Читать книгу Autonomous Airborne Wireless Networks - Группа авторов - Страница 20

Airframe shadowing occurs when the LoS of AG propagation is obstructed by the UAV structure. This impairment is unique to UAV communications for both AA and AG channels and does not exist in conventional cellular communications. Airframe shadowing is more severe in fixed‐wing UAVs mounted with single antenna. In this case, the AG communication link can be severe during roll, pitch, or yaw motion of the UAV. One possible solution to alleviate airframe shadowing is to replace the single‐antenna system with spatially separated multiple antennas. Other factors responsible for airframe shadowing are the size, shape, and material of the UAV. The seminal work on the measurement of airframe shadowing was performed in [48], which found that the aircraft roll angle was proportional to the shadowing attenuation. Moreover, shadowing duration depends on the flight maneuvering.