Call drops / RLF: RRC re-establishment, T310/T311 timers, radio problems

RLF Detection Mechanism

Radio Link Failure (RLF) is the most disruptive radio event — the UE completely loses its serving cell connection. The detection process follows a precise 3GPP procedure: the UE physical layer continuously monitors downlink quality based on hypothetical PDCCH BLER. When quality drops below the Qout threshold, out-of-sync (OOS) indications are sent to the RRC layer. After N310 consecutive OOS indications (configurable, typically 1-10), timer T310 starts with configurable values from 0 to 2000 ms. If the UE receives N311 consecutive in-sync indications before T310 expires, the procedure is…