5G（NR）网络无线资源控制(RRC)中引入了下列计时器、计数器和常量，以便UE在RRC setuprequest, RRC reestablishment, RRC resume, RRC suspend等进程的可靠运行。

     RRC计时器，指示计时器持续时间及在事件中何时开始和停止；如果计时器超时，UE将采取的行动。这些计时器由字母“T”表示，后跟3位数字，例如 T300。每个计时器起始值为零；UE应用的计时器值倒计数为零时，则计为超时；除非明确说明另有规定。

•      Timer: T300
•      Start Point:（起始点）
•      Upon transmission of RRCSetupRequest
•      Stop Point:（结束点）
•      Upon reception of RRCSetup or RRCReject message
•      Upon Cell re-selection
•      Upon abortion of connection establishment by    upper layers
•      Action upon Timer Expiry:（超时后续动作）
•      Timer: T301
•      Start Point:（起始点）
•      Upon transmission of RRCReestabilshmentRequest
•      Stop Point:（结束点）
•      Upon reception of RRCReestablishment or RRCSetupmessage
•      when the selected cell becomes unsuitable
•      Action upon Timer Expiry:（超时后续动作）
•      Go to RRC-IDLE
•      Timer: T302
•      Start Point:（起始点）
•      Upon reception of RRCReject while    performing RRC connection establishment or resume,
•      Upon reception of RRCRelease with    waitTime
•      Stop Point:（结束点）
•      Upon entering RRC-CONNECTED or RRC-IDLE
•      Upon cell re-selection
•      Upon reception of RRCReject message
•      Action upon Timer Expiry:（超时后续动作）
•      Inform upper layers about barring    alleviation
•      Timer: T304
•      Start Point:（起始点）
•      Upon detecting physical layer problems for    the SpCell i.e. upon receiving N310 consecutive    out-of sync indications from lower layers
•      Stop Point:（结束点）
•      Upon receiving N311 consecutive in-sync indications    from lower layers for the SpCell,
•      Upon receiving RRCReconfiguration with    reconfiguration With Sync for that cell group, and upon initiating the    connection re-establishment procedure.
•      Upon SCG release, if the T310 is    kept in SCG
•      Action upon Timer Expiry:（超时后续动作）
•      If the T310 is kept in MCG: If    security is not activated: go to RRC_IDLE else:    initiate the connection re-establishment procedure
•      If the T310 is kept in SCG,    Inform E-UTRAN/NR about the SCG radio link    failure by initiating the SCG failure information procedure as    specified in 5.7.3 of specification 38.331
•      Timer: T311
•      Start Point:（起始点）
•      Upon initiating the RRC connection reestablishment procedure
•      Stop Point:（结束点）
•      Upon selection of a suitable NR cell    or a cell using another RAT
•      Action upon Timer Expiry:（超时后续动作）
•      Enter RRC_IDLE
•      Timer: T319
•      Start Point:（起始点）
•      Upon transmission of RRCResumeRequest
•      Stop Point:（结束点）
•      Upon reception of RRCResume, RRCSetup,    RRCRelease, RRCRelease with suspendConfig or RRCReject message, cell    re-selection
•      Upon abortion of connection establishment by    upper layers
•      Action upon Timer Expiry:（超时后续动作）
•      Perform the actions as specified in 5.3.13.5 of    3GPP specification 38.331
•      Timer: T320
•      Start Point:（起始点）
•      Upon reception of t320
•      upon cell (re)selection to NR from another    RAT with validity time configured for dedicated priorities (in    which case the remaining validity time is applied)
•      Stop Point:（结束点）
•      Upon entering RRC-CONNECTED,
•      Upon reception of RRC Release,    when PLMN selection is performed on request by NAS
•      Upon cell (re)selection to another RAT (in    which case the timer is carried on to the other RAT)
•      Action upon Timer Expiry:（超时后续动作）
• Discard the cell re-selection priority    information provided by dedicated signalling
•      Timer: T321
•      Start Point:（起始点）
•      Upon receiving measConfig including    a reportConfig with the purpose set to report CGI
•      Stop Point:（结束点）
•      Upon acquiring the information needed to set    all fields of cgiinfo
•      Upon receiving measConfig that    includes removal of the reportConfig with the purpose    set to reportCGI
•      upon detecting that a cell is not    broadcasting SIB1
•      Action upon Timer Expiry:（超时后续动作）
•      Initiate the measurement reporting procedure,    stop performing the related measurements and remove the corresponding measId
•      Timer: T325
•      Start Point:（起始点）
•      Upon reception of RRCRelease message    with deprioritisationTimer
•      Action upon Timer Expiry:（超时后续动作）
•      Stop deprioritisation of all  frequencies or NR signalled by RRCRelease
•      Timer: T380
•      Start Point:（起始点）
•      Upon reception of RRCRelease including suspendConfig
•      Stop Point:（结束点）
•      Upon reception of RRCResume,    RRCSetup or RRCRelease
•      Action upon Timer Expiry:（超时后续动作）
•      Perform the actions as specified in 5.3.13 of    3GPP 38.331
•      Timer: T390
•      Start Point:（起始点）
•      When access attempt is barred at    access barring check for an Access Category
•      The UE shall maintain one instance of this    timer per Access Category
•      Stop Point:（结束点）
•      As specified in 5.3.14.3 of 3GPP 38.331
•      Action upon Timer Expiry:（超时后续动作）
•      Perform the actions as specified in    5.3.14.4 of 3GPP 38.331
•      Timer: T3xx
•      Start Point:（起始点）
•      Upon transmitting UEAssistanceInformation message    with DelayBudgetReport
•      Stop Point:（结束点）
•      Upon initiating the connection re-establishment    procedures
•      Action upon Timer Expiry:（超时后续动作）
•      No action.

RRC常量和计数器：计数与否或针对特定事件尝试。计数器用字母“n”表示，后面跟着3个数字。例如 n310。

•      N310: Maximum number of consecutive “out-of-sync” indications  for the PCell received from lower layers
•      Reset
•      Upon reception of “insync” indication   from lower layers
•      Upon receiving RRCReconfiguration with reconfigurationWithSync for   that cell group
•      Upon initiating the connection reestablishment   procedure
•      Incremented
•      Upon reception of “out-of-sync” from  lower layer while the timer T310 is stopped
•      When reaching max value
•      Start timer T310
•      N311: Maximum number of consecutive “in-sync” indications  for the PCell received from lower layers
•      Reset
•      Upon reception of “outof-sync” indication   from lower layers
•      Upon receiving RRCReconfiguration with reconfigurationWithSync for  that cell group
•      Upon initiating the connection reestablishment   procedure
•      Incremented
•      Upon reception of the “in-sync”from  lower layer while the timer T310 is running
•      When reaching max value
•      Stop the timer T310

原文来自：http://www.techplayon.com/5g-nr-rrc-timers-counters-and-constants/