Medium access control (MAC) access conflict support for wireless transmit / receive unit (WTRU) to WTRU relay

Abstract

A relay node may detect conflicts associated with a medium access control (MAC) address. A source node may send a request to the relay node. The request may be a request for establishing communication with a target node. The source node may send an indication of the MAC address of the source node to the relay node. The source node may receive a rejection message from the relay node. The rejection message may include an indication of a collision associated with the MAC address of the source node.

Description

Cross-reference to related applications

[0001] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 527,379, filed July 18, 2023, which is incorporated herein by reference in its entirety. Background Technology

[0002] The existing process allows the establishment of a PC5 link between a source user equipment (UE) and a destination UE via a UE-to-UE (U2U) relay, even if the source UE's MAC (Media Access Control) address is not unique. Furthermore, a PC5 link can be established even when a MAC address conflict is detected. Therefore, when traffic with a non-unique destination MAC address is received, the relay may be unable to determine which PC5 link to forward the traffic to. This could lead the relay to forward traffic to the wrong source UE or discard traffic with a non-unique MAC address. Summary of the Invention

[0003] The UE may also be referred to herein as a Wireless Transmit / Receive Unit (WTRU). Throughout the specification and figures, the terms UE and WTRU are used interchangeably. A relay may be referred to as a relay node. Throughout the specification and figures, the terms relay and relay node are used interchangeably. A relay may include a WTRU, a UE, or any suitable device. This document describes methods and devices for MAC access conflict support for UE-UE (also known as WTRU-WTRU or U2U) relays. The terms relay and relay node are used interchangeably.

[0004] As described in this document with various examples, a relay node can detect a conflict with the Media Access Control (MAC) address of the source WTRU. This conflict can indicate that the MAC address is not unique. The relay can request a new MAC address from the source WTRU. The relay can assign a new MAC address to the source WTRU. The source WTRU can provide a list of MAC addresses, and the relay can select a MAC address from the list. For example, this selection can be made from the list during PC5 link establishment. The relay can detect a conflict with the MAC address of the destination WTRU. The relay can request a new MAC address from the destination WTRU. The relay can trigger a Link Identifier Update (LIU) procedure with the destination WTRU. The relay can release the current PC5 link and restart the PC5 link establishment process. The relay can assign a new MAC address to the destination WTRU after the PC5 link is established. The destination WTRU can provide a list of MAC addresses. The relay can select a MAC address for the destination WTRU after the PC5 link is established. The source WTRU can detect a MAC address conflict. The source WTRU can associate the new MAC address with the destination WTRU. The source WTRU can release the PC5 link. The destination WTRU can detect MAC address conflicts. The destination WTRU can send a list of MAC addresses for the source WTRU. The relay can update the list before sending it to the source WTRU. WTRUs communicating can negotiate MAC address values. Each WTRU (e.g., the initiating WTRU and the destination WTRU) can generate a partial MAC address to create the final MAC address.

[0005] An exemplary method for managing MAC address conflicts can be performed by a relay node. The method may include the relay node receiving a Direct Communication Request (DCR) message from a Wireless Transmit / Receive Unit (WTRU). The relay node may send a Direct Security Mode (DSM) command message to the WTRU. The relay node may receive a DSM Completion message from the WTRU, wherein the DSM Completion message contains a first Media Access Control (MAC) address associated with the WTRU. The relay node may determine that the first MAC address associated with the WTRU is not unique. The relay node may send a PC5 Request message to the WTRU, wherein the PC5 Request message contains a request for a new MAC address. The relay node may receive a PC5 Response message from the WTRU, wherein the PC5 Response message contains an indication of a second MAC address. The relay node may determine that the second MAC address is unique. The relay node may send a Direct Communication Accept (DCA) message to the WTRU, wherein the DCA message may contain an indication that the second MAC address is associated with a first WTRU. The received indication of the second MAC address may contain the new MAC address.

[0006] An exemplary method for managing MAC address conflicts can be performed by a relay node. The relay node can establish a link with a first Wireless Transmit / Receive Unit (WTRU). The relay node can receive a first Media Access Control (MAC) address associated with the first WTRU. The relay node can establish a link with a second WTRU. The relay node can receive a second MAC address associated with the second WTRU. The relay node can determine a conflict between the first MAC address and the second MAC address. The relay node can request a new MAC address from the second WTRU. The relay node can receive a third MAC address from the second WTRU. The relay node can establish a link with the second WTRU based on the third MAC address.

[0007] An exemplary relay node configured to manage MAC address conflicts may include a transceiver and a processor. The processor may be configured to receive a Direct Communication Request (DCR) message from a Wireless Transmit / Receive Unit (WTRU) via the transceiver. The processor may be configured to send a Direct Security Model (DSM) command message to the WTRU via the transceiver. The processor may be configured to receive a DSM Completion message from the WTRU via the transceiver, wherein the DSM Completion message contains a first Media Access Control (MAC) address associated with the WTRU. The processor may be configured to determine that the first MAC address associated with the WTRU is not unique. The processor may be configured to send a PC5 Request message to the WTRU via the transceiver, wherein the PC5 Request message contains a request for a new MAC address. The processor may be configured to receive a PC5 Response message from the WTRU via the transceiver, wherein the PC5 Response message contains an indication of a second MAC address. The processor may be configured to determine that the second MAC address is unique. The processor may be configured to send a Direct Communication Accept (DCA) message to the WTRU via the transceiver, wherein the DCA message contains an indication that the second MAC address is associated with a first WTRU. The indication of the received second MAC address may include a new MAC address.

[0008] An exemplary relay node configured to manage MAC conflicts may include a transceiver and a processor. The processor may be configured to establish a link with a first Wireless Transmit / Receive Unit (WTRU) via the transceiver. The processor may be configured to receive a first Media Access Control (MAC) address associated with the first WTRU via the transceiver. The processor may be configured to establish a link with a second WTRU via the transceiver. The processor may be configured to receive a second MAC address associated with the second WTRU via the transceiver. The processor may be configured to determine a conflict between the first MAC address and the second MAC address. The processor may be configured to request a new MAC address from the second WTRU via the transceiver. The processor may be configured to receive a third MAC address from the second WTRU via the transceiver. The processor may be configured to establish a link with the second WTRU via the transceiver based on the third MAC address.

[0009] At least one exemplary computer-readable storage medium for managing MAC address conflicts may contain executable instructions, wherein the at least one computer-readable storage medium is not a transient signal. When executed, the executable instructions may configure at least one processor to establish a link with a first wireless transmit / receive unit (WTRU). Execution of the instructions may configure at least one processor to receive a first media access control (MAC) address associated with the first WTRU. Execution of the instructions may configure at least one processor to establish a link with a second WTRU. Execution of the instructions may configure at least one processor to receive a second MAC address associated with the second WTRU. Execution of the instructions may configure at least one processor to determine a conflict between the first MAC address and the second MAC address. Execution of the instructions may configure at least one processor to request a new MAC address from the second WTRU. Execution of the instructions may configure at least one processor to receive a third MAC address from the second WTRU. Execution of the instructions may configure at least one processor to establish a link with the second WTRU based on the third MAC address.

[0010] At least one exemplary computer-readable storage medium for managing MAC address conflicts may contain executable instructions, wherein the at least one computer-readable storage medium is not a transient signal. When executed, the executable instructions may configure at least one processor to receive a Direct Communication Request (DCR) message from a Wireless Transmit / Receive Unit (WTRU). Execution of the instructions may configure at least one processor to send a Direct Security Model (DSM) command message to the WTRU. Execution of the instructions may configure at least one processor to receive a DSM Completion message from the WTRU, wherein the DSM Completion message contains a first Media Access Control (MAC) address associated with the WTRU. Execution of the instructions may configure at least one processor to determine that the first MAC address associated with the WTRU is not unique. Execution of the instructions may configure at least one processor to send a PC5 Request message to the WTRU, wherein the PC5 Request message contains a request for a new MAC address. Execution of the instructions may configure at least one processor to receive a PC5 Response message from the WTRU, wherein the PC5 Response message contains an indication of a second MAC address. Execution of the instructions may configure at least one processor to determine that the second MAC address is unique. The execution of the instructions can configure at least one processor to send a Direct Communication Acceptance (DCA) message to the WTRU, wherein the DCA message contains an indication that a second MAC address is associated with the first WTRU. The indication of the received second MAC address may contain a new MAC address.

[0011] An exemplary first WTRU for performing WTRU-to-WTRU communication may include a transceiver and a processor. The processor may be configured to receive a Direct Communication Request (DCR) message from a second WTRU via the transceiver. The DCR message may contain an indication of a request for the first WTRU to establish a link with a third WTRU. The link may be configured to relay traffic from the second WTRU to the third WTRU and vice versa. The processor may be configured to send a Direct Security Mode (DSM) command message to the second WTRU via the transceiver. The processor may be configured to receive a response message from the second WTRU via the transceiver. The response message may contain an indication of the Media Access Control (MAC) address associated with the second WTRU. The processor may be configured to detect a MAC address conflict associated with the MAC address of the second WTRU. The processor may be configured to send a Direct Communication (DC) Reject message to the second WTRU via the transceiver based on the detected MAC address conflict. The DC Reject message may include a reason code indicating a MAC address conflict associated with the MAC address of the second WTRU (e.g., a reason code indicating that the MAC address of the second WTRU is not unique). The response message may include a DSM Completion message. The DSM Command message may be configured to establish a secure link between the first WTRU and the second WTRU. The MAC address conflict associated with the MAC address of the second WTRU may correspond to the MAC address of the second WTRU being used by another WTRU associated with the first WTRU. The processor may be configured to receive a second DCR message from the second WTRU after sending the DC Reject message. The second DCR message may include an indication of a second request for the first WTRU to establish a link with the third WTRU. The processor may be configured to send a second DSM Command message to the second WTRU. The processor may be configured to receive a second response message from the second WTRU. The second response message may include a DSM Completion message and may include an indication of the second MAC address of the second WTRU.

[0012] An exemplary method for performing WTRU-to-WTRU communication can be performed by a first WTRU. The method may include receiving a Direct Communication Request (DCR) message from a second WTRU. The DCR message may contain an indication of a request for the first WTRU to establish a link with a third WTRU. The link may be configured to relay traffic from the second WTRU to the third WTRU and from the third WTRU to the second WTRU. The method may include sending a Direct Security Mode (DSM) command message to the second WTRU. The method may include receiving a response message from the second WTRU. The response message may contain an indication of a Media Access Control (MAC) address associated with the second WTRU. The method may include detecting a MAC address conflict associated with the MAC address of the second WTRU. The method may include sending a Direct Communication (DC) Reject message to the second WTRU based on the detected MAC address conflict associated with the second WTRU's MAC address. The DC Reject message may contain a reason code indicating a MAC address conflict associated with the second WTRU's MAC address (e.g., a reason code indicating that the second WTRU's MAC address is not unique). The response message may contain a DSM Complete message. The DSM command message can be configured to establish a secure link between a first WTRU and a second WTRU. A MAC address conflict associated with the MAC address of the second WTRU may correspond to another WTRU associated with the first WTRU using the MAC address of the second WTRU. The method may include receiving a second DCR message from the second WTRU after sending a DC rejection message. The second DCR message may contain an indication of a second request for the first WTRU to establish a link with a third WTRU. The method may include sending a second DSM command message to the second WTRU. The method may include receiving a second response message from the second WTRU. The second response message may contain a DSM completion message and may contain an indication of the second WTRU's second MAC address.

[0013] At least one exemplary non-transitory computer-readable storage medium may contain executable instructions for configuring at least one processor to perform WTRU-to-WTRU communication. The executable instructions may configure at least one processor to receive a Direct Communication Request (DCR) message from a second WTRU by a first WTRU. The DCR message may contain an indication of a request for the first WTRU to establish a link with a third WTRU. The link may be configured to relay traffic from the second WTRU to the third WTRU and vice versa. The executable instructions may configure at least one processor to send a Direct Security Model (DSM) command message to the second WTRU. The executable instructions may configure at least one processor to receive a response message from the second WTRU. The response message may contain an indication of a Media Access Control (MAC) address associated with the second WTRU. The processor may be configured to detect a MAC address conflict associated with the MAC address of the second WTRU. The processor may be configured to send a Direct Communication (DC) Reject message to the second WTRU via a transceiver based on the detected MAC address conflict. The DC Reject message may include a reason code indicating a MAC address conflict associated with the MAC address of the second WTRU (e.g., a reason code indicating that the MAC address of the second WTRU is not unique). The response message may include a DSM Completion message. The DSM Command message may be configured to establish a secure link between the first WTRU and the second WTRU. The MAC address conflict associated with the MAC address of the second WTRU may correspond to the MAC address of the second WTRU being used by another WTRU associated with the first WTRU. Executable instructions may configure at least one processor to receive a second DCR message from the second WTRU after sending the DC Reject message. The second DCR message may include an indication of a second request for the first WTRU to establish a link with the third WTRU. Executable instructions may configure at least one processor to send a second DSM Command message to the second WTRU. Executable instructions may configure at least one processor to receive a second response message from the second WTRU. The second response message may include a DSM Completion message and may include an indication of the second MAC address of the second WTRU.

