An iterative detection and decoding (IDD) scheme is proposed for multiuser multiple-antenna systems assisted by an active or a passive Reconfigurable Intelligent Surface (RIS). The proposed approach features an IDD strategy that incorporates Low-Density Parity-Check (LDPC) codes, RIS processing with refinements of soft information in the form of log likelihood ratios (LLRs) and truncation. Specifically, a minimum mean square error (MMSE) receive filter is used for refinement of LLRs and truncation at the RIS, and for soft interference cancellation at the receiver. An analysis of the proposed MMSE refinement is also devised along with a study of the computational complexity of the proposed and existing schemes. Simulation results demonstrate significant improvements in system capacity and bit error rate in the presence of block-fading channels

翻译：本文提出了一种用于主动或被动可重构智能表面（RIS）辅助多用户多天线系统的迭代检测与解码（IDD）方案。该方案采用了一种结合低密度奇偶校验（LDPC）码、基于对数似然比（LLR）软信息优化与截断的RIS处理的IDD策略。具体而言，采用最小均方误差（MMSE）接收滤波器在RIS端进行LLR优化与截断，并在接收端执行软干扰消除。本文同时对所提出的MMSE优化方法进行了理论分析，并对所提方案与现有方案的计算复杂度进行了比较研究。仿真结果表明，在块衰落信道环境下，该系统在容量和误码率性能上均取得了显著提升。