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RRC5GgNB -> UE3GPP TS 38.331
5G NR - UE Information Request
UE Information Request is the NR RRC message the network uses to ask the UE for diagnostic information such as radio link failure context, connection establishment failure context, logged measurements, mobility history, random access reports, or idle and inactive measurement information.
Message Fact Sheet
Protocol
rrc
Network
5g
Spec
3GPP TS 38.331
Spec Section
5.6, 6.2.2
Direction
gNB -> UE
Message Type
Diagnostic / Reporting Control
Full message name
5G NR - UE Information Request
Protocol
RRC
Technology
5G
Direction
gNB -> UE
Interface
Uu
Signaling bearer / channel
SRB1 / DL-DCCH
Typical trigger
Used when the network wants the UE to return one or more stored or available diagnostic reports, especially after failure recovery, mobility analysis, or coverage troubleshooting.
Main purpose
Requests UE-generated diagnostic or historical information that helps the network analyze failures, mobility behavior, random access issues, and measurement history.
Main specification
3GPP TS 38.331, 5.6, 6.2.2
Release added
Release 15
Procedures where used
Radio Link Failure Investigation, Connection Establishment Failure Investigation, Mobility Diagnostics, Random Access Diagnostics
What is UE Information Request in simple terms?
UE Information Request is the NR RRC message the network uses to ask the UE for diagnostic information such as radio link failure context, connection establishment failure context, logged measurements, mobility history, random access reports, or idle and inactive measurement information.
Requests UE-generated diagnostic or historical information that helps the network analyze failures, mobility behavior, random access issues, and measurement history.
Why this message matters
UE Information Request is the network asking the UE to send back stored diagnostic information about failures, measurements, mobility, or access behavior.
Where this message appears in the call flow
Radio Link Failure Investigation
Call flow position: Sent when the network wants UE-side diagnostic information after failure or recovery-related behavior.
Typical state: UE is connected or has re-entered connected operation and the network wants historical or stored diagnostic data.
Preconditions:
AS security is active.
The network expects the UE to have relevant stored or available information.
Next likely message: UEInformationResponse
Mobility and Measurement Diagnostics
Call flow position: Used when the network needs UE-side measurement history or mobility history information.
Typical state: UE is connected and can return diagnostic information on request.
Preconditions:
Relevant measurement or mobility history exists or may exist in the UE.
Next likely message: UEInformationResponse or later measurement-related action
Random Access and Connection Failure Analysis
Call flow position: Relevant when the network wants details about random access behavior or connection establishment failure reports.
Typical state: The network is troubleshooting access-side problems using UE-side stored context.
Preconditions:
The UE supports the requested report type.
Relevant failure or access history is available in the UE.
Next likely message: UEInformationResponse
Call flow position
Previous message(s):RRC Reconfiguration, Radio recovery or mobility context, Failure or diagnostic investigation trigger
Domain: Access-side RRC diagnostics and failure analysis
Signaling bearer: SRB1
Logical channel: DL-DCCH
Transport / encapsulation: Dedicated RRC signaling on SRB1 over DCCH in connected mode
Security context: Sent as protected connected-mode RRC signaling after AS security activation, usually when the network wants extra UE-side diagnostic context.
Message Structure Overview
UE Information Request is mostly a set of report request flags rather than a large configuration message.
Its operational meaning depends on which report types are requested, because each requested flag points to a different diagnostic workflow.
The message is best interpreted as the network asking the UE for stored evidence about failure, mobility, measurement, or access behavior.
The key engineering point is that the message contains request flags rather than the report contents themselves. The useful data comes later in UEInformationResponse.
Each present flag shows what kind of diagnostic information the network expects in the UE response.
The absence of a flag matters, because it tells you which report types were not requested.
The next trace step should usually be UEInformationResponse, not another diagnostic guess.
Important Information Elements
IE
Required
Description
connEstFailReportReq
Optional
Requests connection establishment failure report information from the UE if available.
rlf-ReportReq
Optional
Requests radio link failure information from the UE if available.
logMeasReportReq
Optional
Requests logged measurement information from the UE.
mobilityHistoryReportReq
Optional
Requests UE mobility history information.
ra-ReportReq
Optional
Requests random access related report information.
idleModeMeasurementReq-r16
Optional
Requests idle or inactive measurement information from the UE if available.
Detailed field explanation
connEstFailReportReq
Requests connection establishment failure report information from the UE if available.
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.
rlf-ReportReq
Requests radio link failure information from the UE if available.
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.
logMeasReportReq
Requests logged measurement information from the UE.
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.
mobilityHistoryReportReq
Requests UE mobility history information.
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.
ra-ReportReq
Requests random access related report information.
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.
idleModeMeasurementReq-r16
Requests idle or inactive measurement information from the UE if available.
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
Check which report request flags are present.
Verify that the requested report types make sense for the observed problem, such as RLF, random access, or mobility history.
Correlate the request with the likely trigger, for example handover failure, access failure, or coverage issue.
Check whether UEInformationResponse follows and whether it actually contains the requested report types.
If the response is missing or incomplete, check UE capability support and whether the UE had relevant stored information to return.
Use this message together with measurement, reestablishment, paging, or initial access traces depending on the requested report type.
Common Issues and Troubleshooting
UE Information Request is sent but no UEInformationResponse appears.
Likely cause: The UE may not support the requested report path, may not have relevant stored information, or the procedure may be interrupted.
What to inspect: Check requested flags, UE support, connection stability, and whether the trace continues long enough for the response.
Next step: Correlate with the exact failure or recovery procedure instead of assuming the request itself is malformed.
UEInformationResponse appears but does not contain the expected report.
Likely cause: The UE may not have stored the requested information or the requested condition may not have occurred.
What to inspect: Check which flags were requested and whether the underlying failure or measurement event truly happened.
Next step: Validate the assumption that the UE should have report data before escalating to decoder or protocol issues.
Wrong report type seems to be requested for the problem under investigation.
Likely cause: The network may be requesting generic diagnostics rather than the most precise report, or the engineer may be reading the scenario incorrectly.
What to inspect: Compare the requested flags with the actual symptom: random access, connection failure, mobility failure, or RLF.
Next step: Interpret the request as a diagnostic intent signal from the network and correlate with the broader troubleshooting workflow.
LTE / 5G / Variant Comparison
UE Information Request versus UE Information Response
UE Information Request asks for diagnostic information. UE Information Response carries the actual UE-side diagnostic content.
UE Information Request versus Measurement Report
Measurement Report is event-driven UE feedback from configured measurements. UE Information Request is an on-demand network request for stored or available diagnostic information.
FAQ
What is UE Information Request in 5G NR?
UE Information Request is the NR RRC message the network uses to ask the UE for diagnostic information such as RLF, connection failure, mobility history, logged measurements, or random access information.
Who sends UE Information Request?
The network side sends UE Information Request to the UE.
What comes after UE Information Request?
The normal follow-up is UEInformationResponse from the UE.
Does UE Information Request carry the report itself?
No. It only indicates which report types the network wants the UE to send back.
Why is UE Information Request useful in troubleshooting?
Because it shows which diagnostic information the network is asking for and helps engineers correlate the later UE response with the suspected problem area.
Is UE Information Request the same as Measurement Report?
No. Measurement Report is UE-triggered feedback based on configured rules, while UE Information Request is a network-triggered diagnostic request.
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.