Wireless powered communications refer to the communications systems where the power of the communications device is supplied via wireless power transfer. This method is particularly useful for energy‐constrained systems, such as a remote sensor or a mobile phone. In such systems, without wireless power transfer, when the battery is drained or the mains power is disconnected, the communications device will have to stop operations. Figure 6.1 shows some scenarios where wireless power can be used. In these cases, it is impossible or too costly to replace the battery of the device. Hence, wireless power transfer will be a good solution.
In general, energy harvesting wireless communications use different media to carry energy and information. For example, the communications device could harvest the solar power and then use the harvested solar power to send information via radio waves. One unique characteristic of wireless powered communications is that energy and information are often carried by the same wireless media. This saves the hardware cost.
There are many different sources of energy. There are also many different types of wireless systems. Thus, wireless powered communications can be implemented in different forms. For example, in Wang et al. (2015