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RRC5GgNB -> UE3GPP TS 38.331
5G NR - Measurement Configuration
Measurement Configuration is the NR RRC configuration block that tells the UE what to measure, when to report, and how measurement identities map objects and report rules. It is usually delivered inside RRC Reconfiguration rather than as a standalone message.
Message Fact Sheet
Protocol
rrc
Network
5g
Spec
3GPP TS 38.331
Spec Section
5.5, 6.3.2
Direction
gNB -> UE
Message Type
Measurement Configuration / Mobility Control
Full message name
5G NR - Measurement Configuration
Protocol
RRC
Technology
5G
Direction
gNB -> UE
Interface
Uu
Signaling bearer / channel
SRB1 / DCCH
Typical trigger
Sent when the gNB needs to start, modify, or optimize connected-mode measurements for mobility, beam management, or radio troubleshooting.
Main purpose
Provides the UE with measurement objects, report configurations, gap settings, and measurement identities so that connected-mode mobility and measurement reporting work as intended.
Reporting behavior depends on event thresholds, hysteresis, time-to-trigger, and report intervals defined by the measurement configuration, Measurement gap behavior depends on the configured gap pattern rather than a dedicated standalone transaction timer
Related cause values
Measurement Configuration does not carry reject causes, Problems are usually inferred from wrong or missing reports, unstable mobility behavior, or UE inability to measure the configured targets
What is Measurement Configuration in simple terms?
Measurement Configuration is the NR RRC configuration block that tells the UE what to measure, when to report, and how measurement identities map objects and report rules. It is usually delivered inside RRC Reconfiguration rather than as a standalone message.
Provides the UE with measurement objects, report configurations, gap settings, and measurement identities so that connected-mode mobility and measurement reporting work as intended.
Why this message matters
Measurement Configuration is the set of RRC instructions that tells the UE what to measure and when to report it back to the network.
Where this message appears in the call flow
Connected-Mode Mobility Setup
Call flow position: Delivered when the gNB prepares the UE for connected-mode measurements.
Typical state: UE is connected and able to receive dedicated RRC configuration.
Preconditions:
SRB1 is established.
Security is active.
The gNB has decided which cells, beams, or frequencies should be measured.
Next likely message: Measurement Report once a configured condition is met
Handover Preparation
Call flow position: Used before the network expects mobility-triggering reports.
Typical state: UE is connected and evaluating serving and neighbor radio conditions.
Preconditions:
Relevant measurement objects and report configurations are present.
Neighbor targets or beam targets are known to the gNB.
Next likely message: Measurement Report followed by handover-related action
Measurement Optimization / Re-tuning
Call flow position: Used when the network updates measurement strategy because the current configuration is too noisy, too weak, or incomplete.
Typical state: UE remains connected while measurement behavior is adjusted.
Preconditions:
An earlier measurement configuration already exists or needs replacement.
Next likely message: Updated Measurement Report behavior under the new configuration
Domain: Access-side radio control and mobility optimization
Signaling bearer: SRB1
Logical channel: DCCH
Transport / encapsulation: Dedicated RRC configuration carried inside RRC Reconfiguration on DCCH
Security context: Dedicated UE-specific AS-protected RRC signaling after security activation in connected mode.
Message Structure Overview
Measurement Configuration is not usually decoded as a standalone message. It is a configuration block inside RRC Reconfiguration.
For engineering work, the most important parts are the measurement objects, report configurations, and measurement identities because they explain why a later Measurement Report exists or does not exist.
The key trace question is not only what the UE measured, but what the network actually asked the UE to measure.
ASN.1 for 5G NR - Measurement Configuration
MeasConfig ::= SEQUENCE {
measObjectToRemoveList SEQUENCE (SIZE (1..maxObjectId)) OF MeasObjectId OPTIONAL,
measObjectToAddModList SEQUENCE (SIZE (1..maxNrofMeasObjects)) OF MeasObjectToAddMod OPTIONAL,
reportConfigToRemoveList SEQUENCE (SIZE (1..maxReportConfigId)) OF ReportConfigId OPTIONAL,
reportConfigToAddModList SEQUENCE (SIZE (1..maxNrofReportConfig)) OF ReportConfigToAddMod OPTIONAL,
measIdToRemoveList SEQUENCE (SIZE (1..maxMeasId)) OF MeasId OPTIONAL,
measIdToAddModList SEQUENCE (SIZE (1..maxNrofMeasId)) OF MeasIdToAddMod OPTIONAL,
quantityConfig QuantityConfig OPTIONAL,
measGapConfig MeasGapConfig OPTIONAL,
...
