Stochastic Channel Modeling for Flat Fading in Non-Terrestrial Narrowband Systems

In non-terrestrial narrowband systems, the Doppler effects, atmospheric impairments, and multipath propagation show a critical interplay influencing flat fading. Channel modeling accurately is a component that constitutes a crucial element in system design and optimization. LEO satellites are characterized by high-speed movement, and hence, severe Doppler shifts and spreads that imply time-varying channel characteristics degrading communication performance. Also, the presence of atmospheric effects such as rain attenuation, fog, and scintillation causes even further signal degradation especially at higher frequency bands like Ka-band. The problem of multipath propagation caused by reflections and scattering also adds another layer of complexity through random fading variations in the received signal. The challenges require a stochastic modeling approach to characterize flat fading channels in narrowband NTN scenarios. This framework captures the unique propagation dynamics of LEO satellite links by integrating statistical fading models with Doppler and atmospheric effects. Rayleigh fading is utilized for modeling NLOS scenarios, while Rician fading describes the scenario with a dominant line-of-sight component, such as under clear-sky conditions. The simulation results confirm that the proposed approach is also quite accurate and versatile in predicting NTN communication system performance. These results emphasize the necessity of accurate channel modeling in designing robust and reliable non-terrestrial communication systems, paving the way for enhanced connectivity in both terrestrial and remote environments.