Energy Efficient Air-to-Ground Wireless Networks Using Circularly Orbiting UAVs

Air-to-ground (A2G) wireless networks comprising unnamed aerial vehicles (UAVs) can provide flexible communications services to ground users. However, battery capacity limitations of UAVs affect the stability of the A2G networks. To improve network stability, we propose an A2G Network using Circularly ORbiting UAVs (ANCOR), where UAV base stations (UAV-BSs) always move in circular orbits. ANCOR is based on the fact that hovering UAVs consume more power than moving UAVs. We also propose an arrangement method for the orbits of the UAV-BSs to improve the average energy efficiency, which is defined as the ratio of the average capacity to the average power consumption. The arrangement method comprises two steps. In the first step, the orbits of the UAV base stations are optimized to minimize coverage holes and maximize the minimum capacity in the area. In the second step, the moving speeds of the UAV BSs in orbit are optimized to maximize the average energy efficiency with the user density distribution of the area. Moreover, we evaluate the performance of ANCOR via simulation experiments.