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LTE MBMS Interest Indication Call Flow

call-flow LTE | MBMS | Interest | RRC

LTE MBMS Interest Indication is the UE-side LTE reporting path used when the UE needs to expose MBMS interest back to the network.

It is a reporting branch rather than a content-delivery branch, and it should be read together with the MBMS context that exists before the report is sent.

Introduction

This procedure centers on the UE-side MBMS interest report and the MBMS context that gives that report meaning.

Use it when the main question is whether the UE exposed MBMS interest clearly enough for the network to use in later MBMS-related handling.

What Is LTE MBMS Interest Indication in Simple Terms?

What starts the procedure: The UE needs to report MBMS interest to the network.
What the UE and network want to achieve: Expose MBMS interest so the network can use it in later handling.
What success looks like: MBMS Interest Indication appears and lines up with the MBMS context behind it.
What failure means: The MBMS interest report is missing, unclear, or detached from the right MBMS context.

Why this procedure matters

MBMS interest reporting is one of the clearest UE-side indicators of MBMS relevance. If it is missing or misread, later MBMS behavior can look surprising even though the UE never exposed the expected service interest.

Quick Fact Sheet

Procedure name	LTE MBMS Interest Indication
Domain	LTE MBMS interest reporting
Main trigger	UE-side need to expose MBMS interest
Start state	MBMS context is relevant to the UE
End state	The network has a UE-side MBMS interest report
Main nodes	UE, eNB
Main protocols	RRC MBMS interest reporting
Main success outcome	The MBMS interest report is visible and usable
Main failure outcome	MBMS interest stays unclear at the network side
Most important messages	MBMS Interest Indication r11, SIB13
Main specs	TS 36.331

LTE MBMS Interest Indication Call Flow — Click the diagram to open the full-size in a new tab.

Preconditions

MBMS context is already relevant to the UE.
The UE is in the correct state to send MBMS interest reporting.
The network can receive and interpret the MBMS interest report.

Nodes and Interfaces

Nodes involved

Node	Role in this procedure
UE	Sends the MBMS interest report to the network.
eNB	Receives the MBMS interest report and uses it in later MBMS handling.
MBMS context	Provides the service-interest background that explains the report.

Interfaces used

Interface	Path	Role
UL-DCCH	UE -> eNB	Carries MBMS Interest Indication in connected mode.
LTE Uu	UE <-> eNB	Carries the full MBMS interest-reporting branch.
BCCH / DL-SCH	eNB -> UE	Carry the MBMS broadcast context that exists before the report.

End-to-End Call Flow

UE                         eNB
|--MBMS context known-------->|
|--MBMS Interest Indication--->|
|--later MBMS continuation---->|

Major Phases

Phase	What happens
1. MBMS context exists	The UE already has MBMS-relevant background context.
2. UE-side report decision	The UE reaches the point where interest reporting is needed.
3. Interest report upload	MBMS Interest Indication is sent.
4. Later MBMS handling	The network uses the report in later MBMS-related decisions.

Step-by-Step Breakdown

Start from the MBMS broadcast context

Sender -> receiver: eNB -> UE

Message(s): SIB13 and MBMS background

Purpose: Anchor the interest report in the MBMS context already visible to the UE.

State or context change: The UE has MBMS context before the report is sent.

Note: The report is easiest to understand when the earlier MBMS background is visible first.

Reach the interest-report point

Sender -> receiver: UE

Message(s): MBMS interest reporting decision

Purpose: Move into the branch where the UE exposes MBMS interest.

State or context change: The UE is ready to send the report.

Note: This step explains why the report appears at this point and not earlier.

Send MBMS Interest Indication

Sender -> receiver: UE -> eNB

Message(s): MBMS Interest Indication r11

Purpose: Tell the network that MBMS interest is relevant for the UE.

State or context change: The network now has a direct UE-side MBMS interest report.

Note: This is one of the clearest MBMS interest signals in the LTE trace.

Correlate the report with later MBMS handling

Sender -> receiver: eNB

Message(s): Later MBMS continuation

Purpose: Check how the network used the interest report after receiving it.

State or context change: The interest-report branch is now tied to later MBMS behavior.

Note: Do not treat the report as the endpoint if the later MBMS decision is the real question.

Important Messages

Message	Protocol	Direction	Purpose in this procedure	What to inspect briefly
System Information Block Type 13	RRC	eNB -> UE	Provides the MBMS area context behind the report.	Check whether the MBMS background existed before the interest report appeared.
MBMS Interest Indication r11	RRC	UE -> eNB	Reports MBMS interest back to the network.	Check what MBMS interest the UE was exposing and why it appeared at this point.
MBMS Counting Request r10	RRC	eNB -> UE	Useful related context if the interest path is tied to a counting branch.	Check whether MBMS interest reporting followed a counting-related trigger or a broader MBMS interest change.

Important Parameters to Inspect

Parameter	What it is	Where it appears	Why it matters	Common issues
MBMS interest scope	The service-interest context exposed by the UE.	MBMS Interest Indication	Explains what the UE was trying to report.	The report is found, but the actual interest scope is never identified.
Earlier MBMS background	The MBMS context that existed before the report.	SIB13 and earlier MBMS setup	Needed to keep the report tied to the right MBMS environment.	The report is analyzed with no earlier MBMS context.
Report timing	When the report appeared relative to MBMS context changes.	Across the reporting branch	Useful when the report appears later than expected.	The report timing is treated as random or unrelated.
Related counting context	Whether the interest report is close to a counting branch.	MBMS counting context	Helps separate direct interest reporting from demand-estimation exchange.	Interest reporting and counting are treated as the same branch.
Later MBMS effect	What the network did after receiving the report.	Later MBMS continuation	Shows whether the report had visible downstream effect.	The interest report is found, but later handling is never checked.

Successful Completion

Success means the MBMS interest report is visible, understandable, and tied to the correct MBMS context.

Common Failures and Troubleshooting

Symptom	Likely cause	Where to inspect	Relevant message(s)	Relevant interface(s)	Likely next step
The UE should have exposed MBMS interest, but no report appears	The MBMS context may not have reached the right reporting point or the report was not captured.	Earlier MBMS context and the period where reporting should have happened.	SIB13 and later MBMS reporting context	LTE Uu	Do not assume the absence of the report means the MBMS context never existed.
The report exists, but later MBMS handling still looks unexplained	The report is being read without the later decision branch.	MBMS Interest Indication plus later MBMS continuation.	MBMS Interest Indication r11	LTE Uu	Carry the analysis past the report into the later MBMS branch.

What to Check in Logs and Traces

Tie the report back to the earlier MBMS background.
Keep MBMS counting and MBMS interest reporting separated unless the trace shows both branches together.
Follow the report into the later MBMS handling path.

Related sub-procedures

Related message reference pages

Related troubleshooting pages

Notes

MBMS Interest Indication is a UE-side reporting branch. It should be read with the MBMS background already in view.

FAQ

What is LTE MBMS Interest Indication?

It is the UE-side LTE RRC message used to report MBMS interest to the network.

Is MBMS Interest Indication the same as MBMS counting?

No. MBMS counting is a demand-estimation exchange, while MBMS interest indication is a direct UE-side report of MBMS interest.