Improving the accuracy of ray-tracing techniques for indoor propagation modeling

Problems with the use of ray-tracing techniques in indoor propagation environments are identified, and a new set of widely applicable diffraction coefficients is developed. The limitations on the accuracy of the ray-tracing method in indoor propagation environments are first assessed. The effects of scatterers with dimensions approaching the wavelength of operation and of scatterers with finite conductivity are considered. The accuracy of ray tracing is quantified by comparison to a full-wave simulation technique, which combines the finite-difference time-domain method with a spatial transformation technique, the Kirchhoff surface integral formulation. Simulation results demonstrate that when the magnitude and phase of the received signal components are properly accounted for, the ray-tracing solution may be accurate down to a fraction of a wavelength. A new set of diffraction coefficients is presented for calculations involving obstacles with finite conductivity. The new coefficients eliminate an artificial dip in the diffracted field strength, which is often encountered when currently available techniques are used. Validation is provided by comparison with full-wave simulations and measurements. Improved accuracy in both the illuminated and shadowed regions is demonstrated.