LTE RRC SCG Failure Information r12

Message Fact Sheet

Protocol	lte-rrc	Network	lte
Spec	3GPP TS 36.331	Spec Section	5.6, 6.2.2
Direction	UE -> eNodeB	Message Type	Failure Reporting

Full message name	LTE RRC SCG Failure Information r12
Protocol	LTE-RRC
Technology	LTE
Direction	UE -> eNodeB
Interface	Uu
Signaling bearer / channel	SRB1 / SRB3 / UL-DCCH
Typical trigger	Triggered when the UE detects failure affecting the secondary cell group.
Main purpose	Lets the network know that SCG handling failed so later recovery, reconfiguration, or release action can be taken.
Main specification	3GPP TS 36.331, 5.6, 6.2.2
Release added	Release 12
Procedures where used	SCG failure reporting, Dual connectivity recovery

What is LTE RRC SCG Failure Information r12 in simple terms?

Uplink LTE RRC message used by the UE to report secondary cell group failure in dual-connectivity related LTE contexts.

Lets the network know that SCG handling failed so later recovery, reconfiguration, or release action can be taken.

Why this message matters

SCG Failure Information r12 tells the LTE network that the secondary cell group has failed.

Where this message appears in the call flow

SCG failure reporting

LTE flow showing SCG Failure Information r12 after secondary cell group failure — When the SCG fails, the UE reports it so the network can move into recovery or reconfiguration handling.

Call flow position: UE failure report sent when the secondary cell group has failed.

Typical state: The report tells the network that the dual-connectivity branch needs recovery, reconfiguration, or release handling.

Preconditions:

An SCG context exists.

Next likely message: Recovery handling or reconfiguration

PSCell or secondary-node failure recovery

LTE flow showing SCG Failure Information r12 before later SCG recovery handling — The message marks the failing secondary branch and helps the network decide whether to recover, reconfigure, or release that part of the connection.

Call flow position: UE report sent as the trigger for investigating or recovering the failing secondary branch.

Typical state: The message helps the network distinguish SCG failure from a broader master-cell issue.

Preconditions:

The UE detected a failure tied to the SCG side of the connection.

Next likely message: Later SCG recovery or release

Call flow position

Previous message(s): RRCConnectionReconfiguration, Dual-connectivity related continuation

Next message(s): Recovery handling, RRCConnectionReconfiguration, RRCConnectionRelease

Message direction and transport

Sender and receiver: UE -> eNodeB

Interface: Uu

Domain: Access-side radio control and failure reporting

Signaling bearer: SRB1 / SRB3

Logical channel: UL-DCCH

Transport / encapsulation: Protected LTE RRC signaling in connected mode

Security context: Sent as protected connected-mode signaling.

Message Structure Overview

SCGFailureInformation-r12 is a UE-originated failure report for the secondary cell group branch.

ASN.1 for LTE RRC SCG Failure Information r12

SCGFailureInformation-r12 ::= SEQUENCE {
  criticalExtensions CHOICE {
    c1 CHOICE {
      scgFailureInformation-r12 SCGFailureInformation-r12-IEs,
      spare3 NULL,
      spare2 NULL,
      spare1 NULL
    },
    criticalExtensionsFuture SEQUENCE {}
  }
}

How to read this ASN.1

The report is mainly useful because it marks the SCG branch as failed and starts recovery handling.

LTE RRC SCG Failure Information r12 - Example Dump

UL-DCCH-Message
  message c1 : scgFailureInformation-r12 : {
    criticalExtensions c1 : scgFailureInformation-r12 : {
      failureType-r12 t310-Expiry
    }
  }

How to read this dump

Start with the failure type and then follow the later recovery branch.

Important Information Elements

IE	Required	Description
`failureType-r12`	Yes	Indicates the SCG-related failure category reported by the UE.

Detailed field explanation

`failureType-r12`

Indicates the SCG-related failure category reported by the UE.

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.

What to check in logs and traces

Check what dual-connectivity or SCG context existed before the failure.
Inspect the reported failure type.
Follow the later recovery, reconfiguration, or release path.

Common Issues and Troubleshooting

The secondary branch disappears or dual connectivity becomes unstable.

Likely cause: The UE may have reported SCG Failure Information r12 after detecting an SCG-side failure.

What to inspect: Check the reported failure type and what recovery action followed.

Next step: Compare SCG failure handling with broader master-cell behavior before assuming a full connection failure.

FAQ

What is SCG Failure Information r12 in LTE?

It is the uplink LTE RRC message the UE uses to report that the secondary cell group failed.

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.