Method and device for adding target-end user equipment for relay communication between user equipment

Abstract

Methods and apparatus for relay end user equipment are disclosed. In one embodiment, a relay user equipment receives a first message from a source user equipment, where the first message will establish a first hop PC5 connection with the relay user equipment for supporting inter-user equipment relay communications with any target user equipment. And the relay user equipment further establishes a first second hop PC5 connection with the first target-end user equipment for supporting inter-user equipment relay communication with the source-end user equipment. And the relay user equipment also establishes a second second hop PC5 connection with the second target-end user equipment for supporting inter-user equipment relay communication with the source-end user equipment. In addition, the relay user equipment sends a second message to the source user equipment, where the second message will complete the establishment of the first hop PC5 connection and includes the user information of the first target user equipment and the user information of the second target user equipment.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 528,016 filed on July 20, 2023 and U.S. Provisional Patent Application No. 63 / 541,228 filed on September 28, 2023, the entire disclosures of the above U.S. Provisional Patent Applications are incorporated herein by reference in their entirety. Technical Field

[0003] The present disclosure generally relates to wireless communication networks, and more particularly, to a method and apparatus for adding multiple target UEs to a relay user equipment (UE) for inter-UE relay communication in a wireless communication system. Background Art

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

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

[0006] A method and apparatus for a relay-end user equipment are disclosed. In one embodiment, a relay UE receives a first message from a source-end UE, wherein the first message will establish a 1st-hop PC5 connection with the relay UE for supporting inter-UE (U2U) relay communication with any target-end UE. The relay UE further establishes a first 2nd-hop PC5 connection with a first target-end UE for supporting U2U relay communication with the source-end UE. The relay UE also establishes a second 2nd-hop PC5 connection with a second target-end UE for supporting U2U relay communication with the source-end UE. In addition, the relay UE sends a second message to the source-end UE, wherein the second message will complete the establishment of the 1st-hop PC5 connection and contain user information of the first target-end UE and user information of the second target-end UE. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 A drawing showing a wireless communication system according to an exemplary embodiment is shown.

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

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

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

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

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

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

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

[0015] Fig. 9 It is 3GPP TS23.304V18.2.0 Figure 6 .Reproduction of 4.3.4-1.

[0016] Fig.10 It is 3GPP TS23.304V18.2.0 Figure 6 .7.1.1-1 is reproduced.

[0017] Fig.11 It is 3GPP TS23.304V18.2.0 Figure 6 .7.1.4-1 is reproduced.

[0018] Fig.12 It is 3GPP TS23.304V18.2.0 Figure 6 .7.3.2-1 is reproduced.

[0019] Fig.13 It is 3GPP TS23.304V18.2.0 Figure 6 .7.3.3-1 is reproduced.

[0020] Fig.14 It is 3GPP TS24.554V18.1.0 Figure 7 .Reproduction of 2.2.2.2.

[0021] Fig.15 It is 3GPP TS24.554V18.1.0 Figure 7 .Reproduction of 2.3.2.1.

[0022] Fig.16 It is 3GPP TS24.554V18.1.0 Figure 7 .Reproduction of 2.3.2.2.

[0023] Fig.17 It is 3GPP TS24.554V18.1.0 Figure 7 .Reproduction of 2.10.2.1.

[0024] Fig.18 This is a reproduction of Table 10.3.1.1.1 of 3GPP TS24.554 V18.1.0.

[0025] Fig.19 This is a reproduction of Table 10.3.2.1.1 of 3GPP TS24.554 V18.1.0.

[0026] Fig. 20A is an accompanying message diagram according to an exemplary embodiment.

[0027] Fig. 20B is an accompanying message diagram according to an exemplary embodiment.

[0028] Fig.21 is an accompanying message diagram according to an exemplary embodiment.

[0029] Fig. 22 is an accompanying message diagram according to an exemplary embodiment.

[0030] Fig.23 is a flow chart according to an exemplary embodiment.

[0031] Fig.24 is a flow chart according to an exemplary embodiment.

[0032] Fig.25 is a flow chart according to an exemplary embodiment.

[0033] Fig.26is a flow chart according to an exemplary embodiment. DETAILED DESCRIPTION

[0034] The exemplary wireless communication systems and devices described below employ wireless communication systems that support broadcast services. Wireless communication systems are widely deployed to provide various types of communications, such as voice, data, etc. These systems can be based on code division multiple access (CDMA), time division multiple access (TDMA), orthogonal frequency division multiple access (OFDMA), 3GPP Long Term Evolution (LTE) radio access, 3GPP Long Term Evolution Advanced (LTE-A), 3GPP2 Ultra Mobile Broadband (UMB), WiMax, 3GPP New Radio (NR), or some other modulation technology.

[0035] In particular, the exemplary wireless communication systems and devices described below may be designed to support one or more standards, such as those provided by a consortium named “3rd Generation Partnership Project” referred to herein as 3GPP, including: TS 23.304 V18.2.0, “Proximity-based Services (ProSe) in 5G System (5GS) (Release 18)”; and TS 24.554 V18.1.0, “Proximity Services (ProSe) in 5G System (5GS) Protocol Aspects; Stage 3 (Release 18)”. The standards and documents listed above are hereby expressly incorporated by reference in their entirety.

[0036] Figure 1 1 shows a multiple access wireless communication system according to an embodiment of the present invention. An access network 100 (AN) includes multiple antenna groups, one including 104 and 106, another including 108 and 110, and another including 112 and 114. Figure 1In the figure, only two antennas are shown for each antenna group, however, each antenna group may utilize more or fewer antennas. Access terminal 116 (Access terminal, 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 (Access terminal, AT) 122 communicates with antennas 106 and 108, where antennas 106 and 108 transmit information to access terminal (Access terminal, AT) 122 via forward link 126 and receive information from access terminal (Access terminal, AT) 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 frequency different from the frequency used by reverse link 118.

[0037] Each group of antennas and / or the area in which they are designed to communicate is often referred to as a sector of the access network. In an embodiment, the antenna groups are each designed to communicate with access terminals in a sector of the area covered by the access network 100.

[0038] In communicating over forward links 120 and 126, the transmit antennas of access network 100 may utilize beamforming in order to improve the signal-to-noise ratio of the forward links for the different access terminals 116 and 122. Also, an access network that uses beamforming to transmit to access terminals that are randomly dispersed throughout the coverage area of ​​the access network may generate less interference to access terminals in neighboring cells than an access network that transmits to all of its access terminals via a single antenna.

[0039] An access network (AN) may be a fixed station or base station for communicating with a terminal, and may also be referred to as an access point, a Node B, a base station, an enhanced base station, an evolved Node B (eNB), a network node, a network, or some other term. An access terminal (AT) may also be referred to as a user equipment (UE), a wireless communication device, a terminal, an access terminal, or some other term.

[0040] Figure 2 2 is a simplified block diagram of an embodiment of a transmitter system 210 (also referred to as an access network) and a receiver system 250 (also referred to as an access terminal (AT) or user equipment (UE)) in a MIMO system 200. At the transmitter system 210, traffic data for a number of data streams is provided from a data source 212 to a transmit (TX) data processor 214.

[0041] In one embodiment, each data stream is transmitted through a respective transmit antenna.TX data processor 214 formats, codes, and interleaves the traffic data for each data stream based on a particular coding scheme selected for that data stream to provide coded data.

[0042] The coded data for each data stream may be multiplexed with pilot data using OFDM techniques. The pilot data is typically a known data pattern that is processed in a known manner and may be used at the receiver system to estimate the channel response. The multiplexed pilot and coded data for each data stream is then modulated (i.e., symbol mapped) based on a particular modulation scheme (e.g., BPSK, QPSK, M-PSK, or M-QAM) selected for that data stream to provide modulation symbols. Instructions executed by processor 230 may determine the data rate, coding, and modulation for each data stream.

[0043] The modulation symbols for all data streams are then provided to a TX MIMO processor 220, which may further process the modulation symbols (e.g., for OFDM). The TX MIMO processor 220 then converts the N T The modulation symbol stream is provided to N T transmitters (TMTR) 222a through 222t. In certain embodiments, TX MIMO processor 220 applies beamforming weights to the symbols of the data streams and to the antenna from which the symbol is being transmitted.

[0044] Each transmitter 222 receives and processes a respective symbol stream to provide one or more analog signals, and further conditions (eg, amplifies, filters, and up-converts) the analog signals to provide a modulated signal suitable for transmission via a MIMO channel. T The antennas 224a to 224t transmit the N signals from the transmitters 222a to 222t. T a modulated signal.

[0045] At the receiver system 250, N R The transmitted modulated signals are received by each antenna 252a through 252r and the received signal from each antenna 252 is provided to a respective receiver (RCVR) 254a through 254r. Each receiver 254 conditions (e.g., filters, amplifies, and downconverts) a respective received signal, digitizes the conditioned signal to provide samples, and further processes the samples to provide a corresponding “received” symbol stream.

[0046] RX data processor 260 then extracts the N R The receiver 254 receives and processes N R received symbol streams to provide N TThe RX data processor 260 then demodulates, deinterleaves, and decodes each detected symbol stream to recover the traffic data for the data stream. The processing by the RX data processor 260 is complementary to the processing performed by the TX MIMO processor 220 and the TX data processor 214 at the transmitter system 210.

[0047] Processor 270 periodically determines which pre-coding matrix to use (discussed below). Processor 270 formulates a reverse link message comprising a matrix index portion and a rank value portion.

[0048] The reverse link message may include various types of information about the communication link and / or the received data stream. The reverse link message is then processed by the TX data processor 238 (which also receives traffic data for a number of data streams from the data source 236), modulated by the modulator 280, conditioned by the transmitters 254a to 254r, and transmitted back to the transmitter system 210.

[0049] At the transmitter system 210, the modulated signal from the receiver system 250 is received by the antenna 224, conditioned by the receiver 222, demodulated by the demodulator 240, and processed by the RX data processor 242 to extract the reverse link message transmitted by the receiver system 250. The processor 230 then determines which precoding matrix to use to determine the beamforming weights and then processes the extracted message.

[0050] Go to Figure 3 , this figure shows an alternative simplified functional block diagram of a communication device according to one embodiment of the present invention. Figure 3 As shown, the communication device 300 in the wireless communication system can be used to implement Figure 1 UE (or AT) 116 and 122 in or Figure 1 The base station (or AN) 100 in the wireless communication system is preferably an NR system. The communication device 300 may include an input device 302, an output device 304, a control circuit 306, a central processing unit (CPU) 308, a memory 310, a program code 312, and a transceiver 314. The control circuit 306 executes the program code 312 in the memory 310 through the CPU 308, thereby controlling the operation of the communication device 300. The communication device 300 can receive signals input by the user through the input device 302 (for example, a keyboard or a keypad), and can output images and sounds through the output device 304 (for example, a monitor or a speaker). The transceiver 314 is used to receive and transmit wireless signals, pass the received signals to the control circuit 306, and wirelessly output the signals generated by the control circuit 306. The communication device 300 in the wireless communication system can also be used to implement Figure 1 AN 100 in.

[0051] Figure 4 According to one embodiment of the present invention, Figure 3 4. In this embodiment, program code 312 includes application layer 400, layer 3 portion 402, and layer 2 portion 404, and is coupled to layer 1 portion 406. Layer 3 portion 402 typically performs radio resource control. Layer 2 portion 404 typically performs link control. Layer 1 portion 406 typically performs physical connectivity.

[0052] 3GPP TS23.304 introduces the following:

[0053] 4.2.8 5G ProSe Inter-UE Relay Reference Architecture

[0054] Figure 4 .2.8-1 shows the layer 2 and layer 3 5G ProSe inter-UE relay reference architecture. 5G ProSe end UEs communicate with each other via the 5G ProSe inter-UE relay.

[0055] [3GPP TS23.304 V18.2.0 titled "Reference architecture for 5G ProSe inter-UE relay" Figure 4 .2.8-1 is reproduced as Figure 5 ]

[0056] Each 5G ProSe end UE and 5G ProSe inter-UE relay may have a subscription from the same PLMN or different PLMNs.

[0057] […]

[0058] 5.8.4 Identifiers for 5G ProSe Inter-UE Relay Discovery

[0059] 5.8.4.1 General

[0060] The 5G ProSe inter-UE relay discovery message contains two identifier sets, namely the direct discovery set and the inter-UE relay discovery set.

[0061] - The direct discovery identifier set is part of the content of the 5G ProSe direct discovery message, as defined in clause 5.8.1.

[0062] -The inter-UE relay discovery identifier set contains extended information to support 5G ProSe inter-UE relay discovery and direct discovery.

[0063] The 5G ProSe inter-UE relay shall modify the inter-UE relay discovery identifier set and forward the direct discovery identifier set and the inter-UE relay discovery identifier set during the discovery procedure.

[0064] 5.8.4.2 Common Identifiers for 5G ProSe Inter-UE Relay Discovery

[0065] The following parameters are used for the 5G ProSe Inter-UE Relay Discovery Notification message (Model A), where the source layer 2 ID and destination layer 2 ID are used to send and receive the message, and the user information ID and relay service code are included in the message:

[0066] - Source Layer 2 ID: The 5G ProSe Inter-UE Relay selects the Source Layer 2 ID for the 5G ProSe Inter-UE Relay Discovery Notification message by itself.

[0067] - Destination Layer 2 ID: The destination Layer 2 ID for the 5G ProSe Inter-UE Relay Discovery Notification message is selected based on the configuration as described in clause 5.1.5.1.

[0068] -User Information ID of 5G ProSe Inter-UE Relay: Provides information about 5G ProSe Inter-UE Relay.

[0069] -User information ID list of 5G ProSe UE: provides information about 5G ProSe UE.

[0070] -Relay Service Code: Information used to indicate the connectivity service provided by the 5G ProSe inter-UE relay for the 5G ProSe end UE.

[0071] The following parameters are used for the 5G ProSe inter-UE relay discovery solicitation message (Model B) between the discoverer 5G ProSe end UE and the 5G ProSe inter-UE relay, where the source layer 2 ID and the destination layer 2 ID are used to send and receive the message, and the user information ID and relay service code are included in the message:

[0072] -Source Layer 2 ID: The discoverer 5G ProSe UE selects the source layer 2 ID for relaying discovery request messages between 5G ProSe UEs.

[0073] - Destination Layer 2 ID: The destination Layer 2 ID for the 5G ProSe Inter-UE Relay Discovery Solicitation message is selected based on the configuration as described in clause 5.1.5.1.

[0074] -User information ID of the discoverer 5G ProSe UE: provides information about the discoverer 5G ProSe UE.

[0075] -User information ID of the discovered 5G ProSe UE: provides information about the discovered 5G ProSe UE.

[0076] -Relay Service Code: Information about the connectivity services that the discoverer 5G ProSe-side UE is interested in.

[0077] The following parameters are used for the 5G ProSe inter-UE relay discovery response message (Model B) between the discoverer 5G ProSe end UE and the 5G ProSe inter-UE relay, where the source layer 2 ID and the destination layer 2 ID are used to send and receive the message, and the user information ID and relay service code are included in the message:

[0078] - Source Layer 2 ID: The 5G ProSe Inter-UE Relay selects the Source Layer 2 ID for the 5G ProSe Inter-UE Relay Discovery Response message by itself.

[0079] - Destination Layer 2 ID: set to the source Layer 2 ID of the received 5G ProSe Inter-UE Relay Discovery Request message.

[0080] -User information ID of the discovered 5G ProSe UE: provides information about the discovered 5G ProSe UE.

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

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

[0083] The following parameters are used for the 5G ProSe Inter-UE Relay Discovery Solicitation message (Model B) between the 5G ProSe Inter-UE Relay and the discoverer 5G ProSe end UE, where the source layer 2 ID and the destination layer 2 ID are used to send and receive the message, and the user information ID and relay service code are included in the message:

[0084] - Source Layer 2 ID: The 5G ProSe Inter-UE Relay selects the Source Layer 2 ID for the 5G ProSe Inter-UE Relay Discovery Request message itself.

[0085] - Destination Layer 2 ID: The destination Layer 2 ID for the 5G ProSe Inter-UE Relay Discovery Solicitation message is selected based on the configuration as described in clause 5.1.5.1.

[0086] -User information ID of the discoverer 5G ProSe UE: provides information about the discoverer 5G ProSe UE.

[0087] -User information ID of the discovered 5G ProSe UE: provides information about the discovered 5G ProSe UE.

[0088] -User Information ID of 5G ProSe Inter-UE Relay: Provides information about 5G ProSe Inter-UE Relay.

[0089] -Relay Service Code: identifies the connectivity service provided by the 5G ProSe inter-UE relay to the 5G ProSe end UE.

[0090] The following parameters are used for the 5G ProSe Inter-UE Relay Discovery Response message (Model B) between the 5G ProSe Inter-UE Relay and the discoverer 5G ProSe end UE, where the source layer 2 ID and the destination layer 2 ID are used to send and receive the message, and the user information ID and relay service code are included in the message:

[0091] -Source Layer 2 ID: The discoverer 5G ProSe UE selects the source layer 2 ID for the 5G ProSe inter-UE relay discovery response message.

[0092] - Destination Layer 2 ID: set to the source Layer 2 ID of the received 5G ProSe Inter-UE Relay Discovery Request message.

[0093] -User information ID of the discovered 5G ProSe UE: provides information about the discovered 5G ProSe UE.

[0094] -User information ID of the discoverer 5G ProSe UE: provides information about the discoverer 5G ProSe UE.

[0095] -Relay Service Code: identifies the connectivity service provided by the 5G ProSe inter-UE relay to the 5G ProSe end UE, which matches the relay service code from the corresponding discovery request message.

[0096] NOTE: UE implementations need to ensure that when the UE selects a source Layer 2 ID itself, the self-selected source Layer 2 ID is different between 5G ProSe direct discovery (including 5G ProSe UE to network relay discovery and 5G ProSe inter-UE relay discovery) in clause 6.3.2 and 5G ProSe direct communication (including 5G ProSe UE to network relay communication and 5G ProSe inter-UE relay communication) in clauses 6.4, 6.5 and 6.7, and is different from any other supplied destination Layer 2 ID described in clause 5.1 and any other self-selected source Layer 2 ID used for simultaneous 5G ProSe direct discovery (including 5G ProSe UE to network relay discovery and 5G ProSe inter-UE relay discovery) with different discovery models.

[0097] 5.8.5 Identifier for 5G ProSe Inter-UE Relay Communication Integrated with Discovery

[0098] For the broadcast direct communication request message on the first-hop PC5 reference point, the source Layer 2 ID is selected by the source 5G ProSe end UE itself, and the destination Layer 2 ID is selected based on the configuration described in clause 5.1.

[0099] For the Broadcast Direct Communication Request message over the second-hop PC5 reference point, the source Layer 2 ID is selected by the 5G ProSe Inter-UE Relay itself and the destination Layer 2 ID is selected based on the configuration described in clause 5.1.

[0100] The 5G ProSe inter-UE relay may send a unicast direct communication request message to the target 5G ProSe end UE by setting the destination layer 2 ID with the received unicast destination layer 2 ID of the target 5G ProSe end UE specified in clause 6.4.3.7. The source layer 2 ID is selected by the 5G ProSe inter-UE relay itself.

[0101] For unicast direct communication accept messages, the source layer 2 ID is selected by the target 5G ProSe UE or the 5G ProSe UE-to-UE relay itself.

[0102] […]

[0103] 6.3.2.4 5G ProSe Inter-UE Relay Discovery

[0104] 6.3.2.4.1 General

[0105] 5G ProSe inter-UE relay discovery is suitable for both 5G ProSe layer 3 and layer 2 inter-UE relay discovery for public safety purposes and commercial services. In order to perform 5G ProSe inter-UE relay discovery, the 5G ProSe-side UE and the 5G ProSe inter-UE relay are pre-configured or provisioned with the relevant information described in clause 5.1.

[0106] A Relay Service Code (RSC) is used for 5G ProSe inter-UE relay discovery to indicate the connectivity service provided by the 5G ProSe inter-UE relay to the 5G ProSe end UE. The RSC is pre-configured or provisioned on the 5G ProSe inter-UE relay and the 5G ProSe end UE as defined in clause 5.1. The 5G ProSe inter-UE relay and the 5G ProSe end UE know whether the RSC is providing 5G ProSe layer 2 or layer 3 inter-UE relay service based on the policy as specified in clause 5.1. A 5G ProSe inter-UE relay supporting multiple RSCs may advertise the RSCs using multiple discovery messages with one RSC per discovery message.

[0107] 6.3.2.4.2 Procedure for 5G ProSe Inter-UE Relay Discovery using Model A

[0108] Figure 6 .3.2.4.2-1 describes the procedure for 5G ProSe inter-UE discovery using Model A.

[0109] [3GPP TS 23.304 V18.2.0 entitled "5G ProSe Inter-UE Relay Discovery using Model A" Figure 6 .3.2.4.2-1 is reproduced as Figure 6 ]

[0110] 1. The 5G ProSe inter-UE relay has discovered other UEs in the vicinity (eg, via a previous 5G ProSe inter-UE relay discovery or 5G ProSe inter-UE relay communication procedure). The 5G ProSe inter-UE relay obtains the user information IDs of other UEs in the vicinity for each RSC.

[0111] 2.5G ProSe Inter-UE Relay sends Inter-UE Relay Discovery Notification message. The Inter-UE Relay Discovery Notification message contains the type of discovery message, the user information ID of the 5G ProSe Inter-UE Relay, the RSC and the user information ID list of the 5G ProSe end UE, and is sent using the source layer 2 ID and the destination layer 2 ID, as described in clause 5.8.4.

[0112] 5G ProSe inter-UE relay will only inform the user information IDs of other UEs in the vicinity that provided relay_indication when previously discovered.

[0113] The 5G ProSe UE listens to the notification message from the 5G ProSe inter-UE relay. The 5G ProSe UE determines the destination layer 2 ID for signaling reception as specified in clause 5.1.

[0114] 6.3.2.4.3 Procedure for 5G ProSe Inter-UE Relay Discovery using Model B

[0115] Figure 6 The procedure for 5G ProSe inter-UE relay discovery using Model B is described in .3.2.4.3-1.

[0116] [3GPP TS 23.304 V18.2.0 entitled "5G ProSe Inter-UE Relay Discovery using Model B" Figure 6 .3.2.4.3-1 is reproduced as Figure 7 ]

[0117] 1. The discoverer 5G ProSe UE (UE-1) sends a 5G ProSe inter-UE relay discovery request message. The 5G ProSe inter-UE relay discovery request message contains the type of discovery message, its own user information ID, RSC and the user information ID of the discoverer 5G ProSe UE (UE-2), and is sent using the source layer 2 ID and the destination layer 2 ID, as described in clause 5.8.4.

[0118] The 5G ProSe inter-UE relay determines the destination Layer 2 ID for signaling reception as specified in clause 5.1.

[0119] 2. The 5G ProSe inter-UE relay matching the RSC sends a 5G ProSe inter-UE relay discovery solicitation message. The 5G ProSe inter-UE relay discovery solicitation message contains the type of discovery message, the user information ID of the discoverer 5G ProSe end UE (UE-1), the user information ID of the inter-UE relay, the RSC and the user information ID of the discoverer 5G ProSe end UE (UE-2), and is sent using the source layer 2 ID and the destination layer 2 ID, as described in clause 5.8.4.

[0120] The 5G ProSe-side UE determines the destination Layer 2 ID for signaling reception as specified in clause 5.1.

[0121] 3. The discoverer 5G ProSe end UE (UE2) matching the value of RSC and the user information ID of the discoverer 5G ProSe end UE (UE2) responds to the 5G ProSe inter-UE relay with a 5G ProSe inter-UE relay discovery response message. The 5G ProSe inter-UE relay discovery response message contains the type of discovery message, RSC, the user information ID of the discoverer 5G ProSe end UE (UE-1) and its own user information ID, and is sent using the source layer 2 ID and the destination layer 2 ID, as described in clause 5.8.4. If the discoverer 5G ProSe end UE (UE-2) receives multiple inter-UE relay discovery solicitation messages from different 5G ProSe inter-UE relays, it may choose to respond or not to the 5G ProSe inter-UE relay (e.g., based on the PC5 signal strength of each message received).

[0122] 4.5G ProSe Inter-UE Relay sends a 5G ProSe Inter-UE Relay Discovery Response message. The 5G ProSe Inter-UE Relay Discovery Response message contains the type of discovery message, the user information ID of the Inter-UE Relay, the RSC and the user information ID of the discovered 5G ProSe end UE (UE-2), and is sent using the source layer 2 ID and the destination layer 2 ID, as described in clause 5.8.4.

[0123] 6.3.2.4.4 Candidate 5G ProSe Inter-UE Relay Discovery

[0124] This procedure for candidate 5G ProSe inter-UE relay discovery supports negotiated relay reselection when the discoverer-side UE discovers a candidate 5G ProSe inter-UE relay, as described in clause 6.7.4.

[0125] The procedure for 5G ProSe inter-UE relay discovery with Model B is used (see clause 6.3.2.4.3), with the following differences:

[0126] - Step 1: In the 5G ProSe Inter-UE Relay Discovery Solicitation message, no RSC is included, and the User Information ID of the discoverer 5G ProSe end UE is replaced with the User Information ID of the candidate 5G ProSe Inter-UE Relay. If the 5G ProSe end UE receives the Layer 2 ID of the candidate 5G ProSe Inter-UE Relay in the Link Modification Request message, then it can set the Layer 2 ID of the candidate 5G ProSe Inter-UE Relay to the destination Layer 2 ID.

[0127] - Step 2 and step 3 are skipped because RSC is not present in the received 5G ProSe Inter-UE Relay Discovery Solicitation message.

