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

Abstract

A method and a relay user equipment (UAE) for inter-user equipment (UAE) relay communication are disclosed. A direct link is established between the relay UAE and a second-end UAE to support UAE-UAE relay communication via the relay UAE between a first-end UAE and the second-end UAE. The relay UAE receives a second message from the first-end UAE to establish a security context or add new PC5 Quality of Service (QoS) information between the relay UAE and the first-end UAE. The second message includes first PC5 QoS information for supporting UAE-UAE relay communication and the Media Access Control (MAC) address of the first-end UAE. In response to receiving the first PC5 QoS information, the relay UAE sends a third message to the second-end UAE to modify or update the direct link. The third message includes second PC5 QoS information for supporting UAE-UAE relay communication and the MAC address of the first-end UAE included in the second message.

Description

[0001] Cross-reference to related applications

[0002] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 778,925, filed March 27, 2025, the entire disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0003] This disclosure generally relates to wireless communication networks, and more specifically, to a method and apparatus in a wireless communication system that supports a link establishment procedure with integrated discovery for inter-UE relay communication. Background Technology

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

[0005] An exemplary network architecture is the Evolved Universal Terrestrial Radio Access Network (E-UTRAN). E-UTRAN systems can provide high data throughput to enable the aforementioned IP-based voice and multimedia services. Currently, the 3rd Generation Partnership Project (3GPP) standards organization is discussing next-generation (e.g., 5G) radio technologies. Therefore, changes to the current framework of 3GPP standards are being submitted and considered to evolve and finalize the 3GPP standards. Summary of the Invention

[0006] This invention discloses a method and apparatus for relaying user equipment (UE). In one embodiment, the relay UE establishes a direct link with a second-end UE to support UE-to-UE (U2U) relay communication between a first-end UE and the second-end UE via the relay UE. Furthermore, after establishing the direct link between the relay UE and the second-end UE, the relay UE sends a first message to the first-end UE to trigger the establishment of a security connection between the two UEs. The relay UE also receives a second message from the first-end UE to establish a security context or add new PC5 Quality of Service (QoS) information between the relay UE and the first-end UE, wherein the second message includes first PC5 QoS information for supporting U2U relay communication and the media access control (MAC) address of the first-end UE. Furthermore, in response to receiving the first PC5 QoS information, the relay UE sends a third message to the second-end UE to modify or update the direct link, wherein the third message includes second PC5 QoS information for supporting U2U relay communication and the MAC address of the first-end UE included in the second message. Attached Figure Description

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

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

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

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

[0011] Figure 5 For 3GPP TS 23.304 V18.7.0 Figure 6 Reproduction of 7.1.1-1;

[0012] Figure 6 For 3GPP TS 23.304 V18.7.0 Figure 6 Reproduction of .7.3.2-1;

[0013] Figure 7 For 3GPP TS 24.554 V18.8.0 Figure 7 Reproduction of .2.3.2.1;

[0014] Figure 8 For 3GPP TS 24.554 V18.8.0 Figure 7 Reproduction of .2.3.2.2;

[0015] Figure 9 Reproduction of Table 10.3.2.1.1 of 3GPP TS 23.554 V18.8.0;

[0016] Figure 10 Reproduction of Table 10.3.6.1.1 of 3GPP TS 23.554 V18.8.0;

[0017] Figure 11 Reproduction of Table 10.3.14.1.1 of 3GPP TS 23.554 V18.8.0;

[0018] Figure 12 An exemplary MAC address exchange is illustrated in a relay communication scenario without integrated discovery, according to an exemplary embodiment.

[0019] Figure 13 An exemplary MAC address exchange is illustrated in a relay communication scenario with integrated discovery, according to an exemplary embodiment.

[0020] Figure 14 This is a message flow diagram according to an exemplary embodiment;

[0021] Figure 15 This is a message flow diagram according to an exemplary embodiment;

[0022] Figure 16 A flowchart according to an exemplary embodiment;

[0023] Figure 17 This is a message flow diagram according to an exemplary embodiment;

[0024] Figure 18 This is a message flow diagram according to an exemplary embodiment;

[0025] Figure 19 A flowchart according to an exemplary embodiment;

[0026] Figure 20 This is a flowchart according to an exemplary embodiment. Detailed Implementation

[0027] The exemplary wireless communication systems and apparatus described below employ wireless communication systems that support broadcast services. Wireless communication systems are widely deployed to provide various types of communication, such as voice and data. These systems may be based on Code Division Multiple Access (CDMA), Time Division Multiple Access (TDMA), Orthogonal Frequency Division Multiple Access (OFDMA), 3GPP Long Term Evolution (LTE) radio access, 3GPP Long Term Evolution Advanced (LTE-A or Advanced LTE), 3GPP2 Ultra Mobile Broadband (UMB), WiMax, 3GPP New Radio (NR), or some other modulation techniques.

[0028] To be clear, the exemplary wireless communication systems and apparatus described below may be designed to support one or more standards, such as those provided by the alliance known herein as the 3rd Generation Partnership Project (3GPP), including: 3GPP TS 23.304 V18.7.0, "Proximity-based Service (ProSe) in 5G Systems (5GS) (Revision 18)"; and 3GPP TS 24.554 V18.8.0, "Proximity Service (ProSe) in Protocol Aspects of 5G Systems (5GS) (Revision 18)".

[0029] The standards and documents listed above are hereby explicitly incorporated in their entirety.

[0030] Figure 1 A multiple access wireless communication system according to an embodiment of the present invention is illustrated. Access network 100 (AN) includes multiple antenna groups, one group comprising 104 and 106, another group comprising 108 and 110, and an additional group comprising 112 and 114. Figure 1In this diagram, only two antennas are shown for each antenna group; however, each antenna group may utilize more or fewer antennas. Access terminal 116 (AT) communicates with antennas 112 and 114, which transmit information to AT 116 via forward link 120 and receive information from AT 116 via reverse link 118. Access terminal (AT) 122 communicates with antennas 106 and 108, which transmit information to AT 122 via forward link 126 and receive information from AT 122 via reverse link 124. In a Frequency Division Duplex (FDD) system, communication links 118, 120, 124, and 126 may use different frequencies for communication. For example, forward link 120 may use a different frequency than reverse link 118.

[0031] Each antenna group and / or the area in which the antenna groups are designed to communicate is often referred to as a sector of the access network. In an embodiment, each antenna group is designed to communicate with an access terminal in a sector of an area covered by access network 100.

[0032] In communications via forward links 120 and 126, the transmit antennas of access network 100 can utilize beamforming to improve the signal-to-noise ratio of the forward links used for different access terminals 116 and 122. Furthermore, compared to an access network transmitting to all its access terminals via a single antenna, using beamforming to transmit to access terminals randomly distributed within its coverage area causes less interference to access terminals in neighboring cells.

[0033] An access network (AN) can be a fixed station or base station used for communication with terminals, and may also be referred to as an access point, Node B, base station, enhanced base station, evolved Node B (eNB), network node, network, or other terms. An access terminal (AT) may also be referred to as a user equipment (UE), wireless communication device, terminal, access terminal, or other terms.

[0034] Figure 2 This is a simplified block diagram of an embodiment of a multiple input multiple output (MIMO) system 200, specifically 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)). At the transmitter system 210, service data for multiple data streams is provided from a data source 212 to a transport (TX) data processor 214.

[0035] In one embodiment, each data stream is transmitted via a corresponding transmit antenna. The TX data processor 214 formats, encodes, and interleaves the service data of each data stream based on a specific encoding scheme selected for the data stream to provide encoded data.

[0036] OFDM technology can be used to multiplex the coded data and pilot data of each data stream. The pilot data is typically a known data pattern processed in a known manner and can be used at the receiver system to estimate the channel response. The multiplexed pilot and coded data of each data stream are then modulated (i.e., symbol mapped) based on a specific modulation scheme selected for the data stream (e.g., Binary Phase Shift Keying (BPSK), Quadrature Phase Shift Keying (QPSK), Multiple Phase Shift Keying (M-PSK), or Quadrature Amplitude Modulation (M-QAM)). The data rate, coding, and modulation of each data stream can be determined by instructions executed by processor 230.

[0037] The modulation symbols of all data streams are then provided to the TX MIMO processor 220, which can further process the modulation symbols (e.g., for OFDM). The TX MIMO processor 220 then provides NT modulation symbol streams to NT transmitters (TMTRs) 222a to 222t. In some embodiments, the TX MIMO processor 220 applies beamforming weights to the symbols of the data streams and to the antennas from which the symbols are being transmitted.

[0038] Each transmitter 222 receives and processes a corresponding symbol stream to provide one or more analog signals, and further modulates (e.g., amplifies, filters, and upconverts) the analog signals to provide modulated signals suitable for transmission over a MIMO channel. Subsequently, NT modulated signals from transmitters 222a to 222t are transmitted from NT antennas 224a to 224t, respectively.

[0039] At receiver system 250, the transmitted modulated signal is received by NR antennas 252a to 252r, and the signal received from each antenna 252 is provided to the corresponding receivers (RCVRs) 254a to 254r. Each receiver 254 modulates (e.g., filters, amplifies, and down-converts) the corresponding received signal, digitizes the modulated signal to obtain a sample, and further processes the sample to provide the corresponding "received" symbol stream.

[0040] The RX data processor 260 then receives and processes the NR symbol streams received from the NR receivers 254 based on specific receiver processing techniques to provide NT "detected" symbol streams. The RX data processor 260 then demodulates, deinterleaves, and decodes each detected symbol stream to recover the service data of the data stream. The processing performed by the RX data processor 260 is complementary to the processing performed by the TX MIMO processor 220 and TX data processor 214 at the transmitter system 210.

[0041] Processor 270 periodically determines which precoding matrix to use (discussed below). Processor 270 formulates a reverse link message that includes the matrix index portion and the rank portion.

[0042] The reverse link message may include various types of information about the communication link and / or the received data stream. The reverse link message is then processed by the TX data processor 238, which also receives service data from several data streams from the data source 236, modulated by the modulator 280, regulated by the transmitters 254a to 254r, and transmitted back to the transmitter system 210.

[0043] At transmitter system 210, the modulated signal from receiver system 250 is received by antenna 224, conditioned by receiver 222, demodulated by demodulator 240, and processed by RX data processor 242 to extract the reverse link message transmitted by receiver system 250. Processor 230 then determines which precoding matrix to use to determine beamforming weights and then processes the extracted message.

[0044] Turn Figure 3 This figure illustrates an alternative simplified functional block diagram of a communication device according to an embodiment of the present invention. Figure 3 As shown, this can be achieved using the communication device 300 in a wireless communication system. Figure 1 UE (or AT) 116 and 122 or Figure 1 The communication device 300 includes a base station (or AN) 100, and the wireless communication system is preferably an NR system. The communication device 300 may include an input device 302, an output device 304, a control circuit 306, a central processing unit (CPU) 308, a memory 310, program code 312, and a transceiver 314. The control circuit 306 executes the program code 312 in the memory 310 via the CPU 308, thereby controlling the operation of the communication device 300. The communication device 300 can receive signals input by a user via the input device 302 (e.g., a keyboard or keypad) and can output images and sounds via the output device 304 (e.g., a display or speaker). The transceiver 314 is used to receive and transmit wireless signals, transmit the received signals to the control circuit 306, and wirelessly output signals generated by the control circuit 306. The communication device 300 in the wireless communication system can also be used for this purpose. Figure 1 AN 100 in the middle.

[0045] Figure 4 According to an embodiment of the present invention, in Figure 3 A simplified block diagram of program code 312 is shown below. In this embodiment, program code 312 includes an application layer 400, a layer 3 portion 402, and a layer 2 portion 404, and is coupled to a layer 1 portion 406. Layer 3 portion 402 typically performs radio resource control. Layer 2 portion 404 typically performs link control. Layer 1 portion 406 typically performs physical connections.

[0046] 3GPP TS 23.304 introduces the following:

[0047] 6.4.3.7.1 Common part for Layer 2 link management of PC5 reference points for 5G ProSe UE inter-relay

[0048] For 5G ProSe communication via 5G ProSe UE-to-UE relay as described in Clauses 6.7.1 and 6.7.2:

[0049] -The direct communication request message via the first hop PC5 reference point contains:

[0050] - User information of the source 5G ProSe UE (i.e., application layer ID): Identifier of the source 5G ProSe UE requesting relay operation.

[0051] -5G ProSe Inter-UE Relay User Information ID: The identifier of the inter-UE relay provided to the source 5G ProSe UE during the 5G ProSe Inter-UE Relay discovery procedure.

[0052] - User information of the target 5G ProSe UE (i.e., application layer ID): The identifier of the target 5G ProSe UE provided to the source 5G ProSe UE during the UE inter-relay discovery procedure.

[0053] - (Optional) Destination Layer 2 ID of the target 5G ProSe UE: The unicast destination Layer 2 ID of the target 5G ProSe UE determined by the source 5G ProSe UE, as specified in Clause 5.8.2.4.

[0054] -ProSe service information: Information about the ProSe identifier used to establish the request layer 2 link.

[0055] -RSC: Connectivity service requested by the source 5G ProSe UE from the 5G ProSe UE-to-UE relay.

[0056] - Security information: Information used to establish the security of the first hop PC5 link (see TS 33.503

[29] ).

[0057] The direct communication request message via the second hop PC5 reference point includes:

[0058] - User information of the source 5G ProSe terminal UE (i.e., application layer ID).

[0059] - User information (i.e., application layer ID) of the target 5G ProSe terminal UE.

[0060] -5G ProSe UE-to-UE relay user information ID.

[0061] -ProSe service information: Information about the ProSe identifier.

[0062] -RSC: Connectivity service requested by the source 5G ProSe UE from the 5G ProSe UE-to-UE relay.

[0063] - Security information: Information used to establish the security of the second-hop PC5 link (see TS 33.503

[29] ).

[0064] The message received via direct communication through the second-hop PC5 reference point includes:

[0065] - User information (i.e., application layer ID) of the target 5G ProSe terminal UE.

[0066] The message received via direct communication through the first hop PC5 reference point includes:

[0067] - User information (i.e., application layer ID) of the target 5G ProSe terminal UE.

[0068] -5G ProSe UE-to-UE relay user information ID.

[0069] The link modification request message via the first hop PC5 reference point includes:

[0070] - User information of the target 5G ProSe UE (i.e., application layer ID): The identifier of the target 5G ProSe UE provided to the source 5G ProSe UE during the UE inter-relay discovery procedure.

[0071] - (Optional) Destination Layer 2 ID of the target 5G ProSe UE: The unicast destination Layer 2 ID of the target 5G ProSe UE determined by the source 5G ProSe UE, as specified in Clause 5.8.2.4.

[0072] The link modification request message via the second hop PC5 reference point includes:

[0073] - User information of the source 5G ProSe terminal UE (i.e., application layer ID).

[0074] - User information (i.e., application layer ID) of the target 5G ProSe terminal UE.

[0075] The link modification received via the second-hop PC5 reference point includes:

[0076] - User information (i.e., application layer ID) of the target 5G ProSe terminal UE.

[0077] The link modification received via the first hop PC5 reference point includes:

[0078] - User information (i.e., application layer ID) of the target 5G ProSe terminal UE.

[0079] Each end-to-end unicast link used for 5G Layer 2 ProSe UE-to-UE relay is associated with a unicast link attribute set, which includes:

[0080] - User information (i.e., application layer ID) and layer 2 ID of the source 5G ProSe UE; and

[0081] - User information (i.e., application layer ID) and layer 2 ID of the target 5G ProSe UE; and

[0082] - Relay service code; and

[0083] - Information about PC5 QoS streams.

[0084] Each PC5 unicast link used for relaying between 5G Layer 3 ProSe UEs via the first hop is associated with a unicast link attribute set, which includes:

[0085] - User information (i.e., application layer ID) and layer 2 ID of the 5G ProSe terminal UE; and

[0086] -User information ID and Layer 2 ID for 5G ProSe UE-to-UE relay; and

[0087] - Relay service code; and

[0088] - Network layer protocols and information about PC5 QoS flows.

[0089] Each PC5 unicast link used for 5G Layer 3 ProSe UE-to-UE relay via the second hop is associated with a unicast link attribute set, which includes:

[0090] -User information ID and Layer 2 ID for 5G ProSe UE-to-UE relay; and

[0091] - User information (i.e., application layer ID) and layer 2 ID of the 5G ProSe terminal UE; and

[0092] - Relay service code; and

[0093] - Network layer protocols and information about PC5 QoS flows.

[0094] The unicast link attribute set should be updated accordingly after a Layer 2 link is modified or a Layer 2 link identifier is updated.

