Dynamic RF Charging of Zero-Energy Devices via Reconfigurable Intelligent Surfaces

Communication networks can achieve self-sustainability with the help of reconfigurable intelligent surfaces (RIS) that direct electromagnetic waves toward zero-energy devices (ZEDs) for energy harvesting. The harvested energy charges the ZEDs’ batteries, reduces their dependency on external energy sources and enables energy neutrality. In this letter, we propose a dynamic algorithm that adjusts the joint RIS and TX phases based on the battery levels to maximize a weighted-sum power metric favoring ZEDs with lower battery levels. The simulation results show that threshold-based weighting slightly underperforms compared to the weighting with optimal parameters while requiring less data exchange with the network entity manager.