Optimum Deployment of UAV Relaying with Mobile Ground User System

The usage of unmanned aerial vehicles (UAVs) as aerial base station (BS) or relay are becoming increasingly important in the yield of wireless communications. An UAV-based relay can greatly support the transmission between the mobile ground user (MGU) and the base station. In this paper, we study the optimum altitude of a decode-and-forward (DF) relaying UAV system. In particular, we analyze two different communication scenarios, i.e., BS-UAV-MGU (BUM) and MGU-UAV-MGU (MUM) scenarios, respectively. For the BUM scenario, the optimum altitude of UAV-based relay over Mixed-Rayleigh fading channel is studied. For the MUM scenario, we analyze the performance of a two-hop network over the Double-Rayleigh fading channel with the assistance of a DF relay. Moreover, the average end-to-end bit error rate (BER) and outage probability of the proposed UAV-relay system are analyzed for both BUM and MUM scenarios. Additionally, we provide closed-form expressions of outage probability and BER for BPSK modulation and demonstrate the accuracy of proposed expressions via Monte-Carlo simulations.