Modelling radio wave propagation in tunnels with ray-tracing method

The understanding of propagation characteristics in tunnels is important for communication systems deployed in tunnel environments. In this paper, formulas for path loss calculation based on ray-tracing techniques are presented. Two numerical criteria for terminating simulation processes are investigated together with their verifications. Among them, one criterion is the ending number of reflected rays; the other is the threshold for the last reflected ray. Simulation investigations carried out show that these two criteria are 50 and 0.1% respectively with accuracy in agreement with each other and with the measured results. The simulation results for propagation characteristics are illustrated for some applications with the developed programs.