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5G NRRRCTimersConstants3GPP

5G NR Timers and Constants

WirelessBrew Team
May 20, 2024
6 min read
  • UE Timers
  • UE Counters
  • UE Constants

Below is the list of all the UE Timers and Constants in 5G NR. These descriptions are based on 3GPP TS 38.331.

UE Timers

TimerStartStopAt expiry
T300Upon transmission of RRCSetupRequest.Upon reception of RRCSetup or RRCReject message, cell re-selection and upon abortion of connection establishment by upper layers.Perform the actions as specified in 5.3.3.7.
T301Upon transmission of RRCReestabilshmentRequest.Upon reception of RRCReestablishment or RRCSetup message as well as when the selected cell becomes unsuitable.Go to RRC_IDLE.
T302Upon reception of RRCReject while performing RRC connection establishment or resume, upon reception of RRCRelease with waitTime.Upon entering RRC_CONNECTED or RRC_IDLE, upon cell re-selection and upon reception of RRCReject message.Inform upper layers about barring alleviation as specified in 5.3.14.4.
T304Upon reception of RRCReconfiguration message including reconfigurationWithSync or upon conditional reconfiguration execution.Upon successful completion of random access on the corresponding SpCell. For T304 of SCG, upon SCG release.For T304 of MCG: Initiate RRC re-establishment (Intra-NR) or failure information (DAPS). For T304 of SCG: Initiate SCG failure information procedure.
T310Upon detecting physical layer problems for the SpCell (N310 consecutive out-of-sync indications).Upon receiving N311 consecutive in-sync indications, RRCReconfiguration with reconfigurationWithSync, MobilityFromNRCommand, or upon initiating re-establishment.If in MCG: Go to RRC_IDLE (if no security) or initiate re-establishment/failure information. If in SCG: Initiate SCG failure information procedure.
T311Upon initiating the RRC connection re-establishment procedure.Upon selection of a suitable NR cell or a cell using another RAT.Enter RRC_IDLE.
T312Upon triggering a measurement report for a measurement identity for which T312 is configured, while T310 is running.Upon receiving N311 consecutive in-sync indications, reconfigurationWithSync, MobilityFromNRCommand, or T310 expiry.Initiate connection re-establishment or failure information procedure.
T316Upon transmission of the MCGFailureInformation message.Upon receiving RRCRelease, RRCReconfiguration with reconfigurationwithSync for the PCell, MobilityFromNRCommand, or upon initiating re-establishment.Perform the actions as specified in 5.7.3b.5.
T319Upon transmission of RRCResumeRequest or RRCResumeRequest1.Upon reception of RRCResume, RRCSetup, RRCRelease, RRCReject message or cell re-selection.Perform the actions as specified in 5.3.13.5.
T320Upon reception of t320 or upon cell (re)selection to NR with validity time configured.Upon entering RRC_CONNECTED, RRCRelease, PLMN selection, or cell (re)selection to another RAT.Discard the cell reselection priority information provided by dedicated signalling.
T321Upon receiving measConfig with purpose set to reportCGI.Upon acquiring cgi-info, receiving measConfig removing reportCGI, or detecting cell not broadcasting SIB1.Initiate measurement reporting procedure, stop related measurements.
T322Upon receiving measConfig with purpose set to reportSFTD.Upon acquiring SFTD measurement results or receiving measConfig removing reportSFTD.Initiate measurement reporting procedure, stop related measurements.
T325Upon reception of RRCRelease message with deprioritisationTimer.-Stop deprioritisation of all frequencies or NR signalled by RRCRelease.
T330Upon receiving LoggedMeasurementConfiguration message.Upon log volume exceeding memory or initiating release of LoggedMeasurementConfiguration.Perform the actions specified in 5.5a.1.4.
T331Upon receiving RRCRelease message with measIdleDuration.Upon receiving RRCSetup, RRCResume, RRCRelease with idle/inactive config, or cell re-selection.Perform the actions as specified in 5.7.8.3.
T342Upon transmitting UEAssistanceInformation with DelayBudgetReport.Upon releasing delayBudgetReportingConfig or receiving configuration set to release.No action.
T345Upon transmitting UEAssistanceInformation with overheatingAssistance.Upon releasing overheatingAssistance or receiving configuration set to release.No action.
T346aUpon transmitting UEAssistanceInformation with drx-Preference.Upon releasing drx-PreferenceConfig or receiving configuration set to release.No action.
T346bUpon transmitting UEAssistanceInformation with maxBW-Preference.Upon releasing maxBW-PreferenceConfig or receiving configuration set to release.No action.
T346cUpon transmitting UEAssistanceInformation with maxCC-Preference.Upon releasing maxCC-PreferenceConfig or receiving configuration set to release.No action.
T346dUpon transmitting UEAssistanceInformation with maxMIMO-LayerPreference.Upon releasing maxMIMO-LayerPreferenceConfig or receiving configuration set to release.No action.
T346eUpon transmitting UEAssistanceInformation with minSchedulingOffsetPreference.Upon releasing minSchedulingOffsetPreferenceConfig or receiving configuration set to release.No action.
T346fUpon transmitting UEAssistanceInformation with releasePreference.Upon releasing releasePreferenceConfig or receiving configuration set to release.No action.
T350Upon transmitting DedicatedSIBRequest.Upon acquiring requested SIB(s), releasing onDemandSIB-Request, or RRCRelease.No action.
T380Upon reception of t380 in RRCRelease.Upon reception of RRCResume, RRCSetup or RRCRelease.Perform the actions as specified in 5.3.13.
T390When access attempt is barred at access barring check.Upon cell (re)selection, entering RRC_CONNECTED, reconfigurationWithSync, MobilityFromNRCommand, or RRCRelease.Perform the actions as specified in 5.3.14.4.
T400Upon transmission of RRCReconfigurationSidelink.Upon reception of RRCReconfigurationFailureSidelink or RRCReconfigurationCompleteSidelink.Perform Sidelink radio link failure related actions.

Note: For T346a-e, the UE maintains one instance of this timer per cell group.

UE Counters

CounterResetIncrementedWhen reaching max value
N310Upon reception of "in-sync" indication from lower layers; reconfigurationWithSync; or initiating connection re-establishment.Upon reception of "out-of-sync" from lower layer while T310 is stopped.Start timer T310.
N311Upon reception of "out-of-sync" indication from lower layers; reconfigurationWithSync; or initiating connection re-establishment.Upon reception of "in-sync" from lower layer while T310 is running.Stop timer T310.

UE Constants

ConstantUsage
N310Maximum number of consecutive "out-of-sync" indications for the SpCell received from lower layers.
N311Maximum number of consecutive "in-sync" indications for the SpCell received from lower layers.

Reference: 3GPP TS 38.331

W
Written by

WirelessBrew Team

Technical expert at WirelessBrew, specializing in 5G NR, LTE, and wireless system optimization. Committed to providing accurate, 3GPP-compliant engineering tools.

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