[0128] - Step 4: If the 5G ProSe inter-UE relay matches the user information ID of the candidate 5G ProSe inter-UE relay received in the 5G ProSe inter-UE relay discovery request, it sends a 5G ProSe inter-UE relay discovery response and does not include the user information ID of the discovered 5G ProSe end UE.

[0129] […]

[0130] 6.4.3 Unicast Mode 5G ProSe Direct Communication

[0131] 6.4.3.1 Layer 2 link establishment over PC5 reference point

[0132] To perform unicast mode of ProSe direct communication over PC5 reference point, the UE is configured with relevant information as described in clause 5.1.3.

[0133] Figure 6 .4.3.1-1 shows the Layer 2 link establishment procedure for unicast mode ProSe direct communication over PC5 reference point.

[0134] [3GPP TS23.304 V18.2.0 is titled "Layer 2 Link Establishment Procedure" Figure 6 .4.3.1-1 is reproduced as Figure 8 ]

[0135] 1. The UE determines the destination Layer 2 ID for signalling reception for PC5 unicast link establishment as specified in clause 5.8.2.4.

[0136] 2. The ProSe application layer in UE-1 provides application information for PC5 unicast communication. The application information includes ProSe service information and the application layer ID of the UE. The application information may include the application layer ID of the target UE.

[0137] The ProSe application layer in UE-1 may provide the ProSe application requirements for this unicast communication.UE-1 determines the PC5 QoS parameters and PFI as specified in clause 5.6.1.

[0138] If UE-1 decides to reuse the existing PC5 unicast link as specified in clause 5.3.4, the UE triggers the Layer 2 Link Modification procedure as specified in clause 6.4.3.4.

[0139] 3. UE-1 sends a direct communication request message to initiate the unicast layer 2 link establishment procedure. The direct communication request message contains:

[0140] - Source user information: the application layer ID of the originating UE (ie, the application layer ID of UE-1).

[0141] - If the ProSe application layer provides the application layer ID of the target UE in step 2, the following information is included:

[0142] - Target user information: Application layer ID of the target UE (ie, the application layer ID of UE-2).

[0143] -ProSe service information: Information about the ProSe identifier requesting Layer 2 link establishment.

[0144] - Security information: information used to establish security.

[0145] NOTE 1: Security information and the necessary protection of source user information and destination user information are defined in TS 33.503

[29] .

[0146] As specified in clauses 5.8.2.1 and 5.8.2.4, the source layer 2ID and destination layer 2ID used to send the direct communication request message are determined. The destination layer 2ID can be a broadcast or unicast layer 2ID. When a unicast layer 2ID is used, the target user information shall be included in the direct communication request message.

[0147] UE-1 sends a direct communication request message via PC5 by broadcast or unicast using the source layer 2ID and the destination layer 2ID.

[0148] The default PC5 DRX configuration may be used for transmission and reception of this message (see TS 38.300

[12] ).

[0149] 4. Establish security for UE-1 as follows:

[0150] 4a. If the target user information is included in the direct communication request message, the target UE (ie, UE-2) responds by establishing security with UE-1.

[0151] 4b. If the target user information is not included in the direct communication request message, the UE interested in using the announced ProSe service over the PC5 unicast link with UE-1 responds by establishing security with UE-1.

[0152] NOTE 2: Signalling for security procedures is defined in TS 33.503

[29] .

[0153] When security protection is enabled, UE-1 sends the following information to the target UE:

[0154] - If using IP communication, then:

[0155] -IP Address Configuration: For IP communication, this link requires IP address configuration, and it indicates one of the following values:

[0156] - "DHCPv4 server", if only IPv4 address allocation mechanism is supported by the initiating UE, i.e. acting as a DHCPv4 server; or

[0157] - "IPv6 router", if the initiating UE only supports IPv6 address allocation mechanisms, i.e. acts as an IPv6 router; or

[0158] - "DHCPv4 server and IPv6 router", if both IPv4 and IPv6 address allocation mechanisms are supported by the initiating UE; or

[0159] - "Address allocation not supported", if neither IPv4 nor IPv6 address allocation mechanisms are supported by the initiating UE.

[0160] - Link-local IPv6 address: If UE-1 does not support the IPv6 IP address allocation mechanism, i.e. the IP address configuration indicates "address allocation not supported", then a link-local IPv6 address is formed locally based on RFC 4862

[17] .

[0161] - QoS Information: Information about one or more PC5 QoS flows. For each PC5 QoS flow, the PFI and corresponding PC5 QoS parameters (ie, PQI and conditionally other parameters such as MFBR / GFBR) and the associated ProSe identifier.

[0162] -Optional PC5 QoS rules.

[0163] The source Layer 2 ID for the security establishment procedure is determined as specified in clauses 5.8.2.1 and 5.8.2.4. The destination Layer 2 ID is set to the source Layer 2 ID of the received direct communication request message.

[0164] Upon receiving the Security Setup Procedure message, UE-1 obtains the Layer 2 ID of the peer UE for future communications for signaling and data traffic for this unicast link.

[0165] 5. One or more target UEs that have successfully established security with UE-1 send a direct communication acceptance message to UE-1:

[0166] 5a. (Layer 2 link establishment towards UE) If the target user information is contained in the direct communication request message, then if the application layer ID for UE-2 matches, the target UE (ie, UE-2) responds with a direct communication accept message.

[0167] 5b. (Layer 2 Link Establishment for ProSe Services) If the direct communication request message does not contain target user information, the UE interested in using the notified ProSe service (in Figure 6 .UE-2 and UE-4 in 4.3.1-1) respond to the request by sending a direct communication accept message.

[0168] The direct communication acceptance message contains:

[0169] -Source user information: the application layer ID of the UE that sends the direct communication acceptance message.

[0170] - QoS Information: Information about one or more PC5 QoS flows. For each PC5 QoS flow, the PFI requested by UE-1 and the corresponding PC5 QoS parameters (ie PQI and conditionally other parameters such as MFBR / GFBR) and optionally the associated ProSe identifier.

[0171] -Optional PC5 QoS rules.

[0172] - If using IP communication, then:

[0173] -IP Address Configuration: For IP communication, this link requires IP address configuration, and it indicates one of the following values:

[0174] - "DHCPv4 Server", if only IPv4 address allocation mechanism is supported by the target UE, i.e. act as a DHCPv4 server; or

[0175] - "IPv6 router", if the target UE only supports IPv6 address allocation mechanisms, i.e. acts as an IPv6 router; or

[0176] - "DHCPv4 server and IPv6 router", if both IPv4 and IPv6 address allocation mechanisms are supported by the target UE; or

[0177] - "Address allocation not supported" if neither IPv4 nor IPv6 address allocation mechanisms are supported by the target UE.

[0178] - Link-local IPv6 address: A link-local IPv6 address formed locally based on RFC 4862

[17] . If the target UE does not support the IPv6 IP address allocation mechanism, i.e., the IP address configuration indicates "address allocation is not supported", and UE-1 includes a link-local IPv6 address in the Direct Communication Request message, the target UE shall include a non-conflicting link-local IPv6 address.

[0179] If two UEs (ie, an initiating UE and a target UE) are selected to use link-local IPv6 addresses, then the two UEs shall disable dual address detection as defined in RFC 4862

[17] .

[0180] NOTE 3: When the initiating UE or the target UE indicates support for IPv6 routers, the corresponding address configuration procedure shall be implemented after the layer 2 link is established and the link-local IPv6 address shall be ignored.

[0181] The ProSe layer of the UE that establishes the PC5 unicast link passes the PC5 link identifier assigned for the unicast link and the PC5 unicast link related information downward to the AS layer. The information related to the PC5 unicast link 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 the PC5 unicast link related information.

[0182] The two UEs may negotiate the PC5 DRX configuration in the AS layer, and PC5 DRX parameter values ​​may be configured for each pair of source and destination Layer 2 IDs in the AS layer.

[0183] 6. ProSe data is transmitted over the established unicast link as follows:

[0184] The PC5 link identifier and PFI are provided to the AS layer together with the ProSe data.

[0185] Additionally, layer 2 ID information (ie, source layer 2 ID and destination layer 2 ID) is optionally provided to the AS layer.

[0186] NOTE 4: It is up to the UE implementation to provide the Layer 2 ID information to the AS layer.

[0187] UE-1 sends ProSe data using a source Layer 2 ID (ie, the Layer 2 ID of UE-1 for this unicast link) and a destination Layer 2 ID (ie, the Layer 2 ID of the peer UE for this unicast link).

[0188] NOTE 5: The PC5 unicast link is bidirectional, so UE-1's peer UE can send ProSe data to UE-1 through the unicast link with UE-1.

[0189] […]

[0190] 6.4.3.4 Layer 2 Link Modification for Unicast Links

[0191] Figure 6 .4.3.4-1 shows the Layer 2 Link Modification procedure for unicast links. This procedure is used to:

[0192] -Add new PC5 QoS flow in existing PC5 unicast link.

[0193] - This covers the case for adding a new PC5 QoS flow to an existing ProSe service as well as the case for adding a new PC5 QoS flow to a new ProSe service.

[0194] - Modify an existing PC5 QoS flow in an existing PC5 unicast link.

[0195] - This covers the case of modifying PC5 QoS parameters for an existing PC5 QoS flow.

[0196] - This also covers the case where an associated ProSe service is removed from an existing PC5 QoS flow and the case where a new ProSe service is associated with an existing PC5 QoS flow.

[0197] - Remove one or more existing PC5 QoS flows in an existing PC5 unicast link.

[0198] [3GPP TS 23.304 V18.2.0 entitled "Layer 2 Link Modification Procedure" Figure 6 .4.3.4-1 is reproduced as Fig. 9 ]

[0199] 0. UE-1 and UE-2 have a unicast link established as described in clause 6.4.3.1.

[0200] 1. The ProSe application layer in UE-1 provides application information for PC5 unicast communication. The application information contains 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 the existing PC5 unicast link as specified in clause 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.

[0201] The link modification request message contains:

[0202] a) To add a new PC5 QoS flow in an existing PC5 unicast link:

[0203] - QoS Information: Information about the PC5 QoS flows to be added. For each PC5 QoS flow, PFI, corresponding PC5 QoS parameters (ie PQI and conditionally other parameters such as MFBR / GFBR) and optionally associated ProSe identifier.

[0204] -Optional PC5 QoS rules.

[0205] b) To modify a PC5 QoS flow in an existing PC5 unicast link:

[0206] - QoS Information: Information about the PC5 QoS flows to be modified. For each PC5 QoS flow, the PFI, the corresponding PC5 QoS parameters (ie PQI and conditionally other parameters such as MFBR / GFBR) and optionally the associated ProSe identifier.

[0207] -Optional PC5 QoS rules.

[0208] c) To remove the PC5 QoS flow from an existing PC5 unicast link:

[0209] -PFI.

[0210] 2. UE-2 responds with a Link Modification Accept message.

[0211] The link modification acceptance message contains:

[0212] - For case a) and case b) described in step 1:

[0213] - QoS Information: Information about PC5 QoS flows requested by UE- 1. For each PC5 QoS flow, PFI, corresponding PC5 QoS parameters (ie PQI and conditionally other parameters such as MFBR / GFBR) and optionally associated ProSe identifier.

[0214] -Optional PC5 QoS rules.

[0215] The ProSe layer of each UE provides information about the unicast link modification to the AS layer, which enables the AS layer to update the context related to the modified unicast link.

[0216] […]

[0217] 6.4.3.7 Layer 2 Link Management over PC5 Reference Point for 5G ProSe Inter-UE Relay

[0218] 6.4.3.7.1 Common part of Layer 2 link management over PC5 reference point for 5G ProSe inter-UE relay

[0219] For 5G ProSe communication via 5G ProSe inter-UE relay as described in clauses 6.7.1 and 6.7.2:

[0220] -The direct communication request message on the first hop PC5 reference point contains:

[0221] -User information ID of the source 5G ProSe UE: the identity of the source 5G ProSe UE requesting the relay operation (i.e., the user information ID).

[0222] - User Information ID of 5G ProSe Inter-UE Relay: The identity of the Inter-UE Relay (i.e., User Information ID) provided to the source 5G ProSe end UE during the 5G ProSe Inter-UE Relay discovery procedure.

[0223] - User Information ID of target 5G ProSe UE: The identity of the target 5G ProSe UE (i.e., User Information ID) provided to the source 5G ProSe UE during the inter-UE relay discovery procedure.

[0224] - (Optional) Destination Layer 2 ID of target 5G ProSe end UE: The unicast destination Layer 2 ID of the target 5G ProSe end UE determined by the source 5G ProSe end UE, as specified in clause 5.8.2.4.

[0225] -ProSe service information: Information about the ProSe identifier requesting Layer 2 link establishment.

[0226] -RSC: Connectivity service requested by the source 5G ProSe UE and provided by the 5G ProSe inter-UE relay.

[0227] - Security information: information used to establish security for first-hop PC5 link establishment.

[0228] NOTE 1 Security information is defined by SA WG3.

[0229] The direct communication request message on the second hop PC5 reference point contains:

[0230] -User information ID of the source 5G ProSe UE.

[0231] -User information ID of the target 5G ProSe UE.

[0232] -User information ID relayed between 5G ProSe UEs.

[0233] -ProSe service information: information about the ProSe identifier.

[0234] -RSC: Connectivity service requested by the source 5G ProSe UE and provided by the 5G ProSe inter-UE relay.

[0235] - Security information: information used to establish security for the second hop PC5 link establishment.

[0236] NOTE 2 Security information is defined by SA WG3.

[0237] The direct communication acceptance message on the second hop PC5 reference point contains:

[0238] -User information ID of the target 5G ProSe UE.

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

[0240] -User information ID of the target 5G ProSe UE.

[0241] -User information ID relayed between 5G ProSe UEs.

[0242] The link modification request message on the first hop PC5 reference point contains:

[0243] - User Information ID of target 5G ProSe UE: The identity of the target 5G ProSe UE provided to the source 5G ProSe UE during the inter-UE relay discovery procedure.

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

[0245] The link modification request message on the second hop PC5 reference point contains:

[0246] -User information ID of the source 5G ProSe UE.

[0247] -User information ID of the target 5G ProSe UE.

[0248] The link modification acceptance message on the second hop PC5 reference point contains:

[0249] -User information ID of the target 5G ProSe UE.

[0250] The link modification acceptance message on the first hop PC5 reference point contains:

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

[0252] 6.4.3.7.2 Layer 2 Link Management over PC5 Reference Point for 5G ProSe Layer 2 Inter-UE Relay

[0253] For 5G ProSe communication via 5G ProSe layer 2 inter-UE relay as described in clause 6.7.2, the description in clause 6.4.3.7.1 applies.

[0254] The message contents over the PC5 reference point for unicast mode 5G ProSe direct communication described in clauses 6.4.3.1 to 6.4.3.5 are the same for end-to-end connections between peer 5G ProSe end UEs.

[0255] Editor's note: Whether LIU between peer-to-peer UEs has the same message content as direct PC5 LIU messages is for further study.

[0256] 6.4.3.7.3 Layer 2 Link Management over PC5 Reference Point for 5G ProSe Layer 3 Inter-UE Relay

[0257] For 5G ProSe communication via 5G ProSe layer 3 inter-UE relay as described in clause 6.7.1, the description in clause 6.4.3.7.1 applies with the following differences and clarifications:

[0258] - In the security procedure of the first-hop PC5 reference point, the source 5G ProSe layer 3 end UE provides the 5G ProSe layer 3 inter-UE relay with IP address configuration or link-local IPv6 address and QoS information of end-to-end QoS. If the PC5 link is used to transmit Ethernet services, the source 5G ProSe layer 3 end UE provides its Ethernet MAC address instead of IP related information.

[0259] - In the security procedure of the second-hop PC5 reference point, the 5G ProSe layer 3 inter-UE relay provides the target 5G ProSe end UE with IP address configuration or link-local IPv6 address and QoS information of the second-hop QoS. If the PC5 link is used to transmit Ethernet services, the 5G ProSe layer 3 inter-UE relay provides the Ethernet MAC address of the source 5G ProSe layer 3 end UE instead of IP related information.

[0260] -The direct communication accept message on the second hop PC5 reference point additionally contains the 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 end UE provides its Ethernet MAC address instead of IP related information.

[0261] - The 5G ProSe layer 3 inter-UE relay determines the QoS information of the first-hop QoS by considering the received second-hop QoS. The direct communication accept message on the first-hop PC5 reference point additionally contains the IP address configuration or link-local IPv6 address, the QoS information of the first-hop QoS and may contain the IP address of the target 5G ProSe end UE. If the PC5 link is used to transmit Ethernet services, the 5G ProSe layer 3 inter-UE relay provides the Ethernet MAC address of the target 5G ProSe layer 3 end UE instead of IP related information.

[0262] - In the Link Modification Request message on the first hop PC5 reference point, the source 5G ProSe UE additionally includes QoS information for end-to-end QoS. If the PC5 link is used to deliver Ethernet services, the source 5G ProSe layer 3 UE may provide its Ethernet MAC address.

[0263] - In the Link Modification Request message over the second-hop PC5 reference point, the 5G ProSe layer 3 inter-UE relay additionally includes the QoS information of the second-hop QoS to the target 5G ProSe end UE. If the PC5 link is used to deliver Ethernet services, the 5G ProSe layer 3 inter-UE relay provides the Ethernet MAC address of the source 5G ProSe layer 3 end UE.

[0264] -The Link Modification Accept message on the second hop PC5 reference point additionally contains QoS information for the second hop QoS. If the PC5 link is used to deliver Ethernet services, the target 5G ProSe layer 3 end UE may provide its Ethernet MAC address.

[0265] - Taking into account the received second-hop QoS, the 5G ProSe layer 3 inter-UE relay determines the QoS information of the first-hop QoS, and the link modification accept message on the first-hop PC5 reference point additionally contains the QoS information of the first-hop QoS and may contain the IP address of the target 5G ProSe end UE. If the PC5 link is used to deliver Ethernet services, the 5G ProSe layer 3 inter-UE relay provides the Ethernet MAC address of the target 5G ProSe layer 3 end UE instead of IP related information.

[0266] When the PC5 link between the 5G ProSe layer 3 end UE and the 5G ProSe layer 3 inter-UE relay is released, the 5G ProSe layer 3 inter-UE relay can initiate the release of the PC5 link to the peer 5G ProSe layer 3 end UE, or notify the peer 5G ProSe layer 3 end UE that the peer PC5 link is released.

[0267] 6.4.3.7.4 Layer 2 Link Management over PC5 Reference Point for 5G ProSe Inter-UE Relay Communication with Integrated Discovery

[0268] This clause is for 5G ProSe inter-UE relay communication integrated with discovery procedures as described in clause 6.7.3.

[0269] The direct communication request message on the first hop PC5 reference point contains:

[0270] -User information ID of the source 5G ProSe UE.

[0271] - (Optional) User Information ID of target 5G ProSe UE: the identity of the target 5G ProSe UE (if provided from the ProSe application layer).

[0272] - (Optional) Destination Layer 2 ID of target 5G ProSe end UE: The unicast destination Layer 2 ID of the target 5G ProSe end UE determined by the source 5G ProSe end UE, as specified in clause 5.8.2.4.

[0273] -ProSe service information: Information about the ProSe identifier requesting Layer 2 link establishment.

[0274] -RSC: Connectivity service requested by the source 5G ProSe UE and provided by the 5G ProSe inter-UE relay.

[0275] -Relay_indication: indicates whether the direct communication request message can be forwarded by the 5G ProSe inter-UE relay.

[0276] - Security information: information used to establish security for first-hop PC5 link establishment.

[0277] NOTE 1 Security information is defined by SA WG3.

[0278] The direct communication request message on the second hop PC5 reference point contains:

[0279] -User information ID of the source 5G ProSe UE.

[0280] -User information ID relayed between 5G ProSe UEs.

[0281] -(Optional) User information ID of the target 5G ProSe UE.

[0282] -ProSe service information: information about the ProSe identifier.

[0283] -RSC: Connectivity service requested by the source 5G ProSe UE and provided by the 5G ProSe inter-UE relay.

[0284] - Security information: information used to establish security for the second hop PC5 link establishment.

[0285] NOTE 2 Security information is defined by SA WG3.

[0286] The direct communication acceptance message on the second hop PC5 reference point contains:

[0287] -User information ID of the target 5G ProSe UE.

[0288] The direct communication acceptance message on the first hop PC5 reference point contains:

[0289] -User information ID of the target 5G ProSe UE.

[0290] -User information ID relayed between 5G ProSe UEs.

[0291] For 5G ProSe communication via 5G ProSe layer 3 inter-UE relay, additional explanations are as follows:

[0292] -In the security procedure of the second-hop PC5 reference point, the 5G ProSe layer 3 inter-UE relay provides the IP address configuration or link-local IPv6 address to the target 5G ProSe end UE.

[0293] -The direct communication accept message on the second hop PC5 reference point additionally includes the IP address configuration or link-local IPv6 address (if IP communication is used), the Ethernet MAC address of the target 5G ProSe end UE (if Ethernet communication is used). QoS information is not included in the security procedures or direct communication accept message of the second hop PC5 reference point.

[0294] - In the security procedure of the first-hop PC5 reference point, the source 5G ProSe end UE provides the 5G ProSe layer 3 inter-UE relay with IP address configuration, link-local IPv6 address and QoS information of end-to-end QoS.

[0295] -5G ProSe Layer 3 Inter-UE Relay provides QoS information of the second-hop QoS to the target 5G ProSe end UE using Layer 2 Link Modification as described in clause 6.4.3.4.

[0296] - Considering that the second-hop QoS is received from the target 5G ProSe end UE, the 5G ProSe layer 3 inter-UE relay determines the QoS information of the first-hop QoS, and the direct communication accept message on the first-hop PC5 reference point additionally includes the IP address configuration or link-local IPv6 address, the QoS information of the first-hop QoS, and may include the IP address of the target 5G ProSe end UE (if IP communication is used) or the Ethernet MAC address of the target 5G ProSe end UE (if Ethernet communication is used).

[0297] For 5G ProSe communication via 5G ProSe layer 2 inter-UE relay, the message contents over the PC5 reference point for unicast mode 5G ProSe direct communication described in clauses 6.4.3.1 to 6.4.3.5 are the same for end-to-end connections between peer 5G ProSe end UEs.

[0298] […]

[0299] 6.7 5G ProSe UE-to-UE Relay Communication

[0300] 6.7.1 5G ProSe Communication via 5G ProSe Layer 3 Inter-UE Relay

[0301] 6.7.1.1 Layer 2 Link Establishment for PC5 Communication via 5G ProSe Layer 3 Inter-UE Relay

[0302] Figure 6 .7.1.1-1 shows the procedure for Layer 2 link establishment via 5G ProSe Layer 3 inter-UE relay.

[0303] [3GPP TS 23.304 V18.2.0 entitled "Layer 2 link establishment via 5G ProSe Layer 3 inter-UE relay" Figure 6 .7.1.1-1 is reproduced as Fig.10 ]

[0304] 1. Perform service authorization and provisioning for the source 5G ProSe Layer 3-end UE, the target 5G ProSe Layer 3-end UE and the 5G ProSe Layer 3 inter-UE relay as described in clause 6.2.

[0305] 2. The source 5G ProSe layer 3 end UE performs discovery of 5G ProSe layer 3 inter-UE relays as described in clause 6.3.2.4.

[0306] 3. The source 5G ProSe layer 3 end UE sends a direct communication request message to initiate the unicast layer 2 link establishment procedure with the 5G ProSe layer 3 inter-UE relay. The parameters included in the direct communication request message are described in clause 6.4.3.7.

[0307] The source layer 2 ID of the direct communication request message is assigned by the source 5G ProSe layer 3 end UE, and the destination layer 2 ID is set to the source layer 2 ID of the discovery message relayed between 5G ProSe layer 3 UEs.

[0308] 4. If the User Information ID of the 5G ProSe layer 3 inter-UE relay in the direct communication request message matches the User Information ID of the 5G ProSe layer 3 inter-UE relay, and the RSC in the direct communication request matches one of the RSCs supported by the relay, then the 5G ProSe layer 3 inter-UE relay responds by establishing security with the source 5G ProSe layer 3 end UE. When security protection is enabled, the source 5G ProSe layer 3 end UE sends the parameters as described in clause 6.4.3.7 to the 5G ProSe layer 3 inter-UE relay.

[0309] If the Ethernet MAC address of the source 5G ProSe layer 3 end UE is already used by another 5G ProSe layer 3 end UE, the 5G ProSe layer 3 inter-UE relay may send a message to the source 5G ProSe layer 3 end UE indicating that there is an Ethernet MAC address conflict.

[0310] The source Layer 2 ID used for the security establishment procedure is self-assigned by the 5G ProSe Layer 3 inter-UE relay, and the destination Layer 2 ID is set to the source Layer 2 ID of the received direct communication request message.

[0311] The 5G ProSe layer 3 inter-UE relay will select different source layer 2 IDs for the PC5 links of different types of services, i.e., IP services, Ethernet services and unstructured services.

[0312] If the PC5 link is used to deliver unstructured services, the 5G ProSe layer 3 inter-UE relay will select different source layer 2 IDs for different pairs of source and target 5G ProSe layer 3 end UEs.

[0313] After receiving the security establishment procedure message, the source 5G ProSe layer 3 end UE obtains the layer 2 ID of the 5G ProSe layer 3 inter-UE relay for future communications, thereby being used for signaling and data services of this unicast link.

[0314] 5. After the security establishment procedure in step 4 is completed, the 5G ProSe layer 3 inter-UE relay sends a direct communication request message to initiate a unicast layer 2 link establishment procedure with the target 5G ProSe layer 3 end UE. The parameters included in the direct communication request message are described in clause 6.4.3.7.

