This letter focuses on a transmitter or base station (BS) side beyond-diagonal reflecting intelligent surface (BD-RIS) deployment strategy to enhance the spectral efficiency (SE) of a time-division-duplex massive multiple-input multiple-output (MaMIMO) network. In this strategy, the active antenna array utilizes a BD-RIS at the BS to serve multiple users in the downlink. Based on the knowledge of statistical channel state information (CSI), the BD-RIS coefficients matrix is optimized by employing a novel manifold algorithm, and the power control coefficients are then optimized with the objective of maximizing the minimum SE. Through numerical results we illustrate the SE performance of the proposed transmission framework and compare it with that of a conventional MaMIMO transmission for different network settings.

翻译：本文聚焦于一种发射端或基站侧超对角反射智能表面（BD-RIS）部署策略，以提升时分双工大规模多输入多输出（MaMIMO）网络的频谱效率（SE）。在该策略中，有源天线阵列在基站处利用BD-RIS为下行链路中的多个用户提供服务。基于统计信道状态信息（CSI）的知识，采用一种新颖的流形算法优化BD-RIS系数矩阵，随后以最大化最小SE为目标优化功率控制系数。通过数值结果，我们展示了所提传输框架的SE性能，并在不同网络设置下将其与传统MaMIMO传输进行了比较。