UE Radio Capability Info Indication is the NGAP message sent by the NG-RAN node to the AMF to provide UE radio capability information or capability ID context for storage and later use.
Message Fact Sheet
Protocol
ngap
Network
5g
Spec
3GPP TS 38.413
Spec Section
UE Radio Capability Management messages and UE Radio Capability Info Indication (Release 18 baseline)
NG-RAN has obtained or updated UE radio capability information and reports it to AMF for storage, reuse, paging handling, or later capability management procedures.
Main purpose
Transfers UE radio capability information to the AMF, supports AMF-side capability storage, enables later UE context and mobility decisions, helps avoid repeated capability retrieval, and supports capability ID based optimization when applicable.
Main specification
3GPP TS 38.413, UE Radio Capability Management messages and UE Radio Capability Info Indication (Release 18 baseline)
Release added
Release 15
Procedures where used
UE Radio Capability Info Indication, UE Radio Capability Management, AMF capability storage, Paging capability optimization, Capability ID based optimization
What is UE Radio Capability Info Indication in simple terms?
UE Radio Capability Info Indication is the NGAP message sent by the NG-RAN node to the AMF to provide UE radio capability information or capability ID context for storage and later use.
Transfers UE radio capability information to the AMF, supports AMF-side capability storage, enables later UE context and mobility decisions, helps avoid repeated capability retrieval, and supports capability ID based optimization when applicable.
Why this message matters
UE Radio Capability Info Indication is the gNB telling AMF what it knows about a UE's radio capability, possibly using a capability ID instead of sending the full payload every time.
Where this message appears in the call flow
UE Radio Capability Info Indication
Reporting branch: NG-RAN provides full capability information, paging capability, or capability ID context for AMF storage.
Call flow position: NG-RAN sends this initiatingMessage to provide UE radio capability information or related capability ID context to the AMF.
Typical state: AMF stores or updates UE capability context for later use.
Preconditions:
AMF UE NGAP ID and RAN UE NGAP ID identify the UE-associated NGAP context.
NG-RAN has capability information, paging capability information, or capability ID context to report.
Next likely message: AMF-side capability storage and later UE handling
Capability storage and reuse
The indication can carry full capability information or ID-based context when capability reuse is possible.
Call flow position: The indication can reduce repeated capability retrieval by allowing AMF to store full capability information or a valid capability ID.
Typical state: Stored capability information can support setup, modification, mobility, paging, and capability ID handling.
Preconditions:
Optional capability fields are decoded and stored according to AMF policy.
UE Radio Capability ID Validity is interpreted if a capability ID is present.
Next likely message: Later capability-dependent procedure
Capability management distinction
Info Indication reports capability context. Check Request/Response asks for and returns a compatibility result.
Call flow position: The indication is different from UE Radio Capability Check Request/Response and ID Mapping Request/Response.
Typical state: Trace analysis treats this as capability reporting, not compatibility checking or ID resolution.
Preconditions:
Procedure name, direction, and optional IEs are checked before interpreting the message.
Next likely message: Correct procedure-specific analysis
Transport / encapsulation: NGAP over SCTP/IP between NG-RAN and AMF
Security context: The message can carry UE radio capability information and capability ID context. It is capability reporting, not a compatibility result response.
Message Structure Overview
UE Radio Capability Info Indication is an NG-RAN-to-AMF initiatingMessage in UE Radio Capability Management.
AMF UE NGAP ID and RAN UE NGAP ID identify the UE context.
The message can carry full UE Radio Capability, paging-related capability, capability ID, and capability ID validity information.
There is no direct paired response message.
The message reports capability information; it is not a compatibility check result.
ASN.1 for 5G NGAP - UE Radio Capability Info Indication
UERadioCapabilityInfoIndication ::= SEQUENCE {
protocolIEs ProtocolIE-Container { {UERadioCapabilityInfoIndication-IEs} },
...
}
UERadioCapabilityInfoIndication-IEs NGAP-PROTOCOL-IES ::= {
{ ID id-AMF-UE-NGAP-ID CRITICALITY reject TYPE AMF-UE-NGAP-ID PRESENCE mandatory } |
{ ID id-RAN-UE-NGAP-ID CRITICALITY reject TYPE RAN-UE-NGAP-ID PRESENCE mandatory } |
{ ID id-UERadioCapability CRITICALITY ignore TYPE UERadioCapability PRESENCE optional } |
{ ID id-UERadioCapabilityForPaging CRITICALITY ignore TYPE UERadioCapabilityForPaging PRESENCE optional } |
{ ID id-UERadioCapabilityID CRITICALITY ignore TYPE UERadioCapabilityID PRESENCE optional } |
{ ID id-UERadioCapabilityIDValidity CRITICALITY ignore TYPE UERadioCapabilityIDValidity PRESENCE optional },
...
}
How to read this ASN.1
Decode both UE identifiers first, then inspect the optional capability fields that are present. The full capability container, paging capability, capability ID, and ID validity are separate pieces of capability context.
5G NGAP - UE Radio Capability Info Indication - Example Dump
Treat this as a teaching example based on the expected message structure, not as a captured network trace.
Optional capability fields appear only when relevant.
There is no direct response message for this indication.
