Measurement-Based Small-Scale Channel Model for Sub-6 GHz RIS-Assisted Communications

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.