Reconfigurable intelligent surfaces (RISs) have attracted increasing interest from both academia and industry, thanks to their unique features on controlling electromagnetic (EM) waves. Although theoretical models of RIS-empowered communications have covered a variety of applications, yet, very few papers have investigated the modeling of the real propagation characteristics. In this paper, we fill this gap by providing an empirical statistical channel model to describe the small-scale channel variations for RIS-assisted broadband system at 2.6 GHz. Based on real channel measurements in outdoor, indoor and outdoor-to-indoor (O2I) environments, we compare and analyze the global, inter-cluster and intra-cluster parameters. Measurement results indicate that the intelligent reflection through an RIS can significantly improve the channel quality by enhancing the $K$-factor and reducing the time dispersion. The small-scale fading is well characterized by the proposed statistical model and the empirical channel parameters. These results are essential for the design of emerging RIS-assisted wireless systems and communication specifications in future applications.

翻译：可重构智能表面（RIS）因其在控制电磁波方面的独特特性，已引起学术界和工业界的日益关注。尽管RIS赋能通信的理论模型已涵盖多种应用场景，但关于实际传播特性建模的研究仍然很少。本文通过在2.6 GHz频段对RIS辅助宽带系统进行实际信道测量，提出了一种经验统计信道模型来描述小尺度信道变化，从而填补了这一空白。基于室外、室内及室外到室内（O2I）环境下的实测数据，我们比较并分析了全局、簇间及簇内参数。测量结果表明，RIS的智能反射可通过提高K因子和减少时延扩展显著提升信道质量。所提出的统计模型和经验信道参数能够很好地表征小尺度衰落特性。这些结果对于未来应用中新兴RIS辅助无线系统及通信规范的设计至关重要。