Improve Stability in UAV Relay Networks by Jointly optimizing Communication, Trajectory and Power

Unmanned Aerial Vehicles (UAVs) have attracted significant interest recently in wireless communication due to their high maneuverability, flexible deployment, and low cost. This paper studies a UAV relay network where the UAV is employed as an amplify-and-forward relay to provide communication service for a group of buoy sensors far off the coast in a three-dimensional (3D) coordinate system. Once a high-speed relay communication link is established, stable transmission is critical. We jointly optimize buoy sensors communication scheduling, UAV trajectory and the system power to minimize the maximum average outage probability among all buoy sensors. The formulated problem is a mixed integer non-convex optimization problem that is difficult to solve in general. We decouple the problem into three sub-problems, which can be iteratively solved by utilizing the inexact block coordinate descent and successive convex optimization techniques. Simulation results show that the outage probability of the proposed algorithm is significantly lower than that of the circle trajectory for the UAV relay.