Self-synchronized Interference Avoidance Method for Far-field WPT System

Recently, far-field wireless power transfer(WPT) for IoT and wearable devices has become increasingly popular. The frequency used for the WPT is also used for wireless-communications hence coexistence should be done not to affect existing communications. Although conventional methods such as CCA (Clear Channel Assessment) and LBT (Listen Before Talk) are not suitable for WPT because multiple WPT transmitters compete with each other and degrading the performance of the system. This article proposes "Synchronous-LBT" that CCA algorithm suitable for WPT and shows by simulation that WPT systems automatically perform synchronous operations with each other. In addition, the simulations show that the proposed method can provide time slots for existing communications and improve transmission power by simultaneous transmitting. We also prototype WPT transmitters and show the effectiveness of the proposed algorithm.