Energy efficient MIMO SWIPT by hybrid analog-digital beamforming

In this paper, we investigate the simultaneous wireless information and power transfer (SWIPT) for MIMO systems with limited RF chains at the base station. We focus on the scenario where there is one information decoder with a targeted SINR and several separate energy receivers with energy harvesting thresholds. Based on the observation that the fully-digital beamformer consists of only the information beamformer, we propose an iterative hybrid analog-digital beamforming scheme, where we design the analog beamformer by minimizing the difference between the fully-digital beamformer and the hybrid beamformer, and the optimal solution can be obtained via a geometrical interpretation. Numerical results show that the proposed scheme can achieve a close-to-optimal performance with significant gains in the total power consumption over fully-digital SWIPT.