Trajectory Optimization Methods of the OFDM-UAV Cascade Relay Communication System

Unmanned Aerial Vehicle (UAV) cascading relay communication can achieve more extensive, efficient, and secure wireless communication services. In this paper, we consider a UAV cascading relay communication system with frequency-selective fading channels, and propose two UAV trajectory optimization methods that are joint and stepwise trajectory optimization based on orthogonal frequency division multiplexing (OFDM). First, the OFDM-UAV cascade relay communication transmission model is provided, and the probability of system interruption is theoretically analyzed and an approximate calculation formula is derived. Then, based on the principle of minimizing the probability of system interruption, the joint and stepwise trajectory optimization methods are proposed. Finally, the computer simulation results demonstrate the validity and correctness of the proposed trajectory optimization methods. It is proved that the OFDM-UAV cascade relay communication system can effectively overcome frequency-selective fading, and the two proposed trajectory optimization methods have similar interruption performance.