Channel Estimation for UAV-Enabled mmWave Massive MIMO Communications

The Doppler frequency shift caused by the high mobility of unmanned aerial vehicles (UAVs) can seriously degrade the performance of communication systems. In this paper, we propose an angle of arrival (AOA) estimation method with Doppler shift compensation for the UAV-enabled millimeter-wave (mmWave) system which is equipped with a large-scale uniform linear array (ULA) and used to serve multiple users simultaneously. Specifically, we apply discrete Fourier transform (DFT) and phase rotation methods to estimate the Doppler shift. Besides, combined with the orthogonal pilot matrix, we can derive the channel state information (CSI), Doppler shift, and AOA of each user well. Finally, simulation results are provided to corroborate our proposed studies.