This paper considers Cell-Free Massive Multiple Input Multiple Output (MIMO) systems with the assistance of an RIS for enhancing the system performance. Distributed maximum-ratio combining (MRC) is considered at the access points (APs). We introduce an aggregated channel estimation method that provides sufficient information for data processing. The considered system is studied by using asymptotic analysis which lets the number of APs and/or the number of RIS elements grow large. A lower bound for the channel capacity is obtained for a finite number of APs and engineered scattering elements of the RIS, and closed-form expression for the uplink ergodic net throughput is formulated. In addition, a simple scheme for controlling the configuration of the RIS scattering elements is proposed. Numerical results verify the effectiveness of the proposed system design and the benefits of using RISs in Cell-Free Massive MIMO systems are quantified.

翻译：本文在RIS的协助下,审议了无细胞大量输入多重输出系统,以提高系统性能。在接入点考虑了分配的最大比例组合(MRC),我们采用了为数据处理提供充足的信息的综合频道估计方法。我们通过使用无症状分析对考虑的系统进行了研究,这种分析使APS和/或RIS元素的数量大增。对于有限数量的ARISAP和设计中的RIS散射元素来说,频道容量较低,并且为顶端链路网输送量制定了封闭式表达式。此外,还提出了控制RIS散射元素配置的简单办法。数字结果对拟议的系统设计的有效性和在无细胞的大型IMIMO系统中使用RIS的好处进行了量化。