Reconfigurable intelligent surface (RIS)-empowered communication, has been considered widely as one of the revolutionary technologies for next generation networks. However, due to the novel propagation characteristics of RISs, underlying RIS channel modeling and measurement research is still in its infancy and not fully investigated. In this paper, we conduct multi-scenario broadband channel measurements and modeling for RIS-assisted communications at the sub-6 GHz band. The measurements are carried out in three scenarios covering outdoor, indoor, and outdoor-to-indoor (O2I) environments, which suffer from non-line-of-sight (NLOS) propagation inherently. Three propagation modes including intelligent reflection with RIS, specular reflection with RIS and the mode without RIS, are taken into account in each scenario. In addition, considering the cascaded characteristics of RIS-assisted channel by nature, two modified empirical models including floating-intercept (FI) and close-in (CI) are proposed, which cover distance and angle domains. The measurement results rooted in 2096 channel acquisitions verify the prediction accuracy of these proposed models. Moreover, the propagation characteristics for RIS-assisted channels, including path loss (PL) gain, PL exponent, spatial consistency, time dispersion, frequency stationarity, etc., are compared and analyzed comprehensively. These channel measurement and modeling results may lay the groundwork for future applications of RIS-assisted communication systems in practice.

翻译：可重构智能表面（RIS）赋能的通信被广泛视为下一代网络的革命性技术之一。然而，由于RIS新型传播特性的影响，底层RIS信道建模与测量研究仍处于起步阶段且尚未充分探索。本文针对子6GHz频段RIS辅助通信系统开展了多场景宽带信道测量与建模研究。测量涵盖室外、室内及室外到室内（O2I）三类固有非视距（NLOS）传播场景，并在每个场景中考虑了三种传播模式：RIS智能反射模式、RIS镜面反射模式及无RIS模式。此外，针对RIS辅助信道固有的级联特性，提出了两种改进的经验模型——浮动截距（FI）模型和近距离（CI）模型，这些模型同时覆盖距离域和角度域。基于2096次信道采集的测量结果验证了所提模型的预测精度。同时，对RIS辅助信道的传播特性进行了全面对比分析，包括路径损耗（PL）增益、PL指数、空间一致性、时间色散和频率平稳性等。这些信道测量与建模结果可为RIS辅助通信系统在实际中的应用奠定基础。