Method and apparatus for sidelink operation

1. A user equipment (UE) comprising:

one or more non-transitory computer-readable media containing computer-executable instructions embodied therein; and

at least one processor coupled to the one or more non-transitory computer-readable media, the at least one processor configured to execute the computer-executable instructions to:

receive, from a first cell, a conditional handover command that includes an indication of a second cell and one or more triggering conditions for handover to the second cell;

perform handover to the second cell after determining that at least one of the triggering conditions is fulfilled; and

apply a sidelink resource configuration that is stored in the UE after performing handover to the second cell based on the conditional handover command, the sidelink resource configuration having an associated Channel Busy Ratio (CBR) measurement configuration; and

apply the CBR measurement configuration after performing handover to the second cell.

2. The UE of claim 1 , wherein the sidelink resource configuration is included in the conditional handover command.

3. The UE of claim 1 , wherein the at least one processor is further configured to execute the computer-executable instructions to:

receive area-scope system information associated with a first system information area identifier (ID);

store the sidelink resource configuration along with the first system information area ID; and

receive, from the second cell, a system information block (SIB) that includes a second system information area ID that is equal to the first system information area ID.

4. The UE of claim 3 , wherein the at least one processor is further configured to execute the computer-executable instructions to:

transmit a system information request message through UE-specific unicast control signaling to the first cell, wherein the area-scope system information is received from the first cell after the transmission of the system information request message.

5. The UE of claim 4 , wherein the area-scope system information is received from the first cell through UE-specific unicast control signaling.

6. The UE of claim 3 , wherein the area-scope system information is divided into at least two segments.

7. The UE of claim 1 , wherein the sidelink resource configuration includes a normal sidelink resource pool configuration and an exceptional sidelink resource pool configuration, and the at least one processor is further configured to execute the computer-executable instructions to:

apply the exceptional sidelink resource pool configuration during the handover procedure to the second cell.

8. The UE of claim 7 , wherein each of the normal sidelink resource pool configuration and the exceptional sidelink resource pool configuration is associated with one sidelink bandwidth part (BWP) in one sidelink component carrier, wherein the UE applies the sidelink resource pool configuration associated with one or more sidelink component carriers when performing handover to the second cell based on the conditional handover command.

9. The UE of claim 1 , wherein the at least one processor is further configured to execute the computer-executable instructions to:

apply the sidelink resource configuration during a radio resource control (RRC) re-establishment procedure with the second cell.

10. The UE of claim 1 , wherein the at least one processor is further configured to execute the computer-executable instructions to:

apply the sidelink resource configuration after determining that at least one of the triggering conditions is fulfilled and radio link failure occurs.

11. The UE of claim 1 , wherein the at least one processor is further configured to execute the computer-executable instructions to:

apply the sidelink resource configuration after the UE moves to a radio resource control (RRC) inactive state or an RRC idle state.

12. The UE of claim 1 , wherein the sidelink resource configuration includes at least one of a resource configuration for New Radio (NR) sidelink operation and a resource configuration for Long Term Evolution (LTE) Vehicle-to-Everything (V2X) service.

13. A method for sidelink operation performed by a user equipment (UE), the method comprising:

receiving, from a first cell, a conditional handover command that includes an indication of a second cell and one or more triggering conditions for handover to the second cell;

performing handover to the second cell after determining that at least one of the triggering conditions is fulfilled; and

applying a sidelink resource configuration that is stored in the UE after performing handover to the second cell based on the conditional handover command, the sidelink resource configuration having an associated Channel Busy Ratio (CBR) measurement configuration; and

applying the CBR measurement configuration after performing handover to the second cell.

14. The method of claim 13 , wherein the sidelink resource configuration is included in the conditional handover command.

15. The method of claim 13 , further comprising:

receiving area-scope system information associated with a first system information area identifier (ID);

storing the sidelink resource configuration along with the first system information area ID; and

receiving, from the second cell, a system information block (SIB) that includes a second system information area ID that is equal to the first system information area ID.

16. The method of claim 15 , further comprising:

transmitting a system information request message through UE-specific unicast control signaling to the first cell, wherein the area-scope system information is received from the first cell after the transmission of the system information request message.

17. The method of claim 16 , wherein the area-scope system information is received from the first cell through UE-specific unicast control signaling.

18. The method of claim 15 , wherein the area-scope system information is divided into at least two segments.

19. The method of claim 13 , wherein the sidelink resource configuration includes a normal sidelink resource pool configuration and an exceptional sidelink resource pool configuration, and the method further comprises:

applying the exceptional sidelink resource pool configuration during the handover procedure to the second cell.

20. The method of claim 19 , wherein each of the normal sidelink resource pool configuration and the exceptional sidelink resource pool configuration is associated with one sidelink bandwidth part (BWP) in one sidelink component carrier, wherein the UE applies the sidelink resource pool configuration associated with one or more sidelink component carriers when performing handover to the second cell based on the conditional handover command.

21. The method of claim 13 , further comprising:

applying the sidelink resource configuration during a radio resource control (RRC) re-establishment procedure with the second cell.

22. The method of claim 13 , further comprising:

applying the sidelink resource configuration after determining that at least one of the triggering conditions is fulfilled and radio link failure occurs.

23. The method of claim 13 , further comprising:

applying the sidelink resource configuration after the UE moves to a radio resource control (RRC) inactive state or an RRC idle state.

24. The method of claim 13 , wherein the sidelink resource configuration includes at least one of a resource configuration for New Radio (NR) sidelink operation and a resource configuration for Long Term Evolution (LTE) Vehicle-to-Everything (V2X) service.