Summary of 3GPP Change Request S4-260229

Document Information

• Source: InterDigital Pennsylvania
• Title: Description of experimental approach and test setup for Conversational XR real-time communication
• Specification: 3GPP TR 26.823 v0.2.0 (FS_DCTC_eQoS_MED)
• Purpose: Agreement

Background and Motivation

This CR addresses the currently empty Clause 6.1.1 of TR 26.823, which focuses on the Study on dynamically changing traffic characteristics and usage of enhanced QoS support in 5GS for media applications and services. The study examines various use cases including real-time communication, streaming, short-form video download, and media upstream for AI inferencing.

The contribution specifically targets the real-time communication for Conversational XR scenario, providing a complete experimental framework based on InterDigital's XR platform for traffic measurement associated with QoE metrics.

Main Technical Contributions

Experimental Approach (Clause 6.1.1.1)

The proposal introduces a standalone custom client/server XR platform for simplified emulation of real-time communication for conversational XR with the following key features:

Platform Capabilities

• Control of transmission/reception of XR data at both client and server sides in uplink and downlink
• Measurement of QoE metrics including:
• Pose-to-render-to-photon latency
• Roundtrip-interaction delay
• Measurement of uplink/downlink traffic characteristics

Architecture Design

• Client side: Generation and transmission of user's XR data (pose information, actions, real environment data)
• Server side: Management of XR scene, generation and transmission of resulting XR scene data (scene state for local rendering, media)

Measurement Methodology

• Per-packet metadata insertion in both uplink and downlink flows for latency QoE metrics measurement
• Packet marking with timing information to enable end-to-end latency measurement
• Correlation between uplink packets (e.g., pose information) and corresponding downlink packets (e.g., scene state)

Testing Phases

1. Baseline measurements on wired network (ideal network conditions)
2. 5G network emulation using test channels or emulated 5G network with:
3. Deterministic, controllable, and reproducible conditions
4. Real-time typical radio and capacity conditions
5. Impact assessment of delays and packet losses

5G Network Conditions

The approach considers multiple network scenarios:
- Nominal conditions
- Cell-edge conditions
- System load in multi-UE scenarios

Test Setup (Clause 6.1.1.2)

The proposal defines a comprehensive test setup with detailed observation points:

Client-Side Custom XR Application

Functions include:
- Generation and transmission of user's data with metadata for QoE metrics measurement to remote Scene Manager
- Reception of resulting XR scene data with metadata
- Rendering and display of XR scene

Server-Side Custom XR Application

Functions include:
- Reception of user's data with metadata
- XR scene updates and QoE metrics collection
- Transmission of resulting XR scene data with metadata

Observation Points Architecture

Five observation points are defined for comprehensive measurement:

Network-Level Observation Points:
1. Network_UE_OP (UE side):
- 5G network emulator ingress for uplink XR data
- 5G network emulator egress for downlink XR data

1. Network_UPF_OP (UPF side):
2. 5G network emulator egress for uplink XR data
3. 5G network emulator ingress for downlink XR data

Application-Level Observation Points:
3. Client_Application_OP_1 (client side):
- Measurement of round-trip QoE metrics (pose-to-render-to-photon, roundtrip-interaction delay)

1. Client_Application_OP_2 (client side):

2. Measurement of inter-flow time synchronization QoE metrics in downlink

3. Server_Application_OP (server side):

4. Measurement of inter-flow time synchronization QoE metrics in uplink

Measurement Tools and Techniques

• Traffic characteristics measurement: IP packet analysis using open-source network protocol analyzer (e.g., Wireshark)
• Dual-point measurement: Both ingress and egress of 5G network emulator to:
• Highlight network performance impact on traffic characteristics
• Identify application/transport level impacts from network performance through variability analysis

Technical Significance

This contribution provides a complete experimental framework for evaluating conversational XR real-time communication, enabling:
- Systematic measurement of dynamic traffic characteristics
- Assessment of QoS feature benefits in 5G systems
- Correlation between network conditions and QoE metrics
- Reproducible testing methodology for standardization purposes