}
How to read this ASN.1
In practice, engineers focus on the relationship between measObject, reportConfig, and measId. Those three blocks explain almost all later reporting behavior.
The most important field for troubleshooting is often measId because it links the object and report rule.
A later Measurement Report with measId 3 should be interpreted against this exact configuration.
If no reports appear, start by checking whether the object, report rule, and mapping were all present and sensible.
Important Information Elements
IE
Required
Description
measObjectToAddModList
Yes
Defines what the UE should measure, such as NR, LTE, or beam-related targets.
reportConfigToAddModList
Yes
Defines when and how the UE should report, including event and periodic behavior.
measIdToAddModList
Yes
Maps measurement objects to report configurations and is one of the most important blocks for trace analysis.
quantityConfig
Optional
Controls how measurement quantities such as RSRP, RSRQ, and SINR are filtered and interpreted.
measGapConfig
Optional
Tells the UE when measurement gaps are available for targets that cannot be measured continuously.
Detailed field explanation
measObjectToAddModList
Defines what the UE should measure, such as NR, LTE, or beam-related targets.
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.
reportConfigToAddModList
Defines when and how the UE should report, including event and periodic behavior.
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.
measIdToAddModList
Maps measurement objects to report configurations and is one of the most important blocks for trace analysis.
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.
quantityConfig
Controls how measurement quantities such as RSRP, RSRQ, and SINR are filtered and interpreted.
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.
measGapConfig
Tells the UE when measurement gaps are available for targets that cannot be measured continuously.
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 that Measurement Configuration was actually delivered inside RRC Reconfiguration.
Verify the measObject, reportConfig, and measId mapping.
Inspect event thresholds, hysteresis, and time-to-trigger before judging the UE's reporting behavior.
Check whether measurement gaps were configured where the target frequency or RAT required them.
Correlate the configuration with later Measurement Reports and mobility actions.
If reports are missing or noisy, validate the configuration before blaming UE measurements.
Common Issues and Troubleshooting
The UE never sends Measurement Report.
Likely cause: The measurement configuration may be missing, too restrictive, or mapped incorrectly.
What to inspect: Check measObjectToAddModList, reportConfigToAddModList, and measIdToAddModList first.
Next step: Confirm the configured event can really be met in the observed radio conditions.
The UE reports too often.
Likely cause: The event trigger may be too sensitive or the radio environment may be unstable.
What to inspect: Check hysteresis, time-to-trigger, and report interval settings.
Next step: Tune the configuration or analyze the radio fluctuation causing repeated triggers.
The network expects inter-frequency or inter-RAT reports but receives none.
Likely cause: The target measurement object or measurement gap configuration may be incomplete.
What to inspect: Check the configured measurement object and whether measGapConfig supports that target.
Next step: Validate that the UE had a practical way to measure the configured target.
LTE / 5G / Variant Comparison
Measurement Configuration versus Measurement Report
Measurement Configuration defines what the UE should do. Measurement Report is the UE's response when the configured conditions are satisfied.
Measurement Configuration versus standalone RRC messages
Measurement Configuration is usually an information element group inside RRC Reconfiguration, not a standalone over-the-air message by itself.
FAQ
What is Measurement Configuration in 5G NR?
Measurement Configuration is the NR RRC configuration block that tells the UE what to measure, when to report, and how reporting identities are mapped.
Is Measurement Configuration a standalone RRC message?
Usually no. It is typically carried inside RRC Reconfiguration.
Why is measId important?
Because measId links the measurement object to the report configuration and explains why a later report was triggered.
What comes after Measurement Configuration?
Usually Measurement Report once the configured event or reporting condition is satisfied.
Why are measurement gaps important?
Because without the right gap configuration the UE may not be able to measure some target frequencies or RATs properly.
Can bad Measurement Configuration cause handover problems?
Yes. If the network configures the wrong objects, thresholds, or mappings, the UE may not report the right mobility conditions.
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.