Wireless powered UAV relay communications over fluctuating two-ray fading channels

The unmanned aerial vehicle (UAV) relay has recently attracted a large amount of research interests, due to it's relative ease of development to enhance cooperative communication performance when the direct link between transmitters and receivers is severely blocked. With simultaneous wireless information and power transfer, the UAV relay can harvest energy from radio frequency and prolong the network lifetime. In this paper, we use the time-switching relaying protocol for UAV energy harvesting (EH) and data forwarding. Different from prior works, the ground-to-air links are modeled as fluctuating two-ray fading channels, which provide a very good fit to the UAV relay communication. In addition, we obtain novel exact analytical expressions for the outage probability, symbol error rate and average capacity of the considered system employing decode-and-forward and amplify-and-forward protocols, respectively. Furthermore, we offer valuable insights into the impact of system and fading parameters on the performance. For example, the optimal EH time can be selected to enhance the system performance. Finally, numerical results are provided to validate the derived results.