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 design.

翻译：本文研究了超越对角可重构智能表面（BD-RIS）在无小区超大规模多输入多输出（CF-mMIMO）系统中的集成应用，重点聚焦于同时无线信息与能量传输（SWIPT）场景。该系统支持两类用户并发工作：信息用户（IUs）与能量用户（EUs）。采用BD-RIS技术增强面向EUs的无线能量传输（WPT）性能。为全面评估系统性能，我们构建了在BD-RIS单元间存在空间相关性及非线性能量采集电路条件下的分析框架，分别计算IUs的频谱效率（SE）与EUs的平均采集能量（HE）。研究结果揭示了BD-RIS的变革潜力，为开发更高效能的SWIPT网络奠定了基础。最后，与随机散射矩阵设计方案相比，在BD-RIS中采用启发式散射矩阵设计可实现显著的性能提升。