Methods and apparatuses for listen before talk failure detection and recovery

1. A method performed by a User Equipment (UE) for Listen Before Talk (LBT) failure detection and recovery, the method comprising:

triggering a first consistent LBT failure procedure for a first consistent LBT failure detected on a first Bandwidth Part (BWP) of a first cell of a Base Station (BS);

triggering a second consistent LBT failure procedure for a second consistent LBT failure detected on a second BWP of a second cell of the BS;

triggering a first Scheduling Request (SR) procedure for the first consistent LBT failure detected on the first BWP;

triggering a second SR procedure for the second consistent LBT failure detected on the second BWP;

receiving, from the BS, an indication for BWP switching of the first cell;

switching an active BWP of the first cell based on the indication;

canceling the first consistent LBT failure procedure, without canceling the second consistent LBT failure procedure, in response to receiving the indication; and

canceling the first SR procedure, without canceling the second SR procedure, in response to receiving the indication.

2. The method of claim 1 , further comprising:

in a case that the first consistent LBT failure procedure and the first SR procedure have not been canceled, canceling the first consistent LBT failure procedure and canceling the second consistent LBT failure procedure when the UE transmits an LBT failure Medium Access Control (MAC) Control Element (CE) to the BS, the LBT failure MAC CE indicating a first index of the first cell and a second index of the second cell; and

canceling the first SR procedure and canceling the second SR procedure when the UE transmits the LBT failure MAC CE to the BS.

3. The method of claim 1 , further comprising:

deactivating the second cell when at least one of a plurality of conditions is fulfilled;

canceling the second consistent LBT failure procedure in response to deactivating the second cell; and

canceling the second SR procedure in response to deactivating the second cell,

wherein the plurality of conditions comprises at least one of:

a Secondary Cell (SCell) Activation/Deactivation Medium Access Control (MAC) Control Element (CE) for deactivating the second cell being received from the BS, or

expiration of an SCell deactivation timer configured for the second cell.

4. The method of claim 1 , further comprising:

receiving, from the BS, a Radio Resource Control (RRC) message for reconfiguring an LBT failure recovery configuration of the second cell;

canceling the second consistent LBT failure procedure in response to receiving the RRC message; and

canceling the second SR procedure in response to receiving the RRC message.

5. The method of claim 1 , wherein the indication is received on a Physical Downlink Control Channel (PDCCH) or via Radio Resource Control (RRC) signaling.

6. The method of claim 1 , wherein at least one of the first SR procedure and the second SR procedure is triggered when at least one of a plurality of conditions is fulfilled, the plurality of conditions comprising at least one of:

no Uplink Shared Channel (UL-SCH) resource being available for a new transmission, and

as a result of logical channel prioritization, an UL-SCH resource allocated to the UE not being able to accommodate an LBT failure Medium Access Control (MAC) Control Element (CE) and a sub-header of the LBT failure MAC CE.

7. The method of claim 1 , further comprising:

after canceling the first consistent LBT failure procedure and the first SR procedure, performing operations including:

transmitting, to the BS, an SR for the second consistent LBT failure on a Physical Uplink Control Channel (PUCCH) resource to request an Uplink Shared Channel (UL-SCH) resource; and

transmitting, to the BS, an LBT failure Medium Access Control (MAC) Control Element (CE) via the UL-SCH resource after the UL-SCH resource is allocated to the UE, the LBT failure MAC CE indicating a second index of the second cell and not indicating a first index of the first cell.

8. The method of claim 1 , further comprising:

initiating a Random Access (RA) procedure on a Special Cell (SpCell) in a case that the UE is not configured with any valid Physical Uplink Control Channel (PUCCH) resource for the second SR procedure; and

canceling the second SR procedure after initiating the RA procedure.

9. The method of claim 1 , wherein the first BWP and the second BWP are Uplink (UL) BWPs, and the active BWP is one of a Downlink (DL) BWP and an UL BWP.

