UE-to-UE relay communications for non-IP traffic

Abstract

A relay UE includes a receiver for receiving a control plane (CP) message transmitted by a terminal UE to the relay UE. The CP message includes a data link layer (DLL) address (e.g., Ethernet MAC address) of the terminal UE. The relay UE further comprises processing circuitry configured to cause the relay UE to maintain an association between the DLL address of the terminal UE and the link established with the terminal UE.

Description

Technical Field

[0001] Embodiments are disclosed relating to UE relay for relaying traffic (e.g., Ethernet protocol data units (PDUs) or unstructured traffic) from a source user equipment (UE) to a target UE or from a source UE (also referred to as a remote UE) to a network node (e.g., an application server). Background Art

[0002] The Third Generation Partnership Project (3GPP) Technical Report (TR) 23.700-33 V1.2.0 ("TR 23.700-33") provides an assessment of possible architectural enhancements for the fifth generation (5G) Proximity-based Services (5G ProSe) system defined in 3GPP Technical Specification (TS) 23.304 V18.0.0 ("TS 23.304"). TR 23.700-33 describes UE-to-UE (also known as U2U) relay, which is a UE that relays traffic from a source UE to a target UE. A UE is any communication device capable of wireless communication. A UE-to-Network (U2N) relay is a UE that relays traffic from a UE (also known as a "remote UE") to a network node (e.g., an application server).

[0003] When a source UE wants to communicate with a target UE, it will first try to find the target UE by sending a Direct Communication Request (DCR) or a request message with the target UE information. If the source UE cannot reach the target UE directly, it will try to discover a UE-to-UE relay for reaching the target UE, which may also trigger the relay to discover the target UE.

[0004] For IP traffic relayed from a source UE to a target UE, the U2U relay acts as an IP router, the link between the source UE and the U2U relay can be shared by multiple target UEs, and the link between the U2U relay and the target UE can be shared by multiple source UEs. Summary of the Invention

[0005] There are certain challenges.

[0006] While it is agreed that 5G ProSe Layer 3 UE-to-UE relays should provide generic functionality capable of relaying any IP, Ethernet, or unstructured traffic, TS 23.304 does not document how Layer 3 U2U relays support Ethernet or unstructured traffic. Another challenge is that when relaying Data Link Layer (also known as Layer 2) traffic (e.g., Ethernet traffic), a UE relay (U2U relay or U2N relay) can act as a Layer 2 switch (e.g., an Ethernet switch). However, if a UE relay (or simply "relay") acts as a switch, the relay must maintain (e.g., create) an association between a Data Link Layer (DLL) address (e.g., a Media Access Control (MAC) address) and the UE's User Information ID, or maintain a link between the relay and the source / destination UE (e.g., establish a mapping table that maps DLL addresses to PC5 links). However, there is currently no solution for how a relay can obtain the MAC address from a source UE (or target UE, if the relay is a U2U relay) before sending Ethernet packets to the terminating UE (source or target UE). Thus, for example, when a relay UE receives an Ethernet packet addressed to a target UE from a source UE, where the target UE itself has not yet sent an Ethernet packet to the relay UE, the relay UE either discards the packet or sends the packet via all links except the link over which the relay received the Ethernet packet.

[0007] Therefore, in one aspect, a relay UE is provided, configured to receive a control plane (CP) message sent by a terminal UE. The CP message includes a data link layer (DLL) address of the terminal UE. The relay UE is further configured to maintain an association between the DLL address of the terminal UE and a link established with the terminal UE.

[0008] In another aspect, a terminal UE (source UE or target UE) is provided. The terminal UE is configured to create a CP message, wherein the CP message includes a DLL address of the terminal UE. The terminal UE is also configured to wirelessly send the CP message to a UE relay.

[0009] In another aspect, a relay UE is provided, configured to receive a first CP message including a DLL address of the first UE from a first UE, and further configured to send a second CP message including the DLL address of the first UE to a second UE, wherein the second CP message is not the first CP message.

[0010] In another aspect, a method performed by a relay UE is provided. The method includes receiving a control plane (CP) message sent by a terminal UE to the relay UE. The CP message includes a DLL address of the terminal UE. The method also includes maintaining an association between the DLL address of the terminal UE and a link established with the terminal UE.

[0011] In another aspect, a method performed by a terminal UE (source UE or target UE) is provided. The method includes: creating a CP message, wherein the CP message includes a DLL address of the terminal UE. The method also includes: wirelessly transmitting the CP message to a UE relay.

[0012] In another aspect, a method performed by a relay UE is provided. The method includes receiving a first CP message including a DLL address of the first UE from a first UE. The method also includes sending a second CP message including the DLL address of the first UE to a second UE, wherein the second CP message is different from the first CP message.

[0013] In another aspect, a computer program comprising instructions is provided, which, when executed by a processing circuit of a UE, causes the UE to perform any of the methods disclosed herein. In one embodiment, a carrier embodying the computer program is provided, wherein the carrier is one of an electronic signal, an optical signal, a radio signal, and a computer-readable storage medium.

[0014] In another aspect, a UE configured to perform the method disclosed herein is provided. The UE may include a memory and a processing circuit coupled to the memory.

[0015] An advantage of the embodiments disclosed herein is that they enable relay UEs to support non-IP services (eg, Ethernet services). BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The accompanying drawings, which are incorporated herein and form a part of the specification, illustrate various embodiments.

[0017] Figure 1A A system according to an embodiment is shown.

[0018] Figure 1B A protocol stack according to an embodiment is shown.

[0019] Figure 1C A protocol stack according to an embodiment is shown.

[0020] Figure 2A is a message flow diagram according to an embodiment.

[0021] Figure 2B is a message flow diagram according to an embodiment.

[0022] Figure 3 is a message flow diagram according to an embodiment.

[0023] Figure 4 is a flowchart illustrating a process according to an embodiment.

[0024] Figure 5is a flowchart illustrating a process according to an embodiment.

[0025] Figure 6 is a flowchart illustrating a process according to an embodiment.

[0026] Figure 7 is a block diagram of a UE according to an embodiment. DETAILED DESCRIPTION

[0027] Figure 1A A system 100 according to an embodiment is shown. System 100 includes a source UE 101, a UE relay 102 (also referred to as "relay UE 102"), a target UE 103, and a network node (NN) 104 (e.g., an application server). Each of UEs 101, 102, and 103 may be an enhanced 5G ProSe Layer 3 UE. Relay 102 may be configured to relay data link layer (DLL) (e.g., Ethernet) traffic from source UE 101 to target UE 103 and / or NN 104. When relay 102 relays DLL traffic, it acts as a Layer 2 switch (e.g., an Ethernet switch). As shown in FIG1 , network 110 enables communication between relay 102 and NN 104.

[0028] As described above, if relay 102 acts as a switch, the relay needs to create at least a first mapping between a data link layer address (e.g., an Ethernet media access control (MAC) address) assigned to source UE 102 and a user information ID of source UE 102, or a link 112 between the relay and the source UE. If relay 102 relays DLL traffic between source UE 101 and target UE 102, relay 102 also needs to obtain a DLL address of target UE 103 and associate the DLL address of the target UE with a link 114 between relay 102 and target UE 103.

[0029] Figure 1B Example user plane protocol stacks for source UE 101, relay 102, and target UE 103 are shown. Figure 1B In the example shown, non-IP data generated at the UE 101 (e.g., Ethernet PDUs (also known as Ethernet frames)) is processed by the Service Data Adaptation Protocol (SDAP) layer (which is a Layer 2 protocol) and other Layer 2 protocol layers (i.e., the Packet Data Convergence Protocol (PDCP) layer, the Radio Link Control (RLC) layer, and the Medium Access Control (MAC) layer) before being sent over the air by the Physical (PHY) layer.

