When a wireless and batteryless sensor is powered by microwave power transmission technology, time scheduling is required if wireless communication and power transmission use the same radio frequency band. In addition, constant energy should be stored in the capacitors of the wireless sensor. This paper reports designing a method to allocate periods for microwave power transmission and WLAN communication. Microwave emission is stopped when the WLAN terminal transmits the data and receives beacons transmitted from an access point. The WLAN terminal controls sleep period depending on the remaining energy to store constant energy in the capacitor of the WLAN terminal.