Timers in LTE

RRC Timers

Timer	Start	Stop	At expiry
T300	Transmission ofRRCConnectionRequest	Reception of RRCConnectionSetup or RRCConnectionRejectmessage, cell re-selection and upon abortion of connection establishment by upper layers	reset MAC, release the MAC configuration and re-establish RLC for all RBs that are established;  inform upper layers about the failure to establish the RRC connection, upon which the procedure ends;
T301	Transmission ofRRCConnectionReestabilshmentRequest	Reception of RRCConnectionReestablishment orRRCConnectionReestablishmentReject message as well as when the selected cell becomes unsuitable	Go to RRC_IDLE
T302	Reception of RRCConnectionReject while performing RRC connection establishment	Upon entering RRC_CONNECTED and upon cell re-selection	if timer T302 expires or is stopped:  inform upper layers about barring alleviation for mobile terminating access; 2> if timer T303 is not running: 3> inform upper layers about barring alleviation for mobile originating calls; 2> if timer T305 is not running: 3> inform upper layers about barring alleviation for mobile originating signalling;
T303	Access barred while performing RRC connection establishment for mobile originating calls	Upon entering RRC_CONNECTED and upon cell re-selection	Inform upper layers
T304	Reception ofRRCConnectionReconfigurationmessage including the MobilityControl Info or reception ofMobilityFromEUTRACommand message including CellChangeOrder	Criterion for successful completion of handover to EUTRA or cell change order is met (the criterion is specified in the target RAT in case of inter-RAT)	In case of cell change order from E-UTRA or intra E-UTRA handover, initiate the RRC connection re-establishment procedure; In case of handover to E-UTRA, perform the actions defined in the specifications applicable for the source RAT.
T305	Access barred while performing RRC connection establishment for mobile originating signalling	Upon entering RRC_CONNECTED and upon cell re-selection	Inform upper layers
T310	Upon detecting physical layer problems i.e. upon receiving N310 consecutive out-of-sync indications from lower layers	Upon receiving N311 consecutive in-sync indications from lower layers, upon triggering the handover procedure and upon initiating the connection re-establishment procedure	If security is not activated: go to RRC_IDLE else: initiate the connection re-establishment procedure
T311	Upon initiating the RRC connection re-establishment procedure	Selection of a suitable E-UTRA cell or a cell using another RAT.	Enter RRC_IDLE
T320	Upon receiving t320 or upon cell (re)selection to E-UTRA from another RAT with validity time configured for dedicated priorities (in which case the remaining validity time is applied).	Upon entering RRC_CONNECTED, when PLMN selection is performed on request by NAS, or upon cell (re)selection to another RAT (in which case the timer is carried on to the other RAT).	Discard the cell reselection priority information provided by dedicated signalling.
T321	Upon receiving measConfig including areportConfig with the purpose set toreportCGI	Upon acquiring the information needed to set all fields ofcellGlobalId for the requested cell, upon receiving measConfigthat includes removal of the reportConfig with the purpose set toreportCGI	Initiate the measurement reporting procedure, stop performing the related measurements and remove the corresponding measId
NAS Timers
T3402	Found in Attach accept and Tracking Area Update Accept
T3412
T3423

RRC Constants:

Constant	Usage
N310	Maximum number of consecutive "out-of-sync" indications received from lower layers. Value in whole number
N311	Maximum number of consecutive "in-sync" indications received from lower layers. Value in whole number

Timer (EPS Mobile Management - UE Side)

Following table comes from 24.301 - 10.2 Timers of EPS mobility management (Table 10.2.1: EPS mobility management timers – UE side)