[0030] Relay 102 receives the over-the-air transmission and obtains the non-IP data sent by source UE 101. In this example, the non-IP data is an Ethernet frame addressed to target UE 103. After obtaining the Ethernet frame, relay 102 discovers the destination address included in the Ethernet frame and uses a mapping table (or similar) to map the destination address to a link (in this case, link 114 between relay 102 and target UE 103). After determining the link associated with the destination address, the Ethernet frame is provided to and processed by the Layer 2 layers (SDAP, PDCP, RLC, MAC) before being sent over-the-air to target UE 103. In other words, relay 102 sends a Layer 2 message (e.g., an SDAP PDU) generated by relay 102 to target UE 103. The Layer 2 message encapsulates the Ethernet frame received from source UE 101. In this way, relay 102 relays the non-IP data from the source UE to the target UE.

[0031] The same process occurs in the reverse direction. That is, relay 102 receives a Layer 2 message (DLL PDU) from target 103 containing an Ethernet frame addressed to source UE 102. Relay 102 discovers the destination address included in the Ethernet frame and uses a mapping table (or similar) to map the destination address to a link (in this case, link 112 between relay 102 and source UE 101). After determining the link associated with the destination address, the Ethernet frame is provided to and processed by the Layer 2 layers (SDAP, PDCP, RLC, MAC), and then sent over the air to source UE 103. That is, relay 102 transmits a Layer 2 message (e.g., SDAP PDU) generated by relay 102 to source UE 101. The Layer 2 message encapsulates the Ethernet frame received from target UE 103. In this way, relay 102 relays non-IP data from the target UE to the source UE.

[0032] In order to map the source UE's DLL address to link 112 and the target UE's DLL address to link 114, relay 102 must discover the source UE's DLL address and the target UE's DLL address. In one embodiment, this is achieved using control plane (CP) signaling between the source UE and the relay, and between the target UE and the relay. Figure 1C An example control plane protocol stack is shown that allows the source / target UE to send and receive CP messages to and from the relay 102. In the example, each UE shown (source, target, relay) includes a CP layer (in this example, the PC5 signaling protocol layer) located above one or more Layer 2 layers (e.g., PDCP, RLC, and MAC).

[0033] Figure 2A and Figure 2BAn embodiment is shown that enables the relay 102 to obtain the DLL (eg, Ethernet MAC) address of the source UE 101 and the DLL address of the target UE 103 so that the relay 102 can create a mapping.

[0034] Provide DLL address during PC5 link establishment

[0035] Figure 2A is a message flow diagram illustrating the link establishment process. In 3GPP 5G terminology, a link is referred to as a "PC5 link" or simply "PC5". Figure 2A The message flow diagram shown assumes that i) each UE has performed service authorization and provisioning, ii) source UE 101 has discovered relay 102, and iii) relay 102 has discovered target UE 103. As part of the link establishment process, source UE 101 and target UE 103 provide their DLL addresses to relay 102, as described below.

[0036] like Figure 2A As shown, source UE 101 sends a CP message m201 (in this case, a Direct Communication Request (DCR) message) to relay 102 to initiate a Layer 2 link establishment procedure with relay 102 (i.e., source UE 101 initiates establishment of a PC5 link with relay 102). The DCR message m201 is sent using a source Layer 2 ID and a destination Layer 2 ID. The source Layer 2 ID is self-assigned by source UE 101, and the destination Layer 2 ID is set to the Layer 2 ID received by source UE 101 from relay 102 (e.g., the destination Layer 2 ID is set to the source Layer 2 ID included in a discovery message sent by relay 102 to source UE 101). The DCR m201 may include a Relay Service Code (RSC) and / or a User Information ID. The RSC may indicate that the link to be established is for DLL services (or the DCR m201 may include another indicator indicating that the link to be established is for DLL services).

[0037] If the user information ID in the DCR message m201 matches the user information ID of the relay and / or the RSC in the DCR message matches an RSC supported by relay 102, relay 102 responds by establishing security protection with source UE 101. That is, relay 102 sends a security command message m202 (e.g., a PROSE DIRECT LINK SECURITY MODE COMMAND message defined in 3GPP TS 24.554 V17.2.1 ("TS 24.554")) to source UE 101. When security protection is enabled, source UE 101 sends IP address configuration and QoS information to relay 102.

[0038] If the requested PC5 link is used to carry DLL traffic (e.g., Ethernet traffic), in one embodiment, source UE 101 sends its DLL address (e.g., Ethernet MAC address) to relay 102 after security protection is enabled. The relay UE then maps the DLL address to the PC5 link between source UE 101 and relay 102. For example, source UE 101 may send its DLL address in a security complete message m203 (e.g., the PROSE DIRECT LINK SECURITY MODE COMPLETE message defined in TS 24.554). If the DLL address is already in use by another UE, the relay will send a message to the source UE indicating a DLL address conflict. In another embodiment, source UE 101 may send its DLL address before security is established to enable early address conflict detection. For example, source UE 101 may include its DLL address in a DCR message m201. In either case, relay 102 maps (ie, associates) the DLL address of source UE 101 with the PC5 link between UE 101 and relay 102 .

[0039] After the security establishment procedure is complete, relay 102 sends a CP message m204 (in this case, a Direct Communication Request (DCR) message) to target UE 103 to initiate the Layer 2 link establishment procedure with target UE 103 (i.e., relay 102 initiates establishment of a PC5 link with target UE 103). The DCR message m204 is sent using a source Layer 2 ID and a destination Layer 2 ID. The source Layer 2 ID is self-assigned by relay 102, and the destination Layer 2 ID is set to the Layer 2 ID received by relay 102 from the target UE (e.g., the destination Layer 2 ID is set to the source Layer 2 ID included in the discovery message sent by target UE 103 to relay 102). The DCR m204 may include a relay service code (RSC) and / or a user information ID. Relay 102 should select different source Layer 2 IDs for PC5 links for different types of services (i.e., IP services, Ethernet services, and unstructured services). The RSC may indicate that the link to be established is for DLL traffic (or the DCR m204 may include another indicator to indicate that the link to be established is for DLL traffic).

[0040] If the user information ID and RSC of the target 5G ProSe Layer 3 terminal UE included in the DCR message m204 match the user information ID and RSC supported by the target UE, the target UE 103 responds by establishing security protection with the relay 102. That is, the target UE 103 sends a security message m205 (e.g., a PROSE DIRECT LINK SECURITY MODE COMMAND message defined in TS 24.554 or a PROSE DIRECT LINK SECURITY ESTABLISHMENT REQUEST message defined in 3GPP Technical Document (Tdoc) C1-238124) to the relay 102. When security protection is enabled, the relay 102 sends IP address configuration and QoS information to the target UE 103.

[0041] If the PC5 link is used to transmit DLL traffic, relay 102 may send the DLL address of source UE 101 to target UE 103. For example, relay 102 may include the DLL address of source UE 101 in a security message m206 (e.g., a PROSE DIRECT LINK SECURITY MODE COMPLETE message defined in TS 24.554 or a PROSE DIRECT LINK SECURITY ESTABLISHMENT ACCEPT message defined in C1-238124) sent by relay 102 to target 103. Alternatively, relay 102 may include the DLL address of UE 101 in a DCR message m204.

[0042] The source layer 2 ID used for the security establishment procedure is self-assigned by the target UE 103, and the destination layer 2 ID is set to the source layer 2 ID of the received direct communication request message m204.

[0043] After receiving the security setup procedure message, relay 102 obtains the layer 2 ID of target UE 103 for future communications, for signaling and data traffic for the unicast link.