[0014] An exemplary first WTRU for performing WTRU-to-WTRU communication may include a transceiver and a processor. The processor may be configured to receive a first Direct Communication Request (DCR) message from a second WTRU via the transceiver. The first DCR message may contain an indication of a request for the first WTRU to establish a link with a third WTRU. The link may be configured to relay traffic between the second and third WTRUs. The processor may be configured to send a second DCR message to the third WTRU via the transceiver. The processor may be configured to receive a response message from the third WTRU via the transceiver. The response message may contain an indication of the media access control (MAC) address of the third WTRU. The processor may be configured to detect a MAC address conflict associated with the MAC address of the third WTRU. The processor may be configured to send a Link Release (LR) request message to the third WTRU via the transceiver based on the detected MAC address conflict. The LR request message may contain a reason code indicating a MAC address conflict with the third WTRU (e.g., a reason code indicating that the MAC address of the second WTRU is not unique). The response message may contain a Direct Communication Accept (DCA) message. The processor can be configured to establish a first secure link with a second WTRU. The processor can be configured to establish a second secure link with a third WTRU. The first secure link can be a PC5 link. The second secure link can be a PC5 link. The LR request message can contain one or more alternative MAC addresses for the third WTRU. The processor can be configured to receive an LR response message from the third WTRU. The processor can be configured to send a third DCR message to the third WTRU. The processor can be configured to receive a DC Accept (DCA) message from the third WTRU, which can contain an indication of a MAC address selected from one or more alternative MAC addresses for the third WTRU.

[0015] An exemplary method for performing WTRU-to-WTRU communication can be performed by a first WTRU. The method may include receiving a first Direct Communication Request (DCR) message from a second WTRU. The first DCR message may contain an indication of a request for the first WTRU to establish a link with a third WTRU. The link may be configured to relay traffic between the second and third WTRUs. The method may include sending a second DCR message to the third WTRU. The method may include receiving a response message from the third WTRU. The response message may contain an indication of the media access control (MAC) address of the third WTRU. The method may include detecting a MAC address conflict associated with the MAC address of the third WTRU. The method may include sending a Link Release (LR) request message to the third WTRU based on the detected MAC address conflict associated with the MAC address of the third WTRU. The LR request message may contain a reason code indicating a conflict with the MAC address of the third WTRU (e.g., a reason code indicating that the MAC address of the second WTRU is not unique). The response message may contain a Direct Communication Accept (DCA) message. The method may include establishing a first secure link with the second WTRU. The method may include establishing a second secure link with the third WTRU. The first secure link can be a PC5 link. The second secure link can be a PC5 link. The LR request message can contain one or more alternative MAC addresses for the third WTRU. The method can include receiving an LR response message from the third WTRU. The method can include sending a third DCR message to the third WTRU. The method can include receiving a DC Accept (DCA) message from the third WTRU, which may contain an indication of a MAC address selected from one or more alternative MAC addresses for the third WTRU.

[0016] At least one exemplary non-transitory computer-readable storage medium may contain executable instructions configured to perform WTRU-to-WTRU communication. The executable instructions may configure at least one processor to receive a first Direct Communication Request (DCR) message from a second WTRU. The first DCR message may contain an indication of a request for the first WTRU to establish a link with a third WTRU. The link may be configured to relay traffic between the second and third WTRUs. The executable instructions may configure at least one processor to send a second DCR message to the third WTRU. The executable instructions may configure at least one processor to receive a response message from the third WTRU. The response message may contain an indication of the media access control (MAC) address of the third WTRU. The executable instructions may configure at least one processor to detect a MAC address conflict associated with the MAC address of the third WTRU. The executable instructions may configure at least one processor to send a Link Release (LR) request message to the third WTRU based on the detected MAC address conflict associated with the MAC address of the third WTRU. The LR request message may contain a reason code indicating a conflict with the MAC address of the third WTRU (e.g., a reason code indicating that the MAC address of the second WTRU is not unique). The response message may contain a Direct Communication Acceptance (DCA) message. Executable instructions may configure at least one processor to establish a first secure link with the second WTRU. Executable instructions may configure at least one processor to establish a second secure link with the third WTRU. The first secure link may be a PC5 link. The second secure link may be a PC5 link. The LR request message may contain one or more alternative MAC addresses for the third WTRU. Executable instructions may configure at least one processor to receive an LR response message from the third WTRU. Executable instructions may configure at least one processor to send a third DCR message to the third WTRU. Executable instructions may configure at least one processor to receive a DC Acceptance (DCA) message from the third WTRU, which may contain an indication of a MAC address selected from one or more alternative MAC addresses for the third WTRU.

[0017] An exemplary first WTRU for performing WTRU-to-WTRU communication may include a transceiver and a processor. The processor may be configured to send a Direct Communication Request (DCR) message to a second WTRU via the transceiver. The DCR message may contain an indication of a request for the first WTRU to establish a link with a third WTRU. This link may be configured to relay traffic between the first and third WTRUs. The processor may be configured to receive a Direct Security Mode (DSM) command message from the second WTRU via the transceiver. The processor may be configured to send a response message to the second WTRU via the transceiver. This response message may contain an indication of the media access control (MAC) address of the first WTRU. The processor may be configured to receive a Direct Communication (DC) Reject message from the second WTRU via the transceiver. This DC Reject message may contain a reason code indicating a MAC address conflict associated with the MAC address of the first WTRU. The response message may contain a DSM Complete message. The DSM command message may be configured to establish a secure link between the first and second WTRUs. A MAC address conflict associated with the MAC address of the first WTRU may correspond to the MAC address of the first WTRU being used by another WTRU associated with the second WTRU. The processor may be configured to send a second DCR message to the second WTRU upon receiving a DC rejection message, wherein the second DCR message may contain an indication of a second request for the first WTRU to establish a link with the third WTRU. The processor may be configured to receive a second DSM command message from the second WTRU. The processor may be configured to send a second response message to the second WTRU, wherein the second response message may contain a DSM completion message, and wherein the second response message may contain an indication of the second Media Access Control (MAC) address of the first WTRU.

[0018] An exemplary method for performing WTRU-to-WTRU communication can be performed by a first WTRU. The method may include sending a Direct Communication Request (DCR) message to a second WTRU. The DCR message may contain an indication of a request for the first WTRU to establish a link with a third WTRU. The link may be configured to relay traffic between the first and third WTRUs. The method may include receiving a Direct Security Mode (DSM) command message from the second WTRU. The method may include sending a response message to the second WTRU. The response message may contain an indication of the media access control (MAC) address of the first WTRU. The method may include receiving a Direct Communication (DC) Reject message from the second WTRU. The DC Reject message may contain a reason code indicating a MAC address conflict associated with the MAC address of the first WTRU. The response message may contain a DSM Complete message. The DSM command message may be configured to establish a secure link between the first and second WTRUs. The MAC address conflict associated with the MAC address of the first WTRU may correspond to the MAC address of the first WTRU being used by another WTRU associated with the second WTRU. The method may include, upon receiving a DC rejection message, sending a second DCR message to a second WTRU, wherein the second DCR message may contain an indication of a second request for the first WTRU to establish a link with the third WTRU. The method may include receiving a second DSM command message from the second WTRU. The method may include sending a second response message to the second WTRU, wherein the second response message may contain a DSM completion message, and wherein the second response message may contain an indication of a second Media Access Control (MAC) address of the first WTRU.

[0019] At least one exemplary non-transitory computer-readable storage medium may contain executable instructions configured to perform WTRU-to-WTRU communication. The executable instructions may configure at least one processor to send a Direct Communication Request (DCR) message to a second WTRU. The DCR message may contain an indication of a request for a link to be established between a first WTRU and a third WTRU. The link may be configured to relay traffic between the first and third WTRUs. The executable instructions may configure at least one processor to receive a Direct Security Mode (DSM) command message from the second WTRU. The executable instructions may configure at least one processor to send a response message to the second WTRU. The response message may contain an indication of the Media Access Control (MAC) address of the first WTRU. The executable instructions may configure at least one processor to receive a Direct Communication (DC) Reject message from the second WTRU. The DC Reject message may contain a reason code indicating a MAC address conflict associated with the MAC address of the first WTRU. The response message may contain a DSM Completion message. The DSM command message may be configured to establish a secure link between the first and second WTRUs. A MAC address conflict associated with the MAC address of the first WTRU may correspond to the MAC address of the first WTRU being used by another WTRU associated with the second WTRU. Executable instructions may configure at least one processor to send a second DCR message to the second WTRU upon receiving a DC rejection message, wherein the second DCR message may contain an indication of a second request for the first WTRU to establish a link with the third WTRU. Executable instructions may configure at least one processor to receive a second DSM command message from the second WTRU. Executable instructions may configure at least one processor to send a second response message to the second WTRU, wherein the second response message may contain a DSM completion message, and wherein the second response message may contain an indication of the second Media Access Control (MAC) address of the first WTRU.

[0020] An exemplary first WTRU for performing WTRU-to-WTRU communication may include a transceiver and a processor. The processor may be configured to receive a Direct Communication Request (DCR) message from a second WTRU via the transceiver. The processor may be configured to send a response message to the second WTRU via the transceiver. The response message may contain an indication of the media access control (MAC) address of the first WTRU. The processor may be configured to receive a Link Release (LR) Request message from the second WTRU via the transceiver. The LR request message may contain a reason code indicating a MAC address conflict associated with the MAC address of the first WTRU. The DCR message may contain an indication of a request for the first WTRU to establish communication with a third WTRU. A MAC address conflict associated with the MAC address of the first WTRU may include a conflict between the MAC address of the first WTRU and the MAC address of another WTRU associated with the second WTRU. The response message may contain a Direct Communication Accept (DCA) message. The processor may be configured to establish a PC5 secure link with the second WTRU. The LR request message contains one or more alternative MAC addresses for the first WTRU. The processor may be configured to send an LR response message to the second WTRU. The processor can be configured to send a DC Accept (DCA) message to the second WTRU. The DCA message may contain an indication of a MAC address selected from one or more alternative MAC addresses used for the first WTRU.

[0021] An exemplary method for performing WTRU-to-WTRU communication can be performed by a first WTRU. The method may include receiving a Direct Communication Request (DCR) message from a second WTRU. The method may include sending a response message to the second WTRU. The response message may contain an indication of the Media Access Control (MAC) address of the first WTRU. The method may include receiving a Link Release (LR) Request message from the second WTRU. The LR Request message may contain a reason code indicating a MAC address conflict associated with the MAC address of the first WTRU. The DCR message may contain an indication of a request for the first WTRU to establish communication with a third WTRU. A MAC address conflict associated with the MAC address of the first WTRU may include a conflict between the MAC address of the first WTRU and the MAC address of another WTRU associated with the second WTRU. The response message may contain a Direct Communication Accept (DCA) message. The method may include establishing a PC5 secure link with the second WTRU. The LR Request message contains one or more alternative MAC addresses for the first WTRU. The method may include sending an LR response message to the second WTRU. The method may include sending a DC Accept (DCA) message to the second WTRU. The DCA message may contain an indication of the MAC address selected from one or more alternative MAC addresses used for the first WTRU.

[0022] At least one exemplary non-transitory computer-readable storage medium may contain executable instructions for configuring at least one processor to perform WTRU-to-WTRU communication. The executable instructions may configure at least one processor to receive a Direct Communication Request (DCR) message from a second WTRU. The executable instructions may configure at least one processor to send a response message to the second WTRU. The response message may contain an indication of the Media Access Control (MAC) address of the first WTRU. The executable instructions may configure at least one processor to receive a Link Release (LR) Request message from the second WTRU. The LR request message may contain a cause code indicating a MAC address conflict associated with the MAC address of the first WTRU. The DCR message may contain an indication of a request for the first WTRU to establish communication with a third WTRU. A MAC address conflict associated with the MAC address of the first WTRU may include a conflict between the MAC address of the first WTRU and the MAC address of another WTRU associated with the second WTRU. The response message may contain a Direct Communication Accept (DCA) message. The executable instructions may configure at least one processor to establish a PC5 secure link with the second WTRU. The LR request message contains one or more alternative MAC addresses for the first WTRU. Executable instructions can configure at least one processor to send an LR response message to the second WTRU. Executable instructions can also configure at least one processor to send a DC accept (DCA) message to the second WTRU. The DCA message may contain an indication of a MAC address selected from one or more alternative MAC addresses for the first WTRU. Attached Figure Description

[0023] A more detailed understanding can be obtained from the following detailed description given by way of example in conjunction with the accompanying drawings. As with the detailed description, the figures in these drawings are illustrative. Therefore, the figures and detailed description should not be considered limiting, and other equally valid examples are possible. The same reference numerals (“ref.” or “refs.”) in the figures indicate the same elements.

[0024] Figure 1A This is an exemplary system diagram illustrating an exemplary communication system that can implement one or more of the disclosed embodiments.

[0025] Figure 1B This illustrates that, according to an embodiment, it is possible to Figure 1A An exemplary system diagram of an exemplary wireless transmit / receive unit (WTRU) used within the communication system shown.

