A tree-scattering model for improved propagation prediction in urban microcells

This paper presents a model for the scattering of radiowaves from the canopy of a single tree. The canopy is modeled as a cylindrical volume containing randomly distributed and oriented cylinders, representing the branches, and thin disks, representing the leaves. A simple expression for the incoherent scattered field outside the canopy is obtained using Twersky´s multiple scattering theory. This expression is shown to agree well with results of scattering measurements on a live tree typical of those found in urban environments. The scattering model can be readily incorporated in ray-based propagation prediction tools that assist the planning of microcellular radio networks. This involves the use of so-called tree-scattered rays, which interact at the tree centers. Path loss predictions generated with the aid of the new model are shown and compared with measured data to illustrate the considerable improvement in prediction accuracy that can be achieved in realistic urban microcellular scenarios by taking into account the scatter from trees.