The Optimal Deployment of UAV-based NOMA Communication System

Massive connections and higher spectral efficiency requirements are the main challenges for the fifth generation (5G) and beyond 5G (B5G) wireless networks. Unmanned aerial vehicles (UAVs) based non-orthogonal multiple access (NOMA) transmission is one of promising ways which has recently gained significant interests to leverage the strength of line of sight links and improve the coverage as well as maximize the throughput of wireless communications systems. This paper investigates a simplified UAV-enabled wireless system to provide air-to-ground (A2G) connection for two terrestrial users. The paper highlights the performance evaluation based on NOMA and orthogonal multiple access (OMA) schemes in terms of spectral and energy link efficiencies at the two interested users. Then, it aims to find the optimal location for deploying the UAV in which that the system performance has a significant enhancement. Simulation results reveal that the best performance for the both users can be achieved using NOMA transmission scheme. In addition, the undesirable impact of increasing the hovering altitude after the optimal point is less on spectral efficiency performance of the far user based NOMA transmission. Furthermore, the energy efficiency gap between near and far users based OMA transmission decreases as the hovering altitude increases after the optimal point.