[0026] Figure 1C This illustrates that, according to an embodiment, it is possible to Figure 1AAn exemplary system diagram of an exemplary radio access network (RAN) and an exemplary core network (CN) used within the communication system shown.

[0027] Figure 1D This illustrates that, according to an embodiment, it is possible to Figure 1A An exemplary system diagram of another exemplary RAN and another exemplary CN used in the communication system shown.

[0028] Figure 2 This is a diagram depicting an exemplary fifth-generation (5G) ProSe (proximity-based service or proximity service) communication via 5G ProSe layer 3 UE to UE relay.

[0029] Figure 3 An exemplary process is described in which a relay detects a conflict between the MAC address of the source WTRU and other MAC addresses.

[0030] Figure 4 An exemplary process for a relay to select the MAC address of the source WTRU is described.

[0031] Figure 5 An exemplary process is described in which a relay detects a conflict between the MAC address of the target WTRU and other MAC addresses.

[0032] Figure 6 An exemplary process is described that provides a list of MAC addresses for the target WTRU or relay.

[0033] Figure 7 An exemplary process is described in which a relay detects a conflict between the MAC address of the source WTRU and other MAC addresses.

[0034] Figure 8 An exemplary process is described in which the target WTRU detects a conflict between the MAC address of the source WTRU and other MAC addresses.

[0035] Figure 9 An exemplary process for conflict-free MAC address negotiation is described.

[0036] Figure 10 An exemplary process for updating conflict-free MAC addresses is described.

[0037] Figure 11 An exemplary process for conflict-free MAC address negotiation via U2U relay is described. Detailed Implementation

[0038] Figure 1AThis diagram illustrates an exemplary communication system 100 that can implement one or more of the disclosed embodiments. The communication system 100 may be a multiple access system providing content such as voice, data, video, messaging, and broadcasting to multiple wireless users. The communication system 100 enables multiple wireless users to access such content through shared system resources including wireless broadband. For example, the communication system 100 may employ one or more channel access methods, such as Code Division Multiple Access (CDMA), Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA), Orthogonal FDMA (OFDMA), Single Carrier FDMA (SC-FDMA), Zero-Tail Unique Word DFT Extended OFDM (ZT UW DTS-s OFDM), Unique Word OFDM (UW-OFDM), Resource Block Filtered OFDM, Filter Bank Multicarrier (FBMC), etc.

[0039] like Figure 1A As shown, the communication system 100 may include wireless transmit / receive units (WTRUs) 102a, 102b, 102c, 102d, RAN 104 / 113, CN 106 / 115, public switched telephone network (PSTN) 108, Internet 110, and other networks 112. However, it will be understood that the disclosed embodiments contemplate any number of WTRUs, base stations, networks, and / or network elements. Each of the WTRUs 102a, 102b, 102c, and 102d may be any type of device configured to operate and / or communicate in a wireless environment. For example, WTRUs 102a, 102b, 102c, and 102d (any of which may be referred to as a “station” and / or “STA”) may be configured to transmit and / or receive wireless signals and may include user equipment (UE), mobile stations, fixed or mobile subscriber units, subscription-based units, pagers, cellular phones, personal digital assistants (PDAs), smartphones, laptops, netbooks, personal computers, wireless sensors, hotspots or Mi-Fi devices, Internet of Things (IoT) devices, watches or other wearable devices, head-mounted displays (HMDs), vehicles, drones, medical devices and applications (e.g., remote surgery), industrial devices and applications (e.g., robots and / or other wireless devices operating in the context of industrial and / or automated processing chains), consumer electronics devices, devices operating on commercial and / or industrial wireless networks, etc. Any of WTRUs 102a, 102b, 102c, and 102d may be interchangeably referred to as a UE. Furthermore, any descriptions of UEs referred to herein may equally apply to WTRUs ( Conversely However For example, the WTRU can be configured to execute any procedure or program as described herein, such as that performed by the UE. vice versa ).

[0040] The communication system 100 may also include base station 114a and / or base station 114b. Each of base stations 114a and 114b may be any type of device configured to wirelessly interface with at least one of WTRUs 102a, 102b, 102c, and 102d to facilitate access to one or more communication networks such as CN 106 / 115, Internet 110, and / or other networks 112. By way of example, base stations 114a and 114b may be base transceiver stations (BTS), Node-B, eNode B, home Node-B, home eNode B, next-generation node B (gNB), NR NodeB, site controller, access point (AP), wireless router, etc. Although base stations 114a and 114b are each depicted as a single element, it will be understood that base stations 114a and 114b may include any number of interconnected base stations and / or network elements.

[0041] Base station 114a may be part of RAN 104 / 113, which may also include other base stations and / or network elements (not shown), such as base station controllers (BSCs), radio network controllers (RNCs), relay nodes, etc. Base station 114a and / or base station 114b may be configured to transmit and / or receive radio signals on one or more carrier frequencies, which may be referred to as cells (not shown). These frequencies may be in licensed spectrum, unlicensed spectrum, or a combination of licensed and unlicensed spectrum. A cell may provide coverage for a specific geographic area that may be relatively fixed or may change over time. A cell may also be divided into cell sectors. For example, the cell associated with base station 114a may be divided into three sectors. Therefore, in one embodiment, base station 114a may include three transceivers, i.e., one transceiver for each sector of the cell. In embodiments, base station 114a may employ multiple-input multiple-output (MIMO) technology and may utilize multiple transceivers for each sector of the cell. For example, beamforming may be used to transmit and / or receive signals in a desired spatial direction.

[0042] Base stations 114a and 114b can communicate with one or more of WTRUs 102a, 102b, 102c, and 102d via air interface 116, which can be any suitable wireless communication link (e.g., radio frequency (RF), microwave, centimeter wave, micrometer wave, infrared (IR), ultraviolet (UV), visible light, etc.). Any suitable air interface access technology (RAT) can be used to establish air interface 116.

[0043] More specifically, as described above, the communication system 100 can be a multiple access system and can employ one or more channel access schemes, such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, etc. For example, base station 114a in RAN 104 / 113 and WTRUs 102a, 102b, 102c can implement radio technologies, such as using Wideband CDMA (WCDMA) to establish Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access (UTRA) for air interfaces 115 / 116 / 117. WCDMA can include communication protocols such as High-Speed ​​Packet Access (HSPA) and / or Evolved HSPA (HSPA+). HSPA can include High-Speed ​​Downlink (DL) Packet Access (HSDPA) and / or High-Speed ​​UL Packet Access (HSUPA).

[0044] In one embodiment, base station 114a and WTRUs 102a, 102b, 102c can implement radio technologies such as Evolved UMTS Terrestrial Radio Access (E-UTRA), which can use Long Term Evolution (LTE) and / or LTE-Advanced (LTE-A) and / or LTE-Advanced Pro (LTE-A Pro) to establish air interface 116.

[0045] In one embodiment, base station 114a and WTRUs 102a, 102b, 102c can implement radio technologies such as NR radio access, which can use New Radio (NR) to establish air interface 116.

[0046] In one embodiment, base station 114a and WTRUs 102a, 102b, and 102c can implement multiple air interface access technologies. For example, base station 114a and WTRUs 102a, 102b, and 102c can, for instance, use the dual connectivity (DC) principle to jointly implement LTE radio access and NR radio access. Therefore, the air interface used by WTRUs 102a, 102b, and 102c can be characterized by multiple types of radio access technologies and / or transmissions sent to / from multiple types of base stations (e.g., eNBs and gNBs).

[0047] In other embodiments, base station 114a and WTRUs 102a, 102b, 102c can implement radio technologies such as IEEE 802.11 (i.e., WiFi), IEEE 802.16 (i.e., Global Microwave Interconnection (WiMAX)), CDMA2000, CDMA2000 1X, CDMA2000 EV-DO, Provisional Standard 2000 (IS-2000), Provisional Standard 95 (IS-95), Provisional Standard 856 (IS-856), Global System for Mobile Communications (GSM), Enhanced Data Rate GSM Evolution (EDGE), GSMEDGE (GERAN), etc.

[0048] Figure 1A Base station 114b can be, for example, a wireless router, a home Node-B, a home eNode-B, or an access point, and can utilize any suitable RAT to facilitate wireless connectivity in localized areas such as commercial locations, homes, vehicles, campuses, industrial facilities, air corridors (e.g., for use by drones), roads, etc. In one embodiment, base station 114b and WTRUs 102c, 102d can implement radio technologies such as IEEE 802.11 to establish a wireless local area network (WLAN). In another embodiment, base station 114b and WTRUs 102c, 102d can implement radio technologies such as IEEE 802.15 to establish a wireless personal area network (WPAN). In yet another embodiment, base station 114b and WTRUs 102c, 102d can utilize cellular-based RATs (e.g., WCDMA, CDMA2000, GSM, LTE, LTE-A, LTE-A Pro, NR, etc.) to establish picocells or femtocells. Figure 1A As shown, base station 114b can be directly connected to Internet 110. Therefore, base station 114b does not need to access Internet 110 via CN 106 / 115.

[0049] RAN 104 / 113 can communicate with CN 106 / 115, which can be any type of network configured to provide voice, data, application, and / or Voice over Internet Protocol (VoIP) services to one or more of WTRU 102a, 102b, 102c, and 102d. Data can have different Quality of Service (QoS) requirements, such as different throughput requirements, latency requirements, fault tolerance requirements, reliability requirements, data throughput requirements, mobility requirements, etc. CN 106 / 115 can provide call control, billing services, location-based services, prepaid calling, internet connectivity, video distribution, etc., and / or perform advanced security functions such as user authentication. Although Figure 1AAs not shown, but will be understood, RAN 104 / 113 and / or CN 106 / 115 can communicate directly or indirectly with other RANs using the same RAT as or a different RAT than RAN 104 / 113. For example, in addition to being connected to RAN 104 / 113, which may be utilizing NR radio technology, CN 106 / 115 can also communicate with another RAN (not shown) using GSM, UMTS, CDMA 2000, WiMAX, E-UTRA, or WiFi radio technology.

[0050] CN 106 / 115 can also serve as a gateway for WTRU 102a, 102b, 102c, 102d to access PSTN 108, the Internet 110, and / or other networks 112. PSTN 108 may include a circuit-switched telephone network providing Common Old-Style Telephone Service (POTS). The Internet 110 may include a global system of interconnected computer networks and devices using common communication protocols such as Transmission Control Protocol (TCP), User Datagram Protocol (UDP), and / or Internet Protocol (IP) from the TCP / IP Internet Protocol suite. Network 112 may include wired and / or wireless communication networks owned and / or operated by other service providers. For example, network 112 may include another CN connected to one or more RANs, which may use the same RAT as RAN 104 / 113 or a different RAT.

[0051] Some or all of the WTRUs 102a, 102b, 102c, and 102d in communication system 100 may include multi-mode capabilities (e.g., WTRUs 102a, 102b, 102c, and 102d may include multiple transceivers for communicating with different wireless networks via different wireless links). For example, Figure 1A The WTRU 102c shown can be configured to communicate with a base station 114a that can use cellular-based radio technology and with a base station 114b that can use IEEE 802 radio technology.

[0052] Figure 1B This is a system diagram illustrating example WTRU 102. (See diagram below.) Figure 1B As shown, WTRU 102 may include a processor 118, a transceiver 120, a transmitting / receiving element 122, a speaker / microphone 124, a keypad 126, a display / touchpad 128, non-removable memory 130, removable memory 132, a power supply 134, a Global Positioning System (GPS) chipset 136, and / or other peripheral devices 138, etc. It will be understood that, while remaining consistent with the embodiments, WTRU 102 may include any sub-combination of the foregoing elements.

[0053] Processor 118 may be a general-purpose processor, a special-purpose processor, a conventional processor, a digital signal processor (DSP), multiple microprocessors, one or more microprocessors associated with a DSP core, a controller, a microcontroller, an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA) circuit, any other type of integrated circuit (IC), a state machine, etc. Processor 118 may perform signal encoding, data processing, power control, input / output processing, and / or any other functions that enable WTRU 102 to operate in a wireless environment. Processor 118 may be coupled to transceiver 120, which may be coupled to transmitting / receiving element 122. Although Figure 1B While the processor 118 and transceiver 120 are depicted as separate components, it will be understood that the processor 118 and transceiver 120 can be integrated together in an electronic package or chip.

[0054] Transmitting / receiving element 122 can be configured to transmit signals to or receive signals from a base station (e.g., base station 114a) via air interface 116. For example, in one embodiment, transmitting / receiving element 122 can be an antenna configured to transmit and / or receive RF signals. In one embodiment, transmitting / receiving element 122 can be a transmitter / detector configured to transmit and / or receive, for example, IR, UV, or visible light signals. In yet another embodiment, transmitting / receiving element 122 can be configured to transmit and / or receive both RF signals and optical signals. It will be understood that transmitting / receiving element 122 can be configured to transmit and / or receive any combination of wireless signals.

