Trajectory Optimization for UAV-Enabled Amplify-and-Forward Relaying System Based on Communication Performance

In this paper, we discuss an unmanned aerial vehicle enabled Amplify-and-Forward Relaying System, where a fixed-wing UAV flies is used as mobile relay, and circular trajectories are set. The system employs a fixed-wing UAV to ferry data from source node to destination node with limited energy consumption. We also choose the amplify-and-forward (AF) as the method of cooperative communication. By adjusting the orbital radius to minimize the propulsion energy consumption of UAV while contenting the communication throughput requirement. To save this, we transform the problem into a discretized equivalent, and discuss its optimal solution depends on whether the problem is convex. By using the algorithm and analyzing the function monotonicity and extremum to get the conclusion. Numerical results show that the precise orbital radius could significantly improve communication performance. And the proposed cache-enabled AF strategy model can provide more communication throughput in the same case, compared to the no cache-enabled AF strategy.