This works explores the correlation between channels in reconfigurable intelligent surface (RIS)-aided communication systems. In this type of system, an RIS made up of many passive elements with adjustable phases reflects the transmitter's signal to the receiver. Since the transmitter-RIS link may be shared by multiple receivers, the cascade channels of two receivers may experience correlated fading, which can negatively impact system performance. Using the mean correlation coefficient as a metric, we analyze the correlation between two cascade channels and derive an accurate approximation in closed form. We also consider the extreme case of an infinitely large number of RIS elements and obtain a convergence result. Our analysis accuracy is validated by simulation results, which offer insights into the correlation characteristics of RIS-aided fading channels.

翻译：本文探讨了可重构智能表面（RIS）辅助通信系统中信道之间的相关性。在此类系统中，由大量具有可调相位的无源元件构成的RIS将发射机信号反射至接收机。由于发射机-RIS链路可能被多个接收机共享，两个接收机的级联信道可能经历相关衰落，这会对系统性能产生负面影响。我们采用平均相关系数作为度量指标，分析了两条级联信道之间的相关性，并推导出闭合形式的精确近似表达式。同时，我们考虑了RIS元件数量趋于无穷的极限情况，并得到了收敛性结论。仿真结果验证了所提分析方法的准确性，并为RIS辅助衰落信道的相关特性提供了重要见解。