[0095] [...]

[0096] 6.4.3.7.3 Layer 2 link management via PC5 reference point for 5G ProSe Layer 3 UE inter-UE relay

[0097] For 5G ProSe communication via 5G ProSe Layer 3 UE relay as described in Clause 6.7.1, the description in Clause 6.4.3.7.1 applies, but with the following differences and notes:

[0098] - In the security procedure at the first hop PC5 reference point, the source 5G ProSe Layer 3 UE provides the 5G ProSe Layer 3 UE inter-relay with IP address configuration or link-local IPv6 address and end-to-end QoS information. If the PC5 link is used to transmit Ethernet services, the source 5G ProSe Layer 3 UE provides its Ethernet MAC address instead of IP-related information.

[0099] - In the security procedures at the second-hop PC5 reference point, the 5G ProSe Layer 3 UE-to-UE relay provides the target 5G ProSe UE with IP address configuration or link-local IPv6 address and QoS information for the second-hop QoS. If the PC5 link is used to transmit Ethernet services, the 5G ProSe Layer 3 UE-to-UE relay provides the Ethernet MAC address of the source 5G ProSe Layer 3 UE instead of IP-related information.

[0100] - Messages received via direct communication through the second-hop PC5 reference point additionally include IP address configuration or link-local IPv6 address and QoS information for the second-hop QoS. If the PC5 link is used to transmit Ethernet services, the target 5G ProSe Layer 3 UE provides its Ethernet MAC address instead of IP-related information.

[0101] - 5G ProSe Layer 3 UE-to-UE relay determines the QoS information of the first hop by considering the received second-hop QoS. The message received via direct communication through the first-hop PC5 reference point also includes IP address configuration or link-local IPv6 address, first-hop QoS information, and may include the IP address of the target 5G ProSe UE. If the PC5 link is used to transmit Ethernet services, the 5G ProSe Layer 3 UE-to-UE relay provides the Ethernet MAC address of the target 5G ProSe Layer 3 UE instead of IP-related information.

[0102] - To add a new end-to-end QoS flow or modify an existing end-to-end QoS flow, the source 5G ProSe UE additionally includes end-to-end QoS information in the link modification request message via the first-hop PC5 reference point, as described in Clause 6.4.3.4. To remove an end-to-end QoS flow, the source 5G ProSe UE includes the PFI of the first-hop QoS flow in the link modification request message via the first-hop PC5 reference point, as described in Clause 6.4.3.4. If the PC5 link is used to transmit Ethernet services, the source 5G ProSe Layer 3 UE can provide its Ethernet MAC address.

[0103] - To add a new end-to-end QoS flow or modify an existing end-to-end QoS flow, the 5G ProSe Layer 3 UE-to-UE relay in the link modification request message via the second-hop PC5 reference point additionally includes the second-hop QoS information for the target 5G ProSe end UE. To remove an end-to-end QoS flow, the 5G ProSe Layer 3 UE-to-UE relay in the link modification request message via the second-hop PC5 reference point includes the PFI of the second-hop QoS flow. If the PC5 link is used to transmit Ethernet services, the 5G ProSe Layer 3 UE-to-UE relay provides the Ethernet MAC address of the source 5G ProSe Layer 3 end UE.

[0104] - To add a new end-to-end QoS flow or modify an existing end-to-end QoS flow, the link modification accept message via the second-hop PC5 reference point additionally includes QoS information for the second-hop QoS. If the PC5 link is used to transmit Ethernet services, the target 5G ProSe layer 3 UE can provide its Ethernet MAC address.

[0105] To add new end-to-end QoS flows or modify existing end-to-end QoS flows, the 5G ProSe Layer 3 UE-to-UE relay determines the QoS information of the first hop by considering the received second-hop QoS. The link modification receive message through the first-hop PC5 reference point also includes the first-hop QoS information and may include the IP address of the target 5G ProSe UE. If the PC5 link is used to transmit Ethernet services, the 5G ProSe Layer 3 UE-to-UE relay provides the Ethernet MAC address of the target 5G ProSe Layer 3 UE instead of IP-related information.

[0106] When the PC5 link between a 5G ProSe Layer 3 UE and a 5G ProSe Layer 3 UE relay is released, the 5G ProSe Layer 3 UE relay can initiate the release of the PC5 link to the peer 5G ProSe Layer 3 UE, or notify the peer 5G ProSe Layer 3 UE that the peer PC5 link has been released.

[0107] 6.4.3.7.4 Layer 2 Link Management via PC5 Reference Point for 5G ProSe UE-to-UE Relay Communication with Integrated Discovery

[0108] This clause applies to 5G ProSe UE-to-UE relay communication with an integrated discovery procedure, as described in Clause 6.7.3.

[0109] The direct communication request message via the first hop PC5 reference point includes:

[0110] - User information of the source 5G ProSe terminal UE (i.e., application layer ID).

[0111] - (Optional) Target 5G ProSe UE User Information ID (i.e., Application Layer ID): Identifier of the target 5G ProSe UE, provided it is provided from the ProSe application layer.

[0112] - (Optional) Destination Layer 2 ID of the target 5G ProSe UE: The unicast destination Layer 2 ID of the target 5G ProSe UE determined by the source 5G ProSe UE, as specified in Clause 5.8.2.4.

[0113] -ProSe service information: Information about the ProSe identifier used to establish the request layer 2 link.

[0114] -RSC: Connectivity service requested by the source 5G ProSe UE from the 5G ProSe UE-to-UE relay.

[0115] -Relay_indication: Indicates whether the 5G ProSe UE-to-UE relay can send a direct communication request message based on the received direct communication request message containing relay_indication.

[0116] - Security information: Information used to establish the security of the first hop PC5 link (see TS 33.503

[29] ).

[0117] The direct communication request message via the second hop PC5 reference point includes:

[0118] - User information of the source 5G ProSe terminal UE (i.e., application layer ID).

[0119] -5G ProSe UE-to-UE relay user information ID.

[0120] - (Optional) User information for the target 5G ProSe end UE.

[0121] -ProSe service information: Information about the ProSe identifier.

[0122] -RSC: Connectivity service requested by the source 5G ProSe UE from the 5G ProSe UE-to-UE relay.

[0123] - Security information: Information used to establish the security of the second-hop PC5 link (see TS 33.503

[29] ).

[0124] The message received via direct communication through the second-hop PC5 reference point includes:

[0125] - User information (i.e., application layer ID) of the target 5G ProSe terminal UE.

[0126] The message received via direct communication through the first hop PC5 reference point includes:

[0127] - User information (i.e., application layer ID) of the target 5G ProSe terminal UE.

[0128] -5G ProSe UE-to-UE relay user information ID.

[0129] For 5G ProSe communication via 5G ProSe Layer 3 UE relay, the following additional notes apply:

[0130] - In the security procedure at the second hop PC5 reference point, the 5G ProSe Layer 3 UE-to-UE relay provides the target 5G ProSe end UE with an IP address configuration or a link-local IPv6 address.

[0131] - The direct communication accept message via the second-hop PC5 reference point also includes the IP address configuration or link-local IPv6 address (if IP communication is used) and the Ethernet MAC address of the target 5G ProSe UE (if Ethernet communication is used). QoS information is not included in the security procedures or direct communication accept message of the second-hop PC5 reference point.

[0132] - In the security procedure at the first hop PC5 reference point, the source 5G ProSe UE provides the 5G ProSe Layer 3 UE-to-UE relay with IP address configuration, link-local IPv6 address and end-to-end QoS information.

[0133] -5G ProSe Layer 3 UE-to-UE relay uses Layer 2 link modification to provide second-hop QoS information to the target 5G ProSe UE, as described in Clause 6.4.3.4.

[0134] - Taking into account the second-hop QoS received from the target 5G ProSe UE, the 5G ProSe Layer 3 UE-to-UE relay determines the QoS information of the first-hop QoS. The message received through direct communication with the first-hop PC5 reference point also includes the IP address configuration or link-local IPv6 address, the QoS information of the first-hop QoS, and may include the IP address of the target 5G ProSe UE (if using IP communication) or the Ethernet MAC address of the target 5G ProSe UE (if using Ethernet communication).

[0135] For 5G ProSe communication relayed between 5G ProSe Layer 2 UEs, the message content via the PC5 reference point for unicast mode 5G ProSe direct communication described in Clauses 6.4.3.1 to 6.4.3.5 is the same for end-to-end connections between peer 5G ProSe end UEs.

[0136] [...]

[0137] 6.7.1 5G ProSe Communication via 5G ProSe Layer 3 UE Inter-UE Relay

[0138] 6.7.1.1 Layer 2 Link Establishment for PC5 Communication via 5G ProSe Layer 3 UE Inter-UE Relay

[0139] Figure 6 .7.1.1-1 illustrates the procedure for establishing a Layer 2 link via 5G ProSe Layer 3 UE relay.

[0140] The document titled "Establishment of Layer 2 Links via 5G ProSe Layer 3 Inter-UE Relay" in 3GPP TS 23.304 V18.7.0 Figure 6 .7.1.1-1 reproduced as Figure 5 ]

[0141] 1. Perform service authorization and provisioning for the source 5G ProSe Layer 3 UE, the target 5G ProSe Layer 3 UE, and the relay between 5G ProSe Layer 3 UEs, as described in Clause 6.2.

[0142] 2. The source 5G ProSe Layer 3 UE performs the discovery of 5G ProSe Layer 3 UE-to-UE relay, as described in Clause 6.3.2.4.

[0143] 3. The source 5G ProSe Layer 3 UE sends a Direct Communication Request message to initiate a unicast Layer 2 link establishment procedure utilizing 5G ProSe Layer 3 UE-to-UE relay. The parameters included in the Direct Communication Request message are described in Clause 6.4.3.7.

[0144] The source layer 2 ID of the direct communication request message is assigned by the source 5G ProSe layer 3 UE, and the destination layer 2 ID is set to the source layer 2 ID of the discovery message for 5G ProSe layer 3 UE relay.

[0145] The 5G ProSe layer 3 UE obtains application information and optional ProSe application requirements from the ProSe application layer and determines end-to-end QoS parameters as described in Clause 5.6.3.1.

[0146] 4. If the user information ID of the 5G ProSe Layer 3 UE-to-UE relay in the direct communication request message matches the user information ID of the 5G ProSe UE-to-UE relay and the RSC in the direct communication request matches a (pre-)configured RSC specified by the relay as specified in Clause 5.1.5.1, then the 5G ProSe Layer 3 UE-to-UE relay responds by establishing security with the source 5G ProSe Layer 3 UE. When security protection is enabled, the source 5G ProSe Layer 3 UE sends the parameters described in Clause 6.4.3.7 to the 5G ProSe Layer 3 UE-to-UE relay.

[0147] If the Ethernet MAC address of the source 5G ProSe Layer 3 UE is already in use by another 5G ProSe Layer 3 UE, the 5G ProSe Layer 3 UE inter-relay refuses to establish a direct link, indicating that the MAC address is not unique.

[0148] The source layer 2 ID used for the security establishment procedure is assigned by the 5G ProSe layer 3 UE inter-relay itself, and the destination layer 2 ID is set to the source layer 2 ID of the received direct communication request message.

[0149] 5G ProSe Layer 3 UE inter-relay will select different source layer 2 IDs for PC5 links for different types of services (i.e., IP services, Ethernet services, and unstructured services).

[0150] If the PC5 link is used to transmit unstructured services, the 5G ProSe Layer 3 UE relay will select different source layer 2 IDs for the source and target 5G ProSe Layer 3 end UEs of different pairs.

[0151] Upon receiving the security establishment procedure message, the source 5G ProSe Layer 3 UE obtains the Layer 2 ID of the 5G ProSe Layer 3 UE relay for future communication, thereby enabling signaling and data services for this unicast link.

[0152] 5. After completing the security establishment procedure in step 4, the 5G ProSe Layer 3 UE-to-UE relay determines whether to use its existing unicast Layer 2 link with the target 5G ProSe UE for the required service. If no existing unicast Layer 2 link exists between the required RSC and the target 5G ProSe Layer 3 UE, the 5G ProSe Layer 3 UE-to-UE relay sends a direct communication request message to initiate a unicast Layer 2 link establishment procedure with the target 5G ProSe Layer 3 UE. The parameters included in the direct communication request message are described in clause 6.4.3.7.

[0153] The source Layer 2 ID of the direct communication request message is assigned by the 5G ProSe Layer 3 UE inter-relay itself, and the destination Layer 2 ID can be either a broadcast or unicast Layer 2 ID. The unicast Layer 2 ID is used only when the Layer 2 ID of the target 5G ProSe Layer 3 UE associated with the user information (i.e., the application layer ID) is known to the 5G ProSe Layer 3 UE inter-relay.

[0154] 5G ProSe Layer 3 UE inter-relay will select different source layer 2 IDs for PC5 links for different types of services (i.e., IP services, Ethernet services, and unstructured services).

[0155] If the PC5 link is used to transmit unstructured services, the 5G ProSe Layer 3 UE relay will select different source layer 2 IDs for the source and target 5G ProSe Layer 3 end UEs of different pairs.

[0156] 6. If the RSC contained in the direct communication request matches the RSC of the target UE (as specified in Clause 5.1.5.1, pre-configured), and if the user information contained in the direct communication request matches the user information of the target UE, the target 5G ProSe Layer 3 UE responds by establishing security with the 5G ProSe Layer 3 UE relay. When security protection is enabled, the 5G ProSe Layer 3 UE relay sends the parameters described in Clause 6.4.3.7 to the target 5G ProSe Layer 3 UE.

[0157] The source layer 2 ID used for the security establishment procedure is assigned by the target 5G ProSe layer 3 UE, and the destination layer 2 ID is set to the source layer 2 ID of the received direct communication request message.

[0158] Upon receiving the security establishment procedure message, the 5G ProSe Layer 3 UE inter-relay obtains the Layer 2 ID of the target 5G ProSe Layer 3 UE for future communication, thereby enabling signaling and data services on this unicast link.

[0159] 7. The target 5G ProSe Layer 3 UE sends a direct communication accept message to the 5G ProSe Layer 3 UE relay with which it has successfully established security. The parameters included in the direct communication accept message are described in Clause 6.4.3.7.

[0160] Note: When a 5G ProSe Layer 3 UE relay receives a direct communication accept message, it can detect that the Ethernet MAC address of the target 5G ProSe Layer 3 UE has been used by another 5G ProSe Layer 3 UE.

[0161] 8. For IP services, assign an IPv6 prefix or IPv4 address to the target 5G ProSe Layer 3 UE as defined in Clause 5.5.1.4.

[0162] 9. After receiving a direct communication accept message from the target 5G ProSe Layer 3 UE, the 5G ProSe Layer 3 UE relay sends a direct communication accept message to the source 5G ProSe Layer 3 UE with which it has successfully established security. The parameters included in the direct communication accept message are described in Clause 6.4.3.7.

[0163] 10. For IP services, assign an IPv6 prefix or IPv4 address to the source 5G ProSe Layer 3 UE as defined in Clause 5.5.1.4.

[0164] 11. For IP communication, the 5G ProSe Layer 3 UE inter-relay can store the association between user information (i.e., application layer ID) and the IP address of the target 5G ProSe Layer 3 UE in its DNS entries, and the 5G ProSe Layer 3 UE inter-relay can act as a DNS server for other UEs. If the IP address of the target 5G ProSe Layer 3 UE is not received in step 9, the source 5G ProSe Layer 3 UE can send a DNS query to the 5G ProSe Layer 3 UE inter-relay after step 10 to request the IP address of the target 5G ProSe Layer 3 UE, and the 5G ProSe Layer 3 UE inter-relay will transmit the IP address of the target 5G ProSe Layer 3 UE back to the source 5G ProSe Layer 3 UE.

[0165] For Ethernet communication, the 5G ProSe Layer 3 UE-to-UE relay maintains the association between the PC5 link and the Ethernet MAC address received from the 5G ProSe Layer 3 UE.

[0166] For unstructured service communication, for each pair of source and target 5G ProSe layer 3 UEs, the 5G ProSe layer 3 UE inter-relay maintains a 1:1 mapping between the PC5 link and the source 5G ProSe layer 3 UE, as well as between the PC5 link and the target 5G ProSe layer 3 UE.

[0167] 12. The source 5G ProSe layer 3 UE communicates with the target 5G ProSe layer 3 UE via 5G ProSe layer 3 UE relay.