[0055] Although the transmitting / receiving element 122 is in Figure 1B While depicted as a single element, WTRU 102 may include any number of transmit / receive elements 122. More specifically, WTRU 102 may employ MIMO technology. Thus, in one embodiment, WTRU 102 may include two or more transmit / receive elements 122 (e.g., multiple antennas) for transmitting and receiving wireless signals via air interface 116.

[0056] Transceiver 120 can be configured to modulate signals transmitted by transmitting / receiving element 122 and demodulate signals received by transmitting / receiving element 122. As described above, WTRU 102 can have multi-mode capability. Therefore, transceiver 120 can include multiple transceivers for enabling WTRU 102 to communicate via various RATs (e.g., such as NR and IEEE 802.11).

[0057] The processor 118 of WTRU 102 can be coupled to and receive user input data from: a speaker / microphone 124, a keypad 126, and / or a display / touchpad 128 (e.g., a liquid crystal display (LCD) unit or an organic light-emitting diode (OLED) display unit). The processor 118 can also output user data to the speaker / microphone 124, keypad 126, and / or display / touchpad 128. Additionally, the processor 118 can access information and store data from any suitable type of memory, such as non-removable memory 130 and / or removable memory 132. Non-removable memory 130 may include random access memory (RAM), read-only memory (ROM), a hard disk, or any other type of memory storage device. Removable memory 132 may include a subscriber identity module (SIM) card, memory stick, secure digital storage (SD) card, etc. In other embodiments, the processor 118 can access information and store data from memory not physically located on WTRU 102 (such as on a server or home computer (not shown)).

[0058] The processor 118 may receive power from the power supply 134 and may be configured to distribute power to other components in the WTRU 102 and / or control power to those other components. The power supply 134 may be any suitable device for powering the WTRU 102. For example, the power supply 134 may include one or more dry cell batteries (e.g., nickel-cadmium (NiCd), nickel-zinc (NiZn), nickel metal hydride (NiMH), lithium-ion (Li-ion), etc.), solar cells, fuel cells, etc.

[0059] The processor 118 may also be coupled to a GPS chipset 136, which may be configured to provide location information (e.g., longitude and latitude) about the current location of the WTRU 102. In addition to or instead of information from the GPS chipset 136, the WTRU 102 may receive location information from base stations (e.g., base stations 114a, 114b) via air interface 116 and / or determine its location based on the timing of signals received from two or more nearby base stations. It will be understood that, while remaining consistent with the embodiments, the WTRU 102 may acquire location information using any suitable location determination method.

[0060] The processor 118 may also be coupled to other peripheral devices 138, which may include one or more software and / or hardware modules that provide additional features, functions, and / or wired or wireless connectivity. For example, peripheral device 138 may include an accelerometer, electronic compass, satellite transceiver, digital camera (for photos and / or video), Universal Serial Bus (USB) port, vibration device, television transceiver, hands-free headset, Bluetooth® module, FM radio unit, digital music player, media player, video game player module, internet browser, virtual reality and / or augmented reality (VR / AR) device, activity tracker, etc. Peripheral device 138 may include one or more sensors, which may be one or more of the following: gyroscope, accelerometer, Hall effect sensor, magnetometer, orientation sensor, proximity sensor, temperature sensor, time sensor; geolocation sensor; altimeter, light sensor, touch sensor, magnetometer, barometer, gesture sensor, biometric sensor, and / or humidity sensor.

[0061] WTRU 102 may include a full-duplex radio, wherein the transmission and reception of some or all of the signals (e.g., associated with a specific subframe of UL (e.g., for transmission) and downlink (e.g., for reception)) may be concurrent and / or simultaneous. The full-duplex air interface may include an interference management unit 139 to reduce and / or substantially eliminate self-interference via hardware (e.g., a choke) or via a processor (e.g., a separate processor (not shown) or via processor 118) for signal processing. In embodiments, WTRU 102 may include a half-duplex radio, wherein the transmission and reception of some or all of the signals (e.g., associated with a specific subframe of UL (e.g., for transmission) or downlink (e.g., for reception)) may be separate.

[0062] Figure 1C This is a system diagram illustrating RAN 104 and CN 106 according to an embodiment. As described above, RAN 104 can employ E-UTRA radio technology to communicate with WTRUs 102a, 102b, and 102c via air interface 116. RAN 104 can also communicate with CN 106.

[0063] RAN 104 may include eNode-Bs 160a, 160b, and 160c, but it will be understood that RAN 104 may include any number of eNode-Bs while remaining consistent with the embodiments. eNode-Bs 160a, 160b, and 160c may each include one or more transceivers for communicating with WTRUs 102a, 102b, and 102c via air interface 116. In one embodiment, eNode-Bs 160a, 160b, and 160c may implement MIMO technology. Therefore, for example, eNode-B 160a may use multiple antennas to transmit radio signals to and / or receive radio signals from WTRU 102a.

[0064] Each of the eNode-B 160a, 160b, and 160c can be associated with a specific cell (not shown) and can be configured to handle radio resource management decisions, handover decisions, user scheduling in UL and / or DL, etc. Figure 1C As shown, eNode-B 160a, 160b, and 160c can communicate with each other via the X2 interface.

[0065] Figure 1C The CN 106 shown may include a Mobility Management Entity (MME) 162, a Serving Gateway (SGW) 164, and a Packet Data Network (PDN) Gateway (or PGW) 166. While each of the foregoing elements is described as part of CN 106, it will be understood that any of these elements may be owned and / or operated by an entity other than a CN operator.

[0066] The MME 162 can connect to each of the eNode-Bs 162a, 162b, and 162c in RAN 104 via the S1 interface and can act as a control node. For example, the MME 162 can be responsible for authenticating users of WTRUs 102a, 102b, and 102c, activating / deactivating bearers, selecting a specific serving gateway during the initial attachment of WTRUs 102a, 102b, and 102c, etc. The MME 162 can provide control plane functions for handover between RAN 104 and other RANs (not shown) employing other radio technologies such as GSM and / or WCDMA.

[0067] The SGW 164 can connect to each of the eNode Bs 160a, 160b, and 160c in RAN 104 via the S1 interface. The SGW 164 can typically route and forward user data packets to or from WTRUs 102a, 102b, and 102c. The SGW 164 can perform other functions such as anchoring the user plane during eNode-B handover, triggering paging when DL data is available to WTRUs 102a, 102b, and 102c, and managing and storing the context of WTRUs 102a, 102b, and 102c.

[0068] SGW 164 can be connected to PGW 166, which can provide WTRU 102a, 102b, 102c with access to packet-switched networks (such as Internet 110) to facilitate communication between WTRU 102a, 102b, 102c and IP-enabled devices.

[0069] CN 106 can facilitate communication with other networks. For example, CN 106 can provide WTRUs 102a, 102b, and 102c with access to circuit-switched networks (such as PSTN 108) to facilitate communication between WTRUs 102a, 102b, and 102c and conventional terrestrial line communication devices. For example, CN 106 may include an IP gateway (e.g., an IP Multimedia Subsystem (IMS) server) or be able to communicate with it, serving as an interface between CN 106 and PSTN 108. Additionally, CN 106 can provide WTRUs 102a, 102b, and 102c with access to other networks 112, which may include other wired and / or wireless networks owned and / or operated by other service providers.

[0070] Despite WTRU in Figures 1A to 1D While described as a wireless terminal, it is envisioned that, in some representative embodiments, such a terminal may (e.g., temporarily or permanently) use a wired communication interface with a communication network.

[0071] In a representative embodiment, the other network 112 may be a WLAN.

[0072] A WLAN in Infrastructure Basic Services Set (BSS) mode may have an access point (AP) for the BSS and one or more stations (STAs) associated with the AP. The AP may have access or an interface to a distribution system (DS) or another type of wired / wireless network that carries traffic entering and / or leaving the BSS. Traffic originating outside the BSS destined for a STA can be delivered to the AP. Traffic from a STA to a destination outside the BSS can be sent to the AP for delivery to the appropriate destination. Traffic between STAs within the BSS can be sent via the AP, for example, where a source STA can send traffic to the AP, and the AP can deliver the traffic to the destination STA. Traffic between STAs within the BSS can be considered and / or referred to as point-to-point traffic. Point-to-point traffic can be sent between a source STA and a destination STA using a direct link setup (DLS) (e.g., directly between them). In some representative embodiments, the DLS may use 802.11e DLS or 802.11z Tunneled DLS (TDLS). A WLAN using the Standalone BSS (IBSS) mode may not have an access point (AP), and STAs within the IBSS or using the IBSS (e.g., all STAs) can communicate directly with each other. The IBSS communication mode may sometimes be referred to as an "ad-hoc" communication mode in this document.

[0073] When operating in 802.11ac infrastructure mode or a similar mode, the AP can transmit beacons on a fixed channel, such as the primary channel. The primary channel can be of fixed width (e.g., a bandwidth of 20 MHz) or dynamically set via signaling. The primary channel can be the operating channel of the BSS and can be used by the STA to establish a connection with the AP. In some representative embodiments, Carrier Sense Multiple Access with Collision Avoidance (CSMA / CA) can be implemented, for example, in an 802.11 system. For CSMA / CA, each STA, including the AP, can sense the primary channel. If a particular STA senses / detects that the primary signal is busy and / or determines that the primary signal is busy, that particular STA can back off. In a given BSS, at any given time, only one STA (e.g., only one station) can transmit.

[0074] High-throughput (HT) STAs can communicate using a 40 MHz wide channel, for example, by combining a primary 20 MHz channel with adjacent or non-adjacent 20 MHz channels.

[0075] Very High Throughput (VHT) STAs can support channels with widths of 20 MHz, 40 MHz, 80 MHz, and / or 160 MHz. 40 MHz and / or 80 MHz channels can be formed by combining consecutive 20 MHz channels. A 160 MHz channel can be formed by combining eight consecutive 20 MHz channels, or by combining two non-consecutive 80 MHz channels, which can be referred to as an 80+80 configuration. In the 80+80 configuration, data, after channel coding, can be passed through a fragment parser that splits the data into two streams. Inverse Fast Fourier Transform (IFFT) processing and time-domain processing can be performed on each stream separately. The streams can be mapped onto the two 80 MHz channels, and the data can be transmitted by the transmitting STA. At the receiver of the receiving STA, the above operations for the 80+80 configuration can be reversed, and the combined data can be sent to the Media Access Control (MAC).

[0076] 802.11af and 802.11ah support operating modes below 1 GHz. The channel operating bandwidth and carrier are reduced in 802.11af and 802.11ah compared to those used in 802.11n and 802.11ac. 802.11af supports 5 MHz, 10 MHz, and 20 MHz bandwidths in the TV Blank (TVWS) spectrum, and 802.11ah supports 1 MHz, 2 MHz, 4 MHz, 8 MHz, and 16 MHz bandwidths using non-TVWS spectrum. According to a representative embodiment, 802.11ah may support instrument-type control / machine-type communication (MTC), such as MTC devices in macro coverage areas. MTC devices may have certain capabilities, such as limited capabilities, including support (e.g., only support) certain and / or limited bandwidths. MTC devices may include batteries with a battery life exceeding a threshold (e.g., to maintain a very long battery life).

[0077] WLAN systems that can support multiple channels and channel bandwidths (such as 802.11n, 802.11ac, 802.11af, and 802.11ah) include a channel that can be designated as the primary channel. The primary channel can have a bandwidth equal to the maximum common operating bandwidth supported by all STAs in the BSS. The bandwidth of the primary channel can be set and / or limited by the STAs operating in the BSS that support the minimum bandwidth operating mode. In the 802.11ah example, for STAs that support (e.g., only support) the 1 MHz mode (e.g., MTC type devices), the primary channel can be 1 MHz wide, even if the AP and other STAs in the BSS support 2 MHz, 4 MHz, 8 MHz, 16 MHz, and / or other channel bandwidth operating modes. Carrier Sense and / or Network Assignment Vector (NAV) settings can depend on the status of the primary channel. If the primary channel is busy, for example, because an STA (which only supports the 1 MHz operating mode) is transmitting to the AP, the entire available band may be considered busy even if most of the band remains idle and potentially available.

[0078] In the United States, the available frequency band for 802.11ah is 902 MHz to 928 MHz. In South Korea, the available frequency band is 917.5 MHz to 923.5 MHz. In Japan, the available frequency band is 916.5 MHz to 927.5 MHz. The total available bandwidth for 802.11ah is 6 MHz to 26 MHz, depending on the country code.

[0079] Figure 1D This is a system diagram illustrating RAN 113 and CN 115 according to one embodiment. As described above, RAN 113 may employ NR radio technology to communicate with WTRUs 102a, 102b, and 102c via air interface 116. RAN 113 may also communicate with CN 115.

