 5G ProSe direct link security mode control procedure.

[0965] Note 1: The maximum number of retransmissions allowed is specific to the UE implementation scheme.

[0966] b) This 5G ProSe direct link is no longer required until the 5G ProSe direct link security mode control procedure is completed.

[0967] The initiating UE will abort the procedure, provide the lower layer with an indication to revoke the activation of 5G ProSe direct security protection and delete the security context used for 5G ProSe direct links (if applicable), and terminate the ongoing procedure that triggered the initiation of the 5G ProSe direct link security mode control procedure.

[0968] c) If the ProSe direct link modification request message or the ProSe direct link identifier update request message is received while timer T5089 is running, then the initiating UE will discard the ProSe direct link modification request message or the ProSe direct link identifier update request message.

[0969] d) For the same 5G ProSe direct link, if the ProSe direct link release request message is received while timer T5089 is running, the initiating UE will stop timer T5089, terminate the 5G ProSe direct link security mode control procedure, and continue the 5G ProSe direct link release procedure.

[0970] Note 2: The anomalies described in item c) or d) occur only when the 5G ProSe direct link security mode control procedure is used to establish security between two UEs during the 5G ProSe direct link key update procedure.

[0971] Generally, 3GPP TS23.304 describes support for inter-UE relay. That is, when two (Layer 2 or Layer 3) Proximity-based (ProSe) end UEs cannot communicate directly with each other, a relay UE can be used to support communication between these two UEs. The inter-UE relay UE establishes a PC5 unicast link (e.g., or referred to as a PC5 connection, Layer 2 link, direct link, PC5 link, etc.) 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 related to the ProSe service between the two ProSe end UEs. If multiple source ProSe end UEs want to communicate with a target ProSe end UE, the PC5 link between the ProSe inter-UE relay UE and the target ProSe end UE can be shared, while the PC5 link can be established separately between the source ProSe end UE and the ProSe inter-UE relay UE. To establish a PC5 link, either a non-integrated discovery Layer 2 link establishment procedure as specified in Section 6.7.1 of 3GPP TS23.304 or an integrated discovery Layer 2 link establishment procedure as specified in Section 6.7.3 of 3GPP TS23.304 can be used (i.e., the former can be used if the Layer 2 link establishment procedure is initiated towards a relay UE or the source UE has selected a specific relay UE, and the latter can be used if the Layer 2 link establishment procedure is initiated towards any relay UE or the source UE has not yet discovered any relay UE). For shared PC5 links, a Layer 2 link modification procedure will be used. However, it is unclear how to initiate a Layer 2 link modification procedure when multiple source UEs are communicating with a single target UE.

[0972] For example, a first source UE may send a first Direct Communication Request (DCR) message. The first DCR message may contain user information of the first source UE, first user information of the target UE, user information of the relay UE, relay service code, etc. The source UE may obtain the first user information during the relay UE discovery procedure, or it may communicate with the target UE in previous direct communication between the first source UE and the target UE. The first DCR message may be received by the relay UE. The relay UE may then send a second DCR message addressed to a broadcast address (i.e., a predefined or preconfigured broadcast Layer 2 ID in both the relay UE and the target UE) or a Layer 2 ID associated with the target UE. The second DCR message may contain user information of the first source UE, user information of the relay UE, first user information of the target UE, relay service code, etc. The target UE may receive the second DCR message. In response to receiving the second DCR message, the target UE may establish a second-hop PC5 link with the relay UE. Similarly, the relay UE can then establish a first hop PC5 link with the first source UE, enabling the first source UE and the target UE to communicate with each other via the relay UE.

[0973] The second source UE may be able to send a third DCR message. This third DCR message may contain user information of the second source UE, second user information of the target UE, user information of the relay UE, relay service code, etc. The relay UE can receive the third DCR message. However, the relay UE may not be aware that the first and second user information belong to the same target UE. Therefore, the relay UE may still send a fourth DCR message addressed to the same broadcast address. This fourth DCR message may contain user information of the second source UE, user information of the relay UE, second user information of the target UE, relay service code, etc. For this purpose, the target UE can establish another PC5 link with the relay UE to communicate with the second source UE via the relay UE. Because using a shared PC5 link is beneficial in terms of resource efficiency, it is advisable for the relay UE to initiate a Layer 2 link modification procedure with the target UE in some way rather than initiating a Layer 2 link establishment procedure.