[0315] The source layer 2 ID of the direct communication request message is assigned by the 5G ProSe layer 3 inter-UE relay, and the destination layer 2 ID is the unicast layer 2 ID of the target 5G ProSe layer 3 end UE associated with the user information ID of the target 5G ProSe layer 3 end UE.

[0316] The 5G ProSe layer 3 inter-UE relay will select different source layer 2 IDs for the PC5 links of different types of services, i.e., IP services, Ethernet services and unstructured services.

[0317] If the PC5 link is used to deliver unstructured services, the 5G ProSe layer 3 inter-UE relay will select different source layer 2 IDs for different pairs of source and target 5G ProSe layer 3 end UEs.

[0318] 6. If the user information ID of the target 5G ProSe layer 3 end UE and the RSC contained in the direct communication request match the user information ID of the target UE and the RSC supported by the target UE, then the target 5G ProSe layer 3 end UE responds by establishing security with the 5G ProSe layer 3 inter-UE relay. When security protection is enabled, the 5G ProSe layer 3 inter-UE relay sends the parameters as described in clause 6.4.3.7 to the target 5G ProSe layer 3 end UE.

[0319] The source Layer 2 ID used for the security establishment procedure is self-assigned by the target 5G ProSe Layer 3 end UE, and the destination Layer 2 ID is set to the source Layer 2 ID of the received direct communication request message.

[0320] After receiving the security establishment procedure message, the 5G ProSe layer 3 inter-UE relay obtains the layer 2 ID of the target 5G ProSe layer 3 end UE for future communications, thereby being used for signaling and data services of this unicast link.

[0321] 7. The target 5G ProSe layer 3 end UE sends a direct communication accept message to the 5G ProSe layer 3 inter-UE relay for which security has been successfully established. The parameters included in the direct communication accept message are described in clause 6.4.3.7.

[0322] 8. For IP services, an IPv6 prefix or IPv4 address is allocated to the target 5G ProSe layer 3 end UE as defined in clause 5.5.1.4.

[0323] 9. After receiving the direct communication accept message from the target 5G ProSe layer 3 end UE, the 5G ProSe layer 3 inter-UE relay sends a direct communication accept message to the source 5G ProSe layer 3 end UE for which security has been successfully established. The parameters included in the direct communication accept message are described in clause 6.4.3.7.

[0324] 10. For IP services, an IPv6 prefix or IPv4 address is allocated to the source 5G ProSe layer 3 end UE as defined in clause 5.5.1.4.

[0325] 11. For IP communication, the 5G ProSe layer 3 inter-UE relay may store the association of the user information ID and the IP address of the target 5G ProSe layer 3 end UE into its DNS entry, and the 5G ProSe layer 3 inter-UE relay may act as a DNS server for other UEs. If the IP address of the target 5G ProSe layer 3 end UE is not received in step 9, then after step 10, the source 5G ProSe layer 3 end UE may send a DNS query to the 5G ProSe layer 3 inter-UE relay to request the IP address of the target 5G ProSe layer 3 end UE, and the 5G ProSe layer 3 inter-UE relay returns the IP address of the target 5G ProSe layer 3 end UE to the source 5G ProSe layer 3 end UE.

[0326] For Ethernet communications, the 5G ProSe Layer 3 inter-UE relay maintains the association between the PC5 link and the Ethernet MAC address received from the 5G ProSe Layer 3 end UE.

[0327] For unstructured traffic communications, for each pair of source and target 5G ProSe layer 3 end UEs, the 5G ProSe layer 3 inter-UE relay maintains a 1:1 mapping between the PC5 link with the source 5G ProSe layer 3 end UE and the PC5 link with the target 5G ProSe layer 3 end UE.

[0328] 12. The source 5G ProSe layer 3 end UE communicates with the target 5G ProSe layer 3 end UE via the 5G ProSe layer 3 inter-UE relay.

[0329] In the case where a source 5G ProSe layer 3 end UE communicates with multiple target 5G ProSe layer 3 end UEs, the PC5 link between the source 5G ProSe layer 3 end UE and the 5G ProSe layer 3 inter-UE relay can be shared by multiple target 5G ProSe layer 3 end UEs for each RSC, while a PC5 link can be established separately between the 5G ProSe layer 3 inter-UE relay and the target 5G ProSe layer 3 end UE for each RSC. For the shared PC5 link, the layer 2 link modification procedure will be used.

[0330] In the case where multiple source 5G ProSe layer 3 end UEs communicate with one target 5G ProSe layer 3 end UE, the PC5 link between the 5G ProSe layer 3 inter-UE relay and the target 5G ProSe layer 3 end UE can be shared for each RSC, while the PC5 link can be established separately between the source 5G ProSe layer 3 end UE and the 5G ProSe layer 3 inter-UE relay for each RSC. For the shared PC5 link, the layer 2 link modification procedure will be used.

[0331] […]

[0332] 6.7.1.4 Layer 2 Link Modification for PC5 Communication via 5G ProSe Layer 3 Inter-UE Relay

[0333] Figure 6 .7.1.4-1 shows the Layer 2 Link Modification procedure via Layer 3 Inter-UE Relay. This procedure is used to add / modify / remove PC5 QoS flows in an existing PC5 unicast link, as described in clause 6.4.3.7.3.

[0334] [3GPP TS 23.304 V18.2.0 entitled "Layer 2 Link Modification Procedure via Layer 3 Inter-UE Relay" Figure 6 .7.1.4-1 is reproduced as Fig.11 ]

[0335] 0. UE-1 and the inter-UE relay and the inter-UE relay and UE-2 establish unicast links as described in clause 6.7.1.1.

[0336] 1. UE-1 sends a Link Modification Request to the Inter-UE Relay as described in clause 6.4.3.7.3.

[0337] 2. After receiving the Link Modification Request message from UE-1, the Inter-UE Relay sends a Link Modification Request to UE-2 as described in clause 6.4.3.7.3.

[0338] 3. UE-2 responds to the Inter-UE Relay with a Link Modification Accept message as described in clause 6.4.3.7.3.

[0339] 4. After receiving the Link Modification Accept message from UE-2, the Inter-UE Relay responds to UE-1 with a Link Modification Accept message as described in clause 6.4.3.7.3.

[0340] […]

[0341] 6.7.3 5G ProSe Inter-UE Relay Communication with Integrated Discovery

[0342] 6.7.3.1 General

[0343] 5G ProSe communication via 5G ProSe inter-UE relay with integrated discovery is supported.

[0344] For 5G ProSe inter-UE relay communication integrated with discovery, when a UE allows direct communication requests to other UEs involving inter-UE relays, the UE indicates this by including relay_indication in the broadcast direct communication request message.

[0345] When the inter-UE relay receives a direct communication request containing relay_indication, it decides whether to forward the message based on, for example, the relay service code (if present), application ID, operator policy for each relay service code, signal strength, and local policy.

[0346] 6.7.3.2 Procedures for communication via layer 3 inter-UE relay

[0347] [3GPP TS 23.304 V18.2.0 entitled "5G ProSe inter-UE relay communication with integrated discovery via Layer 3 inter-UE relay" Figure 6 .7.3.2-1 is reproduced as Fig.12 ]

[0348] 0.5G ProSe end UE is authorized and provisioned with parameters to use the service provided by 5G ProSe inter-UE relay. 5G ProSe inter-UE relay is authorized and provisioned with parameters to provide the service of relaying traffic among 5G ProSe end UEs.

[0349] 1. The source 5G ProSe end UE (ie, UE-1) wants to establish unicast communication with the target 5G ProSe end UE (ie, UE-2) and broadcasts a direct communication request. The parameters contained in the direct communication request message are described in clause 6.4.3.7.

[0350] The relay_indication in the direct communication request is used to indicate whether the 5G ProSe inter-UE relay can forward the direct communication request message. It is also used to limit the number of hops of the 5G ProSe inter-UE relay by removing the relay_indication in the direct communication request message from the 5G ProSe inter-UE relay.

[0351] The source layer 2 ID and destination layer 2 ID for the direct communication request message are defined in clause 5.8.5.

[0352] NOTE 1: The data type of relay_indication can be determined in phase 3.

[0353] 2. When receiving a direct communication request with relay_indication from UE-1, the 5G ProSe inter-UE relays (i.e., Relay-1 and Relay-2) may decide to participate in the procedure and broadcast a direct communication request message without relay_indication in its vicinity. The parameters included in the direct communication request message are described in clause 6.4.3.7.

[0354] The source layer 2 ID and destination layer 2 ID for the direct communication request message are defined in clause 5.8.5.

[0355] 3. When UE-2 receives a direct communication request from one or more 5G ProSe inter-UE relays, UE-2 selects a 5G ProSe inter-UE relay to which UE-2 will respond. UE-2 may select a 5G ProSe inter-UE relay based on, for example, signal strength, local policy, operator policy for each relay service code (if any).

[0356] 4. If required, security establishment occurs between UE-2 and the selected 5G ProSe Inter-UE Relay (here Relay-1).

[0357] If an existing PC5 link can be reused, then Link Modification Request and Link Modification Accept messages are used.

[0358] NOTE 2: Conflicts between link modification requests and direct communication requests may be determined in phase 3.

[0359] 5. UE-2 replies a direct communication accept message to relay-1. The parameters included in the direct communication accept message are described in clause 6.4.3.7.

[0360] 6. For IP services, an IPv6 prefix or IPv4 address is allocated to the target 5G ProSe layer 3 end UE as defined in clause 5.5.1.4.

[0361] 7. If required, security establishment occurs between UE-1 and Relay-1.

[0362] 8. For 5G ProSe inter-UE relay communication with integrated discovery, after receiving the QoS information of end-to-end QoS from UE-1, Relay-1 provides QoS information of second-hop QoS to UE-2 using a Link Modification Request message.

[0363] 9. For 5G ProSe inter-UE relay communication with integrated discovery, UE-2 responds with a Link Modification Accept message.

[0364] 10. Relay-1 responds to UE-1 with a Direct Communication Accept. The parameters contained in the Direct Communication Accept message are described in clause 6.4.3.7.

[0365] 11. For IP services, an IPv6 prefix or IPv4 address is allocated to the source 5G ProSe layer 3 end UE as defined in clause 5.5.1.4.

[0366] 12. For IP communication, the 5G ProSe layer 3 inter-UE relay may store the association of the user information ID and the IP address of the target 5G ProSe layer 3 end UE into its DNS entry, and the 5G ProSe layer 3 inter-UE relay may act as a DNS server for other UEs. If the IP address of the target 5G ProSe layer 3 end UE is not received in step 10, then after step 11, the source 5G ProSe layer 3 end UE may send a DNS query to the 5G ProSe layer 3 inter-UE relay to request the IP address of the target 5G ProSe layer 3 end UE, and the 5G ProSe layer 3 inter-UE relay returns the IP address of the target 5G ProSe layer 3 end UE to the source 5G ProSe layer 3 end UE.

[0367] For Ethernet communication, the 5G ProSe Layer 3 inter-UE relay acts as an Ethernet switch by maintaining the association between the PC5 link and the Ethernet MAC address received from the 5G ProSe Layer 3 end UE.

[0368] For unstructured traffic communications, for each pair of source and target 5G ProSe layer 3 end UEs, the 5G ProSe layer 3 inter-UE relay maintains a 1:1 mapping between the PC5 link with the source 5G ProSe layer 3 end UE and the PC5 link with the target 5G ProSe layer 3 end UE.

[0369] The source 5G ProSe layer 3 end UE communicates with the target 5G ProSe layer 3 end UE via a 5G ProSe layer 3 inter-UE relay.

[0370] 3GPP TS24.554 introduces the following:

[0371] 7.2.2 5G ProSe direct link establishment procedure

[0372] 7.2.2.1 General

[0373] Depending on the type of 5G ProSe direct link establishment procedure (i.e., Layer 2 link establishment for UEs or Layer 2 link establishment for ProSe services in 3GPP TS 23.304 [2]), the 5G ProSe direct link establishment procedure is used to establish a 5G ProSe direct link between two UEs or to establish multiple 5G ProSe direct links between a UE and multiple target UEs. The UE that sends the request message is referred to as the "initiating UE" and the other UE is referred to as the "target UE". If the request message does not indicate a specific target UE (i.e., target user information is not included in the request message) and multiple target UEs are interested in the ProSe application indicated in the request message, the initiating UE shall handle the corresponding response messages received from those target UEs. The maximum number of 5G ProSe direct links established in a UE at a time shall not exceed the implementation-specific maximum number of established 5G ProSe direct links.

[0374] NOTE 1: The recommended maximum number of established 5G ProSe direct links is 8.

[0375] When the 5G ProSe direct link establishment procedure for the 5G ProSe Layer 3 remote UE is successfully completed, and if there is a PDU session established for relaying the traffic of the 5G ProSe remote UE, the 5G ProSe Layer 3 UE to network relay UE shall perform the remote UE reporting procedure as specified in 3GPP TS 24.501

[11] .

[0376] NOTE 2: A single PC5 unicast link is established between the 5G ProSe Layer 2 UE to 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] .

[0377] 7.2.2.2 5G ProSe direct link establishment procedure initiated by the initiating UE

[0378] The initiating UE shall meet the following prerequisites before initiating this procedure:

[0379] a) A request from an upper layer to transmit a data packet for a ProSe application via PC5, or a request from a lower layer to trigger the establishment of a ProSe direct link;

[0380] b) the communication mode is unicast mode (e.g. pre-configured as specified in clause 5.2.4 or indicated by upper layers);

[0381] c) the link layer identifier for the initiating UE (i.e., Layer 2 ID for unicast communication) is available (e.g., pre-configured or self-assigned) and is not used by other existing 5G ProSe direct links within the initiating UE;

[0382] d) a link layer identifier for the destination UE (i.e., the unicast Layer 2 ID or broadcast Layer 2 ID of the target UE) is available to the initiating UE (e.g., pre-configured, obtained as specified in clause 5.2, known via previous ProSe direct communication, or indicated by lower layers);

[0383] NOTE 1: In the case where different ProSe applications are mapped to distinct default destination Layer 2 IDs, when the initiating UE wishes to establish a single unicast link that can be used for more than one ProSe identifier, the UE may select any one of the default destination Layer 2 IDs for unicast initial signaling.

[0384] e) The initiating UE is authorized for 5G ProSe direct communication on PC5 in NR-PC5 in the serving PLMN, has a valid authorization for 5G ProSe direct communication on PC5 in NR-PC5 when not served by NG-RAN, is authorized to use a 5G ProSe UE to Network Relay UE, is authorized to use a 5G ProSe Inter-UE Relay UE or is authorized to act as a 5G ProSe Inter-UE Relay UE. The UE is considered not to be served by NG-RAN if the following conditions are met:

[0385] 1) Not served by NG-RAN for ProSe direct communication via PC5;

[0386] 2) in the limited service state as specified in 3GPP TS 23.122

[14] , provided that the reason why the UE is in the limited service state is one of the following;

[0387] i) The UE cannot find a suitable cell in the selected PLMN, as specified in 3GPP TS 38.304

[15] ;

[0388] ii) the UE receives a REGISTRATION REJECT message or SERVICE REJECT message with 5GMM Cause #11 “PLMN not allowed” as specified in 3GPP TS 24.501

[11] ; or

[0389] iii) the UE receives a REGISTRATION REJECT message or SERVICE REJECT message with 5GMM Cause #7 “5GS service not allowed” as specified in 3GPP TS 24.501

[11] ; or

[0390] 3) is in a limited service state as specified in 3GPP TS 23.122

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

[0391] Editor's note: The 5G ProSe direct link establishment procedure is used for the UE characteristics in the limited service state in the case of direct communication between 5G ProSe end UE and 5G ProSe inter-UE relay UE, which needs to be re-discussed, and this will be determined by SA2.

[0392] f) there is no existing 5G ProSe direct link for a pair of peer application layer IDs, or there is an existing 5G ProSe direct link for a pair of peer application layer IDs, and:

[0393] 1) The network layer protocol of the existing 5G ProSe direct link is different from the network layer protocol required by the upper layer for this ProSe application in the initiating UE;

[0394] 2) The security policy (signaling security policy or user plane security policy) corresponding to the ProSe identifier is not compatible with the security policy of the existing 5G ProSe direct link; or

[0395] 3) In case the 5G ProSe direct link establishment procedure is used for direct communication between a 5G ProSe layer 3 remote UE and a 5G ProSe layer 3 UE to a network relay UE, an existing 5G ProSe direct link for peer UEs is established with a different RSC or is established not for direct communication between a 5G ProSe layer 3 remote UE and a 5G ProSe layer 3 UE to a network relay UE;

[0396] 4) in case the 5G ProSe direct link establishment procedure is for direct communication between a 5G ProSe Layer 2 Remote UE and a 5G ProSe Layer 2 UE to a network relay UE, an existing 5G ProSe direct link for peer UEs 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 network relay UE; or

[0397] 5) In case the 5G ProSe direct link establishment procedure is used for direct communication between a 5G ProSe layer 3 end UE and a 5G ProSe layer 3 inter-UE relay UE, the existing 5G ProSe direct link for peer UEs is established with a different RSC, or is established but not used for direct communication between a 5G ProSe layer 3 end UE and a 5G ProSe layer 3 inter-UE relay UE;

[0398] g) the number of established 5G ProSe direct links is less than an implementation-specific maximum number of established 5G ProSe direct links allowed in the UE at any one time;

[0399] 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.

[0400] i) in the case that: 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 a 5G ProSe layer 3 end UE and a 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 an 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 a 5G ProSe inter-UE relay communication with the additional 5G ProSe layer 3 end UE, as specified in clause 7.2.3.2; and

[0401] j) The initiating UE has received a PROSE direct link establishment request message including a relay indication, and the initiating UE acts as a 5G ProSe inter-UE relay UE, and the 5G ProSe direct link establishment procedure is used for direct communication between the 5G ProSe inter-UE relay UE and the 5G ProSe end UE

[0402] After receiving service data or request from upper layers, the initiating UE shall derive PC5 QoS parameters and assign a PQFI for establishing a PC5 QoS flow as specified in clause 7.2.7.

[0403] If the 5G ProSe direct link establishment procedure is used for direct communication between a 5G ProSe remote UE and a 5G ProSe UE to network relay UE, the UE shall apply DUCK or DUSK with the associated encrypted bitmask for UE to network relay discovery and a UTC-based counter for encryption:

[0404] a) Relay service code; and

[0405] b) UP-PRUK ID or CP-PRUK ID (if applicable),

[0406] As specified in clause 6.3.5.2 of 3GPP TS 33.503

[34] , the UE shall use the security-protected relay service code and the security-protected UP-PRUK ID or the security-protected CP-PRUK ID to create the ProSe Direct Link Setup Request message.

[0407] NOTE 2: If the UE is configured neither to use DUCK nor DUSK, the relay service code and UP-PRUK ID or CP-PRUK ID are not encrypted.

[0408] If the 5G ProSe direct link establishment procedure is used for direct communication between a 5G ProSe inter-UE relay UE and a target 5G ProSe end UE, if 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 as specified in clause 5.2.4 and a relay indication is included), then the initiating UE acting as a 5G ProSe inter-UE relay UE initiates the 5G ProSe direct link establishment procedure to the target 5G ProSe end UE.

[0409] If the 5G ProSe direct link establishment procedure is used for direct communication between a 5G ProSe inter-UE relay UE and a target 5G ProSe end UE, then without integrated discovery, after successfully completing the 5G ProSe direct link security mode control procedure with the source 5G ProSe end UE, the initiating UE acting as the 5G ProSe inter-UE relay UE initiates the 5G ProSe direct link establishment procedure to the target 5G ProSe end UE.

[0410] Editor's note: When the direct link modification procedure can be used between a 5G ProSe inter-UE relay UE and a target 5G ProSe end UE is for further study.

[0411] To initiate the 5G ProSe direct link establishment procedure, the initiating UE will generate a ProSe direct link establishment request message. The initiating UE:

[0412] a) contains source user information, which is set to the application layer ID of the initiating UE received from the upper layer, or is set to the user information ID of the source 5G ProSe UE when the 5G ProSe direct link establishment procedure is used for 5G ProSe direct communication between a 5G ProSe UE and a 5G ProSe inter-UE relay UE;

[0413] b) shall contain the ProSe identifier received from upper layers if the 5G ProSe direct link establishment procedure is not used for 5G ProSe direct communication between a 5G ProSe remote UE and a 5G ProSe UE to a network relay UE;

[0414] c) The target user information shall be included, which shall be set to the application layer ID of the target UE if received from upper layers or if known based on the unicast layer 2 ID of the target UE (i.e., the destination layer 2 ID) as described in clause 5.8.2.4 of 3GPP TS 23.304 [3], to the user information ID of the 5G ProSe UE to network relay UE obtained during the 5G ProSe UE to network relay discovery procedure, or to the user information ID of the target 5G ProSe end UE:

[0415] 1) If the initiating UE acts as the source 5G ProSe end UE and the user information ID of the target 5G ProSe end UE is obtained during the 5G ProSe inter-UE relay discovery procedure; or

[0416] 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 the PROSE direct link modification request message from the source 5G ProSe end UE;

[0417] ca) The inter-UE relay UE user information including the user information ID set as the 5G ProSe inter-UE relay UE:

[0418] 1) If obtained during the 5G ProSe inter-UE relay discovery procedure, and the 5G ProSe direct link establishment procedure is used for 5G ProSe direct communication between the source 5G ProSe end UE and the 5G ProSe inter-UE relay UE; or

[0419] 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 clause 5.2.7;

[0420] cb) if the initiating UE acts as a source 5G ProSe end UE, and the layer 2 ID of the target 5G ProSe end UE is available in the source 5G ProSe end UE via previous direct communication, then the target UE layer 2 ID set to the layer 2 ID of the target 5G ProSe end UE shall be included;

[0421] 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:

[0422] 1) If the UE PC5 unicast signaling integrity protection policy is set to "signaling integrity protection required" or "signaling integrity protection preferred", then the key establishment information container shall be included, and if the UE PC5 unicast signaling integrity protection policy is set to "signaling integrity protection not required", then the key establishment information container may be included;

[0423] NOTE 3: The key establishment information container is provided by the upper layer.

[0424] e) will include:

[0425] 1) Nonce_1, if the direct communication is not between a 5G ProSe Remote UE and a 5G ProSe UE to a Network Relay UE, or 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 are used as specified in 3GPP TS 33.503

[34] ; or

[0426] 2) K NRP Freshness parameter 1, if direct communication is between 5G ProSe Remote UE and 5G ProSe UE to Network Relay UE, and security procedures on the control plane are used as specified in 3GPP TS 33.503

[34] ;

[0427] If the UE PC5 unicast signaling integrity protection policy is set to "Signaling integrity protection required" or "Signaling integrity protection preferred", then set to the 128-bit temporary value generated by the initiating UE for session key establishment over this 5G ProSe direct link;

[0428] Note 4: The Nonce_1 IE in the ProSe direct link establishment request message is used to store Nonce_1 or K NRP The value of freshness parameter 1.

[0429] f) shall contain its UE security capabilities, indicating the list of algorithms supported by the initiating UE for security establishment of this 5G ProSe direct link;

[0430] g) If the UE PC5 unicast signalling integrity protection policy is set to "Signaling integrity protection required" or "Signaling integrity protection preferred", then the K selected by the initiating UE as specified in 3GPP TS 33.503

[34] shall be included. NRP-sess MSB of ID;

[0431] NOTE 5: If the direct communication is not between 5G ProSe remote UE and 5G ProSe UE to network relay UE, then K NRP-sess ID remains corresponding to K NRP-sess If the direct communication is between a 5G ProSe remote UE and a 5G ProSe UE to a network relay UE, then K NRP-sess ID remains corresponding to K NRP-sess (if security procedures on the user plane are used) or K relay-sess The ID of the control plane security program if you are using it.

