Method and apparatus for a user equipment (UE) to transmit a direct communication request message in a wireless communication system
A method and device are disclosed from the perspective of a first User Equipment (UE) to perform a PC5 unicast link establishment procedure. In one embodiment, the method includes the first UE transmitting a first PC5-S message for establishing a PC5 unicast link with a UE-to-UE Relay, wherein the PC5-S message includes a Layer-2 Identity (ID) of a second UE. The method further includes the first UE receiving a second PC5-S message from the UE-to-UE Relay, wherein the second PC5-S message is transmitted by the UE-to-UE Relay in response to reception of the first PC5-S message.
1. A method for a first User Equipment (UE) to perform a PC5 unicast link establishment procedure, comprising:
transmitting to a UE-to-UE Relay a first PC5-S message for establishing a PC5 unicast link with the UE-to-UE Relay, wherein the first PC5-S message is addressed to a default Destination Layer-2 Identity (ID) configured by a network and includes a Layer-2 ID of a second UE different than the UE-to-UE Relay, and wherein the Layer-2 ID is self-assigned by the second UE; and
receiving a second PC5-S message from the UE-to-UE Relay, wherein the second PC5-S message is transmitted by the UE-to-UE Relay in response to reception of the first PC5-S message.
2. The method of claim 1 , wherein the default Destination Layer-2 ID is associated with a UE-to-UE Relay service.
3. The method of claim 1 , wherein the first PC5-S message includes the first UE's Application Layer ID.
4. The method of claim 1 , wherein the first PC5-S message includes the second UE's Application Layer ID.
5. The method of claim 1 , wherein the first PC5-S message includes Service Info of a Proximity-based Services (ProSe) service.
6. The method of claim 5 , wherein the Service Info of the ProSe service is an identity of the ProSe service.
7. The method of claim 1 , wherein the first PC5-S message is a Direct Communication Request message or a DIRECT LINK ESTABLISHMENT REQUEST message.
8. The method of claim 1 , wherein the second PC5-S message is a Direct Communication Accept message or a DIRECT LINK ESTABLISHMENT ACCEPT message.
9. A first User Equipment (UE), comprising:
a processor; and
a memory operatively coupled to the processor, wherein the processor is configured to execute a program code to:
transmit to a UE-to-UE Relay a first PC5-S message for establishing a PC5 unicast link with the UE-to-UE Relay, wherein the first PC5-S message is addressed to a default Destination Layer-2 Identity (ID) configured by a network and includes a Layer-2 of a second UE different than the UE-to-UE Relay, and wherein the Layer-2 ID is self-assigned by the second UE; and
receive a second PC5-S message from the UE-to-UE Relay, wherein the second PC5-S message is transmitted by the UE-to-UE Relay in response to reception of the first PC5-S message.
10. The first UE of claim 9 , wherein the default Destination Layer-2 ID is associated with a UE-to-UE Relay service.
11. The first UE of claim 9 , wherein the first PC5-S message includes the first UE's Application Layer ID.
12. The first UE of claim 9 , wherein the first PC5-S message includes the second UE's Application Layer ID.
13. The first UE of claim 9 , wherein the first PC5-S message includes Service Info of a Proximity-based Services (ProSe) service.
14. The first UE of claim 13 , wherein the Service Info of the ProSe service is an identity of the ProSe service.
15. The first UE of claim 9 , wherein the first PC5-S message is a Direct Communication Request message or a DIRECT LINK ESTABLISHMENT REQUEST message.
16. The first UE of claim 9 , wherein the second PC5-S message is a Direct Communication Accept message or a DIRECT LINK ESTABLISHMENT ACCEPT message.
17. The method of claim 1 , wherein the first UE is a Source UE.
18. The method of claim 1 , wherein the second UE is a Target UE.
19. The first UE of claim 9 , wherein the first UE is a Source UE.
20. The first UE of claim 9 , wherein the second UE is a Target UE.