UAV-Aided Backscatter Networks: Joint UAV Trajectory and Protocol Design

This paper investigates unmanned aerial vehicle (UAV)- aided backscatter communication (BackCom) networks, where the UAV is leveraged to help the backscatter device (BD) forward signals to the receiver using transmit- backscatter (TB) protocol. Our goal is to maximize the system ergodic capacity by jointly optimizing the time allocation, reflection coefficient and UAV trajectory. The resulting optimization problem is shown to be non-convex, which is challenging to solve. We consider two different circuit power consumption models, namely dynamic and static models. We first consider the dynamic model, and decompose the original problem into three sub- problems, and an iterative algorithm is proposed to optimize three subproblems alternately by leveraging the block coordinate descent method and successive convex approximation (SCA) techniques. In addition, for the static model, we obtain the optimal time allocation with a given reflection coefficient and UAV trajectory and the optimal reflection coefficient with low computational complexity using the Lagrangian dual method. Simulation results show that the proposed scheme is able to achieve significant throughput gains over the compared benchmarks.