[0168] In the scenario where a source 5G ProSe Layer 3 UE communicates with multiple target 5G ProSe Layer 3 UEs, according to the RSC, the PC5 link between the source 5G ProSe Layer 3 UE and the inter-UE relay can be shared among the multiple target 5G ProSe Layer 3 UEs. Simultaneously, according to the RSC, the PC5 link can be established individually between the inter-UE relay and the target 5G ProSe Layer 3 UEs. For shared PC5 links, a Layer 2 link modification procedure should be used instead of... Figure 6 Steps 3 to 4 and 9 to 10 of the procedure in .7.1.1-1. The parameters used in the Layer 2 link modification procedure are described in Clause 6.4.3.7.

[0169] In scenarios where multiple source 5G ProSe Layer 3 UEs communicate with a single target 5G ProSe Layer 3 UE, according to the RSC, the PC5 link between the 5G ProSe Layer 3 UE inter-relay and the target 5G ProSe Layer 3 UE can be shared. Simultaneously, according to the RSC, the PC5 link can be established individually between the source 5G ProSe Layer 3 UEs and the 5G ProSe Layer 3 UE inter-relay. For shared PC5 links, a Layer 2 link modification procedure should be used instead of... Figure 6 Steps 5 through 8 of the procedure in .7.1.1-1. The parameters used in the Layer 2 link modification procedure are described in Clause 6.4.3.7.

[0170] [...]

[0171] 6.7.3 5G ProSe UE-to-UE relay communication with integrated discovery

[0172] 6.7.3.1 Overview

[0173] Supports 5G ProSe communication via 5G ProSe UE-to-UE relay with integrated discovery.

[0174] For 5G ProSe inter-UE relay communication with integrated discovery, when a UE allows direct communication requests to other UEs involving inter-UE relay, the UE indicates this by including relay_indication in the broadcast direct communication request message.

[0175] When an inter-UE relay receives a direct communication request containing relay_indication, it determines whether to send a direct communication request message containing its own user information based on factors such as the relay service code (if it exists), ProSe service information, the operator policy for each relay service code, signal strength, and local policy.

[0176] 6.7.3.2 Procedures for communication via Layer 3 UE inter-relay

[0177] The document titled "5G ProSe Inter-UE Relay Communication with Integrated Discovery via Layer 3 Inter-UE Relay" in 3GPP TS 23.304 V18.7.0... Figure 6 7.3.2-1 reproduced as Figure 6 ]

[0178] The 0.5G ProSe UE is authorized and equipped with parameters to use services provided by 5G ProSe UE relay. The 5G ProSe UE relay is authorized and equipped with parameters to provide services for relaying services within the 5G ProSe UE.

[0179] 1. A source 5G ProSe UE (i.e., UE-1) wants to establish unicast communication with a target 5G ProSe UE (i.e., UE-2) and broadcasts a direct communication request. The parameters included in the direct communication request message are described in Clause 6.4.3.7.

[0180] The relay_indication in the direct communication request is used to indicate whether the 5G ProSe UE-to-UE relay can forward the direct communication request message (i.e., send a direct communication request based on the received direct communication request message). It is also used to limit the hop count of the 5G ProSe UE-to-UE relay by removing the relay_indication from the direct communication request message.

[0181] The source layer 2 ID and destination layer 2 ID used for direct communication request messages are defined in clause 5.8.5.

[0182] The source 5G ProSe end UE obtains application information and optional ProSe application requirements from the ProSe application layer and determines end-to-end QoS parameters as described in Clause 5.6.3.1.

[0183] Note 1: The data type of relay_indication can be determined in stage 3.

[0184] 2. When a direct communication request with relay_indication is received from UE-1, the 5G ProSe inter-UE relays (i.e., relay-1 and relay-2) may decide to participate in the procedure and broadcast a direct communication request message in their vicinity if no relay_indication is received. The parameters included in the direct communication request message are described in Clause 6.4.3.7.

[0185] The source layer 2 ID and destination layer 2 ID used for direct communication request messages are defined in clause 5.8.5.

[0186] 3. When UE-2 receives a direct communication request from one or more 5G ProSe inter-UE relays, UE-2 selects the 5G ProSe inter-UE relay to which UE-2 will respond. UE-2 may select the 5G ProSe inter-UE relay based on factors such as signal strength, local policies, and operator policies for each relay service code (if applicable).

[0187] 4. If necessary, security setup occurs between UE-2 and the selected 5G ProSe UE relay (relay-1 in this case).

[0188] If the existing PC5 link can be reused, then use the link modification request and link modification accept message.

[0189] Note 2: Conflicts between link modification requests and direct communication requests can be identified in phase 3.

[0190] 5. UE-2 replies to Relay-1 with a Direct Communication Acceptance Message. The parameters included in the Direct Communication Acceptance Message are described in Clause 6.4.3.7.

[0191] 6. For IP services, assign an IPv6 prefix or IPv4 address to the target 5G ProSe Layer 3 UE as defined in Clause 5.5.1.4.

[0192] 7. If necessary, security setup occurs between UE-1 and relay-1.

[0193] 8. For 5G ProSe UE-to-UE relay communication with integrated discovery, after receiving end-to-end QoS information from UE-1, relay-1 uses a link modification request message to provide UE-2 with second-hop QoS information.

[0194] 9. For 5G ProSe UE-to-UE relay communication with integrated discovery, UE-2 responds with a link modification acceptance message.

[0195] 10. Relay-1 responds to UE-1 using direct communication acceptance. The parameters included in the direct communication acceptance message are described in Clause 6.4.3.7.

[0196] 11. For IP services, assign an IPv6 prefix or IPv4 address to the source 5G ProSe Layer 3 UE as defined in Clause 5.5.1.4.

[0197] 12. For IP communication, the 5G ProSe Layer 3 UE inter-relay can store the association between user information (i.e., application layer ID) and the IP address of the target 5G ProSe Layer 3 UE in its DNS entries, and the 5G ProSe Layer 3 UE inter-relay can act as a DNS server for other UEs. If the IP address of the target 5G ProSe Layer 3 UE is not received in step 10, the source 5G ProSe Layer 3 UE can send a DNS query to the 5G ProSe Layer 3 UE inter-relay after step 11 to request the IP address of the target 5G ProSe Layer 3 UE, and the 5G ProSe Layer 3 UE inter-relay will transmit the IP address of the target 5G ProSe Layer 3 UE back to the source 5G ProSe Layer 3 UE.

[0198] For Ethernet communication, the 5G ProSe Layer 3 UE-to-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 UE.

[0199] For unstructured service communication, for each pair of source and target 5G ProSe layer 3 UEs, the 5G ProSe layer 3 UE inter-relay maintains a 1:1 mapping between the PC5 link and the source 5G ProSe layer 3 UE, as well as between the PC5 link and the target 5G ProSe layer 3 UE.

[0200] The source 5G ProSe layer 3 UE communicates with the target 5G ProSe layer 3 UE via 5G ProSe layer 3 UE relay.

[0201] 3GPP TS 24.554 introduces the following:

[0202] 7.2.2.4 The 5G ProSe direct link establishment procedure initiated by the UE is completed.

[0203] If the 5G ProSe direct link establishment procedure is not used for direct communication between the source 5G ProSe UE and the relay UE between the 5G ProSe UE, and:

[0204] - If the target user information (IE) is included in the PROSE DIRECT LINK ESTABLISHMENT REQUEST message, then upon receiving the PROSE DIRECT LINK ESTABLISHMENT ACCEPT message, the initiating UE will stop timer T5080; or

[0205] - If the target user information IE is not included in the PROSE DIRECT LINK ESTABLISHMENT REQUEST message, the initiating UE can keep timer T5080 running and continue to process multiple response messages from multiple target UEs (i.e., PROSE DIRECT LINK ESTABLISHMENT ACCEPT messages).

[0206] If the 5G ProSe direct link establishment procedure is used for direct communication between the source 5G ProSe UE and the relay UE between the 5G ProSe UE, and:

[0207] - If the UE user information (IE) for inter-UE relay is included in the PROSE DIRECT LINK ESTABLISHMENT REQUEST message, then upon receiving the PROSE DIRECT LINK ESTABLISHMENT ACCEPT message, the initiating UE will stop timer T5080; or

[0208] - If the UE user information (IE) of the inter-UE relay is not included in the PROSE DIRECT LINK ESTABLISHMENT REQUEST message (i.e., the 5G ProSe direct link establishment procedure is used for direct communication with integration discovery between the source 5G ProSe UE and the 5G ProSe inter-UE relay UE), then the initiating UE can keep timer T5080 running and continue to process multiple response messages from multiple target UEs (i.e., PROSE DIRECT LINK ESTABLISHMENT ACCEPT message).

[0209] For each received PROSE DIRECT LINK ESTABLISHMENT ACCEPT message, the initiating UE will uniquely assign a PC5 link identifier and generate a 5G ProSe direct link context for each 5G ProSe direct link. Then, the initiating UE stores the source layer 2 ID and destination layer 2 ID used in the transmission of this message provided by the lower layer in the 5G ProSe direct link context to complete the establishment of a 5G ProSe direct link with the target UE. From this point onward, the initiating UE should use the established link for ProSe direct communication via PC5, along with additional PC5 signaling messages reaching the target UE.

[0210] 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, then after receiving the PROSE DIRECT LINK ESTABLISHMENT ACCEPT message from the target 5G ProSe end UE, the initiating UE will initiate a 5G ProSe direct link security mode control procedure with the source 5G ProSe end UE, and after successfully completing the 5G ProSe direct link security mode control procedure with the source 5G ProSe end UE, the initiating UE will create a PROSE DIRECT LINK ESTABLISHMENT ACCEPT message as specified in Clause 7.2.2.3 to send to the source 5G ProSe end UE. If the target user information (IE) is not included in the PROSE DIRECT LINK ESTABLISHMENT REQUEST message, the initiating UE acting as a 5G ProSe inter-UE relay UE can initiate a 5G ProSe direct link security mode control procedure with the source 5G ProSe UE after processing multiple response messages (i.e., PROSE DIRECT LINK ESTABLISHMENT ACCEPT messages) from multiple target UEs. If the target user information (IE) is not included in the PROSE DIRECT LINK ESTABLISHMENT REQUEST message, the initiating UE acting as a 5G ProSe inter-UE relay UE can initiate a 5G ProSe direct link modification procedure to add additional target 5G ProSe UEs to the source 5G ProSe UE after processing multiple response messages (i.e., PROSE DIRECT LINK ESTABLISHMENT ACCEPT messages) from multiple target UEs.

[0211] Upon receiving the PROSE DIRECT LINK ESTABLISHMENT ACCEPT message, the initiating UE should provide the following information, along with the Layer 2 ID, to the lower layer, enabling the lower layer to process the incoming PC5 signaling or service data:

[0212] a) The PC5 link identifier assigned by the user for this 5G ProSe direct link;

[0213] b) PQFI and its corresponding PC5 QoS parameters (if available); and

[0214] c) Instructions to activate PC5 unicast user plane security protection for 5G ProSe direct links (if applicable).

[0215] The UE will start timer T5090 under the following conditions:

[0216] a) At least one ProSe identifier used for the 5G ProSe direct link satisfies the privacy requirements specified in Clause 5.2.4; or

[0217] b) T5090 shall be configured as specified in Clause 5.2.5.

[0218] Additionally, the initiating UE can perform PC5 QoS flow establishment via a 5G ProSe direct link as specified in Clause 7.2.7.

[0219] If, after timer T5080 expires:

[0220] - The 5G ProSe direct link establishment procedure is not used for direct communication between the source 5G ProSe UE and the relay UE between the 5G ProSe UEs, and the PROSE DIRECT LINK ESTABLISHMENT REQUEST message does not contain target user information (IE); or

[0221] - The 5G ProSe direct link establishment procedure is used for direct communication between the source 5G ProSe UE and the relay UE between 5G ProSe UEs, and the PROSE DIRECT LINK ESTABLISHMENT REQUEST message does not contain the relay UE user information (IE).

[0222] And when the UE receives at least one PROSE DIRECT LINK ESTABLISHMENT ACCEPT message, the UE implementation scheme determines whether to consider the 5G ProSe direct link establishment procedure as complete or to restart timer T5080.

[0223] If the 5G ProSe direct link establishment procedure is triggered by a PROSE DIRECTLINK MODIFICATION REQUEST message from the source 5G ProSe Layer 3 UE, as specified in Clause 7.2.3.2, then when the initiating UE acts as a 5G ProSe Layer 3 UE inter-UE relay UE, upon receiving the PROSE DIRECT LINK ESTABLISHMENT ACCEPT message, the initiating UE will send a PROSE DIRECT LINK MODIFICATION ACCEPT message to the source 5G ProSe Layer 3 UE, as specified in Clause 7.2.3.3.

[0224] If the 5G ProSe direct link establishment procedure is used for 5G ProSe direct communication between a 5G ProSe Layer 3 UE relay UE and a target 5G ProSe Layer 3 end UE for Ethernet services, and the initiating UE acting as the 5G ProSe Layer 3 UE relay UE detects that the MAC address of the target 5G ProSe Layer 3 end UE in the PROSE DIRECT LINK ESTABLISHMENT ACCEPT message is not unique, i.e., the MAC address of the target 5G ProSe Layer 3 end UE is also provided by another 5G ProSe Layer 3 end UE in the existing ProSe 5G direct link, then the 5G ProSe Layer 3 UE relay UE shall execute the 5G ProSe direct link release procedure as specified in Clause 7.2.6.

[0225] 7.2.2.5 5G ProSe Direct Link Establishment Procedure Not Accepted by the Target UE

[0226] If the PROSE DIRECT LINK ESTABLISHMENT REQUEST message cannot be accepted, the target UE should send a PROSE DIRECT LINK ESTABLISHMENT REJECT message. The PROSE DIRECT LINK ESTABLISHMENT REJECT message contains a PC5 signaling protocol reason IE set to one of the following reason values:

[0227] #1 Direct communication with the target UE is not allowed;

[0228] #3 A collision of Layer 2 IDs used for unicast communication was detected;

[0229] #5 Lack of resources for 5G ProSe direct links;

[0230] #13 Congestion situation;

[0231] #155G ProSe UE to network relay security procedure failure;

[0232] #225G ProSe UE-to-UE relay security procedure failure;

[0233] #20 Fault originating from the 5G ProSe UE;

[0234] #215G ProSe direct links already exist;

[0235] #23 MAC addresses are not unique;

[0236] #25 Unable to trigger security procedures; or

[0237] #111 Unspecified protocol error.

[0238] [...]

[0239] If the 5G ProSe direct link establishment procedure is used for 5G ProSe direct communication between the source 5G ProSe layer 3 UE and the 5G ProSe layer 3 UE relay UE for Ethernet services, and the target UE acting as the 5G ProSe layer 3 UE relay UE detects that the MAC address of the source 5G ProSe layer 3 UE in the PROSE DIRECT LINK SECURITY MODE COMPLETE message is not unique, that is, the MAC address of the source 5G ProSe layer 3 UE is also provided by another 5G ProSe layer 3 UE in the existing ProSe 5G direct link, then the 5G ProSe layer 3 UE relay UE will send a PROSE DIRECT LINK ESTABLISHMENTREJECT message containing the PC5 signaling protocol reason value #23 "MAC address is not unique" to the source 5G ProSe layer 3 UE.

[0240] If the 5G ProSe direct link establishment procedure is used for 5G ProSe direct communication between the source 5G ProSe layer 3 UE and the 5G ProSe layer 3 UE relay UE for Ethernet services, and the target UE acting as the 5G ProSe layer 3 UE relay UE releases the 5G ProSe direct link between the 5G ProSe layer 3 UE relay UE and the target 5G ProSe layer 3 UE, and the PC5 signaling protocol reason value is #23 "MAC address is not unique", then the 5G ProSe layer 3 UE relay UE will send a PROSE DIRECTLINK ESTABLISHMENT REJECT message containing the PC5 signaling protocol reason value #111 "unspecified protocol error" to the source 5G ProSe layer 3 UE.

[0241] [...]