[0432] h) may contain K NRP ID, provided that the initiating UE has an existing K NRP , and direct communication is not between 5G ProSe remote UE and 5G ProSe UE to network relay UE;

[0433] i) shall contain its UE PC5 unicast signaling security policy. In case different ProSe applications are mapped to different PC5 unicast signaling security policies, when the initiating UE wishes to establish a single unicast link that can be used for more than one ProSe application, each of the signaling security policies of those ProSe applications shall be compatible, for example, "signaling integrity protection not required" and "signaling integrity protection required" are not compatible. In case 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, the signaling integrity protection policy shall be set to "signaling integrity protection required";

[0434] j) containing the Relay Service Code IE, which is set to the Relay Service Code of the target relay UE when the 5G ProSe direct link establishment procedure is used for direct communication between a 5G ProSe remote UE and a 5G ProSe UE to a network relay UE, or is set to the Relay Service Code indicating the connectivity service requested by the source 5G ProSe end UE when the 5G ProSe direct link establishment procedure is used for direct communication between a (source or target) 5G ProSe end UE and a 5G ProSe inter-UE relay UE;

[0435] k) contain the UTC-based counter LSBs, which are set to the four least significant bits of the UTC-based counter in case 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;

[0436] l) shall contain the UE Identity IE, which is set to the SUCI of the originating UE in the following cases:

[0437] 1) 5G ProSe direct link establishment procedure is used for direct communication between 5G ProSe remote UE and 5G ProSe UE to network relay UE; and

[0438] 2) security for 5G ProSe UE to network relay uses security procedures 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 security procedures on the user plane and the initiating UE does not have a valid UP-PRUK as specified in 3GPP TS 33.503

[34] ;

[0439] m) shall contain the User Security Key ID IE, which shall be set to:

[0440] 1) The UP-PRUK ID of the initiating UE, if:

[0441] i) 5G ProSe direct link establishment procedure is used for direct communication between 5G ProSe remote UE and 5G ProSe UE to network relay UE;

[0442] ii) the initiating UE has a valid UP-PRUK; and

[0443] iii) security for 5G ProSe UE to network relay using security procedures on the user plane as specified in 3GPP TS 33.503

[34] ; or

[0444] 2) The CP-PRUK ID of the originating UE associated with the relay service code of the target UE, provided that:

[0445] i) 5G ProSe direct link establishment procedure is used for direct communication between 5G ProSe remote UE and 5G ProSe UE to network relay UE;

[0446] ii) the originating UE has a valid CP-PRUK associated with the relay service code of the target UE; and

[0447] iii) Security for 5G ProSe UE to network relay uses security procedures on the control plane as specified in 3GPP TS 33.503

[34] ;

[0448] n) shall contain the HPLMN ID of the originating UE, provided that the UP-PRUK ID of the originating UE is included and is not in NAI format (see 3GPP TS 33.503

[34] );

[0449] o) shall include the MIC IE, which is set to the calculated MIC value in the case where the 5G ProSe Direct Link Establishment procedure is used for direct communication between a 5G ProSe Remote UE and a 5G ProSe UE to Network Relay UE and the UE has a DUIK, as specified in clause 6.3.5.3 of 3GPP TS 33.503

[34] ; and

[0450] p) shall include a relay indication indicating that the PROSE direct link establishment request message may be forwarded by a 5G ProSe inter-UE relay UE, provided that the 5G ProSe direct link establishment procedure is used for direct communication between the source 5G ProSe end UE and the 5G ProSe inter-UE relay UE;

[0451] Editor's note: Security parameters for 5G ProSe inter-UE relay and parameters for 5G ProSe layer 2 inter-UE relay are for further study.

[0452] After generating the ProSe Direct Link Setup Request message, the initiating UE passes this message together with the source Layer 2 ID and the destination Layer 2 ID to the lower layers for transmission as follows:

[0453] a) If the 5G ProSe direct communication is due to 5G ProSe direct discovery as defined in clauses 6.2.14, 6.2.15, 8.2.1 and 8a.2.1:

[0454] self-assigned source layer 2 ID, and

[0455] 1) Destination Layer 2 ID, which is set to the target UE Layer 2 ID received in the PROSE Direct Link Setup 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;

[0456] 2) otherwise, set to the destination Layer 2 ID of the source Layer 2 ID in the received PROSE PC5 DISCOVERY message for the discovery procedure;

[0457] b) If the initiating UE acts as a source 5G ProSe end UE and the 5G ProSe direct link establishment procedure is used for direct communication with integrated discovery between the source 5G ProSe end UE and the 5G ProSe interUE relay UE:

[0458] self-assigns a Source Layer 2 ID and sets the Destination Layer 2 ID to the configured Broadcast Destination Layer 2 ID as specified in clause 5.2.4; or

[0459] c) If the initiating UE acts as a 5G ProSe inter-UE relay UE and the 5G ProSe direct link establishment procedure is used for direct communication with integrated discovery between the 5G ProSe inter-UE relay UE and the target 5G ProSe end UE:

[0460] Assign your own source layer 2 ID, and set the destination layer 2 ID to:

[0461] 1) Target UE Layer 2 ID, if received in the PROSE Direct Link Setup Request message from the source 5G ProSe UE; otherwise

[0462] 2) a broadcast destination layer 2 ID configured as specified in clause 5.2.4; or

[0463] d) Otherwise:

[0464] self-assigned source Layer 2 ID and a destination Layer 2 ID set to the destination Layer 2 ID used for unicast initial signalling as specified in clause 5.2.4,

[0465] NOTE 6: The UE implementation ensures that any value of the self-assigned source Layer 2 ID in a) and b) is different from any other self-assigned source Layer 2 ID used for 5G ProSe direct discovery as specified in clauses 6.2.14, 6.2.15 and 8.2.1, and is different from any other destination Layer 2 ID provided as specified in clause 5.2.

[0466] NOTE 6A: The UE implementation ensures that any value of the self-assigned Source Layer 2 ID in a) and b) is different from any self-assigned Source Layer 2 ID when used for 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 Inter-UE Relay UE and a target 5G ProSe Layer 3 end UE.

[0467] NOTE 6B: The UE implementation ensures that any value of the self-assigned Source Layer 2 ID in a) and b) is different from any other self-assigned Source Layer 2 ID and different pairs of User Information ID of the source 5G ProSe side UE and User Information ID of the target 5G ProSe side UE in 5G ProSe direct communication for unstructured traffic, if the 5G ProSe direct link establishment procedure is used for 5G ProSe direct communication between a 5G ProSe Layer 3 Inter-UE Relay UE and a target 5G ProSe Layer 3 side UE and for unstructured traffic.

[0468] NOTE 7: It is possible for the initiating UE to reuse the Layer 2 ID of the initiating UE used in the previous 5G ProSe direct link with the same peer UE, except that the 5G ProSe direct link establishment procedure is used for 5G ProSe direct communication between a 5G ProSe Layer 3 inter-UE relay UE and a target 5G ProSe Layer 3 end UE for unstructured traffic and different pairs of User Information ID of the source 5G ProSe end UE and User Information ID of the target 5G ProSe end UE, and the 5G ProSe direct link establishment procedure is used for 5G ProSe direct communication between a 5G ProSe Layer 3 inter-UE relay UE and a target 5G ProSe Layer 3 end UE whose data unit type is different from that of the previous 5G ProSe direct link.

[0469] And start timer T5080.

[0470] NOTE 8: The preset PC5 DRX configuration is used to transmit the ProSe Direct Link Establishment Request message as specified in 3GPP TS 38.300

[21] .

[0471] When the timer T5080 is running, the UE shall not send a new ProSe direct link setup request message to the same target UE identified by the same application layer ID. If the target user information IE is not included in the ProSe direct link setup request message (i.e., 5G ProSe direct link setup procedure for ProSe applications), the initiating UE shall process multiple ProSe direct link setup accept messages (if any) received from different target UEs for establishing multiple 5G ProSe direct links before the timer T5080 expires.

[0472] NOTE 9: To ensure a successful 5G ProSe direct link establishment, T5080 should be set to a value greater than the sum of T5089 and T5092.

[0473] [3GPP TS24.554 V18.1.0 titled "5G ProSe direct link establishment procedure towards UE" Figure 7 .2.2.2.1 is reproduced as Fig.13 ]

[0474] [3GPP TS 24.554 V18.1.0 titled "5G ProSe direct link establishment procedures for ProSe services" Figure 7 .2.2.2.2 is reproduced as Fig.14 ]

[0475] 7.2.2.3 5G ProSe direct link establishment procedure accepted by target UE

[0476] After receiving the ProSe direct link establishment request message, if the target UE accepts this request, the target UE will uniquely assign a PC5 link identifier and generate a 5G ProSe direct link context.

[0477] NOTE 1: The PC5 DRX configuration is preset for receiving the ProSe Direct Link Establishment Request message as specified in 3GPP TS 38.300

[21] .

[0478] If the ProSe direct link setup request message is for 5G ProSe direct communication between a 5G ProSe remote UE and a 5G ProSe UE to a network relay UE, the target UE shall verify the MIC field in the received ProSe direct link setup request with the DUIK (if present) and decrypt the encrypted one using DUCK or DUSK:

[0479] a) Relay service code; and

[0480] b) UP-PRUK ID or CP-PRUK ID (if received),

[0481] The associated encrypted bit mask is used for 5G ProSe UE to Network Relay Discovery (see clause 6.3.5.2 of 3GPP TS 33.503

[34] ) and verifies whether the Relay Service Code matches the code sent by the target UE during the 5G ProSe UE to Network Relay Discovery procedure.

[0482] NOTE 2: If the UE is configured neither to use DUCK nor DUSK, the relay service code and UP-PRUK ID or CP-PRUK ID are not encrypted.

[0483] If the target UE acts as a target 5G ProSe end UE and the 5G ProSe direct link establishment procedure is used for direct communication with integrated discovery between a 5G ProSe inter-UE relay UE and a 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 as 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 clause 6.7.3.2 of TS 23.304.

[0484] If the 5G ProSe direct link establishment procedure is not used for direct communication between a 5G ProSe remote UE and a 5G ProSe UE to a network relay UE, the target UE may initiate a 5G ProSe direct link authentication procedure as specified in clause 7.2.12 and shall initiate a 5G ProSe direct link security mode control procedure as specified in clause 7.2.10.

[0485] 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, the target UE shall proceed to:

[0486] a) authentication and key agreement procedures as specified in clause 5.5.4 of 3GPP TS 24.501

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

[34] are used; or

[0487] b) the Key Request procedure as specified in clause 8.2.10.2.4, provided that the security procedures on the user plane as specified in 3GPP TS 33.503

[34] are used;

[0488] And the 5G ProSe direct link security mode control procedure shall be initiated as specified in clause 7.2.10.

[0489] In the 5G ProSe direct link context, the target UE shall set the source Layer 2 ID and destination Layer 2 ID as specified in clauses 7.2.12 and 7.2.10, and store the corresponding source Layer 2 ID for unicast communication and store the destination Layer 2 ID for unicast communication.

[0490] if:

[0491] a) The Target User Information IE is included in the ProSe Direct Link Setup Request message, and this IE contains the application layer ID of the target UE; or

[0492] b) the target user information IE is not included in the ProSe direct link setup request message, and the target UE is interested in the ProSe application identified by the ProSe identifier IE in the ProSe direct link setup request message;

[0493] Next, the target UE will:

[0494] a) If the direct communication is not between 5G ProSe Remote UE and 5G ProSe UE to Network Relay UE:

[0495] 1) Based on K contained in the ProSe direct link establishment request message NRP ID, identifies the existing K NRP ;or

[0496] 2) If K NRP The ID is not included in the ProSe direct link establishment request message, and the target UE does not have the ID for the K included in the ProSe direct link establishment request message. NRP ID's existing K NRP , or the target UE wishes to derive a new K NRP , then derive the new K NRP This may require performance of one or more 5G ProSe direct link authentication procedures as specified in clause 7.2.12;

[0497] 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, a new K is requested according to the security procedures on the user plane specified in 3GPP TS 33.503

[34] . NR_ProSe ;or

[0498] c) 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 user plane specified in 3GPP TS 33.503

[34] are used, then a new K is requested according to the security procedures on the user plane. NRP .

[0499] Note 3: How many times do you need to perform the 5G ProSe direct link certification procedure to derive a new K NRP Depends on the authentication method used.

[0500] In identifying the existing K NRP Or export new K NRP Afterwards, or upon receiving a new K NRP or K NR_ProSeAfterwards, the target UE shall initiate the 5G ProSe direct link security mode control procedure as specified in clause 7.2.10.

[0501] After the 5G ProSe direct link security mode control procedure is successfully completed, in order to determine whether the ProSe direct link establishment request message is acceptable, in the case of IP communication, the target UE checks whether there is at least one common IP address configuration option supported by both the initiating UE and the target UE.

[0502] Prior to sending the ProSe Direct Link Setup Accept message to the 5G ProSe Remote UE, the target UE acting as a 5G ProSe Layer 3 UE to the Network Relay UE initiates the UE-Requested PDU Session Establishment procedure as specified in 3GPP TS 24.501

[11] , provided that:

[0503] 1) a PDU session for relaying services associated with the RSC has not been established; or

[0504] 2) A PDU session for relaying services associated with the RSC has been established, but the PDU session type is unstructured.

[0505] If the target UE accepts the 5G ProSe direct link establishment procedure, the target UE will generate a ProSe direct link establishment acceptance message.

[0506] a) contains source user information, which is set to the application layer ID of the target UE received from the upper layer, or is set to the user information ID of the target 5G ProSe UE when the 5G ProSe direct link establishment procedure is used for 5G ProSe direct communication between a 5G ProSe UE and a 5G ProSe inter-UE relay UE;

[0507] aa) shall contain the Inter-UE Relay UE User Information, which is set to the User Information ID of the 5G ProSe Inter-UE Relay UE in case the 5G ProSe Direct Link Establishment Procedure is used for 5G ProSe direct communication between the source 5G ProSe end UE and the 5G ProSe Inter-UE Relay UE; b) shall contain the PQFI, the corresponding PC5 QoS parameters and optionally the ProSe Identifier accepted by the target UE, if the target UE does not act as a 5G ProSe Layer 2 UE to network relay UE 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 Inter-UE Relay UE;

[0508] c) PC5 QoS rules may be included, provided that the target UE does not act as a 5G ProSe Layer 2 UE to network relay UE, and the 5G ProSe direct link establishment procedure 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 inter-UE relay UE;

[0509] Editor's note: How to forward PC5 QoS parameters and PQFI of PC5 QoS flows between 5G ProSe layer 3 inter-UE relay UE and 5G ProSe layer 3 end UE is for further study.

[0510] d) If IP communication is used and the target UE does not act as a 5G ProSe Layer 2 UE to Network Relay UE, then an IP Address Configuration IE set to one of the following values ​​shall be included:

[0511] 1) "DHCPv4 server", if only IPv4 address allocation mechanism is supported by the target UE, i.e. acting as a DHCPv4 server;

[0512] 2) "IPv6 router", if only the IPv6 address allocation mechanism is supported by the target UE, i.e. acting as an IPv6 router;

[0513] 3) "DHCPv4 server and IPv6 router", if both IPv4 and IPv6 address allocation mechanisms are supported by the target UE; or

[0514] 4) “Address allocation not supported”, if both IPv4 and IPv6 address allocation mechanisms are not supported by the target UE and the target UE does not act as a 5G ProSe Layer 3 UE to network relay UE;

[0515] NOTE 4: If the communication uses Ethernet or Unstructured Data Unit Type, the UE does not include the IP Address Configuration IE nor the Link-Local IPv6 Address IE.

[0516] e) if the IP Address Configuration IE is set to "Address Allocation Not Supported", the received ProSe Direct Link Security Mode Complete message contains the Link-Local IPv6 Address IE and the target UE acts neither as a 5G ProSe Layer 2 UE to Network Relay UE nor as a 5G ProSe Layer 3 Relay UE, then the Link-Local IPv6 Address IE formed locally based on IETF RFC 4862

[25] shall be included;

[0517] f) shall include the configuration of UE PC5 unicast user plane security protection based on the agreed user plane security policy, as specified in 3GPP TS 33.503

[34] ;

[0518] Editor's note: Security parameters for 5G ProSe inter-UE relay and parameters for 5G ProSe layer 2 inter-UE relay are for further study.

[0519] g) if the 5G ProSe direct link establishment procedure is used for 5G ProSe direct communication between a source or target 5G ProSe Layer 3 end UE and a 5G ProSe Layer 3 inter-UE relay UE and is used for Ethernet services, then the MAC address of the target 5G ProSe Layer 3 end UE shall be included; and

[0520] h) may include the target 5G ProSe layer 3 end UE IP address IE, which is set to the IP address of the target 5G ProSe layer 3 end UE if the 5G ProSe direct link establishment procedure is used for 5G ProSe direct communication between the source 5G ProSe layer 3 end UE and the 5G ProSe layer 3 inter-UE relay UE and the data unit type of the communication is IP.

[0521] Editor's note: Security parameters for 5G ProSe inter-UE relay and parameters for 5G ProSe layer 2 inter-UE relay are for further study.

[0522] After generating the ProSe Direct Link Setup Accept message, the initiating UE passes this message together with the layer 2 ID of the initiating UE for unicast communication and the layer 2 ID of the target UE for unicast communication to the lower layer for transmission, and starts the timer T5090 in the following cases:

[0523] a) at least one ProSe identifier used for the 5G ProSe direct link satisfies the privacy requirements specified in clause 5.2.4; or

[0524] b) T5090 is configured as specified in clause 5.2.5.

[0525] NOTE 5: Two UEs negotiate the PC5 DRX configuration in the AS layer and the PC5 DRX parameter value is configured based on a pair of source / destination Layer 2 IDs in the AS layer, as specified in 3GPP TS 38.300

[21] .

[0526] After sending the ProSe Direct Link Setup Accept message, the target UE provides the following information together with the Layer 2 ID to the lower layers, which enables the lower layers to process the incoming PC5 signaling or service data:

[0527] a) a self-assigned PC5 link identifier for this 5G ProSe direct link;

[0528] b) PQFI and its corresponding PC5 QoS parameters (if applicable); and

[0529] c) an indication to activate PC5 unicast user plane security protection for 5G ProSe direct link (if applicable).

[0530] If the target UE accepts the 5G ProSe direct link establishment request and the 5G ProSe direct link is established but not for 5G ProSe direct communication between a 5G ProSe remote UE and a 5G ProSe UE to network relay UE and not for 5G ProSe direct communication between a 5G ProSe end UE and a 5G ProSe inter-UE relay UE, then the target UE may perform PC5 QoS flow establishment on the 5G ProSe direct link as specified in clause 7.2.7. If the 5G ProSe direct link is established for 5G ProSe layer 3 remote UE and a 5G ProSe layer 3 UE to network relay UE, then the target UE may perform PC5 QoS flow establishment on the 5G ProSe direct link as specified in clause 8.2.6. If the 5G ProSe direct link is established for 5G ProSe direct communication between a 5G ProSe layer 3 end UE and a 5G ProSe layer 3 inter-UE relay UE, then the target UE may perform PC5 QoS flow establishment on the 5G ProSe direct link as specified in clause 8a.2.7.

[0531] 7.2.2.4 Completion of 5G ProSe direct link establishment procedure by initiating UE

[0532] If the target user information IE is included in the ProSe direct link setup request message, the initiating UE shall stop timer T5080 after receiving the ProSe direct link setup accept message. If the target user information IE is not included in the ProSe direct link setup request message, the initiating UE may keep timer T5080 running and continue to process multiple response messages (i.e., ProSe direct link setup accept messages) from multiple target UEs.

[0533] For each of the received ProSe Direct Link Setup Accept messages, the initiating UE shall uniquely assign a PC5 link identifier and generate a 5G ProSe direct link context for each of the 5G ProSe direct links. The initiating UE then stores the source layer 2 ID and destination layer 2 ID used in the transmission of this message provided by the lower layers in the 5G ProSe direct link context to complete the establishment of the 5G ProSe direct link with the target UE. From this time on, the initiating UE shall use the established link for ProSe direct communication over PC5 and additional PC5 signaling messages to the target UE.

[0534] If the initiating UE acts as a 5G ProSe inter-UE relay and the 5G ProSe direct link establishment procedure is used for direct communication with integrated discovery between the 5G ProSe inter-UE relay UE and the target 5G ProSe side UE, then after receiving the PROSE direct link establishment accept message from the target 5G ProSe side UE, the initiating UE shall initiate the 5G ProSe direct link security mode control procedure with the source 5G ProSe side UE, and after successfully completing the 5G ProSe direct link security mode control procedure with the source 5G ProSe side UE, the initiating UE shall create a PROSE direct link establishment accept message as specified in clause 7.2.2.3 to send to the source 5G ProSe side UE.

[0535] After receiving the ProSe Direct Link Setup Accept message, the initiating UE provides the following information together with the Layer 2 ID to the lower layer so that the lower layer can process the incoming PC5 signaling or service data:

[0536] a) a self-assigned PC5 link identifier for this 5G ProSe direct link;

[0537] b) PQFI and its corresponding PC5 QoS parameters (if applicable); and

[0538] c) an indication to activate PC5 unicast user plane security protection for 5G ProSe direct link (if applicable).

[0539] The initiating UE shall start timer T5090 if:

[0540] a) at least one ProSe identifier used for the 5G ProSe direct link satisfies the privacy requirements specified in clause 5.2.4; or

[0541] b) T5090 is configured as specified in clause 5.2.5.

[0542] Additionally, the initiating UE may perform PC5 QoS flow establishment on the 5G ProSe direct link as specified in clause 7.2.7.

[0543] After timer T5080 expires, if the ProSe direct link establishment request message does not include the target user information IE and the initiating UE receives at least one ProSe direct link establishment accept message, it is up to the UE implementation to regard the 5G ProSe direct link establishment procedure as completed or restart the timer T5080.

[0544] If the 5G ProSe direct link establishment procedure is triggered by a ProSe direct link modification request message from a source 5G ProSe layer 3 end UE, as specified in clause 7.2.3.2, then in the case where the initiating UE acts as a 5G ProSe layer 3 inter-UE relay UE, upon receiving the ProSe direct link establishment accept message, the initiating UE shall send a ProSe direct link modification accept message to the source 5G ProSe layer 3 end UE, as specified in clause 7.2.3.3.

[0545] 7.2.2.5 5G ProSe direct link establishment procedure not accepted by target UE

[0546] If the ProSe direct link setup request message cannot be accepted, the target UE shall send a ProSe direct link setup reject message. The ProSe direct link setup reject message contains the PC5 signaling protocol cause IE set to one of the following cause values:

[0547] #1 Direct communication with the target UE is not allowed;

[0548] #3 A conflict of layer 2 IDs for unicast communication is detected;

[0549] #5 Lack of resources for 5G ProSe direct links;

[0550] #13 Congestion situation;

[0551] #15 5G ProSe UE to network relay security procedure failure;

[0552] #20 Failure from 5G ProSe UE; or

[0553] #111 Unspecified protocol error.

[0554] If the target UE is not allowed to accept the ProSe Direct Link Establishment Request message, for example, based on operator policy or configuration parameters for ProSe direct communication over PC5, as specified in clause 5.2, or the target UE acts as a 5G ProSe Layer 3 UE to a network relay UE in a disallowed area of ​​its serving PLMN and the corresponding relay service code is not associated with high priority access, as defined in clause 5.3.5 of 3GPP TS 24.501

[11] , then the target UE shall send a ProSe Direct Link Establishment Reject message with PC5 signalling protocol cause value #1 “Direct communication with target UE not allowed”.

[0555] NOTE 1: When a target UE acting as a 5G ProSe Layer 3 UE to network relay UE is involved in its own emergency services as specified in 3GPP TS 24.501

[11] or handles emergency services of another 5G ProSe Layer 3 remote UE, and receives a ProSe Direct Link Setup Request message with an RSC specific to emergency services, the target UE is allowed to ignore the ProSe Direct Link Setup Request message if it decides to prioritize its own ongoing emergency services or handle emergency services of other 5G ProSe Layer 3 remote UEs due to local regulations or implementation-specific requirements.

[0556] For a ProSe Direct Link Setup Request message received from a Layer 2 ID (for unicast communication), if the target UE already has an existing link established to the UE using this Layer 2 ID or is currently processing a ProSe Direct Link Setup Request message from the same Layer 2 ID and one of the following parameters is different from the existing link or the link for which link setup is in progress:

[0557] a) Source user information;

[0558] b) the type of data (e.g. IP, Ethernet or unstructured); or

[0559] c) Security policy,

[0560] The target UE shall send a ProSe direct link setup reject message with PC5 signaling protocol cause value #3 “Conflict of Layer 2 IDs for unicast communication detected”.

[0561] NOTE 2: If the UE is processing a ProSe direct discovery message for the same source Layer 2 ID from a received ProSe direct link setup request message, then avoiding the conflict of the destination Layer 2 ID is up to the UE implementation (e.g., sending a ProSe direct link setup reject message with PC5 signaling protocol cause value #3 "Conflict of Layer 2 IDs detected for unicast communication" or ignoring the ProSe direct discovery message).

[0562] NOTE 3: The type of data (e.g., IP, Ethernet, or unstructured) is indicated by the optional IP Address Configuration IE included in the corresponding Direct Link Security Mode Complete message, i.e., if this IE is included, then the type of data for the requested link is IP type, and if this IE is not included, then the type of data for the requested link is Ethernet or unstructured.

[0563] If the 5G ProSe direct link establishment fails due to the implementation-specific maximum number of established 5G ProSe direct links having been reached or other temporary lower layer problems causing resource constraints, the target UE shall send a ProSe Direct Link Setup Reject message with PC5 signaling protocol cause value #5 “Lack of resources for 5G ProSe direct link”.

[0564] If the 5G ProSe direct link establishment request is for 5G ProSe UE to network relay and:

[0565] a) activating NAS-level mobility management congestion control as specified in clause 5.3.9 of TS 24.501

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

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

[0567] The target UE shall send a ProSe direct link setup reject message with PC5 signaling protocol cause value #13 "Congestion situation". The target UE may provide the back-off timer value to the initiating UE in the ProSe direct link setup reject message. If the back-off timer for NAS-level mobility management congestion control is running, the target UE shall not accept any 5G ProSe direct link setup request for relaying.

[0568] If the 5G ProSe direct link establishment request is for a 5G ProSe UE to network relay, NAS level session management congestion as specified in clauses 6.2.7 and 6.2.8 of TS 24.501

[11] is activated at the target UE acting as a 5G ProSe Layer 3 UE to network relay UE, the relay service code for the 5G ProSe direct link establishment corresponds to a DNN and / or S-NSSAI in which NAS level session management congestion is activated, and the target UE needs to perform a PDU Session Establishment Procedure for DNN and / or S-NSSAI or a PDU Session Modification Procedure for DNN and / or S-NSSAI, then the target UE shall send a ProSe Direct Link Establishment Reject message with PC5 signaling protocol cause value #13 "Congestion Situation". The target UE may provide the back-off timer value to the initiating UE in the ProSe Direct Link Establishment Reject message.

[0569] NOTE 4: How the target UE determines that it is under congestion is implementation specific (eg, any relay related operation overhead, etc.).

[0570] NOTE 5: In case the target UE is under NAS level mobility management congestion control, setting the back-off timer value provided to the initiating UE to the remaining time of the mobility management back-off timer T3346 or with an additional offset value is an implementation option.