[0974] The target UE can recognize that the fourth DCR message itself is based on the second user information of the target UE contained in this DCR message. Therefore, the target UE can send a PC5-S message to the relay UE in response to receiving the fourth DCR message (if the target UE wants to reuse the second-hop PC5 link with the relay UE). In addition to including the user information of the second source UE in the PC5-S message, the PC5-S message may also include the first user information of the target UE, so that the relay UE can know that these two user information are associated with a single target ProSe UE (i.e., the target UE). The PC5-S message may further include the second user information of the target UE. If the user information of the target ProSe UE included in the fourth DCR message is not any user information belonging to or associated with the target UE, the target UE can ignore / discard the fourth DCR message.

[0975] In response to receiving a PC5-S message from the target UE, the relay UE can initiate a Layer 2 link modification procedure toward the target UE. The relay UE can send a Link Modification Request (LMR) message to the target UE on the second-hop PC5 link. The LMR message may include user information of the second source UE, second user information of the target UE, relay service code, etc. The target UE can respond with a Link Modification Acceptance (LMA) message to the relay UE on the second-hop PC5 link.

[0976] In response to receiving an LMA message from the target UE, the relay UE may establish a second first-hop PC5 link with the second source UE. More specifically, the PC5-S message may contain a reason value instructing the relay UE to (reconsider) initiating a Layer 2 link modification procedure. The PC5-S message may be a direct communication rejection message or a ProSe direct link establishment rejection message.

[0977] In one embodiment, the first-hop PC5 link can be a PC5 connection established between the source ProSe UE and the inter-UE relay UE. The second-hop PC5 link can be a PC5 connection established between the inter-UE relay UE and the target ProSe UE.

[0978] In one embodiment, user information may be a user information ID, an application layer ID, or an upper layer ID.

[0979] Figure 21This is a flowchart 2100 of a method for a relay UE. In step 2105, the relay UE sends or broadcasts a first message establishing a PC5 connection with another relay UE for communication with a first source UE via the relay UE. In step 2110, the relay UE receives a second message from the target UE confirming the PC5 connection. In step 2115, the relay UE sends or broadcasts a third message establishing another PC5 connection with another relay UE for communication with a second source UE via the relay UE, wherein the third message contains second user information of the target source UE. In step 2120, the relay UE receives a fourth message from the target UE, wherein the fourth message contains information indicating that the second user information belongs to or is associated with the target UE. In step 2125, in response to receiving the fourth message, the relay UE sends a fifth message to the target UE modifying the PC5 connection.

[0980] In one embodiment, the first message may include first user information of the target UE, user information of the first source UE, user information of the relay UE, relay service code, etc. The second message may include first user information of the target UE, user information of the relay UE, relay service code, etc. The third message may include user information of the second source UE, user information of the relay UE, relay service code, etc. The fourth message may include first user information, second user information, user information of the first source UE, user information of the second source UE, user information of the relay UE, relay service code, cause value, etc. The fifth message may include second user information, user information of the second source UE, relay service code, etc.

[0981] In one embodiment, the first / third message may be a direct communication request message or a ProSe direct link establishment request message. The second message may be a direct communication acceptance message or a ProSe direct link establishment acceptance message. The fourth message may be a direct communication rejection message or a ProSe direct link establishment rejection message. The fifth message may be a link modification request message or a ProSe direct link modification request message.

[0982] In one embodiment, the first / second source UE or target UE can be a 5G ProSe UE. The relay UE can be a 5G ProSe UE-to-UE relay UE.

[0983] In one embodiment, the cause value may instruct the relay UE to initiate a link modification procedure toward the target UE. The link modification procedure may involve adding a second source UE to the PC5 connection. The user information may be a user information ID or an application layer ID.

[0984] Return to reference Figure 3 and 4In one example from the perspective of the relay UE, the relay UE 300 includes program code 312 stored in memory 310. CPU 308 executes program code 312 such that the relay UE is able to: (i) send or broadcast a first message establishing a PC5 connection with the relay UE for communication with a first source UE via the relay UE; (ii) receive a second message from the target UE confirming the completion of the PC5 connection; (iii) send or broadcast a third message establishing another PC5 connection with the relay UE for communication with a second source UE via the relay UE, wherein the third message contains second user information of the target source UE; (iv) receive a fourth message from the target UE, wherein the fourth message contains information indicating that the second user information belongs to or is associated with the target UE; and (v) in response to receiving the fourth message, send a fifth message to the target UE modifying the PC5 connection. Furthermore, CPU 308 executes program code 312 to perform all of the above actions and steps or other actions and steps described herein.

