3-D Beamforming for Flexible Coverage in Millimeter-Wave UAV Communications

Unmanned aerial vehicle (UAV) communications can provide high capacity, long transmission distance, and large coverage range in the future air-to-ground networks. Due to the mobility, the target coverage area of a UAV may change frequently, which requires flexible beamforming. Thus, millimeter-wave (mmWave) beamforming with a phased-array is preferred in UAV communications due to the small size and power efficiency. In this letter, we explore 3-D beamforming for mmWave UAV communications with a phased uniform planar array. To realize a flexible coverage, we first take the coordinate transformation of a target area and obtain a minimum rectangular which can cover the target area. Then, we use the subarray technique to design a wide beam to cover the rectangular. Simulation results show that the proposed approach can achieve flexible beam coverage for any type of target area, and the beamforming gain is mainly concentrated in the target coverage area.