Ray-Tracing With Geometric Optics And UTD

Source: Remcom, Inc.

Geometric optics and the uniform theory of diffraction (GO/UTD) provide one of the dominant combined sets of methods used for calculating electromagnetic fields using ray-tracing. This method is very effective for calculating fields from waves propagating through a complex environment, such as an indoor office environment, or a dense urban scene. It is the dominant set of techniques used in Remcom’s Wireless InSite® 3D wireless prediction software.

Why Geometric Optics and UTD? 
Figure 1: Dominant propagation paths from a base station to a point within an urban setting

Wireless InSite’s ray-based solvers use the GO/UTD method to evaluate a ray path’s electric field. With GO/UTD, as rays propagate, they interact with geometric structures in the environment, reflecting from surfaces, diffracting from edges, and transmitting through obstructions.  Effects from these interactions are calculated using reflection, diffraction, and transmission coefficients calculated based on the material properties of each object, usually specified in terms of the dielectric properties (relative permittivity and conductivity) of one or more material layers.  Scattering effects can also be accounted for in terms of additional paths that scatter from surfaces that are rough compared to a wavelength.

A base assumption is that object surfaces are multiple wavelengths in size, though the edge corrections in the UTD method allow for one dimension to be fairly narrow relative to a wavelength. These basic size assumptions allow calculations to be performed based on interaction points rather than surface integrations, required for techniques such as Physical Optics (PO). This allows the methods to efficiently calculate propagation through large-scale indoor and outdoor scenarios, where interactions with many structures and walls can lead to dense multipath.