5G NR - UL Information Transfer IRAT

Message Fact Sheet

Protocol	rrc	Network	5g
Spec	3GPP TS 38.331	Spec Section	6.2.2
Direction	UE -> gNB	Message Type	IRAT Information Transfer

Full message name	5G NR - UL Information Transfer IRAT
Protocol	RRC
Technology	5G
Direction	UE -> gNB
Interface	Uu
Signaling bearer / channel	SRB1 / UL-DCCH
Typical trigger	Used when the UE needs to transfer inter-RAT-related information to the network.
Main purpose	Lets the UE send inter-RAT-related information through a dedicated RRC container when the wider procedure needs it.
Main specification	3GPP TS 38.331, 6.2.2
Release added	Release 16
Procedures where used	Inter-RAT Information Transfer, Mobility Support

What is UL Information Transfer IRAT in simple terms?

UL Information Transfer IRAT is the UE-to-network NR RRC wrapper used to carry inter-RAT related information in the uplink direction.

Lets the UE send inter-RAT-related information through a dedicated RRC container when the wider procedure needs it.

Why this message matters

UL Information Transfer IRAT is an uplink RRC wrapper for inter-RAT information.

Where this message appears in the call flow

Inter-RAT Information Transfer

Call flow position: Sent when the UE transfers inter-RAT-related information in the uplink.

Typical state: UE is in connected mode during an inter-RAT-related workflow.

Preconditions:

An inter-RAT-related context exists.

Next likely message: Network-side inter-RAT handling

Call flow position

Previous message(s): Mobility From NR Command, RRC Reconfiguration

Next message(s): Inter-RAT handling at the network

Message direction and transport

Sender and receiver: UE -> gNB

Interface: Uu

Domain: Access-side radio control with inter-RAT context

Signaling bearer: SRB1

Logical channel: UL-DCCH

Transport / encapsulation: Dedicated protected RRC signaling

Security context: Sent as protected connected-mode signaling.

Message Structure Overview

The real value is the inner IRAT payload, not the wrapper itself.

ASN.1 for 5G NR - UL Information Transfer IRAT

ULInformationTransferIRAT ::= SEQUENCE {
  dedicatedIRAT-Message OCTET STRING
}

How to read this ASN.1

Engineers use the message to follow inter-RAT side information rather than standard NAS transfer.

5G NR - UL Information Transfer IRAT - Example Dump

UL-DCCH-Message
  message: ulInformationTransferIRAT
    dedicatedIRAT-Message: present

How to read this dump

Correlate the payload with the inter-RAT workflow under test.

Important Information Elements

IE	Required	Description
`dedicatedIRAT-Message`	Yes	Carries the actual inter-RAT-related content.

Detailed field explanation

`dedicatedIRAT-Message`

Carries the actual inter-RAT-related content.

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 whether the UE actually sent the expected inter-RAT payload.

Common Issues and Troubleshooting

The network does not behave as expected in an inter-RAT workflow.

Likely cause: The UE may not have sent the required IRAT-related information.

What to inspect: Check this message and correlate it with the surrounding mobility flow.

Next step: Compare it with the relevant command or target-system behavior.

FAQ

What does UL Information Transfer IRAT carry?

It carries UE-to-network inter-RAT-related information inside a dedicated RRC wrapper.

Related message pages

Related Procedures

5G Inter-RAT Handover

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.