Contents I. Introduction
Conventional wireless networks such as sensor networks and cellular networks are generally powered by batteries, which have limited energy supply capacity and need periodically either to be exchanged with new ones or to be recharged from alternating current (AC) power supply. Therefore, the battery capacity has been considered an important performance indicator, and enhancing the capacity is essential to extend the lifetime of wireless networks. Wireless energy transfer using radio frequency (RF) radiation, which is captured by receiver antenna(s) and recharges batteries, has been proposed to prolong the network lifetime [1]–[5]. There have been two different approaches to harvest energy in point-to-point communications: power splitting [6], [7], and time switching [7], [8]. In the power splitting, the receiver detects information and harvests energy through the received signal at the same time, whereas in the time switching, the receiver switches between information detection and energy harvesting.
