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LTE Inter-Frequency RSTD Measurement Indication Call Flow

call-flow LTE | Positioning | Measurements | RRC

LTE inter-frequency RSTD measurement indication is the measurement procedure used when LTE positioning workflows need inter-frequency reference timing information.

This page covers the measurement indication path itself rather than generic mobility reporting.

Introduction

The network configures positioning-related measurement behavior, the UE evaluates the requested inter-frequency timing context, and the result is delivered for later positioning use.

Use this page when the trace is positioning-oriented rather than handover-oriented.

What Is Inter-Frequency RSTD Measurement Indication in Simple Terms?

What starts the procedure: The LTE side needs positioning-related inter-frequency timing measurements.
What the UE and network want to achieve: Collect the inter-frequency RSTD-related indication needed for later positioning handling.
What success looks like: The UE provides the requested indication with the expected frequency context.
What failure means: The indication is missing, tied to the wrong frequency, or not usable for the intended positioning workflow.

Why this procedure matters

This procedure is useful when the measurement branch supports positioning analysis rather than classic handover decisions.

Quick Fact Sheet

Procedure name	LTE Inter-Frequency RSTD Measurement Indication
Domain	Positioning-oriented LTE measurement handling
Main trigger	Positioning workflow needs inter-frequency RSTD context
Start state	UE is connected with positioning-related measurement setup active
End state	Inter-frequency RSTD indication is available to the network
Main nodes	UE, eNB
Main protocols	RRC
Main success outcome	Requested positioning indication is returned
Main failure outcome	Positioning-related indication is incomplete or missing
Most important messages	Measurement configuration and inter-frequency indication
Main specs	TS 36.331

LTE Inter-Frequency RSTD Measurement Indication — Click the diagram to open the full-size in a new tab.

Preconditions

Positioning-related measurement configuration is active.
The required inter-frequency context is available in the scenario.
The UE is still able to perform the requested observation in connected LTE service.

Nodes and Interfaces

Nodes involved

Node	Role in this procedure
UE	Applies measurement rules, performs the configured observations, and sends the relevant result back to the network.
eNB	Configures measurement behavior, interprets results, and uses them for mobility, optimization, or analytics decisions.

Interfaces used

Interface	Path	Role
LTE Uu	UE <-> eNB	Carries measurement configuration, reporting, and any later control action based on the result.

End-to-End Call Flow

UE                    eNB
|<--positioning config----|
|--RSTD indication------->|

Major Phases

Phase	What happens
1. Positioning setup	The network enables the relevant positioning-oriented measurement behavior.
2. Observation	The UE evaluates the requested inter-frequency timing context.
3. Indication	The UE delivers the positioning-related result.
4. Positioning use	The result is used by later positioning logic.

Step-by-Step Breakdown

Step 1: Configure positioning-related measurement behavior

Sender -> receiver: eNB -> UE

Message(s): Positioning measurement configuration

Purpose: Tell the UE which inter-frequency timing observation is required.

State or context change: The UE starts the requested positioning-related measurement handling.

Note: This path is more positioning-oriented than mobility-oriented.

Step 2: Perform the timing observation

Sender -> receiver: UE

Message(s): Inter-frequency RSTD evaluation

Purpose: Collect the timing-related observation requested by the network.

State or context change: The UE has the raw positioning measurement context.

Note: The key question is whether the right frequency layer was observed.

Step 3: Return the indication

Sender -> receiver: UE -> eNB

Message(s): Inter-frequency RSTD Measurement Indication

Purpose: Send the positioning-related result back to the LTE side.

State or context change: The network now has the indication it requested.

Note: This page stays at the measurement indication level.

Step 4: Use the result later

Sender -> receiver: Network

Message(s): Later positioning handling

Purpose: Feed the indication into the positioning workflow.

State or context change: The result becomes input for later non-call-flow logic.

Note: The later positioning result is outside this page.

Important Messages

Message	Protocol	Direction	Purpose in this procedure	What to inspect briefly
Inter-Frequency RSTD Measurement Indication	RRC	UE -> eNB	Returns the requested inter-frequency positioning-related indication.	Check the frequency context and whether the right positioning branch is being traced.
Measurement configuration	RRC	eNB -> UE	Enables the positioning-oriented observation.	Check that the requested indication matches the intended frequency context.

Important Parameters to Inspect

Parameter	What it is	Where it appears	Why it matters	Common issues
Target frequency	The LTE layer involved in the positioning observation.	Configuration and indication	Confirms the indication belongs to the intended inter-frequency context.	Wrong layer or wrong indication context.
Positioning scope	The positioning-oriented purpose of the requested observation.	Configuration	Explains why this measurement path exists.	It is mistaken for normal mobility reporting.
Timing result	The actual RSTD-related outcome returned by the UE.	Indication	Shows whether the requested observation was obtained.	Timing result is present but interpreted against the wrong target layer.
Indication timing	When the result was returned relative to the setup.	Trace timing	Useful for delayed or missing-positioning analysis.	The indication is judged too late without checking the setup time.
Later positioning use	The workflow that consumes the result.	Follow-up trace context	Shows whether the indication was the right measurement branch for the scenario.	Positioning and mobility branches are mixed together.

Successful Completion

Success means the requested inter-frequency RSTD indication is returned with the correct frequency and positioning context.

Common Failures and Troubleshooting

Symptom	Likely cause	Where to inspect	Relevant message(s)	Relevant interface(s)	Likely next step
Indication missing	The requested inter-frequency positioning observation was not completed or not captured.	Configuration and the expected indication window.	Inter-Frequency RSTD Measurement Indication	LTE Uu	Check whether the scenario really supported the requested positioning observation.

What to Check in Logs and Traces

Confirm that the trace is positioning-related rather than mobility-related.
Check the target frequency used for the RSTD indication.
Correlate the indication timing with the earlier measurement setup.

Related sub-procedures

Related message reference pages

Related troubleshooting pages

Notes

Inter-Frequency RSTD Measurement Indication is positioning-oriented. It should not be interpreted as a normal handover-trigger event page.

FAQ

What is LTE Inter-Frequency RSTD Measurement Indication?

It is the LTE positioning-related measurement indication path used for inter-frequency timing observations.