SCell selection for beam failure recovery
A method for beam failure recovery (BFR) by a user equipment (UE) is disclosed. The method includes receiving, by the UE, an instruction for BFR from a base station, and selecting, by the UE, at least one of a plurality of secondary cells (SCells) to perform BFR based on the instruction. The instruction is contained in a radio resource control (RRC) message, a medium access control (MAC) control element (CE) (MAC-CE), or downlink control information (DCI).
1. A method for beam failure recovery (BFR) by a user equipment (UE), the method comprising: receiving, a medium access control (MAC) control element (CE) from a base station; performing BFR upon at least one of a plurality of selected secondary, cells (SCells) based on the received MAC CE; wherein the MAC CE indicates whether each of the plurality of selected SCells supports BFR based on one or more BFR-related radio resource control (RRC), parameters in an RRC message, and wherein the one or more BFR-related RRC parameters contain at least one of: one or more BFR-candidate-reference signals; a beam-failure-candidate-beam-threshold; and one or more reference signal identifiers (IDs) for failure detection resources (failureDetectionResources).
2. The method of claim 1 , wherein the MAC CE is configured by a base station.
3. The method of claim 1 , wherein:
the MAC CE determines a priority based on an absolute radio frequency channel number (AFRCN) value broadcast by each of the plurality of selected SCells; and
an SCell having a higher ARFCN value has a higher priority over an SCell having a lower ARFCN value to perform BFR.
4. The method of claim 1 , further comprising:
selecting the at least one of the plurality of selected SCells, when an instruction indicates that the one or more BFR-related parameters are configured for the at least one of the plurality of selected SCells.
5. The method of claim 1 , wherein the MAC CE includes at least one of:
a list of SCell identifiers (IDs) corresponding to the plurality of selected SCells; and
the one or more BFR-related parameters.
6. The method of claim 1 , wherein the MAC CE includes a carrier frequency indicator (CFI) information element (IE), and the UE selects the at least one of the plurality of selected SCells based on the CFI IE.
7. The method of claim 1 , wherein the plurality of selected SCells is grouped into at least one subset based on:
an explicit indication in RRC signaling;
an implicit indication based on an order of SCellIDs in an SCellID list;
an absolute radio frequency channel number (AFRCN) value in frequencyInfoDL;
a frequency range (FR); and
a preamble of contention free random access (CFRA) for BFR, the preamble having one or more SCellIDs corresponding to one or more SCells detecting beam failures.
8. The method of claim 7 , wherein when the preamble of CFRA for BFR does not contain any of the one or more SCellIDs, the base station considers all of the at least one subset of the plurality of selected SCells as detecting beam failure.
9. A user equipment (UE) comprising: one or more non-transitory computer-readable media having computer-executable instructions embodied thereon; at least one processor coupled to the one or more non-transitory computer-readable media, and configured to execute the computer-executable instructions to; receive a medium access control (MAC) control element (CE) from a base station; perform beam failure recovery (BFR) upon at least one of a plurality of selected secondary cells (SCells) based on the received MAC CE; wherein the plurality of selected SCells is grouped into at least one subset based on: an explicit indication in radio resource control (RRC) signaling, an implicit indication based on an order of SCellIDs in an SCellID list; an absolute radio frequency channel number (AFRCN) value in frequencyInfoDL; a frequency range (FR); and a preamble of contention free random access (CFRA) for BFR, the preamble having one or more SCellIDs corresponding to one or more SCells detecting beam failures; and wherein when the preamble of CFRA for BFR does not contain any of the one or more SCellIDs, the base station considers all of the at least one subset of the plurality of SCells as detecting beam failure.
10. The UE of claim 9 , wherein:
the MAC CE indicates whether each of the plurality of selected SCells supports BFR based on one or more BFR-related RRC parameters in an RRC message; and
the BFR-related RRC parameter contains at least one of:
one or more BFR-candidate-reference signals;
a beam-failure-candidate-beam-threshold; and
one or more reference signal identifiers (IDs) for failure detection resources (failureDetectionResources).
11. The UE of claim 9 , wherein:
the MAC CE determines a priority based on an absolute radio frequency channel number (AFRCN) value in frequencyInfoDL of each of the plurality of SCells;
an SCell having a higher ARFCN value has a higher priority over an SCell having a lower ARFCN value to perform BFR.
12. The UE of claim 9 , wherein:
the at least one processor is further configured to execute the computer-executable instructions to select the at least one of the plurality of selected SCells, when the MAC CE indicates that one or more BFR-related parameters are configured for the at least one of the plurality of SCells; and
the one or more BFR-related parameters contain at least one of:
one or more BFR-candidate-reference signals;
a beam-failure-candidate-beam-threshold; and
one or more reference signal identifiers (IDs) for failure detection resources (failureDetectionResources).
13. The UE of claim 9 , wherein the MAC CE includes at least one of:
a list of SCell identifiers (IDs) corresponding to the plurality of selected SCells; and
one or more BFR-related parameters.
14. The UE of claim 9 , wherein:
the MAC CE includes a carrier frequency indicator (CFI) information element (IE); and
the UE selects the at least one of the plurality of selected SCells based on the CFI IE.