[0044] After security protection is established, the target UE 103 sends a Direct Communication Accept (DCA) message m207 to the relay 102. If the PC5 link is used to transmit DLL traffic, then in one embodiment, the target UE 103 sends its DLL address to the relay 102 in the DCA message m207. If the DLL address is already in use by another UE, the relay will send a message to the target UE indicating that there is an address conflict.

[0045] After receiving DCA message m207, relay 102 sends DCA message m208 to source UE 101. The parameters included in DCA message m208 are described in Section 6.4.3 of TS 23.304. If the PC5 link between source UE 101 and relay 102 is used to transmit DLL traffic, relay 102 may send the DLL address of target UE 103 to source UE 101 in DCA message m208.

[0046] For IP communication, the relay 102 may store the association of the target UE 103's user information ID and IP address into its DNS entry, and the relay 102 may act as a DNS server for other UEs.

[0047] After source UE 101 receives DCA message m208, source UE 101 may communicate with target UE 103 via relay 102. That is, relay 102 may relay DLL traffic from source UE 101 to target UE 103. For example, when relay 102 receives a DLL frame sent by source UE 101, relay 102 routes the frame based on the destination DLL address included in the frame. Therefore, if the destination DLL address included in the DLL frame matches the DLL address of target UE 103, relay 102 forwards the frame to target UE 103 via the PC5 link previously established between relay 102 and target UE 103. That is, for example, relay 102 may maintain a table that maps DLL destination addresses to PC5 links, so that DLL frames can be routed to the correct destination.

[0048] Provide DLL address during PC5 link modification

[0049] Figure 2B is a message flow diagram illustrating the link modification process. Figure 2B The message flow diagram shown assumes that a PC5 link for DLL traffic already exists between the source UE 101 and the relay 102 and / or between the relay 102 and the target UE 103. The existing links will be used to transfer DLL traffic between the source UE and the target UE via the relay.

[0050] like Figure 2BAs shown, source UE 101 sends a Link Modification Request (LMR) message m252 to relay 102. LMR message m252 contains the user information ID and layer 2 ID of target UE 103, as well as the end-to-end QoS to the target UE. Relay 102 already knows the DLL address of the source UE because the link has already been established.

[0051] If an existing PC5 link exists between relay 102 and the target UE for the required RSC associated with the Ethernet service, the relay sends an LMR message m254 to the target UE. LMR message m254 includes the source UE's user information ID, the source UE's IP address (if available in the relay), and the QoS between the relay and the target UE. The relay includes the source UE's DLL address in the LMR message m254 sent to the target UE.

[0052] The target UE 103 then sends an LMA message m256 to the relay. The relay already knows the DLL of the target UE because the link has already been established.

[0053] After receiving the LMA message m256, the relay sends an LMA message m258 to the source UE. In one embodiment, the relay includes the DLL address of the target UE in the LMA message 258 sent to the source UE.

[0054] The above example illustrates the case where relay 102 is a U2U relay. However, as previously described, relay 102 can also be a U2N relay. When source UE 101 establishes a PC5 link for Ethernet traffic with relay 102, which is acting as a U2N relay, the source UE sends its DLL address (e.g., Ethernet MAC address) to relay 102, as described above. For example, the source UE sends its Ethernet MAC address in a PROSE DIRECTLINK SECURITY MODE COMPLETE message.

[0055] Additional Examples

[0056] 3GPP has agreed that a 5G ProSe Layer 3 UE-to-UE relay (e.g., relay 102) should provide generic functionality capable of relaying any IP, Ethernet, or unstructured traffic. However, TS 23.304 does not document how Layer 3 U2U relays support Ethernet or unstructured traffic. In other words, according to 3GPP, how to support Ethernet and unstructured traffic is for further study (FFS). This disclosure describes how to support Ethernet and unstructured traffic by enabling a Layer 3 U2U relay to forward non-IP traffic while maintaining a 1:1 mapping between the link with the source UE and the link with the target UE.

[0057] Figure 3 is a message flow diagram according to an embodiment. Figure 3 The message flow shown in illustrates the process for 5G ProSe communication via 5G ProSe layer 3 UE-to-UE relay. Figure 3 The twelve steps shown in .

[0058] 1. Perform service authorization and provisioning for the source 5G ProSe layer 3 terminal UE, the target 5G ProSe layer 3 terminal UE, and the 5G ProSe layer 3 UE-to-UE relay as described in clause 6.2 of TS 23.304.

[0059] 2. The source 5G ProSe Layer 3 terminal UE performs discovery of 5G ProSe Layer 3 UE-to-UE relay as described in clause 6.3.2.4 of TS 23.304.

[0060] 3. The source 5G ProSe Layer 3 terminal UE sends a Direct Communication Request message to initiate a unicast Layer 2 link establishment procedure with the 5G ProSe Layer 3 UE-to-UE relay. The parameters included in the Direct Communication Request message are described in clause 6.4.3 of TS 23.304. The Source Layer 2 ID of the DCR message is self-assigned by the source 5G ProSe Layer 3 terminal UE, and the Destination Layer 2 ID is set to the Source Layer 2 ID of the Discovery message sent by the 5G ProSe Layer 3 UE-to-UE relay.

[0061] 4. If the User Information ID of the 5G ProSe Layer 3 UE-to-UE Relay in the DCR message matches the User Information ID of the relay and / or the RSC in the Direct Communication Request matches one of the RSCs supported by the relay, 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 IP address configuration, QoS information (as described in clause 6.4.3) to the 5G ProSe Layer 3 UE-to-UE Relay.

[0062] If the PC5 link is used to transmit Ethernet traffic, the source 5G ProSe layer 3 terminal UE sends its Ethernet MAC address to the 5G ProSe layer 3 UE-to-UE relay after security protection is enabled. If the Ethernet MAC address is already used by another 5G ProSe layer 3 terminal UE, the 5G ProSe layer 3 UE-to-UE relay may send a message to the source 5G ProSe layer 3 terminal UE indicating that there is an Ethernet MAC address conflict.

[0063] The source Layer 2 ID used for the security establishment procedure is self-assigned by the 5G ProSe Layer 3 UE-to-UE relay, and the destination Layer 2 ID is set to the source Layer 2 ID of the received direct communication request message.

[0064] 5G ProSe layer 3 UE-to-UE relay should select different source layer 2 IDs for PC5 links for different types of services (i.e., IP services, Ethernet services, and unstructured services).

[0065] If the PC5 link is used to transmit unstructured traffic, the 5G ProSe Layer 3 UE-to-UE relay should select different source Layer 2 IDs for different source and target 5G ProSe Layer 3 terminal UE pairs.

[0066] After receiving the security establishment procedure message, the source 5G ProSe layer 3 terminal UE obtains the layer 2 ID of the 5G ProSe layer 3 UE-to-UE relay for future communications, for signaling and data services for the unicast link.

[0067] 5. After the security establishment procedure in step 4 is completed, the 5G ProSe Layer 3 UE-to-UE relay sends a Direct Communication Request message to initiate a unicast Layer 2 link establishment procedure with the target 5G ProSe Layer 3 terminal UE. The parameters included in the Direct Communication Request message are described in clause 6.4.3 of TS 23.304.

[0068] The source layer 2 ID of the DCR message is self-assigned by the 5G ProSe layer 3 UE-to-UE relay, and the destination layer 2 ID is the unicast layer 2 ID of the target 5G ProSe layer 3 terminal UE associated with the user information ID of the target 5G ProSe layer 3 terminal UE.

