RFLTE Timers Explained
lte
timer
rrc
protocol
mobile communication
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This page covers LTE timers, including T300, T301, T303, T304, T305, T310, T311, T320, and T321.
LTE Timer Functions
The following table describes the start, stop, and expiry behavior of each timer.
| LTE Timers | Function at Start/Stop/Expiry |
|---|---|
| T300 | Starts: At the RRC connection REQ transmit. Stops: Upon receipt of RRC connection setup or reject message, at cell reselection time, or upon abortion of connection establishment by higher layers (L2/L3). Expiry Action: Performs the actions specified in the standard. |
| T301 | Starts: At the RRC Connection Re-establishment REQUEST. Stops: Upon receipt of RRC Connection Re-establishment OR RRC Connection Re-Establishment REJECT message OR when the selected cell becomes unsuitable to continue further. Expiry Action: Goes to RRC_IDLE mode. |
| T303 | Starts: When access is barred while performing RRC CONNECTION ESTABLISHMENT for MO (Mobile Originating) calls. Stops: Upon entering RRC_CONNECTED and upon cell re-selection mode. Expiry Action: Informs higher layers about barring alleviation. |
| T304 | Starts: Upon receipt of RRC CONNECTION RECONFIGURATION message along with Mobility Control Info OR upon receipt of mobility from EUTRA command message including CELL CHANGE ORDER. Stops: Upon successful completion of HANDOVER to EUTRA or CELL CHANGE ORDER is met. Expiry Action: Action depends on the scenario: 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: Upon entering RRC_CONNECTED and when UE does cell re-selection. Expiry Action: 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. Expiry Action: If security is not activated, it goes to RRC IDLE; otherwise, it initiates the CONNECTION RE-ESTABLISHMENT Procedure. |
| T311 | Starts: While initiating the RRC CONNECTION RE-ESTABLISHMENT procedure. Stops: Upon selection of a suitable E-UTRA cell OR a cell using another RAT. Expiry Action: 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. Expiry Action: 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: 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. Expiry Action: Initiates the measurement reporting procedure, stop performing the related measurements, and remove the corresponding measID. |
