The Throughput and Energy-Efficiency Maximization in UAV-Enabled Mobile Relaying System

Employing unmanned aerial vehicles (UAVs) relay to provide wireless connectivity in areas without infrastructure coverage has brought significant interests recently due to its flexibility, fast reactions and low-cost. This paper proposes an energy efficient rotary-wing UAV-enabled relaying system. By considering time-division duplexing (TDD) based decode-and-forward (DF) relaying, the semi-circular trajectory is adopted when the obstacles such as high mountains block the Line-of-Sight link between communication nodes. By using the iterative algorithm, we maximize the throughput in bits/second/Hz as well as energy efficiency (EE) in bits/Joule of the considered system by jointly optimizing the time allocation, flying trajectory and speed of the UAV relay. The proposed algorithm is superior to the benchmark schemes in terms of improving the energy efficiency (EE) and transmission rate, which proves that the proposed algorithm can effectively improve the EE of UAV-enabled mobile relaying system.