RRC Timers
Below are the timers available in 5G NR RRC:
T300, T301, T302, T304, T311, T319, T320, T321, T325, T380, T390, T3xx
Timer: T300
Start: Upon transmission of RRCSetupRequest.
Stop: Upon reception of RRCSetup or RRCReject message, cell re-selection
Upon Timeout: If security is not activated, then goto idle state.
Timer: T301
Start: Upon transmission of RRCReestabilshmentRequest
Stop: Upon reception of RRCReestablishment or RRCSetupmessage as well as when the selected cell becomes unsuitable
Upon Timeout: Go to RRC_IDLE
Timer: T302
Start: Upon reception of RRCReject while performing RRC connection establishment or resume, upon reception of RRCRelease with waitTime.
Stop: Upon entering RRC_CONNECTED or RRC_IDLE, upon cell re-selection and upon reception of RRCReject message.
Upon Timeout: Inform upper layers about barring alleviation
Timer: T304
Start: Upon reception of RRCReconfiguration message including reconfigurationWithSync
Stop: Upon successful completion of random access on the corresponding SpCell
Upon Timeout: For T304 of MCG, in case of the handover from NR or intra-NR handover, initiate the RRC re-establishment procedure;
Timer: T310
Start: Upon detecting physical layer problems for the SpCell i.e. upon receiving N310 consecutive out-of-sync indications from lower layers.
Stop: Upon receiving N311 consecutive in-sync indications from lower layers for the SpCell,
Upon Timeout:
Timer: T311
Start: Upon initiating the RRC connection re-establishment procedure
Stop: Upon selection of a suitable NR cell or a cell using another RAT.
Upon Timeout: Enter RRC_IDLE
Timer: T319
Start: Upon transmission of RRCResumeRequest or RRCResumeRequest1.
Stop: Upon reception of RRCResume, RRCSetup, RRCRelease, RRCRelease with suspendConfig or RRCReject message,
Upon Timeout:
Counter and Constant
N310: Maximum number of consecutive “out-of-sync” indications for the PCell received from lower layers
N311: Maximum number of consecutive “in-sync” indications for the PCell received from lower layers
Source 3GPP TS 38.331