  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.
