High-Speed Train Channels with Reconfigurable Intelligent Surface: Modeling and Analysis

In this paper, a geometry-based millimeter-wave channel model is proposed for on-board reconfigurable intelligent surface (RIS)-assisted high-speed train communications, where three propagation cases are considered to describe real channels. In addition, RIS phase optimization method is presented to enhance received power and mitigate channel fading. Based on the proposed model, impacts of RIS phase optimization and channel parameters on channel impulse responses are analyzed. Numerical results indicate that received power at a specific area can be enhanced by adjusting the phase of RIS elements, and a larger number of RIS elements can effectively improve performance of high-speed train systems. These observations and conclusions are insightful for designing and realizing RIS-assisted high-speed train communications.