Channel Characteristics Analysis of RIS-Assisted Wireless Communication in Mountainous City Scenarios

The space-time-frequency (STF) characteristics of Reconfigurable Intelligent Surface (RIS)-assisted communication channels significantly influence the performance of integrated sensing and communication systems. This paper classifies three distinct communication scenarios in the complex mountainous city environment of Chongqing: mountainous urban, mountainous tunnel/bridge, and mountainous riverside scenarios. Different channel models are developed by accounting for the variations in path propagation across the three scenarios. Theoretical analyses of fading characteristics are conducted for the different scenarios, with a focus on the path loss model incorporating the water surface effect in the riverside scenario and the dualslope path loss model refined for the tunnel scenario to account for the waveguide effect. Numerical simulations are employed to investigate the STF correlation characteristics of the channels in these three scenarios. The results indicate slightly higher temporal autocorrelation in the urban and tunnel scenarios compared to the riverside scenario, due to the line-of-sight path and RIS assistance. Additionally, the double RIS reconfiguration of the electromagnetic wave propagation path in the riverside scenario leads to smoother, reduced spatial correlation compared to the other scenarios, and causes the scatterers to be more dispersed, resulting in greater delay spread. It is shown that RIS-assisted communication channel models in complex mountainous environments exhibit distinct statistical characteristics across different communication scenarios.