LTE RRC UL Information Transfer IRAT r16

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	Dedicated Transfer / IRAT

Full message name	LTE RRC UL Information Transfer IRAT r16
Protocol	LTE-RRC
Technology	LTE
Direction	UE -> eNodeB
Interface	Uu
Signaling bearer / channel	SRB1 / UL-DCCH
Typical trigger	Triggered when the UE needs to deliver dedicated information associated with an inter-RAT branch.
Main purpose	Carries UE-originated dedicated information for inter-RAT handling so the network can continue the IRAT branch correctly.
Main specification	3GPP TS 36.331, 5.6, 6.2.2
Release added	Release 16
Procedures where used	Inter-RAT dedicated information transfer

What is LTE RRC UL Information Transfer IRAT r16 in simple terms?

Uplink LTE RRC message used to transfer dedicated information in inter-RAT related contexts.

Carries UE-originated dedicated information for inter-RAT handling so the network can continue the IRAT branch correctly.

Why this message matters

UL Information Transfer IRAT r16 is the LTE UE message used to carry dedicated inter-RAT information to the network.

Where this message appears in the call flow

Inter-RAT uplink dedicated information transfer

LTE flow showing UL Information Transfer IRAT r16 carrying dedicated inter-RAT information — The UE sends UL Information Transfer IRAT r16 when an inter-RAT branch needs dedicated UE-originated information.

Call flow position: UE message carrying dedicated information during an inter-RAT branch.

Typical state: The message transports information needed for IRAT handling rather than commanding the mobility step itself.

Preconditions:

An IRAT-related branch is active.

Next likely message: Later IRAT handling or mobility continuation

IRAT container delivery

LTE flow showing UL Information Transfer IRAT r16 used as an inter-RAT container — Read the message as an inter-RAT information container inside a larger mobility or handover branch.

Call flow position: Uplink transfer step used when the UE needs to send inter-RAT specific dedicated content.

Typical state: The message is best read as a wrapper for the dedicated inter-RAT payload.

Preconditions:

The UE has dedicated inter-RAT information to deliver.

Next likely message: Forwarding, processing, or later inter-RAT continuation

Call flow position

Previous message(s): RRCConnectionReconfiguration, Inter-RAT preparation

Next message(s): Network-side IRAT handling

Message direction and transport

Sender and receiver: UE -> eNodeB

Interface: Uu

Domain: Access-side radio control with inter-RAT information transfer

Signaling bearer: SRB1

Logical channel: UL-DCCH

Transport / encapsulation: Protected connected-mode LTE RRC signaling

Security context: Sent as protected connected-mode signaling.

Message Structure Overview

ULInformationTransferIRAT-r16 is an uplink transport wrapper for dedicated inter-RAT information.

ASN.1 for LTE RRC UL Information Transfer IRAT r16

ULInformationTransferIRAT-r16 ::= SEQUENCE {
  criticalExtensions CHOICE {
    c1 CHOICE {
      ulInformationTransferIRAT-r16 ULInformationTransferIRAT-r16-IEs,
      spare3 NULL,
      spare2 NULL,
      spare1 NULL
    },
    criticalExtensionsFuture SEQUENCE {}
  }
}

How to read this ASN.1

Read the message through the dedicated inter-RAT container it carries and the branch around it.

LTE RRC UL Information Transfer IRAT r16 - Example Dump

UL-DCCH-Message
  message c1 : ulInformationTransferIRAT-r16 : {
    criticalExtensions c1 : ulInformationTransferIRAT-r16 : {
      dedicatedInfoType-r16 present
    }
  }

How to read this dump

The main value is the inter-RAT payload and its position in the procedure.

Important Information Elements

IE	Required	Description
`dedicatedInfoType-r16`	Yes	Carries the inter-RAT related dedicated payload type.

Detailed field explanation

`dedicatedInfoType-r16`

Carries the inter-RAT related dedicated payload type.

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

Identify the dedicated payload type.
Check which inter-RAT branch the message belongs to.
Follow the later IRAT handling step.

Common Issues and Troubleshooting

An inter-RAT branch depends on UE-delivered information but the next network step never appears.

Likely cause: The uplink inter-RAT information transfer may be missing, delayed, or carrying unexpected content.

What to inspect: Check whether UL Information Transfer IRAT r16 appears and what payload it carries.

Next step: Treat the issue as dedicated payload transport or interpretation before assuming the mobility command itself failed.

FAQ

What is UL Information Transfer IRAT r16 in LTE?

It is the uplink LTE RRC message the UE uses to transfer dedicated information associated with inter-RAT handling.

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.