[0985] Alternatively, once the target UE establishes a second-hop PC5 link with the relay UE, or after the target UE establishes a second-hop PC5 link with the relay UE, or when the target UE establishes a second-hop PC5 link with the relay UE, or if the target UE establishes a second-hop PC5 link with the relay UE, the target UE may provide the relay UE with one or more user information belonging to or associated with the target UE via, for example, PC5-S messages (e.g., direct communication request / accept message, link modification request / accept message, link identifier update request / response / acknowledgment message, etc.). Given the one or more user information belonging to or associated with the target UE, the relay UE may determine whether to initiate a Layer 2 link establishment procedure or a link modification procedure toward the target UE when the relay UE receives a third DCR message from the second source UE. That is, if the user information of the target ProSe UE included in the third DCR message can match any of the one or more user information belonging to or associated with the target UE, then the relay UE can initiate a link modification procedure toward the target UE; otherwise, the relay UE can initiate a Layer 2 link establishment procedure.

[0986] On the other hand, a third source UE may be able to initiate service with an undetermined target ProSe UE. In this case, the third source UE can send a fifth DCR message that does not contain any user information of the target ProSe UE. The relay UE can receive the fifth DCR message and then send a sixth DCR message addressed to the broadcast address. The target UE can also receive the sixth DCR message from the relay UE and may be interested in communicating with the third source UE. If the target UE also considers reusing the second-hop PC5 link to communicate with the third source UE via the relay UE, then the target UE can apply the above solution for the relay UE to initiate a Layer 2 link modification procedure. Regarding latency reduction, if the relay UE receives a DCR message from the source ProSe UE that does not indicate a specific target ProSe UE, then the relay UE can not only initiate a Layer 2 link establishment procedure (for broadcasting the second-hop DCR message to find if any target ProSe UE is interested in the relevant service with the source ProSe UE), but also initiate one or more Layer 2 link modification procedures toward the connected target UE. Based on this concept, a relay UE can send an LMR message to add a third source UE to a target UE. If the target UE accepts reusing the second-hop PC5 link to communicate with the third source UE via the relay UE, then the target UE can respond to the relay UE with an LMA message.

[0987] Alternatively, the relay UE can first complete one or more link modification procedures toward the connected target UE, and then initiate a Layer 2 link establishment procedure (or broadcast a second-hop DCR message) to check if any other target ProSe UE (which has not yet established a PC5 link with the relay UE) is also interested in communicating with the third source UE. In this way, because the third source UE has already been added to the second-hop PC5 link by using the link modification procedure toward the target UE, the target UE can ignore the received broadcast second-hop DCR message.

[0988] Figure 22 This is a flowchart 2200 of a method for a relay UE. In step 2205, the relay UE establishes a PC5 connection with the target UE for communication with the first source UE via the relay UE. In step 2210, the relay UE receives a first message from the second source UE establishing communication with any target ProSe UE. In step 2215, in response to receiving the first message, the relay UE initiates a link modification procedure toward the target UE.

[0989] In one embodiment, the relay UE may initiate both a Layer 2 link establishment procedure and a link modification procedure toward a target UE in response to receiving a first message. In response to receiving the first message, the relay UE may initiate the Layer 2 link establishment procedure after the link modification procedure toward the target UE (and another link modification procedure toward any target UE connected to the relay UE) is completed. The Layer 2 link establishment procedure may be initiated toward an undetermined target ProSe UE.

[0990] In one embodiment, the first message may not contain any user information for the target ProSe UE. The first message may be a direct communication request message or a ProSe direct link establishment request message.

[0991] In one embodiment, user information may be a user information ID or an application layer ID.

[0992] Return to reference Figure 3 and 4 In one example from the perspective of the relay UE, the relay UE 300 includes program code 312 stored in memory 310. CPU 308 executes program code 312 such that the relay UE is able to: (i) establish a PC5 connection with a target UE for communication with a first source UE via the relay UE; (ii) receive a first message from a second source UE establishing communication with any target ProSe UE; and (iii) in response to receiving the first message, initiate a link modification procedure toward the target UE. Furthermore, CPU 308 executes program code 312 to perform all of the above actions and steps or other actions and steps described herein.

