LTE RRC Connection Release | LTE-RRC Message

Message Fact Sheet

Protocol	lte-rrc	Network	lte
Spec	3GPP TS 36.331	Spec Section	5.3.8, 6.2.2
Direction	eNodeB -> UE	Message Type	Connection Release

Full message name	LTE RRC Connection Release
Protocol	LTE-RRC
Technology	LTE
Direction	eNodeB -> UE
Interface	Uu
Signaling bearer / channel	SRB1 / DL-DCCH
Typical trigger	The network decides to release the active LTE RRC connection because the dedicated context is no longer needed or because the UE should be redirected.
Main purpose	Ends the current LTE connected-mode context while optionally providing release redirection or idle-side information that affects what the UE does next.
Main specification	3GPP TS 36.331, 5.3.8, 6.2.2
Release added	Release 8
Procedures where used	RRC Connection Release, Connected-to-idle transition, CS fallback and redirection
Related timers	T320 when release includes redirected carrier priorities

What is LTE RRC Connection Release in simple terms?

Downlink LTE RRC message used to release the connected RRC context and move the UE back toward idle-mode behavior or redirection handling.

Ends the current LTE connected-mode context while optionally providing release redirection or idle-side information that affects what the UE does next.

Why this message matters

RRCConnectionRelease is the LTE network telling the UE that the active connected RRC context is ending, sometimes with instructions about where to go next.

Where this message appears in the call flow

Connected release to idle

LTE call flow showing connected-mode signaling followed by RRCConnectionRelease and return to idle behavior — In the normal release path, RRCConnectionRelease is the last dedicated LTE RRC step before the UE returns to idle-side behavior.

Call flow position: Network command that ends the active LTE connected context and returns the UE toward idle behavior.

Typical state: UE is in RRC_CONNECTED and the dedicated signaling path is being closed.

Preconditions:

The UE already has an active connected LTE RRC context.
The network no longer needs to keep the UE in connected mode.

Next likely message: Idle-mode camping, paging monitoring, or later fresh access

CS fallback and redirection path

LTE call flow showing service trigger, RRCConnectionRelease with redirection, and movement to another system — In redirection-related cases such as CS fallback, the release carries the context that moves the UE away from the current LTE path.

Call flow position: Release message used to redirect the UE away from LTE toward another RAT or carrier.

Typical state: UE is in connected-mode signaling long enough to receive the release and the redirection context.

Preconditions:

The network has decided to move the UE to another system or carrier.
Any preceding paging, service, or voice trigger has already selected the release path.

Next likely message: Target-system acquisition and later access signaling outside the current LTE connected path

Call flow position

Previous message(s): Connected-mode LTE RRC signaling, RRCConnectionReconfiguration in redirection-related paths

Next message(s): Idle-mode cell camping and paging monitoring, Fresh access signaling if service returns later, Inter-RAT redirection behavior in redirected cases

Message direction and transport

Sender and receiver: eNodeB -> UE

Interface: Uu

Domain: Access-side radio control

Signaling bearer: SRB1

Logical channel: DL-DCCH

Transport / encapsulation: RRC over DCCH on SRB1 in connected mode

Security context: Normally sent after LTE AS security activation as protected dedicated signaling before the UE leaves the connected context.

Message Structure Overview

RRCConnectionRelease can be a plain release to idle or a release carrying redirection-related information.
The main practical reading point is not only that the connection ends, but what the UE is expected to do immediately after the release.
redirectedCarrierInfo and idle-side context often explain why later behavior leaves the LTE connected path.

ASN.1 for LTE RRC Connection Release

RRCConnectionRelease ::= SEQUENCE {
  rrc-TransactionIdentifier RRC-TransactionIdentifier,
  criticalExtensions CHOICE {
    c1 CHOICE {
      rrcConnectionRelease-r8 RRCConnectionRelease-r8-IEs,
      spare3 NULL,
      spare2 NULL,
      spare1 NULL
    },
    criticalExtensionsFuture SEQUENCE {}
  }
}

RRCConnectionRelease-r8-IEs ::= SEQUENCE {
  redirectedCarrierInfo        RedirectedCarrierInfo OPTIONAL,
  idleModeMobilityControlInfo  IdleModeMobilityControlInfo OPTIONAL,
  nonCriticalExtension         RRCConnectionRelease-v890-IEs OPTIONAL
}

How to read this ASN.1

The main reading path is to determine whether the release is plain idle return or release with redirection or idle-side mobility context.