[0080] RAN 113 may include gNBs 180a, 180b, and 180c, but it will be understood that RAN 113 may include any number of gNBs while remaining consistent with the embodiments. gNBs 180a, 180b, and 180c may each include one or more transceivers for communicating with WTRUs 102a, 102b, and 102c via air interface 116. In one embodiment, gNBs 180a, 180b, and 180c may implement MIMO technology. For example, gNBs 180a and 180b may utilize beamforming to transmit signals to and / or receive signals from gNBs 180a, 180b, and 180c. Thus, for example, gNB 180a may use multiple antennas to transmit radio signals to and / or receive radio signals from WTRU 102a. In one embodiment, gNBs 180a, 180b, and 180c may implement carrier aggregation technology. For example, gNB 180a can transmit multiple component carriers to WTRU 102a (not shown). A subset of these component carriers may be located on unlicensed spectrum, while the remaining component carriers may be located on licensed spectrum. In one embodiment, gNBs 180a, 180b, and 180c can implement Coordinated Multipoint (CoMP) technology. For example, WTRU 102a can receive coordinated transmissions from gNBs 180a and 180b (and / or gNB 180c).

[0081] WTRUs 102a, 102b, and 102c can communicate with gNBs 180a, 180b, and 180c using transmissions associated with scalable parameter sets. For example, the OFDM symbol spacing and / or OFDM subcarrier spacing can be varied for different transmissions, different cells, and / or different portions of the radio transmission spectrum. WTRUs 102a, 102b, and 102c can communicate with gNBs 180a, 180b, and 180c using subframes of various or scalable lengths or transmission time intervals (TTIs) (e.g., containing different numbers of OFDM symbols and / or absolute times of varying durations).

[0082] gNBs 180a, 180b, and 180c can be configured to communicate with WTRUs 102a, 102b, and 102c in standalone and / or non-standalone configurations. In standalone configuration, WTRUs 102a, 102b, and 102c can communicate with gNBs 180a, 180b, and 180c without accessing other RANs (e.g., eNodeBs 160a, 160b, and 160c). In standalone configuration, WTRUs 102a, 102b, and 102c can use one or more of gNBs 180a, 180b, and 180c as mobile anchors. In standalone configuration, WTRUs 102a, 102b, and 102c can communicate with gNBs 180a, 180b, and 180c using signals in unlicensed frequency bands. In a non-standalone configuration, WTRUs 102a, 102b, and 102c can communicate / connect with gNBs 180a, 180b, and 180c while also communicating / connecting with another RAN (such as eNode-Bs 160a, 160b, and 160c). For example, WTRUs 102a, 102b, and 102c can implement DC principles to communicate substantially simultaneously with one or more gNBs 180a, 180b, and 180c and one or more eNode-Bs 160a, 160b, and 160c. In a non-standalone configuration, eNode-Bs 160a, 160b, and 160c can act as mobile anchors for WTRUs 102a, 102b, and 102c, and gNBs 180a, 180b, and 180c can provide additional coverage and / or throughput to serve WTRUs 102a, 102b, and 102c.

[0083] Each of gNBs 180a, 180b, and 180c can be associated with a specific cell (not shown) and can be configured to handle air interface resource management decisions, handover decisions, user scheduling in uplink (UL) and / or downlink (DL), support for network slicing, dual connectivity, interoperability between NR and E-UTRA, routing of user plane data to User Plane Functions (UPF) 184a and 184b, routing of control plane information to Access and Mobility Management Functions (AMF) 182a and 182b, etc. Figure 1D As shown, gNB 180a, 180b, and 180c can communicate with each other via the Xn interface.

[0084] Figure 1DThe CN 115 shown may include at least one AMF 182a, 182b, at least one UPF 184a, 184b, at least two Session Management Functions (SMFs) 183a, 183b, and possibly Data Networks (DNs) 185a, 185b. While each of the foregoing elements is described as part of the CN 115, it will be understood that any of these elements may be owned and / or operated by an entity other than a CN operator.

[0085] AMF 182a and 182b can connect to one or more of the gNBs 180a, 180b, and 180c in RAN 113 via the N2 interface and can act as control nodes. For example, AMF 182a and 182b can be responsible for authenticating users of WTRU 102a, 102b, and 102c, supporting network slicing (e.g., handling different PDU sessions with different requirements), selecting specific SMFs 183a and 183b, managing registration areas, terminating NAS signaling, mobility management, etc. AMF 182a and 182b can use network slicing to customize CN support for WTRU 102a, 102b, and 102c based on the service types being used by WTRU 102a, 102b, and 102c. For example, different network slices can be established for different use cases, such as services relying on Ultra Reliable Low Latency (URLLC) access, services relying on Enhanced Massive Mobile Broadband (eMBB) access, and services for Machine Type Communication (MTC) access. AMF 162 can provide control plane functions for switching between RAN 113 and other RANs (not shown) that employ other radio technologies (such as LTE, LTE-A, LTE-A Pro) and / or non-3GPP (3rd Generation Partnership Project) access technologies (such as WiFi).

[0086] SMFs 183a and 183b can connect to AMFs 182a and 182b in CN 115 via the N11 interface. SMFs 183a and 183b can also connect to UPFs 184a and 184b in CN 115 via the N4 interface. SMFs 183a and 183b can select and control UPFs 184a and 184b, and configure traffic routing through UPFs 184a and 184b. SMFs 183a and 183b can perform other functions, such as managing and allocating UE IP addresses, managing PDU sessions, controlling policy enforcement and QoS, and providing downlink data notifications. PDU session types can be IP-based, non-IP-based, or Ethernet-based.

[0087] UPF 184a and 184b can be connected via the N3 interface to one or more of the gNBs 180a, 180b, and 180c in RAN 113. These gNBs can provide WTRU 102a, 102b, and 102c with access to packet-switched networks (such as the Internet 110) to facilitate communication between WTRU 102a, 102b, and 102c and IP-enabled devices. UPF 184 and 184b can perform other functions such as routing and forwarding packets, enforcing user plane policies, supporting multihomed PDU sessions, handling user plane QoS, buffering downlink packets, and providing mobility anchoring.

[0088] CN 115 can facilitate communication with other networks. For example, CN 115 may include or be able to communicate with an IP gateway (e.g., an IP Multimedia Subsystem (IMS) server) that serves as an interface between CN 115 and PSTN 108. Additionally, CN 115 can provide WTRUs 102a, 102b, and 102c with access to other networks 112, which may include other wired and / or wireless networks owned and / or operated by other service providers. In one embodiment, WTRUs 102a, 102b, and 102c can be connected to DN 185a and 185b via UPF 184a and 184b through the N3 interface to UPF 184a and 184b and the N6 interface between UPF 184a and 184b and local data networks (DNs) 185a and 185b.

[0089] Given Figures 1A to 1D and Figures 1A to 1D The corresponding descriptions can be performed by one or more emulation devices (not shown) that perform one or more of the functions described herein with respect to: WTRU 102a to 102d, base stations 114a to 114b, eNode-B 160a to 160c, MME 162, SGW 164, PGW 166, gNB 180a to 180c, AMF 182a to 182b, UPF 184a to 184b, SMF 183a to 183b, DN 185a to 185b, and / or any other devices described herein. An emulation device can be one or more devices configured to emulate one or more or all of the functions described herein. For example, an emulation device can be used to test other devices and / or simulate network and / or WTRU functions.

[0090] Simulation devices can be designed to perform one or more tests on other devices in laboratory and / or carrier network environments. For example, one or more simulation devices may perform one or more functions when fully or partially implemented and / or deployed as part of a wired and / or wireless communication network to test other devices within the communication network. One or more simulation devices may perform one or more functions when temporarily implemented / deployed as part of a wired and / or wireless communication network. Simulation devices may be directly coupled to another device for testing purposes and / or may use over-the-air wireless communication to perform tests.

[0091] One or more simulation devices can perform one or more functions without being implemented / deployed as part of a wired and / or wireless communication network. For example, a simulation device can be used to test scenarios in a laboratory and / or undeployed (e.g., under test) wired and / or wireless communication networks to enable testing of one or more components. One or more simulation devices can be test equipment. The simulation device can transmit and / or receive data using direct RF coupling and / or wireless communication via an RF circuit system (e.g., which may include one or more antennas).

[0092] This article describes methods and devices for handling MAC address conflicts in U2U (also known as UE-to-UE or WTRU-to-WTRU) communication. U2U communication can be established via a PC5 link. Figure 2 This is a diagram depicting an exemplary 5G ProSe communication via UE-to-UE relay at 5G ProSe layer 3. More specifically, Figure 2 This describes an exemplary PC5 unicast link establishment process between a source UE and a destination UE via a Layer 3 UE-to-UE relay. If the PC5 link is used to transmit traffic (e.g., Ethernet traffic), then... Figure 2As described in step 4, the source WTRU (202) can send its MAC address to the WTRU-WTRU relay (204) after security protection is enabled, for example, using a Direct Security Model (DSM) completion message. If the MAC address is being used by another end WTRU, the WTRU-WTRU relay (204) can send a message to the source WTRU (202) indicating a MAC address conflict. After the security establishment process between the source WTRU (202) and the WTRU-WTRU relay (204) is completed (step 4), the WTRU-WTRU relay (204) can send a Direct Communication Request message to initiate a unicast layer 2 link establishment process (step 5). The destination WTRU (206) can respond by establishing security with the WTRU-WTRU relay (step 6). After security protection is enabled, the WTRU-WTRU relay (204) can send the MAC address of the source WTRU (202) to the destination WTRU (206), for example, using a DSM completion message, as described in step 6. The target WTRU (206) can send a Direct Communication Acceptance (DCA) message (step 7) to the WTRU-WTRU relay (204) with which it has successfully established security. The target WTRU (206) can include its MAC address in the DCA message of step 7. After receiving the Direct Communication Acceptance message from the target WTRU (206), the WTRU-WTRU relay (204) can send a Direct Communication Acceptance message (step 9) to the source WTRU (202) with which it has successfully established security. The relay (204) can include the MAC address of the target WTRU in the DCA message of step 9. For Ethernet communication, the WTRU-WTRU relay (204) can maintain the association between the PC5 link and the Ethernet MAC addresses received from the source WTRU and the target WTRU.

[0093] With more and more mobile devices connecting to the internet directly (e.g., via cellular networks or Wi-Fi) or indirectly (e.g., via smartphones using Bluetooth), internet privacy issues are receiving increasing attention. One aspect to consider in location tracking is the widespread use of long-term valid identifiers (such as MAC addresses). A MAC address can contain a 48-bit value, consisting of a 24-bit Organization Unique Identifier (OUI) portion and a 24-bit Network Interface Controller (NIC) portion. Privacy issues can be addressed using MAC randomization. MAC addressing can include a bit to specify whether the hardware address is locally managed or globally managed. This allows for the generation of local addresses without a global coordination mechanism, ensuring that the generated address remains unique within the local network. This feature can be used to generate random addresses, thereby decoupling the globally unique identifier from the device and thus making it more difficult to track the user device via the device's MAC / L2 (Layer 2) address.

[0094] Even if the MAC address of the source WTRU is not unique, a PC5 link can be established between the source and destination WTRUs via a WTRU-to-WTRU relay. The WTRU-to-WTRU relay can send a message to the source WTRU indicating a MAC address conflict. The message sent to the source WTRU does not need to be mandatory, and the behavior of the source WTRU may be undefined. Furthermore, the establishment of a PC5 link can be allowed even when a MAC address conflict is detected. When receiving traffic with a destination MAC address that is not unique (e.g., Ethernet traffic), the relay may not be able to determine which PC5 link to forward the traffic to; the relay may decide to forward the traffic to the wrong source WTRU; the relay may discard the traffic with the non-unique MAC address; or it may take any appropriate combination of the above. Furthermore, the existing process does not consider a second PC5 hop between the relay and the destination WTRU, where the security process can be triggered by the destination WTRU.

[0095] In the case of WTRU-to-network relay, MAC address conflict avoidance between remote WTRUs can be supported to at least ensure that the relay reports a unique MAC address for each remote WTRU for each connection to the Network Session Management Function (SMF), as the MAC address can be used to uniquely identify a remote WTRU outside the 5G core network (5GC). Furthermore, WTRU-to-network relay can use independent Internet Protocol (IP) tunnels on user-to-user (Uu) links to transmit traffic to and from each remote WTRU. If the WTRU-to-network relay internally uses the MAC address of the destination remote WTRU to determine which PC5 link to route downlink traffic, then ensuring the uniqueness of the remote WTRU's MAC address locally (as in the case of WTRU-to-WTRU relay) can be advantageous. Therefore, this paper describes devices and methods that address how a relay can ensure the uniqueness of the MAC address of the source WTRU and how a relay can ensure the uniqueness of the MAC address of the destination WTRU.

[0096] Furthermore, in scenarios where a WTRU connects to other WTRUs via multiple ProSe links, MAC address conflicts across ProSe links can occur. For example, a source WTRU can connect to a target WTRU A via ProSe link A, and the same source WTRU can connect to a second target WTRU via a second ProSe link B. If target WTRU A and target WTRU B share the same MAC address, the source WTRU may not know which ProSe link to choose when sending data. This situation also applies when a source (or target) WTRU communicates with multiple target (or source) WTRUs via multiple WTRU-to-WTRU relays. For example, if a source WTRU communicates with target WTRU1 via relay 1 and with target WTRU2 via relay 2, and if both target WTRUs use the same MAC address, the relays may not detect the MAC address conflict and therefore may not be able to process it. Therefore, MAC address conflict resolution can occur at the end WTRU. Furthermore, this document describes devices and methods for resolving how an end WTRU can ensure the uniqueness of its MAC address with its peer end WTRU.

