The full procedure for determining if the link has failed due to being out of sync is shown in the figure below. There are 3 main parameters/timers involved:
n310: This parameter indicates the number of 200 ms intervals when the UE is unable to successfully decode the PDCCH due to low RSRP detected. That is, this parameter indicates the number of times in which the UE cannot successfully decode 20 consecutive frames in the downlink.
t310: It is a timer, in seconds, used to allow the UE to get back in synchronization with the eNodeB.
n311: This parameter indicates the number of 100 ms intervals that the UE must successfully decode the PDCCH to be back in-synch with the eNodeB. That is, this parameter indicates the number of times in which the UE must successfully decode 10 consecutive frames in the downlink in order for the UE to assume the radio link is in-synch.
If the UE detects n310 consecutive out-of-sync indications, it starts the t310 timer. If the timer expires, the link has failed. If the UE detects n311 consecutive in-sync indications prior to the t310 timer expiring, then the timer is stopped and the link has will not fail.
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