[0242] 7.2.35G ProSe Direct Link Modification Program

[0243] 7.2.3.1 Overview

[0244] The purpose of the 5G ProSe direct link modification procedure is to modify the existing ProSe direct link to:

[0245] a) Add new PC5 QoS flows to existing 5G ProSe direct links;

[0246] b) Modify existing PC5 QoS flows to update the PC5 QoS parameters of existing PC5 QoS flows;

[0247] c) Modify existing PC5 QoS flows to associate the new ProSe application with existing PC5 QoS flows;

[0248] d) Modify an existing PC5 QoS stream to remove the associated ProSe application from the existing PC5 QoS stream;

[0249] e) Remove existing PC5 QoS flows from existing 5G ProSe direct links;

[0250] f) Negotiate new 5G ProSe UE-to-UE relay UEs on existing 5G ProSe direct links;

[0251] g) Establish 5G ProSe UE-to-UE relay communication with additional 5G ProSe UEs using the existing 5G ProSe direct link between 5G ProSe Layer 3 end UEs and 5G ProSe Layer 3 UE-to-UE relay UEs;

[0252] h) Use the shared 5G ProSe direct link between the 5G ProSe Layer 3 end UE and the 5G ProSe Layer 3 inter-UE relay UE to release 5G ProSe inter-UE relay communication with one of the peer 5G ProSe Layer 3 end UEs;

[0253] i) Establish 5G ProSe UE-to-UE relay communication with additional 5G ProSe layer 2 UEs using the existing 5G ProSe direct link between the 5G ProSe layer 2 end UE and the 5G ProSe layer 2 UE-to-UE relay UE; or

[0254] j) For 5G ProSe Layer 2 UE-to-UE relay, when the end-to-end 5G ProSe direct link is released, the existing PC5 QoS flow is removed from the existing 5G ProSe direct link between the 5G ProSe Layer 2 end UE and the 5G ProSe Layer 2 UE-to-UE relay UE.

[0255] 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".

[0256] Note: The 5G ProSe direct link modification procedure is not applicable to 5G ProSe Layer 2 UE to network relay scenarios.

[0257] 7.2.3.2 5G ProSe Direct Link Modification Procedure Initiated by the UE

[0258] Before initiating this procedure to add a new ProSe application to an existing 5G ProSe direct link, the following prerequisites must be met:

[0259] a) A 5G ProSe direct link exists between the initiating UE and the target UE;

[0260] b) If the initiating UE does not act as a 5G ProSe UE-to-network relay UE or 5G ProSe UE-to-network relay UE for an existing 5G ProSe direct link, then the application layer ID and network layer protocol of this 5G ProSe direct link pair are the same as the application layer ID and network layer protocol required by the application layer in the initiating UE of this ProSe application.

[0261] c) The security policy corresponding to the ProSe identifier is consistent with the existing security policy for 5G ProSe direct links;

[0262] d) Timer T5091 is not running; and

[0263] e) The UE does not execute the 5G ProSe direct link key update procedure initiated by the target UE.

[0264] Before initiating this procedure for negotiating a new 5G ProSe UE-to-UE relay UE on an existing 5G ProSe direct link, the following prerequisites must be met:

[0265] a) A 5G ProSe direct link exists between the initiating UE and the target UE;

[0266] b) The initiating UE is the source 5G ProSe UE that communicates with the target 5G ProSe UE via a 5G ProSe UE-to-UE relay UE;

[0267] c) Initiating UE-based trunk reselection, for example, based on PC5 signal strength; and

[0268] d) The UE initiates a process to obtain a list of candidate UE relays through the UE discovery procedure.

[0269] Before initiating this procedure to establish 5G ProSe UE-to-UE relay communication with additional 5G ProSe Layer 3 UEs on an existing 5G ProSe direct link, the following prerequisites must be met:

[0270] a) A 5G ProSe direct link exists between the initiating UE and the target UE;

[0271] b) The initiating UE acts as a 5G ProSe layer 3 terminal UE and the target UE acts as a 5G ProSe layer 3 inter-UE relay UE, or vice versa;

[0272] c) If acting as a 5G ProSe layer 3 UE, initiate UE determination to communicate with additional 5G ProSe layer 3 UEs using the same RSC as the existing 5G ProSe direct link; and

[0273] d) If acting as a 5G ProSe Layer 3 UE inter-UE relay UE, the initiating UE receives a request from another 5G ProSe Layer 3 end UE to communicate with the target UE using the same RSC as the existing 5G ProSe direct link.

[0274] If the initiating UE is not acting as a 5G ProSe UE-to-network relay UE or a 5G ProSe UE-to-network relay UE for an existing 5G ProSe direct link, the initiating UE shall perform PC5 QoS flow matching as specified in Clause 7.2.8 after receiving service data or requests from the upper layer. If no matching PC5 QoS flow exists, the initiating UE shall derive PC5 QoS parameters and assign a PQFI for the PC5 QoS flow established as specified in Clause 7.2.7.

[0275] If the 5G ProSe direct link modification procedure adds a new PC5 QoS flow to an existing 5G ProSe direct link, the initiating UE will create a PROSE DIRECT LINK MODIFICATION REQUEST message. In this message, the initiating UE:

[0276] a) Will include PQFI, corresponding PC5 QoS parameters, and optional ProSe identifier;

[0277] b) Include link modification operation code set to "Add new PC5 QoS flow to existing 5G ProSe direct link";

[0278] c) Packet filters may include PC5 QoS rules to indicate PC5 QoS flows;

[0279] d) If the UE acts as a 5G ProSe layer 3 UE relay UE, and the 5G ProSe direct link is between the 5G ProSe layer 3 UE relay UE and the target 5G ProSe layer 3 end UE, and multiple source 5G ProSe layer 3 end UEs use the same 5G ProSe direct link to establish direct communication with the target 5G ProSe layer 3 end UE via the 5G ProSe layer 3 UE relay UE, then the source end UE information containing the user information set as the source 5G ProSe layer 3 end UE will be included.

[0280] e) If 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 only one source 5G ProSe end UE uses the 5G ProSe direct link to establish direct communication with the target 5G ProSe end UE via the 5G ProSe inter-UE relay UE, then the source UE information, which is set as the user information of the source 5G ProSe end UE, can be included.

[0281] f) If the UE acts as the source 5G ProSe layer 3 end UE, the 5G ProSe direct link is between the source 5G ProSe layer 3 end UE and the 5G ProSe layer 3 UE inter-relay UE, and the source 5G ProSe layer 3 end UE uses the same 5G ProSe direct link to establish direct communication with multiple target 5G ProSe layer 3 end UEs via the 5G ProSe layer 3 UE inter-relay UE, then the target end UE information containing the user information set as the target 5G ProSe layer 3 end UE will be included.

[0282] g) Target UE information that may include user information set as the target 5G ProSe UE, if:

[0283] 1) The UE acts as the source 5G ProSe UE, the 5G ProSe direct link is between the source 5G ProSe UE and the 5G ProSe UE relay UE, and the source 5G ProSe UE establishes direct communication with only one target 5G ProSe UE via the 5G ProSe UE relay UE using the 5G ProSe direct link; or

[0284] 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

[0285] h) If the UE acts as the source 5G ProSe end UE and the 5G ProSe direct link is between the source 5G ProSe end UE and the relay UE between the 5G ProSe UE, then the target end UE layer 2 ID set as the layer 2 ID of the target 5G ProSe end UE can be included.

[0286] If the 5G ProSe direct link modification procedure modifies the PC5 QoS parameters of an existing PC5 QoS flow in an existing 5G ProSe direct link, the initiating UE will create a PROSE DIRECT LINK MODIFICATION REQUEST message. In this message, the initiating UE:

[0287] a) It will include PQFI and corresponding PC5 QoS parameters, including the ProSe identifier;

[0288] b) Include link modification operation code that is set to "Modify PC5 QoS parameters of existing PC5 QoS flows";

[0289] c) Packet filters may include PC5 QoS rules to indicate PC5 QoS flows;

[0290] d) If the UE acts as a 5G ProSe layer 3 UE relay UE, and the 5G ProSe direct link is between the 5G ProSe layer 3 UE relay UE and the target 5G ProSe layer 3 end UE, and multiple source 5G ProSe layer 3 end UEs use the same 5G ProSe direct link to establish direct communication with the target 5G ProSe layer 3 end UE via the 5G ProSe layer 3 UE relay UE, then the source end UE information containing the user information set as the source 5G ProSe layer 3 end UE will be included.

[0291] e) If 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 only one source 5G ProSe end UE uses the 5G ProSe direct link to establish direct communication with the target 5G ProSe end UE via the 5G ProSe inter-UE relay UE, then the source UE information, which is set as the user information of the source 5G ProSe end UE, can be included.

[0292] f) If the UE acts as the source 5G ProSe layer 3 end UE, the 5G ProSe direct link is between the source 5G ProSe layer 3 end UE and the 5G ProSe layer 3 UE inter-relay UE, and the source 5G ProSe layer 3 end UE uses the same 5G ProSe direct link to establish direct communication with multiple target 5G ProSe layer 3 end UEs via the 5G ProSe layer 3 UE inter-relay UE, then the target end UE information containing the user information set as the target 5G ProSe layer 3 end UE will be included.

[0293] g) Target UE information that may include user information set as the target 5G ProSe UE, if:

[0294] 1) The UE acts as the source 5G ProSe UE, the 5G ProSe direct link is between the source 5G ProSe UE and the 5G ProSe UE relay UE, and the source 5G ProSe UE establishes direct communication with only one target 5G ProSe UE via the 5G ProSe UE relay UE using the 5G ProSe direct link; or

[0295] 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

[0296] h) may include the destination layer 2 ID of the target 5G ProSe UE, if the UE acts as the source 5G ProSe UE and the 5G ProSe direct link is between the source 5G ProSe UE and the 5G ProSe UE relay UE.

[0297] If the 5G ProSe direct link modification procedure associates a new ProSe application with an existing PC5 QoS flow, the initiating UE will create a PROSE DIRECT LINK MODIFICATION REQUEST message. In this message, the initiating UE:

[0298] a) It will include PQFI and corresponding PC5 QoS parameters, including the ProSe identifier;

[0299] b) Include link modification operation code set to "Associate the new ProSe application with an existing PC5 QoS flow";

[0300] c) Packet filters may include PC5 QoS rules to indicate PC5 QoS flows;

[0301] d) If the UE acts as a 5G ProSe layer 3 UE relay UE, and the 5G ProSe direct link is between the 5G ProSe layer 3 UE relay UE and the target 5G ProSe layer 3 end UE, and multiple source 5G ProSe layer 3 end UEs use the same 5G ProSe direct link to establish direct communication with the target 5G ProSe layer 3 end UE via the 5G ProSe layer 3 UE relay UE, then the source end UE information containing the user information set as the source 5G ProSe layer 3 end UE will be included.

[0302] e) If 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 only one source 5G ProSe end UE uses the 5G ProSe direct link to establish direct communication with the target 5G ProSe end UE via the 5G ProSe inter-UE relay UE, then the source UE information, which is set as the user information of the source 5G ProSe end UE, can be included.

[0303] f) If the UE acts as the source 5G ProSe layer 3 end UE, the 5G ProSe direct link is between the source 5G ProSe layer 3 end UE and the 5G ProSe layer 3 UE inter-relay UE, and the source 5G ProSe layer 3 end UE uses the same 5G ProSe direct link to establish direct communication with multiple target 5G ProSe layer 3 end UEs via the 5G ProSe layer 3 UE inter-relay UE, then the target end UE information containing the user information set as the target 5G ProSe layer 3 end UE will be included.

[0304] g) Target UE information that may include user information set as the target 5G ProSe UE, if:

[0305] 1) The UE acts as the source 5G ProSe UE, the 5G ProSe direct link is between the source 5G ProSe UE and the 5G ProSe UE relay UE, and the source 5G ProSe UE establishes direct communication with only one target 5G ProSe UE via the 5G ProSe UE relay UE using the 5G ProSe direct link; or

[0306] 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

[0307] h) If the UE acts as the source 5G ProSe end UE and the 5G ProSe direct link is between the source 5G ProSe end UE and the relay UE between the 5G ProSe UE, then the target end UE layer 2 ID set as the layer 2 ID of the target 5G ProSe end UE can be included.

[0308] If the PC5 5G ProSe direct link modification procedure removes the associated ProSe application from an existing PC5 QoS flow, the initiating UE will create a PROSE DIRECT LINK MODIFICATION REQUEST message. In this message, the initiating UE:

[0309] a) Includes PQFI and corresponding PC5 QoS parameters, including the ProSe identifier; and

[0310] b) Include link modification operation code that is set to "Remove ProSe application from existing PC5 QoS flow".

[0311] If the direct link modification procedure removes any PC5 QoS flows from an existing 5G ProSe direct link, the initiating UE will create a PROSE DIRECT LINK MODIFICATION REQUEST message. In this message, the initiating UE:

[0312] a) Will include PQFI; and

[0313] b) Include link modification operation code set to "Remove existing PC5 QoS flow from existing 5G ProSe direct link".

[0314] If the 5G ProSe direct link modification procedure needs to establish 5G ProSe inter-UE relay communication with an additional 5G ProSe layer 3 UE using the existing 5G ProSe layer 3 end UE and the 5G ProSe layer 3 inter-UE relay UE, the initiating UE will create a PROSE DIRECT LINK MODIFICATION REQUEST message. In this message, the initiating UE:

[0315] a) 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, then the source end UE information, which includes the user information set as the source 5G ProSe layer 3 end UE, and the target end UE information, which includes the user information of the target 5G ProSe layer 3 end UE received in the PROSE DIRECT LINK ESTABLISHMENT REQUEST message, will be included.

[0316] b) For Ethernet services, 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, then the MAC address of the source 5G ProSe Layer 3 end UE will be included, and the MAC address of the source 5G ProSe Layer 3 end UE will be included if:

[0317] 1) The UE acts as the source 5G ProSe layer 3 UE inter-UE;

[0318] 2) Changes in the MAC address of the UE at the 5G ProSe layer 3; and

[0319] 3) The 5G ProSe direct link is between the relay UE and the source 5G ProSe layer 3 UE in the 5G ProSe layer 3 UE;

[0320] c) If the UE acts as a source 5G ProSe layer 3 end UE or a 5G ProSe layer 3 inter-UE relay UE, and the 5G ProSe direct link is between the source 5G ProSe layer 3 end UE and the 5G ProSe layer 3 inter-UE relay UE, then the target end UE information will include user information of the additional target 5G ProSe layer 3 end UE configured to request 5G ProSe inter-UE relay communication with it.

[0321] d) Include link modification operation code set to "Add a new 5G ProSe layer 3 UE to an existing 5G ProSe direct link";

[0322] e) May include PQFI and corresponding PC5 QoS parameters, including the ProSe identifier;

[0323] f) May include PC5 QoS rules to indicate packet filters for PC5 QoS flows; and

[0324] g) If the UE acts as the source 5G ProSe layer 3 end UE and the 5G ProSe direct link is between the source 5G ProSe layer 3 end UE and the relay UE between the 5G ProSe layer 3 UE, then the target end UE layer 2 ID, which is set as the layer 2 ID of the target 5G ProSe layer 3 end UE, may be included.

[0325] If the 5G ProSe direct link modification procedure will use the existing 5G ProSe direct link between the 5G ProSe Layer 2 UE and the 5G ProSe Layer 2 UE to establish 5G ProSe UE-to-UE relay communication with the additional 5G ProSe Layer 2 UE, then the initiating UE will create a PROSE DIRECT LINK MODIFICATION REQUEST message. In this message, the initiating UE:

[0326] a) If the UE acts as a 5G ProSe layer 2 inter-UE relay UE and the 5G ProSe direct link is between the 5G ProSe layer 2 inter-UE relay UE and the target 5G ProSe layer 2 end UE, then the source end UE information, which includes the user information set as the source 5G ProSe layer 2 end UE, and the target end UE information, which includes the user information of the target 5G ProSe layer 2 end UE received in the PROSE DIRECT LINK ESTABLISHMENT REQUEST message, will be included.

[0327] b) If the UE acts as the source 5G ProSe layer 2 end UE, and the 5G ProSe direct link is between the source 5G ProSe layer 2 end UE and the 5G ProSe layer 2 UE inter-relay UE, then the target end UE information will include user information of the additional target 5G ProSe layer 2 end UE configured to request 5G ProSe inter-UE relay communication with it; and

[0328] c) Include link modification operation code set to "Add a new 5G ProSe layer 2 UE to an existing 5G ProSe direct link".

[0329] If acting as the source 5G ProSe UE, the initiating UE must meet the following prerequisites before initiating this procedure for establishing 5G ProSe UE-to-UE relay communication with an additional 5G ProSe UE via the same 5G ProSe Layer 2 UE-to-UE relay UE:

[0330] a) There is no ongoing 5G ProSe direct link establishment or modification procedure between the initiating UE and the 5G ProSe layer 2 UE relay UE for establishing 5G ProSe UE relay communication with the target 5G ProSe end UE.

[0331] Note: The source 5G ProSe UE will not initiate any 5G ProSe direct link modification procedure to the same 5G ProSe layer 2 UE relay UE for communication with different target 5G ProSe layer 2 UEs, unless any current 5G ProSe direct link establishment or 5G ProSe direct link modification procedure has been completed, including receiving the layer 2 ID of the target 5G ProSe UE from the 5G ProSe layer 2 UE relay UE, as specified in TS 38.300

[12] .