[0069] 5G ProSe layer 3 UE-to-UE relay should select different source layer 2 IDs for PC5 links for different types of services (i.e., IP services, Ethernet services, and unstructured services).

[0070] If the PC5 link is used to transmit unstructured traffic, the 5G ProSe Layer 3 UE-to-UE relay should select different source Layer 2 IDs for different source and target 5G ProSe Layer 3 terminal UE pairs.

[0071] The 5G ProSe layer 3 UE-to-UE relay may select the same source layer 2 ID as in step 4.

[0072] 6. If the user information ID and RSC of the target 5G ProSe Layer 3 terminal UE included in the direct communication request match the user information ID of the target UE and the RSC supported by the target UE, the target 5G ProSe Layer 3 terminal UE responds by establishing security with the 5G ProSe Layer 3 UE-to-UE relay. When security protection is enabled, the 5G ProSe Layer 3 UE-to-UE relay sends IP address configuration and QoS information to the target 5G ProSe Layer 3 terminal UE (as described in clause 6.4.3 of TS 23.304).

[0073] If the PC5 link is used to transmit Ethernet traffic, after security protection is enabled, the 5G ProSe layer 3 UE-to-UE relay sends the Ethernet MAC address of the source 5G ProSe layer 3 terminal UE to the target 5G ProSe layer 3 terminal UE.

[0074] The source layer 2 ID used for the security establishment procedure is self-assigned by the target 5G ProSe layer 3 terminal UE, and the destination layer 2 ID is set to the source layer 2 ID of the received direct communication request message.

[0075] After receiving the security establishment procedure message, the 5G ProSe layer 3 UE-to-UE relay obtains the layer 2 ID of the target 5G ProSe layer 3 terminal UE for future communications, for signaling and data services for the unicast link.

[0076] 7. The target 5G ProSe layer 3 terminal UE sends a direct communication accept message to the 5G ProSe layer 3 UE-to-UE relay with which it has successfully established security. The parameters included in the direct communication accept message are described in Section 6.4.3 of TS 23.304.

[0077] 8. For IP traffic, allocate an IPv6 prefix or IPv4 address to the target 5G ProSe Layer 3 terminal UE, as defined in clause 5.5.1.4 of TS 23.304.

[0078] 9. After receiving the Direct Communication Accept message from the target 5G ProSe Layer 3 terminal UE, the 5G ProSe Layer 3 UE-to-UE relay sends a Direct Communication Accept message to the source 5G ProSe Layer 3 terminal UE with which security has been successfully established. The parameters included in the Direct Communication Accept message are described in Section 6.4.3 of TS 23.304.

[0079] 10. For IP traffic, the source 5G ProSe Layer 3 terminal UE is allocated an IPv6 prefix or an IPv4 address as defined in clause 5.5.1.4 of TS 23.304.

[0080] 11. For IP communication, the 5G ProSe layer 3 UE-to-UE relay may store the association between the user information ID and IP address of the target 5G ProSe layer 3 terminal UE in its DNS entry, and the 5G ProSe layer 3 UE-to-UE relay may act as a DNS server for other UEs. If the IP address of the target 5G ProSe layer 3 terminal UE is not received in step 9, the source 5G ProSe layer 3 terminal UE may send a DNS query to the 5G ProSe layer 3 UE-to-UE relay after step 10 to request the IP address of the target 5G ProSe layer 3 terminal UE, and the 5G ProSe layer 3 UE-to-UE relay returns the IP address of the target 5G ProSe layer 3 terminal UE to the source 5G ProSe layer 3 terminal UE.

[0081] 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 terminal UE.

[0082] For unstructured traffic communications, for each source and target 5G ProSe layer 3 terminal UE pair, the 5G ProSe layer 3 UE-to-UE relay maintains a 1:1 mapping between the PC5 link with the source 5G ProSe layer 3 terminal UE and the PC5 link with the target 5G ProSe layer 3 terminal UE.

[0083] 12. The source 5G ProSe layer 3 terminal UE communicates with the target 5G ProSe layer 3 terminal UE via the 5G ProSe layer 3 UE-to-UE relay.

[0084] In the case where a source 5G ProSe Layer 3 terminal UE communicates with multiple target 5G ProSe Layer 3 terminal UEs, the PC5 link between the source 5G ProSe Layer 3 terminal UE and the 5G ProSe Layer 3 UE-to-UE relay can be shared for the multiple target 5G ProSe Layer 3 terminal UEs according to RSC, and at the same time, separate PC5 links can be established between the 5G ProSe Layer 3 UE-to-UE relay and the target 5G ProSe Layer 2 terminal UEs according to RSC. For the shared PC5 link, the Layer 2 link modification procedure should be used.

[0085] In the case where multiple source 5G ProSe Layer 3 terminal UEs communicate with one target 5G ProSe Layer 3 terminal UE, the PC5 link between the 5G ProSe Layer 3 UE-to-UE relay and the target 5G ProSe Layer 3 terminal UE can be shared per RSC, while a separate PC5 link can be established between the source 5G ProSe Layer 3 terminal UE and the 5G ProSe Layer 3 UE-to-UE relay per RSC. For the shared PC5 link, the Layer 2 link modification procedure should be used.

[0086] Layer 2 link management over the PC5 reference point for 5G ProSe Layer 3 UE-to-UE relay

[0087] For 5G ProSe communication via 5G ProSe Layer 3 UE-to-UE Relay as described in clause 6.7.1 of TS 23.304:

[0088] In step 5, the direct communication request message includes the user information ID of the source 5G ProSe layer 3 terminal UE, the user information ID of the 5G ProSe layer 3 UE to UE relay, the user information ID of the target 5G ProSe layer 3 terminal UE, RSC and security information to the target 5G ProSe layer 3 terminal UE.

[0089] In step 7, the direct communication acceptance message includes the user information ID of the source 5G ProSe layer 3 terminal UE, the user information ID of the 5G ProSe layer 3 UE to UE relay, the user information ID of the target 5G ProSe layer 3 terminal UE, RSC, QoS information, and IP address configuration.

[0090] If the PC5 link is used to transmit Ethernet traffic, the target 5G ProSe layer 3 terminal UE will send its Ethernet MAC address to the 5G ProSe layer 3 UE-to-UE relay in the direct communication accept message.

[0091] In step 9, the direct communication acceptance message includes the user information ID of the source 5G ProSe layer 3 terminal UE, the user information ID of the 5G ProSe layer 3 UE to UE relay, the user information ID of the target 5G ProSe layer 3 terminal UE, RSC, QoS information, IP address configuration and the IP address or Ethernet MAC address of the target 5G ProSe layer 3 terminal UE (if received before step 9).

[0092] Figure 4is a flow chart illustrating a process 400 performed by relay 102 according to an embodiment. Process 400 may begin at step s402. Step s402 includes receiving a CP message sent by a UE (UE 101 or UE 103) to relay 102, wherein the CP message includes a DLL address of the UE. Step s404 includes maintaining (s404) (e.g., establishing) an association between the DLL address and a link established with the UE. In some embodiments, receiving the CP message includes receiving a DLL PDU (e.g., a PDCP PDU, an RLC PDU, or a MAC PDU) having a header and a payload, wherein the payload includes the CP message (or at least a portion thereof).

[0093] In some embodiments, the process further comprises: enabling security protection with the terminal UE, and the CP message is sent by the terminal UE after the security protection with the terminal UE is enabled.

[0094] In some embodiments, the terminal UE is the source UE, the process further includes: sending a message including the DLL address of the source UE to the target UE, the process further includes: enabling security protection with the target UE, the message including the DLL address of the source UE is sent to the target UE after the security protection with the target UE is enabled, the process further includes: obtaining the DLL address of the target UE from the message (m207) sent by the target UE, and sending a message including the DLL address of the target UE to the source UE (m208, m258).

