Beam failure recovery in secondary cells

1. One or more non-transitory computer-readable media (NTCRM) comprising instructions for beam failure recovery (BFR), wherein execution of the instructions by one or more processors is to cause a user equipment (UE) to:

in response to detection of a beam failure event in a secondary cell (SCell),

determine one or more beams of the SCell on which to camp, wherein the determination of the one or more beams includes:

determine a set of beam failure detection (BFD)-reference signals (RSs) to measure based on a received BFD configuration,

perform measurement of the set of BFD-RSs, and

determine the one or more beams to be beams associated with the measured BFD-RSs having a signal strength above a configured threshold; and

generate a Medium Access Control (MAC) Control Element (CE) to include an index of the SCell, indications of the determined beams, and indexes of each measured BFD-RS having a signal strength above a configured threshold, and

send the MAC CE to a Radio Access Network (RAN) node over an uplink (UL) channel in the SCell or a UL channel in a primary cell (PCell) associated with the SCell.

2. The one or more NTCRM of claim 1 , wherein execution of the instructions is to cause the UE to:

declare the beam failure event in the SCell when all BFD-RSs configured to the SCell have failed.

3. The one or more NTCRM of claim 1 , wherein the MAC CE is a physical uplink control channel (PUSCH) MAC CE.

4. The one or more NTCRM of claim 1 , wherein the UL channel in the SCell is a Physical Random Access Channel (PRACH), and to send the MAC CE to the RAN node over the UL channel in the SCell, execution of the instructions is to cause the UE to:

transmit the MAC CE over preconfigured random access channel (RACH) resources on the SCell.

5. The one or more NTCRM of claim 4 , wherein execution of the instructions is to cause the UE to:

receive a BFR configuration in a BFR Control Resource Set (CORESET) of a Physical Downlink Control Channel (PDCCH) on the SCell that is quasi co-located (QCL'd) with the determined beams, and the BFR configuration is to indicate at least one beam indicated by the MAC CE.

6. The one or more NTCRM of claim 5 , wherein execution of the instructions is to cause the UE to:

monitor a BFR CORESET QCL′d with the determined beams for a PDCCH transmission including the BFR configuration.

7. The one or more NTCRM of claim 1 , wherein execution of the instructions is to further cause the UE to:

transmit a BFR request (BFRQ) to the RAN node over Physical Uplink Control Channel (PUCCH) resources of a dedicated scheduling request (SR) on the PCell; and

receive PCell downlink control information (DCI) in response to the BFRQ.

8. The one or more NTCRM of claim 7 , wherein, the UL channel in the SCell is a PRACH, the DCI to include a BFR PDCCH order-like RACH configuration, and to send the MAC CE to the RAN node over the UL channel in the SCell, execution of the instructions is to cause the UE to:

select at least one RACH occasion during which to transmit the MAC CE based on a set of PRACH association periods indicated by the BFR PDCCH order-like RACH configuration; and

transmit the MAC CE on the PRACH of the SCell during the selected RACH occasion.

9. The one or more NTCRM of claim 8 , wherein, to select the at least one RACH occasion, execution of the instructions is to further cause the UE to:

select the at least one RACH occasion as being a RACH occasion corresponding to a measured synchronization signal block (SSB) that is above a configured measurement threshold.

10. The one or more NTCRM of claim 7 , wherein the UL channel in the SCell is a PUSCH, the DCI is to include a PUSCH UL grant for the SCell, and to send the MAC CE to the RAN node over the UL channel in the SCell, execution of the instructions is to cause the UE to:

repeatedly transmit the MAC CE over PUSCH resources indicated by the PUSCH UL grant.

11. The one or more NTCRM of claim 7 , wherein the UL channel in the SCell is a PUSCH, the DCI is to include a PUSCH UL grant for the SCell, and to send the MAC CE to the RAN node over the UL channel in the SCell, execution of the instructions is to cause the UE to:

select a spatial filter to be used for transmission of the PUSCH, the selected spatial filter different than a spatial filter used for forming a beam of the detected beam failure event; and

transmit the MAC CE over PUSCH resources indicated by the PUSCH UL grant using the selected spatial filter.

12. A modem platform to be employed by a user equipment (UE), the modem platform comprising:

baseband circuitry to:

detect a beam failure in a secondary cell (SCell),

determine candidate beams of the SCell on which to camp based on measurement of corresponding Beam Failure Detection (BFD) reference signals (RSs), wherein the determination of the candidate beams includes:

determine the corresponding of BFD-RSs to measure based on a received BFD configuration,

perform measurement of the corresponding of BFD-RSs, and

determine the candidate beams to be beams associated with the measured BFD-RSs having a signal strength above a configured threshold, and

generate a Beam Failure Recovery (BFR) Medium Access Control (MAC) Control Element (CE) to include reference signal identifiers (IDs) of respective candidate beams whose corresponding BFD-RSs have a signal strength above a configured threshold; and

radiofrequency (RF) circuitry coupled with the baseband circuitry, the RF circuitry to:

transmit the BFR MAC CE to a Radio Access Network (RAN) node over the SCell or a primary cell (PCell) associated with the SCell, and

receive a BFR configuration in a BFR Control Resource Set (CORESET) of a Physical Downlink Control Channel (PDCCH) on the SCell that is quasi co-located (QCL′d) with a candidate beam indicated by the BFR MAC CE, the BFR configuration to include parameters for use of the candidate beam.

13. The modem platform of claim 12 , wherein the RF circuitry is to:

transmit the BFR MAC CE over a Physical Uplink Shared Channel (PUSCH) of the SCell using an available uplink grant.

14. The modem platform of claim 12 , wherein:

the baseband circuitry is to select a Random Access Channel (RACH) occasion during which to transmit the BFR MAC CE based on a set of Physical RACH (PRACH) association periods indicated by a PDCCH ordered RACH configuration; and

the RF circuitry is to transmit the BFR MAC CE over a PRACH of the SCell during the selected RACH occasion.

15. The modem platform of claim 12 , wherein the RF circuitry is to:

receive Downlink Control Information (DCI) over a PCell, the DCI to include an uplink grant for a Physical Uplink Shared Channel (PUSCH) of the SCell; and

transmit the BFR MAC CE over the PUSCH of the SCell according to the uplink grant included in the DCI.