[0097] As described herein, the following terms are used interchangeably: relay, UE-to-UE relay, UE-to-UE relay 5G Prose layer 3, WTRU-to-WTRU relay, and WTRU-to-WTRU relay 5G Prose layer 3. Furthermore, the terms UE, 5G Prose end UE, WTRU, and 5GProSe WTRU are used interchangeably.

[0098] The example described in this article is based on the end WTRU having the ability to change its MAC address. The MAC address of the end WTRU can be managed by the end WTRU or by the trunk. For example, the end WTRU can generate a new MAC address, or a new MAC address can be assigned by the trunk via the PC5 interface when needed.

[0099] Furthermore, in scenarios where the end WTRU checks / verifies the uniqueness of MAC addresses between its peer UEs, as described herein, the same procedure can be used by replacing the relay procedure with the corresponding end WTRU. As described herein, the MAC address of the end WTRU can be changed to address privacy concerns. The examples described herein for mitigating MAC address conflict detection and / or prevention at WTRU-to-WTRU relays can be applied to WTRU-to-network relays.

[0100] Exemplary detection of non-unique MAC addresses can be achieved, but is not limited to, comparing the new MAC address with other existing MAC addresses stored in a local database (e.g., an Address Resolution Protocol (ARP) table). Any suitable entity (e.g., a relay, WTRU, node, or any suitable combination thereof) can detect non-unique MAC addresses. A lookup request can be sent to a node in the network (e.g., a relay WTRU) carrying the MAC address to be verified. In response, the sender can receive an indication of whether the MAC address in the request is unique. Alternatively, the response can include all MAC addresses known to the node, which can then be used for comparison with the MAC address to be verified. Some relays can store the MAC addresses of all other WTRUs and provide MAC address lookup services to other WTRUs. ARP can be used to discover MAC addresses. Other WTRUs can be requested (e.g., via broadcast messages) to check if they hold the MAC address to be verified in order to obtain their MAC addresses for comparison.

[0101] Exemplary allocation of non-unique MAC addresses can be achieved, but is not limited to, by maintaining a list of previously allocated MAC addresses and the nodes to which they were assigned, and assigning the same MAC address to the same node. MAC addresses can be generated randomly, and any of the above processes can be used to check whether the generated addresses are unique. The allocation of non-unique MAC addresses can be performed by any suitable entity or device (e.g., a relay).

[0102] Figure 3An exemplary process is described in which a relay detects a MAC address conflict between the source WTRU and another MAC address. At step 1, the relay WTRU (304) can receive a Direct Communication Request (DCR) message from the source WTRU (302), wherein the DCR message may contain an indication of a request for the source WTRU (302) to establish a link with the target WTRU (306). This link can be configured to relay traffic between the source WTRU (302) and the target WTRU (306). The relay (304) can detect a MAC address conflict between the source WTRU (302) and another MAC address. The source WTRU (302) can send a Direct Communication Request (DCR) message to the WTRU-to-WTRU relay (304), thereby initiating the link establishment process (step 1). The relay WTRU (304) can send a DSM command message to the source WTRU (302). A WTRU-to-WTRU relay (304) can send a DSM command message to the source WTRU (302) to establish security (step 2). The relay WTRU (304) can receive a response message from the source WTRU (302) (step 3). The response message may contain an indication of the MAC address associated with the source WTRU (302). The response message may contain a DSM completion message. A WTRU can be associated with another WTRU in any suitable manner. For example, a WTRU may have the MAC address of another WTRU in memory, thereby enabling these WTRUs to be associated. A WTRU does not necessarily have to be connected to another WTRU to be associated with other WTRUs. The source WTRU (302) can send a DSM completion message containing the MAC address of its source WTRU (step 3). The relay (304) can detect a MAC address conflict associated with the MAC address of the source WTRU (302). A MAC address conflict can be associated with the MAC address of a source WTRU (302) that is being used by another WTRU associated with a relay WTRU (304). The relay (304) can detect that the MAC address received from the source WTRU (302) is not unique, for example, if there is a conflict with the MAC address of another end WTRU (step 4). The detection can be performed as described above.

[0103] Depicted as Alternative A, after step 4, the relay (304) may send a PC5 signaling protocol stack (PC5-S) request message to the source WTRU (302) to request a new MAC address (Alternative A, step 5a). This could be a new message, such as "Request for New Address" specifying the "MAC Address Type," or a modified existing message, such as "DSM Command" or "Link Modification Request" specifying "New MAC Address Required." The source WTRU (302) may respond with a PC5-S response message containing the new MAC address of the source WTRU (Alternative A, step 6a). This could be a new message, such as "Request for New Address Response," or a modified existing message, such as "DSM Complete" or "Link Modification Response." The relay (304) may check whether the MAC address received from the source WTRU (302) is unique (step 7a). This can be performed as described above. The relay (304) can establish a PC5 link with the target WTRU (306) (step 8a). The relay (304) can send a DCA message to the source WTRU (302) indicating that the DCR has been accepted (alternative solution A, step 9a).

[0104] Described as Alternative Option B, after step 4, the relay (304) can assign a new MAC address to the source WTRU (302) (Alternative Option B, step 5b). This can be performed based on the above. The relay (304) can establish a PC5 link with the target WTRU (306) (Alternative Option B, step 6b). The relay (304) can send a DCA message to the source WTRU (302) containing the newly assigned MAC address of the source WTRU (Alternative Option B, step 7b).

[0105] Described as Alternative Solution C, after step 4, if the relay (304) detects that the MAC address of the source WTRU (302) is not unique, the relay (304) can send a Direct Communication (DC) Reject message to the source WTRU (302) containing an indication that the MAC address is not unique (e.g., reason = MAC address is not unique) (Alternative Solution C, step 5c). The source WTRU (302) can generate a new MAC address and restart the PC5 link establishment process with the relay (step 1).

[0106] After sending the DC rejection message, the relay WTRU (304) can receive a second DCR message from the source WTRU (302) (similar to step 1), wherein the second DCR message may contain an indication of a second request for the source WTRU (302) to establish a link with the target WTRU (306). Based on the second DCR message, the process can continue as depicted in steps 2, 3, and 4. The relay WTRU (304) may send a second DSM command message (similar to step 2), and the relay WTRU (304) may receive a second response message, wherein the second response message may contain an indication of the second Media Access Control (MAC) address of the second WTRU.

[0107] Figure 4 This is an exemplary description of a relay selecting the MAC address of the source WTRU. The source WTRU can provide a list of MAC addresses. The source WTRU (402) can initiate the link establishment process (step 1) by sending a Direct Communication Request message to the WTRU-WTRU relay (404). The WTRU-WTRU relay (404) can send a DSM Command message to the source WTRU (402) to establish security with the source WTRU (402) (step 2). The source WTRU (402) can send a DSM Complete message to the WTRU-WTRU relay (404), wherein the DSM Complete message may contain the MAC address of the source WTRU or one or more MAC addresses that the source WTRU (402) can use for the link between the source WTRU (402) and the relay (404) (step 3). For example, this can be specified as a list or a range. The relay (402) can select a unique MAC address from the list received from the source WTRU (402) (step 4). This can be performed based on the process described above. The relay (404) can establish a PC5 link with the target WTRU (406) (step 5). The relay (404) can send a DC accept message to the source WTRU (402), which contains the selected MAC address to be used by the source WTRU (402) (step 6).

[0108] Figure 5This is an exemplary description of a relay detecting a MAC address conflict between the target WTRU and another MAC address. At step 1, the relay (504) can receive a Direct Communication Request (DCR) message from the source WTRU (502), where the DCR message may contain an indication of a request for the source WTRU (502) to establish a link with the target WTRU (506). This link can be configured to relay traffic between the source WTRU (502) and the target WTRU (506). The source WTRU (502) can send a Direct Communication Request message to the WTRU-to-WTRU relay (504), thereby initiating the link establishment process (step 1). The relay WTRU (504) can establish a secure link with the source WTRU (502) (step 2). The WTRU-to-WTRU relay (504) and the source WTRU (502) can establish a secure PC5 link (step 2). The relay (504) can send a direct communication request to the target WTRU (506) for traffic (step 3). The relay (504) can send a DCR message to the target WTRU (506), wherein the DCR message may contain an indication of a request for the target WTRU (506) to establish communication (e.g., a link) with the source WTRU (502) (step 3). The relay WTRU (504) can establish a secure link with the target WTRU (506) (step 4). The relay (504) and the target WTRU (506) can establish a secure PC5 link (step 4). The relay WTRU (504) can receive a response message from the target WTRU (506) (step 5). The response message may contain an indication of the MAC address associated with the target WTRU (506). The response message may contain a DCA message. The WTRU may be associated with another WTRU in any appropriate manner. For example, a WTRU can have the MAC address of another WTRU in its memory, thus enabling association between these WTRUs. A WTRU does not necessarily need to be connected to another WTRU to be associated with other WTRUs. The relay (504) can receive Direct Communication Acceptance (DCA) messages from the relay (506), where the DCA message may contain the MAC address of the target WTRU (step 5). The relay (504) can detect MAC address conflicts associated with the MAC address of the target WTRU (step 6). The relay (504) can detect that the MAC address received from the target WTRU (506) is not unique, for example, there is a conflict with the MAC address of another WTRU (step 6). This can be performed based on the process described above.

[0109] Described as Alternative Solution A, after step 6, the relay (504) can block traffic from / to the PC5 link and can send a Link Modification (LM) request message to the target WTRU (506), for example, with operation code = "Get New MAC Address" and reason = "MAC Address Not Unique" (Alternative Solution A, step 7). The target WTRU (506) can send a Link Modification (LM) response to the relay (504), where the LM response can contain the new MAC address (Alternative Solution A, step 7).

[0110] Described as Alternative Option B, after step 6, the relay (504) may interpret the received non-unique MAC address as a trigger for a Link Identifier Update (LIU) procedure. The relay (504) may send a Link Identifier Update Request message to the target WTRU (506) (Alternative Option B, step 7). This message may contain suggested / alternative MAC addresses for the target WTRU (506) and may also contain the MAC address of the source WTRU received in step 2. The target WTRU (506) may send a LIU response to the relay (504), wherein the LIU response may contain the new MAC address of the target WTRU (Alternative Option B, step 8). The new MAC address may be selected from the list of suggested / alternative MAC addresses (if received at step 7). The relay (504) may send a LIU acknowledgment message to the target WTRU (506), wherein the LIU acknowledgment message may contain the new MAC address of the target WTRU received at step 8 (Alternative Option B, step 9).

[0111] Depicted as Alternative C, after step 6, the relay (504) may send a Link Release Request message to the target WTRU (506), for example, with the reason "MAC address not unique" (Alternative C, step 7). The relay (504) may send a Link Release (LR) Request message to the target WTRU (506) based on the detection of a MAC address conflict associated with the MAC address of the target WTRU (506). The LR Request message may contain one or more alternative MAC addresses for the target WTRU (506). The LR Request message may contain a reason code indicating an indication of a conflict associated with the MAC address of the target WTRU (506) (e.g., MAC address not unique). This LR message may contain suggested / alternative MAC addresses for the target WTRU (506). The target WTRU (506) may record the suggested MAC address from the relay (504), which will be used in subsequent PC5 link establishment processes. The target WTRU (506) can send a link release response message to the relay (504) (Alternative Solution C, Step 8). The relay (504) can send another direct communication request to the target WTRU (506) for traffic (Alternative Solution C, Step 9). The target WTRU (506) can verify whether any suggested MAC addresses have been previously received from the relay. The target WTRU (506) can select a MAC address from the list received at Step 7 in Alternative Solution C. The target WTRU (506) can continue with PC5 link establishment. After successful security establishment, the target WTRU (506) can send a DCA message to the relay (504), which may contain the selected MAC address (Alternative Solution C, Step 10).

[0112] Described as Alternative D, after step 6, the relay (504) may block traffic from / to the PC5 link and may send a link modification request message to the target WTRU (506) containing a new MAC address for the target WTRU (506) (Alternative D, step 7). Alternatively, a list of MAC addresses may be specified. The target WTRU (506) may send a link modification response to the relay (504), wherein the link modification response acknowledges receipt of the new MAC address assigned by the relay (504) (Alternative D, step 7).

[0113] Alternatively, the target WTRU (506) may select a new MAC address from a list received from the self-relay (504) and provide its selected MAC address along with the link modification response.

[0114] Figure 6An exemplary process is described that provides a list of MAC addresses for the target WTRU or relay. Figure 6 This is an exemplary description of a list of MAC addresses provided by the target WTRU or relay. The relay (604) can receive DCR messages from the source WTRU (602) for traffic and can establish security (step 1). WTRU-to-WTRU relay (604) and source WTRU (602) can establish security for the PC5 link (step 2). The relay (604) can send DCRs to the target WTRU (606) for traffic (step 3). The relay (604) can receive DSM command messages from the target WTRU (606) (step 4).

