Joint Trajectory and Power Optimization for UAV Relay Network over Time-Varying Rician Channel

To enhance the reliability of unmanned aerial vehicle (UAV) relay communication systems, a joint optimization method for UAV relay trajectory and transmission power allocation is proposed for time-varying Rician channels. Initially, a signal reception model for the base station-UAV and UAV-user dual-hop links based on the decode-and-forward (DF) protocol is presented. A time-varying Rician channel model related to the elevation angle is established, and a first-order approximation expression for the outage probability is derived, followed by an analysis of the system’s outage performance. Subsequently, based on the criterion of minimizing outage probability, a joint optimization method for trajectory and power allocation is proposed: optimizing the transmission power allocation while fixing the UAV’s heading angle, and then optimizing the UAV’s heading angle while keeping the power allocation factor constant. Finally, simulations validate the correctness and effectiveness of the proposed optimization scheme.