Study on the propagation characteristics of radio wave in tunnels by the method of SBR/image

In this paper, the propagation characteristics of radio wave is studied in tunnel environments based on the method of SBR/Image (Shooting and bounding ray tracing/Image). An agreement is achieved by a comparison of simulated results and measured results. The formula of field strength considering polarization has been derived. Then the tunnel physical model has been set up. Some propagation parameters have been obtained in the simulations, such as the received power, delay spread, Doppler shift and so on. The simulated results indicate that the delay spread will become increasingly smaller and almost has no relationship with radio waves frequency in the long rectangular tunnel with the increase of propagation distance. Doppler shift changes between -10Hz~-110Hz when the radio frequency is 900MHz and receiver moving speed is 40m/s. Theoretical basis for wireless network communication planning and optimization in tunnels can be provided by above results.