Measurement-Based Channel Characterization of Air-to-Ground Propagation for UAV in Coastal Beaches

In this paper, a miniaturization-and-lightweighting air-to-ground (A2G) channel measurement system is developed based on the software-defined radio (SDR) platform. Utilizing the system, low-altitude A2G channel measurements are conducted in a coastal beaches environment over a 1-kilometer flight distance at the carrier frequency of 1.5 GHz. The collected measurement data is statistically analyzed, and a fitted channel model is proposed. The fitted results are then compared with the free space path loss (FSPL) model and the flat earth two ray (FETR) model, which considers the electromagnetic characteristics of ground reflection points. The error analysis is performed from the perspectives of link distance and the pitch angle between the UAV and the ground station. The results demonstrate that the fitted model provides greater reliability than the FSPL model and the FETR model. Moreover, in the medium pitch angle region, the two-ray model that accounts for actual electromagnetic characteristics exhibits higher accuracy.