On screen placement for building representation in urban environments considering 2D multiple diffraction problems

A numerical method to solve 2D diffraction problems is used in this work to understand the number and placement of screens needed to represent individual buildings in path loss prediction tools. The methodology used to determine the field strength is based upon the Kirchhoff-Huygens integral, where the incident field on the plane containing a screen is given in terms of the field in the aperture plane of the previous screen. A relatively simple analysis is performed, whereby two different screen representations for the buildings between the transmitter and receiver are used to obtain the excess path loss over free space. The results clearly indicate that screen placement variability does not effect the path loss range dependence. The importance of representing a building by one or two screens has considerable consequences, namely whether on average, the predicted results are 4-7 dB off actual path loss values