IEEE SA P1944: Non-Terrestrial Network Channel Modeling

The IEEE SA P1944 Non-Terrestrial Network Channel Modeling subgroup brings together researchers from academia and industry to examine the limitations of existing satellite channel models and develop recommendations for more transparent, physically grounded, and reproducible modeling approaches.

The initial effort focuses on low-Earth-orbit (LEO) satellite-to-ground links, with potential extensions to UAV links. The subgroup is initially prioritizing link-level channel modeling. System-level models, optical links, inter-satellite links, and coexistence studies may be considered in later phases.

 

Motivation

Many existing non-terrestrial network models extend assumptions originally developed for terrestrial cellular systems. These assumptions do not fully represent several defining characteristics of LEO satellite channels:

  • Significant line-of-sight propagation at higher elevation angles and more diffuse scattering at lower elevations
  • Rapidly changing satellite geometry and large Doppler shifts
  • Large slant ranges and continuously changing elevation angles
  • Geometry-dependent obstruction from buildings, foliage, vehicles, and terrain
  • Atmospheric and ionospheric effects that vary with frequency and elevation
  • Wide-area spatial consistency requirements for mobility, beam switching, and handover studies
  • Limited public measurement datasets and reproducible validation scenarios

These limitations affect downstream simulations of OFDM synchronization, beam tracking, random access, handovers, and other mobility-sensitive procedures.

 

Initial Objective

The subgroup’s first deliverable is an authoritative review of existing NTN channel models and recommendations for future development. This report is intended to document the state of the art, identify unresolved modeling and validation gaps, and provide a technical blueprint for subsequent model-development projects.

Following this review, the group expects to investigate two complementary directions:

  1. Orbit-aware stochastic channel models
  2. Site-specific and ray-tracing-based channel models

 

Prior-Art Review Themes

1. NTN Channel-Model Structures

This theme reviews geometric, stochastic, ray-traced, standardized, and empirical NTN models. It examines which established terrestrial modeling concepts—such as geometry-based stochastic models, clustering methods, and multipath representations—can be adapted to NTN environments.

The review also considers how antenna architecture, including planar and cylindrical arrays, should be connected to the angular and spatial structure of the channel model.

2. Slow and Fast Fading

This theme examines how existing models represent satellite and terminal mobility, time and frequency selectivity, multipath delay and Doppler, shadowing and obstruction, fast and slow fading, angle spread, and polarization.

The initial priority is delay and Doppler behavior arising from mobility and multipath. More detailed MIMO effects may be introduced according to the target scenario.

3. Site-Specific and Ray-Tracing Models

This theme reviews how site-specific NTN models are constructed and which physical effects they include, such as antenna configuration, polarization, building and terrain obstruction, material-dependent reflection and scattering, atmospheric impairments, time-varying geometry, and channel nonstationarity.

The review will also examine whether model configurations and ray-tracing assumptions are documented well enough to permit independent reproduction, benchmarking, and validation.

4. Atmospheric and Ionospheric Effects

This theme studies simulation-oriented and physically resolved treatments of rain, cloud and gaseous attenuation, tropospheric refraction, excess propagation delay, ionospheric scintillation, Faraday rotation, and other frequency-dependent effects.

A central question is whether these components can be combined into a unified and validated NTN modeling pipeline.

 

Open Technical Questions

  • How should the channel model be modularized across mobility, Doppler, delay, shadowing, and fast and slow fading?
  • Which antenna architecture and array assumptions should be adopted?
  • How should spatial consistency be enforced across large geographic areas?
  • Which measurements, hardware platforms, and public datasets can support validation, particularly at Ku- and Ka-band?
  • How should standardized, stochastic, and site-specific models be compared using common scenarios and metrics?

 

FUNLAB Supporting Research

FUNLAB is investigating simulation tools and methods that can support the subgroup’s technical goals. Current research includes:

  • Orbit propagation using SGP4 trajectories
  • Doppler-aware channel generation from satellite position and velocity
  • Site-specific channel modeling using Sionna RT
  • Integration of ray-tracing-derived channel information into ns-3
  • Channel impulse responses sampled at orbital or elevation waypoints
  • Within-waypoint channel evolution using Doppler, angle-of-arrival, and angle-of-departure information
  • Benchmarking against stochastic models and 3GPP-based channel assumptions
  • Evaluation of material, polarization, K-factor, and RMS-delay-spread behavior

Because continuous ray tracing at every ns-3 simulation interval is computationally expensive, the current integration concept obtains high-fidelity channel samples at selected waypoints and evolves or interpolates the channel between them.

 

Participants and Contributors

  • Sumit Roy — University of Washington
  • Xose Rodríguez-Piñeiro — Tongji University
  • Abla Kammoun — King Abdullah University of Science and Technology
  • Ashutosh Balakrishnan — Télécom Paris
  • Shijian Gao — Hong Kong University of Science and Technology (Guangzhou)
  • Zhenlin An — University of Georgia
  • Raghunandan Rao — Indian Institute of Technology Gandhinagar
  • Harsh Verma — Sanyark Space
  • Mike McLernon — MathWorks
  • Kuan-Po Chiu — University of Washington
  • Aaron Buck — University of Washington

 

Resources

 

Current Status

The prior-art review is underway, with working materials and code organized through shared repositories. Subsequent updates will document the review results, modeling recommendations, reproducible simulation scenarios, software artifacts, and validation activities.