In this research topic, we study the radio frequency (RF) power transfer technique that makes use of an electromagnetic (EM) wave as a medium for carrying power. Differently from other wireless power transfer techniques (e.g., inductive coupling and magnetic resonant coupling), the RF energy transfer technique enjoys an advantage of longer energy transfer distance compared to other competing technologies thanks to the characteristics of the EM wave. Especially, we study a multi-antenna wireless-powered sensor network (WPSN), in which a power beacon wirelessly transfers electric energy to a sensor node via an EM wave.

In the coming era of Internet-of-Things (IoT), we are expected to be surrounded by communicating things deployed everywhere in our daily life. This explosive increase of communicating things poses a very challenging problem of high power consumption of current wireless communication technologies. In this research topic, we study a novel ultra-low power wireless communication technology for IoT devices in the cellular long-range communication networks. We adopt an RFID technique such as envelope detection in the downlink and backscattering in the uplink direction. To overcome the short range of RFID communication techniques, we consider a base station equipped with a massive number of antennas for transmit and receive beamforming, and IoT devices with the retroreflective modulation technology.

The visible light communication (VLC) is a new wireless communication paradigm that transfers digital data via visible light spectrum instead of microwave. In VLC, the light emitting diode (LED) is modulated in a very fast speed so that information is embedded in the light while no blinking is perceived by human eyes. In this research, we study a novel architecture that combines the VLC and the RF communication to benefit from the advantages of high data rate and stability at the same time. Moreover, high-speed camera-based VLC for smart car application is studied.