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LTE RRC Connection Release Procedure Call Flow

call-flowLTE | E-UTRAN | RRC

LTE RRC Connection Release is the procedure that ends the active connected radio-control path and returns the UE toward idle-mode behavior. It is centered on RRC Connection Release.

This is the branch that closes connected signaling after data inactivity, service completion, or other release conditions, and it sets up the later idle and paging behavior.

Introduction

The LTE RRC Connection Release procedure moves the UE out of active connected signaling. It does not necessarily mean that EPS registration is removed. In many cases, the UE stays registered and simply returns to idle reachability.

The main nodes are the UE and eNB. The later impact is visible in LTE Paging Procedure and LTE Service Request Procedure.

What Is LTE RRC Connection Release in Simple Terms?

What starts the procedure: The active radio connection no longer needs to stay open.
What the UE and network want to achieve: Close the connected radio path and return the UE to idle monitoring.
What success looks like: The eNB sends RRC Connection Release and the UE returns to idle behavior cleanly.
What failure means: The UE drops unexpectedly, re-enters signaling immediately, or the release timing does not match the scenario.

Why this procedure matters

This branch explains when a UE should move from connected signaling back into idle reachability and when the next expected procedure becomes paging or service request instead of continuous connected activity.

Quick Fact Sheet

Procedure name	LTE RRC Connection Release Procedure
Domain	Connected-to-idle radio transition
Main trigger	Service completion, inactivity, or release decision by the network
Start state	UE is in RRC_CONNECTED
End state	UE moves toward RRC_IDLE
Main nodes	UE, eNB
Main protocols	RRC
Main success outcome	Connected signaling closes cleanly and idle behavior starts
Main failure outcome	Unexpected reconnect loop or unstable connected-to-idle transition
Most important messages	RRC Connection Release
Main specs	TS 36.331, TS 36.300

LTE RRC Connection Release call flow across UE and eNB — Click the diagram to open the full-size in a new tab.

Preconditions

The UE already has an active connected radio context.
The network decides that the connected path no longer needs to stay open.
No immediate higher-priority signaling need blocks release.

Nodes and Interfaces

Nodes involved

Node	Role in this procedure
UE	Receives the release and returns to idle behavior.
eNB	Triggers the release when connected signaling should close.

Interfaces used

Interface or channel context	Path	Why it matters here
LTE Uu	UE <-> eNB	Carries the release signaling.
DCCH	UE <-> eNB	The release is sent while the UE is still connected.

End-to-End Call Flow

UE                          eNB
|                            |
|<- RRC Connection Release --|
|                            |
|   UE returns to idle mode  |
|                            |
|   later page or service request may follow |

Major Phases

Phase	What happens
1. Release decision	The network decides the connected path can close.
2. Release delivery	The UE receives RRC Connection Release.
3. Idle return	The UE leaves connected behavior and starts idle monitoring.

Step-by-Step Breakdown

Step 1: RRC Connection Release

Sender -> receiver: eNB -> UE

Message(s): RRC Connection Release

Purpose: End the active radio-control path.

State or context change: The UE leaves connected-mode signaling and returns to idle behavior.

Note: EPS registration may still remain valid after release.

Important Messages in This Flow

Message	Protocol	Direction	Purpose in this procedure	What to inspect briefly
RRC Connection Release	RRC	eNB -> UE	Closes the connected radio path.	Release timing and whether the next expected state is idle reachability.

Important Parameters to Inspect

Parameter	What it is	Where it appears	Why it matters	Common issues
Release timing	The point at which the connected branch is closed.	RRC Connection Release	Shows whether inactivity or service completion matches the release.	Unexpected early release.
Later idle continuity	The next behavior after release.	After release	Explains whether paging or service return should be expected later.	Immediate reconnect loop.

Successful Completion

Success means the UE returns cleanly to idle-mode monitoring and the next expected behavior is consistent with idle reachability, paging, or later service request.

Common Failures and Troubleshooting

Symptom	Likely cause	Where to inspect	Relevant message(s)	Relevant interface(s)	Likely next step
Immediate reconnect after release	A new trigger appeared right after release or the release timing is wrong for the scenario.	Events immediately before and after release.	RRC Connection Release	LTE Uu	Check whether paging or uplink trigger restarted access.
UE behavior does not match idle expectation	Release did not complete cleanly or the trace is missing the next branch.	Post-release radio behavior.	RRC Connection Release	LTE Uu	Check later paging or fresh setup behavior.

What to Check in Logs and Traces

Confirm the UE was previously in connected mode.
Check whether the release timing matches inactivity or service completion.
Use the next branch after release to confirm idle return.

Related sub-procedures

Related message reference pages

RRC Connection Release

Related troubleshooting pages

Notes

RRC Connection Release does not automatically mean detach. The UE may remain registered and only return to idle reachability.

FAQ

What is LTE RRC Connection Release?

It is the RRC procedure that ends the active connected radio path and returns the UE toward idle mode.

What usually comes after release?

Paging, service request, or continued idle monitoring may follow depending on the scenario.