Effect of terrain on path loss in urban environments for wireless applications

Path loss prediction algorithms for advanced wireless communication system planning have long considered the effect of electromagnetic propagation over buildings between the base station and subscriber. This phenomena is particularly important in residential areas, where the houses are typically a few stories high. For the most part, the buildings were assumed to lie on level terrain, although shadowing effects by the terrain in the absence of buildings has been included. Previous works have offered a number of methods to quantitatively determine these effects from path profiles. This study examines propagation over buildings when the buildings are located on terrain features (hills). The buildings, which are represented by a series of absorbing half screens, are assumed to lie in rows that are equally spaced along parallel streets, with the streets running perpendicular to the terrain slope. Numerical results are obtained using successive repetition of the Kirchhoff-Huygens approximation. A phenomenological model based on ray optics for diffraction over a smooth surface is proposed as a way to interpret the numerical results. The dependence of the model coefficients on the terrain parameters are obtained from the numerical results.