  Millimeter wave (mmWave)-based unmanned aerial vehicle (UAV) communication is
a promising candidate for future communications due to its flexibility and
sufficient bandwidth. However, random fluctuations in the position of hovering
UAVs will lead to random variations in the blockage and signal-to-noise ratio
(SNR) of the UAV-user link, thus affecting the quality of service (QoS) of the
system. To assess the impact of UAV position fluctuations on the QoS of
air-to-ground mmWave UAV communications, this paper develops a tractable
analytical model that jointly captures the features of three-dimensional (3D)
position fluctuations of hovering UAVs and blockages of mmWave (including
static, dynamic, and self-blockages). With this model, we derive the
closed-form expressions for reliable service probability respective to blockage
probability of UAV-user links,and coverage probability respective to SNR,
respectively. The results indicate that the greater the position fluctuations
of UAVs, the lower the reliable service probability and coverage probability.
The degradation of these two evaluation metrics confirms that the performance
of air-to-ground mmWave UAV systems largely depends on the UAV position
fluctuations, and the stronger the fluctuation, the worse the QoS. Finally,
Monte Carlo simulations demonstrate the above results and show UAVs' optimal
location to maximize the reliable service and coverage probability,
respectively.

Computation