High Altitude Air-to-Ground Channel Modeling for Fixed-Wing UAV Mounted Aerial Base Stations

This letter models the high-altitude air-to-ground (A2G) channel for aerial base stations (BSs), which are carried by fixed-wing unmanned aerial vehicles (UAVs). Different from ground BS, fixed-wing UAVs have to periodically hover to provide coverage to ground users (GUs), which may result in the instability of A2G wireless links. On the one hand, pathloss is modeled as a function of distance from UAV to GUs, which includes hover radius and flight altitude, and the elevation angle of GUs. On the other hand, the model of multipath and shadow (MS) fading is dependent on the elevation angle as well. Specifically, we show that generalized Gamma distribution is suitable to model MS fading under large elevation angle, while log-normal fading is suitable otherwise. Moreover, we further investigate the spatial-temporal correlation of the A2G channel, which is shown to depend on the movement distance/direction of GU and the distance from GU to the hover center.