A wireless sensor network is considered a game changing technology. Currently, the power of the sensors is limited by the limits of the batteries. This chapter investigated wireless power transfer (WPT) via radio wave or microwave for a batteryless and wireless sensor network. In this study, a WPT assisted ZigBee was proposed as a low power wireless sensor. In particular, to suppress the interference between the WPT and the wireless communication, a time division duplex WPT (TDD-WPT)was proposed to enable the coexistence ofWPTand ZigBee on the same frequency band. A scheduled TDD-WPT that can automatically transmit wireless power between the wireless communication devices was suggested and examined through an experiment.