Influence of Typical Railway Objects in a mmWave Propagation Channel

In the future railway services, wireless communication is the fundamental part and millimeter wave (mmWave) is foreseen to be a key enabler toward the smart railway. An accurate understanding of the propagation environment can assist designing both systems and railway infrastructures for better communication services. In this paper, the influence of typical objects to the mmWave propagation channel is analyzed for “train-to-infrastructure” and “intrawagon” railway scenarios with various configurations. Propagation measurements are conducted in the mmWave band for the 12 most common railway materials. The corresponding electromagnetic parameters are obtained, and a 3-D ray tracing (RT) simulator is calibrated. The mean absolute error of the simulated $S_{21}$ parameter is $-$53.5 dB, indicating that the calibrated RT can be used to generate the close-to-real mmWave channel for railway scenarios. Statistically consistent scenarios and deployments are generated, which enables drawing unbiased numerical results based on intensive RT simulations. The influence of typical objects and corresponding material compositions is then compared, and significant objects are determined for each scenario. The results of this work not only imply how the propagation environment impacts on the propagation channel, but also make suggestions to efficiently reconstruct railway environment models for an accurate RT-based channel model. Moreover, the understanding of the influence of the environment at object and material levels will, in turn, guide the construction of railway infrastructure for better railway services.