RRC 5G gNB -> UE 3GPP TS 38.331

5G NR - RRC Resume

RRC Resume is the downlink NR RRC message used by the network to resume a suspended or inactive context after a valid resume request.

Message Fact Sheet

Protocol	rrc	Network	5g
Spec	3GPP TS 38.331	Spec Section	5.3.13, 6.2.2
Direction	gNB -> UE	Message Type	Connection Resume

Full message name	5G NR - RRC Resume
Protocol	RRC
Technology	5G
Direction	gNB -> UE
Interface	Uu
Signaling bearer / channel	SRB1 / DL-DCCH
Typical trigger	Used when the network accepts an RRC Resume Request and restores the UE's context.
Main purpose	Restores the UE's connected-mode context from an inactive or suspended state so protected signaling and data transfer can continue.
Main specification	3GPP TS 38.331, 5.3.13, 6.2.2
Release added	Release 15
Procedures where used	RRC Resume, Inactive-to-Connected Transition
Related timers	T380
Related cause values	None highlighted

What is RRC Resume in simple terms?

RRC Resume is the downlink NR RRC message used by the network to resume a suspended or inactive context after a valid resume request.

Restores the UE's connected-mode context from an inactive or suspended state so protected signaling and data transfer can continue.

Why this message matters

RRC Resume is the network's message for restoring an inactive or suspended RRC context.

Where this message appears in the call flow

RRC Resume

Call flow position: Sent after the network accepts the resume attempt.

Typical state: UE is recovering from RRC_INACTIVE or suspended context.

Preconditions:

The UE sent a valid resume request.

Next likely message: RRC Resume Complete

Call flow position

Previous message(s): RRC Resume Request, RRC Resume Request1

Next message(s): RRC Resume Complete

Message direction and transport

Sender and receiver: gNB -> UE

Interface: Uu

Domain: Access-side radio control

Signaling bearer: SRB1

Logical channel: DL-DCCH

Transport / encapsulation: Dedicated protected RRC signaling

Security context: Sent when resuming an existing suspended or inactive context.

Message Structure Overview

RRC Resume restores an earlier context rather than building a new one from zero.

ASN.1 for 5G NR - RRC Resume

RRCResume ::= SEQUENCE {
  criticalExtensions CHOICE {
    rrcResume RRCResume-IEs,
    ...
  }
}

How to read this ASN.1

The important practical question is what context was restored and whether the UE accepted it.

Decoded Message Dump

DL-DCCH-Message
  message: rrcResume
    radioBearerConfig: present

How to read this dump

If this message appears, the network accepted the resume path.

Important Information Elements

IE	Required	Description
`radioBearerConfig`	Optional	Restored or updated bearer configuration used during resume.
`masterCellGroup`	Optional	Cell-group information the UE applies when resuming the connected context.

Detailed field explanation

`radioBearerConfig`

Restored or updated bearer configuration used during resume.

Presence: Optional

`masterCellGroup`

Cell-group information the UE applies when resuming the connected context.

Presence: Optional

What to check in logs and traces

Check which resume request triggered it.
Correlate the restored context with the later resume complete.

Common Issues and Troubleshooting

The UE tries to resume but service does not recover.

Likely cause: The restored context may not match the UE's inactive state.

What to inspect: Check the resume payload and the later complete or failure path.

Next step: Follow the exact state transition after the resume command.

Detailed explanation

5G NR - RRC Resume Explained

RRC Resume is a 5G NR RRC message reference page for engineers who need to understand what the message carries, where it fits in the procedure, and what to inspect in traces when behavior does not match expectation.

RRC Resume is the downlink NR RRC message used by the network to resume a suspended or inactive context after a valid resume request. Restores the UE’s connected-mode context from an inactive or suspended state so protected signaling and data transfer can continue.

What is RRC Resume in simple terms?

RRC Resume is the downlink NR RRC message the network sends to the UE when this specific procedure step needs to be controlled, configured, or completed.

Restores the UE’s connected-mode context from an inactive or suspended state so protected signaling and data transfer can continue.

Why this message matters

it directly affects RRC Resume, Inactive-to-Connected Transition
The UE tries to resume but service does not recover
Used when the network accepts an RRC Resume Request and restores the UE’s context

Where this message appears in the call flow

RRC Resume is typically seen during RRC Resume. Engineers usually read it together with the messages just before and just after it so they can tell whether the procedure is progressing normally or drifting into a fallback or failure path.

The UE is usually in recovering from RRC_INACTIVE or suspended context when engineers evaluate this message in traces. In the main procedure context, it appears sent after the network accepts the resume attempt. Before this message appears, the important preconditions are The UE sent a valid resume request..

Simplified sequence:

UE                       gNB / Network
|                        |
|--- RRC Resume Request ----------->|
|<-- RRC Resume -----------|
|--- RRC Resume Complete ----------->|

Message direction and transport

sender: gNB
receiver: UE
interface: Uu
signaling bearer: SRB1
signaling channel: DL-DCCH
transport type: Dedicated protected RRC signaling
domain: Access-side radio control
security context: Sent when resuming an existing suspended or inactive context.

Important Information Elements

IE	Why it matters
`radioBearerConfig`	Restored or updated bearer configuration used during resume.
`masterCellGroup`	Cell-group information the UE applies when resuming the connected context.

Example message dump

DL-DCCH-Message
  message: rrcResume
    radioBearerConfig: present

How to read this dump

If this message appears, the network accepted the resume path.

FAQ

What happens after RRC Resume?

The UE normally answers with RRC Resume Complete if the resume succeeds.

Summary

RRC Resume is the downlink NR RRC message used by the network to resume a suspended or inactive context after a valid resume request.

Advanced Engineer Notes

Resume failures often come from state mismatch rather than simple radio delivery problems.

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.