[0571] If the 5G ProSe direct link establishment request is for a 5G ProSe Layer 3 UE to network relay, the request requires the establishment of a PDU session with the 5G ProSe Layer 3 UE to network relay UE as the target UE, and the PDU session establishment is unsuccessful due to receiving 5GSM cause #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 TS 24.501

[11] , then the target UE shall send a ProSe direct link establishment reject message with PC5 signaling protocol cause value #111 "unspecified protocol error".

[0572] If the 5G ProSe direct link establishment request is for 5G ProSe inter-UE relay and:

[0573] a) The target UE acting as the target 5G ProSe end UE is in congestion;

[0574] The target UE shall send a ProSe direct link setup reject message with PC5 signaling protocol cause value #13 “Congestion situation.” The target UE may provide the back-off timer value to the initiating UE in the ProSe direct link setup reject message.

[0575] After receiving the ProSe direct link establishment reject message from the target 5G ProSe end UE, the initiating UE acts as a 5G ProSe inter-UE relay UE, and the 5G ProSe direct link establishment procedure is used for direct communication between the source 5G ProSe end UE and the 5G ProSe inter-UE relay UE, the target 5G ProSe end UE has rejected the 5G ProSe direct link establishment procedure or the 5G ProSe direct link modification procedure, the rejection message contains a back-off value, the initiating UE has not reached the maximum number of allowed retransmissions, the initiating UE will notify (message TBD) the source 5G ProSe end UE that the target 5G ProSe end UE has rejected the link establishment or link modification request, and will provide the cause value from the target 5G ProSe end UE.

[0576] Editor's note: How the target 5G ProSe UE notifies the 5G ProSe inter-UE relay UE that it has rejected the link establishment or link modification request is for further study.

[0577] After receiving a ProSe direct link setup reject message from a target 5G ProSe side UE, the initiating UE acts as a 5G ProSe inter-UE relay UE, the 5G ProSe direct link setup procedure is used for direct communication between the source 5G ProSe side UE and the 5G ProSe inter-UE relay UE, the target 5G ProSe side UE has rejected the 5G ProSe direct link setup procedure or the 5G ProSe direct link modification procedure, the reject message contains a backoff value, and the initiating UE has reached the maximum number of allowed retransmissions, the initiating UE may send a ProSe direct link setup reject message with an appropriate PC5 signaling protocol cause value to the source 5G ProSe side UE. The initiating UE shall include the PC5 protocol cause value #xx “Failure from 5G ProSe side UE” in the ProSe direct link setup reject message, and include the PC5 side UE failure cause IE set to #13 “Congestion situation” received from the target 5G ProSe side UE that has rejected the 5G ProSe direct link setup or 5G ProSe direct link modification procedure. The initiating UE may include the target UE information IE set to the user information ID of the target 5G ProSe UE in the ProSe direct link establishment rejection message.

[0578] If the 5G ProSe direct link establishment request is for 5G ProSe inter-UE relay and:

[0579] a) The target UE acting as a 5G ProSe inter-UE relay UE is in congestion;

[0580] The target UE shall send a ProSe direct link setup reject message with PC5 signaling protocol cause value #13 “Congestion situation.” The target UE may provide the back-off timer value to the initiating UE in the ProSe direct link setup reject message.

[0581] If the 5G ProSe direct link establishment procedure is used for direct communication between a 5G ProSe remote UE and a 5G ProSe UE to network relay UE and fails due to a failure of the security procedure on the control plane or the security procedure on the user plane as specified in 3GPP TS 33.503

[34] , the target UE shall send a ProSe direct link establishment reject message with PC5 signaling protocol cause value #15 “5G ProSe UE to network relay security procedure failure”. The target UE shall 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] .

[0582] If the target UE acts as a target 5G ProSe end UE and the 5G ProSe direct link establishment procedure is between a 5G ProSe inter-UE relay UE and the target 5G ProSe end UE, the target 5G ProSe end UE may include the following in the ProSe direct link establishment reject message:

[0583] a) Source UE Information IE set to the User Information ID of the source 5G ProSe UE;

[0584] b) Target UE Information IE set to the User Information ID of the target 5G ProSe UE; and

[0585] c) Inter-UE relay UE information IE set to the user information ID of the 5G ProSe inter-UE relay UE.

[0586] 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 end UE and the 5G ProSe inter-UE relay UE, and the target 5G ProSe end UE has rejected the 5G ProSe direct link establishment procedure or the 5G ProSe direct link modification procedure, then the 5G ProSe inter-UE relay UE shall send a ProSe direct link establishment reject message with a PC5 signaling protocol cause value #20 "Failure from 5G ProSe end UE" to the source 5G ProSe end UE. The 5G ProSe inter-UE relay UE may include the PC5 end UE failure cause IE in the ProSe direct link establishment reject message, which is set to the PC5 signaling protocol cause received from the target 5G ProSe end UE that has rejected the 5G ProSe direct link establishment procedure. The 5G ProSe inter-UE relay UE may include the following in the ProSe direct link establishment reject message:

[0587] a) Source UE Information IE set to the User Information ID of the source 5G ProSe UE;

[0588] b) Target UE Information IE set to the User Information ID of the target 5G ProSe UE; and

[0589] c) Inter-UE relay UE information IE set to the user information ID of the 5G ProSe inter-UE relay UE.

[0590] NOTE 6: Cause value #15 “5G ProSe UE to Network Relay Security Procedure Failure” is also used when no CP-PRUK or UP-PRUK is found in the network.

[0591] If the 5G ProSe direct link establishment fails for other reasons, the target UE shall send a ProSe direct link establishment reject message with PC5 signaling protocol cause value #111 “Unspecified protocol error”.

[0592] After sending the ProSe Direct Link Establishment Reject message, the target UE shall provide the following information to the lower layer along with the Layer 2 ID of the initiating UE for unicast communication and the Layer 2 ID of the target UE for unicast communication:

[0593] a) Indication of deactivation of PC5 unicast security protection and deletion of security context for 5G ProSe direct link (if applicable).

[0594] Upon receiving the ProSe direct link setup reject message, the initiating UE shall stop timer T5080 and abort the 5G ProSe direct link setup procedure. If the PC5 signaling protocol cause value in the ProSe direct link setup reject message is #1 "Direct communication with target UE not allowed" or #5 "Lack of resources for 5G ProSe direct link", the initiating UE shall not attempt to initiate a 5G ProSe direct link setup procedure with the same target UE for at least a time period T. If the PC5 signaling protocol cause value in the ProSe direct link setup reject message is #13 "Congestion situation" and a back-off timer value is provided in the ProSe direct link setup reject message, the initiating UE shall start timer T5088 associated with the layer 2 ID of the target UE and set its value to the provided timer value. If the PC5 signaling protocol cause value in the ProSe Direct Link Setup Reject message is #15 "Security procedures failure of 5G ProSe UE to Network Relay" and the initiating UE has included the UE Identity IE set to the SUCI in the ProSe Direct Link Setup Request message, the initiating UE shall initiate the UE to Network Relay reselection procedure as specified in clause 8.2.3. If the PC5 signaling protocol cause value in the ProSe Direct Link Setup Reject message is #15 "Security procedures failure of 5G ProSe UE to Network Relay" and the initiating UE has included the User Security Key ID IE set to the UP-PRUK ID or CP-PRUK ID in the ProSe Direct Link Setup Request message, the initiating UE may initiate the UE to Network Relay reselection procedure as specified in clause 8.2.3 and the UE shall further:

[0595] 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 the subsequent 5G ProSe Direct Link Establishment procedure, as specified in clause 7.2.2.2; or

[0596] b) If a different 5G ProSe UE to network relay UE is selected, the User Security Key ID IE set to the previously used UP-PRUK ID or CP-PRUK ID is included in the ProSe Direct Link Establishment Request message.

[0597] NOTE 7: The length of the time period T is UE implementation specific and may be different for the cases when the UE receives PC5 signaling protocol cause value #1 "Direct communication to target UE not allowed" or when the UE receives PC5 signaling protocol cause value #5 "Lack of resources for 5G ProSe direct link".

[0598] Editor's note: Security related content is for further study and depends on SA3 requirements.

[0599] After receiving the ProSe Direct Link Establishment Reject message, the initiating UE shall provide the following information to the lower layer along with the Layer 2 ID of the initiating UE for unicast communication and the Layer 2 ID of the target UE for unicast communication:

[0600] a) Indication of deactivation of PC5 unicast security protection and deletion of security context for 5G ProSe direct link (if applicable).

[0601] 7.2.2.6 Abnormal situations

[0602] 7.2.2.6.1 Abnormal situation at the initiating UE

[0603] If the timer T5080 expires and the target user information IE is included in the ProSe direct link setup request message, the initiating UE shall retransmit the ProSe direct link setup request message and restart the timer T5080. After reaching the maximum number of allowed retransmissions, the initiating UE shall abort the 5G ProSe direct link establishment procedure and may notify the upper layers that the target UE is unreachable.

[0604] After the timer T5080 expires, if the ProSe direct link setup request message does not include the target user information IE and the initiating UE does not receive any ProSe direct link setup accept message, the initiating UE may retransmit the ProSe direct link setup request message and restart the timer T5080. If the ProSe direct link setup request message does not include the target user information IE and the initiating UE does not receive any ProSe direct link setup accept message, the initiating UE shall abort the 5G ProSe direct link setup procedure after reaching the maximum number of allowed retransmissions and may notify the upper layers that the target UE is unavailable.

[0605] NOTE: The maximum number of allowed retransmissions is UE implementation specific.

[0606] If the link establishment is no longer required before completing the procedure, the initiating UE shall abort the procedure.

[0607] When the initiating UE aborts the 5G ProSe direct link establishment procedure, the initiating UE shall provide the following information to the lower layers 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:

[0608] a) Indication of deactivation of PC5 unicast security protection and deletion of security context for 5G ProSe direct link (if applicable).

[0609] 7.2.2.6.2 Abnormal conditions at the target UE

[0610] For a ProSe Direct Link Setup Request message received from a Source Layer 2 ID (for unicast communication), if the target UE already has an existing link established 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 shall process the new request. However, the target UE shall only delete the existing 5G ProSe direct link context after the new link establishment procedure is successful.

[0611] NOTE: The type of data (e.g., IP, Ethernet, or unstructured) is indicated by the optional IP address configuration included in the corresponding ProSe Direct Link Security Mode Complete message, i.e., if this IE is included, the type of data for the requested link is IP type, and if this IE is not included, the type of data for the requested link is Ethernet or unstructured.

[0612] 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 using DUIK, DUSK or DUCK (where the associated encrypted bit mask is used for 5G ProSe UE to network relay discovery), 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 shall abort the 5G ProSe direct link establishment procedure.

[0613] 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 a network relay UE, the message integrity is protected, and the integrity verification of the message fails at the target UE, then the target UE shall abort the 5G ProSe direct link establishment procedure.

[0614] 7.2.3 5G ProSe direct link modification procedure

[0615] 7.2.3.1 General

[0616] The purpose of the 5G ProSe Direct Link Modification procedure is to modify the existing ProSe Direct Link to:

[0617] a) Add new PC5 QoS flows to the existing 5G ProSe direct link;

[0618] b) modifying an existing PC5 QoS flow to update the PC5 QoS parameters of the existing PC5 QoS flow;

[0619] c) modifying the existing PC5 QoS flow to associate the new ProSe application with the existing PC5 QoS flow;

[0620] d) modifying an existing PC5 QoS flow to remove the associated ProSe application from the existing PC5 QoS flow;

[0621] e) Remove the existing PC5 QoS flow from the existing 5G ProSe direct link;

[0622] f) Negotiate a new 5G ProSe inter-UE relay UE on the existing 5G ProSe direct link;

[0623] g) establishing 5G ProSe inter-UE relay communication with an additional 5G ProSe layer 3 end UE using an existing 5G ProSe direct link between the 5G ProSe layer 3 end UE and the 5G ProSe layer 3 inter-UE relay UE; or

[0624] h) releasing the 5G ProSe inter-UE relay communication with one of the peer 5G ProSe layer 3 end UEs using a shared 5G ProSe direct link between the 5G ProSe layer 3 end UE and the 5G ProSe layer 3 inter-UE relay UE.

[0625] 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".

[0626] Note: The 5G ProSe direct link modification procedure is not applicable to the 5G ProSe layer 2 UE to network relay case.

[0627] 7.2.3.2 5G ProSe direct link modification procedure initiated by the initiating UE

[0628] The initiating UE shall meet the following prerequisites before initiating this procedure to add a new ProSe application to an existing 5G ProSe direct link:

[0629] a) There is a 5G ProSe direct link between the initiating UE and the target UE;

[0630] b) a pair of application layer IDs and network layer protocols for this 5G ProSe direct link are the same as those required by the application layer in the initiating UE of this ProSe application; c) the security policy corresponding to the ProSe identifier is consistent with the security policy of the existing 5G ProSe direct link;

[0631] d) Timer T5091 is not running; and

[0632] e) The initiating UE does not perform the 5G ProSe direct link key update procedure initiated by the target UE.

[0633] The initiating UE shall satisfy the following prerequisites before initiating this procedure for negotiating a new 5G ProSe inter-UE relay UE over an existing 5G ProSe direct link:

[0634] a) The initiating UE is a source 5G ProSe UE that communicates with a target 5G ProSe UE via a 5G ProSe inter-UE relay UE;

[0635] b) The initiating UE determines to perform inter-UE relay reselection, for example based on PC5 signal strength; and

[0636] c) The initiating UE obtains a list of candidate inter-UE relays via the inter-UE discovery procedure.

[0637] After receiving service data or request from upper layers, the initiating UE shall perform PC5 QoS flow matching as specified in clause 7.2.8. If there is no matching PC5 QoS flow, the initiating UE shall derive PC5 QoS parameters and assign a PQFI for the PC5 QoS flow to be established as specified in clause 7.2.7.

[0638] If the 5G ProSe direct link modification procedure is to add a new PC5 QoS flow to an existing 5G ProSe direct link, the initiating UE shall create a ProSe Direct Link Modification Request message. In this message, the initiating UE:

[0639] a) shall contain the PQFI, the corresponding PC5 QoS parameters and an optional ProSe identifier;

[0640] b) shall contain a link modification operation code set to “add a new PC5 QoS flow to an existing 5G ProSe direct link”;

[0641] c) may contain PC5 QoS rules to indicate packet filters for PC5 QoS flows;

[0642] d) including the source UE information set to the user information ID of the source 5G ProSe layer 3 end UE, if the UE acts as a 5G ProSe layer 3 inter-UE relay UE, the 5G ProSe direct link is between the 5G ProSe layer 3 inter-UE relay UE and the target 5G ProSe layer 3 end UE, and multiple source 5G ProSe layer 3 end UEs have established direct communication with the target 5G ProSe layer 3 end UE via the 5G ProSe layer 3 inter-UE relay UE using the same 5G ProSe direct link;

[0643] e) may include source UE information set to the user information ID of the source 5G ProSe end 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 end UE, and only one source 5G ProSe end UE has established direct communication with the target 5G ProSe end UE via the 5G ProSe inter-UE relay UE using the 5G ProSe direct link;

[0644] f) including the target UE information set to the user information ID of the target 5G ProSe layer 3 end UE, if the UE acts as a source 5G ProSe layer 3 end UE, the 5G ProSe direct link is between the source 5G ProSe layer 3 end UE and a 5G ProSe layer 3 inter-UE relay UE, and the source 5G ProSe layer 3 end UE has established direct communications with multiple target 5G ProSe layer 3 end UEs via the 5G ProSe layer 3 inter-UE relay UE using the same 5G ProSe direct link;

[0645] g) may include target UE information set to the user information ID of the target 5G ProSe UE, provided that:

[0646] 1) The UE acts as a source 5G ProSe end UE, the 5G ProSe direct link is between the source 5G ProSe end UE and the 5G ProSe inter-UE relay UE, and the source 5G ProSe end UE establishes direct communication with only one target 5G ProSe end UE via the 5G ProSe inter-UE relay UE using the 5G ProSe direct link; or

[0647] 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

[0648] h) may contain the target UE Layer 2 ID set to the Layer 2 ID of the target 5G ProSe UE if the UE acts as a source 5G ProSe UE and the 5G ProSe direct link is between the source 5G ProSe UE and a 5G ProSe inter-UE relay UE.

[0649] If the 5G ProSe direct link modification procedure is to modify the PC5 QoS parameters of an existing PC5 QoS flow in an existing 5G ProSe direct link, the initiating UE shall create a ProSe Direct Link Modification Request message. In this message, the initiating UE:

[0650] a) It will contain PQFI and corresponding PC5 QoS parameters, including ProSe identifier;

[0651] b) shall contain a link modification operation code set to "Modify PC5 QoS parameters of an existing PC5 QoS flow";

[0652] c) may contain PC5 QoS rules to indicate packet filters for PC5 QoS flows;

[0653] d) including the source UE information set to the user information ID of the source 5G ProSe layer 3 end UE, if the UE acts as a 5G ProSe layer 3 inter-UE relay UE, the 5G ProSe direct link is between the 5G ProSe layer 3 inter-UE relay UE and the target 5G ProSe layer 3 end UE, and multiple source 5G ProSe layer 3 end UEs have established direct communication with the target 5G ProSe layer 3 end UE via the 5G ProSe layer 3 inter-UE relay UE using the same 5G ProSe direct link;

[0654] e) may include source UE information set to the user information ID of the source 5G ProSe end 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 end UE, and only one source 5G ProSe end UE has established direct communication with the target 5G ProSe end UE via the 5G ProSe inter-UE relay UE using the 5G ProSe direct link;

[0655] f) including the target UE information set to the user information ID of the target 5G ProSe layer 3 end UE, if the UE acts as a source 5G ProSe layer 3 end UE, the 5G ProSe direct link is between the source 5G ProSe layer 3 end UE and a 5G ProSe layer 3 inter-UE relay UE, and the source 5G ProSe layer 3 end UE has established direct communications with multiple target 5G ProSe layer 3 end UEs via the 5G ProSe layer 3 inter-UE relay UE using the same 5G ProSe direct link;

[0656] g) may include target UE information set to the user information ID of the target 5G ProSe UE, provided that:

[0657] 1) The UE acts as a source 5G ProSe end UE, the 5G ProSe direct link is between the source 5G ProSe end UE and the 5G ProSe inter-UE relay UE, and the source 5G ProSe end UE establishes direct communication with only one target 5G ProSe end UE via the 5G ProSe inter-UE relay UE using the 5G ProSe direct link; or

[0658] 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

[0659] h) may contain the target UE Layer 2 ID set to the destination Layer 2 ID of the target 5G ProSe UE if the UE acts as a source 5G ProSe UE and the 5G ProSe direct link is between the source 5G ProSe UE and a 5G ProSe inter-UE relay UE.

[0660] If the 5G ProSe direct link modification procedure is to associate a new ProSe application with an existing PC5 QoS flow, the initiating UE shall create a ProSe direct link modification request message. In this message, the initiating UE:

[0661] a) It will contain PQFI and corresponding PC5 QoS parameters, including ProSe identifier;

[0662] b) shall contain a link modification operation code set to “associate a new ProSe application with an existing PC5 QoS flow”;

[0663] c) may contain PC5 QoS rules to indicate packet filters for PC5 QoS flows;

[0664] d) including the source UE information set to the user information ID of the source 5G ProSe layer 3 end UE, if the UE acts as a 5G ProSe layer 3 inter-UE relay UE, the 5G ProSe direct link is between the 5G ProSe layer 3 inter-UE relay UE and the target 5G ProSe layer 3 end UE, and multiple source 5G ProSe layer 3 end UEs have established direct communication with the target 5G ProSe layer 3 end UE via the 5G ProSe layer 3 inter-UE relay UE using the same 5G ProSe direct link;

[0665] e) may include source UE information set to the user information ID of the source 5G ProSe end 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 end UE, and only one source 5G ProSe end UE has established direct communication with the target 5G ProSe end UE via the 5G ProSe inter-UE relay UE using the 5G ProSe direct link;

[0666] f) including the target UE information set to the user information ID of the target 5G ProSe layer 3 end UE, if the UE acts as a source 5G ProSe layer 3 end UE, the 5G ProSe direct link is between the source 5G ProSe layer 3 end UE and a 5G ProSe layer 3 inter-UE relay UE, and the source 5G ProSe layer 3 end UE has established direct communications with multiple target 5G ProSe layer 3 end UEs via the 5G ProSe layer 3 inter-UE relay UE using the same 5G ProSe direct link;

[0667] g) may include target UE information set to the user information ID of the target 5G ProSe UE, provided that:

[0668] 1) The UE acts as a source 5G ProSe end UE, the 5G ProSe direct link is between the source 5G ProSe end UE and the 5G ProSe inter-UE relay UE, and the source 5G ProSe end UE establishes direct communication with only one target 5G ProSe end UE via the 5G ProSe inter-UE relay UE using the 5G ProSe direct link; or

[0669] 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

[0670] h) may contain the target UE Layer 2 ID set to the Layer 2 ID of the target 5G ProSe UE if the UE acts as a source 5G ProSe UE and the 5G ProSe direct link is between the source 5G ProSe UE and a 5G ProSe inter-UE relay UE.

[0671] If the PC5 5G ProSe direct link modification procedure is to remove the associated ProSe application from an existing PC5 QoS flow, the initiating UE shall create a ProSe direct link modification request message. In this message, the initiating UE:

[0672] a) will contain the PQFI and corresponding PC5 QoS parameters, including the ProSe identifier; and

[0673] b) shall contain a Link Modification Operation Code set to “Remove ProSe Application from Existing PC5 QoS Flow”.

[0674] If the direct link modification procedure is to remove any PC5 QoS flow from an existing 5G ProSe direct link, the initiating UE shall create a ProSe Direct Link Modification Request message. In this message, the initiating UE:

[0675] a) will include the PQFI; and

[0676] b) shall contain a link modification operation code set to “Remove existing PC5 QoS flow from existing 5G ProSe direct link”.

[0677] If the 5G ProSe direct link modification procedure is to establish a 5G ProSe inter-UE relay communication with an additional 5G ProSe layer 3 end UE using an existing 5G ProSe direct link between a 5G ProSe layer 3 end UE and a 5G ProSe layer 3 inter-UE relay UE, the initiating UE shall create a ProSe direct link modification request message. In this message, the initiating UE:

[0678] a) contains the source UE information set to the source user information ID of the 5G ProSe layer 3 end UE received in the PROSE direct link setup 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 end UE;

[0679] b) For Ethernet traffic, the MAC address of the source 5G ProSe Layer 3 end UE shall be included 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 end UE;

[0680] c) including the target UE information set to the user information ID of the additional target 5G ProSe layer 3 UE to which the 5G ProSe inter-UE relay communication is requested, if the UE acts as a source 5G ProSe layer 3 UE and the 5G ProSe direct link is between the source 5G ProSe layer 3 UE and the 5G ProSe layer 3 inter-UE relay UE;

[0681] d) setting the ProSe identifier received from upper layers if the UE acts as a source 5G ProSe Layer 3 end UE or to the ProSe identifier received in the ProSe Direct Link Setup Request message if the UE acts as a 5G ProSe Layer 3 inter-UE relay UE;

[0682] Editor's note: Whether to include the PQFI and the corresponding PC5 QoS parameters including the ProSe identifier instead of just the ProSe identifier is for further study.

[0683] Editor's note: Whether to include and how to set the ProSe identifier for the 5G ProSe direct link between the source 5G ProSe layer 3 end UE and the 5G ProSe layer 3 inter-UE relay UE and the 5G ProSe direct link between the 5G ProSe layer 3 inter-UE relay UE and the target 5G ProSe layer 3 end UE is for further study.

[0684] e) will contain a link modification operation code set to “add a new 5G ProSe layer 3 end UE to an existing 5G ProSe direct link”; and

[0685] f) may contain the target UE Layer 2 ID set to the Layer 2 ID of the target 5G ProSe Layer 3 UE, if the UE acts as a source 5G ProSe Layer 3 UE and the 5G ProSe direct link is between the source 5G ProSe Layer 3 UE and a 5G ProSe Layer 3 inter-UE relay UE.

[0686] If the 5G ProSe direct link modification procedure is to release the 5G ProSe inter-UE relay communication with the peer 5G ProSe layer 3 end UE using a shared 5G ProSe direct link between the 5G ProSe layer 3 end UE and the 5G ProSe layer 3 inter-UE relay UE, the initiating UE shall create a ProSe direct link modification request message. In this message, the initiating UE:

[0687] a) contains the source UE information set to 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;

[0688] b) the target UE information including the user information ID of the peer 5G ProSe layer 3 end UE with which the 5G ProSe inter-UE relay communication is to be released, 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

[0689] c) shall contain a link modification operation code set to "Remove 5G ProSe layer 3 end UE from an existing 5G ProSe direct link".

[0690] If the 5G ProSe direct link modification procedure is to trigger inter-UE relay reselection, the initiating UE shall create a ProSe direct link modification request message. In this message:

[0691] 1) If the initiating UE acts as a source 5G ProSe end UE, and the 5G ProSe direct link is between the source 5G ProSe end UE and the 5G ProSe inter-UE relay UE, then the initiating UE:

[0692] a) will contain a relay reselection indication;

[0693] b) a list containing candidate 5G ProSe inter-UE relay UE user information IDs;

[0694] c) If IP communication is used, a list of target 5G ProSe UE IP addresses / prefixes will be included; and

[0695] d) may contain a list of candidate 5G ProSe Inter-UE Relay UE Layer 2 IDs.

