Characteristics of radio propagation channels in tunnel environments: a statistical analysis

The propagation characteristic in tunnel environments is very different from that in free space. Measurements for both strong and weak fading phenomena regions have been performed to characterize the channels in a tunnel. The direct and reflected waves of the received power have been separated, and the ratio of the reflected wave to the direct wave is used to estimate a parameter, K. The tunnel propagation channels have been analyzed for variation of the K parameter with distance. The signal was received in the form of a Rician channel with the reflected and the direct waves. With the channel characterized using the K parameter, in a short section, where the receive antenna is near the transmit antenna, the received signal distribution fitted a Gaussian channel, while it fitted the Rayleigh channel in long sections.