Multi-UAV Wireless Networks: Jointly Trajectory Optimization and Resource Allocation

Unmanned aerial vehicles (UAVs) have attracted considerable interest in assisting wireless communication due to their mobility, flexibility, easy deployment, and lower cost. This paper investigates a multi-UAV-enabled wireless communication system, where multiple UAV aerial base stations are employed to serve a group of user equipment (UEs) on the ground. We maximize the total uploaded rate of the overall ground UEs in the uplink transmission, by optimizing the communication association between the UAVs and UEs jointly with the UAV's trajectory and transmit power. The formulated problem is a mixed-integer non-convex optimization problem that is challenging to solve. Therefore, we propose an efficient iterative algorithm for solving the problem on a time-slot by time-slot basis, by applying the successive convex optimization techniques. Specifically, the UAVs-UE association, UAVs trajectory, and transmit power are alternately optimized in each iteration to find a reduced complexity solution for the problem. To further reduce the complexity, we assume fixed UE transmit power and find a closed-form expression of the optimal UAVs-UEs associations.