[0696] 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:

[0697] a) will contain a relay reselection indication;

[0698] b) a list containing candidate 5G ProSe inter-UE relay UE user information IDs;

[0699] c) if IP communication is used, the originating 5G ProSe UE IP address / prefix will be included; and

[0700] d) may contain a list of candidate 5G ProSe Inter-UE Relay UE Layer 2 IDs.

[0701] Editor's Note: The ProSe direct link modification request message needs to be updated.

[0702] If the 5G ProSe direct link modification procedure is to trigger relay reselection, and the initiating UE acts as a 5G ProSe inter-UE relay UE, then the initiating UE shall create a ProSe direct link modification request message for each IP address / prefix of the target 5G ProSe UE received from the 5G ProSe source UE on the associated ProSe direct link modification request message.

[0703] After the ProSe direct link modification request message is generated, the initiating UE passes this message together with the layer 2 ID of the initiating UE for 5G ProSe direct communication and the layer 2 ID of the target UE for 5G ProSe direct communication to the lower layer for transmission, and starts the timer T5081. While the timer T5081 is running, the UE shall not send a new ProSe direct link modification request message to the same target UE.

[0704] [3GPP TS24.554 V18.1.0 titled “5G ProSe direct link modification procedures” Figure 7 .2.3.2.1 is reproduced as Fig.15 ]

[0705] [3GPP TS 24.554 V18.1.0 entitled "5G ProSe direct link modification procedures for Layer 3 inter-UE relay reselection" Figure 7 .2.3.2.2 is reproduced as Fig.16 ]

[0706] 7.2.3.3 5G ProSe Direct Link Modification Procedure Accepted by Target UE

[0707] If the ProSe direct link modification request message is accepted, the target UE shall respond with a ProSe direct link modification accept message.

[0708] If the ProSe direct link modification request message will add a new ProSe application, add a new PC5 QoS flow or modify any existing PC5 QoS flow in the 5G ProSe direct link, the target UE:

[0709] a) shall contain the PQFI, the corresponding PC5 QoS parameters and, optionally, the ProSe identifier accepted by the target UE;

[0710] b) PC5 QoS rules may include packet filters for indicating PC5 QoS flows;

[0711] c) including the source UE information set to the user information ID of the source 5G ProSe layer 3 end UE, if the UE acts as a target 5G ProSe layer 3 end UE, the 5G ProSe direct link is between the 5G ProSe layer 3 inter-UE relay UE and the target 5G ProSe layer 3 end UE, and the target 5G ProSe layer 3 end UE has established direct communications with multiple source 5G ProSe layer 3 end UEs using the same 5G ProSe direct link by the 5G ProSe layer 3 inter-UE relay UE; and

[0712] d) may include source UE information set to the user information ID of the source 5G ProSe end UE, if the UE acts as a target 5G ProSe end UE, the 5G ProSe direct link is between the 5G ProSe inter-UE relay UE and the target 5G ProSe end UE, and the target 5G ProSe end UE has established direct communication with only one source 5G ProSe end UE using the 5G ProSe direct link by the 5G ProSe inter-UE relay UE; and

[0713] e) including the target UE information set to 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 layer 3 UE has established direct communications with multiple target 5G ProSe layer 3 UEs by the 5G ProSe layer 3 inter-UE relay UE using the same 5G ProSe direct link;

[0714] f) the target UE information may include 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 established direct communication with only one target 5G ProSe UE using the 5G ProSe direct link by the 5G ProSe inter-UE relay UE;

[0715] In the ProSe Direct Link Modification Accept message.

[0716] If the ProSe direct link modification request message is to remove an existing ProSe application from the 5G ProSe direct link, the target UE will delete the ProSe identifier received in the ProSe direct link modification request message and the corresponding PQFI and PC5 QoS parameters from the attribute set associated with the 5G ProSe direct link.

[0717] If the ProSe direct link modification request message is to remove an existing PC5 QoS flow from a PC5 5G ProSe direct link, the target UE will delete the PQFI and corresponding PC5 QoS parameters from the attribute set associated with the 5G ProSe direct link.

[0718] 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 provides the added or modified PQFI and corresponding PC5 QoS parameters and PC5 link identifier to the lower layer.

[0719] If the ProSe direct link modification request message is to remove an existing ProSe application or to remove an existing PC5 QoS flow from the 5G ProSe direct link, then after sending the ProSe direct link modification accept message, the target UE provides the removed PQFI and PC5 link identifier to the lower layer.

[0720] If the ProSe direct link modification request message is to establish a 5G ProSe inter-UE relay communication with an additional 5G ProSe layer 3 end UE using an existing 5G ProSe direct link between a 5G ProSe layer 3 end UE and a 5G ProSe layer 3 inter-UE relay UE, the target UE:

[0721] a) if acting as a 5G ProSe Layer 3 inter-UE relay UE, shall perform the 5G ProSe direct link establishment procedure towards the target 5G ProSe Layer 3 end UE as specified in clause 7.2.2.2; and upon receiving a ProSe Direct Link Setup Accept message from the target 5G ProSe Layer 3 end UE, shall create a ProSe Direct Link Modification Accept message;

[0722] b) if acting as a target 5G ProSe Layer 3 end UE, a ProSe Direct Link Modification Accept message shall be created; and

[0723] c) In the ProSe Direct Link Modification Accept message, the target UE:

[0724] 1) If the UE acts as a target 5G ProSe Layer 3 UE, the source UE information shall be included with the user information ID set to that of the source 5G ProSe Layer 3 UE; or

[0725] 2) If the UE acts as a 5G ProSe layer 3 inter-UE relay UE:

[0726] i) including the target UE information set to the user information ID of the target 5G ProSe layer 3 UE;

[0727] ii) for IP services, a target 5G ProSe Layer 3 UE IP address IE set to the IP address of the additional target 5G ProSe Layer 3 UE may be included; and

[0728] iii) For Ethernet services, the MAC address of the target 5G ProSe layer 3 end UE will be included.

[0729] If the ProSe direct link modification request message is to release a 5G ProSe inter-UE relay communication with one of the peer 5G ProSe Layer 3 end UEs using a shared 5G ProSe direct link between the 5G ProSe Layer 3 end UE and a 5G ProSe Layer 3 inter-UE relay UE, then the target UE:

[0730] a) If acting as a 5G ProSe Layer 3 inter-UE relay UE, one of the following procedures may be initiated towards the target 5G ProSe Layer 3 end UE:

[0731] 1) 5G ProSe Direct Link Release procedure, as specified in clause 7.2.6.2, for releasing the 5G ProSe direct link with a peer 5G ProSe Layer 3 end UE; or

[0732] 2) 5G ProSe direct link modification procedure, as specified in clause 7.2.3.2, for removing the corresponding PC5 QoS flow if the UE determines to maintain the 5G ProSe direct link with the peer 5G ProSe Layer 3 end UE; and

[0733] b) A ProSe Direct Link Modification Accept message shall be created, and in this message, the target UE:

[0734] 1) include the source UE information set to the user information ID of the source 5G ProSe Layer 3 UE, if the UE acts as a target 5G ProSe Layer 3 UE; or

[0735] 2) The target UE information shall be included as the user information ID of the target 5G ProSe layer 3 UE if the UE acts as a 5G ProSe layer 3 inter-UE relay UE.

[0736] 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 network relay UE, and if the initiating UE is a 5G ProSe remote UE, then the target UE (as a 5G ProSe layer 3 UE to network relay UE) performs the QoS flow handling procedure as specified in clauses 8.2.6.3.3 and clauses 8.2.6.4.2.

[0737] If the ProSe direct link modification request message is for inter-UE relay UE reselection, the target UE may perform a 5G ProSe inter-UE relay discovery procedure with the user information ID of the candidate 5G ProSe inter-UE relay in the discovery message, and may set the layer 2 ID of the candidate 5G ProSe inter-UE relay as the destination layer 2 ID to carry the discovery message, if received in the ProSe direct link modification request message.

[0738] 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 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.

[0739] If the ProSe Direct Link Modification Request message is accepted to trigger relay reselection, the target UE shall respond with a ProSe Direct Link Modification Accept message. In this message:

[0740] 1) If the target UE acts as a target 5G ProSe end UE and the 5G ProSe direct link is between the target 5G ProSe end UE and the 5G ProSe inter-UE relay UE, then the target UE:

[0741] a) will contain a relay reselection indication;

[0742] b) will contain the new 5G ProSe inter-UE relay UE user information ID;

[0743] c) will contain the UE IP address of the initiating 5G ProSe; and

[0744] d) If IP communication is used, it will contain the target 5G ProSe end UE IP address to be used with the newly selected 5G ProSe inter-UE relay UE.

[0745] 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 end UE, then the target UE.

[0746] a) will contain a relay reselection indication;

[0747] b) will contain the new 5G ProSe inter-UE relay UE user information ID;

[0748] c) will contain the target 5G ProSe UE IP address; and

[0749] d) If IP communication is used, it will contain the target 5G ProSe end UE IP address to be used with the newly selected 5G ProSe inter-UE relay UE.

[0750] Editor's Note: The ProSe Direct Link Modification Accept message needs to be updated.

[0751] If the target UE accepts the 5G ProSe direct link modification request, the target UE may perform PC5 QoS flow establishment on the 5G ProSe direct link as specified in clause 7.2.7, and perform PC5 QoS flow matching on the 5G ProSe direct link as specified in clause 7.2.8.

[0752] 7.2.3.4 Completion of 5G ProSe Direct Link Modification Procedure by Initiating UE

[0753] After receiving the ProSe direct link modification accept message, the initiating UE shall stop timer T5081.

[0754] After receiving the ProSe direct link modification accept 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, the initiating UE shall provide the added or modified PQFI and corresponding PC5 QoS parameters and PC5 link identifier to the lower layers.

[0755] After receiving the ProSe direct link modification accept message, if the ProSe direct link modification request message is to remove an existing ProSe application or to remove an existing PC5 QoS flow from the 5G ProSe direct link, the initiating UE provides the removed PQFI and PC5 link identifier to the lower layer.

[0756] Upon receiving the ProSe direct link modification accept message, if the ProSe direct link modification request message is to establish a 5G ProSe inter-UE relay communication with an additional 5G ProSe layer 3-end UE using an existing 5G ProSe direct link between the 5G ProSe layer 3-end UE and the 5G ProSe layer 3 inter-UE relay UE, the initiating UE shall send a ProSe direct link setup accept message to the source 5G ProSe layer 3-end UE, as specified in clause 7.2.2.3, provided that the initiating UE acts as a 5G ProSe layer 3 inter-UE relay UE.

[0757] Editor's note: Whether to include and how to set the ProSe identifier for the 5G ProSe direct link between the source 5G ProSe layer 3 end UE and the 5G ProSe layer 3 inter-UE relay UE and the 5G ProSe direct link between the 5G ProSe layer 3 inter-UE relay UE and the target 5G ProSe layer 3 end UE is for further study.

[0758] Upon receipt of the ProSe Direct Link Modification Accept message containing a Relay Reselection Indication, if the ProSe Direct Link Modification Request message is for Layer 3 Inter-UE Relay Reselection, the initiating UE shall establish a PC5 unicast link with the selected 5G ProSe Inter-UE Relay UE (if such PC5 unicast link does not already exist), and shall create a ProSe Direct Link Modification Confirm message. In this message, the initiating UE:

[0759] a) shall contain the relay reselection indication, the IP address of the initiating 5G ProSe UE to be used with the newly selected 5G ProSe inter-UE relay UE and the IP address of the target 5G ProSe end UE, if IP communication is used, and if:

[0760] 1) The UE acts as a source 5G ProSe end UE, and the 5G ProSe direct link is between the source 5G ProSe end UE and the 5G ProSe inter-UE relay UE; or

[0761] b) shall contain the relay reselection indication, the IP address of the target 5G ProSe end UE to be used with the newly selected 5G ProSe inter-UE relay UE and the IP address of the source 5G ProSe end UE, if IP communication is used, and if:

[0762] 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.

[0763] After the ProSe direct link modification confirm message is generated, the initiating UE passes this message together with the layer 2 ID of the initiating UE for 5G ProSe direct communication and the layer 2 ID of the target UE for 5G ProSe direct communication to the lower layer for transmission.

[0764] If the source UE confirms 5G ProSe direct link modification acceptance, the source UE starts receiving and / or transmitting traffic via the newly selected 5G ProSe inter-UE relay UE.

[0765] 7.2.3.5 5G ProSe direct link modification procedure not accepted by target UE

[0766] If the 5G ProSe direct link modification request cannot be accepted, the target UE shall send a ProSe direct link modification reject message. The ProSe direct link modification reject message contains the PC5 signaling protocol cause IE set to one of the following cause values:

[0767] #5 Lack of resources for 5G ProSe direct links;

[0768] #6 Required services are not allowed;

[0769] #12 Misalignment with security policy;

[0770] #16 Lack of local capabilities;

[0771] #20 is from the 5G ProSe UE failure;

[0772] #yyThe relay UE is not selected for link establishment with integrated discovery; or

[0773] #111 Unspecified protocol error.

[0774] 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 over PC5 specified in clause 5.2.4, then the target UE shall send a ProSe Direct Link Modification Reject message with PC5 signaling protocol cause value #6 “Required service not allowed”.

[0775] If the 5G ProSe direct link modification fails due to congestion issues or other temporary lower layer issues resulting in resource constraints, the target UE shall send a ProSe Direct Link Modification Reject message with PC5 signaling protocol cause value #5 “Lack of resources for 5G ProSe direct link”.

[0776] If a target UE acting as a target 5G ProSe end UE receives one or more direct link modification requests or direct link establishment requests for end-to-end connection establishment with a source 5G ProSe end UE and uses integrated discovery, the target UE shall select a 5G ProSe inter-UE relay UE and send a ProSe direct link modification reject message with PC5 signaling protocol cause value #yy "Relay UE not selected for link establishment with integrated discovery" to the 5G ProSe inter-UE relay that was not selected and had sent the ProSe direct link modification request message.

[0777] If the Link Modification Operation Code is set to "Associate new ProSe application with 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, the target UE shall send a ProSe Direct Link Modification Reject message with PC5 signaling protocol cause value #12 "Misaligned security policy".

[0778] If the link modification operation requires adding a new PC5 QoS flow, but the target UE is unable to support the additional packet filters that will be required on the existing PDU sessions of the target UE, then the target UE shall send a ProSe Direct Link Modification Reject message with PC5 signaling protocol cause value #16 “Lack of local capability”.

[0779] If the target UE acts as a target 5G ProSe end UE, and the 5G ProSe direct link modification procedure is between the 5G ProSe UE inter-UE relay UE and the target 5G ProSe end UE, then the target 5G ProSe end UE may include in the ProSe direct link modification reject message the source UE information IE set to the user information ID of the source 5G ProSe end UE that has initiated the 5G ProSe direct link establishment procedure.

[0780] 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 side UE and the 5G ProSe inter-UE relay UE, and the target 5G ProSe side 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 shall send a ProSe direct link modification reject message with a PC5 signaling protocol cause value #20 "Failure from 5G ProSe side UE" to the source 5G ProSe side UE. The 5G ProSe inter-UE relay UE may include in the ProSe direct link modification reject message the PC5 side UE failure cause IE set to the PC5 signaling protocol cause received from the target 5G ProSe side UE that has rejected the 5G ProSe direct link establishment procedure, as specified in clause 7.2.2.5. The 5G ProSe inter-UE relay UE may include in the ProSe direct link modification reject message the target UE information IE set to the user information ID of the target 5G ProSe side UE that has rejected the 5G ProSe direct link establishment procedure.

[0781] For other reasons leading to link establishment failure, the target UE shall send a ProSe Direct Link Modification Reject message with PC5 signaling protocol cause value #111 “Unspecified protocol error”.

[0782] After receiving the ProSe Direct Link Modification Reject message, the initiating UE shall stop timer T5081 and abort the 5G ProSe direct link modification procedure. If the PC5 signaling protocol cause value in the ProSe Direct Link Modification Reject message is #11 "Required service not allowed" or #5 "Lack of resources for 5G ProSe direct link" or #12 "Misaligned security policy", the initiating UE shall not attempt to initiate a 5G ProSe direct link modification with the same target UE to add the same ProSe application or to add or modify the same PC5 QoS flow for at least a time period T.

[0783] NOTE: The length of the time period T is UE implementation specific and may be different if the UE receives PC5 signaling protocol cause value #11 "Required service not allowed" or the UE receives PC5 signaling protocol cause value #5 "Lack of resources for 5G ProSe direct link" or the UE receives PC5 signaling protocol cause value #12 "Misaligned security policy". The length of the time period T is not less than 30 minutes.

[0784] 7.2.3.6 Abnormal situations

[0785] 7.2.3.6.1 Abnormal situation at the initiating UE

[0786] The following anomalies can be identified:

[0787] a) If timer T5081 expires, the initiating UE shall retransmit the ProSe direct link modification request message and restart timer T5081. After reaching the maximum number of allowed retransmissions, the initiating UE shall abort the 5G ProSe direct link modification procedure and may notify upper layers that the target UE is unreachable.

[0788] NOTE 1: The maximum number of allowed retransmissions is UE implementation specific.

[0789] NOTE 2: After reaching the maximum number of allowed retransmissions, whether the initiating UE releases this 5G ProSe direct link depends on its implementation.

[0790] b) For the same 5G ProSe direct link, if the initiating UE receives a ProSe direct link release request message after the 5G ProSe direct link modification procedure requested by the initiating UE, the initiating UE shall stop timer T5081, abort the 5G ProSe direct link modification procedure, and continue with the 5G ProSe direct link release procedure.

[0791] 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 shall stop the timer T5081 and abort the 5G ProSe direct link modification procedure. The subsequent processing depends on the implementation, for example, the initiating UE waits for a time depending on the implementation before initiating a new 5G ProSe direct link modification procedure (if still needed).

[0792] NOTE 3: Implementation dependent timer values ​​need to be set to avoid further conflicts (e.g., random timer values).

[0793] 7.2.3.6.2 Abnormal situation at the target UE

[0794] The following anomalies can be identified:

[0795] 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 shall stop all running timers of this 5G ProSe direct link, abort the 5G ProSe direct link modification procedure, and continue with the 5G ProSe direct link release procedure.

[0796] 7.2.3.7 5G ProSe Direct Link Modification Procedure by Target UE Completed

[0797] After receiving the ProSe direct link modification confirmation, the target 5G ProSe end UE starts to receive services, transmit services, or both via the newly selected 5G ProSe inter-UE relay UE.

[0798] […]

[0799] 7.2.10 5G ProSe direct link security mode control procedure

[0800] 7.2.10.1 General

[0801] 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. If the UE PC5 signaling integrity protection is not activated, then security is not established. After successfully completing the 5G ProSe direct link security mode control procedure, the selected security algorithm and its non-null associated key are used to integrity protect and encrypt all PC5 signaling messages exchanged over this 5G ProSe direct link between UEs, and the security context can be used to protect all PC5 user plane data exchanged over this 5G ProSe direct link between UEs. The UE that sends the ProSe direct link security mode command message is called the "initiating UE", and the other UE is called the "target UE".

[0802] 7.2.10.2 5G ProSe direct link security mode control procedure initiated by the initiating UE

[0803] The initiating UE shall meet the following prerequisites before initiating the 5G ProSe direct link security mode control procedure:

[0804] 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:

[0805] 1) ProSe direct link establishment request message:

[0806] i) contains the target user information IE, which contains the application layer ID of the initiating UE; or

[0807] ii) the Target User Information IE is not included, and the initiating UE is interested in the ProSe service identified by the ProSe identifier in the ProSe Direct Link Setup Request message; and

[0808] 2) Initiating UE:

[0809] i) If the direct communication is not between a 5G ProSe remote UE and a 5G ProSe UE to a network relay UE, then based on the K contained in the ProSe direct link establishment request message NRP ID identifies the existing K NRP , or export a new K NRP ;

[0810] ii) 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 user plane are used, then the new K is received according to the security procedures on the user plane specified in 3GPP TS 33.503

[34] . NRP ;

[0811] iii) 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 are used, then the new K is received according to the security procedures on the control plane specified in 3GPP TS 33.503

[34] . NR_ProSe ;or

[0812] iv) has decided not to activate security protection based on its UE 5G ProSe direct signalling security policy and the target UE’s 5G ProSe direct signalling security policy; or

[0813] b) The target UE has initiated the 5G ProSe direct link key update procedure towards the initiating UE by sending a ProSe direct link key update request message along with:

[0814] 1) If the target UE has included a re-authentication indication in the ProSe direct link key update request message, the initiating UE has derived a new K NRP .

[0815] when:

[0816] a) Direct communication is not between 5G ProSe remote UE and 5G ProSe UE to network relay UE. If the new K NRP has been derived by the initiating UE; or

[0817] b) Direct communication between 5G ProSe remote UE and 5G ProSe UE to network relay UE, if a new K is received by the initiating UE 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] ;

[0818] The initiating UE will generate KNRP The 2 MSBs of ID are used to ensure that the resulting K NRP The ID will be unique within the initiating UE.

[0819] NOTE 1: If the direct communication is not between 5G ProSe remote UE and 5G ProSe UE to network relay UE, then K NRP ID remains corresponding to K NRP If the direct communication is between a 5G ProSe remote UE and a 5G ProSe UE to a network relay UE, then K NRP ID remains corresponding to K NRP (if security procedures on the user plane are used) or K NR_ProSe The ID of the control plane security program if you are using it.

[0820] The initiating UE shall select the 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, the initiating UE shall not select the null integrity protection algorithm if the 5G ProSe direct signaling integrity protection policy of either the initiating UE or the target UE is set to "signaling integrity protection required". If the 5G ProSe direct link security mode control procedure is triggered during the 5G ProSe direct link key update procedure, the initiating UE:

[0821] a) If the integrity protection algorithm currently used for the 5G ProSe direct link is different from the null integrity protection algorithm, the null integrity protection algorithm shall not be selected;

[0822] b) if the encryption protection algorithm currently used for the 5G ProSe direct link is different from the null encryption protection algorithm, then the null encryption protection algorithm shall not be selected;

[0823] c) if the currently used integrity protection algorithm is the null integrity protection algorithm, then the null integrity protection algorithm will be selected; and

[0824] d) If the encryption protection algorithm currently in use is the null encryption protection algorithm, then the null encryption protection algorithm will be selected.

[0825] Next, the initiating UE will:

[0826] a) If the direct communication is not between 5G ProSe Remote UE and 5G ProSe UE to Network Relay UE:

[0827] 1) Generate a 128-bit Nonce_2 value;

[0828] 2) Nonce_1 and K received in the ProSe direct link establishment request message NRP and Nonce_2 to derive K NRP-sess , as specified in 3GPP TS 33.536

[37] ; and

[0829] 3) From K NRP-sess and the selected security algorithm to derive the NR PC5 encryption key NRPEK and the NR PC5 integrity key NRPIK as specified in 3GPP TS 33.536

[37] ;

[0830] 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:

[0831] 1) From the K received in 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

[0832] 2) From K relay-sess and the selected security algorithm 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

[0833] c) 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 user plane specified in 3GPP TS 33.503

[34] are used:

[0834] 1) K received from the ProSe Direct Link Setup Request message specified in 3GPP TS 33.503

[34] NRP , K NRP Freshness parameter 2 and K NRP Freshness parameter 1 derives K NRP-sess ;as well as

[0835] 2) From K NRP-sess and the selected security algorithm to derive the NR PC5 encryption key NRPEK and the NR PC5 integrity key NRPIK as specified in 3GPP TS 33.503

[34] ;

[0836] d) Generate a ProSe direct link security mode command message. In this message, the initiating UE:

[0837] 1) The key establishment information container IE shall be included, provided that the 5G ProSe direct link is not used for direct communication between 5G ProSe remote UE and 5G ProSe UE to network relay UE, and a new K has been derived at the initiating UE NRP , and is used to generate K NRP The authentication method requires sending information to complete the 5G ProSe direct link authentication procedure;

[0838] NOTE 2: The key establishment information container is provided by the upper layer.

[0839] 2) Include K NRP MSB of ID IE, if new K has been derived NRP Or a new K has been received at the initiating UE NRP or K NR_ProSe ;

[0840] 3) Will contain Nonce_2IE, which:

[0841] i) When the direct communication is not between a 5G ProSe remote UE and a 5G ProSe UE to a network relay UE, it is set to a 128-bit temporary value generated by the initiating UE;

[0842] ii) When 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 user plane specified in 3GPP TS 33.503

[34] are used, set to the K received by the initiating UE NRP Freshness parameter 2 value; or

[0843] iii) when 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, set to the Nonce_2 value received by the initiating UE;

[0844] for the purpose of establishing session keys on this 5G ProSe direct link if the selected integrity protection algorithm is not the Null Integrity Protection Algorithm;

[0845] 4) will include the selected security algorithm;

[0846] 5) including the UE security capabilities received from the target UE in the ProSe direct link setup request message or the ProSe direct link key update request message;

[0847] 6) including the UE 5G ProSe direct signaling security policy received from the target UE in the ProSe direct link establishment request message;

[0848] 7) If the selected integrity protection algorithm is not the Null Integrity Protection Algorithm, then it shall contain the K selected by the initiating UE as specified in 3GPP TS 33.536

[37] . NRP-sess LSB of ID;

[0849] NOTE 3: If the direct communication is not between 5G ProSe remote UE and 5G ProSe UE to network relay UE, then K NRP-sess ID remains corresponding to K NRP-sess If the direct communication is between a 5G ProSe remote UE and a 5G ProSe UE to a network relay UE, then K NRP-sess ID remains corresponding to K NRP-sess (if security procedures on the user plane are used) or K relay-sess The ID of the control plane security program if you are using it.

