Ray-tracing Simulation and Hybrid Channel Modeling for Low-Terahertz UAV Communications

Unmanned Aerial Vehicles (UAVs) are currently playing an important role in both military and commercial applications. While UAVs possess potential to enhance network coverage with their high flexibility, combining with the Tera-hertz (THz) band is promising to enhance the wireless data rate with abundant spectrum resources and ultra-high bandwidth. As a fundamental challenge, air-ground (AG) channel modeling and analysis in the THz band are investigated in this paper, based on ray-tracing simulation and hybrid modeling approaches. The channel statistics are extracted and analyzed based on ray-tracing simulated data, including path loss, excess delay, among others. In particular, the height dependence of statistical parameters is thoroughly analyzed, which shows a clear trend of increasing channel sparsity with high-altitude UAVs. In light of the simulated data and analysis, a hybrid channel model including the line-of-sight, ground-reflection path, and stochastically generated multi-path, is proposed to characterize the THz AG propagation, for which the fading characteristics are validated.