A UAV Real-time Trajectory Optimized Strategy for Moving Users

Abstract

As a supplement of mobile communication in Fifth generation mobile networks (5G), Unmanned Aerial Vehicles (UAVs) are playing an important role in user coverage. When base stations (BSs) are not able to serve all users in hot spots, deployable UAVs are required to mitigate the burden of BSs and maximize the access number of users. Besides, thanks to the controllable mobility, UAVs can provide better coverage for the mobile users with high velocity or fixed direction. Therefore, it is important to solve the problem of the trajectory planing of multiple UAVs. In this paper, we propose a UAV trajectory optimization strategy to maximize the access number of moving users. Firstly, according to the mobility of UAVs and the Signal to Interference plus Noise Ratio (SINR) requirements of users, we formulate the UAV's trajectory optimization problem, which is an atypical mixed integer linear programming problem (MILP). Then, a convex optimization problem is obtained by correlation relaxation of the previous atypical MILP. Finally, we propose a practicable trajectory optimization algorithm with limited times of iteration. The simulation results show that the proposed algorithm can maximize the access number of users while maintaining enough SINR.