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 for RIS-empowered communications have covered a variety of applications, yet, very few papers have investigated the modeling of 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 an 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 deployment of an RIS with proper phase configurations 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 for 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广泛关注。尽管面向RIS赋能通信的理论模型已涵盖众多应用场景，但针对实际传播特性建模的研究仍鲜有涉及。本文通过建立经验统计信道模型，填补了RIS辅助宽带系统在2.6 GHz频段微小区信道变化特性研究的空白。基于室外、室内及室外到室内（O2I）环境的真实信道测量，我们对比并分析了全局、簇间及簇内参数。测量结果表明，采用适当相位配置的RIS部署可通过提升$K$因子、降低时间色散显著改善信道质量。所提出的统计模型与经验信道参数能有效刻画微小区衰落特性。这些研究成果对于未来面向RIS辅助无线通信系统的设计具有重要指导意义。