Path-loss characteristics in subway tunnels at 2.65 GHz

This paper presents the measurement of electromagnetic wave propagation in subway tunnels at f = 2.6425 GHz. The main goal of this work is to obtain more accurate knowledge of the propagation characteristics in straight and curved tunnels. Measurements have been conducted in four different types of tunnel courses: a straight tunnel, two curved tunnels (with 245-m and 500-m radius of curvature, respectively), and a tunnel that has both straight and curved sections. From the measured results, we analyze and compare the differences between the straight and curved tunnels, particularly with regard to path loss and the effect of path loss arising from different curvatures, and the characteristics of the combined tunnel (the straight and curved tunnel). The findings presented here should prove helpful in the estimation of link budget for satellite DMB service in tunnels and the determination of accurate propagation characteristics in tunnels.