A Geometry‐Based Stochastic Channel Model and Beam Domain Transformation for Satellite‐to‐UAV Communications

ABSTRACT

Satellite communications are pivotal to realising the global coverage vision of 6G. This paper proposes a general three‐dimensional (3D) geometry‐based stochastic model for satellite‐to‐unmanned aerial vehicle (UAV) channels, covering S‐band to millimeter wave and incorporating spatially consistent large‐scale parameters (LSPs) dependent on environment, frequency, and satellite elevation angle, as well as ionospheric and rain attenuation. A beam domain channel model is further derived via unitary transformation for low‐complexity beam‐level characterisation. Simulation results indicate that rainfall significantly deteriorates channel characteristics: heavy rain at 50 mm/h introduces approximately 30 dB additional effective path loss, accelerates temporal autocorrelation function decay, and increases root‐mean‐square delay spread. The proposed models provide a theoretical basis for 6G satellite‐to‐UAV system design and optimisation.