5G NR - UE Capability Information

Message Fact Sheet

Protocol	rrc	Network	5g
Spec	3GPP TS 38.331	Spec Section	5.6.1, 6.2.2, Annex B.1
Direction	UE -> gNB	Message Type	Capability Exchange

Full message name	5G NR - UE Capability Information
Protocol	RRC
Technology	5G
Direction	UE -> gNB
Interface	Uu
Signaling bearer / channel	SRB1 / UL-DCCH
Typical trigger	The UE responds to UECapabilityEnquiry by returning the requested capability containers.
Main purpose	Transfers UE radio capability information so the network can build configuration that matches the UE's supported NR features.
Main specification	3GPP TS 38.331, 5.6.1, 6.2.2, Annex B.1
Release added	Release 15
Procedures where used	UE Capability Transfer, Connected-Mode Capability Discovery, Capability-Aware RRC Reconfiguration

What is UE Capability Information in simple terms?

Uplink NR RRC message used by the UE to report its supported radio capability containers to the gNB.

Transfers UE radio capability information so the network can build configuration that matches the UE's supported NR features.

Why this message matters

UECapabilityInformation is the UE's answer to the network's capability request. It tells the gNB what radio features the UE supports.

Where this message appears in the call flow

UE Capability Transfer

Call flow position: UE response that carries the requested capability containers back to the gNB.

Typical state: UE is in RRC_CONNECTED and able to return capability information on protected DCCH signaling.

Preconditions:

The gNB sent UECapabilityEnquiry.
The UE can assemble the requested capability information.

Next likely message: Capability-dependent RRCReconfiguration or another network decision based on the reported support

Capability-Aware RRC Reconfiguration

Call flow position: Capability report that the network uses before applying feature-dependent radio configuration.

Typical state: UE is connected and the network is validating supported features before changing configuration.

Preconditions:

The network requested the relevant RAT capability containers.

Next likely message: RRCReconfiguration

Call flow position

Previous message(s): UECapabilityEnquiry

Next message(s): RRCReconfiguration, Capability-aware connected-mode network decision

Message direction and transport

Sender and receiver: UE -> gNB

Interface: Uu

Domain: Access-side radio control capability reporting

Signaling bearer: SRB1

Logical channel: UL-DCCH

Transport / encapsulation: RRC over DCCH on SRB1 during connected-mode capability exchange

Security context: Typically exchanged after AS security is active, so it is usually carried as protected connected-mode RRC signaling.

Message Structure Overview

UECapabilityInformation is the payload-heavy half of the capability exchange because it carries the actual reported capability containers.
The key engineering task is to identify which RAT containers are present and whether the reported support matches the later network configuration.
This message should always be interpreted together with the earlier UECapabilityEnquiry and the later capability-dependent RRC behavior.

ASN.1 for 5G NR - UE Capability Information

UECapabilityInformation ::= SEQUENCE {
  rrc-TransactionIdentifier RRC-TransactionIdentifier,
  criticalExtensions CHOICE {
    ueCapabilityInformation UECapabilityInformation-IEs,
    criticalExtensionsFuture SEQUENCE {}
  }
}

UECapabilityInformation-IEs ::= SEQUENCE {
  ue-CapabilityRAT-ContainerList UE-CapabilityRAT-ContainerList,
  lateNonCriticalExtension       OCTET STRING OPTIONAL,
  nonCriticalExtension           SEQUENCE {} OPTIONAL
}

How to read this ASN.1

Most of the practical value is inside the returned RAT capability containers. Engineers should inspect what RAT capability blocks are present and whether the network later interprets them correctly.

5G NR - UE Capability Information - Example Dump

UL-DCCH-Message
  message: ueCapabilityInformation
    rrc-TransactionIdentifier: 3
    criticalExtensions:
      ueCapabilityInformation:
        ue-CapabilityRAT-ContainerList:
          - rat-Type: nr
            ueCapabilityRAT-Container: <NR UE Capability container>
        lateNonCriticalExtension: absent
        nonCriticalExtension: absent

How to read this dump

The important part is the returned RAT capability container list.
In practical traces, the NR capability container can be large and deeply structured.
If later configuration fails, compare the network decision against what the UE actually reported here.

Important Information Elements

IE	Required	Description
`rrc-TransactionIdentifier`	Yes	Transaction identifier used to correlate the UE response with the preceding UECapabilityEnquiry.
`ue-CapabilityRAT-ContainerList`	Yes	List of UE capability containers reported by the UE for the requested RATs.
`lateNonCriticalExtension`	Optional	Extension container used for later release evolution and compatibility handling.
`nonCriticalExtension`	Optional	Forward-compatible extension branch for later additions.

Detailed field explanation

`rrc-TransactionIdentifier`

Transaction identifier used to correlate the UE response with the preceding UECapabilityEnquiry.

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.

`ue-CapabilityRAT-ContainerList`

List of UE capability containers reported by the UE for the requested RATs.

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.

`lateNonCriticalExtension`

Extension container used for later release evolution and compatibility handling.

Presence: Optional

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.

`nonCriticalExtension`

Forward-compatible extension branch for later additions.

Presence: Optional

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

Confirm the message follows UECapabilityEnquiry and uses SRB1 / UL-DCCH.
Verify the transaction identifier matches the preceding enquiry.
Inspect which RAT capability containers are present.
Check whether the reported capability content is complete and consistent with the scenario.
Correlate the message with the following RRCReconfiguration or other network action.

Common Issues and Troubleshooting

UECapabilityInformation is present but later feature configuration fails.

Likely cause: The network may have misread or misused the reported capability data, or the UE report may be incomplete for the intended feature.

What to inspect: Compare the returned capability containers with the later RRCReconfiguration content.

Next step: Validate that the configured features are actually declared as supported in the UE report.

Capability reporting looks incomplete or missing expected containers.

Likely cause: The enquiry may not have requested the full set needed, the decoder may be incomplete, or the UE may not report the expected capability data.

What to inspect: Check UECapabilityEnquiry first, then compare the requested and returned RAT lists.

Next step: Confirm whether the missing container is truly absent or just not decoded in the current toolchain.

Repeated capability exchange occurs.

Likely cause: The network may be revalidating capability context after context loss, mobility, or implementation-specific behavior.

What to inspect: Check whether the repeated exchange corresponds to a new connected-mode context or procedure restart.

Next step: Determine whether the repeat procedure is expected before treating it as abnormal.

LTE / 5G / Variant Comparison

Compared with UECapabilityEnquiry

UECapabilityEnquiry asks for capability data. UECapabilityInformation carries the actual UE-reported capability containers.

FAQ

What does UECapabilityInformation do in 5G NR?

It reports the UE's radio capability information back to the gNB.

Who sends UECapabilityInformation?

The UE sends UECapabilityInformation to the gNB.

What comes before UECapabilityInformation?

UECapabilityEnquiry normally comes immediately before it.

Why is UECapabilityInformation important?

It gives the network the capability data needed to build configuration that the UE can actually support.

Does UECapabilityInformation affect later RRCReconfiguration?

Yes. The reported capabilities often directly influence what the network configures next.

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.