Simulation and Analysis of Propagation Characteristics for Tunnel Train-Ground Communications at 1.4 and 40 GHz

This paper focuses on the analysis of propagation characteristics for train-ground communication (TGC) systems in tunnel scenarios at both low frequency and millimeter-wave (mmWave) bands, based on ray-tracing (RT) simulation. The material parameters in the RT simulation are calibrated by measurement data collected in realistic tunnel environments. A practical three dimension (3D) tunnel TGC environment considering the existence of train cars is established, which is further divided into three kinds of scenarios, involving the direct coverage, relay coverage, and in-train coverage scenarios. Both large-scale and small-scale propagation characteristics, such as path loss and root mean square delay spread, are analyzed for the three tunnel TGC scenarios. The obtained results can provide useful information for the design of future fifth-generation (5G) tunnel TGC systems.