Adaptive Limited Feedback Designs in MIMO Broadcast Systems with Simultaneous Wireless Information and Power Transfer

This paper studies an adaptive limited feedback design in a multi-user downlink broadcast channel (BC) for simultaneous wireless information and power transfer. The objective is to maximize the sum-rate of information decoding (ID) users while maintain an minimum energy harvesting (EH) constraint for each EH user. For limited feedback environments, a total feedback bit constraint is applied at the base station and each user adopts a codebook to quantize the normalized channel state information (CSI). We first present a beamforming design for the case of one EH user and one ID user. In addition, for multiple UEs, we propose a sub-optimal beamforming design which generates a dedicated beam for each user and has low complexity. Also, we derive closed-form expressions of the achievable sum rate of the ID users and present an adaptive mode selection algorithm under different EH constraints and total number of feedback bits. Finally, simulation results verify the effectiveness of our proposed schemes.