[0095] In some embodiments, the terminal UE is a target UE, the CP message is an accept message, and the process further includes: sending a message including a DLL address of the target UE to the source UE (m208, m258).

[0096] In some embodiments, the DLL address of the terminal UE is a Media Access Control MAC address.

[0097] In some embodiments, the relay UE is a UE-to-UE relay and the terminal UE is a 5G ProSe terminal UE.

[0098] In some embodiments, the relay UE is a UE-to-network relay and the terminal UE is a 5G ProSe remote UE.

[0099] In some embodiments, receiving the CP message includes receiving a DLL protocol data unit (PDU) having a header and a payload, wherein the payload contains at least a portion of the CP message including a DLL address of the terminal UE.

[0100] In some embodiments, the DLL address is an Ethernet MAC address, the process further includes: determining whether the Ethernet MAC address is used by another UE, and the process further includes: in response to determining that the Ethernet MAC address is used by another UE, sending a message to the terminal UE indicating that there is an Ethernet MAC address conflict.

[0101] In some embodiments, the terminal UE is the source UE, the link established with the terminal UE is a PC5 link, and the relay UE is further configured such that if the PC5 link is used to transmit Ethernet services, then after security with the target UE is enabled, the relay UE sends the Ethernet MAC address of the source UE to the target UE.

[0102] Figure 5 is a flow chart illustrating a process 500 performed by UE 101 or UE 103 according to an embodiment. Process 500 may begin at step s502. Step s502 includes the UE creating a CP message (e.g., a sidelink control plane message). The CP message includes the UE's data link layer (DL) address. Step s504 includes wirelessly transmitting the CP message to relay 102. In some embodiments, transmitting the CP message to relay 102 includes creating a DLL PDU (e.g., a MAC frame, an RLC frame, a PDCP PDU) including a payload that includes the CP message (or at least a portion thereof), wherein the DLL PDU is addressed to the relay; and transmitting the DLL PDU to relay 102.

[0103] In some embodiments, the terminal UE is a source UE, and the method includes: the source UE initiating a link establishment process with the relay UE before wirelessly sending a CP message to the relay UE, and the source UE is also configured so that if the link to be established is to be used to transmit Ethernet services, then after security protection with the relay UE is enabled, the source UE sends a CP message including an Ethernet MAC address.

[0104] In some embodiments, the terminal UE is a source UE and the CP message is a security mode complete message in response to a security command message (m202) sent by the relay UE, or the terminal UE is a target UE and the CP message is an accept message (m207) in response to a communication request message (m204) sent by the relay UE.

[0105] In some embodiments, the process further includes: after sending the CP message, receiving a message (m208, m258) from the relay including the DLL address of the target UE, the DLL address of the target UE being the Ethernet MAC address of the target UE, and the process further includes: after receiving the message including the Ethernet MAC address of the target UE, creating a DLL protocol data unit PDU including a payload, the payload including at least a portion of the Ethernet frame; and sending the DLL PDU to the relay UE, wherein the destination address of the DLL PDU is the DLL address of the relay UE and the destination address of the Ethernet frame is the Ethernet MAC address of the target UE.

[0106] In some embodiments, sending a CP message to a relay UE comprises: creating a DLL protocol data unit (PDU) including a payload, the payload including at least a portion of the CP message, the CP message including a DLL address of the terminal UE, wherein the DLL PDU is addressed to the relay UE; and sending the DLL PDU to the relay UE.

[0107] In some embodiments, the process further comprises: before sending the CP message including the DLL address of the terminal UE to the relay: sending a direct communication request DCR to the relay; and performing a security procedure for establishing security with the relay UE.

[0108] Figure 6 is a flow chart illustrating a process 600 performed by relay 102 according to an embodiment. Process 600 may begin at step s602. Step s602 includes receiving a first CP message (e.g., message m203 or m207) from a first UE (e.g., UE 101 or UE 103) that includes the first UE's DLL address. Step s604 includes sending a second CP message (e.g., message m206, m208, m254, m258) to a second UE that includes the first UE's DLL address.

[0109] In some embodiments, the process further includes maintaining an association between the DLL address of the first UE and a link established between the first UE and the relay UE, the link established with the terminal UE being a PC5 link for transmitting Ethernet traffic.

[0110] In some embodiments, the process further includes: enabling security protection with the second UE, the relay UE being configured to send a second CP message including the DLL address of the first UE to the second UE after security protection with the target UE is enabled, and the process further includes: obtaining the DLL address of the second UE from a message (m207) sent by the second UE to the relay UE, and the process further includes: sending a message including the DLL address of the second UE to the first UE (m208, m258).

[0111] In some embodiments, the DLL address of the first UE is an Ethernet MAC address, the process further includes: determining whether the Ethernet MAC address is used by another UE, and the process further includes: in response to determining that the Ethernet MAC address is used by another UE, sending a message to the first UE indicating that there is an Ethernet MAC address conflict.

[0112] In some embodiments, the first UE is a source UE, the second UE is a target UE, the link established with the source UE is a PC5 link, and the relay UE is further configured such that if the PC5 link is used to transmit Ethernet services, then after security with the target UE is enabled, the relay UE sends the DLL address of the source UE to the target UE.

[0113] Figure 7 is a block diagram of UEs 101, 102, and 103 according to some embodiments. Figure 7 As shown, each UE may include: processing circuitry (PC) 702, which includes one or more processors (P) 755 (e.g., one or more general-purpose microprocessors and / or one or more other processors, such as application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), etc.); communication circuitry 748, which is coupled to an antenna arrangement 749 including one or more antennas and includes a transmitter (Tx) 745 and a receiver (Rx) 747 for enabling the UE to transmit and receive data (e.g., wirelessly); and a storage unit (also referred to as a "data storage system") 708, which may include one or more non-volatile memory devices and / or one or more volatile memory devices. In embodiments where PC 702 includes a programmable processor, a computer-readable storage medium (CRSM) 742 may be provided. CRSM 742 may store a computer program (CP) 743 including computer-readable instructions (CRI) 744. CRSM 742 may be a non-transitory computer-readable medium, such as magnetic media (e.g., a hard disk), optical media, a memory device (e.g., random access memory, flash memory), etc. In some embodiments, CRI 744 of computer program 743 is configured such that, when executed by PC 702, the CRI causes the UE to perform the steps described herein (e.g., the steps described herein with reference to the flowcharts). In other embodiments, the UE may be configured to perform the steps described herein without requiring code. That is, for example, PC 702 may consist solely of one or more ASICs. Thus, features of the embodiments described herein may be implemented in hardware and / or software.

[0114] Overview of Various Additional Embodiments

[0115] A1. A user equipment (UE) relay, the UE relay comprising: a receiver for receiving a control plane (CP) message including a DLL address of the UE from a UE; and a processing circuit configured to cause the UE relay to maintain (eg, create) an association between the DLL address and a link established with the UE.

[0116] A2. The UE relay of embodiment A1, wherein the UE is a source UE and the CP message is a security mode complete message (eg, an extended version of the current 3GPP PROSE DIRECT LINK SECURITY MODE COMPLETE message).

[0117] A3. The UE relay of embodiment A1 or A2, wherein the UE is a source UE, and the UE relay further comprises a transmitter for sending a message including a DLL address of the source UE to a target UE.

[0118] A4. The UE relay according to embodiment A3, wherein the message sent to the target UE is a security message or a link modification request message.

[0119] A5. The UE relay according to embodiment A3 or A4, wherein the UE relay is further configured to: obtain the DLL address of the target UE from the message sent by the target UE to the relay UE; and send a message including the DLL address of the target UE to the source UE.