[0115] Depicted as Alternative A, after step 4, the target WTRU (606) can provide a list of MAC addresses. The relay (604) can send a DSM completion message containing the source WTRU's MAC address (Alternative A, step 5a). The target WTRU (606) can send a Direct Communication Acceptance (DCA) message to the relay (604), where the DCA message may contain one or more MAC addresses it can use (Alternative A, step 6a). The relay (604) can select a MAC address for the target WTRU (606) that does not conflict with MAC addresses used by other WTRUs. The relay (604) can send a PC5 Signaling Protocol Stack (PC5-S) message to the target WTRU (606), which contains the selected unique MAC address (Alternative A, step 7a). The PC5-S message can be a new message (e.g., setting a MAC address) or a modified existing message (e.g., a link modification request). The target WTRU (606) may send a PC5-S response message to the relay (604), the PC5-S response message confirming that the selected MAC address will be used by the target WTRU (alternative scheme A, step 8a). The target WTRU (606) may contain the received selected MAC address.

[0116] Described as Alternative Option B, after step 4, the relay (604) can provide a list of MAC addresses. The relay (604) can send a DSM Completion message to the target WTRU (606), wherein the DSM Completion message may contain the MAC address of the source WTRU and may also provide one or more MAC addresses that the target WTRU (606) can use to establish a link with the relay (Alternative Option B, step 5b). The target WTRU (606) can select a MAC address from the list received from the relay (604). The target WTRU (606) can select a MAC address that does not conflict with the MAC address used by its peer WTRU. The target WTRU (606) can send a Direct Communication Acceptance (DCA) message to the relay (604), wherein the DCA message may contain the selected MAC address of the target WTRU (Alternative Option B, step 6b).

[0117] Figure 7 This is an exemplary description of a relay detecting a MAC address conflict between the source WTRU and another MAC address. The source WTRU (702) can establish a PC5 link with relay 1 (704) to enable communication with the target WTRU1 (708) (Step 1). Relay 1 (704) can establish a PC5 link to the target WTRU1 (708) (Step 2). The source WTRU (702) can trigger the establishment of a PC5 link with relay 2 (706) to reach the target WTRU2 (710) by sending a DCR message for traffic (Step 3). Relay 2 (706) can send a DCR message to the target WTRU2 (710) (Step 4). The target WTRU2 (710) can send a DCA message containing its MAC address to relay 2 (706) (Step 5). Relay 2 (706) can send a DCA message containing the MAC address of the target WTRU (710) to the source WTRU (702) (Step 6). The source WTRU (702) can detect non-unique MAC addresses (e.g., MAC address conflict) (step 7). For example, the MAC address used by the destination WTRU2 (710) can be the same as the MAC address used by the destination WTRU1 (702). This can be performed based on the process described above.

[0118] Described as Alternative Solution A, after step 7, a new MAC address can be associated with the target WTRU (710). The source WTRU (702) can send a modified link modification request message to relay 2 (706), which includes an indication that the MAC address of the target WTRU (710) is not unique and an indication that relay 2 (706) will block traffic on this end-to-end PC5 link (Alternative Solution A, step 8a). Alternatively, the source WTRU (702) can provide one or more MAC addresses, which the target WTRU (710) can use as replacements for conflicting MAC addresses. Relay 2 (706) can block / not forward traffic on the PC5 link between the source WTRU (702) and the relay, directed towards the target WTRU2 (710) (and vice versa) (Alternative Solution A, step 9a). Relay 2 (706) can send a link modification request message, which includes an indication that the MAC address is not unique (Alternative Solution A, step 10a). Optionally, relay 2 (706) may provide one or more MAC addresses, which the target WTRU (710) uses as replacements for conflicting MAC addresses (as received at step 8a). The target WTRU2 (710) may provide a list of MAC addresses in an LM response message to request the source WTRU (702) to select a MAC address (Alternative Scheme A, step 11a). Alternatively, the target WTRU2 (710) may change its MAC address, for example, by generating a new MAC address. The target WTRU (710) may send a link modification response message to relay (706) containing its new MAC address. Relay (706) may associate this MAC address with the PC5 link. Optionally, the target WTRU (710) may select a MAC address from the list received from step 10 (if any). Relay 2 (706) may send an LM response message to the source WTRU (702) containing the parameters received at step 11a (Alternative Scheme A, step 12a). The source WTRU (702) can select a MAC address from the list received from the destination WTRU (710) and can send an LM acknowledgment message to relay 2 (706) containing an indication to unblock traffic forwarding and an indication of the selected MAC address (Alternative Solution A, step 13a). Optionally, if a new MAC address of the destination WTRU is received in step 12a, the source WTRU (702) can verify it. Relay 2 (706), having received the indication to unblock traffic, can begin processing traffic forwarding between the source WTRU (702) and the destination WTRU2 (710) (Alternative Solution A, step 14a).If the selected MAC address of the target WTRU (710) is provided in step 13a, then relay 2 (706) can send an LM acknowledgment message to the target WTRU2 (710) and associate the selected MAC address with the PC5 link corresponding to the target WTRU (710) (alternative scheme A, step 15a). The target WTRU2 (710) can receive the LM acknowledgment message containing the selected MAC address to be used by the target WTRU (710) and associate it with the PC5 link.

[0119] Described as Alternative Solution B, after step 7, the PC5 link can be released. The source WTRU (702) can send a link release request message to relay 2 (706), which includes an indication that the MAC address of the destination WTRU is not unique (Alternative Solution B, step 8b). Optionally, a list of MAC addresses can be included. Relay 2 (706) can send a link release request message to the destination WTRU2 (710), which includes the indication and a list of MAC addresses (if received) (Alternative Solution B, step 9b). The destination WTRU2 (710) can record the list of MAC addresses from the source WTRU (702), which will be used when establishing another PC5 link with the source WTRU (702). The destination WTRU2 (710) can send a link release response message to relay 2 (706) and can release the PC5 link (Alternative Solution B, step 10b). Relay 2 (706) can send a PC5 link response message to the source WTRU (702) and can release the PC5 link (alternative solution B, step 11b). The source WTRU (702) can re-trigger the establishment of a PC5 unicast link with the target WTRU (710) via relay (706). In this case, the target WTRU (710) can select a MAC address from the list saved in step 10.

[0120] Described as Alternative Solution C, after step 7, the local MAC address can be updated. The source WTRU (702) can send a modified link modification request message to relay 2 (706), which includes an indication that the target WTRU's MAC address is not unique, and optionally can provide one or more MAC addresses that the target WTRU (710) can use to replace the conflicting MAC address (Alternative Solution C, step 8c). Relay 2 (706) can decide to change the target WTRU's MAC address to a new MAC address in order to communicate locally with the source WTRU (702) (Alternative Solution C, step 9c). Relay 2 (706) can send an LM response message to the source WTRU (702), which includes the newly assigned MAC address (Alternative Solution C, step 10c). Whenever relay 2 (706) receives traffic from source WTRU (702) to destination WTRU (710) using the new MAC address allocated in step 9 as the destination MAC address, relay 2 (706) can change the new MAC address to the MAC address of the destination WTRU received in step 5 (alternative solution C, step 11c). When relay 2 (706) receives traffic from destination WTRU (710) to source WTRU (702) using the MAC address of the destination WTRU received in step 5 as the source MAC address, relay 2 (706) can change the MAC address of the destination WTRU to the new MAC address allocated in step 9 (alternative solution C, step 11c).

[0121] The target WTRU can be identified using its MAC address and the Layer 2 (L2) identifier (ID) of the relay WTRU. When the source WTRU detects that the target WTRU's MAC address is not unique (this can be based on the process described above), the source WTRU can use the L2 ID of the relay WTRU connected to both the source and target WTRUs, along with the target WTRU's MAC address, to identify the user information associated with the application. Upon receiving downlink (DL) traffic, the associated application can be identified using the source L2 ID / destination L2 ID and MAC address. When sending UL traffic for a user associated with the target WTRU, the source WTRU retrieves the associated L2 ID and MAC address to identify the relay WTRU, which uses the target END WTRU's MAC address to send the traffic.

[0122] Figure 8This is an exemplary description of a target WTRU detecting a MAC address conflict between the source WTRU and another MAC address. In step 1, the relay (804) can receive a Direct Communication Request (DCR) message from the source WTRU (802), wherein the DCR message may contain an indication of a request for the source WTRU (802) to establish a link with the target WTRU (506). This link may be configured to relay traffic bidirectionally between the source WTRU (802) and the target WTRU (806). The relay (804) can receive the DCR message from the source WTRU (802) for the traffic (step 1). The relay (804) can send a DSM Command message to the source WTRU (802) (step 2). The relay (804) can receive a DSM Completion message from the source WTRU (802), wherein the DSM Completion message may contain the MAC address associated with the source WTRU (802). The relay (804) can receive a DSM completion message from the source WTRU (802), which contains the MAC address of the source WTRU (step 3). The relay (804) can send a DCR message to the target WTRU (806) for traffic (step 4). The relay (804) can receive a DSM command message from the target WTRU (806) (step 5). The relay (806) can send a DSM completion message to the target WTRU (806), which may contain the MAC address associated with the source WTRU (802). The relay (804) can send a DSM completion message to the target WTRU (806), which contains the MAC address of the source WTRU (802) (step 6). The target WTRU (806) can detect that the MAC address is not unique (e.g., MAC address conflict) (step 7). This can be performed based on the above process.

[0123] Depicted as Alternative A, after step 7, the target WTRU (806) may send a list of MAC addresses for the source WTRU (802), and the relay (804) may update this list. At step 8a of Alternative A, the relay WTRU (804) may receive a Direct Communication Acceptance (DCA) message from the target WTRU (806), wherein the DCA message may contain an indication of a conflict associated with a MAC address of the source WTRU (802), and wherein the DCA message may contain a list of alternative MAC addresses for the source WTRU (802). The relay (804) may receive a DCA message containing, for example, an indication that "MAC address is not unique" and one or more MAC addresses for the source WTRU (802) (Alternative A, step 8a). In response to receiving a DCA message from the target WTRU (806), the relay (804) may block traffic between the source WTRU (802) and the target WTRU (806) (Alternative Solution A, step 9a). The relay (804) may block / not forward traffic on the PC5 link between the target WTRU (806) and the relay (804) that is directed towards the source WTRU (802) (or vice versa) (Alternative Solution A, step 9a). The relay (904) may update the list of received alternative MAC addresses for the source WTRU (802) (Alternative Solution A, step 10a). The relay (804) may update the list of MAC addresses received from the target WTRU (806) for the source WTRU (802). For example, the relay (802) may remove all MAC addresses that conflict with other registered WTRUs (e.g., MAC addresses already in use by other WTRUs) (Alternative Solution A, step 10a). The relay (804) may send a DCA message containing an update of the MAC address for the source WTRU (802) to the source WTRU (802) (Alternative A, step 11a). The relay WTRU (804) may receive a modified link message (LM) from the source WTRU (802), wherein the modified LM may contain an indication of the selected MAC address, wherein the selected MAC address is selected from an updated list of MAC addresses (Alternative A, step 12a). The source WTRU (802) may send a modified link modification request message containing the MAC address selected from the list received from the DCA message (Alternative A, step 12a). The relay (804) may send a link modification request message containing the selected MAC address of the source WTRU (Alternative A, step 13a). The destination WTRU (806) may associate the received MAC address of the source WTRU with the PC5 link and may send a link modification response message (Alternative A, step 14a).In response to receiving an LM response message, the relay WTRU (804) can unblock traffic between the source WTRU (802) and the destination WTRU (806). The relay (804) can unblock / allow forwarding of traffic on the PC5 link between the destination WTRU (806) and the relay (804) that is directed towards the source WTRU (802) (or vice versa) (Alternative Solution A, step 15a). The relay (804) can send an LM response message to the source WTRU (802) (Alternative Solution A, step 16a).

[0124] Described as Alternative Solution B, after step 7, the target WTRU (806) can refuse link establishment. The relay (804) can receive a DC Reject message from the target WTRU (806) indicating that the MAC address is not unique, for example, reason = MAC address not unique (Alternative Solution B, step 8b). The relay (804) can send a DC Reject message to the source WTRU (802) indicating that the MAC address is not unique, for example, reason = MAC address not unique (Alternative Solution B, step 9b).

[0125] Depicted as Alternative C, after step 7, the MAC address of the source WTRU (802) can be used only between the relay (804) and the target WTRU (806). The relay (804) can receive a DCA message containing an indication that the MAC address is not unique, such as "MAC address is not unique," and one or more MAC addresses for the source WTRU (802) (Alternative C, step 8c). The relay (804) can block / not forward traffic on the PC5 link between the target WTRU (806) and the relay (804) that is directed towards the source WTRU (802) (or vice versa) (Alternative C, step 9c). The relay (804) can decide to change the MAC address of the source WTRU to a new MAC address that will only be used between the relay (80) and the target WTRU (806) during communication (Alternative C, step 10c). The selected new MAC address can be chosen from a list of candidate MAC addresses received in step 8. The relay (804) can send a DCA message to the source WTRU (802) (Alternative C, step 11c). The relay (804) can send a link modification request message containing a new MAC address, which may have been locally assigned to the MAC address selected for the source WTRU in step 10 (Alternative C, step 12c). The destination WTRU (806) can associate the received MAC address of the source WTRU with the PC5 link and can send a link modification response message (Alternative C, step 13c). The relay (804) can unblock / allow forwarding traffic on the PC5 link between the destination WTRU (806) and the relay (804) towards the source WTRU (802) (and vice versa) (Alternative C, step 14c).

