3GPP Technical Document Summary: TS 26.802 CR 0009 rev 3

Document Information

• Change Request for: TS 26.802 v19.2.0
• Work Item: FS_AMD_Ph2 (Advanced Media Delivery Phase 2)
• Category: C (functional modification of feature)
• Release: Rel-19
• Source: Qualcomm Germany
• Status: Endorsed at SA4#134

Main Objective

This CR addresses Work Topic #4: Combined Unicast-Multicast-Broadcast, extending the combination of unicast with broadcast/multicast services as introduced in TR 26.804 clause 5.12. The work includes progressing candidate solutions, studying combination with deployed media players, and defining a RESTful API between MBSF and MBS AS (reference point MBS-9) for configuring unicast repair.

Key Technical Contributions

1. Background and Problem Statement (Clause 5.12.1)

Deployment Scenarios Addressed:
- 5GMS via eMBMS and MBS
- DVB ABR Multicast (ETSI TS 103 769)
- ATSC 3.0 (A/331)
- 5G Broadcast (ETSI TS 103 720)
- DVB-I over 5G (ETSI TR 103 972)

Use Cases for Hybrid Services:
- In-session unicast repair
- Application services including hybrid services
- Reporting and metrics
- DRM support
- Common Media Client Data (CMCD)
- Targeted Ad Insertion (ISO/IEC 23009-1 6th edition)
- Fast Start-up using unicast (Segment Sequences)
- A/B Watermarking (DASH-IF ETSI TS 104 002)

Personalization Requirements:
- Requests may include personalized information (user IDs, tokens, device IDs, tracking data, CMCD)
- Responses may be customized by CDN/edge servers
- Examples: Ad tracking/beaconing, DRM license requests, targeted dynamic ads, A/B watermarking variants

2. High-Level Solutions (Clause 5.12.1.2)

Solution 1: Media Player Handles Unicast Requests
- Manifest discriminates between local media server (broadcast/multicast) and unicast requests via different URLs
- Media Player directly handles unicast requests
- Limitations: Request data terminates at local Media Server, obfuscation issues, scalability concerns

Solution 2: MBS/MBMS/5G Broadcast Client Handles Unicast Requests
- Media Player sends conditioned requests to local/gateway server
- Local/gateway server processes additional information and may issue unicast requests
- Resources may be served from broadcast, unicast, or combination
- This CR focuses on Solution 2

3. MBMS Generic Application Service (Clause 5.12.1.3)

Key Specifications from TS 26.346:
- User service announcement contains explicit Application Service Description (DASH MPD or HLS M3U8)
- Resources referenced in Application Service Entry Point document delivered as MBMS User Service
- Supports both broadcast and unicast delivery

Two Main Use Cases:
1. Unicast fallback reception: When UE moves outside MBMS coverage
2. Unicast-supplemented service offerings: Certain resources only available via unicast for enhanced user experience

Service Location Switching Techniques:

3.1 SAND4M (Clause 5.12.2.2.2)

• Uses SAND messages to signal availability of MBMS User Service
• Example: In coverage - broadcast available, supplementary unicast available
• Out of coverage - broadcast unavailable, fallback unicast available

3.2 DASH-IF Content Steering (Clause 5.12.2.2.3)

• Broader client support
• Uses Content Steering documents with pathway priorities
• TTL and reload URI for dynamic updates

3.3 Presentation Manifest Rewriting (Clause 5.12.2.2.4)

• MBMS Client understands streaming manifest (e.g., DASH MPD)
• Rewrites document based on resource availability
• Prunes unavailable Representations based on service location

4. Collaboration Scenarios (Clause 5.12.2)

Generic Application Service Architecture:
- New function in Multicast/Broadcast client for policy-based service location steering
- Application service document requested through Media Service (service location 1)
- Policy enforcement via SAND4M, manifest rewriting, or content steering

Personalized Request Handling:
- New function collects information and communicates with unicast Application Provider
- Application provider configures Multicast/Broadcast Network Function
- Configuration instruction provided to Multicast/Broadcast Clients via service announcement
- Client manages personalized requests/responses, adapts responses, selectively requests from unicast server

5. Architecture Mappings (Clause 5.12.3)

5.1 MBS AS-Based Solution (Clause 5.12.3.2)

Architecture Extensions:
- MBS AS extended beyond object repair to host content for generic application services
- May be co-located with unicast server
- MBSTF Client includes steering policy for service locations
- Media Server provides configuration API

New/Modified Reference Points:
- MBS-6': MBSF Client configures content steering policy in MBSTF Client
- MBS-7: MBS-Aware Application requests to Media Server (may include different service locations)
- MBS-9: MBSF provisions application unicast ingest in MBS AS
- MBS-12: Unicast ingest session from MBSTF to MBS AS

