Method and apparatus for sidelink signaling radio bearer (SRB) establishment in a wireless communication system
A method and apparatus are disclosed. The first UE establishes a first sidelink Signaling Radio Bearer (SRB) for PC5-S message transmission if a unicast link or a PC5-Radio Resource Control (PC5-RRC) connection establishment is initiated, wherein the first sidelink SRB is associated with a default Destination Layer-2 Identity (ID). Also, the first UE transmits a first PC5-S message for the unicast link or the PC5-RRC connection establishment on the first sidelink SRB with a Source Layer-2 ID derived from a Layer-2 ID of the first UE and a Destination Layer-2 ID derived from the default Destination Layer-2 ID. Furthermore, the first UE receives a second PC5-S message from a second UE, wherein the second PC5-S message is transmitted with a Source Layer-2 ID derived from a Layer-2 ID of the second UE and a Destination Layer-2 ID derived from the Layer-2 ID of the first UE. In addition, the first UE establishes a second sidelink SRB for PC5-S message reception and/or transmission, wherein the second sidelink SRB is associated with the Layer-2 ID of the second UE. Furthermore, the first UE establishes a third sidelink SRB for PC5-RRC message transmission if the unicast link or the PC5-RRC connection establishment has been successfully completed, wherein the third sidelink SRB is associated with the Layer-2 ID of the second UE.
1. A method for unicast link establishment by a first User Equipment (UE), comprising:
establishing a first sidelink Signaling Radio Bearer (SRB) for PC5-S message transmission in response to a unicast link or a PC5-Radio Resource Control (PC5-RRC) connection establishment being initiated, wherein the first sidelink SRB is associated with a default Destination Layer-2 Identity (ID);
transmitting a first PC5-S message for the unicast link or the PC5-RRC connection establishment on the first sidelink SRB with a Source Layer-2 ID derived from a Layer-2 ID of the first UE and a Destination Layer-2 ID derived from the default Destination Layer-2 ID;
receiving a second PC5-S message from a second UE, wherein the second PC5-S message is transmitted with a Source Layer-2 ID derived from a Layer-2 ID of the second UE and a Destination Layer-2 ID derived from the Layer-2 ID of the first UE;
establishing a second sidelink SRB for PC5-S message reception and/or transmission, wherein the second sidelink SRB is associated with the Layer-2 ID of the second UE; and
establishing a third sidelink SRB for PC5-RRC message transmission in response to the unicast link or the PC5-RRC connection establishment being successfully completed, wherein the third sidelink SRB is associated with the Layer-2 ID of the second UE.
2. The method of claim 1 , further comprising:
establishing a fourth sidelink SRB for protected PC5-S message transmission, wherein the fourth sidelink SRB is associated with the Layer-2 ID of the second UE.
3. The method of claim 1 , further comprising:
not establishing any sidelink SRB for PC5-RRC message transmission before the unicast link or the PC5-RRC connection establishment has been successfully completed.
4. The method of claim 1 , wherein the second sidelink SRB is established in response to reception of the second PC5-S message by a physical layer of the first UE.
5. The method of claim 1 , wherein a first Sidelink Control Channel (SCCH) configuration specified in a RRC specification is used for establishing the first sidelink SRB and the second sidelink SRB.
6. The method of claim 1 , wherein a second Sidelink Control Channel (SCCH) configuration specified in a RRC specification is used for establishing the third sidelink SRB.
7. The method of claim 1 , wherein the default Destination Layer-2 ID is associated with a sidelink service for which the unicast link or the PC5-RRC connection is established.
8. The method of claim 1 , wherein the first PC5-S message is a Direct Communication Request.
9. The method of claim 1 , wherein the second PC5-S message is a security related message.
10. The method of claim 1 , wherein each sidelink SRB corresponds to a Sidelink Control Channel (SCCH).
11. A first UE (User Equipment) for establishing unicast link, comprising:
a control circuit;
a processor installed in the control circuit; and
a memory installed in the control circuit and operatively coupled to the processor;
wherein the processor is configured to execute a program code stored in the memory to:
establish a first sidelink Signaling Radio Bearer (SRB) for PC5-S message transmission in response to a unicast link or a PC5-Radio Resource Control (PC5-RRC) connection establishment being initiated, wherein the first sidelink SRB is associated with a default Destination Layer-2 Identity (ID);
transmit a first PC5-S message for the unicast link or the PC5-RRC connection establishment on the first sidelink SRB with a Source Layer-2 ID derived from a Layer-2 ID of the first UE and a Destination Layer-2 ID derived from the default Destination Layer-2 ID;
receive a second PC5-S message from a second UE, wherein the second PC5-S message is transmitted with a Source Layer-2 ID derived from a Layer-2 ID of the second UE and a Destination Layer-2 ID derived from the Layer-2 ID of the first UE;
establish a second sidelink SRB for PC5-S message reception and/or transmission, wherein the second sidelink SRB is associated with the Layer-2 ID of the second UE; and
establish a third sidelink SRB for PC5-RRC message transmission in response to the unicast link or the PC5-RRC connection establishment being successfully completed, wherein the third sidelink SRB is associated with the Layer-2 ID of the second UE.
12. The first UE of claim 11 , wherein the processor is further configured to execute a program code stored in the memory to:
establish a fourth sidelink SRB for protected PC5-S message transmission, wherein the fourth sidelink SRB is associated with the Layer-2 ID of the second UE.
13. The first UE of claim 11 , wherein the processor is further configured to execute a program code stored in the memory to:
not establish any sidelink SRB for PC5-RRC message transmission before the unicast link or the PC5-RRC connection establishment has been successfully completed.
14. The first UE of claim 11 , wherein the second sidelink SRB is established in response to reception of the second PC5-S message by a physical layer of the first UE.
15. The first UE of claim 11 , wherein a first Sidelink Control Channel (SCCH) configuration specified in a RRC specification is used for establishing the first sidelink SRB and the second sidelink SRB.
16. The first UE of claim 11 , wherein a second Sidelink Control Channel (SCCH) configuration specified in a RRC specification is used for establishing the third sidelink SRB.
17. The first UE of claim 11 , wherein the default Destination Layer-2 ID is associated with a sidelink service for which the unicast link (or the PC5-RRC connection) is established.
18. The first UE of claim 11 , wherein the first PC5-S message is a Direct Communication Request.
19. The first UE of claim 11 , wherein the second PC5-S message is a security related message.
20. The first UE of claim 11 , wherein each sidelink SRB corresponds to a Sidelink Control Channel (SCCH).