This study focuses on the optimization of a single-cell multi-user multiple-input multiple-output (MIMO) system with multiple large-size reconfigurable intelligent surfaces (RISs). The overall transmit power is minimized by optimizing the precoding coefficients and the RIS configuration, with constraints on users' signal-to-interference-plus-noise ratios (SINRs). The minimization problem is divided into two sub-problems and solved by means of an iterative alternating optimization (AO) approach. The first sub-problem focuses on finding the best precoder design. The second sub-problem optimizes the configuration of the RISs by partitioning them into smaller tiles. Each tile is then configured as a combination of pre-defined configurations. This allows the efficient optimization of RISs, especially in scenarios where the computational complexity would be prohibitive using traditional approaches. Simulation results show the good performance and limited complexity of the proposed method in comparison to benchmark schemes.

翻译：本研究聚焦于优化配备多个大规模可重构智能表面（RIS）的单小区多用户多输入多输出（MIMO）系统。通过联合优化预编码系数与RIS配置，在满足用户信干噪比（SINR）约束的条件下，实现总发射功率的最小化。该最小化问题被分解为两个子问题，并采用迭代交替优化（AO）方法求解。第一个子问题致力于寻找最优预编码器设计。第二个子问题通过将RIS划分为较小单元来优化其配置，每个单元被设置为若干预定义配置的组合。这种方法能够高效优化RIS，尤其适用于传统方法因计算复杂度过高而难以实施的场景。仿真结果表明，与基准方案相比，所提方法在保证良好性能的同时具有有限的计算复杂度。