A new uniform theory of diffraction based model for multiple building diffraction in the presence of trees

摘要

In this article, the uniform theory of diffraction is the base of multiple diffraction loss calculation by buildings. The path loss is derived and analyzed on the basis that buildings are parallel rows of dielectric blocks, having rectangular shapes and being flat roofed with the same heights and spacing. As far as the path loss calculation is concerned, the above assumption leads to more realistic results, since previous studies are limited to the simplified models in which buildings are approximated as absorbing half-screens, perfect conducting half-screens (knife-edges), or 90 wedges. In addition, this study endeavored to extend this model to include higher-order terms for reflection coefficients as well as considering tree effects. In this way, it was assumed that apart from the high-rise urban core, buildings have nearly the same height and spacing and are organized by street systems into rows; also, the trees are assumed to be situated next to the buildings. The canopies of trees are modeled as discrete ensembles of leaves and branches. The comparison between the model and measurement data shows that including tree effects provides reasonable and convincing predictions.