Analysis of energy transfer efficiency in UAV-enabled wireless networks

Wireless power transfer (WPT) is a promising charging technology for battery-limited sensors. In this paper, we study the energy transfer in a wireless network using an unmanned aerial vehicle (UAV). Instead of charging the remote wireless sensors directly from the access point (AP), we study the schemes of using a UAV to charge the remote wireless sensors after it is charged by the AP. To this end, two schemes are proposed. The performances of these two schemes are examined and compared with the conventional scheme without using a UAV. A distance threshold beyond which the new schemes have superiority over the conventional scheme is derived by solving energy equations. Numerical results show that the proposed schemes can achieve significantly higher energy efficiency than the conventional scheme when the transmission distance is within the derived critical range.