Sidelink beam failure recovery

A method of wireless communications by a first sidelink user equipment (UE), comprising:

• periodically transmitting, to a second sidelink UE, a plurality of beam failure recovery (BFR) reference signals across a plurality of transmit beams;
• receiving, from the second sidelink UE, a first indication of a selected beam for communications between the first sidelink UE and the second sidelink UE via a contention free random access (SL-CFRA) resource;
• receiving, from the second sidelink UE, a second indication of the selected beam for communications between the first sidelink UE and the second sidelink UE via a contention based random access (SL-CBRA) resource in response to unsuccessful beam failure recovery with the SL-CFRA resource;
• and
• notifying the second sidelink UE of successful beam failure recovery with a scrambled physical sidelink control channel (PSSCH).

An apparatus for wireless communications at a first sidelink user equipment (UE), comprising:

• at least one processor;
• memory coupled with the at least one processor;
• and
• instructions stored in the memory and operable, when executed by the at least one processor, to cause the apparatus to:
• receive, from a second sidelink UE, a candidate list of reference signals for beam failure recovery with sidelink contention free random access (SL-CFRA);
• measure a plurality of reference signals periodically transmitted by the second sidelink UE using a plurality of receive beams corresponding to the plurality of reference signals in response to a beam failure declared by the first UE, the plurality of reference signals indicated in the candidate list of reference signals;
• receive a scrambled physical sidelink control channel (PSCCH) indicating beam failure recovery success if beam failure recovery is successful;
• and
• initiate beam failure recovery with sidelink contention based random access (SL-CBRA) in response to not receiving the scrambled PSCCH before a beam failure recovery timer expires.

An apparatus for wireless communications at a first sidelink user equipment (UE), comprising:

• at least one processor;
• memory coupled with the at least one processor;
• and
• instructions stored in the memory and operable, when executed by the at least one processor, to cause the apparatus to:
• periodically transmit, to a second sidelink UE, a plurality of beam failure recovery (BFR) reference signals across a plurality of transmit beams;
• receive, from the second sidelink UE, a first indication of a selected beam for communications between the first sidelink UE and the second sidelink UE via a contention free random access (SL-CFRA) resource;
• receive, from the second sidelink UE, a second indication of the selected beam for communications between the first sidelink UE and the second sidelink UE via a contention based random access (SL-CBRA) resource in response to unsuccessful beam failure recovery with the SL-CFRA resource;
• and
• notify the second sidelink UE of successful beam failure recovery with a scrambled physical sidelink control channel (PSCCH).