[0120] A6. The UE relay of embodiment A1, wherein the UE is a target UE and the CP message is a communication accept message (eg, an extended version of the current 3GPP direct communication accept message).

[0121] A7. The UE relay according to embodiment A6, wherein the relay UE is further configured to send a message including the DLL address of the target UE to the source UE.

[0122] A8. The method of any one of embodiments A1 to A7, wherein the DLL address of the UE is an Ethernet MAC address.

[0123] A9. The method according to any one of embodiments A1 to A8, wherein the UE relay is a UE-to-UE relay, and the UE is a 5G ProSe terminal UE.

[0124] A10. The method of any one of embodiments A1 to A8, wherein the UE relay is a UE-to-network relay, and the UE is a 5G ProSe remote UE.

[0125] A11. The method of any one of embodiments A1 to A10, wherein receiving the CP message comprises receiving a DLL PDU (eg, a PDCP PDU or an RLC PDU) having a header and a payload, wherein the payload contains at least a portion of the CP message.

[0126] B1. A user equipment (UE), comprising: a receiver; and a transmitter, wherein the UE is configured to transmit a control plane (CP) message including a data link layer (DLL) address of the UE to a relay using the transmitter.

[0127] B2. The UE according to embodiment B1, wherein the UE is a source UE and the CP message is a security mode completion message in response to a security command message sent by a UE relay, or the UE is a target UE and the CP message is a communication acceptance message in response to a communication request message sent by the UE relay.

[0128] B3. The UE of embodiment B1 or B2, wherein the DLL address of the source UE is an Ethernet MAC address.

[0129] B4. The UE of embodiment B1, B2, or B3, wherein the UE sends the CP message to the relay by sending a layer 2 PDU having a header and a payload to the relay, the payload containing at least a portion of the CP message.

[0130] C1. A method performed by a user equipment (UE) relay, the method comprising: receiving a control plane (CP) message including a DLL address of the UE from the UE; and maintaining (eg, creating) an association between the DLL address and a link established with the UE.

[0131] C2. The method of embodiment C1, wherein the CP message is a security mode complete message.

[0132] C3. The method of embodiment C1 or C2, wherein the UE is a source UE, and the method further comprises: the UE relay sending a message including the DLL address of the source UE to a target UE.

[0133] C4. The method of embodiment C3, wherein the message sent to the target UE is a security mode complete message or a link modification request message.

[0134] C5. The method of embodiment C3 or C4, further comprising: obtaining a DLL address of the target UE from a message sent by the target UE to the relay UE; and sending a message including the DLL address of the target UE to the source UE.

[0135] C6. The method of embodiment C1, wherein the UE is a target UE, the method further comprising: sending a communication request message to the target UE, and the CP message is a communication accept message in response to the communication request message sent by the UE relay to the target UE.

[0136] C7. The method of embodiment C6, further comprising: sending a message including the DLL address of the target UE to the source UE.

[0137] C8. The method of any one of embodiments C1 to C7, wherein the DLL address of the UE is an Ethernet MAC address.

[0138] C9. The method of any one of embodiments C1 to C8, wherein receiving the CP message comprises receiving a DLL PDU (eg, PDCP PDU, RLC PDU, MAC PDU) having a header and a payload, wherein the payload contains at least a portion of the CP message.

[0139] D1. A method performed by a user equipment (UE), the method comprising: creating a control plane (CP) message (eg, a sidelink control plane message), wherein the CP message comprises a data link layer (DLL) address of the UE; and wirelessly transmitting the CP message to a UE relay.

[0140] D2. The method of embodiment D1, wherein the UE is a source UE and the CP message is a security mode complete message (eg, an extended version of the current 3GPP PROSE DIRECT LINK SECURITY MODE COMPLETE message).

[0141] D3. The method of embodiment D1 or D2, further comprising: after sending the CP message, receiving a message including a DLL address of a target UE from the relay.

[0142] D4. The method according to embodiment D3 further includes: after receiving the message including the DLL address of the target UE, creating a first DLL protocol data unit PDU including a payload, the payload including at least a portion of a second DLL PDU (e.g., an Ethernet frame); and sending the first DDL PDU to the UE relay, wherein the destination address of the first DLL PDU is the DLL address of the UE relay, and the destination address of the second DLL PDU is the DLL address of the target UE.

[0143] D5. The method of embodiment D1, wherein the UE is a target UE and the CP message is a communication accept message (eg, an extended version of the current 3GPP direct communication accept message).

[0144] D6. The method of any one of embodiments D1 to D6, wherein the DLL address of the UE is an Ethernet MAC address.

[0145] D7. The method of embodiments D1 to D6, wherein sending the CP message to the UE relay comprises: creating a DLL protocol data unit (PDU) (e.g., a MAC frame, an RLC frame, a PDCP PDU) including a payload, the payload including at least a portion of the CP message, wherein the DLL PDU is addressed to the UE relay; and sending the DDL PDU to the UE relay.

[0146] E1. A user equipment UE relay, the UE relay comprising: a receiver for receiving a first control plane CP message including a DLL address of the first UE from a first UE; and a transmitter for sending a second CP message including the DLL address of the first UE to a second UE.

[0147] E2. The UE relay of embodiment E1, further comprising: a processing circuit configured to cause the UE relay to maintain (eg, create) an association between the DLL address of the first UE and a link established between the first UE and the UE relay.

[0148] E3. The UE relay of embodiment E1 or E2, wherein the first UE is a source UE and the first CP message is a security mode complete message (eg, an extended version of the current 3GPP PROSE DIRECT LINK SECURITY MODE COMPLETE message).

[0149] E4. The UE relay of embodiment E1 or E2, wherein the first UE is a target UE and the first CP message is a communication accept message (eg, an extended version of the current 3GPP direct communication accept message).

[0150] E5. The method of any one of embodiments E1 to E4, wherein the second CP message is a security mode complete message, a communication accept message, a link modification request message, or a link modification accept message.

[0151] E6. The method of any one of embodiments E1 to E5, wherein the first DLL address of the first UE is a first Ethernet MAC address, and the second DLL address of the second UE is a second Ethernet MAC address.

[0152] F1. A method performed by a user equipment (UE) relay, the method comprising: receiving a first control plane (CP) message including a DLL address of the first UE from a first UE; and sending a second CP message including the DLL address of the first UE to a second UE.

[0153] F2. The method of embodiment F1, further comprising maintaining an association between the DLL address of the first UE and the link established between the first UE and the UE relay.

[0154] F3. The method of embodiment F1 or F2, wherein the first UE is a source UE and the first CP message is a security mode complete message (eg, an extended version of the current 3GPP PROSE DIRECT LINK SECURITY MODE COMPLETE message).

[0155] F4. The method of embodiment F1 or F2, wherein the first UE is a target UE and the first CP message is a communication accept message (eg, an extended version of the current 3GPP direct communication accept message).

[0156] F5. The method according to any one of claims F1 to F4, wherein the second CP message is a security mode complete message, a communication accept message, a link modification request message, or a link modification accept message.

[0157] F6. The method according to any one of claims F1 to F5, wherein the first DLL address of the first UE is a first Ethernet MAC address, and the second DLL address of the second UE is a second Ethernet MAC address.

[0158] F7. The method according to any one of claims F1 to F6, wherein sending the second CP message to the second UE comprises: sending a DLL PDU having a header and a payload to the second UE, the payload containing at least a portion of the CP message including the DLL address of the first UE.

[0159] G1. A computer program comprising instructions executable by a processing circuit of a UE for configuring the UE to perform the method of any one of embodiments C1 to C8, D1 to D5, or G1 to G7.

