an improved model based on utd for multiple diffractions by buildings

in this paper, a new propagation model based on utd for multiple diffraction paths in cellular mobile radio communications in urban environments is proposed. moreover, the most rigorous novel utd-based expressions for multiple diffractions by buildings and excess path losses are d - rived and analyzed. for this purpose, building rows are supposed to have rectangular cross-sections with the same heights and spacings. in addition, in this analysis actual electrical roperties of buildings are regarded. previous studies have been concentrated on the simplified models that approximated building rows as absorbing half-screens or perfectly conducting half screens (knife-edges) or 90 degrees wedges. in this work, buildings are assumed flat-roofed parallel rows of dielectric blocks and their actual relative permittivity and conductivity are applied.