[0993] Figure 23 This is a flowchart 2300 of a method for a target UE. In step 2305, the target UE receives from a relay UE a first message establishing a PC5 connection with the relay UE for communication with a first source UE via the relay UE, wherein the PC5 connection is associated with first user information of the target UE. In step 2310, the target UE receives from the relay UE a second message establishing another PC5 connection with the relay UE for communication with a second source UE via the relay UE. In step 2315, in response to receiving the second message, if the second message contains second user information belonging to or associated with the target UE, then the target UE sends a third message to the relay UE.

[0994] In one embodiment, the target UE may receive a fourth message from the relay UE requesting modification of the PC5 connection, wherein the fourth message contains second user information.

[0995] In one embodiment, the first message may include user information of the first source UE, user information of the relay UE, relay service code, etc. The second message may include user information of the second source UE, user information of the relay UE, relay service code, etc. The third message may include first user information, second user information, user information of the first source UE, user information of the second source UE, user information of the relay UE, relay service code, cause value, etc. The fourth message may include second user information, user information of the second source UE, relay service code, etc.

[0996] In one embodiment, the first / second message may be a direct communication request message or a ProSe direct link establishment request message. The third message may be a direct communication rejection message or a ProSe direct link establishment rejection message. The fourth message may be a link modification request message or a ProSe direct link modification request message.

[0997] In one embodiment, the first / second source UE or target UE can be a 5G ProSe UE. The relay UE can be a 5G ProSe UE-to-UE relay UE. The reason value can instruct the relay UE to initiate a link modification procedure toward the target UE. The link modification procedure can be adding a second source UE to the PC5 connection. The user information can be a user information ID or an application layer ID.

[0998] Return to reference Figure 3 and 4 In one example from the perspective of the target UE, the target UE 300 includes program code 312 stored in memory 310. CPU 308 executes program code 312 such that the target UE is able to: (i) receive from a relay UE a first message establishing a PC5 connection with the relay UE for communication with a first source UE via the relay UE, wherein the PC5 connection is associated with first user information of the target UE; (ii) receive from the relay UE a second message establishing another PC5 connection with the relay UE for communication with a second source UE via the relay UE; and (iii) in response to receiving the second message, if the second message contains second user information belonging to or associated with the target UE, send a third message to the relay UE. Furthermore, CPU 308 executes program code 312 to perform all of the above actions and steps or other actions and steps described herein.

[0999] Figure 24This is a flowchart 2400 of a method for relaying a UE. In step 2405, the relay UE establishes a PC5 connection with the target UE to support inter-UE relay communication between the first source UE and the target UE via the relay UE. In step 2410, the relay UE sends or broadcasts a first request message to the target UE requesting the establishment of another PC5 connection with the relay UE to support inter-UE relay communication with a second source UE via the relay UE. In step 2415, the relay UE receives a rejection message from the target UE, wherein the rejection message contains information instructing the relay UE to initiate a Layer 2 link modification procedure on the PC5 connection. In step 2420, in response to receiving the rejection message, the relay UE sends a second request message to the target UE requesting modification of the PC5 connection.

[1000] In one embodiment, the first request message may include user information of the second source UE, user information of the relay UE, relay service code, etc. The rejection message may include user information of the second source UE, user information of the target UE, user information of the relay UE, reason value, etc. The second request message may include user information of the second source UE, user information of the target UE, etc.

[1001] In one embodiment, the first request message may be a direct communication request message or a ProSe direct link establishment request message, the rejection message may be a direct communication rejection message or a ProSe direct link establishment rejection message, and the second request message may be a link modification request message or a ProSe direct link modification request message.

[1002] Return to reference Figure 3 and 4 In one example from the perspective of the relay UE, the relay UE 300 includes program code 312 stored in memory 310. CPU 308 executes program code 312 such that the relay UE is able to: (i) establish a PC5 connection with a target UE to support inter-UE relay communication between a first source UE and a target UE via the relay UE; (ii) send or broadcast a first request message to the target UE requesting the establishment of another PC5 connection with the relay UE to support inter-UE relay communication between the relay UE and a second source UE via the relay UE; (iii) receive a rejection message from the target UE, wherein the rejection message contains information instructing the relay UE to initiate a Layer 2 link modification procedure on the PC5 connection; and (iv) in response to receiving the rejection message, send a second request message to the target UE requesting modification of the PC5 connection. Furthermore, CPU 308 executes program code 312 to perform all of the above actions and steps or other actions and steps described herein.

