LTE RRC Timers
This page is a practical LTE RRC timer reference based on 3GPP TS 36.331. It brings together the timers that matter most in live LTE RRC traces, especially for connection setup, re-establishment, handover, radio link failure, and redirected-priority behavior.
Use this page by starting with the active RRC procedure, then checking whether the timer explains the UE behavior. In practice, timers such as T300, T304, T310, T311, and T320 are most useful when you need to explain setup delay, mobility timeout, recovery failure, or retained priority behavior in LTE traces.
Quick facts
| Technology | LTE / E-UTRA |
|---|---|
| Protocol scope | LTE RRC timers used in setup, re-establishment, mobility, release, and radio link failure handling |
| Main spec | 3GPP TS 36.331 |
| Main timer clause | Clause 7.2 with procedure use across connection control and mobility clauses |
| Main use | Connection establishment, re-establishment, handover timing, failure detection, and redirected-priority validity |
Overview
LTE RRC timers do not all do the same job. Some supervise a live connection-control exchange such as setup or re-establishment. Others define how long the UE can keep trying a mobility or recovery branch. A few shape what happens after release, especially when redirected or dedicated priorities stay valid for later idle behavior.
This page groups the timers by how they show up in real traces. Use it as the common reference whenever an LTE RRC message page lists a related timer such as T300, T304, T310, T311, or T320.
Quick lookup
| Timer | Main procedure context | What it changes in practice | Typical message pages |
|---|---|---|---|
| T300 | RRC connection establishment supervision | Supervises the connection-establishment branch after the UE sends RRCConnectionRequest and waits for setup or reject outcome. | LTE Connection Request, LTE Connection Setup, LTE Connection Setup Complete |
| T301 | RRC re-establishment supervision | Supervises the re-establishment branch after the UE sends RRCConnectionReestablishmentRequest and waits for the network response. | LTE Connection Reestablishment Request, LTE Connection Reestablishment |
| T302 | Connection retry wait after reject | Controls how long the UE should wait before retrying a fresh RRC connection attempt after reject handling. | LTE Connection Reject, LTE Connection Request |
| T304 | Handover and inter-RAT mobility execution | Supervises the execution window after the UE receives a handover-related command such as mobilityControlInfo or MobilityFromEUTRACommand. | LTE Connection Reconfiguration, LTE Connection Reconfiguration Complete, LTE Mobility From EUTRA Command |
| T305 | Delay before new access after selected release or mobility fallback handling | Used in LTE connection-control wait handling where the UE is expected to hold off before another access attempt. | LTE Connection Reject, LTE Connection Release |
| T310 | Radio link failure detection | Starts when lower-layer out-of-sync conditions cross the configured threshold and supervises whether the radio link failure branch should be entered. | LTE Connection Reestablishment Request, LTE Connection Reestablishment, LTE RRC States |
| T311 | Re-establishment search window after radio link failure | Defines how long the UE may stay in the post-failure recovery window before giving up on re-establishment and falling back further. | LTE Connection Reestablishment Request, LTE Connection Reestablishment Reject, LTE RRC States |
| T320 | Dedicated-priority validity after release or inter-RAT return | Controls how long redirected or dedicated reselection priorities remain valid after the network provides them. | LTE Connection Release, LTE RRC States, LTE System Information |
Connection setup and access
T300
Release 8Main procedure context: RRC connection establishment supervision
What it changes in practice: Supervises the connection-establishment branch after the UE sends RRCConnectionRequest and waits for setup or reject outcome.
Where you will usually see it: Most visible in LTE Connection Request and LTE Connection Setup.
3GPP Specification: 3GPP TS 36.331
Accepted values
- Configured through ue-TimersAndConstants.
- Allowed values are ms100, ms200, ms300, ms400, ms600, ms1000, ms1500, and ms2000.
- Use it to read whether setup waiting time was normal or whether the UE should have moved into failure handling.
Typical message pages
T301
Release 8Main procedure context: RRC re-establishment supervision
What it changes in practice: Supervises the re-establishment branch after the UE sends RRCConnectionReestablishmentRequest and waits for the network response.
Where you will usually see it: Most useful with LTE Connection Reestablishment Request and LTE Connection Reestablishment.
3GPP Specification: 3GPP TS 36.331
Accepted values
- Configured through ue-TimersAndConstants.
- Allowed values are ms100, ms200, ms300, ms400, ms600, ms1000, ms1500, and ms2000.
- Use it when the UE starts recovery but the network answer arrives too late or never arrives.
