Natural wave propagation in subway tunnels at mobile communications frequencies

A measurement campaign has been carried out in the Berlin subway to characterize EM-wave propagation in underground railroad tunnels. The received power levels at 945 MHz, and 1853.4 MHz are used to evaluate the attenuation and the fading characteristics in a curved, arched-shaped tunnel. The measurements are compared to ray-optical modelling results. It is shown that the geometry of a tunnel, especially the cross-sectional shape and the course, is of major impact on the propagation behaviour and thus on the accuracy of the modelling.