10. The method of claim 1 , wherein the first cell and the second cell are Secondary Cells (SCells).

11. A User Equipment (UE) for Listen Before Talk (LBT) failure detection and recovery, the UE comprising:

a memory storing one or more instructions; and

at least one processor coupled to the memory, the at least one processor being configured to execute the instructions to:

trigger a first consistent LBT failure procedure for a first consistent LBT failure detected on a first Bandwidth Part (BWP) of a first cell of a Base Station (BS);

trigger a second consistent LBT failure procedure for a second consistent LBT failure detected on a second BWP of a second cell of the BS;

trigger a first Scheduling Request (SR) procedure for the first consistent LBT failure detected on the first BWP;

trigger a second SR procedure for the second consistent LBT failure detected on the second BWP;

receive, from the BS, an indication for BWP switching of the first cell;

switch an active BWP of the first cell based on the indication;

cancel the first consistent LBT failure procedure, without canceling the second consistent LBT failure procedure, in response to receiving the indication; and

cancel the first SR procedure, without canceling the second SR procedure, in response to receiving the indication.

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

in a case that the first consistent LBT failure procedure and the first SR procedure have not been canceled, cancel the first consistent LBT failure procedure and cancel the second consistent LBT failure procedure when the UE transmits an LBT failure Medium Access Control (MAC) Control Element (CE) to the BS, the LBT failure MAC CE indicating a first index of the first cell and a second index of the second cell; and

cancel the first SR procedure and cancel the second SR procedure when the UE transmits the LBT failure MAC CE to the BS.

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

deactivate the second cell when at least one of a plurality of conditions is fulfilled;

cancel the second consistent LBT failure procedure in response to deactivating the second cell; and

cancel the second SR procedure in response to deactivating the second cell,

wherein the plurality of conditions comprises at least one of:

a Secondary Cell (SCell) Activation/Deactivation Medium Access Control (MAC) Control Element (CE) for deactivating the second cell being received from the BS, or

expiration of a SCell deactivation timer configured for the second cell.

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

receive, from the BS, a Radio Resource Control (RRC) message for reconfiguring an LBT failure recovery configuration of the second cell;

cancel the second consistent LBT failure procedure in response to receiving the RRC message; and

cancel the second SR procedure in response to receiving the RRC message.

15. The UE of claim 11 , wherein the indication is received on a Physical Downlink Control Channel (PDCCH) or via Radio Resource Control (RRC) signaling.

16. The UE of claim 11 , wherein at least one of the first SR procedure and the second SR procedure is triggered when at least one of a plurality of conditions is fulfilled, the plurality of conditions comprising at least one of:

no Uplink Shared Channel (UL-SCH) resource being available for a new transmission, and

as a result of logical channel prioritization, an UL-SCH resource allocated to the UE not being able to accommodate an LBT failure Medium Access Control (MAC) Control Element (CE) and a sub-header of the LBT failure MAC CE.

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

after canceling the first consistent LBT failure procedure and the first SR procedure, perform operations including:

transmitting, to the BS, an SR for the second consistent LBT failure on a Physical Uplink Control Channel (PUCCH) resource to request an Uplink Shared Channel (UL-SCH) resource; and

transmitting, to the BS, an LBT failure Medium Access Control (MAC) Control Element (CE) via the UL-SCH resource after the UL-SCH resource is allocated to the UE, the LBT failure MAC CE indicating a second index of the second cell and not indicating a first index of the first cell.

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

initiate a Random Access (RA) procedure on a Special Cell (SpCell) in a case that the UE is not configured with any valid Physical Uplink Control Channel (PUCCH) resource for the second SR procedure; and

cancel the second SR procedure after initiating the RA procedure.

19. The UE of claim 11 , wherein the first BWP and the second BWP are Uplink (UL) BWPs, and the active BWP is one of a Downlink (DL) BWP and an UP BWP.

20. The UE of claim 11 , wherein the first cell and the second cell are Secondary Cells (SCells).