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This paper describes an algorithm for the implementation of the slope diffraction method [Andersen97] for an arbitrary codiguration including edges or wedges. Validations against several published results are presented. The validations include examples of wedge Configurations for which no validation of the slope diffraction method is available in the literature. Furthermore, an estimation for an urban environment of the gain in accuracy due to the use of the slope diffraction method over the classical Uniform Theory of Diffraction (UTD) was performed. It was found that the gain in accuracy is directly related to a factor we called the Transition Region Width TRW. TRW depends on the three parameters (the frequency freq, the separation between two screens d, the difference in building heights Ah) to give a single parameter:Ah'/(h*d). It was shown that the classical UTD used with power summing of the rays can be accurate in configurations in which it was usually not considered to be valid. The results were obtained from 25 realizations of 10 equally spaced screens with heights distributed according to a uniform distribution U[18-Ah, 18+Ah] m.

Mobile cellular communication has already entered the mass market, and mobile Internet services will soon become a reality. The frequent use of mobile radio technologies wherever people are has a direct impact on the deployment of base stations or radio access points, including antennas. Put simply, to serve an increasing number of users requires an increasing number of base stations. Thus, operators must carefully plan the deployment and configurations of radio base stations in order to support voice and data traffic at a level of quality expected by customers. Planning tools are used to help radio engineers in their difficult tasks of balancing requirements or radio coverage and quality with economic and other practical aspects. These planning tools make extensive use of terrain databases and of visualisation tools that lead some tool vendors to offer functionalities very similar to a geographical information system (GIS) or even to base their product on a GIS. Futhermore, because radio communication between base stations and users is crucial, all computations in a planning tool are based on the use of radio-propagation predictions. Until recently, empirical propagation prediction seemed sufficient. However, more efficient planning and the planning of nonvoice services or of a mixture of voice and nonvoice services require more accurate propagation-prediction models. These propagation models are usually based on the computation of the physical interaction of ratio waves and the environment. Thus more detailed databases are required, especially in urban environments where most users are located. Although the authors are not GIS specialists, they aim to expose some of the relationship between radio-propagation models used for mobile radio network planning and databases for terrain and buildings. For example, an accuracy of about 1 m on the coordinates of building corners is found to be acceptable in terms of accuracy in radio coverage. As another example, simulation results show that the use of conventional propagation models and rough geographical databases for the planning of future cellular systems like UMTS might cause serious difficulties.