Method and apparatus for acknowledging SCell beam failure recovery request

1. A base station (BS) for performing a Secondary Cell (SCell) Beam Failure Recovery (BFR) procedure, the BS comprising:

one or more non-transitory computer-readable media having computer-executable instructions embodied thereon; 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 user equipment (UE), a BFR Medium Access Control (MAC) Control Element (CE) that includes a cell index of an SCell for which a beam failure is detected, and a reference signal index for the S Cell, the BFR MAC CE being transmitted, by the UE, via an uplink (UL) transmission associated with a Hybrid Automatic Repeat Request (HARQ) process having a HARQ process identifier (ID); and

transmit, to the UE, Downlink Control Information (DCI) that schedules a Physical Uplink Shared Channel (PUSCH) transmission with the HARQ process ID of the HARQ process that is used for the UL transmission of the BFR MAC CE, the DCI indicating a toggled New Data Indicator (NDI) value,

wherein the UE is configured to:

determine, upon receiving the DCI, that the SCell BFR procedure is successfully completed; and

monitor, on the S Cell, a Physical Downlink Control Channel (PDCCH) using antenna port quasi-colocation parameters associated with the reference signal index after receiving the DCI.

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

indicate, via at least one Transmission Configuration Indication (TCI) activation MAC CE, beam information to the UE, wherein the UE is further configured to:

apply the beam information to receive the DCI.

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

configure, via signaling, a BFR timer to the UE, wherein the UE is further configured to:

start, before receiving the DCI, the BFR timer; and

stop the BFR timer upon receipt of the DCI.

4. The BS of claim 3 , wherein the UE is further configured to:

start the BFR timer upon detection of the beam failure.

5. The BS of claim 3 , wherein the UE is further configured to:

stop the BFR timer when the S Cell BFR procedure is determined as successfully completed.

6. The BS of claim 3 , wherein starting the BFR timer before receiving the DCI comprises starting the BFR timer when the BFR MAC CE is transmitted.

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

receive a Scheduling Request (SR) for BFR.

8. The BS of claim 7 , wherein the SR requests a UL resource for transmitting the BFR MAC CE.

9. The BS of claim 1 , wherein:

the toggled NDI value is compared to an NDI value associated with the BFR MAC CE, and

the toggled NDI value is different from the NDI value associated with the BFR MAC CE.

10. A method for a Secondary Cell (SCell) Beam Failure Recovery (BFR) procedure performed by a base station (BS), the method comprising:

receiving, from a user equipment (UE), a BFR Medium Access Control (MAC) Control Element (CE) that includes a cell index of an S Cell for which a beam failure is detected, and a reference signal index for the SCell, the BFR MAC CE being transmitted, by the UE, via an uplink (UL) transmission associated with a Hybrid Automatic Repeat Request (HARQ) process having a HARQ process identifier (ID); and

transmitting, to the UE, Downlink Control Information (DCI) that schedules a Physical Uplink Shared Channel (PUSCH) transmission with the HARQ process ID of the HARQ process that is used for the UL transmission of the BFR MAC CE, the DCI indicating a toggled New Data Indicator (NDI) value,

wherein the UE is configured to:

determine, upon receiving the DCI, that the SCell BFR procedure is successfully completed; and

monitor, on the SCell, a Physical Downlink Control Channel (PDCCH) using antenna port quasi-colocation parameters associated with the reference signal index after receiving the DCI.

11. The method of claim 10 , further comprising:

indicating, via at least one Transmission Configuration Indication (TCI) activation MAC CE, beam information to the UE, wherein the UE is further configured to:

apply the beam information to receive the DCI.

12. The method of claim 10 , further comprising:

configuring, via signaling, a BFR timer to the UE, wherein the UE is further configured to:

start, before receiving the DCI, the BFR timer; and

stop the BFR timer upon receipt of the DCI.

13. The method of claim 12 , wherein the UE is further configured to:

start the BFR timer upon detection of the beam failure.

14. The method of claim 12 , wherein the UE is further configured to:

stop the BFR timer when the S Cell BFR procedure is determined as successfully completed.

15. The method of claim 12 , wherein starting the BFR timer before receiving the DCI comprises starting the BFR timer when the BFR MAC CE is transmitted.

16. The method of claim 10 , further comprising:

receiving a Scheduling Request (SR) for BFR.

17. The method of claim 16 , wherein the SR requests a UL resource for transmitting the BFR MAC CE.

18. The method of claim 10 , wherein:

the toggled NDI value is compared to an NDI value associated with the BFR MAC CE, and

the toggled NDI value is different from the NDI value associated with the BFR MAC CE.