Beam Failure Detection: The UE continuously monitors reference signals (SSB or CSI-RS) using L1-RSRP measurements and compares them against configured thresholds. This detection is governed by important RRC parameters like RadioLinkMonitoringConfig and beamFailureDetectionTimer.
Candidate Beam Search: Upon detecting beam failure, the UE scans for alternative beams with better signal quality, using parameters like rsrp-ThresholdSSB to identify suitable candidates.
Recovery Request: The UE transmits a beam failure recovery request via non-contention based PRACH (or PUCCH in Release 16), using resources linked to the selected candidate beam. Critical parameters include ra-PreambleIndex and PRACH-ResourceDedicatedBFR.
Recovery Response: The network processes the request and responds with a RACH Response containing timing advance, uplink grants, and temporary C-RNTI, transmitted in a dedicated search space identified by recoverySearchSpaceId.