LTE RRC Connection Release - Example Dump

DL-DCCH-Message
  message c1 : rrcConnectionRelease : {
    rrc-TransactionIdentifier 4,
    criticalExtensions c1 : rrcConnectionRelease-r8 : {
      redirectedCarrierInfo present
    }
  }

How to read this dump

Check whether redirectedCarrierInfo is present because it changes the next expected UE behavior completely.
If the release is plain, the next useful reading path moves toward idle camping and later paging or fresh setup.
If idleModeMobilityControlInfo is present, read the release together with the expected post-release idle behavior.

Important Information Elements

IE	Required	Description
`rrc-TransactionIdentifier`	Yes	Transaction identifier used to correlate the release procedure.
`redirectedCarrierInfo`	Optional	Redirection information telling the UE which other carrier or RAT to move to after release.
`idleModeMobilityControlInfo`	Optional	Idle-side mobility information that affects how the UE behaves after the release.
`nonCriticalExtension`	Optional	Release-extension branch used for later additions.

Detailed field explanation

`rrc-TransactionIdentifier`

Transaction identifier used to correlate the release procedure.

Presence: Required

In practice: In practice, compare this field with the original request and with any later release-dependent optional fields so you can see whether the network accepted the same service model the UE asked for.

`redirectedCarrierInfo`

Redirection information telling the UE which other carrier or RAT to move to after release.

Presence: Optional

In practice: In practice, compare this field with the original request and with any later release-dependent optional fields so you can see whether the network accepted the same service model the UE asked for.

`idleModeMobilityControlInfo`

Idle-side mobility information that affects how the UE behaves after the release.

Presence: Optional

In practice: In practice, compare this field with the original request and with any later release-dependent optional fields so you can see whether the network accepted the same service model the UE asked for.

`nonCriticalExtension`

Release-extension branch used for later additions.

Presence: Optional

In practice: In practice, compare this field with the original request and with any later release-dependent optional fields so you can see whether the network accepted the same service model the UE asked for.

What to check in logs and traces

Confirm the message appears as the final dedicated downlink control step before the UE leaves connected mode.
Check whether redirectedCarrierInfo is present.
Check whether idleModeMobilityControlInfo is present.
Correlate the release with what the UE does next: idle camping, fresh access, or inter-RAT move.
If the wider issue is service interruption, confirm whether the release itself is expected behavior.

Common Issues and Troubleshooting

The UE leaves LTE connected mode earlier than expected.

Likely cause: The network may have intentionally released the connection, or the wider procedure may have fallen back into a release path.

What to inspect: Check whether the release is plain or includes redirectedCarrierInfo or idle-side mobility context.

Next step: Follow the immediate post-release behavior instead of stopping at the message decode.

Voice or service continuation moves out of LTE after release.

Likely cause: The release may be part of a redirection or CS fallback path rather than an unexpected drop.

What to inspect: Check redirectedCarrierInfo and correlate with the service trigger that happened just before the release.

Next step: Continue into the target-system acquisition path.

The UE returns to idle but does not behave as expected afterward.

Likely cause: Post-release idle behavior may depend on the release context and later idle-mode system information.

What to inspect: Read the release together with idle-side mobility context and the next camping or paging path.

Next step: Move into idle-side broadcast and paging analysis.

LTE / 5G / Variant Comparison

Compared with RRCConnectionReconfiguration

RRCConnectionReconfiguration changes the connected LTE context. RRCConnectionRelease ends it.

Compared with NR RRC Release

LTE and NR both use release messages to end the connected context, but the LTE release path is centered on idle return and redirection handling rather than NR inactive behavior.

FAQ

What is RRCConnectionRelease in LTE?

It is the downlink LTE RRC message the network sends to end the active connected RRC context.

Does RRCConnectionRelease always mean a failure?

No. It can be a normal connected-to-idle transition or a planned redirection path.

What should I inspect first in RRCConnectionRelease?

Start with redirectedCarrierInfo, idle-side mobility context, and the UE action immediately after the release.

Why is RRCConnectionRelease important?

It defines the boundary between connected LTE signaling and the next idle, paging, or redirection behavior.

Related message pages

Related Procedures

Related Tools

Use This Reference in Practice

Decode this message with the 3GPP Decoder, inspect the related message database, or open the matching call flow to see where this signaling step fits in the full procedure.