# Summary of S4-260258: Application Scenario for Real-time Peer to Application to Peer Communication

## Document Overview

This contribution to TR 26.836 (Study on QUIC-based media delivery for real-time communication and services) proposes the addition of a Peer to Application to Peer (P2A2P) application scenario for evaluating QUIC-based media delivery protocols in real-time communication services. The document references existing 3GPP specifications (TS 23.228 and TS 26.114) as the basis for this scenario.

## Main Technical Contributions

### 1. Reference Updates

The CR adds three new normative references to support the P2A2P scenario:

- **TS 26.506**: 5G Real-time Media Communication Architecture (Stage 2)
- **TR 26.113**: Real-Time Media Communication; Protocols and APIs  
- **TR 22.870**: Study on 6G Use Cases and Service Requirements

### 2. P2A2P Application Scenario Definition (New Clause 5.2.1.1)

#### 2.1 Core Architecture Description

The scenario describes an RTC session where:

- User A establishes a session to an Application Server (AS) rather than directly to User B
- A **SWAP server** (defined in TS 26.113) terminates the SDP offer from User A and initiates a second SDP offer towards User B
- The AS terminates media from User A and forwards it to User B, acting as an intermediary
- Leverages the **GA4RTAR service architecture** (TS 26.506) where the AF triggers appropriate AS based on service logic

#### 2.2 Media Handling Characteristics

The AS is characterized as a **media-aware entity** that actively processes real-time media streams:

- Decodes, analyzes, modifies, or regenerates media before forwarding
- Supports value-added services: call screening, IVR, real-time translation, media mixing, conferencing
- Must maintain conversational latency bounds per TS 26.113
- Ensures synchronization between media components (e.g., voice and RTT)
- Provides graceful adaptation to packet loss or bandwidth variation

### 3. Real-Time Communication for Conversational XR Services Use Case (New Clause 5.2.1.1.2)

#### 3.1 General XR Communication Framework

Describes RTC augmented by shared XR scenes with:

- User representation via 2D/3D avatars or holograms
- Multi-modal immersive experience through multiple XR devices (glasses/headset, immersive audio, haptics)
- **Main XR Scene Manager** located in Media Function (MF) of AS, responsible for maintaining synchronized XR scene for all participants
- Interactive virtual objects within the XR scene

#### 3.2 Deployment Configurations

Three participant configurations are defined:

1. **Full VR**: All participants remote, represented by avatars in common virtual 3D environment
2. **Full AR**: All participants local, common XR scene inserted into physical conference room using AR technology
3. **Hybrid**: Mix of local and remote participants; XR scene inserted for local AR viewing, remote participants represented by avatars

#### 3.3 Specific Use Cases from TR 22.870

Three detailed use cases are referenced:

**Seamless Immersive Reality in Education (Clause 9.5)**
- Supports local, hybrid, or fully immersive classroom configurations
- Virtual objects for learning enhancement

**Seamless Holographic Telepresence in Healthcare (Clause 9.8)**
- Highly immersive real-time interactions between patients and medical practitioners
- Recreates physical co-presence using holograms, avatars, and multi-sensory media
- Requires synchronized multi-modal data streams (video, audio, haptics, motion, volumetric data)
- Supports six degrees of freedom (6DoF)
- Emphasizes security and privacy for sensitive biometric information (facial features, voiceprints, gestures, health signals)

**Personalized Interactive Immersive Guided Tour (Clause 9.12)**
- Combines location-aware MR/XR with avatars and multi-modal interaction
- Remote touristic guide represented by personalized avatars
- Heterogeneous 5G/6G-connected devices (AR glasses, XR headsets, smartphones, haptic wearables, immersive audio)
- Personalized experience: individual choice of immersion level, devices, language, avatar appearance, content type
- AI-based analysis of gaze, facial expressions, and behavior for contextual content adaptation
- Rich XR features: 2D/3D video, volumetric video, 6DoF movement, immersive audio, tactile feedback
- Supports both indoor and outdoor locations

## Technical Significance

This CR establishes P2A2P as a relevant application scenario for evaluating QUIC-based media delivery in RTC services, particularly emphasizing:

- Media processing at intermediary AS nodes rather than pure end-to-end delivery
- Complex multi-modal XR communication requirements
- Need for synchronized, low-latency media handling with active processing
- Support for diverse deployment configurations and personalization
- Integration with GA4RTAR architecture and SWAP server functionality