Method of listen before talk recovery procedure and related device

1. A method of a listen before talk (LBT) recovery procedure performed by a user equipment (UE), the method comprising:

performing an LBT failure detection procedure for a serving cell;

triggering the LBT recovery procedure for a first bandwidth part (BWP) of the serving cell in response to detecting consistent uplink (UL) LBT failures in the first BWP of the serving cell via the LBT failure detection procedure, the LBT recovery procedure comprising triggering an LBT failure procedure for the first BWP for determining the first BWP as an invalid BWP; and

cancelling the triggered LBT recovery procedure for the first BWP of the serving cell in response to confirming a predefined condition in the UE is met,

wherein the LBT recovery procedure further comprises:

transmitting an LBT failure medium access control (MAC) control element (CE) indicating that the LBT failure procedure is triggered for the serving cell to a network on the serving cell in a case that the serving cell is a Special Cell (SpCell), or transmitting the LBT failure MAC CE to the network on another serving cell on which no LBT failure procedure is triggered in a case that the serving cell is a Secondary Cell (SCell);

switching from the first BWP to a second BWP of the serving cell in response to no LBT failure procedure being triggered for the second BWP and the second BWP being configured with a physical random access channel (PRACH) resource in a case that the serving cell is the SpCell; and

initiating a random access procedure on the second BWP of the serving cell in a case that the serving cell is the SpCell.

2. The method of claim 1 , wherein the predefined condition comprises one of:

a physical downlink control channel (PDCCH) that indicates to the UE to perform BWP switching on the serving cell is received by the UE;

the PDCCH that indicates to the UE to perform the BWP switching on the serving cell is received by the UE and a second random access procedure on the serving cell is not performed by the UE;

a radio resource control (RRC) configuration or reconfiguration message to configure or reconfigure the BWP switching on the serving cell is received by the UE;

a MAC reset for a MAC entity corresponding to the serving cell is performed by the UE;

the serving cell is deactivated or activated;

the random access procedure for the LBT recovery procedure on the serving cell is performed by the UE and the random access procedure is successfully completed on the serving cell; and

the LBT failure MAC CE is transmitted by the UE, the LBT failure MAC CE indicating at least one cell for which the LBT recovery procedure is triggered, the at least one cell including the serving cell for which the LBT recovery procedure is triggered.

3. The method of claim 1 , further comprising:

resetting an LBT counter corresponding to the serving cell in response to the cancellation of the triggered LBT recovery procedure; and

incrementing the LBT counter by the UE when an LBT failure is detected on the serving cell via the LBT failure detection procedure.

4. The method of claim 3 , wherein resetting the LBT counter comprises setting the LBT counter to zero when cancelling the triggered LBT recovery procedure for the serving cell.

5. The method of claim 1 , wherein the serving cell is the SpCell including at least one of a Primary Cell (PCell) or a Primary Secondary Cell Group (SCG) Cell (PSCell), or the serving cell is the SCell.

6. A user equipment (UE) for performing a listen before talk (LBT) recovery procedure, the UE comprising:

at least one processor; and

at least one non-transitory computer-readable medium coupled to the at least one processor and storing computer-executable instructions that, executed by the at least one processor, cause the UE to:

perform an LBT failure detection procedure for a serving cell;

trigger the LBT recovery procedure for a first bandwidth part (BWP) of the serving cell in response to detecting consistent uplink (UL) LBT failures in the first BWP of the serving cell via the LBT failure detection procedure, the LBT recovery procedure comprising triggering an LBT failure procedure for the first BWP for determining the first BWP as an invalid BWP; and

cancel the triggered LBT recovery procedure for the first BWP of the serving cell in response to confirming a predefined condition in the UE is met,

wherein the LBT recovery procedure further comprises:

transmitting an LBT failure medium access control (MAC) control element (CE) indicating that the LBT failure procedure is triggered for the serving cell to a network on the serving cell in a case that the serving cell is a Special Cell (SpCell), or transmitting the LBT failure MAC CE to the network on another serving cell on which no LBT failure procedure is triggered in a case that the serving cell is a Secondary Cell (SCell);

switching from the first BWP to a second BWP of the serving cell in response to no LBT failure procedure being triggered for the second BWP and the second BWP being configured with a physical random access channel (PRACH) resource in a case that the serving cell is the SpCell; and

initiating a random access procedure on the second BWP of the serving cell in a case that the serving cell is the SpCell.

7. The UE of claim 6 , wherein the predefined condition comprises one of:

a physical downlink control channel (PDCCH) that indicates to the UE to perform BWP switching on the serving cell is received by the UE;

the PDCCH that indicates to the UE to perform the BWP switching on the serving cell is received by the UE and a second random access procedure on the serving cell is not performed by the UE;

a radio resource control (RRC) configuration or reconfiguration message to configure or reconfigure the BWP switching on the serving cell is received by the UE;

a MAC reset for a MAC entity corresponding to the serving cell is performed by the UE;

the serving cell is deactivated or activated;

the random access procedure for the LBT recovery procedure on the serving cell is performed by the UE and the random access procedure is successfully completed on the serving cell; and

the LBT failure MAC CE is transmitted by the UE, the LBT failure MAC CE indicating at least one cell for which the LBT recovery procedure is triggered, the at least one cell including the serving cell for which the LBT recovery procedure is triggered.

8. The UE of claim 6 , wherein the computer-executable instructions, when executed by the at least one processor, further cause the UE to:

reset an LBT counter corresponding to the serving cell in response to the cancellation of the triggered LBT recovery procedure; and

increment the LBT counter by the UE when an LBT failure is detected on the serving cell via the LBT failure detection procedure.

9. The UE of claim 8 , wherein resetting the LBT counter comprises setting the LBT counter to zero when cancelling the triggered LBT recovery procedure for the serving cell.

10. The UE of claim 6 , wherein the serving cell is the SpCell including at least one of a Primary Cell (PCell) or a Primary Secondary Cell Group (SCG) Cell (PSCell), or the serving cell is the SCell.