Do not confuse capability reporting with UE Radio Capability Check Response, which reports a compatibility result.
Important Information Elements
IE
Required
Description
Message Type
Yes
Identifies the NGAP PDU as UE RADIO CAPABILITY INFO INDICATION.
AMF UE NGAP ID
Yes
Mandatory AMF-side UE identifier used to bind the capability information to the correct UE-associated NGAP context.
RAN UE NGAP ID
Yes
Mandatory NG-RAN-side UE identifier used to bind the indication to the radio-side UE context.
UE Radio Capability
Optional
Optional full UE radio capability information reported by NG-RAN.
UE Radio Capability for Paging
Optional
Optional capability information relevant to paging behavior.
UE Radio Capability ID
Optional
Optional identifier for a UE radio capability set, used to reduce repeated full capability transfer when valid.
UE Radio Capability ID Validity
Optional
Optional validity indication for the provided UE Radio Capability ID.
Detailed field explanation
Message Type
Identifies the NGAP PDU as UE RADIO CAPABILITY INFO INDICATION.
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.
AMF UE NGAP ID
Mandatory AMF-side UE identifier used to bind the capability information to the correct UE-associated NGAP context.
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.
RAN UE NGAP ID
Mandatory NG-RAN-side UE identifier used to bind the indication to the radio-side UE context.
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 Radio Capability
Optional full UE radio capability information reported by NG-RAN.
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.
UE Radio Capability for Paging
Optional capability information relevant to paging behavior.
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.
UE Radio Capability ID
Optional identifier for a UE radio capability set, used to reduce repeated full capability transfer when valid.
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.
UE Radio Capability ID Validity
Optional validity indication for the provided UE Radio Capability ID.
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 direction is NG-RAN node to AMF.
Match AMF UE NGAP ID and RAN UE NGAP ID to the active UE context.
Check UE Radio Capability when full capability reporting is expected.
Decode UE Radio Capability for Paging if paging behavior is under investigation.
Decode UE Radio Capability ID and UE Radio Capability ID Validity if present.
Do not expect a direct response message.
Do not confuse this indication with UE Radio Capability Check Response.
Common Issues and Troubleshooting
AMF does not appear to have UE radio capability information later.
Likely cause: The indication may be missing, the UE Radio Capability IE may be absent, or AMF-side storage may not have updated.
What to inspect: Check the Info Indication, UE identifiers, and optional UE Radio Capability field.
Next step: Confirm AMF stores the decoded capability context against the correct UE.
Capability ID based reuse fails.
Likely cause: UE Radio Capability ID Validity may be missing, invalid, or ignored.
What to inspect: Decode UE Radio Capability ID and UE Radio Capability ID Validity together.
Next step: Use full capability information or perform ID mapping if the ID cannot be trusted.
Paging behavior does not match UE capability.
Likely cause: UE Radio Capability for Paging may be absent or not consumed by AMF.
What to inspect: Check whether the paging-specific capability field is present in the indication.
Next step: Correlate paging behavior with stored paging capability information.
Trace analyst expects a response message.
Likely cause: Info Indication is being treated like Check Request or ID Mapping Request.
What to inspect: Check the procedure type and message direction.
Next step: Treat this as a one-way indication and analyze later AMF behavior instead of a direct response.
Message is mistaken for a compatibility result.
Likely cause: UE Radio Capability Info Indication is being confused with UE Radio Capability Check Response.
What to inspect: Check for full capability or capability ID fields versus IMS Voice Support Indicator.
Next step: Use Info Indication for capability storage analysis and Check Response for compatibility result analysis.
LTE / 5G / Variant Comparison
Compared with UE Radio Capability Check Request
Info Indication transfers capability information from NG-RAN to AMF. Check Request asks NG-RAN to evaluate capability compatibility.
Compared with UE Radio Capability Check Response
Info Indication carries capability context. Check Response carries the compatibility result, especially IMS Voice Support Indicator.
Compared with UE Radio Capability ID Mapping
Info Indication may report capability ID context. ID Mapping Request/Response resolves capability IDs when mapping is needed.
FAQ
What is UE Radio Capability Info Indication in NGAP?
It is the NG-RAN-to-AMF message used to report UE radio capability information, paging capability information, or related capability ID context.
Who sends UE Radio Capability Info Indication?
The NG-RAN node sends UE Radio Capability Info Indication to the AMF.
Does this message require a response?
No. UE Radio Capability Info Indication is a one-way indication and has no direct paired response message.
What is UE Radio Capability IE?
It is the optional full UE radio capability information container reported by NG-RAN when full capability reporting is needed.
What is UE Radio Capability for Paging?
It is optional capability information relevant to paging behavior and paging optimization.
What is UE Radio Capability ID?
It is an identifier for a UE radio capability set that can reduce repeated full capability transfer when the ID is valid and understood.
How is this different from UE Radio Capability Check Response?
Info Indication reports capability context. Check Response reports the result of an AMF-requested compatibility check, mainly through IMS Voice Support Indicator.
How do you troubleshoot missing UE capability information?
Match UE identifiers, check whether UE Radio Capability or capability ID fields are present, verify ID validity, and confirm AMF-side storage or later reuse.
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.
