The Era of Wireless Information and Power Transfer

In recent decades, the rapid development of wireless communication technologies has triggered a massive growth in the number of wireless communication devices for various practical applications, including e-health, autonomous control, logistics and transportation, environmental monitoring, energy management, safety management, etc. It is expected that in the era of the Internet of Things (IoT), there will be 50 billion wireless communication devices connected together worldwide via the Internet with a connection density of 1 million devices per km2 [1]. In particular, small wireless sensor modules will be unobtrusively and invisibly integrated into clothing, walls, and vehicles at locations which are inaccessible for wired/manual recharging. However, battery-powered wireless communication devices have limited energy storage capacity and their frequent replacement can be costly, cumbersome, or even impossible (e.g., biomedical implants), which creates a serious performance bottleneck for realizing reliable and ubiquitous wireless communication networks. A promising approach to prolong the lifetime of traditional wireless communication systems is to let the wireless communication devices harvest energy from the environment [2–4]. For example, solar, wind, and