[0126] Whenever the relay (804) receives traffic from the destination WTRU (806) to the source WTRU (802) using the new MAC address allocated at step 10c of alternative scheme C as the destination MAC address, the relay (804) can change the new MAC address to the MAC address of the source WTRU received at step 3. Whenever the relay (804) receives traffic from the source WTRU (802) to the destination WTRU (806) using the MAC address of the source WTRU received at step 3 as the source MAC address, the relay (804) can change the MAC address of the source WTRU to the new MAC address allocated at step 10c of alternative scheme C.

[0127] Figure 9 An exemplary process for conflict-free MAC address negotiation is described. Figure 9An exemplary process is described for two WTRUs to negotiate conflict-free MAC address negotiation in order to exchange traffic. The initiating WTRU (902) may decide to connect to the target WTRU (904) using a MAC conflict avoidance negotiation protocol. The initiating WTRU (902) may send a DCR message to the target WTRU (904) for traffic (step 1). This message may contain MAC address allocation support information (e.g., a policy / scheme for MAC address allocation). The target WTRU (904) may send a Direct Security Model (DSM) command message to the initiating WTRU (902) (step 2). This message may contain the negotiated MAC address allocation scheme. The MAC address allocation scheme may specify when or how MAC addresses can be randomized (e.g., whether to retain the Organization Unique Identifier (OUI) portion of the MAC address or randomize all allowed bits, and whether to update the MAC address upon connection). The target WTRU (904) may provide a portion of its own MAC address in the DSM command message. The target WTRU (904) may omit MAC address allocation information elements (e.g., to allow backward compatibility with legacy WTRUs). If the MAC address allocation policy of the target WTRU (904) conflicts (e.g., MAC address randomization is not allowed), the target WTRU may refuse the connection. Based on the MAC address allocation scheme, the initiating WTRU (902) may allocate a first portion of its MAC address to itself, wherein the allocated first portion of the MAC address does not conflict with other MAC addresses associated with the initiating WTRU (902). Based on the negotiated MAC address allocation scheme, the initiating WTRU (902) may allocate a portion of its WTRU MAC address (e.g., 5 most significant bytes) (step 3). The initiating WTRU (902) may randomly allocate a WTRU MAC address based on the MAC address allocation scheme, and / or select from a range of MAC addresses configured / reserved by the network for that WTRU. The initiating WTRU (902) may ensure that the portion of the MAC address value does not conflict with other MAC addresses already used by the initiating WTRU or other WTRUs communicating with the initiating WTRU (902). Based on the negotiated MAC address allocation scheme, the initiating WTRU (902) may additionally allocate the missing portion to complete a portion of the WTRU MAC address of the target WTRU (904) (if received in a DSM command message, or if the first portion of the MAC address of the target WTRU (904) will be completed by the target WTRU (904)). The initiating WTRU (902) may send a DSM completion message to the target WTRU (904), wherein the DSM completion message may contain the first portion of the MAC address associated with the initiating WTRU (902).The initiating WTRU (902) may send a DSM completion message to the target WTRU (904), which contains a portion of the WTRU MAC address of the initiating WTRU (902) (step 4). This message may contain a new complete MAC address for the target WTRU (904), or a portion of the initiating WTRU required to complete the MAC address of the target WTRU (904), or a first portion of the MAC address of the target WTRU (904) that will be completed by the target WTRU (904). The complete MAC address associated with the initiating WTRU (902) may contain a second portion of the complete MAC address, which, when combined with the first portion of the MAC address, forms the complete MAC address associated with the initiating WTRU (902). The target WTRU (904) may allocate the missing portion to complete the portion of the WTRU MAC address of the initiating WTRU (902) (e.g., 1 least significant byte), thereby forming a new complete MAC address (step 5). The target WTRU (904) may allocate the missing portion to complete the portion of the WTRU MAC address of the target WTRU (904). The target WTRU (904) can ensure that the newly formed MAC address value does not conflict with other MAC addresses already used by the target WTRU (904) or other WTRUs communicating with the target WTRU (904). The target WTRU (904) can send a DCA message to the initiating WTRU (902) containing the new complete MAC address of the initiating WTRU (902), or containing a portion of the target WTRU's MAC address required to complete the WTRU's MAC address (e.g., least significant byte) (step 6). The target WTRU (904) can include its new complete MAC address in the DCA message sent to the initiating WTRU (902), or contain a portion of the target WTRU's MAC address required to complete the target WTRU's MAC address. The initiating WTRU and the target WTRU can use the newly formed MAC address to exchange traffic. The initiating WTRU (902) can use the complete MAC address associated with the initiating WTRU (902) to exchange traffic with the target WTRU (904).

[0128] Figure 10 An exemplary process for updating conflict-free MAC addresses is described. Figure 10An exemplary process for establishing a new conflict-free MAC address between two communicating WTRUs is described. For privacy reasons, the communicating WTRUs may change their MAC addresses periodically or upon application triggering. Based on a negotiated MAC address allocation scheme, the initiating WTRU (1002) may allocate a portion of its WTRU MAC address (step 1). The initiating WTRU (1002) may ensure that the portion of its MAC address value does not conflict with other MAC addresses already used by the initiating WTRU (1002) or other WTRUs communicating with it. The initiating WTRU (1002) may send a Link Identifier Update (LIU) request message to update its MAC address with that of the target WTRU (1004) (step 2). This message may contain a portion of the initiating WTRU (1002)'s WTRU MAC address. The target WTRU (1004) may allocate the missing portion to complete the portion of the initiating WTRU (1002)'s WTRU MAC address, thus forming a new complete MAC address (step 3). The target WTRU (1004) can ensure that the newly formed MAC address value of the initiating WTRU (1002) does not conflict with other MAC addresses already used by the target WTRU (1004) or other WTRUs communicating with the target WTRU (1004). The target WTRU (1004) can allocate a partial WTRU MAC address for itself. The target WTRU (1004) can ensure that this partial MAC address value does not conflict with other MAC addresses already used by the target WTRU (1004). The target WTRU (1004) can send a LIU response message to the initiating WTRU (1002) (step 4). This message can contain a new complete MAC address or its missing portion used by the initiating WTRU (1002). This message can also contain a partial WTRU MAC address of the target WTRU (1004). The initiating WTRU (1002) can allocate the missing portion to complete the partial WTRU MAC address of the target WTRU (1004), thereby forming a new complete MAC address (step 5). The initiating WTRU (1002) ensures that the newly formed MAC address value of the target WTRU (1004) does not conflict with any other MAC address already used by the initiating WTRU (1002) or other WTRUs communicating with it. The initiating WTRU (1002) may send a LIU acknowledgment message (step 6) to the target WTRU (1004). This message may contain the new complete MAC address or its missing portion for the target WTRU (1004). Figure 11 An exemplary process for conflict-free MAC address negotiation via U2U relay is described. MAC address negotiation can be used when communication is conducted via U2U relay. In this case, the MAC address allocation process can be run after the PC5 link is established.

[0129] Figure 11 An exemplary process for conflict-free MAC address negotiation via U2U relay is described. Figure 11The process can be initiated by either the source WTRU (1102) or the destination WTRU (1106), with the destination WTRU (1106) acting as the initiator. The source WTRU (1102) and the relay (1104) (e.g., a U2U relay) can establish a PC5 link (Step 1 – Left). The relay (1104) and the destination WTRU (1106) establish a PC5 link (Step 1 – Right). The source or destination WTRU can decide to negotiate a MAC address with the source WTRU (1102) via the relay (1104) using a conflict avoidance negotiation protocol (Step 2). Support for MAC address negotiation can be indicated in the DCR sent by the initiating WTRU (e.g., 1102 or 1106) and the relay (1104), and accepted in the DCA from the peer WTRU and the relay (1104). When an acceptance of MAC address negotiation is received from the relay (1104) (and the peer WTRU) (e.g., in a DCA), the process can be triggered by the end WTRU (e.g., 1102 or 1106). Once a PC5 link is established with the relay (1104), the target WTRU (1106) can trigger a MAC address allocation process with the source WTRU (1102) via the relay (1104). The target WTRU (1102) can send a PC5 MAC address allocation request to the relay (1104), which includes a portion of its own WTRU MAC address. The relay (1104) can then forward this message to the source WTRU (1102). The source WTRU (1102) can allocate the missing portion to complete the target WTRU (1106)'s partial WTRU MAC address, thus forming a complete MAC address (step 3). The source WTRU (1102) can also allocate a portion of its own WTRU MAC address. The source WTRU (1102) can send a PC5 MAC address allocation response to the relay (1104), which includes a partial WTRU MAC address for itself and a complete MAC address or its missing portion for the target WTRU (1106). The relay (1104) can record the complete MAC address of the target WTRU (1106) associated with the PC5 link. The relay (1104) can send a message to the target WTRU (1106). The target WTRU (1106) can record its own complete MAC address associated with the PC5 link. The target WTRU (1106) can allocate the missing portion to complete the partial WTRU MAC address of the source WTRU (1102), thus forming a complete MAC address (step 4). The target WTRU (1106) can send a PC5 MAC address allocation confirmation to the relay, which includes the complete MAC address or its missing portion for the source WTRU (1102).

[0130] The relay (1104) can record the complete MAC address of the source WTRU (1102) associated with the PC5 link. The relay (1104) can send this message to the source WTRU (1102). The source WTRU (1102) can record its own complete MAC address associated with the PC5 link.

Claims

1. A first wireless transmit / receive unit (WTRU), comprising: transceiver; as well as Processor, the processor being configured to: The transceiver sends a Direct Communication Request (DCR) message to the second WTRU, the DCR message including an indication of a request for the first WTRU to establish a link with the third WTRU, wherein the link is configured to relay traffic between the first WTRU and the third WTRU; Receive Direct Security Mode (DSM) command messages from the second WTRU via the transceiver; The transceiver sends a response message to the second WTRU, the response message including an indication of the media access control (MAC) address of the first WTRU; and A direct communication (DC) rejection message is received from the second WTRU via the transceiver. The DC rejection message includes a reason code indicating a MAC address conflict associated with the MAC address of the first WTRU.

2. The first WTRU as claimed in claim 1, wherein the response message includes a DSM completion message.

3. The first WTRU as described in claim 1 or 2, wherein the DSM command message is configured to establish a secure link between the first WTRU and the second WTRU.

4. The first WTRU as claimed in any one of claims 1 to 3, wherein the MAC address conflict associated with the MAC address of the first WTRU corresponds to the MAC address of the first WTRU being used by another WTRU associated with the second WTRU.

5. The first WTRU as described in any one of claims 1 to 4, wherein the processor is further configured to send a second DCR message to the second WTRU after receiving the DC rejection message, wherein the second DCR message includes an indication of a second request for the first WTRU to establish a link with the third WTRU.

6. The first WTRU as claimed in claim 5, wherein the processor is further configured to receive a second DSM command message from the second WTRU.

7. The first WTRU of claim 6, wherein the processor is further configured to send a second response message to the second WTRU, wherein the second response message includes a DSM completion message, and wherein the second response message includes an indication of a second Media Access Control (MAC) address of the first WTRU.

8. A method performed by a first wireless transmit / receive unit (WTRU), the method comprising: Send a Direct Communication Request (DCR) message to the second WTRU, the DCR message including an indication of a request for the first WTRU to establish a link with the third WTRU, wherein the link is configured to relay traffic between the first WTRU and the third WTRU; Receive Direct Safety Mode (DSM) command messages from the second WTRU; Send a response message to the second WTRU, the response message including an indication of the media access control (MAC) address of the first WTRU; and A direct communication (DC) rejection message is received from the second WTRU, the DC rejection message including a reason code indicating a MAC address conflict associated with the MAC address of the first WTRU.

9. The method of claim 8, wherein the response message includes a DSM completion message.

10. The method of claim 8 or 9, wherein the DSM command message is configured to establish a secure link between the first WTRU and the second WTRU.

11. The method of any one of claims 8 to 10, wherein the MAC address conflict associated with the MAC address of the first WTRU corresponds to the MAC address of the first WTRU being used by another WTRU associated with the second WTRU.

12. The method of any one of claims 8 to 11, further comprising, upon receiving the DC rejection message, sending a second DCR message to the second WTRU, wherein the second DCR message includes an indication of a second request for the first WTRU to establish a link with the third WTRU.

13. The method of claim 12, further comprising receiving a second DSM command message from the second WTRU.

14. The method of claim 13, further comprising sending a second response message to the second WTRU, wherein the second response message includes a DSM completion message, and wherein the second response message includes an indication of a second media access control (MAC) address of the first WTRU.

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