# Reply LS on Traffic Model for Immersive Communication

## Document Information

- **Source:** SA WG4
- **To:** RAN WG1
- **Response to:** R1-2509596
- **Release:** Release 20
- **Work Item:** FS_6G_Radio

## Overall Description

SA4 has discussed RAN1 LS R1-2509596 and provides information on the eXR model with Haptics.

### Key Modeling Principles

SA4 establishes the following principles for haptics traffic modeling:

1. **Simultaneous haptics packets over multiple channels can be modeled as one aggregated packet**
2. **Silent periods of haptics do not need to be modeled**
3. **Haptics packets and XR traffic packets can be generated either independently or with correlation**

## Downlink Haptics Traffic Model

SA4 provides a statistical parametric model for downlink haptics traffic based on haptics traces (provided in attachment).

### Statistical Parameters

| Parameter | Unit | Value/Distribution |
|-----------|------|-------------------|
| **Packet size** | byte | Pareto distribution with α=7, range = [504, 1736] bits<br>CDF: F(x) = 1 - (x_min/x)^α, where x_min is the minimum value |
| **Packet inter-arrival time (T)** | ms | Exponential distribution with λ=0.015, min=M<br>Quantized to multiples of M using rounding function (e.g., M=32ms)<br>CDF: F(t) = 1 - e^(-λt) |
| **Jitter** | ms | Follows description in clause 5.1.1.2 in TR 38.838 |
| **PDB** | ms | 30 |
| **Packet Success Rate** | % | 90 |

### Key Characteristics

- Packet sizes follow a **Pareto distribution** (heavy-tailed distribution) with shape parameter α=7
- Inter-arrival times follow an **exponential distribution** with rate parameter λ=0.015, subsequently **quantized to multiples of M** (e.g., 32ms)
- **30ms PDB requirement** with **90% packet success rate**

## Uplink Haptics Traffic Model

For uplink haptics traffic, SA4 recommends **reusing existing models**:

- Uplink haptics mainly involves transmission of **haptic sensor information**
- The **uplink control or pose traffic model** defined in **section 5.2 of TR 38.838** can be reused

## Action Requested

SA4 respectfully requests RAN1 to **take the above information into account** for traffic modeling in immersive communication studies.