[1003] Figure 25This is a flowchart 2500 of a method for a target UE. In step 2505, the target UE establishes a PC5 connection with a relay UE to support inter-UE relay communication between the first source UE and the target UE via the relay UE. In step 2510, the target UE receives a request message from the relay UE requesting to establish another PC5 connection with the relay UE to support inter-UE relay communication with a second source UE via the relay UE. In step 2515, in response to receiving the request message, if a PC5 connection exists, the target UE sends a rejection message to the relay UE.

[1004] In one embodiment, the request message may include user information of the second source UE, user information of the relay UE, relay service code, etc. The rejection message may include user information of the second source UE, user information of the target UE, user information of the relay UE, reason value, etc.

[1005] In one embodiment, the request message may be a direct communication request message or a ProSe direct link establishment request message, and the rejection message may be a direct communication rejection message or a ProSe direct link establishment rejection message.

[1006] Return to reference Figure 3 and 4 In one example from the perspective of the target UE, the target UE 300 includes program code 312 stored in memory 310. CPU 308 executes program code 312 such that the target UE is able to: (i) establish a PC5 connection with a relay UE to support inter-UE relay communication between the first source UE and the target UE via the relay UE; (ii) receive from the relay UE a request message requesting the establishment of another PC5 connection with the relay UE to support inter-UE relay communication with a second source UE via the relay UE; and (iii) in response to receiving the request message, send a rejection message to the relay UE if a PC5 connection exists. Furthermore, CPU 308 executes program code 312 to perform all of the above actions and steps or other actions and steps described herein.

[1007] Various aspects of this disclosure have been described above. It should be understood that the teachings herein can be implemented 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, any number of aspects set forth herein can be used to implement an apparatus or practice. Furthermore, this apparatus or practice can be implemented or practiced by using other structures, functions, or structures and functions other than or different from one or more 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.

[1008] Those skilled in the art will understand that information and signals can be represented using any of a variety of different techniques and skills. 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.

[1009] Those skilled in the art will further understand that the various illustrative logic blocks, modules, processors, components, circuits, and algorithm steps described in conjunction with the aspects disclosed herein can be implemented as electronic hardware (e.g., a digital implementation, an analog implementation, or a combination of both, which may be designed using source decoding or some other technique) and various forms of program or design code with instructions (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 functionality of the various illustrative components, blocks, modules, circuits, and steps has been described above in general terms. Whether this functionality is implemented as hardware or software depends on the specific application and the design constraints imposed on the overall system. Those skilled in the art can implement the described functionality in different ways for each specific application, but such implementation decisions should not be construed as causing a deviation from the scope of this disclosure.

[1010] Furthermore, the various illustrative logic blocks, modules, and circuits described in connection with the aspects disclosed herein may 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 capable of executing 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, a combination of multiple microprocessors, one or more microprocessors combined with a DSP core, or any other such configuration.

[1011] It should be understood that any particular order or hierarchy of steps in any disclosed process is an instance of an example method. It should be understood that a particular order or hierarchy of steps in the process may be rearranged based on design preferences while remaining within the scope of this disclosure. The accompanying method claims present the elements of the various steps in an example order, but are not intended to limit one to the particular order or hierarchy presented.

[1012] The steps of the methods or algorithms described in conjunction with the aspects disclosed herein can be implemented directly in hardware, with software modules executed by a processor, or a combination of both. Software modules (e.g., containing executable instructions and associated data) and other data can reside in data memory, such as RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disks, removable disks, CD-ROMs, or any other form of computer-readable storage medium known in the art. Example storage media can be coupled to a machine such as a computer / processor (for convenience, this 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. Example storage media can be integrated with the processor. The processor and storage medium can reside in an ASIC. The ASIC can reside in a user equipment. Alternatively, the processor and storage medium can reside in a user equipment as discrete components. Additionally, 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.

[1013] 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 changes, uses, or adaptations to the invention that generally follow the principles of the invention and include such deviations from this disclosure that fall within the scope of known and customary practice in the art to which this invention pertains.