TIMER NUM.	TIMER VALUE	STATE	CAUSE OF START	NORMAL STOP	ON EXPIRY
T3402	Default 12 min. NOTE 1	EMM DEREGISTERED EMM REGISTERED	At attach failure and the attempt counter is equal to 5. At tracking area updating failure and the attempt counter is equal to 5.	ATTACH REQUEST sent TRACKING AREA UPDATE REQUEST sent	Initiation of the attach procedure or TAU procedure
T3410	15s	EMMREGISTEREDINITIATED	ATTACH REQUEST sent	ATTACH ACCEPT received ATTACH REJECT received	Start T3411 or T3402 as described in subclause 5.5.1.2.6
T3411	10s	EMM DEREGISTERED. ATTEMPTING TO-ATTACH EMM REGISTERED. ATTEMPTING TO-UPDATE	At attach failure due to lower layer failure, T3410 timeout or attach rejected with other EMM cause values than those treated in subclause 5.5.1.2.5. At tracking area updating failure due to lower layer failure, T3430 timeout or TAU rejected with other EMM cause values than those treated in subclause 5.5.3.2.5.	ATTACH REQUEST sent TRACKING AREA UPDATE REQUEST sent	Retransmission of the ATTACH REQUEST or TRACKING AREA UPDATE REQUEST
T3412	Default 54 min. NOTE 2 NOTE 5	EMM REGISTERED	In EMM-REGISTERED, when EMM-CONNECTED mode is left.	When entering state EMM DEREGISTERED or when entering EMM-CONNECTED mode.	Initiation of the periodic TAU procedure
T3416	30s	EMM REGISTERED INITIATED EMM REGISTERED EMM DEREGISTERED INITIATED EMM-TRACKINGAREA UPDATING INITIATED EMM-SERVICE REQUEST INITIATED	RAND and RES stored as a result of a UMTS authentication challenge	SECURITY MODE COMMAND received SERVICE REJECT received TRACKING AREA UPDATE ACCEPT received AUTHENTICATION REJECT received AUTHENTICATION FAILURE sent EMM DEREGISTERED or EMM-NULL entered	Delete the stored RAND and RES
T3417	5s	EMM-SERVICEREQUESTINITIATED	SERVICE REQUEST sent EXTENDED SERVICE REQUEST sent in case f and g in subclause 5.6.1.1	Bearers have been set up SERVICE REJECT received	Abort the procedure
T3417ext	10s	EMM-SERVICEREQUESTINITIATED	EXTENDED SERVICE REQUEST sent in case d in subclause 5.6.1.1 EXTENDED SERVICE REQUEST sent in case e in subclause 5.6.1.1 and the CSFB response was set to "CS fallback accepted by the UE"	Inter-system change from S1 mode to A/Gb mode or Iu mode is completed Inter-system change from S1 mode to A/Gb mode or Iu mode is failed SERVICE REJECT received	Abort the procedure
T3418	20s	EMM REGISTEREDINITIATED EMM REGISTERED EMM-TRACKINGARE AUPDATINGINITIATED EMM DEREGISTEREDINITIATED EMM-SERVICEREQUESTINITIATED	AUTHENTICATION FAILURE (EMM cause = #20 "MAC failure" or #26 "non-EPS authentication unacceptable") sent	AUTHENTICATION REQUEST received	On first expiry, the UE should consider the network as false
T3420	15s	EMM REGISTERED INITIATED EMM REGISTERED EMM DEREGISTERED INITIATED EMM-TRACKINGAREA UPDATING INITIATED EMM-SERVICE REQUEST INITIATED	AUTHENTICATION FAILURE (cause = #21 "synch failure") sent	AUTHENTICATION REQUEST received	On first expiry, the UE should consider the network as false
T3421	15s	EMM DEREGISTERED INITIATED	DETACH REQUEST sent	DETACH ACCEPT received	Retransmission of DETACH REQUEST
T3423	NOTE 3	EMM REGISTERED	T3412 expires while the UE is in EMM-REGISTERED.NO-CELLAVAILABLE and ISR is activated.	When entering state EMM DEREGISTERED or when entering EMM-CONNECTED mode.	Set TIN to "P-TMSI"
T3430	15s	EMM-TRACKING AREA UPDATING INITIATED	TRACKING AREA UPDATE REQUEST sent	TRACKING AREA UPDATE ACCEPT received TRACKING AREA UPDATE REJECT received	Start T3411 or T3402 as described in subclause 5.5.3.2.6
T3440	10s	EMM REGISTERED INITIATED EMM-TRACKING AREA UPDATING INITIATED EMM DEREGISTERED INITIATED EMM-SERVICE REQUEST INITIATED EMM REGISTERED	ATTACH REJECT, DETACH REQUEST, TRACKING AREA UPDATE REJECT with any of the EMM cause #11, #12, #13, #14 or #15 SERVICE REJECT received with any of the EMM cause #11,#12, #13 or #15 TRACKING AREA UPDATE ACCEPT received after the UE sent TRACKING AREA UPDATE REQUEST in EMMIDLE mode with no "active" flag	Signalling connection released Bearers have been set up	Release the signalling connection and proceed as described in subclause 5.3.1.2
T3442	NOTE 4	EMM REGISTERED	SERVICE REJECT received with EMM cause #39 "CS domain temporarily not available"	TRACKING AREA UPDATE REQUEST sent	None
Note 1	The default value of this timer is used if the network does not indicate another value in an EMM signalling procedure.
Note 2	The value of this timer is provided by the network operator during the attach and tracking area updating procedures. (This Timer value is set in Attach Accept message as well).
Note 3	The value of this timer may be provided by the network in the ATTACH ACCEPT message and TRACKING AREA UPDATE ACCEPT message. The default value of this timer is identical to the value of T3412.
Note 4	The value of this timer is provided by the network operator when a service request for CS fallback is rejected by the network with EMM cause #39 "CS domain temporarily not available".
Note 5	The default value of this timer is used if the network does not indicate a value in the TRACKING AREA UPDATE ACCEPT message and the UE does not have a stored value for this timer. (This Timer value is set in Attach Accept message as well).