[0332] If the 5G ProSe direct link modification procedure releases the shared 5G ProSe direct link between a 5G ProSe Layer 3 end UE and a 5G ProSe Layer 3 inter-UE relay UE, and releases 5G ProSe inter-UE relay communication with one of the peer 5G ProSe Layer 3 end UEs, then the initiating UE will create a PROSE DIRECT LINK MODIFICATION REQUEST message. In this message, the initiating UE:

[0333] a) 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, then the source end UE information will include the source user information of the 5G ProSe layer 3 end UE that is set in the PROSE DIRECT LINK RELEASEREQUEST message.

[0334] b) If the UE acts as a 5G ProSe Layer 3 end UE and the 5G ProSe direct link is between the 5G ProSe Layer 3 end UE and the 5G ProSe Layer 3 inter-UE relay UE, then the target end UE information will be included, which is configured to release the user information of the peer 5G ProSe Layer 3 end UE that will release the 5G ProSe inter-UE relay communication through it; and

[0335] c) Include link modification operation code set to "Remove 5G ProSe Layer 3 UE from existing 5G ProSe direct link".

[0336] If the 5G ProSe direct link modification procedure triggers negotiated 5G ProSe Layer 3 UE-to-UE relay reselection, the initiating UE will create a PROSE DIRECT LINK MODIFICATION REQUEST message. In this message:

[0337] a) If the initiating UE acts as the source 5G ProSe layer 3 UE, and the 5G ProSe direct link is between the source 5G ProSe layer 3 UE and the relay UE between the 5G ProSe layer 3 UE, then the initiating UE:

[0338] 1) Will include a trunk reselection instruction;

[0339] 2) A list of user information UEs for candidate 5G ProSe UE-to-UE relay UEs that support the same RSC for existing 5G ProSe direct links will be included;

[0340] 3) If IP communication is used, a list of the target 5G ProSe UE IP addresses / prefixes will be included; and

[0341] 4) May contain a list of Layer 2 IDs of candidate 5G ProSe UE-to-UE relay UEs that support the same RSC for existing 5G ProSe direct links; or

[0342] b) If the initiating 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 end UE, then the initiating UE:

[0343] 1) Will include a trunk reselection instruction;

[0344] 2) A list of user information UEs for candidate 5G ProSe UE-to-UE relay UEs that support the same RSC for existing 5G ProSe direct links will be included;

[0345] 3) If IP communication is used, it will include the originating 5G ProSe UE IP address / prefix; and

[0346] 4) It can include a list of Layer 2 IDs of candidate 5G ProSe UE-to-UE relay UEs that support the same RSC for existing 5G ProSe direct links.

[0347] If the 5G ProSe direct link modification procedure triggers a negotiated 5G ProSe Layer 3 UE inter-relay reselection and the initiating UE acts as a 5G ProSe Layer 3 UE inter-relay UE, then the initiating UE will create a PROSE DIRECT LINK MODIFICATION REQUEST message for each IP address / prefix of the target 5G ProSe Layer 3 UE received on the associated PROSE DIRECT LINK MODIFICATION REQUEST message from the source 5G ProSe Layer 3 UE.

[0348] If the 5G ProSe direct link modification procedure triggers negotiated 5G ProSe Layer 2 UE-to-UE relay reselection, the initiating UE will create a PROSE DIRECT LINK MODIFICATION REQUEST message. In this message:

[0349] a) Will include a relay reselection instruction;

[0350] b) A list containing candidate 5G ProSe UE-to-UE relay UE user information IDs;

[0351] c) A new MSB containing the KNRP ID; and

[0352] d) May contain a list of candidate 5G ProSe UE inter-UE relay UE layer 2 IDs.

[0353] If the 5G ProSe direct link modification procedure triggers a negotiated 5G ProSe inter-UE relay reselection, the initiating UE will include a link modification operation code IE set to a value other than the reserved value specified in Clause 11.3.19 of the PROSE DIRECT LINK MODIFICATION REQUEST message.

[0354] After generating the PROSE DIRECT LINK MODIFICATION REQUEST message, the initiating UE should pass this message to the lower layer along with the Layer 2 ID of the initiating UE for 5G ProSe direct communication and the Layer 2 ID of the target UE for 5G ProSe direct communication, and start timer T5081. While timer T5081 is running, the UE should not send new PROSEDIRECT LINK MODIFICATION REQUEST messages to the same target UE.

[0355] The document titled "5G ProSe Direct Link Modifier" in 3GPP TS 24.554 V18.8.0 Figure 7 2.3.2.1 Reproduced as Figure 7 ]

[0356] The document titled "5G ProSe Direct Link Modification Procedure for Negotiating 5G ProSe Layer 3 UE Inter-UE Relay Reselection" in 3GPP TS 24.554 V18.8.0... Figure 7 2.3.2.2 Reproduced as Figure 8 ]

[0357] 7.2.3.3 5G ProSe Direct Link Modification Procedure Accepted by the Target UE

[0358] If the PROSE DIRECT LINK MODIFICATION REQUEST message is accepted, the target UE will respond with the PROSEDIRECT LINK MODIFICATION ACCEPT message.

[0359] If the PROSE DIRECT LINK MODIFICATION REQUEST message adds a new ProSe application, then add a new PC5 QoS flow or modify any existing PC5 QoS flow in the 5G ProSe direct link, for the target UE:

[0360] a) It will include PQFI, corresponding PC5 QoS parameters, and the ProSe identifier accepted by the target UE (optional).

[0361] b) May contain PC5 QoS rules for indicating packet filters for PC5 QoS flows;

[0362] c) If the UE acts as the target 5G ProSe layer 3 end UE, the 5G ProSe direct link is between the 5G ProSe layer 3 UE relay UE and the target 5G ProSe layer 3 end UE, and the target 5G ProSe layer 3 end UE uses the same 5G ProSe direct link to establish direct communication with multiple source 5G ProSe layer 3 end UEs via the 5G ProSe layer 3 UE relay UE, then the source end UE information containing the user information set as the source 5G ProSe layer 3 end UE will be included.

[0363] d) If the UE acts as the target 5G ProSe end UE, the 5G ProSe direct link is between the 5G ProSe UE relay UE and the target 5G ProSe end UE, and the target 5G ProSe end UE uses the 5G ProSe direct link to establish direct communication with only one source 5G ProSe end UE via the 5G ProSe UE relay UE, then the source UE information that is set as the user information of the source 5G ProSe end UE can be included.

[0364] e) If the UE acts as a 5G ProSe inter-UE relay UE, and 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 layer 3 end UE establishes direct communication with multiple target 5G ProSe layer 3 end UEs via the same 5G ProSe direct link through the 5G ProSe layer 3 inter-UE relay UE, then the target end UE information, including the user information set as the target 5G ProSe end UE, will be included; and

[0365] f) If the UE acts as a 5G ProSe inter-UE relay 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 uses the 5G ProSe direct link to establish direct communication with only one target 5G ProSe end UE via the 5G ProSe inter-UE relay UE, then the target end UE information can include the user information set as the target 5G ProSe end UE.

[0366] In the ProSe direct link modification accept message.

[0367] If the PROSE DIRECT LINK MODIFICATION REQUEST message removes an existing ProSe application from a 5G ProSe direct link, the target UE will remove the ProSe identifier and the corresponding PQFI and PC5QoS parameters received in the PROSEDIRECT LINK MODIFICATION REQUEST message from the attribute set associated with the 5G ProSe direct link.

[0368] If the PROSE DIRECT LINK MODIFICATION REQUEST message removes an existing PC5 QoS flow from the PC5 5G ProSe direct link, the target UE will remove the PQFI and the corresponding PC5 QoS parameters from the attribute set associated with the 5G ProSe direct link.

[0369] 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 PROSEDIRECT LINK MODIFICATION ACCEPT message, the target UE will provide the added or modified PQFI and corresponding PC5 QoS parameters, as well as the PC5 link identifier, to the lower layer.

[0370] If the PROSE DIRECT LINK MODIFICATION REQUEST message is to remove an existing ProSe application or remove an existing PC5 QoS flow from a 5G ProSe direct link, then after sending the PROSE DIRECT LINK MODIFICATION ACCEPT message, the target UE will provide the removed PQFI and PC5 link identifier to the lower layer.

[0371] If the PROSE DIRECT LINK MODIFICATION REQUEST message establishes 5G ProSe UE-to-UE relay communication with an additional 5G ProSe layer 3 UE using the existing 5G ProSe direct link between the 5G ProSe layer 3 end UE and the 5G ProSe layer 3 UE-to-UE relay UE, then the target UE:

[0372] a) If acting as a 5G ProSe Layer 3 UE inter-UE relay UE, a 5G ProSe direct link establishment procedure will be performed on the target 5G ProSe Layer 3 UE as specified in Clause 7.2.2.2; and after receiving the PROSEDIRECT LINK ESTABLISHMENT ACCEPT message from the target 5G ProSe Layer 3 UE, a PROSE DIRECT LINK MODIFICATION ACCEPT message will be created.

[0373] b) If acting as a target 5G ProSe layer 3 UE, a PROSE DIRECT LINK MODIFICATIONACCEPT message will be created; and

[0374] c) In the PROSE DIRECT LINK MODIFICATION ACCEPT message, the target UE:

[0375] 1) If the UE acts as the target 5G ProSe layer 3 end UE:

[0376] i) Source UE information containing user information set as the source 5G ProSe layer 3 UE, and target UE information set as the target 5G ProSe layer 3 UE; and

[0377] ii) For Ethernet services, if the MAC address of the target 5G ProSe layer 3 UE changes, the MAC address of the target 5G ProSe layer 3 UE will be included.

[0378] 2) If the UE acts as a 5G ProSe Layer 3 inter-UE relay UE:

[0379] i) Target UE information containing user information set as the target 5G ProSe layer 3 UE;

[0380] ii) For IP services, it may include the target 5G ProSe layer 3 UE IP address IE, which is set as the IP address of the additional target 5G ProSe layer 3 UE; and

[0381] iii) For Ethernet services, the MAC address of the target 5G ProSe layer 3 UE will be included.

[0382] 3) May include PQFI and corresponding PC5 QoS parameters, optionally including the ProSe identifier of the PC5 QoS flow accepted by the target 5G ProSe layer 3 UE; and

[0383] 4) Packet filters that can include PC5 QoS rules to indicate PC5 QoS flows.

[0384] If the PROSE DIRECT LINK MODIFICATION REQUEST message establishes 5G ProSe UE-to-UE relay communication with an additional 5G ProSe layer 2 UE using the existing 5G ProSe direct link between the 5G ProSe layer 2 end UE and the 5G ProSe layer 2 UE-to-UE relay UE, then the target UE:

[0385] a) If acting as a 5G ProSe Layer 2 UE relay UE, a 5G ProSe direct link establishment procedure will be performed on the target 5G ProSe Layer 2 UE as specified in Clause 7.2.2.2; and after receiving the PROSEDIRECT LINK ESTABLISHMENT ACCEPT message from the target 5G ProSe Layer 2 UE, a PROSE DIRECT LINK MODIFICATIONACCEPT message will be created.

[0386] b) If acting as a target 5G ProSe layer 2 UE, a PROSE DIRECT LINK MODIFICATIONACCEPT message will be created; and

[0387] c) In the PROSE DIRECT LINK MODIFICATION ACCEPT message, the target UE:

[0388] 1) If the UE acts as the target 5G ProSe layer 2 end UE:

[0389] i) Source UE information containing user information set as the source 5G ProSe layer 2 end UE, and target UE information set as the target 5G ProSe layer 2 end UE; or

[0390] 2) If the UE acts as a 5G ProSe Layer 2 inter-UE relay UE:

[0391] i) Target UE information containing user information set as the target 5G ProSe layer 2 UE.

[0392] If the PROSE DIRECT LINK MODIFICATION REQUEST message is a 5G ProSe UE-to-UE relay communication released between a 5G ProSe Layer 3 end UE and a 5G ProSe Layer 3 UE-to-UE relay UE using a shared 5G ProSe direct link, then the target UE is:

[0393] a) If acting as a 5G ProSe Layer 3 inter-UE relay UE, one of the following procedures can be initiated to the target 5G ProSe Layer 3 UE:

[0394] 1) A 5G ProSe direct link release procedure, as specified in Clause 7.2.6.2, for releasing the 5G ProSe direct link with the peer 5G ProSe Layer 3 UE; or

[0395] 2) A 5G ProSe direct link modification procedure, as specified in Clause 7.2.3.2, is used to remove the corresponding PC5 QoS flow, provided that the UE determines to maintain a 5G ProSe direct link with the peer 5G ProSe Layer 3 UE; and

[0396] b) A PROSE DIRECT LINK MODIFICATION ACCEPT message will be created, and in this message, the target UE:

[0397] 1) If the UE acts as the target 5G ProSe layer 3 end UE, then the source UE information, which includes user information set as the source 5G ProSe layer 3 end UE, will be included; or

[0398] 2) If the UE acts as a 5G ProSe Layer 3 inter-UE relay UE, then the target UE information will be included, which contains the user information of the target 5G ProSe Layer 3 end UE.

[0399] If the 5G ProSe direct link is used for 5G ProSe direct communication between a 5G ProSe remote UE and a 5G ProSe Layer 3 UE to a 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 a network relay UE) performs QoS flow processing procedures as specified in Clauses 8.2.6.3.3 and 8.2.6.4.2.

[0400] If the relay reselection instruction is included in this message, the target UE will ignore the value of the link modification operation code IE.

[0401] If the PROSE DIRECT LINK MODIFICATION REQUEST message is accepted by the target 5G ProSe UE to trigger inter-UE relay reselection, and a 5G PC5 direct link exists between the 5G ProSe inter-UE relay UE and the target 5G ProSe UE, then the target UE acting as the target 5G ProSe UE may execute the candidate 5G ProSe inter-UE relay discovery procedure as specified in Clause 8a.2.3.3. If such a PC5 unicast link does not already exist, the target UE shall establish a PC5 unicast link with the selected new 5G ProSe inter-UE relay UE.

[0402] If the PROSE DIRECT LINK MODIFICATION REQUEST message is accepted to trigger negotiated 5G ProSe Layer 3 UE-to-UE trunk reselection, the target UE will respond with the PROSE DIRECT LINK MODIFICATION ACCEPT message. In this message:

[0403] a) If the target UE acts as the target 5G ProSe layer 3 end UE, and the 5G ProSe direct link is between the target 5G ProSe layer 3 end UE and the relay UE between the 5G ProSe layer 3 UE, then the target UE:

[0404] 1) Will include trunk reselection instructions;

[0405] 2) It will include the latest selected 5G ProSe UE-to-UE relay UE user information ID;

[0406] 3) It will include the IP address of the UE initiating the 5G ProSe; and

[0407] 4) If IP communication is used, it will include the target 5G ProSe end UE IP address used with the most recently selected 5G ProSe UE-to-UE relay UE; and

[0408] b) If the target 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 source 5G ProSe Layer 3 UE, then after receiving the PROSEDIRECT LINK MODIFICATION ACCEPT message from the target 5G ProSe Layer 3 UE, the target UE:

[0409] 1) Will include a trunk reselection instruction;

[0410] 2) It will include the latest selected 5G ProSe UE-to-UE relay UE user information ID;

[0411] 3) Will include the target 5G ProSe end UE IP address; and

[0412] 4) If IP communication is used, the target 5G ProSe end UE IP address will be included for use with the latest selected 5G ProSe UE-to-UE relay UE.

[0413] If the PROSE DIRECT LINK MODIFICATION REQUEST message is accepted to trigger negotiated 5G ProSe Layer 2 UE-to-UE relay reselection, the target UE acting as the target 5G ProSe Layer 2 end UE will respond with the PROSE DIRECT LINK MODIFICATION ACCEPT message. In this message:

[0414] a) Will include a relay reselection instruction;

[0415] b) Will include the new 5G ProSe UE-to-UE relay UE user information ID; and

[0416] c) A new LBS containing the KNRP ID.

[0417] After generating the PROSE DIRECT LINK MODIFICATION ACCEPT message, the target UE passes this message, along with the Layer 2 ID of the initiating UE for 5G ProSe direct communication and the Layer 2 ID of the target UE for 5G ProSe direct communication, to the lower layer for transmission.

[0418] If this procedure is performed for negotiated 5G ProSe Layer 3 UE-to-UE relay reselection, the target UE should start timer T5096. While timer T5096 is running, the target UE should not send a new PROSE DIRECT LINKMODIFICATION ACCEPT message to the same initiating UE.

