Trajectory Design for Throughput Maximization in UAV-Assisted Communication System

In this paper, we study an unmanned aerial vehicle (UAV) assisted communication system to provide service to the ground users. We address the problem of UAV deployment in three-dimensional (3D) space to provide on-demand coverage to the users such that their sum rate is maximized. First, we find the optimal UAV location in 3D space where the sum rate is maximized for all ground users. Thereafter an optimal trajectory is designed for the UAV to travel from the initial to the optimal location, such that the overall average sum rate during the flight is maximized while meeting the on-board energy availability and flight duration constraints. The problem formulated is non-convex. To obtain the optimal location, we approximate the rate expression to obtain the concave regions and apply alternating optimization. An iterative scheme is proposed to obtain the optimal UAV trajectory, which computes the optimal location in each time slot sequentially, followed by a greedy approach to reach the final location. Simulation results provide useful insights into the optimal location and the UAV trajectory problem and show on an average 16.5% improvement over the benchmark schemes.