[0850] 8) When direct communication is between a 5G ProSe Remote UE and a 5G ProSe UE to Network Relay UE, the GPI shall be included if received from the 5G PKMF according to the security procedures on the user plane specified in 3GPP TS 33.503

[34] ; and

[0851] 9) When direct communication is between a 5G ProSe Remote UE and a 5G ProSe UE to Network Relay UE, an EAP message shall be included if received from the network according to the security procedures on the control plane specified in 3GPP TS 33.503

[34] .

[0852] If the security protection of this 5G ProSe direct link is activated by using a non-null integrity protection algorithm or a non-null ciphering protection algorithm, the initiating UE shall determine the security protection of the 5G ProSe direct link according to the K received in the ProSe direct link setup 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 The LSB of ID forms K NRP-sess ID. The initiating UE will use K NRP-sess The ID identifies the new security context.

[0853] The initiating UE shall set the source Layer 2 ID and the destination Layer 2 ID as follows:

[0854] 1) If the originating UE acts as a 5G ProSe Layer 3 UE to a network relay UE and uses an EAP-AKA' based authentication method as specified in clause 6.3.3.3 of 3GPP TS 33.503

[34] ,

[0855] Setting the source layer 2 ID to the source layer 2 ID used in the ProSe AA message transmission request message, and setting the destination layer 2 ID to the destination layer 2 ID used in the ProSe AA message transmission request message;

[0856] 2) If the initiating UE does not act as a 5G ProSe UE to a network relay UE and a 5G ProSe direct link authentication procedure has been initiated:

[0857] Set the source layer 2 ID to the source layer 2 ID used in the ProSe direct link authentication request message, and set the destination layer 2 ID to the destination layer 2 ID used in the ProSe direct link authentication request message;

[0858] 3) Otherwise, assign a source layer 2 ID by itself, and set the destination layer 2 ID to the source layer 2 ID in the ProSe direct link establishment request message.

[0859] 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 5G ProSe direct discovery as specified in clauses 6.2.14, 6.2.15 and 8.2.1, and is different from any other provided destination Layer 2 ID as specified in clause 5.2.

[0860] NOTE 5: The target UE may reuse the Layer 2 ID that the target UE used in a previous 5G ProSe direct link with the same peer UE.

[0861] After the ProSe Direct Link Security Mode Command message is generated, the initiating UE passes this message to the lower layers for transmission along with the source layer 2 ID and the destination layer 2 ID, NRPI K (or K relay-Int , where applicable), NRPEK (or K relay-enc , where applicable) (if applicable), K NRP-sess The initiating UE shall send a new ProSe direct link security mode command message to the same target UE while the timer T5089 is running.

[0862] NOTE 6: The ProSe Direct Link Security Mode Command message is integrity protected (and not encrypted) using a new security context at the lower layers.

[0863] If the 5G ProSe direct link security mode control procedure is triggered during the 5G ProSe direct link key update procedure, the initiating UE provides an activation indication of 5G ProSe direct user plane security protection for the 5G ProSe direct link with a new security context (if applicable) to the lower layers together with the Layer 2 ID of the initiating UE for 5G ProSe direct communication and the Layer 2 ID of the target UE for 5G ProSe direct communication.

[0864] [3GPP TS24.554 V18.1.0 titled "5G ProSe direct link security mode control procedures" Figure 7 .2.10.2.1 is reproduced as Fig.17 ]

[0865] 7.2.10.3 5G ProSe direct link security mode control procedure accepted by target UE

[0866] Upon receiving the ProSe direct link security mode command message, if the newly assigned layer 2 ID of the initiating UE is included and if the 5G ProSe direct link authentication procedure has not been performed, the target UE shall replace the layer 2 ID of the original initiating UE with the newly assigned layer 2 ID of the initiating UE for 5G ProSe direct communication. The target UE shall check the selected security algorithm IE contained in the ProSe direct link security mode command message. If the selected security algorithm IE contains "null integrity algorithm", no integrity protection is provided for this 5G ProSe direct link and the signaling message is transmitted unprotected. If "null encryption algorithm" and integrity algorithms other than "null integrity algorithm" are included in the selected algorithm IE, no encryption protection is provided for this 5G ProSe direct link and the signaling message is transmitted unprotected. If the 5G ProSe direct signaling integrity protection policy of the target UE is set to "signaling integrity protection required", the target UE shall verify that the selected security algorithm IE in the ProSe direct link security mode command message does not contain a null integrity protection algorithm. If the selected integrity protection algorithm is not a null integrity protection algorithm, the target UE shall:

[0867] a) If the direct communication is not between 5G ProSe Remote UE and 5G ProSe UE to Network Relay UE:

[0868] 1) From the K received in the ProSe Direct Link Security Mode Command message NRP, Nonce_1 and Nonce_2 derive K NRP-sess , as specified in 3GPP TS 33.536

[37] ;

[0869] 2) From K NRP-sess and the selected integrity algorithm to derive the NRPIK as specified in 3GPP TS 33.536

[37] ; and

[0870] 3) If K is derived NRP-sess If the selected encryption protection algorithm is not a null encryption protection algorithm, the target UE will NRP-sess and the selected encryption algorithm to derive the NRPEK as specified in 3GPP TS 33.536

[37] ; or

[0871] b) If direct communication is between 5G ProSe Remote UE and 5G ProSe UE to Network Relay UE:

[0872] 1) If the control plane security procedures specified in 3GPP TS 33.503

[34] are used, K is derived according to the control plane security procedures. relay-sess , and from K relay-sess and the selected integrity algorithm to derive K relay-int , as specified in 3GPP TS 33.503

[34] . If K relay-sess If the encryption protection algorithm is not the null encryption protection algorithm, the target UE will relay-sess and the selected encryption algorithm to derive K relay-enc , as specified in 3GPP TS 33.503

[34] ; or

[0873] 2) If the user plane security procedures specified in 3GPP TS 33.503

[34] are used, K is derived according to the user plane security procedures. NRP-sess , and from K NRP-sess and the selected integrity algorithm to derive the NRPIK, as specified in 3GPP TS 33.503

[34] . NRP-sess If the encryption protection algorithm is not the null encryption protection algorithm, the target UE will NRP-sess and the selected encryption algorithm to derive the NRPEK, as specified in 3GPP TS 33.503

[34] .

[0874] The target UE shall determine whether the ProSe direct link security mode command message can be accepted by performing the following operations:

[0875] a) If the 5G ProSe direct signaling integrity protection policy of the target UE is set to “signaling integrity protection required”, verify that the Selected Security Algorithm IE in the ProSe Direct Link Security Mode Command message does not contain a null integrity protection algorithm;

[0876] b) If the selected integrity protection algorithm is not the null integrity protection algorithm, the lower layer is required to use NRPIK (or K relay-int , when applicable) and the selected integrity protection algorithm to verify the integrity of the ProSe direct link security mode command message;

[0877] c) verifying 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 Setup Request message or the ProSe Direct Link Key Update Request message;

[0878] d) If the 5G ProSe direct link security mode control procedure is triggered during the 5G ProSe direct link establishment procedure,

[0879] 1) checking that the received UE 5G ProSe direct signalling security policy has not been changed compared to the value sent by the target UE to the initiating UE in the ProSe Direct Link Setup Request message; and

[0880] 2) Check the K contained in the ProSe direct link security mode command message NRP-sess the LSBs of the ID are not set to the same values ​​as those received from another UE in response to the target UE's ProSe direct link setup request message; and

[0881] 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 verify that the selected security algorithm IE in the ProSe direct link security mode command message does not include the null integrity protection algorithm.

[0882] If the target UE does not include K in the ProSe direct link establishment request message NRP ID, the target UE includes a re-authentication indication in the ProSe Direct Link Key Update Request message or the initiating UE has chosen to derive:

[0883] 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 derive K NRP , as specified in 3GPP TS 33.536

[37] ;

[0884] b) New K NRP , 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 user plane specified in 3GPP TS 33.503

[34] are used, then the target UE shall derive K NRP , as specified in 3GPP TS 33.536

[37] ; or

[0885] c) New K NR_ProSe , 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, then the target UE shall derive K NR_ProSe , as specified in 3GPP TS 33.536

[37] ; and

[0886] The target UE should select K NRP The 2 LSBs of ID ensure that the resulting K NRP The ID will be unique in the target UE. The target UE shall NRP The MSB of ID and its selected K NRP The 2 LSBs of ID form K NRP ID, and should be the same as K NRP / K NR_ProSe Store the complete K together NRP ID.

[0887] NOTE 1: If the direct communication is not between 5G ProSe remote UE and 5G ProSe UE to network relay UE, then K NRP ID remains corresponding to K NRP If the direct communication is between a 5G ProSe remote UE and a 5G ProSe UE to a network relay UE, then K NRP ID remains corresponding to K NRP (if security procedures on the user plane are used) or K NR_ProSe The ID of the control plane security program if you are using it.

[0888] If GPI is included in the ProSe Direct Link Security Mode Command message and the direct communication is between a 5G ProSe Remote UE and a 5G ProSe UE to a Network Relay UE, then according to the security procedures on the user plane specified in 3GPP TS 33.503

[34] , the target UE shall derive the UP-PRUK from the GPI and obtain the UP-PRUK ID, and use the UP-PRUK to derive the K NRP.

[0889] If the target UE accepts the ProSe Direct Link Security Mode Command message, the target UE shall generate a ProSe Direct Link Security Mode Complete message. In this message, the target UE:

[0890] a) If the 5G ProSe direct link security mode control procedure is triggered during the 5G ProSe direct link establishment procedure:

[0891] 1) If the 5G ProSe direct link is not used for 5G ProSe direct communication between 5G ProSe remote UE and 5G ProSe UE to network relay UE, then PQFI and corresponding PC5 QoS parameters shall be included; or

[0892] 2) If the 5G ProSe direct link is used for 5G ProSe direct communication between a 5G ProSe layer 3 remote UE and a 5G ProSe layer 3 UE to a network relay UE, then the PQFI and corresponding PC5 QoS parameters may be included;

[0893] NOTE 2: If the 5G ProSe direct link is used for 5G ProSe direct communication between a 5G ProSe Layer 2 remote UE and a 5G ProSe Layer 2 UE to a network relay UE, the PQFI and the corresponding PC5 QoS parameters are not included.

[0894] 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 IP Address Configuration IE set to one of the following values ​​shall be included:

[0895] 1) "IPv6 router", if only the IPv6 address allocation mechanism is supported by the target UE, i.e. acting as an IPv6 router;

[0896] 2) "DHCPv4 server", if only IPv4 address allocation mechanism is supported by the target UE, i.e. acting as a DHCPv4 server;

[0897] 3) "DHCPv4 server and IPv6 router", if both IPv4 and IPv6 address allocation mechanisms are supported by the target UE; or

[0898] 4 ") Address allocation is not supported", if both IPv4 and IPv6 address allocation mechanisms are not supported by the target UE;

[0899] NOTE 3: If Ethernet or Unstructured Data Unit Type is used for communication, then the UE does not include the IP Address Configuration IE nor the Link-Local IPv6 Address IE.

[0900] 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] shall be included;

[0901] d) If the new K is derived NRP Or receive a new K NRP or K NR_ProSe , then it will contain K NRP The 2 LSBs of the ID; and

[0902] e) If the 5G ProSe direct link security mode control procedure is triggered during the 5G ProSe direct link establishment procedure, then its UE 5G ProSe direct user plane security policy for this 5G ProSe direct link shall be included. In case 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 Setup Request message, each of the user plane security policies of those ProSe services shall be compatible, e.g., "user plane integrity protection not required" and "user plane integrity protection required" are not compatible.

[0903] If the selected integrity protection algorithm is not the Null Integrity Protection Algorithm, the target UE will receive the K sent in the ProSe Direct Link Setup 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 The LSB of ID forms K NRP-sess ID. The target UE will use K NRP-sess ID to identify the new security context.

[0904] After the ProSe direct link security mode complete message is generated, the target UE passes this message to the lower layer for transmission together with the following: the layer 2 ID of the target UE for 5G ProSe direct communication and the layer 2 ID of the initiating UE for 5G ProSe direct communication, the NRPIK (or K relay-int , where applicable), NRPEK (or K relay-enc , where applicable) (if 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 the 5G ProSe direct link with the new security context (if applicable).

[0905] NOTE 4: The ProSe Direct Link Security Mode Complete message and other 5G ProSe direct signaling messages are integrity protected and encrypted (if applicable) using a new security context at the lower layers.

[0906] If the 5G ProSe direct link security mode control procedure is triggered during the 5G ProSe direct link key update procedure, the target UE provides an activation indication of 5G ProSe direct user plane security protection for the 5G ProSe direct link with a new security context (if applicable) to the lower layers together with the Layer 2 ID of the initiating UE for 5G ProSe direct communication and the Layer 2 ID of the target UE for 5G ProSe direct communication.

[0907] 7.2.10.4 Completion of 5G ProSe direct link security mode control procedure by the initiating UE

[0908] After receiving the ProSe Direct Link Security Mode Complete message, the initiating UE shall stop timer T5089. If the selected integrity protection algorithm is not a null integrity protection algorithm, the UE checks the integrity of the ProSe Direct Link Security Mode Complete message. If the integrity check passes, the initiating UE shall then continue with the procedure of triggering the 5G ProSe Direct Link Security Mode Control procedure. If the selected integrity protection algorithm is a null integrity protection algorithm, the UE continues with the procedure without checking integrity protection.

[0909] After receiving the ProSe Direct Link Security Mode Complete message, the initiating UE shall delete the old security context it has for the target UE (if any).

[0910] 7.2.10.5 5G ProSe direct link security mode control procedure not accepted by target UE

[0911] If the ProSe direct link security mode command message cannot be accepted, the target UE shall send a ProSe direct link security mode reject message, and the target UE shall abort the ongoing procedure that triggered the initiation of the 5G ProSe direct link security 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 security mode reject message contains the PC5 signaling protocol cause IE, which indicates one of the following cause values:

[0912] #5: Lack of resources for 5G ProSe direct links;

[0913] #7: Integrity failure;

[0914] #8: UE security capability mismatch;

[0915] #9: K NRP-sess LSB conflict of ID;

[0916] #10: UE PC5 unicast signaling security policy mismatch;

[0917] #14: Authentication synchronization error; or

[0918] #111: Unspecified protocol error.

[0919] If this 5G ProSe direct link security mode control procedure is triggered during the 5G ProSe direct link establishment procedure and the implementation-specific maximum number of established NR 5G ProSe direct links has been reached, the target UE shall send a ProSe Direct Link Security Mode Reject message with PC5 signaling protocol cause value #5 “Lack of resources for 5G ProSe direct link”.

[0920] 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, the Selected Security Algorithm IE in the ProSe direct link security mode command message contains a null integrity protection algorithm, and the 5G ProSe direct signaling integrity protection policy of the target UE is set to "Signaling integrity protection required", then the target UE shall include PC5 signaling protocol cause #10 "UE PC5 unicast signaling security policy mismatch" in the ProSe direct link security mode reject message.

[0921] 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 null integrity protection algorithm, and the Selected Security Algorithm IE in the ProSe direct link security mode command message contains the null integrity protection algorithm, then the target UE shall include PC5 signaling protocol cause #10 "UE PC5 unicast signaling security policy mismatch" in the ProSe direct link security mode reject message.

[0922] 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 Setup Request message or the ProSe Direct Link Key Update Request message, the target UE shall include PC5 signaling protocol cause #8 “UE security capabilities mismatch” in the ProSe Direct Link Security Mode Reject message.

[0923] If the target UE detects that the K NRP-sess If the LSBs of the ID are set to the same value as those received from another UE in response to the target UE's ProSe direct link setup request message, then the target UE shall include PC5 signaling protocol cause #9 "K NRP-sess LSB of ID conflicts".

[0924] If the 5G ProSe Direct Link Security Mode Control procedure is 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 in processing the authentication vector (if any) contained in the GPI sent by the 5G ProSe UE to Network Relay UE to the 5G ProSe Remote UE, then the target UE shall include PC5 signaling protocol cause #14 "Authentication synchronization error" in the ProSe Direct Link Security Mode Reject message and shall include the RAND and AUTS parameters in the ProSe Direct Link Security Mode Reject message.

[0925] After generating the ProSe direct link security mode reject message, the target UE passes this message together with the Layer 2 ID of the initiating UE for 5G ProSe direct communication and the Layer 2 ID of the target UE for 5G ProSe direct communication to the lower layer for transmission.

[0926] After receiving the ProSe Direct Link Security Mode Reject message, the initiating UE shall stop timer T5089 and provide an indication to the lower layers to deactivate 5G ProSe direct security protection and delete the security context for the 5G ProSe direct link (if applicable):

[0927] a) If the PC5 signaling protocol cause IE in the ProSe Direct Link Security Mode Reject message is set to #9 "K NRP-sess If the LSB of the ID conflicts, retransmit K NRP-sess The ProSe direct link security mode command message has a different value for the LSB of the ID and restarts the timer T5089;

[0928] b) if the PC5 Signalling Protocol Cause IE in the ProSe Direct Link Security Mode Reject 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 for direct communication between a 5G ProSe Remote UE and a 5G ProSe UE to Network Relay UE, then a fresh GPI may be extracted from the PKMF by sending a Key Request message containing RAND and AUTS, as specified in 3GPP TS 33.503

[34] ; or

[0929] c) If the PC5 signaling protocol reason IE is set to anything other than #9 "K NRP-sess If the value is other than "LSB collision of ID" and other than #14 "Authentication synchronization error", the ongoing procedure that triggered the initiation of the 5G ProSe direct link security mode control procedure is aborted.

[0930] 7.2.10.6 Abnormal situations

[0931] 7.2.10.6.1 Abnormal situation at the initiating UE

[0932] a) Timer T5089 expires.

[0933] The initiating UE shall retransmit the ProSe Direct Link Security Mode Command message and restart the timer T5089. After reaching the maximum number of allowed retransmissions, the initiating UE shall abort the 5G ProSe Direct Link Security Mode Control procedure, provide an indication to the lower layers to deactivate the 5G ProSe direct security protection and delete the security context for the 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.

[0934] NOTE 1: The maximum number of allowed retransmissions is UE implementation specific.

[0935] b) This 5G ProSe direct link does not need to be used any more before completing the 5G ProSe direct link security mode control procedure.

[0936] The initiating UE shall abort the procedure, shall provide an indication to the lower layers to deactivate 5G ProSe direct security protection and delete the security context for the 5G ProSe direct link (if applicable), and shall abort the ongoing procedure that triggered the initiation of the 5G ProSe direct link security mode control procedure.

[0937] c) If the ProSe direct link modification request message or the ProSe direct link identifier update request message is received while the timer T5089 is running, the initiating UE shall discard the ProSe direct link modification request message or the ProSe direct link identifier update request message.

[0938] 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 shall stop timer T5089, abort the 5G ProSe direct link security mode control procedure, and continue with the 5G ProSe direct link release procedure.

[0939] NOTE 2: The exception cases described in item number c) or d) only occur 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.

[0940] […]

[0941] 10.3.1 ProSe Direct Link Establishment Request

[0942] 10.3.1.1 Message Definition

[0943] This message is sent by a UE to another peer UE to establish a direct link. See Table 10.3.1.1.1.

[0944] Message type: ProSe direct link establishment request

[0945] Significance: Dual

[0946] Direction: UE to peer UE

[0947] [Table 10.3.1.1.1 entitled "ProSe direct link setup request message contents" of 3GPP TS 24.554 V18.1.0 is reproduced as Fig.18 ]

[0948] Editor's note: Security parameters for 5G ProSe inter-UE relay and parameters for 5G ProSe layer 2 inter-UE relay are for further study.

[0949] 10.3.1.2 Target User Information

[0950] The UE shall include this IE if the Application Layer ID of the target UE is received from upper layers or is known based on the unicast Layer 2 ID of the target UE (i.e., destination Layer 2 ID), as described in clause 5.8.2.4 of 3GPP TS 23.304 [3], or if the UE receives the 5G ProSe UE to Network Relay UE User Information ID during the 5G ProSe UE to Network Relay Discovery procedure, or if the following conditions exist:

[0951] 1) The UE acts as a source 5G ProSe UE and the user information ID of the target 5G ProSe UE is obtained during the 5G ProSe inter-UE relay discovery procedure; or

[0952] 2) The 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 from the source 5G ProSe end UE.

[0953] […]

[0954] 10.3.1.7 Relay Service Code

[0955] If the 5G ProSe direct link establishment procedure is used for direct communication between a 5G ProSe remote UE and a 5G ProSe UE to network relay UE or between a 5G ProSe end UE and a 5G ProSe inter-UE relay UE, the UE shall include this IE.

[0956] 10.3.1.8 ProSe Identifier

[0957] If the 5G ProSe direct link establishment procedure is not for 5G ProSe direct communication between a 5G ProSe remote UE and a 5G ProSe UE to a network relay UE, the UE shall include this IE.

[0958] 10.3.1.9UE Identity

[0959] 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, the UE shall include this IE.

[0960] […]

[0961] 10.3.1.14 Relaying UE User Information Between UEs

[0962] The UE shall include this IE in the following cases:

[0963] 1) The user information ID of the 5G ProSe inter-UE relay UE is obtained during the 5G ProSe inter-UE relay discovery procedure, and the 5G ProSe direct link establishment procedure is used for 5G ProSe direct communication between the source 5G ProSe end UE and the 5G ProSe inter-UE relay UE; or

[0964] 2) The UE acts as a 5G ProSe inter-UE relay UE.

[0965] 10.3.1.15 Target UE Layer 2 ID

[0966] If the target UE Layer 2 ID is available to the source 5G ProSe UE via previous direct communication, and the 5G ProSe direct link establishment procedure is for 5G ProSe direct communication between the source 5G ProSe UE and a 5G ProSe inter-UE relay UE, the UE should include this IE.

[0967] 10.3.2 ProSe Direct Link Establishment Acceptance

[0968] 10.3.2.1 Message Definition

[0969] This message is sent by a UE to another peer UE to accept the received ProSe Direct Link Setup Request message. See Table 10.3.2.1.1.

[0970] Message Type: ProSe Direct Link Establishment Accept

[0971] Significance: Dual

[0972] Direction: UE to peer UE

[0973] [Table 10.3.2.1.1 entitled "ProSe Direct Link Setup Accept Message Contents" of 3GPP TS 24.554 V18.1.0 is reproduced as Fig.19 ]

[0974] Editor's note: Security parameters for 5G ProSe inter-UE relay and parameters for 5G ProSe layer 2 inter-UE relay are for further study.

[0975] 10.3.2.2 IP address configuration

[0976] If IP communication is used, the UE should include this IE.

[0977] 10.3.2.3 Target Link-Local IPv6 Address

[0978] The UE shall include this IE if IP communication is used and the IP address configuration is set to "Address allocation not supported".

[0979] […]

[0980] 10.3.2.6 Relaying UE User Information Between UEs

[0981] If the 5G ProSe direct link establishment procedure is used for 5G ProSe direct communication between a (source or target) 5G ProSe end UE and a 5G ProSe inter-UE relay UE, the UE shall include this IE.

[0982] […]

[0983] 3GPP TS23.304 describes support for inter-UE relay. In general, a relay UE may be used to support communication between two (layer 2 or layer 3) proximity-based service (ProSe) end UEs when the two UEs are unable to communicate directly with each other. An inter-UE relay UE establishes a PC5 link with each of two ProSe end UEs including a source ProSe end UE (e.g., on a first PC5 hop) and a target ProSe end UE (e.g., on a second PC5 hop) for forwarding traffic of the ProSe service of interest between the two ProSe end UEs. If a source 5G ProSe end UE wishes to communicate with multiple target 5G ProSe end UEs, the (1st hop) PC5 link between the source 5G ProSe layer 3 end UE and the 5G ProSe inter-UE relay UE may be shared for the multiple target 5G ProSe end UEs, while the (2nd hop) PC5 link may be established separately between the 5G ProSe inter-UE relay UE and the target 5G ProSe end UE.

[0984] To establish a PC5 link, a Layer 2 link establishment procedure without discovery integration as specified in clause 6.7.1 of 3GPP TS 23.304 or a Layer 2 link establishment procedure with discovery integration as specified in clause 6.7.3 of 3GPP TS 23.304 may be used (i.e., the former may be used if the Layer 2 link establishment procedure is initiated toward a relay UE or the source UE has selected a specific relay UE, and the latter may be used if the Layer 2 link establishment procedure is initiated toward any relay UE or the source UE has not yet discovered any relay UE). For a shared PC5 link, a Layer 2 link modification procedure should be used. According to 3GPP TS 23.304, a PC5 link may be associated with a relay service code and may support one or more services identified by one or more ProSe identifiers.

[0985] Clause 6.4.3.7.4 of 3GPP TS23.304 states that the user information ID of the target 5G ProSe end UE may be optionally included in the first-hop direct communication request (DCR) message as well as the second-hop DCR message. This implies that the service-oriented link establishment procedure introduced in clause 6.4.3.1 of 3GPP TS23.304 may also be supported for inter-UE relay communication. The source end UE may send a first-hop DCR message that does not contain any user information of the target 5G ProSe end UE to the relay UE. In response to receiving the first-hop DCR message, the relay UE may send a second-hop DCR message that also does not contain any user information of the target 5G ProSe end UE. Both the first-hop DCR message and the second-hop DCR message may contain a relay service code for identifying a connectivity service. It is possible that more than one target 5G ProSe end UE may receive a second-hop DCR message from the relay UE, and these target 5G ProSe end UEs may be interested in the connectivity service or they may match the relay service code. In this case, each of these target 5G ProSe end UEs may continue the corresponding link establishment procedure with the relay UE to establish respective 2nd hop PC5 links between the relay UE and each target 5G ProSe end UE. For example, there are a first target end UE and a second target end UE and they receive a 2nd hop DCR message from the relay UE. The first target end UE may then establish a first 2nd hop PC5 link with the relay UE, and the second target end UE may then also establish a second 2nd hop PC5 link with the relay UE. The first target end UE may send a first 2nd hop direct communication accept (DCA) message to the relay UE to complete the establishment of the first 2nd hop PC5 link. The second target end UE may send a second 2nd hop DCA message to the relay UE to complete the establishment of the second 2nd hop PC5 link. Thereafter, the relay UE may respond to the 1st hop DCA message to the source end UE.

