Joint Power Allocation and Beamforming for UAV-Enabled Relaying Systems with Channel Estimation Errors

In this paper, we study an unmanned aerial vehicle (UAV)-enabled half-duplex mobile relaying system with imperfect channel estimation over uncorrelated Rician fading channels. By assuming that the UAV follows a circular trajectory and applying decode- and-forward relaying strategy, we study the joint design of beamforming and power allocation to improve the end-to-end performance, subject to individual and sum transmit power constraints over source node and UAV relay node. First, beamforming results are obtained based on maximum ratio combing in UAV receiving stage and transmit zero-forcing in UAV forwarding stage. And then, statistical power allocation is performed based on obtained beamforming results. In addition, exact closed-form outage probability expressions are derived. Numerical results demonstrate that joint design of beamforming and statistical power allocation can effectively enhance the end-to-end performance.