Method and apparatus for releasing sidelink radio bearer in a wireless communication system
A method and apparatus are disclosed from the perspective of a first UE (User Equipment) to indicate a network node for releasing SLRB (Sidelink Radio Bearer) or SL-DRB (Sidelink-Data Radio Bearer). In one embodiment, the method includes transmitting a first RRC (Radio Resource Control) message to a network node for requesting sidelink resource, wherein the first RRC message includes a PFI (PC5 QoS Flow Identifier) of a PC5 QoS (Quality of Service) flow in a first list of PC5 QoS flows. The method also includes receiving a second RRC message from the network node, wherein the second RRC message configures a SLRB and maps the PC5 QoS flow to the SLRB. The method further includes transmitting a third RRC message to the network node if the PC5 QoS flow is deactivated or released, wherein the PFI of the PC5 QoS flow is removed from a second list of PC5 QoS flows included in the third RRC message.
1. A method for a first UE (User Equipment) to indicate a network node for releasing SLRB (Sidelink Radio Bearer) or SL-DRB (Sidelink-Data Radio Bearer), comprising:
transmitting a first RRC (Radio Resource Control) message to a network node for requesting sidelink resource, wherein the first RRC message includes a PFI (PC5 QoS Flow Identifier) of a PC5 QoS (Quality of Service) flow in a first list of PC5 QoS flows;
receiving a second RRC message from the network node, wherein the second RRC message configures a SLRB and maps the PC5 QoS flow to the SLRB; and
transmitting a third RRC message to the network node if the PC5 QoS flow is deactivated or released, wherein the PFI of the PC5 QoS flow is removed from a second list of PC5 QoS flows included in the third RRC message.
2. The method of claim 1 , wherein the PC5 QoS flow is to be transmitted on a PC5 unicast link and the PC5 unicast link is established between the first UE and a second UE.
3. The method of claim 1 , further comprising:
receiving a fourth RRC message from the network node, wherein the fourth RRC message reconfigures the UE to release the SLRB.
4. The method of claim 3 , further comprising:
releasing the SLRB according to the fourth RRC message.
5. The method of claim 1 , wherein the PFI of the PC5 QoS flow is not included in the second list of PC5 QoS flows.
6. The method of claim 2 , wherein the first RRC message includes a destination Layer-2 ID associated with the PC5 unicast link.
7. The method of claim 6 , wherein the destination Layer-2 ID (Identity) is a Layer-2 ID of the second UE.
8. The method of claim 1 , wherein the first RRC message or the third RRC message is a SidelinkUEInformation.
9. The method of claim 3 , wherein the second RRC message or the fourth RRC message is a RRC reconfiguration message.
10. The method of claim 1 , wherein the network node is a base station.
11. A first UE (User Equipment), 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:
transmit a first RRC (Radio Resource Control) message to a network node for requesting sidelink resource, wherein the first RRC message includes a PFI (PC5 QoS Flow Identifier) of a PC5 QoS (Quality of Service) flow in a first list of PC5 QoS flows;
receive a second RRC message from the network node, wherein the second RRC message configures a SLRB (Sidelink Radio Bearer) and map the PC5 QoS flow to the SLRB; and
transmit a third RRC message to the network node if the PC5 QoS flow is deactivated or released, wherein the PFI of the PC5 QoS flow is removed from a second list of PC5 QoS flows included in the third RRC message.
12. The first UE of claim 11 , wherein the PC5 QoS flow is to be transmitted on a PC5 unicast link and the PC5 unicast link is established between the first UE and a 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:
receive a fourth RRC message from the network node, wherein the fourth RRC message reconfigures the UE to release the SLRB.
14. The first UE of claim 13 , wherein the processor is further configured to execute a program code stored in the memory to:
release the SLRB according to the fourth RRC message.
15. The first UE of claim 11 , wherein the PFI of the PC5 QoS flow is not included in the second list of PC5 QoS flows.
16. The first UE of claim 12 , wherein the first RRC message includes a destination Layer-2 ID associated with the PC5 unicast link.
17. The first UE of claim 16 , wherein the destination Layer-2 ID is a Layer-2 ID of the second UE.
18. The first UE of claim 11 , wherein the first RRC message or the third RRC message is a SidelinkUEInformation.
19. The first UE of claim 13 , wherein the second RRC message or the fourth RRC message is a RRC reconfiguration message.
20. The first UE of claim 11 , wherein the network node is a base station.