[0419] 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.

[0420] The target UE will form a new KNRP ID from the new MSB of the KNRP ID received from the PROSE DIRECT LINK MODIFICATION REQUEST message and the new LSB of the KNRP ID contained in the PROSE DIRECT LINK MODIFICATION ACCEPT message. The target UE will replace the existing KNRP ID with the new KNRP ID. The target UE may include the new KNRP ID in the DIRECTLINK ESTABLISHMENT REQUEST message to the initiating UE, as specified in Clause 7.2.2.2.

[0421] 7.2.3.4 5G ProSe Direct Link Modification Procedure Completed by the Initiating UE

[0422] Upon receiving the PROSE DIRECT LINK MODIFICATION ACCEPT message, the initiating UE will stop timer T5081.

[0423] Upon receiving the PROSE DIRECT LINK MODIFICATION ACCEPT message, if the PROSE DIRECTLINK MODIFICATION REQUEST message is for adding a new ProSe application, adding a new PC5 QoS flow, or modifying any existing PC5 QoS flow in the 5G ProSe direct link, the initiating UE will provide the added or modified PQFI, the corresponding PC5 QoS parameters, and the PC5 link identifier to the lower layer.

[0424] Upon receiving the PROSE DIRECT LINK MODIFICATION ACCEPT message, if the PROSE DIRECTLINK MODIFICATION REQUEST message is to remove an existing ProSe application or remove an existing PC5 QoS flow from the 5G ProSe direct link, the UE will provide the removed PQFI and PC5 link identifier to the lower layer.

[0425] Upon receiving the PROSE DIRECT LINK MODIFICATION ACCEPT message, if the initiating UE acts as a 5G ProSe Layer 3 inter-UE relay UE and the PROSE DIRECT LINK MODIFICATION REQUEST message will establish 5G ProSe inter-UE relay communication with the additional 5G ProSe Layer 3 UE using the existing 5G ProSe direct link between the 5G ProSe Layer 3 end UE and the 5G ProSe Layer 3 inter-UE relay UE, then the initiating UE should send a PROSEDIRECT LINK ESTABLISHMENT ACCEPT message to the source 5G ProSe Layer 3 end UE, as specified in Clause 7.2.2.3.

[0426] Upon receiving the PROSE DIRECT LINK MODIFICATION ACCEPT message, if the initiating UE acts as a 5G ProSe Layer 3 inter-UE relay UE and the PROSE DIRECT LINK MODIFICATION REQUEST message will add a new PC5 QoS flow or modify any existing PC5 QoS flow in the existing 5G ProSe direct link or remove any PC5 QoS flow from the existing 5G ProSe direct link between the 5G ProSe Layer 3 end UE and the 5G ProSe Layer 3 inter-UE relay UE, 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.

[0427] When a 5G ProSe direct link is between the source 5G ProSe UE and the 5G ProSe UE relay UE, after receiving the PROSE DIRECT LINK MODIFICATION ACCEPT message containing a relay reselection indication and the PROSE DIRECT LINK MODIFICATION REQUEST message for negotiating the 5G ProSe UE relay reselection, the initiating UE acting as the source 5G ProSe UE should establish a PC5 unicast link with the newly selected 5G ProSe UE relay UE. The user information ID of the newly selected 5G ProSe UE relay UE is included in the PROSE DIRECT LINK MODIFICATION ACCEPT message, provided that such a PC5 unicast link no longer exists. If the initiating UE acts as the source 5G ProSe Layer 3 UE, the initiating UE will create a PROSE DIRECT LINK MODIFICATION ACK message. In this message, the initiating UE:

[0428] a) If IP communication is used, the source UE IP address for the new relay IE will be included, which is set as the IP address of the source 5G ProSe Layer 3 UE and will be used with the newly selected 5G ProSe Layer 3 UE as the relay IE, and the target UE IP address IE will be set as the IP address of the target 5G ProSe Layer 3 UE.

[0429] When a 5G ProSe direct link is established between a 5G ProSe Layer 3 UE relay UE and a target 5G ProSe Layer 3 UE, and the 5G ProSe Layer 3 UE relay UE receives a PROSEDIRECT LINK MODIFICATION ACK message containing a relay reselection indication from the source 5G ProSe UE, the 5G ProSe Layer 3 UE relay UE should create a PROSE DIRECTLINK MODIFICATION ACK message. In this message, the 5G ProSe Layer 3 UE relay UE:

[0430] a) If IP communication is used, the source UE IP address for the new relay IE will include the relay reselection indication, the source UE IP address set to the IP address of the source 5G ProSe layer 3 UE that will be used with the newly selected 5G ProSe layer 3 UE relay IE, and the source UE IP address IE set to the IP address of the source 5G ProSe layer 3 UE.

[0431] Upon receiving a PROSE DIRECT LINK MODIFICATION ACCEPT message containing a trunk reselection indication, if the PROSE DIRECT LINK MODIFICATION REQUEST message is used for trunk reselection, the initiating UE should form a new KNRP ID from the MSB of the KNRP ID included in the PROSE DIRECT LINK MODIFICATION REQUEST message and the LSB of the KNRP ID received in the PROSE DIRECT LINK MODIFICATION ACCEPT message. The initiating UE will replace the existing KNRP ID with the new KNRP ID. When the initiating UE reconnects with the same target UE, the initiating UE may include the new KNRP ID in the PROSE DIRECT LINK ESTABLISHMENT REQUEST message with the target UE, as specified in Clause 7.2.2.2.

[0432] After generating the PROSE DIRECT LINK MODIFICATION ACK message, the initiating UE transmits this message, along with the Layer 2 ID of the initiating UE used for 5G ProSe direct communication and the Layer 2 ID of the target UE used for 5G ProSe direct communication, to the lower layer for transmission.

[0433] If the source UE confirms acceptance of the 5G ProSe direct link modification, the source UE begins receiving and / or transmitting services via the newly selected 5G ProSe inter-UE relay UE.

[0434] If the 5G ProSe direct link modification procedure is used for 5G ProSe direct communication between a 5G ProSe Layer 3 UE relay UE and a target 5G ProSe Layer 3 UE for Ethernet services, and the PROSE DIRECT LINK MODIFICATIONACCEPT message contains the MAC address of the target 5G ProSe Layer 3 UE, and the initiating UE acting as the 5G ProSe Layer 3 UE relay detects that the MAC address of the target 5G ProSe Layer 3 UE is not unique, i.e., the MAC address of the target 5G ProSe Layer 3 UE is also provided by another 5G ProSe Layer 3 UE in the existing ProSe 5G direct link, then the 5G ProSe Layer 3 UE relay UE shall execute the 5G ProSe direct link release procedure as specified in Clause 7.2.6.

[0435] 7.2.3.4a 5G ProSe direct link modification procedure completed by the target UE

[0436] Upon receiving the PROSE DIRECT LINK MODIFICATION ACK message, the target layer 3 5G ProSe end UE begins to receive services, transmit services, or perform both via the newly selected 5G ProSe inter-UE relay UE, and will stop T5096.

[0437] Upon receiving the PROSE DIRECT LINK MODIFICATION ACK message, the Layer 3 5G ProSe inter-UE relay UE will stop T5096.

[0438] 7.2.3.5 5G ProSe Direct Link Modification Procedure Not Accepted by the Target UE

[0439] If the 5G ProSe direct link modification request cannot be accepted, the target UE should send a PROSE DIRECT LINK MODIFICATION REJECT message. The PROSE DIRECT LINK MODIFICATION REJECT message contains a PC5 signaling protocol reason IE set to one of the following reason values:

[0440] #5 Lack of resources for 5G ProSe direct links;

[0441] #6 The required service is not allowed;

[0442] #12 Inconsistent security policies;

[0443] #16 Lack of local capabilities;

[0444] #20 Fault originating from the 5G ProSe UE;

[0445] #23 MAC addresses are not unique;

[0446] #24 Relay UE was not selected for link establishment with integrated discovery; or

[0447] #111 Unspecified protocol error.

[0448] If the target UE is not allowed to accept this request, for example because the operator policy or configuration parameters for ProSe communication on PC5 as specified in Clause 5.2.4 do not allow the ProSe application to be added, the target UE will send a PROSE DIRECT LINK MODIFICATION REJECT message with PC5 signaling protocol reason value #6 "Required service not allowed".

[0449] If the target UE is a 5G ProSe Layer 3 UE to network relay UE, then the PDU session used for relay service is a LADNPDU session and:

[0450] a) The target UE is outside the LADN service area; or

[0451] b) 5G ProSe direct link modification requires a PDU session modification procedure that fails due to receiving the 5GSM cause value #46 "outside LADN service area" in the PDU SESSION MODIFICATION REJECT message, as specified in Clause 6.4.2.4.1 of 3GPP TS 24.501

[11] ;

[0452] The target UE will send a PROSE DIRECTLINK MODIFICATION REJECT message with the PC5 signaling protocol reason value #111 "Unspecified protocol error".

[0453] If the 5G ProSe direct link modification fails due to congestion or other temporary lower-layer issues causing resource constraints, the target UE will send a PROSE DIRECT LINK MODIFICATION REJECT message with PC5 signaling protocol reason value #5 "Lack of resources for 5G ProSe direct link".

[0454] If the target UE, acting as the target 5G ProSe end UE, receives one or more direct link modification requests or direct link establishment requests for establishing an end-to-end connection with the source 5G ProSe end UE and uses integration discovery, the target UE will select a 5G ProSe inter-UE relay UE and send a PROSE DIRECT LINK MODIFICATION REJECT message with PC5 signaling protocol reason value #24 "Relay UE not selected for link establishment with integration discovery" to the 5G ProSe inter-UE relay UE that was not selected and has sent a PROSE DIRECT LINK MODIFICATION REQUEST message.

[0455] If the link modification operation code is set to "Associate the new ProSe application with the existing PC5 QoS flow", and the security policy corresponding to the ProSe identifier is inconsistent with the security policy applied to the existing 5G ProSe direct link, the target UE will send a PROSE DIRECT LINKMODIFICATION REJECT message with PC5 signaling protocol reason value #12 "Security policy inconsistency".

[0456] If a link modification operation requires the addition of a new PC5 QoS flow, but the target UE cannot support the additional packet filters required on the target UE's existing PDU session, the target UE will send a PROSE DIRECT LINK MODIFICATION REJECT message with the PC5 signaling protocol reason value #16 "Lack of local capability".

[0457] If the target UE acts as the target 5G ProSe end UE, and the 5G ProSe direct link modification procedure is between the 5G ProSe UE relay UE and the target 5G ProSe end UE, then the target 5G ProSe end UE can include the source UE information IE in the PROSE DIRECT LINK MODIFICATION REJECT message, which is set to the user information of the source 5G ProSe end UE that initiated the 5G ProSe direct link establishment procedure.

[0458] If the target UE acts as a 5G ProSe inter-UE relay UE, the 5G ProSe direct link establishment procedure is between the source 5G ProSe UE and the 5G ProSe inter-UE relay UE, and the target 5G ProSe UE has rejected the 5G ProSe direct link establishment procedure or the 5G ProSe direct link modification procedure, then the 5G ProSe inter-UE relay UE will send a PROSE DIRECT LINKMODIFICATION REJECT message with the PC5 signaling protocol reason value #20 "Fault from 5G ProSe UE" to the source 5G ProSe UE. The 5G ProSe inter-UE relay UE may include in the PROSE DIRECT LINKMODIFICATION REJECT message a PC5 UE fault reason IE set to the PC5 signaling protocol reason received from the target 5G ProSe UE that has rejected the 5G ProSe direct link establishment procedure, as specified in Clause 7.2.2.5. The 5GProSe UE-to-UE relay UE can include the target UE information (IE) in the PROSE DIRECT LINK MODIFICATION REJECT message, which is set to the user information of the target 5G ProSe UE that has rejected the 5G ProSe direct link establishment procedure.

[0459] For other reasons that cause link establishment failure, the target UE will send a PROSE DIRECT LINK MODIFICATION REJECT message with PC5 signaling protocol reason value #111 "Unspecified protocol error".

[0460] Upon receiving the PROSE DIRECT LINK MODIFICATION REJECT message, the initiating UE will stop timer T5081 and abort the 5G ProSe direct link modification procedure. If the PC5 signaling protocol reason value in the PROSE DIRECT LINK MODIFICATION REJECT message is #11 "Required service not allowed", #5 "Lack of resources for 5G ProSe direct link", or #12 "Security policy inconsistency", the initiating UE should not attempt to initiate 5G ProSe direct link modification with the same target UE to add the same ProSe application, or at least add or modify the same PC5 QoS flow within the time period T.

[0461] Note: The length of time period T is specific to the UE implementation scheme and may vary depending on whether the UE receives PC5 signaling protocol reason value #11 "Required service not allowed", PC5 signaling protocol reason value #5 "Lack of resources for 5G ProSe direct link", or PC5 signaling protocol reason value #12 "Security policy inconsistency". The length of time period T is not less than 30 minutes.

[0462] If the 5G ProSe direct link establishment procedure is used for 5G ProSe direct communication between the source 5G ProSe layer 3 UE and the 5G ProSe layer 3 UE relay UE for Ethernet services, and the PROSE DIRECT LINK MODIFICATIONREQUEST message contains the MAC address of the source 5G ProSe layer 3 UE, and the target UE acting as the 5G ProSe layer 3 UE relay UE detects that the MAC address of the source 5G ProSe layer 3 UE is not unique, that is, the MAC address of the source 5G ProSe layer 3 UE is also provided by another 5G ProSe layer 3 UE in the existing ProSe 5G direct link, then the 5G ProSe layer 3 UE relay UE will send a PROSEDIRECT LINK MODIFICATION REJECT message containing the PC5 signaling protocol reason value #23 "MAC address is not unique" to the source 5G ProSe layer 3 UE.

[0463] If the 5G ProSe direct link establishment procedure is used for 5G ProSe direct communication between the source 5G ProSe layer 3 UE and the 5G ProSe layer 3 UE relay UE for Ethernet services, and the target UE, acting as the 5G ProSe layer 3 UE relay UE, releases the 5G ProSe direct link between the 5G ProSe layer 3 UE relay UE and the target 5G ProSe layer 3 UE, and the PC5 signaling protocol reason value is #23 "MAC address is not unique", then the 5G ProSe layer 3 UE relay UE will send a PROSE DIRECTLINK MODIFICATION REJECT message containing the PC5 signaling protocol reason value #111 "unspecified protocol error" to the source 5G ProSe layer 3 UE.

[0464] 7.2.3.6 Abnormal situations

[0465] 7.2.3.6.1 Abnormal situations at the UE initiation point

[0466] The following abnormal situations can be identified:

[0467] a) If timer T5081 expires, the initiating UE will retransmit the PROSE DIRECT LINK MODIFICATION REQUEST message and restart timer T5081. After reaching the maximum allowed number of retransmissions, the initiating UE should abort the 5G ProSe direct link modification procedure and may notify the upper layer that the target UE is unreachable.

[0468] Note 1: The maximum number of retransmissions allowed is specific to the UE implementation.

[0469] Note 2: Whether the initiating UE releases this 5G ProSe direct link after the maximum number of allowed retransmissions has been reached depends on its implementation scheme.

[0470] b) For the same 5G ProSe direct link, if the initiating UE receives a PROSE DIRECT LINK RELEASE REQUEST message after initiating the 5G ProSe direct link modification procedure, the initiating UE will stop timer T5081, terminate the 5G ProSe direct link modification procedure, and continue the 5G ProSe direct link release procedure.

[0471] c) For the same 5G ProSe direct link, if the initiating UE receives a PROSE DIRECT LINK MODIFICATION REQUEST message during the 5G ProSe direct link modification procedure, the initiating UE will stop timer T5081 and abort the 5G ProSe direct link modification procedure. The following processing depends on the implementation scheme; for example, if still necessary, the initiating UE will wait for the implementation scheme-dependent time for initiating a new 5G ProSe direct link modification procedure.

[0472] Note 3: Timer values ​​that depend on the implementation scheme need to be set to avoid further conflicts (e.g., random timer values).

[0473] 7.2.3.6.2 Abnormal situations at the target UE

[0474] The following abnormal situations can be identified:

[0475] a) For the same 5G ProSe direct link, if the target UE receives a PROSE DIRECT LINK RELEASE REQUEST message during the 5G ProSe direct link modification procedure, the target UE will stop all running timers for this 5G ProSe direct link, terminate the 5G ProSe direct link modification procedure, and continue the 5G ProSe direct link release procedure.