[0160] G2. A carrier embodying the computer program according to embodiment G1, wherein the carrier is one of an electronic signal, an optical signal, a radio signal, and a computer-readable storage medium.

[0161] in conclusion

[0162] As disclosed above, in one embodiment, the present disclosure extends the Direct Communication Request message with an indication of Ethernet traffic. Therefore, relay 102 and target UE 103 are aware that the link between the relay and the target is established for Ethernet traffic. Target UE 103 can include its Ethernet MAC address in the Direct Communication Accept or Link Modification Accept message sent to relay 102, and the UE relay can forward the target UE's Ethernet MAC address to the source UE, and similarly, forward the source UE's Ethernet MAC address to the target UE. This enables the source (or target) UE to construct an Ethernet frame to be sent to the target (or source) UE, with the destination address set to the target (or source) UE's MAC address.

[0163] As also disclosed above, in another embodiment, a UE (source UE or target UE) provides its Ethernet MAC address to the relay. The relay then maintains an association between the Ethernet MAC address and the link (e.g., PC5 link) established between the UE and the relay for routing Ethernet PDUs (also known as Ethernet frames). This is useful when the relay is UE-to-network, as the relay can avoid having to broadcast Ethernet frames received from the network with a destination Ethernet MAC address unknown to the relay for the same RSC to all UEs connected to the relay. This is also useful when the relay is UE-to-UE, as if the relay is serving multiple UEs, it enables the relay to avoid having to broadcast Ethernet frames sent by one of the UEs with a destination Ethernet MAC address unknown to the relay for the same RSC to all other UEs connected to the relay.

[0164] Although various embodiments are described herein, it should be understood that they are presented by way of example only and not limitation. Therefore, the breadth and scope of the present disclosure should not be limited by any of the exemplary embodiments described above. Moreover, unless otherwise indicated herein or clearly contradicted by the context, any combination of the elements described above in all possible variations thereof is encompassed by the present disclosure.

[0165] As used herein, sending a message "to" or "toward" an intended recipient encompasses sending the message directly to the intended recipient or indirectly to the intended recipient (i.e., one or more other nodes are used to relay the message from the source node to the intended recipient). Similarly, as used herein, receiving a message "from" a sender encompasses receiving the message directly from the sender or indirectly from the sender (i.e., one or more nodes are used to relay the message from the sender to the receiving node). Furthermore, as used herein, "a" or "an" means "at least one" or "one or more."

[0166] Furthermore, although the processes described above and illustrated in the accompanying drawings are shown as a series of steps, this is done for illustrative purposes only. Therefore, it is contemplated that steps may be added, steps may be omitted, the order of the steps may be rearranged, and steps may be performed in parallel.

Claims

1. A relay user equipment (UE) (102), the relay UE (102) comprising: A receiver (747) is configured to receive a control plane CP message (m201, m203, m205, m206) sent by a terminal UE (101, 103) to the relay UE, the CP message including a data link layer DLL address of the terminal UE; and A processing circuit (702) is configured to cause the relay UE to maintain an association between the DLL address of the terminal UE and a link established with the terminal UE.

2. The relay UE according to claim 1, wherein: The relay UE is further configured to enable security protection with the terminal UE, and The CP message is sent by the terminal UE to the relay UE after the security protection with the terminal UE is enabled.

3. The relay UE according to claim 1 or 2, wherein: The terminal UE is a source UE (101), and The relay UE further comprises a transmitter (745) for sending a message comprising the DLL address of the source UE to a target UE (103).

4. The relay UE according to claim 3, wherein: The relay UE is further configured to enable security protection with the target UE, and The relay UE is further configured to send the message including the DLL address of the source UE to the target UE after the security protection with the target UE is enabled.

5. The relay UE according to claim 3 or 4, wherein: The relay UE is further configured to obtain the DLL address of the target UE from a message (m207) sent by the target UE to the relay UE, and The relay UE is further configured to send a message (m208, m258) including the DLL address of the target UE to the source UE (101). The relay UE according to claim 1 , wherein: The terminal UE is a target UE (103), and The CP message is an acceptance message.

7. The relay UE according to claim 6, wherein: The relay UE is further configured to send a message including the DLL address of the target UE to the source UE (m208, m258).

8. The relay UE according to any one of claims 1 to 7, wherein: The DLL address of the terminal UE is an Ethernet Media Access Control MAC address.

9. The relay UE according to any one of claims 1 to 8, wherein: The relay UE is a UE-to-UE relay, and The terminal UE is a 5G ProSe terminal UE.

10. The relay UE according to any one of claims 1 to 8, wherein: The relay UE is a UE to network relay, and The terminal UE is a 5G ProSe remote UE.

11. The relay UE according to any one of claims 1 to 10, wherein: Receiving the CP message includes: receiving a DLL protocol data unit (PDU) having a header and a payload, wherein the payload at least includes a portion of the CP message including the DLL address of the terminal UE.

12. The relay UE according to any one of claims 1 to 11, wherein: The DLL address is the Ethernet MAC address, The relay UE is further configured to determine whether the Ethernet MAC address is used by another UE, and The relay UE is further configured to, in response to determining that the Ethernet MAC address is used by another UE, send a message to the terminal UE indicating that there is an Ethernet MAC address conflict.

13. The relay UE according to any one of claims 1 to 12, wherein: The link established with the terminal UE is a PC5 link for transmitting Ethernet services.

14. The relay UE according to claim 1, wherein: The terminal UE is a source UE, The link established with the terminal UE is a PC5 link, The relay UE is further configured such that, if the PC5 link is used to transmit Ethernet traffic, the relay UE sends the Ethernet MAC address of the source UE to the target UE after security with the target UE is enabled.

15. A terminal user equipment (UE) (101, 103), the terminal UE comprising: Receiver (747); as well as A transmitter (745), wherein The terminal UE is configured to use the transmitter to send a control plane CP message including the Ethernet media access control MAC address of the UE to the relay UE (102). The terminal UE according to claim 15 , wherein: The terminal UE is a source UE, and The source UE is further configured to initiate a link establishment procedure with the relay UE before sending the CP message including the Ethernet MAC address, and The source UE is further configured such that, if the link to be established is to be used for transmitting Ethernet traffic, the source UE sends the CP message including the Ethernet MAC address after security protection with the relay UE is enabled. The terminal UE according to claim 15 , wherein: The terminal UE is a source UE (101), and the CP message is a security mode complete message in response to a security command message (m202) sent by the relay UE. The terminal UE according to claim 15 , wherein: The terminal UE is a target UE (103), and the CP message is an acceptance message (m207) in response to a communication request message (m204) sent by the relay UE (102).

19. The terminal UE according to any one of claims 15 to 18, wherein: The UE sends the CP message to the relay by sending a layer 2 protocol data unit (PDU) having a header and a payload to the relay, the payload containing at least a portion of the CP message including the Ethernet MAC address.

20. The terminal UE according to any one of claims 15 to 19, wherein: The terminal UE is further configured to use the transmitter to send a direct communication request DCR to the relay before using the transmitter to send the CP message including the Ethernet MAC address of the terminal UE to the relay.

21. A relay user equipment (UE) (102), the relay UE comprising: A receiver (747) for receiving a first control plane CP message (m203, m207) including a data link layer DLL address of the first UE from the first UE (101, 103); and A transmitter (745) is configured to send a second CP message (m206, m208, m254, m258) including the DLL address of the first UE to a second UE (101, 103), wherein the second CP message is not the first CP message.

22. The relay UE according to claim 21, further comprising: A processing circuit (702) is configured to cause the relay UE to maintain an association between the DLL address of the first UE and a link established between the first UE and the relay UE.

