Ray-density normalization for ray-optical wave propagation modelingin arbitrarily shaped tunnels

This work is concerned with the calculation of natural electromagnetic (EM) wave propagation and the determination of the propagation channel characteristics in highway or railway tunnels in the ultrahigh-frequency (UHF) range and above (>300 MHz). A novel ray-tracing technique based on geometrical optics (GO) is presented. Contrary to classical ray tracing, where the one ray representing a locally plane wave front is searched, the new method requires multiple representatives of each physical EM wave at a time. The contribution of each ray to the total field at the receiver is determined by the proposed ray-density normalization (RBN). This technique has the further advantage of overcoming one of the major disadvantages of GO, the failure at caustics. In contrast to existing techniques, the new approach does not use ray tubes or adaptive reception spheres. Consequently, it does not suffer their restrictions to planar geometries. Therefore, it allows one to predict the propagation of high-frequency EM waves in confined spaces with curved boundaries, like tunnels, with an adequate precision. The approach is verified theoretically with canonical examples and by various measurements at 120 GHz in scaled tunnel models     

An approach to include stochastic rough surface scattering into deterministic ray-optical wave propagation modeling

A new method to include stochastic rough surface scattering into deterministic ray-optical wave propagation modeling is derived. It can be utilized in conjunction with the concept of ray launching. Similar to the Kirchoff formulations, the approach is based on a tangential plane approximation, i.e., it is applicable to surfaces with gentle undulations, whose horizontal dimensions are large compared to the incident wavelength. However, in contrast to the Kirchoff models, which are only valid for either slightly rough or very rough surfaces, the proposed stochastic scattering approach includes both the coherent and incoherent components at the same time. The purely deterministic ray-based modeling is expanded by a "stochastic" component, allowing, for the first time, to account for nondeterministic scattering in ray-optical wave propagation modeling.     

Subway tunnel guided electromagnetic wave propagation at mobilecommunications frequencies

A measurement campaign has been carried out in the Berlin subway to characterize electromagnetic wave propagation in underground railroad tunnels. The received power levels at 945 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 modeling results, which are based on ray density normalization. It is shown that the geometry of a tunnel, especially the cross-sectional shape and the course, is of major impact on the propagation behavior and thus on the accuracy of the modeling, while the material parameters of the building materials have less impact     

Two- and three-dimensional ray tracing applied to the land mobilesatellite (LMS) propagation channel

This work examines the application of ray-tracing propagation models to system simulations for satellite mobile communications. A two-dimensional (2D) and a three-dimensional (3D) algorithm are outlined and compared using canonical propagation problems. Additional comparisons of both models with measurement campaigns are performed. The results show that two-dimensional models are suited for coverage and network planning. For system-design studies, however, three-dimensional ray tracing is mandatory. The novel three-dimensional ray-tracing model is able to predict time series of power delay profiles, Doppler and polarimetric information with high precision. It includes the time-variant correlation between the propagation channels of all visible satellites of an arbitrary satellite constellation. It therefore proves to be especially suited for system investigation of future LMS communication and navigation systems