The effect of building height variation on the multiple diffraction loss component of the Walnsch-Bertoni model

The Walfisch model predicts the average path loss from a conceptualised model of the propagation environment in which propagation is assumed to take place over rows of buildings of equal height and spacing. The propagation loss is then separated into that resulting from free space wavefront spreading, multiple forward-diffraction past the rows of buildings and diffraction over the final rooftop down to the receiver. In this paper we use numerical simulations to examine the effect of random building height variations on the multiple diffraction loss component of the model. In particular, our results show that the average multiple diffraction loss component is increased by any building height variations. A simple equation, which agrees to within 1 dB of the simulation results, and that relates building height variations, wavelength and average building separation to the increase in average multiple diffraction loss, is presented.