[0476] [...]

[0477] 7.2.6.2 5G ProSe Direct Link Release Procedure Initiated by the UE

[0478] If a request is received from the upper layer to release the 5G ProSe direct link of the target UE with a known Layer 2 ID (for unicast communication), and there is an existing 5G ProSe direct link between the two UEs, the initiating UE will initiate the procedure.

[0479] If the target UE does not respond, for example, in the 5G ProSe direct link modification procedure, 5G ProSe direct link identifier update procedure, 5G ProSe direct link key update procedure, or 5G ProSe direct link keep-alive procedure, the initiating UE can initiate the procedure.

[0480] If the UE has reached the maximum number of established 5G ProSe direct links and needs to establish new 5G ProSe direct links, the initiating UE can initiate a procedure to release the established 5G ProSe direct links. In this case, which 5G ProSe direct link to release depends on the UE's implementation scheme.

[0481] The UE can initiate a procedure to release the established 5G ProSe direct link after the timer T5084 expires.

[0482] if:

[0483] a) Initiating the UE to act as a 5G ProSe Layer 3 UE to a network relay UE; and

[0484] b) By initiating a UE or network release of a PDU session established for relaying services to the target UE, as specified in Clause 6.3.3 or Clause 6.4.3 of 3GPP TS24.501

[11] ;

[0485] The UE should initiate the 5G ProSe direct link release procedure.

[0486] If the initiating UE acting as a 5G ProSe Layer 3 UE to a network relay UE establishes a new PDU session after receiving the 5GSM cause value #39 "Request Reactivation", as specified in Clause 6.3.2.3 of 3GPP TS 24.501

[11] , then the UE may initiate a 5G ProSe direct link release procedure.

[0487] If the initiating UE is a 5G ProSe Layer 3 UE to a network relay UE, then the PDU session used for relay service is a LADNPDU session and:

[0488] a) The UE is outside the LADN service area; or

[0489] b) The UE receives the 5GSM cause value #46 “outside LADN service area” in the PDU SESSION MODIFICATION REJECT message, as specified in Clause 6.4.2.4.1 of 3GPP TS 24.501

[11] .

[0490] If at least one 5G ProSe Layer 3 remote UE is serving on the PDU session, then the UE should initiate the 5G ProSe direct link release procedure.

[0491] if:

[0492] a) Initiating the UE to act as a 5G ProSe Layer 2 remote UE or a 5G ProSe Layer 3 remote UE for relaying with N3IWF support; and

[0493] b) Initiate UE to be in 5GMM-IDLE mode;

[0494] The UE can initiate the 5G ProSe direct link release procedure.

[0495] if:

[0496] a) Initiating the UE to act as a 5G ProSe Layer 2 remote UE, a 5G ProSe Layer 3 remote UE, or a 5G ProSe Layer 2 UE to a network relay UE; and

[0497] b) Upon receiving the configuration parameters for 5G ProSe UE to network relay, revoke the service authorization for the initiating UE to act as a 5G ProSe Layer 2 remote UE, a 5G ProSe Layer 3 remote UE, or a 5G ProSe Layer 2 UE to network relay UE, as specified in Clause 5.2.5;

[0498] The UE should initiate the 5G ProSe direct link release procedure.

[0499] if:

[0500] a) Initiating the UE to act as a 5G ProSe Layer 3 UE to a network relay UE; and

[0501] b) Upon receiving the configuration parameters for 5G ProSe UE-to-network relay, revoke the service authorization for the initiating UE to act as a 5G ProSe Layer 3 UE-to-network relay UE in the serving PLMN, as specified in Clause 5.2.5;

[0502] The initiating UE shall initiate a 5G ProSe direct link release procedure and release the PDU session established for the service of the relay target UE, as specified in Clause 6.4.3 of 3GPP TS 24.501

[11] .

[0503] if:

[0504] a) Initiate the UE to act as a 5G ProSe Layer 3 UE to a network relay UE;

[0505] b) Establish a 5G ProSe direct link with RSC specifically designed for emergency services; and

[0506] c) As specified in 3GPP TS 24.501

[11] , the initiating UE participates in its own emergency services and, due to local regulations or implementation of specific requirements, the initiating UE decides to prioritize its own emergency services;

[0507] The initiating UE will initiate a 5G ProSe direct link release procedure and release the PDU session established for the service of the relay target UE, as specified in Clause 6.4.3 of 3GPP TS 24.501

[11] .

[0508] if:

[0509] a) Initiating the UE to act as a 5G ProSe end UE or a 5G ProSe UE relay UE; and

[0510] b) Upon receiving the configuration parameters for 5G ProSe UE-to-UE relay, revoke the service authorization for the initiating UE to act as a 5G ProSe end UE or a 5G ProSe UE-to-UE relay UE, as specified in Clause 5.2.7;

[0511] The UE should initiate the 5G ProSe direct link release procedure.

[0512] if:

[0513] a) Initiating the UE to act as a 5G ProSe Layer 3 inter-UE relay UE;

[0514] b) The direct link between the 5G ProSe layer 3 UE and the initiating UE has been released; and

[0515] c) There are one or more direct links between the initiating UE and the peer 5G ProSe layer 3 end UE, with PC5 QoS flows used only for communication with the 5G ProSe layer 3 end UE;

[0516] The initiating UE can initiate a 5G ProSe direct link release procedure to a peer 5G ProSe layer 3 UE.

[0517] if:

[0518] a) Initiating the UE to act as a 5G ProSe Layer 3 inter-UE relay UE;

[0519] b) Receiving a PROSE DIRECT LINK MODIFICATION REQUEST message from a 5G ProSe layer 3 UE to release 5G ProSe UE-to-UE relay communication with one of the peer 5G ProSe layer 3 UEs; and

[0520] c) The 5G ProSe direct link between the initiating UE and the target peer 5G ProSe layer 3 UE has a PC5 QoS flow used only for communication with the 5G ProSe layer 3 UE;

[0521] The initiating UE can initiate a 5G ProSe direct link release procedure to the target peer 5G ProSe layer 3 UE.

[0522] For 5G ProSe layer 2 UE inter-relay, if:

[0523] a) Initiate the UE to act as a 5G ProSe layer 2 UE;

[0524] b) The initiating UE has released the end-to-end 5G ProSe direct link between the initiating UE and its peer 5G ProSe layer 2 UE; and

[0525] c) The 5G ProSe direct link between the initiating UE and the 5G ProSe layer 2 UE relay UE has a PC5 QoS flow used only for end-to-end communication between the initiating UE and its peer 5G ProSe layer 2 UE;

[0526] The initiating UE can initiate a 5G ProSe direct link release procedure to a 5G ProSe layer 2 UE inter-UE relay UE.

[0527] If the 5G ProSe direct link is used for 5G ProSe layer 3 UE-to-UE relay UE and target 5G ProSe layer 3 end UE for 5G ProSe direct communication for Ethernet services, and the initiating UE acting as the 5G ProSe layer 3 UE-to-UE relay UE detects that the MAC address of the 5G ProSe layer 3 end UE is not unique, that is, the MAC address of the target 5G ProSe layer 3 end UE is also provided by another 5G ProSe layer 3 end UE in the existing ProSe 5G direct link, then the 5G ProSe layer 3 UE-to-UE relay UE will send a PROSEDIRECT LINK RELEASE REQUEST message containing the PC5 signaling protocol reason value #23 "MAC address is not unique" to the target 5G ProSe layer 3 end UE.

[0528] [...]

[0529] 10.3.2 ProSe Direct Link Establishment and Acceptance

[0530] 10.3.2.1 Message Definition

[0531] This message is sent by one UE to another peer UE to accept the received PROSE DIRECT LINKESTABLISHMENT REQUEST message. See Table 10.3.2.1.1.

[0532] Message type: PROSE DIRECT LINK ESTABLISHMENT ACCEPT

[0533] Significance: Double

[0534] Direction: UE to peer UE

[0535] Table 10.3.2.1.1 of 3GPP TS 23.554 V18.8.0, titled "Prose Direct Link Estimate Access Message Content", is reproduced as follows: Figure 9 ]

[0536] 10.3.6 ProSe Direct Link Modification Request

[0537] 10.3.6.1 Message Definition

[0538] This message is sent by the UE to another peer UE to initiate a direct link modification procedure. See Table 10.3.6.1.1.

[0539] Message type: PROSE DIRECT LINK MODIFICATION REQUEST

[0540] Significance: Double

[0541] Direction: UE to peer UE

[0542] Table 10.3.6.1.1 of 3GPP TS 23.554 V18.8.0, titled "PROSE DIRECT LINK MODIFICATIONREQUEST Message Content", is reproduced as follows: Figure 10 ]

[0543] 10.3.14 ProSe Direct Link Security Mode Completed

[0544] 10.3.14.1 Message Definition

[0545] This message is sent by one UE to another peer UE in response to the PROSE DIRECT LINK SECURITY MODECOMMAND message. See Table 10.3.14.1.1.

[0546] Message type: PROSE DIRECT LINK SECURITY MODE COMPLETE

[0547] Significance: Double

[0548] Direction: UE to peer UE

[0549] Table 10.3.14.1.1 of 3GPP TS 23.554 V18.8.0, titled "PROSE DIRECT LINK SECURITY MODE COMPLETE Message Content", is reproduced as follows: Figure 11 ]

[0550] Version 18 specifies inter-UE (U2U) relay. If an end UE cannot communicate directly with its peer UE, a relay UE can be used to support connectivity between the end UE and its peer UE. The first end UE (i.e., the source (5G ProSe) end UE) can trigger a Layer 2 link establishment procedure (as introduced in, for example, Clause 6.7 of 3GPP TS 23.304) to support inter-UE relay communication between the first end UE and the second end UE (i.e., the target (5G ProSe) end UE) via the (5G ProSe inter-UE) relay UE. The relay UE can establish a PC5 direct link with the source end UE (e.g., on the first PC5 hop) and a PC5 direct link with the target end UE (e.g., on the second PC5 hop). In 3GPP TS 23.304, two types of Layer 2 link establishment procedures are specified. For Layer 2 link establishment procedures without integrated discovery, the source end UE can first execute a separate 5G ProSe inter-UE relay discovery procedure. The source UE can then send a Direct Communication Request (DCR) message to the target UE via a specific relay UE, whose Layer 2 ID (L2ID) and user information ID have been received from the latest discovery procedure.

[0551] On the other hand, if a Layer 2 link establishment procedure can be initiated to any relay UE and / or if the source UE has not yet discovered any relay UE, a Layer 2 link establishment procedure with integrated discovery can be used. More specifically, the first-end UE broadcasts a Direct Communication Request (DCR) message containing relay_indication. The relay_indication in the DCR indicates whether the relay UE can forward the DCR message. After receiving a DCR message with relay_indication from the first-end UE, the relay UE can decide to participate in the procedure and broadcast a DCR message in its vicinity (i.e., on the second hop) even without relay_indication. In response to receiving the DCR message, which contains the same source user information, ProSe identifier, and relay service code (RSC) 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 UE via. Subsequently, the target UE establishes security on the second hop and sends a Direct Communication Acceptance (DCA) to the selected relay UE to complete the Layer 2 link establishment on the second hop. In response to receiving a DCA message on the second hop, the relay UE establishes security on the first hop and sends a DCA to the source UE to complete the layer 2 link establishment on the first hop.

[0552] During the link establishment process, if the data unit type used for communication is Ethernet, the MAC addresses of the source UE and the destination UE are exchanged via the relay UE. Figure 12 and Figure 13 Procedures for exchanging MAC addresses with and without integrated discovery are shown respectively. Figure 12 The illustration shows MAC address switching in a relay communication scenario without integrated discovery, according to an exemplary embodiment. Figure 13 The illustration shows MAC address switching in a relay communication scenario with integrated discovery, according to an exemplary embodiment.

[0553] As specified in Clause 7.2.2 of 3GPP TS 24.554, the relay UE will detect Ethernet MAC address conflicts. For example, when the relay UE detects that the MAC address of the source UE in the PROSE DIRECT LINK SECURITY MODE COMPLETE message is not unique (i.e., the MAC address of the source UE is also provided by another UE in the existing ProSe 5G direct link), the relay UE will send a PROSE DIRECT LINK ESTABLISHMENT REJECT message containing the PC5 signaling protocol reason value #23 "MAC address is not unique" to the source UE. As another example, when the relay UE detects that the MAC address of the target UE in the PROSEDIRECT LINK ESTABLISHMENT ACCEPT message is not unique, the relay UE will initiate a 5G ProSe direct link release procedure for the target UE and send a PROSE DIRECT LINK ESTABLISHMENT REJECT message containing the PC5 signaling protocol reason value #111 "Unspecified protocol error" to the source UE.

[0554] It should be noted that in the case of a link establishment procedure with integrated discovery, when the relay UE detects that the MAC address of the source UE in the PROSEDIRECT LINK SECURITY MODE COMPLETE message is not unique and sends a PROSE DIRECT LINKESTABLISHMENT REJECT message containing the PC5 signaling protocol reason value #23 "MAC address is not unique" to the source UE, a direct link (i.e., the second hop) between the relay UE and the target UE is established. However, no other actions are specified related to this established direct link. Without additional procedures, the direct link context can still be stored in the target UE, causing the target UE to continue waiting for service on this link. This behavior appears unnecessary and / or unintended. Figure 14 The above problem is illustrated. To resolve this problem, some possible solutions can be considered.

[0555] For example, when a relay UE detects a MAC address conflict, it can send a PROSEDIRECT LINK RELEASE REQUEST to the target UE. The PROSEDIRECT LINK RELEASE REQUEST message can contain the PC5 signaling protocol reason value #111 "Unspecified protocol error". Upon receiving this message, the target UE can delete the associated direct link context and notify the lower-layer associated PC5 link that it has been released. Figure 15 The proposed method is shown.

[0556] Here is the text recommendation from 3GPP TS 24.554:

[0557]

[0558] Figure 16 This is flowchart 1600 for a relay user equipment (UE). In step 1605, the relay UE establishes a direct link with the second-end UE to support UE-to-UE (U2U) relay communication between the first-end UE and the second-end UE via the relay UE. In step 1610, the relay UE sends a first message to the first-end UE to trigger the establishment of security between the first-end UE and the relay UE. In step 1615, the relay UE receives a second message from the first-end UE to establish a security context between the relay UE and the first-end UE, wherein the first message contains the media access control (MAC) address of the first-end UE. In step 1620, in response to detecting that the MAC address of the first-end UE is not unique, the relay UE executes a procedure to release the direct link.

[0559] In one embodiment, in response to detecting that the MAC address of the first UE is not unique, the relay UE may send a third message to the second UE to release the direct link. The relay UE may receive a link establishment request message from the first UE, wherein the request message is for 5G ProSe inter-UE relay communication with integrated discovery. In one embodiment, the request message may include relay_indication. The request message may not contain information for identifying any inter-UE relay.

[0560] In one embodiment, in response to detecting that the MAC address of the first UE is not unique, the relay UE may send a fourth message to the first UE to reject the link establishment procedure between the relay UE and the first UE. In one embodiment, the third / fourth message may contain a reason value or information indicating that the MAC address of the first UE is not unique. The first message may be a PROSE DIRECT LINK SECURITY MODE COMMAND message. The second message may be a PROSE DIRECT LINK SECURITY MODE COMPLETE message. The third message may be a PROSE DIRECT LINK RELEASEREQUEST message. The fourth message may be a PROSE DIRECT LINK ESTABLISHMENT REJECT message.

[0561] In one embodiment, the request message can be a direct communication request message or a PROSE DIRECT LINKESTABLISHMENT REQUEST message. The direct link can be a PC5 connection, a PC5-S connection, a PC5-RRC connection, or a Layer 2 link.

[0562] In one embodiment, the first UE can be a source 5G ProSe (Layer 3) UE. The second UE can be a target 5G ProSe (Layer 3) UE. The relay UE can be an inter-UE relay UE of 5G ProSe (Layer 3). The procedure for releasing the direct link can be a 5G ProSe direct link release procedure.

[0563] Return to reference Figure 3 and 4 In an exemplary embodiment from the perspective of the relay UE, the relay UE 300 includes program code 312 stored in memory 310. CPU 308 can execute program code 312 to enable the relay UE to (i) establish a direct link with a second-end UE to support U2U relay communication between the first-end UE and the second-end UE via the relay UE, (ii) send a first message to the first-end UE to trigger a security establishment between the first-end UE and the relay UE, (iii) receive a second message from the first-end UE to establish a security context between the relay UE and the first-end UE, wherein the first message contains the MAC address of the first-end UE, and (iv) execute a procedure to release the direct link in response to detecting that the MAC address of the first-end UE is not unique. Furthermore, CPU 308 can execute program code 312 to perform all the above actions and steps or other actions and steps described herein.

