Ray-optical prediction of radio-wave propagation characteristics in tunnel environments. 2. Analysis and measurements

For pt.I seeibid. vol.46, no.9, p.1328, (1998).The uniform theory of diffraction (UTD) developed in part 1 is used to predict narrow- and wide-band propagation characteristics in tunnels at 900- and 1800-MHz. Narrow-band propagation characteristics is shown in the spatial domain and wide-band propagation in the time domain. In empty straight-tunnel environments, propagation exhibits a break-point phenomenon and has very short time delay spread. In empty curved or branched tunnel environments, propagation suffers higher loss. Vehicles cause additional propagation loss and larger varying time delay spread in tunnels. The measured results have validated the accuracy of the theoretical model and provided important information on narrow-band and wide-band propagation characteristics in empty, branched and obstructed tunnels