Bi-directional Power and Trajectory Control for UAV-assisted Cellular Systems

In this paper, we aim to maximize the total uplink and downlink sum-rate by optimizing the trajectory of UAV used as relay base station in an OFDM-based UAV-assisted cellular system. We propose a bi-directional power allocation and trajectory control problem to maximize the total rate with collision avoidance, altitude limitations, and mobility constraints on UAVs. Trajectory control dependent on channel information has problems with unpredictable flight movements due to fast fading channels. This problem can be solved by sequentially processing trajectory control through ergodic SR optimization and power allocation. Numerical results compare the performance of algorithms considering only a single directional problem with the proposed bi-directional problems.