A Hybrid Ray-Tracing/Vector Parabolic Equation Method for Propagation Modeling in Train Communication Channels

In recent years, various techniques have been applied to modeling radio-wave propagation in railway networks, each one presenting its own advantages and limitations. This paper presents a hybrid channel modeling technique, which combines two of these methods, the ray-tracing (RT) and vector parabolic equation (VPE) methods, to enable the modeling of realistic railway scenarios including stations and long guideways within a unified simulation framework. The general-purpose RT method is applied to analyze propagation in complex areas, whereas the VPE method is reserved for long and uniform tunnel as well as open-air sections. By using the advantages of VPE to compensate for the limitations of RT and vice versa, this hybrid model ensures improved accuracy and computational savings. Numerical results are validated with experimental measurements in various railway scenarios, including an actual deployment site of communication-based train control (CBTC) systems.