23. The relay UE according to claim 22, wherein: The link established with the terminal UE is a P25 link for transmitting Ethernet services.

24. The relay UE according to any one of claims 21 to 23, wherein: The relay UE is further configured to enable security protection with the second UE, and The relay UE is further configured to send the second CP message including the DLL address of the first UE to the second UE after the security protection with the target UE is enabled.

25. The relay UE according to claim 24, wherein: The relay UE is further configured to obtain the DLL address of the second UE from a message (m207) sent by the second UE to the relay UE, and The relay UE is further configured to send a message including the DLL address of the second UE to the first UE (m208, m258).

26. The relay UE according to any one of claims 21 to 25, wherein: The DLL address of the first UE is an Ethernet MAC address, The relay UE is further configured to determine whether the Ethernet MAC address is used by another UE, and The relay UE is further configured to, in response to determining that the Ethernet MAC address is used by another UE, send a message to the first UE indicating that there is an Ethernet MAC address conflict.

27. The relay UE according to claim 21, wherein: The first UE is a source UE, The second UE is a target UE, The link established with the source UE is a P25 link, and The relay UE is further configured such that, if the P25 link is used to transmit Ethernet traffic, the relay UE sends the DLL address of the source UE to the target UE after security with the target UE is enabled.

28. A method (400) performed by a relay user equipment (UE) (102), the method comprising: receiving (s402) a control plane CP message (m201, m203, m205, m206) sent by a terminal UE (101, 103), the CP message including a data link layer DLL address of the terminal UE; and An association between the DLL address of the terminal UE and the link established with the terminal UE is maintained (s404).

29. The method according to claim 28, wherein The method further includes: enabling security protection with the terminal UE, and The CP message is sent by the terminal UE after the security protection with the terminal UE is enabled.

30. The method according to claim 28 or 29, wherein The terminal UE is a source UE (101), The method further comprises: sending a message including the DLL address of the source UE to a target UE (103), The method further includes: enabling security protection with the target UE, The message including the DLL address of the source UE is sent to the target UE after the security protection with the target UE is enabled, The method further comprises: obtaining the DLL address of the target UE from a message (m207) sent by the target UE, and A message including the DLL address of the target UE is sent to the source UE (m208, m258).

31. The method of claim 28, wherein The terminal UE is a target UE (103), The CP message is an acceptance message, and The method further includes sending a message including the DLL address of the target UE to the source UE (m208, m258).

32. The method according to any one of claims 28 to 31, wherein The DLL address of the terminal UE is a media access control MAC address.

33. The method according to any one of claims 28 to 32, wherein: The relay UE is a UE-to-UE relay, and The terminal UE is a 5G ProSe terminal UE.

34. The method according to any one of claims 28 to 32, wherein The relay UE is a UE to network relay, and The terminal UE is a 5G ProSe remote UE.

35. The method according to any one of claims 28 to 34, wherein Receiving the CP message includes: receiving a DLL protocol data unit (PDU) having a header and a payload, wherein the payload at least includes a portion of the CP message including the DLL address of the terminal UE.

36. The method according to any one of claims 28 to 35, wherein The DLL address is the Ethernet MAC address, The method further includes determining whether the Ethernet MAC address is used by another UE, and The method further includes, in response to determining that the Ethernet MAC address is used by another UE, sending a message to the terminal UE indicating that an Ethernet MAC address conflict exists.

37. The method of claim 28, wherein: The terminal UE is a source UE, The link established with the terminal UE is a PC5 link, and The relay UE is further configured such that, if the PC5 link is used to transmit Ethernet traffic, the relay UE sends the Ethernet MAC address of the source UE to the target UE after security with the target UE is enabled.

38. A method (500) performed by an end user equipment (UE) (101, 103), the method comprising: Creating (s502) a control plane CP message, wherein the CP message includes a data link layer DLL address of the terminal UE; and The CP message is wirelessly transmitted (s504) to the UE relay (102).

39. The method according to claim 38, wherein The terminal UE is a source UE, and The method includes: the source UE initiating a link establishment process with the relay UE before wirelessly sending the CP message to the relay UE, and The source UE is further configured such that, if the link to be established is to be used for transmitting Ethernet traffic, the source UE sends the CP message including the Ethernet MAC address after security protection with the relay UE is enabled.

40. The method of claim 38, wherein The terminal UE is a source UE (101), and the CP message is a security mode complete message in response to a security command message (m202) sent by the relay UE, or The terminal UE is a target UE (103), and the CP message is an acceptance message (m207) in response to a communication request message (m204) sent by the relay UE (102).

41. The method according to any one of claims 38 to 40, wherein The method further comprises: after sending the CP message, receiving a message (m208, m258) including a DLL address of a target UE (103) from the relay, The DLL address of the target UE is the Ethernet MAC address of the target UE, and The method further comprises: After receiving the message including the Ethernet MAC address of the target UE, creating a DLL protocol data unit (PDU) including a payload, the payload including at least a portion of an Ethernet frame; and Sending the DLL PDU to the relay UE, wherein: The destination address of the DLL PDU is the DLL address of the relay UE, and The destination address of the Ethernet frame is the Ethernet MAC address of the target UE.

42. The method according to any one of claims 38 to 41, wherein Sending the CP message to the relay UE includes: creating a DLL protocol data unit (PDU) including a payload, the payload including at least a portion of the CP message, the CP message including the DLL address of the terminal UE, wherein the DLL PDU is addressed to the relay UE; and Send the DLL PDU to the relay UE.

43. The method according to any one of claims 38 to 42, wherein The method further includes: before sending the CP message including the DLL address of the terminal UE to the relay: sending a direct communication request DCR to the relay; and A security procedure for establishing security with the relay UE is performed.

44. A method (600) performed by a user equipment (UE) relay (102), the method comprising: receiving (s602) a first control plane CP message (m203, m207) from a first UE (101, 103) including a DLL address of the first UE; and A second CP message (m206, m208, m254, m258) including the DLL address of the first UE is sent (s604) to a second UE (101, 103), wherein the second CP message is not the first CP message.

45. The method of claim 44, wherein: The method further includes maintaining an association between the DLL address of the first UE and a link established between the first UE and the relay UE, and The link established with the terminal UE is a PC5 link for transmitting Ethernet services.

46. The method according to any one of claims 44 to 45, wherein The method further includes: enabling security protection with the second UE, The relay UE is configured to send the second CP message including the DLL address of the first UE to the second UE after the security protection with the target UE is enabled, and The method further comprises: obtaining the DLL address of the second UE from a message (m207) sent by the second UE to the relay UE, and The method further includes sending a message including the DLL address of the second UE to the first UE (m208, m258).

47. The method according to any one of claims 44 to 46, wherein The DLL address of the first UE is an Ethernet MAC address, The method further includes determining whether the Ethernet MAC address is used by another UE, and The method further includes, in response to determining that the Ethernet MAC address is used by another UE, sending a message to the first UE indicating that an Ethernet MAC address conflict exists.

48. The method of claim 44, wherein The first UE is a source UE, The second UE is a target UE, The link established with the source UE is a PC5 link, and The relay UE is further configured such that, if the PC5 link is used to transmit Ethernet traffic, the relay UE sends the DLL address of the source UE to the target UE after security with the target UE is enabled.

49. A computer program (743) comprising instructions (744) executable by a processing circuit (702) of a UE (101, 102, 103) for configuring the UE to perform the method according to any one of the above method claims.

50. A carrier comprising the computer program according to claim 49, wherein The carrier is one of an electronic signal, an optical signal, a radio signal, and a computer-readable storage medium (742).

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