Numerical estimations of the propagation characteristics of wireless links in high-speed train cars

Demand for wireless broadband access services in long-distance transportations continues to grow. Several railway companies have recently begun in-car wireless LAN services [1]. In order to advance the radio link design in support of such services, an accurate and reliable method for estimating the electromagnetic environment in actual situations is required. However, comprehensive on-site field measurements cost too much, and it is difficult to carry them out precisely. In addition, measurements must take account of the absorbing effects due to many passengers triggering the drawbacks of poor feasibility and repeatability. This study introduces an accurate and reliable method of estimating electromagnetic field (EMF) distributions in train cars so as to advance the radio link design of wireless LANs operated inside train cars. The authors previously proposed an EMF estimation method for a typical commuter train based on FDTD analysis and parallel computing [2]. This paper evaluates the propagation characteristics in a High-Speed Train Car (HSTC). Using newly developed numerical models of HSTC, which include many passengers, EMF distributions created by a 5.2 GHz wireless transmitter inside the HSTC are analyzed and propagation characteristics are evaluated. In order to estimate the effect of the absorption by the passengers' bodies, simplified histograms of the electric field distributions throughout the whole interior of the car are derived.