# 3GPP TR 26.502 Change Request Summary

## General Information

- **CR Number**: 0047
- **Category**: A (mirror corresponding to a change in an earlier release)
- **Release**: Rel-18
- **Work Item**: 5MBUSA (5G MBS User Service Architecture)
- **Source**: BBC
- **Meeting**: S4#135, Goa, India, 9th-13th February 2026

## Reason for Change

This CR addresses two main issues:

1. **Misalignment between Stage-2 and Stage-3 specifications**: Two notification events specified by CT3 in TS 29.580 are not properly motivated at stage-2 level in TR 26.502. This issue is tracked at https://github.com/5G-MAG/rt-mbs-function/issues/11

2. **Errors in notification event depiction**: Figure 5.3-2 contains errors in the depiction of event notifications. This issue is tracked at https://github.com/5G-MAG/Standards/issues/188

## Technical Changes

### Section 4.6.2: Notification Events

**Modifications to Table 4.6.2-1**:

- **Column simplification**: The final column of the notification events table has been simplified for improved clarity. The column header changed from "Applicable reference point(s)" to "Stimulating reference point(s)"

- **Added motivation for missing events**: Two notification events that were previously not properly motivated have been updated:
  - **User Service advertisement event**: Now includes proper description and stimulating reference point (Nmb10/Nmb5)
  - **User Data Ingest Session starting event**: Clarified with appropriate reference point information

- **Clarification of event sources**: The table now more clearly indicates which reference points stimulate each notification event, with brackets indicating intermediate reference points and explicit notation of the final delivery reference points (Nmb10/Nmb5)

### Section 5.3: Procedures for User Service Provisioning

**Corrections to Figure 5.3-2 Call Flow**:

Three specific steps in the MBS User Service internal provisioning procedure have been corrected:

- **Step 14**: Corrected the event notification from MBSTF to MBSF regarding content ingest establishment status using the `Distribution Session established` event

- **Step 15**: Corrected the event notification from MBSF to MBS Application Provider regarding content ingest establishment, properly distinguishing between `Distribution Session established` event (success case) and `Distribution Session establishment failure` event (failure case)

- **Step 17**: Corrected the final notification event from MBSF to MBS Application Provider regarding the overall MBS User Data Ingest Session status, properly distinguishing between `User Data Ingest Session established` event (success case) and `User data ingest failure` event (failure case)

## Impact Assessment

**Consequences if not approved**:
- Continued misalignment between stage-2 (SA4) and stage-3 (CT3) normative specifications
- The MBSF cannot be implemented correctly as currently specified

**Alignment impact**:
- This CR aligns TS 26.502 with TS 29.580
- No impact on TS 29.580 is required