Typical message pages
T302
Release 8Main procedure context: Connection retry wait after reject
What it changes in practice: Controls how long the UE should wait before retrying a fresh RRC connection attempt after reject handling.
Where you will usually see it: Most visible in LTE Connection Reject and later fresh access retry behavior.
3GPP Specification: 3GPP TS 36.331
Accepted values
- Started from the reject-side wait-time information returned by the network.
- The exact accepted value comes from the waitTime or later extension field carried in the reject message rather than from ue-TimersAndConstants.
- Use it to explain why the UE stays quiet after a reject instead of retrying immediately.
Typical message pages
Mobility and recovery
T304
Release 8Main procedure context: Handover and inter-RAT mobility execution
What it changes in practice: Supervises the execution window after the UE receives a handover-related command such as mobilityControlInfo or MobilityFromEUTRACommand.
Where you will usually see it: Most visible in LTE Connection Reconfiguration, LTE Connection Reconfiguration Complete, and LTE Mobility From EUTRA Command.
3GPP Specification: 3GPP TS 36.331
Accepted values
- Configured by the handover or mobility command, not by ue-TimersAndConstants.
- The exact allowed set depends on the branch. Cell-change-order branches include values such as ms100, ms200, ms500, ms1000, ms2000, ms4000, ms8000, and ms10000.
- Use it to explain whether a mobility command timed out before the UE could reach the target side successfully.
T305
Release 8Main procedure context: Delay before new access after selected release or mobility fallback handling
What it changes in practice: Used in LTE connection-control wait handling where the UE is expected to hold off before another access attempt.
Where you will usually see it: Most useful when reading reject, fallback, or delayed re-access behavior around connection control.
3GPP Specification: 3GPP TS 36.331
Accepted values
- This is procedure-controlled wait handling defined by TS 36.331 connection-control behavior.
- Use the exact message context to determine whether the timer was started from a returned delay or from a procedure branch.
- In traces, it mainly explains why the UE does not come back with fresh access immediately.
Typical message pages
T310
Release 8Main procedure context: Radio link failure detection
What it changes in practice: Starts when lower-layer out-of-sync conditions cross the configured threshold and supervises whether the radio link failure branch should be entered.
Where you will usually see it: Most useful with radio link failure, re-establishment request, and recovery analysis.
3GPP Specification: 3GPP TS 36.331
Accepted values
- Configured through ue-TimersAndConstants.
- Allowed values are ms0, ms50, ms100, ms200, ms500, ms1000, and ms2000.
- Read it together with N310 because the failure branch begins only after the lower-layer threshold condition has already been met.
Typical message pages
T311
Release 8Main procedure context: Re-establishment search window after radio link failure
What it changes in practice: Defines how long the UE may stay in the post-failure recovery window before giving up on re-establishment and falling back further.
Where you will usually see it: Most useful with LTE Connection Reestablishment Request, reject handling, and failure-to-recover cases.
3GPP Specification: 3GPP TS 36.331
Accepted values
- Configured through ue-TimersAndConstants.
- Allowed values are ms1000, ms3000, ms5000, ms10000, ms15000, ms20000, and ms30000.
- Use it to explain how long the UE can keep trying recovery before it abandons the broken connected branch.
Priority persistence
T320
Release 8Main procedure context: Dedicated-priority validity after release or inter-RAT return
What it changes in practice: Controls how long redirected or dedicated reselection priorities remain valid after the network provides them.
Where you will usually see it: Most visible in LTE Connection Release and later idle-mode priority behavior.
3GPP Specification: 3GPP TS 36.331
Accepted values
- Configured from redirected-priority or dedicated-priority context carried by the network.
- Allowed values are min5, min10, min20, min30, min60, min120, and min180.
- Use it when the UE keeps honoring earlier dedicated priorities longer than expected after release or inter-RAT return.
Typical message pages
Where to use this page
Use this page as the common lookup target whenever an LTE RRC message lists Related timers. For example, LTE Connection Request and LTE Connection Setup point naturally to T300, while LTE Connection Reconfiguration and LTE Mobility From EUTRA Command point to T304.
The same approach works for failure analysis. Read radio link failure and recovery together with T310 and T311, and read redirected or dedicated priority persistence together with T320.
References
- ETSI TS 136 331 V18.7.0 / 3GPP TS 36.331 Release 18
- Timer definitions and procedure behavior are read from the Release 18 LTE RRC baseline, especially clause 7.2 and the connection-control and mobility procedures that use each timer.