Subway tunnel guided electromagnetic wave propagation at mobile communications frequencies

A measurement campaign has been carried out in the Berlin subway to charact erize electromagnetic wave propagation in underground railroad tunnels. The received power levels at 945 and 1853.4 MHz are used to evaluate the atten uation and the fading characteristics in a curved arched-shaped tunnel. The measurements are compared to ray-optical modeling results, which are based on ray density normalization. It is shown that the geometry of a tunnel, e specially the cross-sectional shape and the course, is of major impact on t he propagation behavior and thus on the accuracy of the modeling, while the material parameters of the building materials have less impact.