Cell-Free Massive MIMO SWIPT with Beyond Diagonal Reconfigurable Intelligent Surfaces

TL;DR

This paper explores the use of beyond-diagonal reconfigurable intelligent surfaces in cell-free massive MIMO systems to enhance simultaneous wireless information and power transfer, providing analytical insights and improved design strategies.

Contribution

It introduces an analytical framework for evaluating spectral efficiency and energy harvesting in BD-RIS aided CF-mMIMO systems with SWIPT, including a heuristic scattering matrix design.

Findings

BD-RIS significantly improves wireless power transfer to energy users.

Analytical models accurately predict spectral efficiency and harvested energy.

Heuristic scattering matrix design outperforms random configurations.

Abstract

This paper investigates the integration of beyond-diagonal reconfigurable intelligent surfaces (BD-RISs) into cell-free massive multiple-input multiple-output (CF-mMIMO) systems, focusing on applications involving simultaneous wireless information and power transfer (SWIPT). The system supports concurrently two user groups: information users (IUs) and energy users (EUs). A BD-RIS is employed to enhance the wireless power transfer (WPT) directed towards the EUs. To comprehensively evaluate the system's performance, we present an analytical framework for the spectral efficiency (SE) of IUs and the average harvested energy (HE) of EUs in the presence of spatial correlation among the BD-RIS elements and for a non-linear energy harvesting circuit. Our findings offer important insights into the transformative potential of BD-RIS, setting the stage for the development of more efficient and effective SWIPT networks. Finally, incorporating a heuristic scattering matrix design at the BD-RIS results in a substantial improvement compared to the scenario with random scattering matrix