Analysis and Modeling of Near-Ground Wave Propagation in the Presence of Building Walls

An efficient semi-analytic model for near-ground wave propagation in indoor scenarios is presented. For transceivers deployed in indoor environments on or near the ground, since RF wave propagation is dominated by Norton surface waves, these higher order waves and their interactions with building walls and other indoor obstacles have to be captured for accurate field calculations. Existing ray tracing routines which are commonly used for indoor field prediction, are inadequate for evaluating signal coverage of transceiver nodes very close to the ground (less than a wavelength above ground) since such routines neglect higher order surface waves. In addition, geometrical optics alone is inadequate to treat finite-size and possible irregular-shaped obstacles at low radio frequencies (VHF and lower UHF). Our approach for calculation of near-ground wave propagation and scattering is based on a hybrid physical optics and asymptotic expansion of dyadic Green's function for a half-space dielectric medium. Equivalence principle in conjunction with physical optics approximation is utilized to handle scattered field from building walls which are the dominant scatterers in indoor settings. Simulation results for various indoor propagation scenarios based on the new approach is validated by using both measurement results and full-wave numerical solvers.