Complete Propagation Model Structure Inside Tunnels

In this paper, a complete model structure for propagation inside tunnels is presented by following the segmentation-based modeling thought.According to the concrete propagation mechanism, totally five zones and four dividing points are modeled to constitute three channel structures corresponding to large-size users and smallsize users.Firstly, the propagation characteristics and mechanisms in all the zones are modeled.Then, from the view point of the propagation mechanism, the criterion of judging the type of a user is analytically derived.Afterwards, all the dividing points are analytically localized as well.Finally, a panorama covering all the propagation mechanisms, characteristics, models, and dividing pints for all types of users is presented for the first time.This panorama is very useful to gain a comprehensive understanding of the propagation inside tunnels.Validations show that by using the analytical equations in this paper, designers can easily realize a fast network planning for all types of users in various tunnels at different frequencies. INTRODUCTIONTo give the answer to the developing demand for high-performance wireless communication systems inside tunnels, many investigators have performed simulations and measurements of wave propagation in the last four decades.Based on different methods, such as vector parabolic equation (VPE) [1], geometrical optics (GO) [2, 3], modal analysis [4-6], finite-difference time-domain (FDTD) [7-9], etc.,