Time-Frequency Scheduling and Power Optimization for Reliable Multiple UAV Communications

Unmanned aerial vehicle (UAV) communication has gained increasing interests from the industry and academia as UAV has a variety of emerging applications, such as aerial sensors, flying base stations, and mobile relays. Generally, UAVs are manipulated by remote ground control center. Thus one critical issue is that UAVs must correctly receive the control signal before following the instructions. However, the control signal quality at UAV receivers is very susceptible due to the variation of channel conditions and the effect of adjacent channel interference. To tackle these challenges, this paper investigates the issue of how to simultaneously ensure the reliability of the remote control signal for multiple UAVs. The problem is formulated as a mixed-integer programming with the goal of maximizing the minimum signal to interference-plus-noise ratio of all UAVs by jointly scheduling the time-frequency resource blocks and optimizing the power allocation. To make the problem tractable, we perform equivalent transformations via leveraging the inherent property of the formulated problem. Next, based on the decoupled constraints on different variables, we propose a low complexity block coordinate descent-based method. Furthermore, to offer better system performance, we leverage the smooth approximation theory and develop a gradient projection-based method. Finally, extensive simulation results demonstrate the effectiveness of the proposed methods under various parameter configurations.