LTE Timers

This page covers LTE timers which include T300, T301, T303, T304, T305, T310, T311, T320 and T321.

LTE Timers Function at Start/Stop/Expiry
T300 >>Starts at the RRC connection REQ transmit
>>Stops at the Receipt of RRC connection setup or reject message OR at the cell reselection time OR upon abortion of connection establishment by Higher layers (L2/L3).
>>At the expiry performs the actions
T301 >>Starts at the RRC Connection Re-establishment REQUEST
>>Stops at the Receipt of RRC Connection Re-establishment OR
RRC Connection Re-Establishment REJECT message OR
When selected cell becomes unsuitable to continue further
>>At expiry, it Go to RRC_IDLE mode
T303 >>Starts when access is barred while performing RRC CONNECTION ESTABLISHMENT for MO(Mobile Originating) calls
>>Stops while entering RRC_CONNECTED and upon cell re-selection mode
>>At expiry, Informs higher layers about barring alleviation
T304 >>Starts at the Receipt of RRC CONNECTION RECONFIGURATION message along with Mobility Control Info OR at the receipt of mobility from EUTRA command message including CELL CHANGE ORDER
>>Stops at the successful completion of HANDOVER to EUTRA or CELL CHANGE ORDER is met
>>At expiry, it performs action based on need.
1. In the case of CELL CHANGE ORDER from E-UTRA OR intra E-UTRA handover, initiate the RRC connection re-establishment procedure.
2. In case of HANDOVER to E-UTRA, perform the actions defined as per the specifications applicable for the source RAT.
T305 >>starts when access is barred while performing RRC CONNECTION ESTABLISHMENT for MO signaling
>>Stops when entering RRC_CONNECTED and when UE does cell re-selection
>> At expiry, Informs higher layers about barring alleviation
T310 >>Starts when UE detects PHY layer related problems (when it receives N310 consecutive out-of-sync INDs from lower layers)
>>Stops 1. When UE receives N311 consecutive in-sync INDs from lower layers/
2. Upon triggering the HANDOVER procedure
3. Upon initiating the CONNECTION RE-ESTABLISHMENT procedure
>> At expiry, if security is not activated it goes to RRC IDLE else it initiates the CONNECTION RE-ESTABLISHMENT Procedure
T311 >>Starts while initiating RRC CONNECTION RE-ESTABLISHMENT procedure
>>stops upon selection of suitable E-UTRA cell OR a cell using another RAT
>>At expiry it enters RRC IDLE state
T320 >> Starts upon receipt of 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).
>>Stops upon entering RRC_CONNECTED state, when PLMN selection is performed on request by NAS OR upon cell re-selection to another RAT
>> At expiry, it discards the cell re-selection priority info provided by dedicated signaling
T321 >>starts upon receipt of measConfig including a reportConfig with the purpose set to reportCGI
>> Stops at either of following cases:
1. Upon acquiring the information needed to set all fields of globalCellId for the requested cell
2. upon receipt of measConfig that includes removal of the reportConfig with the purpose set to reportCGI
>> At expiry initiates the measurement reporting procedure, stop performing the related measurements and remove the corresponding measID

Other System Timers

Engineers and testers working in multimode or multiRAT modem design consisting of multiple wireless technologies need GSM timers and WCDMA timers other than LTE timers mentioned on this page. Refer following links for the same.

RF and Wireless Terminologies