Understanding Concurrent Radiative Wireless Power Transfer in the IoT: Out of Myth, into Reality

Radiative wireless power transfer plays a vital role in addressing the challenges facing today's Internet of Things. Challenges include frequent battery replacement, excessive electronic waste, and autonomous operation in hard-to-reach places. Concurrent charging is a fundamental pattern in radiative wireless power transfer where multiple chargers transmit energy waves concurrently, or the signals are received by multiple nodes simultaneously. However, its system model has yet to be understood, and many widespread assumptions ("myths") -- such as constant power density in the time domain, neglected antenna type, and non-interference between neighboring devices -- are unrealistic. This article aims to experimentally discover the truth about these myths. Firstly, extensive results indicate that instantaneous received power in the time domain fluctuates heavily due to imperfect matches between multiple transmitters. Secondly, the extent to which antenna type affects concurrent charging is investigated. Thirdly, energy interference among neighboring devices is identified, and its interference pattern is explored for the first time. Finally, inspired by new findings, insights from the above three perspectives are given.