Movable Antenna-Assisted MIMO SWIPT: Joint Precoding and Antenna Position Optimization

Movable antenna (MA) technology has recently emerged as a promising paradigm to flexibly reshape wireless channels, thereby enhancing system performance beyond the limits of traditional fixed-position antennas (FPAs). In this paper, we investigate an MA-assisted multiple-input multiple-output (MIMO) simultaneous wireless information and power transfer (SWIPT) network, where an access point (AP) equipped with multiple MAs serves both multi-FPA information decoding users (IDUs) and multi-FPA energy harvesting users (EHUs). Our objective is to maximize the weighted sum harvested power of all EHUs by jointly optimizing the transmit precoding matrices and the positions of MAs, subject to the constraints on the maximum transmit power of the AP, quality of service of each IDU, confined MA moving region, and minimum inter-MA distance. To tackle the non-convexity of this problem, we first transform the original optimization problem into a more tractable equivalent form by leveraging the weighted minimum mean square error (WMMSE) approach. Next, we start with the single-IDU single-EHU scenario and propose an efficient block coordinate descent (BCD) algorithm. Specifically, the transmit precoding matrix and MA positions are iteratively optimized based on the successive convex approximation (SCA) technique. The proposed algorithm is then extended to the general multi-IDU multi-EHU scenario. Finally, simulation results show that the proposed MA-assisted MIMO SWIPT system significantly outperforms conventional FPA systems and other benchmark schemes in terms of the weighted sum harvested power, validating the superiority of MAs in proactively reconfiguring channel conditions to boost energy transfer efficiency.