Performance Analysis of Random 3D mmWave-Assisted UAV Communication System

Recently, millimeter-wave (mmWave) and unmanned aerial vehicle (UAV) communication have attracted considerable attention owing to their advantages in terms of high data rates, low latency, and seamless coverage. However, mmWave-UAV communication performance is significantly compromised by the mmWave molecular absorption and UAV movement, resulting in a drastic deterioration in the performance and even potential disruptions in communication links. In this study, we propose a three-dimensional (3D) mmWave-assisted UAV communication system that considers both mmWave molecular absorption and UAV movement. We utilize the Nakagami-$m$ distribution to model the fading of the mmWave link, and a 3D cylindrical region model to depict the mobility of the UAV. To comprehensively characterize the random movement of the UAV, the proposed system incorporates distribution models in both horizontal and vertical directions. Furthermore, the cumulative distribution and probability density functions of the signal-to-noise ratio for the proposed system are derived. We also derive closed-form and asymptotic expressions of outage probability, average bit error rate, and ergodic capacity. Monte Carlo simulations are conducted to validate the accuracy of the derived expressions. The results show that the extension of the cylindrical region and the increase in mmWave molecular absorption lead to a decrease in the performance of the mmWave-assisted UAV communication system. In addition, the diversity order for the system is obtained to gain further insight. It is demonstrated that the diversity order is affected by the Nakagami fading parameter, the molecular absorption coefficient, and the height and radius of the cylinder.