[0986] According to 3GPP TS24.554, if the 5G ProSe direct link establishment procedure is for 5G ProSe direct communication between a 5G ProSe end UE and a 5G ProSe UE-to-end relay UE, the source user information contained in the ProSe direct link establishment accept message (i.e., direct communication accept message) is set to the user information ID of the target 5G ProSe end UE. Generally, the relay UE may send a 1-hop DCA message containing only one user information of the first target end UE or the second target end UE, because such source user information IE of the ProSe direct link establishment accept message is specified to indicate only one user information ID or one application layer ID. For example, the 1-hop DCA message may contain the user information of the first target end UE. Since the second target end UE also participates in the U2U relay communication with the source end UE via the relay UE, the relay UE may additionally initiate, for example, a link modification procedure with the source end UE to modify the 1-hop PC5 link for adding the second target end UE.

[0987] In addition, item number h) in clause 7.2.2.3 of 3GPP TS24.554 is specified for the relay UE to include the target 5G ProSe layer 3 end UE IP address IE set to the IP address of the target 5G ProSe layer 3 end UE in the ProSe direct link establishment accept message, provided that the 5G ProSe direct link establishment procedure is for 5G ProSe direct communication between the source 5G ProSe layer 3 end UE and the 5G ProSe layer 3 UE inter-relay UE, and the data unit type used for communication is IP. Similarly, following the above example, the relay UE may also include the IP address of the first target end UE in the 1st hop DCA message. The relay UE may need to initiate a link modification procedure with the source UE to modify the 1st hop PC5 link to add the second target end UE together with the IP address of the second target end UE. The concept can be found in Fig. 20A Shown in.

[0988] Alternatively, Fig. 20B It can be shown that the first target UE can send a first 2nd hop DCA message to the relay UE to complete the establishment of the first 2nd hop PC5 link. In response to receiving the first 2nd hop DCA message, the relay UE can respond to the source UE with a 1st hop DCA message. The relay UE can also receive a second 2nd hop DCA message from the second target UE to complete the establishment of the second 2nd hop PC5 link. Since the second target UE also participates in the U2U relay communication with the source UE via the relay UE, the relay UE can additionally initiate, for example, a link modification procedure with the source UE to modify the 1st hop PC5 link for adding the second target UE.

[0989] In terms of latency and signaling overhead reduction, it would be beneficial if the relay UE indicated / included user information of the second target UE in addition to the user information of the first target UE in the 1-hop DCA message, and thus the source UE could understand by receiving the 1-hop DCA message that the 1-hop PC5 link was established to communicate with both the first target UE and the second target UE via the relay UE. The relay UE could also include the IP address of the first target UE and the IP address of the second target UE for communication with the source UE in the 1-hop DCA message.

[0990] Therefore, the source user information IE in the ProSe direct link setup accept message may be further specified and thus contain one or more application layer IDs or user information IDs of the target 5G ProSe end UE. Alternatively, a new IE in the ProSe direct link setup accept message (which is different from the existing source user information IE) may be specified for the case of U2U relay communication and thus contain one or more application layer IDs or user information IDs of the target 5G ProSe end UE.

[0991] It is also possible that the ProSe direct link setup accept message may be further specified to include one or more application layer IDs or user information IDs of the target 5G ProSe end UE. The existing source user information IE may be set to the one or more application layer IDs or user information IDs of the target 5G ProSe end UE. Alternatively, a new IE in the ProSe direct link setup accept message (which is different from the existing source user information IE) may be specified and set to the one or more application layer IDs or user information IDs of the target 5G ProSe end UE. In this way, the existing source user information IE may be set to, for example, zero "0". The source UE may ignore the existing source user information IE in the 1st hop DCA message. Alternatively, the existing source user information IE may be set to one of the one or more application layer IDs or user information IDs of the target 5G ProSe end UE, and the new IE may be set to the remaining part of the one or more application layer IDs or user information IDs of the target 5G ProSe end UE. For example, the existing source user information IE may be set to the application layer ID or user information ID of the first target UE, and the new IE may be set to the application layer ID or user information ID of the second target UE.

[0992] In addition, the target 5G ProSe layer 3 end UE IP address IE or similar purpose IE in the ProSe direct link establishment accept message can be specified to include one or more IP addresses of the target 5G ProSe end UE.

[0993] Can be Fig.21 The above solution is shown in .

[0994] More specifically, the PC5 link may be a PC5 connection, a unicast link, a direct link, a layer 2 link, and the like.

[0995] More specifically, the source UE may be a source 5G ProSe UE.

[0996] More specifically, the target UE may be a target 5G ProSe UE.

[0997] More specifically, the relay UE may be a 5G ProSe inter-UE relay UE.

[0998] More specifically, the user information may be a user information ID, an application layer ID, or an upper layer ID.

[0999] More specifically, the 1st hop DCR message may be sent by using the source layer 2 ID of the source UE and the destination layer 2 ID. The destination layer 2 ID may be a broadcast layer 2 ID associated with a relay service code or connectivity service, or may be used for a link establishment procedure integrated with discovery.

[1000] More specifically, the 2nd hop DCR message may be sent by using the source layer 2 ID and the destination layer 2 ID of the relay UE. The destination layer 2 ID may be a broadcast layer 2 ID associated with a relay service code or connectivity service, or may be used for a link establishment procedure integrated with discovery.

[1001] More specifically, the first 2nd hop DCA message may be sent by using the layer 2 ID of the first target UE as a source and using the layer 2 ID of the relay UE as a destination.

[1002] More specifically, the second 2nd hop DCA message may be sent by using the layer 2 ID of the second target UE as a source and using the layer 2 ID of the relay UE as a destination.

[1003] More specifically, the 1st-hop DCA message may be sent by using the layer 2 ID of the relay UE as a source and using the layer 2 ID of the source UE as a destination.

[1004] Fig.232300 is a flow chart of a method for a relay UE. In step 2305, the relay UE receives a first message from a source UE, wherein the first message will establish a 1-hop PC5 connection with the relay UE for communication with any target UE. In step 2310, the relay UE establishes at least a first 2-hop PC5 connection with a first target UE and a second 2-hop PC5 connection with a second target UE for communication with the source UE. In step 2315, the relay UE sends a second message to the source UE, wherein the second message will complete the establishment of the 1-hop PC5 connection and contain user information of the first target UE and user information of the second target UE.

[1005] In one embodiment, the relay UE may send a third message in response to receiving the first message, wherein the third message will establish a 2nd hop PC5 connection with any target UE for communication with the source UE. The relay UE may receive a fourth message from the first target UE, wherein the fourth message will complete the establishment of the first 2nd hop PC5 connection with the relay UE for communication with the source UE. The relay UE may receive a fifth message from the second target UE, wherein the fifth message will complete the establishment of the second 2nd hop PC5 connection with the relay UE for communication with the source UE.

[1006] In one embodiment, the first message may include user information of the source UE, user information of the relay UE, a relay service code, etc., and does not include user information of any target UE. The second message may include user information of the source UE, user information of the relay UE, a relay service code, an IP address of the first target UE, an IP address of the second target UE, etc. The third message may include user information of the source UE, user information of the relay UE, a relay service code, etc., and does not include user information of any target UE. The fourth message may include user information of the source UE, user information of the relay UE, a relay service code, user information of the first target UE, etc. The fifth message may include user information of the source UE, user information of the relay UE, a relay service code, user information of the second target UE, etc.

[1007] In one embodiment, the first / third message may be a direct communication request message or a ProSe direct link setup request message. The second / fourth / fifth message may be a direct communication accept message or a ProSe direct link setup accept message.

[1008] In one embodiment, the user information may be a user information ID or an application layer ID.

[1009] Return to reference Figure 3 and 4In an exemplary embodiment from the perspective of the relay UE, the relay UE 300 includes a program code 312 stored in the memory 310. The CPU 308 can execute the program code 312 to enable the relay UE to: (i) receive a first message from the source UE, wherein the first message will establish a 1st hop PC5 connection with the relay UE for communication with any target UE, (ii) establish at least a first 2nd hop PC5 connection with the first target UE and a second 2nd hop PC5 connection with the second target UE for communication with the source UE, and (iii) send a second message to the source UE, wherein the second message will complete the establishment of the 1st hop PC5 connection and contain the user information of the first target UE and the user information of the second target UE. In addition, the CPU 308 can execute the program code 312 to perform all of the above actions and steps or other actions and steps described herein.

[1010] Alternatively, given a discovery-integrated link establishment procedure initiated by a source UE, the relay UE may be limited to accepting one target UE for this source UE. If the relay UE may first (start) perform a first security context establishment with a first target UE, the relay UE may not (additionally) perform a second security context establishment with a second target UE. For example, in the first security context establishment, the relay UE may receive a first security mode command message from the first target UE for establishing a first security context for a first 2nd hop PC5 link. The relay UE may then send a first security mode completion message to the first target UE for completing the first security context establishment. In the second security context establishment, the relay UE may receive a second security mode command message from the second target UE for establishing a second security context for a second 2nd hop PC5 link. Since the relay UE has received / accepted the first security mode command message, the relay UE may respond to the second target UE with a rejection message corresponding to the second security mode command message. Instead of sending a rejection message, the relay UE may (only) discard / ignore the second security mode command message received from the second target UE. This concept may be described in detail in the following examples. Fig. 22 Shown in.

[1011] It is also feasible that the relay UE makes a decision to perform the first security context establishment or the second security context establishment after receiving the first security mode command message and the second security mode command message. The decision can be made based on, for example, channel quality, etc. For example, based on the reception of the first security mode command message, the relay UE can measure the channel quality between the relay UE and the first target end UE; and based on the reception of the second security mode command message, the relay UE can measure the channel quality between the relay UE and the second target end UE. If the channel quality between the relay UE and the first target end UE is better than the channel quality between the relay UE and the second target end UE, the relay UE can then perform the first security context establishment with the first target end UE (and reject / ignore the second security context establishment with the second target end UE). Otherwise (that is, if the channel quality between the relay UE and the second target end UE is better), the relay UE can then perform the second security context establishment with the second target end UE (and reject / ignore the first security context establishment with the first target end UE).

[1012] An example of a textual proposal based on 3GPP TS24.554 is provided below. It should be noted that "ongoing 5G ProSe direct link security mode control procedure" may mean that from the perspective of the target UE of the security mode control procedure, the target UE may consider that the security mode control procedure is still in progress until a DCA message is received from the initiating UE of the security mode control procedure.

[1013]

[1014]

[1015] Another example of a textual proposal based on 3GPP TS24.554 is provided below. It should be noted that in the following textual proposal, "yyy" may be replaced by an integer, and "searching for target 5G ProSe end UE" may be replaced by another wording such as "target UE does not continue the procedure". It may also be feasible to reuse existing cause values, such as #5 or #111 in a rejection message.

[1016]

[1017]

[1018] Fig.242400 is a flowchart of a method for a relay UE. In step 2405, the relay UE receives a first message from a source UE, wherein the first message will establish a 1st hop PC5 connection with the relay UE for communication with any target UE. In step 2410, the relay UE sends a second message, wherein the second message will establish a 2nd hop PC5 connection with any target UE for communication with the source UE. In step 2415, the relay UE receives a third message from the first target UE for establishing a first security context for the 2nd hop PC5 connection. In step 2420, the relay UE receives a fourth message from the second target UE for establishing a second security context for the 2nd hop PC5 connection. In step 2425, the relay UE discards the fourth message in response to acceptance of the third message or sends a rejection message corresponding to the fourth message to the second target UE.

[1019] In one embodiment, the relay UE may send a fifth message corresponding to the third message to the first target UE, wherein the fifth message completes the establishment of the first security context. The relay UE may receive a sixth message from the first target UE to complete the establishment of the second hop PC5 connection. The relay UE may send a seventh message to the source UE to complete the establishment of the first hop PC5 connection.

[1020] In one embodiment, the first message may include at least one of the user information of the source UE, the user information of the relay UE, the relay service code, etc., and does not include any user information of the target UE. The second message may include at least one of the user information of the source UE, the user information of the relay UE, the relay service code, etc., and does not include any user information of the target UE. The sixth message may include at least the user information of the first target UE. The seventh message may include at least the user information of the first target UE.

[1021] In one embodiment, the first / second message may be a direct communication request message or a ProSe direct link setup request message. The sixth / seventh message may be a direct communication acceptance message or a ProSe direct link setup acceptance message. The third / fourth message may be a security mode command message or a ProSe direct link security mode command message. The fifth message may be a security mode completion message or a ProSe direct link security mode completion message.

[1022] In one embodiment, the rejection message may be a security mode rejection message or a ProSe direct link security mode rejection message. In one embodiment, the user information may be a user information ID or an application layer ID.

[1023] Return to reference Figure 3 and 4In an exemplary embodiment from the perspective of the relay UE, the relay UE 300 includes a program code 312 stored in the memory 310. The CPU 308 can execute the program code 312 to enable the relay UE to: (i) receive a first message from the source UE, wherein the first message will establish a 1st hop PC5 connection with the relay UE for communication with any target UE, (ii) send a second message, wherein the second message will establish a 2nd hop PC5 connection with any target UE for communication with the source UE, (iii) receive a third message from the first target UE for establishing a first security context for the 2nd hop PC5 connection, (iv) receive a fourth message from the second target UE for establishing a second security context for the 2nd hop PC5 connection, and (v) discard the fourth message in response to the acceptance of the third message or send a rejection message corresponding to the fourth message to the second target UE. In addition, the CPU 308 can execute the program code 312 to perform all of the above actions and steps or other actions and steps described herein.

[1024] Fig.25 2500 is a flowchart of a method for a relay UE. In step 2505, the relay UE receives a first message from a source UE, wherein the first message will establish a 1st hop PC5 connection with the relay UE for supporting inter-UE (U2U) relay communication with any target UE. In step 2510, the relay UE establishes at least a first 2nd hop PC5 connection with a first target UE for supporting U2U relay communication with the source UE. In step 2515, the relay UE sends a second message to the source UE in response to the completion of the first 2nd hop PC5 connection, wherein the second message will complete the establishment of the 1st hop PC5 connection and contain user information of the first target UE. In step 2520, the relay UE establishes a second 2nd hop PC5 connection with a second target UE for supporting U2U relay communication with the source UE. In step 2525, the relay UE sends a third message to the source UE in response to the completion of the second 2nd hop PC5 connection to request modification of the 1st hop PC5 connection to add a second target UE for U2U relay communication, wherein the third message includes user information of the second target UE.

[1025] In one embodiment, the first message may not include any user information of the target UE. The second message may include user information of the source UE, user information of the relay UE, a relay service code, and user information of the first target UE. The third message may include user information of the second target UE.

[1026] In one embodiment, the first message may be a direct communication request message or a ProSe direct link establishment request message, the second message is a direct communication acceptance message or a ProSe direct link establishment acceptance message, and the third message is a link modification request message or a ProSe direct link modification request message.

[1027] Return to reference Figure 3 and 4 In one exemplary embodiment from the perspective of a relay UE, the relay UE 300 includes program code 312 stored in a memory 310 . The CPU 308 can execute the program code 312 to enable the relay UE to: (i) receive a first message from the source UE, wherein the first message will establish a 1st-hop PC5 connection with the relay UE for supporting UE-to-UE (U2U) relay communication with any target UE, (ii) establish at least a first 2nd-hop PC5 connection with a first target UE for supporting U2U relay communication with the source UE, (iii) send a second message to the source UE in response to the completion of the first 2nd-hop PC5 connection, wherein the second message will complete the establishment of the 1st-hop PC5 connection and include user information of the first target UE, (iv) establish a second 2nd-hop PC5 connection with a second target UE for supporting U2U relay communication with the source UE, and (v) send a third message to the source UE in response to the completion of the second 2nd-hop PC5 connection for requesting to modify the 1st-hop PC5 connection to add a second target UE for U2U relay communication, wherein the third message includes user information of the second target UE. Furthermore, CPU 308 may execute program code 312 to perform all of the above-described actions and steps or other actions and steps described herein.

[1028] Fig.26 is a flow chart 2600 of a method for relaying a UE.

[1029] …

[1030] Return to reference Figure 3 and 4 In one exemplary embodiment from the perspective of a relay UE, the relay UE 300 includes a program code 312 stored in a memory 310. The CPU 308 may execute the program code 312 to enable the relay UE to (i) ..., (ii) ..., and (iii) .... In addition, the CPU 308 may execute the program code 312 to perform all of the above actions and steps or other actions and steps described herein.

[1031] Various aspects of the present disclosure have been described above. It should be understood that the teachings herein can be implemented in a wide variety of forms, and any specific structure, function, or both disclosed herein are only representative. Based on the teachings herein, it should be understood by those skilled in the art that the aspects disclosed herein can be implemented independently of any other aspects, and two or more of these aspects can be combined in various ways. For example, any number of aspects set forth herein can be used to implement a device or practice method. In addition, other structures, functionality, or structures and functionality other than one or more aspects set forth herein or different from the aspects can be used to implement such devices or practice such methods. As examples of some of the above concepts, in some aspects, parallel channels can be established based on pulse repetition frequencies. In some aspects, parallel channels can be established based on pulse positions or offsets. In some aspects, parallel channels can be established based on hopping sequences. In some aspects, parallel channels can be established based on pulse repetition frequencies, pulse positions or offsets, and time hopping sequences.

[1032] Those skilled in the art will understand that information and signals may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the above description may be represented by voltage, current, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.

[1033] Those skilled in the art will further appreciate that the various illustrative logical blocks, modules, processors, components, circuits, and algorithm steps described in conjunction with the various aspects disclosed herein may be implemented as electronic hardware (e.g., a digital implementation, an analog implementation, or a combination of the two that may be designed using source decoding or some other technique), various forms of programs or design code incorporating instructions (which, for convenience, may be referred to herein as "software" or "software modules"), or a combination of the two. In order to clearly illustrate the interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends on the specific application and the design constraints imposed on the overall system. Those skilled in the art may implement the described functionality in different ways for each specific application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present disclosure.

[1034] In addition, the various illustrative logical blocks, modules, and circuits described in conjunction with the aspects disclosed herein may be implemented within or performed by an integrated circuit ("IC"), an access terminal, or an access point. The IC may include a general purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, electrical components, optical components, mechanical components, or any combination thereof designed to perform the functions described herein, and may execute code or instructions residing within the IC, outside the IC, or both. A general purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. The processor may also be implemented as a combination of computing devices, such as a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

[1035] It should be understood that any specific order or hierarchy of steps in any disclosed process is an example of an exemplary method. It should be understood that based on design preferences, the specific order or hierarchy of steps in a process can be rearranged while remaining within the scope of the present disclosure. The accompanying method claims present elements of the various steps in a sample order and are not intended to be limited to the specific order or hierarchy presented.

[1036] The steps of the method or algorithm described in conjunction with the various aspects disclosed herein can be implemented directly with hardware, with a software module executed by a processor, or with a combination of the two. Software modules (e.g., including executable instructions and related data) and other data can reside in a data memory, such as a RAM memory, a flash memory, a ROM memory, an EPROM memory, an EEPROM memory, a register, a hard disk, a removable disk, a CD-ROM, or any other form of a computer-readable storage medium known in the art. A sample storage medium can be coupled to a machine such as a computer / processor (for convenience, the machine can be referred to as a "processor" in this article) so that the processor can read information (e.g., code) from the storage medium and write information to the storage medium. A sample storage medium can be integrated with a processor. The processor and the storage medium can reside in an ASIC. The ASIC can reside in a user device. In an alternative, the processor and the storage medium can reside in a user device as discrete components. In addition, in some aspects, any suitable computer program product may include a computer-readable medium, and the computer-readable medium includes a code related to one or more of the various aspects of the present disclosure. In some aspects, a computer program product may include packaging materials.

[1037] Although the present invention has been described in conjunction with various aspects, it will be appreciated that the invention is capable of further modification. This application is intended to cover any changes, uses or adaptations of the present invention that generally follow the principles of the invention and include such deviations from the present disclosure that are within the scope of known and customary practice in the technical field to which the invention pertains.

Claims

1. A method for relaying user equipment, characterized in that: include: The relay user equipment receives a first message from a source user equipment, wherein the first message is to establish a connection with the first hop PC5 of the relay user equipment to support inter-user equipment relay communication with any target user equipment; The relay user equipment at least establishes a first second-hop PC5 connection with the first target user equipment to support the inter-user equipment relay communication with the source user equipment; The relay user equipment sends a second message to the source user equipment in response to the completion of the first second-hop PC5 connection, wherein the second message completes the establishment of the first-hop PC5 connection; The relay user equipment establishes a second second-hop PC5 connection with a second target user equipment to support the inter-user equipment relay communication with the source user equipment; as well as In response to the completion of the second second-hop PC5 connection, the relay UE sends a third message to the source-end UE to request modification of the first-hop PC5 connection to add the second target-end UE for relay communication between the UEs.

2. The method according to claim 1, characterized in that The first message does not include any user information of the target user equipment.

3. The method according to claim 1, characterized in that The second message includes user information of the source user equipment, user information of the relay user equipment, a relay service code, and user information of the first target user equipment.

4. The method according to claim 1, characterized in that: The third message includes user information of the second target user equipment.

5. The method according to claim 1, characterized in that The first message is a direct communication request message or a proximity based service direct link setup request message, the second message is a direct communication accept message or a proximity based service direct link setup accept message, and the third message is a link modification request message or a proximity based service direct link modification request message.

6. A relay user equipment, characterized in that: include: Control circuit; a processor installed in the control circuit; as well as a memory installed in the control circuit and operatively coupled to the processor; wherein the processor is configured to execute program code stored in the memory to: Receiving a first message from a source user device, wherein the first message is to establish a first hop PC5 connection with the relay user device for supporting inter-user device relay communication with any target user device; Establish at least a first second-hop PC5 connection with a first target-end user equipment to support the inter-user equipment relay communication with the source-end user equipment; sending a second message to the source end user equipment in response to the completion of the first second hop PC5 connection, wherein the second message completes the establishment of the first hop PC5 connection; Establishing a second second-hop PC5 connection with a second target-end user equipment to support the inter-user equipment relay communication with the source-end user equipment; as well as In response to the completion of the second second-hop PC5 connection, a third message is sent to the source-end user equipment for requesting to modify the first-hop PC5 connection to add the second target-end user equipment for relay communication between the user equipments.

7. The relay user equipment according to claim 6, characterized in that: The first message does not include any user information of the target user equipment.

8. The relay user equipment according to claim 6, characterized in that: The second message includes user information of the source user equipment, user information of the relay user equipment, a relay service code, and user information of the first target user equipment.

9. The relay user equipment according to claim 6, characterized in that: The third message includes user information of the second target user equipment.

10. The relay user equipment according to claim 6, characterized in that: The first message is a direct communication request message or a proximity based service direct link setup request message, the second message is a direct communication accept message or a proximity based service direct link setup accept message, and the third message is a link modification request message or a proximity based service direct link modification request message.

11. A method for relaying user equipment, characterized in that: include: The relay user equipment receives a first message from a source user equipment, wherein the first message is to establish a connection with the first hop PC5 of the relay user equipment to support inter-user equipment relay communication with any target user equipment; The relay user equipment establishes a first second-hop PC5 connection with the first target user equipment to support the inter-user equipment relay communication with the source user equipment; The relay user equipment establishes a second second-hop PC5 connection with a second target user equipment to support the inter-user equipment relay communication with the source user equipment; as well as The relay user equipment sends a second message to the source user equipment, wherein the second message completes the establishment of the first-hop PC5 connection and contains the user information of the first target user equipment and the user information of the second target user equipment.

12. The method according to claim 11, characterized in that The first message includes user information of the source user equipment, a relay service code, etc., and does not include user information of any target user equipment.

13. The method according to claim 11, characterized in that The first message is a direct communication request message or a proximity based service direct link setup request message, and the second message is a direct communication accept message or a proximity based service direct link setup accept message.

14. A relay user equipment, characterized in that: include: Control circuit; a processor installed in the control circuit; as well as a memory installed in the control circuit and operatively coupled to the processor; wherein the processor is configured to execute program code stored in the memory to: Receiving a first message from a source user device, wherein the first message is to establish a first hop PC5 connection with the relay user device for supporting inter-user device relay communication with any target user device; Establishing a first second-hop PC5 connection with a first target-end user device to support the inter-user device relay communication with the source-end user device; Establishing a second second-hop PC5 connection with a second target-end user equipment to support the inter-user equipment relay communication with the source-end user equipment; as well as A second message is sent to the source-end user equipment, wherein the second message completes the establishment of the first-hop PC5 connection and contains the user information of the first target-end user equipment and the user information of the second target-end user equipment.

15. The relay user equipment according to claim 14, characterized in that: The first message includes user information of the source user equipment, a relay service code, etc., and does not include user information of any target user equipment.

16. The relay user equipment according to claim 14, characterized in that: The first message is a direct communication request message or a proximity based service direct link setup request message, and the second message is a direct communication accept message or a proximity based service direct link setup accept message.

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