RRC 5G gNB -> UE 3GPP TS 38.331

5G NR - DL Information Transfer MRDC

DL Information Transfer MRDC is the downlink NR RRC container used to deliver MR-DC-related information toward the UE.

Message Fact Sheet

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

Full message name	5G NR - DL Information Transfer MRDC
Protocol	RRC
Technology	5G
Direction	gNB -> UE
Interface	Uu
Signaling bearer / channel	SRB1 / SRB3 / DL-DCCH
Typical trigger	Used when the network needs to deliver MR-DC-related information to the UE over RRC.
Main purpose	Carries MR-DC-related control information in a dedicated downlink RRC wrapper so the UE can apply or forward the received content correctly.
Main specification	3GPP TS 38.331, 6.2.2
Release added	Release 15
Procedures where used	MR-DC Coordination, Dual Connectivity Context Handling

What is DL Information Transfer MRDC in simple terms?

DL Information Transfer MRDC is the downlink NR RRC container used to deliver MR-DC-related information toward the UE.

Carries MR-DC-related control information in a dedicated downlink RRC wrapper so the UE can apply or forward the received content correctly.

Why this message matters

DL Information Transfer MRDC is a dedicated RRC wrapper for downlink MR-DC information.

Where this message appears in the call flow

MR-DC Coordination

Call flow position: Used during MR-DC-related information exchange over dedicated RRC signaling.

Typical state: UE is in connected mode with MR-DC context.

Preconditions:

The UE has an MR-DC-related context.

Next likely message: MR-DC handling or an uplink response

Call flow position

Previous message(s): RRC Reconfiguration

Next message(s): MR-DC handling at the UE, Possible UL Information Transfer MRDC

Message direction and transport

Sender and receiver: gNB -> UE

Interface: Uu

Domain: Access-side radio control in MR-DC context

Signaling bearer: SRB1 / SRB3

Logical channel: DL-DCCH

Transport / encapsulation: Dedicated protected RRC signaling on DCCH

Security context: Sent as protected connected-mode signaling.

Message Structure Overview

The practical value is in the inner MR-DC payload, not the wrapper itself.

ASN.1 for 5G NR - DL Information Transfer MRDC

DLInformationTransferMRDC ::= SEQUENCE {
  dedicatedMRDC-Message OCTET STRING
}

How to read this ASN.1

Engineers mainly inspect the contained MR-DC payload and correlate it with SCG or dual-connectivity behavior.

5G NR - DL Information Transfer MRDC - Example Dump

DL-DCCH-Message
  message: dlInformationTransferMRDC
    dedicatedMRDC-Message: present

How to read this dump

The key check is whether the MR-DC payload is present and aligned with the expected coordination path.

Important Information Elements

IE	Required	Description
`dedicatedMRDC-Message`	Yes	Carries the actual MR-DC-related information in the downlink wrapper.

Detailed field explanation

`dedicatedMRDC-Message`

Carries the actual MR-DC-related information in the downlink wrapper.

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 the presence and size of the dedicated MRDC payload.
Correlate the message with SCG, PSCell, or dual-connectivity state changes.

Common Issues and Troubleshooting

MR-DC behavior is inconsistent with the network command.

Likely cause: The UE may not have received or interpreted the MRDC payload correctly.

What to inspect: Check dedicatedMRDC-Message and correlate with later MR-DC behavior.

Next step: Compare this message with the matching uplink MRDC information transfer or reconfiguration context.

FAQ

What does DL Information Transfer MRDC carry?

It carries MR-DC-related information from the network to the UE inside a dedicated RRC wrapper.

Related message pages

Related Procedures

5G RRC Reconfiguration

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.