[1014] Cross-references to related applications

[1015] This application claims the benefit of U.S. Provisional Patent Applications Nos. 63 / 526,597 and 63 / 526,621, filed July 13, 2023, the entire disclosure of which is incorporated herein by reference in its entirety.

Claims

1. A method for relay user equipment, characterized in that, include: The relay user equipment establishes a PC5 connection with the target user equipment to support inter-user equipment relay communication between the first source user equipment and the target user equipment via the relay user equipment. The relay user equipment sends or broadcasts a first request message requesting the establishment of another PC5 connection with the relay user equipment to support inter-user equipment relay communication via the relay user equipment to the second source user equipment. The relay user equipment receives a rejection message from the target user equipment, wherein the rejection message contains information instructing the relay user equipment to initiate a layer 2 link modification procedure on the PC5 connection; as well as In response to receiving the rejection message, the relay user equipment sends a second request message to the target user equipment requesting modification of the PC5 connection.

2. The method according to claim 1, characterized in that, The first request message includes user information of the second source user equipment, user information of the relay user equipment, and / or relay service code.

3. The method according to claim 2, characterized in that, The rejection message includes the user information of the second source user equipment, the user information of the target user equipment, the user information of the relay user equipment, and / or the reason value.

4. The method according to claim 3, characterized in that, The second request message contains the user information of the second source user equipment and / or the user information of the target user equipment.

5. The method according to claim 1, characterized in that, The first request message is a direct communication request message or a direct link establishment request message based on proximity services, the rejection message is a direct communication rejection message or a direct link establishment rejection message based on proximity services, and the second request message is a link modification request message or a direct link modification request message based on proximity services.

6. A method for a target end user equipment, characterized in that, include: The target user equipment establishes a PC5 connection with the relay user equipment to support inter-user equipment relay communication between the first source user equipment and the target user equipment via the relay user equipment. The target user equipment receives a first request message from the relay user equipment requesting to establish another PC5 connection with the relay user equipment to support inter-user equipment relay communication via the relay user equipment to the second source user equipment. In response to receiving the first request message, if the PC5 connection exists, the target user equipment sends a rejection message to the relay user equipment, wherein the rejection message contains information instructing the relay user equipment to initiate a layer 2 link modification procedure on the PC5 connection; as well as The target user equipment receives from the relay user equipment a second request message requesting modification of the PC5 connection in response to receiving the rejection message.

7. The method according to claim 6, characterized in that, The first request message includes user information of the second source user equipment, user information of the relay user equipment, and / or relay service code.

8. The method according to claim 7, characterized in that, The rejection message includes the user information of the second source user equipment, the user information of the target user equipment, the user information of the relay user equipment, and / or the reason value.

9. The method according to claim 6, characterized in that, The first request message is a direct communication request message or a direct link establishment request message based on proximity services, and the rejection message is a direct communication rejection message or a direct link establishment rejection message based on proximity services.

10. A target-end user equipment, characterized in that, include: Control circuit; A processor, which is installed in the control circuit; as well as A memory, which is mounted in the control circuit and operatively coupled to the processor; The processor is configured to execute program code stored in the memory to perform the following operations: Establish a PC5 connection with the relay user equipment to support inter-user equipment relay communication between the first source user equipment and the target user equipment via the relay user equipment; A first request message is received from the relay user equipment to establish another PC5 connection with the relay user equipment to support inter-user equipment relay communication between the relay user equipment and the second source user equipment. In response to receiving the first request message, if the PC5 connection exists, a rejection message is sent to the relay user equipment, wherein the rejection message contains information instructing the relay user equipment to initiate a layer 2 link modification procedure on the PC5 connection; as well as The relay user equipment receives a second request message in response to receiving the rejection message, requesting modification of the PC5 connection.

11. The target end user equipment according to claim 10, characterized in that, The first request message includes user information of the second source user equipment, user information of the relay user equipment, and / or relay service code.

12. The target end user equipment according to claim 11, characterized in that, The rejection message includes the user information of the second source user equipment, the user information of the target user equipment, the user information of the relay user equipment, and / or the reason value.

13. The target end user equipment according to claim 10, characterized in that, The first request message is a direct communication request message or a direct link establishment request message based on proximity services, and the rejection message is a direct communication rejection message or a direct link establishment rejection message based on proximity services.

Images