Tractable Modeling and Performance Analysis of UAV Millimeter Wave Networks With First-Order Reflections

In unmanned aerial vehicle (UAV) networks using millimeter wave (mmWave) in urban environments, dense buildings will cause blockage effects and outage. While reflections become indispensable components and can fairly contribute to the coverage probability in blocked conditions. This letter proposes a tractable model of urban UAV networks with blockage effect as well as first-order reflections and analyzes system coverage probability, where first-order reflection path can be used to recover the communication when direct path is blocked. Specifically, an ellipsoid model is established instead of the planar ellipse model, and the number of tangent points between the ellipsoid and the buildings can quantify the number of first-order reflection paths. In addition, UAV connects to the user by the shortest first-order reflection and the probability density function of its vertical projection length is derived. The results show that utilizing first-order reflections, another 10.6% coverage probability improvement can be achieved on the basis of the optimal direct coverage when the average height of buildings equals 60m.