Change Request Summary: Multi-access Media Delivery - Additional Requirement

CR Metadata

• CR Number: 0033 rev 0
• Specification: TS 26.804 v19.1.0
• Category: C (functional modification of feature)
• Release: Rel-19
• Work Item: FS_AMD_Ph2 (Feasibility Study on Advanced Media Distribution Phase 2)
• Source: LG Electronics Inc.

Purpose and Rationale

This CR addresses a gap in multi-access media delivery when M4 media flows are transported using GBR QoS flows. The main issue is that the current 5G Media Streaming architecture (TS 26.501) lacks mechanisms to convey QoS-related information from non-3GPP access networks to 5GMS control plane entities. This prevents consistent QoS treatment across heterogeneous access networks (3GPP and non-3GPP) in multi-access scenarios.

Technical Contributions

1. Gap Analysis Enhancement (Clause 5.18.5.2.2)

Identified Gaps

Path Identification Limitations:
- Current Dynamic Policy procedures cannot request policy treatment over specific access networks when M4 flows use multiple access networks
- The IPPacketFilterSet parameters (sourceAddress and destinationAddress) in ApplicationFlowDescription only support IP addresses of the Multi-Access PDU Session
- MPTCP and MPQUIC link-specific multipath addresses are not routable via N6, making them unsuitable for Dynamic Policy instantiation requests to 5GMS AF

GBR QoS Flow Constraints:
- According to TS 23.501 clause 5.32.4, traffic splitting for GBR QoS Flows is not supported in Rel-18 ATSSS
- If M4 media flows are transported as GBR QoS Flows, traffic splitting using ATSSS is not supported in this release
- Future ATSSS specification updates need to be monitored

QoS Mapping Gap:
- The 5G Media Streaming architecture (TS 26.501 Figure 4.1.1) lacks mechanisms or reference points to convey QoS information from non-3GPP accesses to 5GMS control plane/entities
- No capability to compare whether QoS requirements for media streaming can be supported across 3GPP and non-3GPP accesses
- Current TS 23.501 requires non-3GPP access to include Additional QoS Information, but this is outside ATSSS scope

NOTE: QoS mapping from non-3GPP access to 3GPP-based QoS profiles can facilitate GBR QoS flow support in multi-access scenarios

2. New Procedure: Multi-access Dynamic Policy with Non-3GPP QoS Mapping (Clause 5.18.X.X)

This CR introduces a new informative procedure for handling QoS mapping between non-3GPP and 3GPP access networks.

Procedure Steps

Initial Setup (Steps 1-4):
1. 5G Media Streaming session established over Multi-Access PDU Session with M4 flows over 3GPP access
2. Media Session Handler instantiates Dynamic Policy in 5GMS AF (per TS 26.501 clause 5.7.4), potentially including QoS specifications
3. 5GMS AF interacts with PCF (directly in Trusted DN or via NEF in external DN) to apply requested Dynamic Policy
4. M4 media flows transferred over 3GPP access with requested dynamic policy

Multi-access Setup (Step 5):
- Multi-access media delivery session established using both 3GPP and non-3GPP access networks
- 5GMS-Aware Application may or may not be aware of multi-access delivery

Non-3GPP QoS Mapping Procedure (Step 6):
- 6a: UE collects QoS information from 3GPP access (e.g., QoS profile, GBR capability)
- 6b: UE ATSSS steering functionality forwards 3GPP QoS information to Media Session Handler
- 6c: Non-3GPP access node provides QoS-related information (e.g., DSCP)
- 6d: UE ATSSS steering functionality forwards non-3GPP QoS information to Media Session Handler
- 6e: Media Session Handler performs QoS mapping based on association between non-3GPP and 3GPP QoS characteristics (e.g., DSCP-QCI, DSCP-5QI mapping)
- 6f: Media Session Handler updates mapped non-3GPP QoS parameters to 5GMS-Aware Application

Media Delivery over Non-3GPP Access (Step 7):
- 7a: 5GMS-Aware Application determines media content for non-3GPP access delivery
- 7b: Media playback initiated over non-3GPP access with requested QoS applied
- 7c: M4 media streaming performed over non-3GPP access
- 7d: M4 media flows delivered over non-3GPP access based on requested Dynamic Policy and mapped parameters

Continuation (Steps 8-9):
8. M4 media flows continue over 3GPP access
9. Media Session Handler modifies Dynamic Policy via 5GMS AF to apply to multi-access session

Key Technical Innovations

1. QoS Mapping Framework: Introduces UE-based QoS mapping between non-3GPP access characteristics (e.g., DSCP) and 3GPP QoS profiles (e.g., QCI, 5QI)

2. ATSSS Integration: Leverages UE ATSSS steering functionality as intermediary for QoS information exchange between access networks and Media Session Handler

3. Application-Level Awareness: Enables 5GMS-Aware Application to make informed decisions about media delivery over non-3GPP access based on mapped QoS parameters

4. Dynamic Policy Adaptation: Supports modification of Dynamic Policies to accommodate multi-access scenarios with heterogeneous QoS capabilities

Impact and Consequences

If Approved: Enables consistent QoS support for M4 media flows in multi-access media delivery scenarios, facilitating better steering/switching decisions and GBR QoS flow support across heterogeneous access networks.

If Not Approved: Consistent QoS support for M4 media flows cannot be achieved in multi-access media delivery, limiting the effectiveness of multi-access scenarios with GBR QoS flows.