[0564] On the other hand, in the case of a link establishment procedure with integrated discovery, according to the current specification, the target UE may not receive the source UE's MAC address via the relay UE. This is because the relay UE continues to receive the source UE's MAC address until it receives the PROSE DIRECT LINK SECURITY MODE COMPLETE message, which occurs after the link between the relay UE and the target UE has been established. To provide lost information (e.g., the source UE's MAC address), the relay UE may additionally include the source UE's MAC address in the link modification procedure for the target UE after receiving the source UE's MAC address. The source UE's MAC address may be included in the information element of the signaling sent within the link modification procedure (e.g., a link modification request message or a PROSE DIRECT LINK MODIFICATION REQUEST message). Figure 17 The proposed possible methods are shown.

[0565] As introduced in Clause 6.7.3.2 of 3GPP TS 23.304, a link modification procedure between the relay UE and the target UE is performed after the security mode control procedure between the source UE and the relay UE is completed (and before the DCA message is sent to the source UE). In this link modification procedure, the relay UE provides the target UE with PC5 Quality of Service (QoS) information on the second hop. However, it is acceptable to alternatively provide the target UE with the source UE's MAC address along with the PC5 QoS information on the second hop. For example, in addition to the PC5 QoS information on the second hop, the link modification request message of the link modification procedure between the relay UE and the target UE may also include the source UE's MAC address. Figure 18 Alternative solutions can be shown.

[0566] Here is the text recommendation from 3GPP TS 24.554:

[0567]

[0568] Figure 19This is flowchart 1900 for a relay user equipment (UE). In step 1905, the relay UE establishes a direct link with the second-end UE to support U2U relay communication between the first-end UE and the second-end UE via the relay UE. In step 1910, the relay UE sends a first message to the first-end UE to trigger the establishment of a security connection between the first-end UE and the relay UE. In step 1915, the relay UE receives a second message from the first-end UE to establish a security context between the relay UE and the first-end UE, wherein the second message contains the MAC address of the first-end UE. In step 1920, in response to receiving the MAC address of the first-end UE, the relay UE sends a third message to the second-end UE to modify or update the direct link, wherein the third message contains the MAC address of the first-end UE.

[0569] In one embodiment, the relay UE may receive a link establishment request message from the first-end UE to support U2U relay communication. The request message can be used for 5G ProSe inter-UE relay communication with integrated discovery. The request message may contain relay_indication. The request message may not contain information for identifying any inter-UE relay.

[0570] In one embodiment, the third message may contain information for providing PC5 QoS-related information to the target UE. The third message may be sent to the target UE during the link establishment procedure or before sending an accept message corresponding to the request message to the source UE.

[0571] In one embodiment, the first message may be a PROSE DIRECT LINK SECURITY MODE COMMAND message. The second message may be a PROSE DIRECT LINK SECURITY MODE COMPLETE message. The third message may be a link modification request message or a PROSE DIRECT LINK MODIFICATION REQUEST message.

[0572] In one embodiment, the request message can be a Direct Linkestablishment Request message or a Prose Direct Linkestablishment Request message. The acceptance message can be a Direct Linkestablishment Accept message or a Prose Direct Linkestablishment Accept message.

[0573] In one embodiment, the direct link can be a PC5 connection, a PC5-S connection, a PC5-RRC connection, or a Layer 2 link. The first-end UE can be a source 5G ProSe (Layer 3) UE. The second-end UE can be a target 5G ProSe (Layer 3) UE. The relay UE can be a relay UE between 5G ProSe (Layer 3) UEs.

[0574] Return to reference Figure 3 and Figure 4 In an exemplary embodiment from the perspective of the relay UE, the relay UE 300 includes program code 312 stored in memory 310. CPU 308 can execute program code 312 to enable the relay UE to (i) establish a direct link with a second-end UE to support U2U relay communication between the first-end UE and the second-end UE via the relay UE, (ii) send a first message to the first-end UE to trigger a security establishment between the first-end UE and the relay UE, (iii) receive a second message from the first-end UE to establish a security context between the relay UE and the first-end UE, wherein the second message contains the MAC address of the first-end UE, and (iv) in response to receiving the MAC address of the first-end UE, send a third message to the second-end UE to modify or update the direct link, wherein the third message contains the MAC address of the first-end UE. Furthermore, CPU 308 can execute program code 312 to perform all the above actions and steps or other actions and steps described herein.

[0575] Figure 20 This is flowchart 2000 for a relay user equipment (UE). In step 2005, the relay UE establishes a direct link with the second-end UE to support U2U relay communication between the first-end UE and the second-end UE via the relay UE. In step 2010, after establishing the direct link between the relay UE and the second-end UE, the relay UE sends a first message to the first-end UE to trigger the establishment of security between the first-end UE and the relay UE. In step 2015, the relay UE receives a second message from the first-end UE to establish a security context or add new PC5 Quality of Service (QoS) information between the relay UE and the first-end UE, wherein the second message contains first PC5 QoS information for supporting U2U relay communication and the MAC address of the first-end UE. In step 2020, in response to receiving the first PC5 QoS information, the relay UE sends a third message to the second-end UE to modify or update the direct link, wherein the third message contains second PC5 QoS information for supporting U2U relay communication and the MAC address of the first-end UE contained in the second message.

[0576] In one embodiment, a relay UE may receive a link establishment request message from a first-end UE to support U2U relay communication. The request message may contain a relay indication indicating its use for 5G ProSe UE-to-UE relay communication with integrated discovery. The request message may not contain information for identifying any UE-to-UE relay.

[0577] In one embodiment, the first message may be a PROSE DIRECT LINK SECURITY MODE COMMAND message, and the second message may be a PROSE DIRECT LINK SECURITY MODE COMPLETE message. The third message may be a link modification request message or a PROSE DIRECT LINK MODIFICATION REQUEST message. The third message can be sent during the link modification procedure to provide the MAC address of the first UE to the second UE.

[0578] In one embodiment, the request message can be a direct communication request message or a PROSE DIRECT LINKESTABLISHMENT REQUEST message, and the acceptance message is a direct communication acceptance message or a PROSE DIRECT LINKESTABLISHMENT ACCEPT message. The direct link can be a PC5 connection, a PC5-S connection, a PC5-RRC connection, or a Layer 2 link. The first-end UE can be a source 5G ProSe UE. The second-end UE can be a target 5G ProSe UE. The relay UE can be a 5G ProSe UE-to-UE relay UE.

[0579] Return to reference Figure 3 and Figure 4In an exemplary embodiment from the perspective of the relay UE, the relay UE 300 includes program code 312 stored in memory 310. CPU 308 can execute program code 312 to enable the relay UE to (i) establish a direct link with a second-end UE to support U2U relay communication between the first-end UE and the second-end UE via the relay UE, (ii) after establishing a direct link between the relay UE and the second-end UE, send a first message to the first-end UE to trigger a security establishment between the first-end UE and the relay UE, (iii) receive a second message from the first-end UE to establish a security context or add new PC5 QoS information between the relay UE and the first-end UE, wherein the second message includes first PC5 QoS information for supporting U2U relay communication and the MAC address of the first-end UE, and (iv) in response to receiving the first PC5 QoS information, send a third message to the second-end UE to modify or update the direct link, wherein the third message includes second PC5 QoS information for supporting U2U relay communication and the MAC address of the first-end UE included in the second message. In addition, CPU 308 can execute program code 312 to perform all the above actions and steps or other actions and steps described herein.

[0580] Various aspects of this disclosure have been described above. It should be understood that the teachings herein can be embodied in a wide variety of forms, and any specific structure, function, or both disclosed herein are merely representative. Based on the teachings herein, those skilled in the art will understand that the aspects disclosed herein can be implemented independently of any other aspects, and two or more of these aspects can be combined in various ways. For example, any number of aspects set forth herein can be used to implement an apparatus or practice. Furthermore, such apparatuses or practices can be implemented using structures, functions, or structures and functions different from those set forth herein, in addition to one or more aspects. As examples of some of the foregoing concepts, in some aspects a parallel channel can be established based on the pulse repetition frequency. In some aspects a parallel channel can be established based on the pulse position or offset. In some aspects a parallel channel can be established based on a time-hopping sequence. In some aspects a parallel channel can be established based on the pulse repetition frequency, the pulse position or offset, and the time-hopping sequence.

[0581] Those skilled in the art will understand that information and signals can be represented using any of a variety of different techniques and skills. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the above description can be represented by voltage, current, electromagnetic waves, magnetic fields or magnetic particles, light fields or light particles, or any combination thereof.

[0582] Those skilled in the art will further appreciate that the various illustrative logic blocks, modules, processors, components, circuits, and algorithm steps described in conjunction with the aspects disclosed herein can be implemented as electronic hardware (e.g., digital implementations, analog implementations, or a combination of both, which may be designed using source decoding or some other technique) and have instructions in various forms of program or design code (which, for convenience, may be referred to herein as "software" or "software module") or a combination of both. To clearly illustrate this interchangeability between hardware and software, the various illustrative components, blocks, modules, circuits, and steps have been described above in general terms of their functionality. Whether such functionality is implemented as hardware or software depends on the specific application and the design constraints imposed on the system as a whole. Those skilled in the art may implement the described functionality in different ways for each specific application, but such implementation decisions should not be construed as causing a departure from the scope of this disclosure.

[0583] Furthermore, the various illustrative logic blocks, modules, and circuits described in connection with the aspects disclosed herein may be implemented within, or executed by, an integrated circuit (“IC”), an access terminal, or an access point. An IC may include a general-purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, electrical components, optical components, mechanical components, or any combination thereof designed to perform the functions described herein, and may execute code or instructions residing within, outside, or both of the IC. A general-purpose processor may be a microprocessor, but alternatively, the processor may be any conventional processor, controller, microcontroller, or state machine. The processor may also be implemented as a combination of computing devices, such as a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors incorporating a DSP core, or any other such configuration.

[0584] It should be understood that any particular order or hierarchy of steps in any disclosed process is an instance of the example method. It should be understood that a particular order or hierarchy of steps in the process may be rearranged based on design preferences while remaining within the scope of this disclosure. The appended method claims present the elements of the various steps in an exemplary order and are not intended to limit us to the particular order or hierarchy presented.

[0585] The steps of the methods or algorithms described in conjunction with the aspects disclosed herein can be implemented directly in hardware, in a software module executed by a processor, or a combination of both. The software module (e.g., containing executable instructions and associated data) and other data can reside in data memory, such as RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, removable disk, CD-ROM, or any other form of computer-readable storage media known in the art. Example storage media can be coupled to a machine such as a computer / processor (which may be referred to herein as a "processor"), which can read information (e.g., code) from and write information to the storage media. Example storage media can be integrated with a processor. The processor and storage media can reside in an ASIC. The ASIC can reside in a user device. Alternatively, the processor and storage media can reside as discrete components in a user device. Furthermore, in some aspects, any suitable computer program product may include computer-readable media comprising code relating to one or more aspects of this disclosure. In some aspects, the computer program product may include packaging material.

[0586] While the invention has been described in conjunction with various aspects, it should be understood that further modifications are possible. This application is intended to cover any changes, uses, or adaptations to the invention that generally follow the principles of the invention and include such deviations from this disclosure, which fall within the scope of known and common practice in the field to which this invention pertains.

Claims

1. A method for relay communication between user equipments, used for relaying user equipment, characterized in that, include: The relay user equipment establishes a direct link with the second end user equipment to support inter-user equipment relay communication between the first end user equipment and the second end user equipment via the relay user equipment. After the direct link is established between the relay user equipment and the second end user equipment, the relay user equipment sends a first message to the first end user equipment to trigger the establishment of a security connection between the first end user equipment and the relay user equipment. The relay user equipment receives a second message from the first end user equipment to establish a security context or add new PC5 quality of service information between the relay user equipment and the first end user equipment, wherein the second message includes first PC5 quality of service information for supporting relay communication between the user equipments and the media access control address of the first end user equipment. as well as In response to receiving the first PC5 Quality of Service information, the relay user equipment sends a third message to the second end user equipment for modifying or updating the direct link, wherein the third message includes second PC5 Quality of Service information for supporting relay communication between the user equipments and the media access control address of the first end user equipment contained in the second message.

2. The method according to claim 1, characterized in that, Further includes: The relay user equipment receives a link establishment procedure request message from the first end user equipment to support relay communication between the user equipments.

3. The method according to claim 2, characterized in that, The request message contains a relay indication that it is used for 5G proximity-based inter-service user equipment relay communication with integrated discovery.

4. The method according to claim 2, characterized in that, The request message does not contain information for identifying any inter-user equipment relay.

5. The method according to claim 1, characterized in that, The first message is a PROSE DIRECT LINK SECURITY MODE COMMAND message, and the second message is a PROSE DIRECT LINK SECURITY MODE COMPLETE message.

6. The method according to claim 1, characterized in that, The third message is either a link modification request message or a PROSE DIRECT LINK MODIFICATION REQUEST message.

7. The method according to claim 1, characterized in that, The third message is sent in the link modification procedure to provide the media access control address of the first end user equipment to the second end user equipment.

8. The method according to claim 2, characterized in that, The request message is either a Direct Communication Request message or a PROSE DIRECT LINK ESTABLISHMENT REQUEST message, and the acceptance message is either a Direct Communication Accept message or a PROSE DIRECT LINK ESTABLISHMENT ACCEPT message.

9. The method according to claim 1, characterized in that, The direct link is a PC5 connection, a PC5-S connection, a PC5-RRC connection, or a Layer 2 link.

10. The method according to claim 1, characterized in that, The first end user equipment is a source 5G proximity-based serving end user equipment, the second end user equipment is a target 5G proximity-based serving end user equipment, and the relay user equipment is a 5G proximity-based serving end user equipment inter-relay user equipment.

11. A relay user equipment, characterized in that, include: Control circuit; A processor, which is installed in the control circuit; A memory, which is installed in the control circuit and coupled to the processor; The processor is configured to execute program code stored in the memory to: A direct link is established with the second end user equipment to support inter-user equipment relay communication between the first end user equipment and the second end user equipment via the relay user equipment; After the direct link is established between the relay user equipment and the second end user equipment, a first message is sent to the first end user equipment to trigger the establishment of a security connection between the first end user equipment and the relay user equipment. A second message is received from the first end user equipment to establish a security context or add new PC5 quality of service information between the relay user equipment and the first end user equipment, wherein the second message includes first PC5 quality of service information for supporting relay communication between the user equipments and the media access control address of the first end user equipment. as well as In response to receiving the first PC5 Quality of Service information, a third message is sent to the second end user equipment to modify or update the direct link, wherein the third message contains second PC5 Quality of Service information for supporting relay communication between the user equipments and the Media Access Control address of the first end user equipment contained in the second message.

12. The relay user equipment according to claim 11, characterized in that, The processor is configured to execute program code stored in the memory to: The first end user equipment receives a link establishment procedure request message to support relay communication between the user equipments.

13. The relay user equipment according to claim 12, characterized in that, The request message contains a relay indication that it is used for 5G proximity-based inter-service user equipment relay communication with integrated discovery.

14. The relay user equipment according to claim 12, characterized in that, The request message does not contain information for identifying any inter-user equipment relay.

15. The relay user equipment according to claim 11, characterized in that, The first message is the PROSE DIRECTLINK SECURITY MODE COMMAND message, and the second message is the PROSE DIRECT LINK SECURITY MODE COMPLETE message.

16. The relay user equipment according to claim 11, characterized in that, The third message is either a link modification request message or a PROSE DIRECT LINK MODIFICATION REQUEST message.

17. The relay user equipment according to claim 11, characterized in that, The third message is sent in the link modification procedure to provide the media access control address of the first end user equipment to the second end user equipment.

18. The relay user equipment according to claim 12, characterized in that, The request message is either a Direct Communication Request message or a PROSE DIRECT LINK ESTABLISHMENT REQUEST message, and the acceptance message is either a Direct Communication Accept message or a PROSE DIRECT LINK ESTABLISHMENT ACCEPT message.

19. The relay user equipment according to claim 11, characterized in that, The direct link is a PC5 connection, a PC5-S connection, a PC5-RRC connection, or a Layer 2 link.

20. The relay user equipment according to claim 11, characterized in that, The first end user equipment is a source 5G proximity-based serving end user equipment, the second end user equipment is a target 5G proximity-based serving end user equipment, and the relay user equipment is a 5G proximity-based serving end user equipment inter-relay user equipment.

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