Extended Procedures:
1. User service provisioning includes application unicast provisioning
2. Distribution session provisioning includes content availability on application unicast
2a. MBSF provisions application unicast ingest in MBS AS via MBS-9
3. User service announcement includes instructions for application unicast
5a. MBS AS ingests application unicast content from MBSTF
8. MBSTF Client configuration extended for content steering policy
9. Distribution Session activation includes content steering policy activation
11. Distribution Session uses MBS AS selectively for unicast requests
11a. Content steering policy changes toggle between multicast (MBS-4-MC) and unicast (MBS-4-UC)
12. Requests from MBS-Aware Application may include different service locations

5.2 External Unicast Server Solution (Clause 5.12.3.3)

Architecture Extensions:
- External unicast server instead of MBS AS
- New Reference Point MBS-13: Connects MBSTF Client to MBS Application Provider
- Unicast traffic retrieved directly from MBS Application Provider (not via MBS AS)
- MBS Application Provider may be 5GMSd AS

Modified Procedures:
- Similar to MBS AS solution but uses MBS-13 for external server access
- Content steering toggles between MBS-13 and MBS-4-UC

5.3 Selective Unicast Requests (Clause 5.12.3.4)

Architecture Extensions:
- Request filter function added to MBSTF Client
- Filters based on request types (DRM license, Ad beacons, A/B watermarking)
- Requests may go to MBS AS or external application server

Modified Procedures:
1. User service provisioning includes request filters
2. Distribution session may provision content on MBS AS
3. User service announcement includes request filter instructions
8. MBSTF Client configuration includes request filter policy
9. Distribution Session activation includes request filter policy
11. Distribution Session uses MBS AS and/or external server based on request filters
12. Requests handled by multicast, unicast to MBS AS, or unicast to external server

6. Gap Analysis (Clause 5.12.4)

6.1 MBS AS-Based Solution Gaps:

1. ~~Void~~ Formal definition of named reference point between MBSTF and MBS AS
2. MBS User Service provisioning parameters at Nmb10 for content steering policy
3. MBS AS provisioning at MBS-9 for application unicast requests
4. MBS User Service Announcement parameters for application unicast
5. Unicast ingest session at MBS-12
6. MBSTF Client functional extension for service location switching
7. Support for differentiated requests from MBS-Aware Application to Media Server
8. Support for application unicast requests from MBSTF Client to MBS AS via MBS-4-UC

6.2 External Unicast Server Additional Gaps:

1. Reference point connecting MBSTF Client to MBS Application Provider
2. MBS AS provisioning at MBS-9 for external application server
3. Support for application unicast requests via MBS-13

6.3 Selective Unicast Requests Additional Gaps:

1. User service provisioning for request filters
2. MBSTF extension for selective unicast requests based on filters
3. Parallel distribution sessions at MBS-4-MC, MBS-4-UC, and/or MBS-13
4. Support for appropriate error codes

7. Candidate Solutions (Clause 5.12.5)

7.1 MBS AS-Based Solutions:

1. Use same reference point as object repair (clause 5.9)
2. URL mapping templates aligned with Content Hosting Configuration in 5GMS AS
3. Generalization of object repair provisioning
4. Include URL mapping template in MBS User Service Announcement
5. Options: SAND4M, manifest rewrite, DASH-IF Content Steering (per TS 26.501, TS 26.512)
6. No specific client extensions needed for typical clients
7. Support for HTTP request headers, URL query parameters processing

7.2 External Unicast Server and Selective Requests:

• Marked as "for further study"

8. Recommendations (Clause 8.5)

Stage 2 Normative Work (TS 26.502):

• Add functional extensions and call flows for combined MBS multicast and unicast

Stage 3 Normative Work (TS 26.517):

• Extend MBS User service protocols and formats based on stage-2 extensions

Coordination:

• Validate approaches by implementation (e.g., 5G-MAG Reference Tools)

Document Updates

New References Added:
- [42] ETSI TS 103 998: "Content Steering for DASH"
- [43] 3GPP TR 26.247: "Transparent end-to-end Packet-switched Streaming Service (PSS); Progressive Download and Dynamic Adaptive Streaming over HTTP (3GP-DASH)"

New Abbreviations:
- CMAF: Common Media Application Format
- MABR: Multicast ABR
- MBSF: Multicast/Broadcast Service Function
- MBSTF: Multicast/Broadcast Service Transport Function
- NEF: Network Exposure Function
- PCF: Policy and Charging Function

Summary

This CR provides comprehensive architectural and procedural extensions to support hybrid unicast-multicast/broadcast services in MBS User Services. It addresses multiple deployment scenarios with three main architectural approaches (MBS AS-based, external server, selective requests), identifies gaps, and proposes candidate solutions. The work enables advanced use cases like targeted advertising, A/B watermarking, DRM, and personalized content delivery while maintaining efficient broadcast distribution for common content.