TDM Scheduling Based on Receiver Grouping for Indoor Wireless Power Transfer

In wireless power transfer (WPT) systems, multiple-input single-output (MISO) signal processing enhances the power transfer efficiency by optimizing array antenna weight vectors according to channel coefficients between the transmitter and receivers. In a MISO-based WPT system, a time division multiplexing (TDM) scheduling should be jointly optimized; transmitter periodically switches weight vectors for receivers by assigning a time slot to each weight vector. This paper proposes a receiver grouping strategy for TDM scheduling to improve the fairness and efficiency of the WPT system. Receivers with correlated channel conditions are classified into a group because the transferred energy with a beamforming weight directed to a certain receiver is supplied to other receivers, which is called beneficial interference. Beamforming weight vectors are derived to maximize the harvested energy of each group. The time slots duration assigned to weight vectors is then optimized to maximize the minimum harvested energy among receivers. The simulation experiments in an indoor multipath environment reveal that the proposed method improves the minimum and average harvested energy.