Joint Caching, Communication, and Trajectory Optimization in Air-Ground Integrated Wireless Networks With Multiple UAVs and Multiple BSs

Using unmanned aerial vehicles (UAVs) to improve the network performance has been widely discussed due to their high agility for deployment and better line-of-sight (LoS) channels. To further improve the efficiency of using UAVs to improve the network, this paper investigates the optimization of cache-enabled air-ground integrated networks where multiple UAVs and base stations (BSs) jointly serve users. Aiming to maximize the minimum user rate of the network, we first formulate two optimization problems. The first problem considers jointly optimizing the user scheduling and association, UAV power allocation, bandwidth allocation, and UAV trajectories when the caching placement is pre-determined, and the second problem further jointly optimizes the caching placement. To solve these two problems, we propose to decompose them into sub-problems, and then solve the sub-problems iteratively to obtain the solutions. The solution approaches of each sub-problem are provided. In addition, convergences of the proposed approaches are analyzed. Simulation results show that our proposed approaches perform well and outperform the reference schemes.