 to both a higher number of tion are presented and validated with measurements. Of concentrated losses and a higher distributed path loss. course, since the two different environments must be Thus, the simplification method is based on the selection handled in a uniform way, proper conversion procedures of the buildings belonging to three categories (A, B, C) as must be adopted. In the latter, an automatic propagation follows. model for the automatic planning of UMTS networks is (A) buildings located around and between the radio termi- presented which is one of the results of the European nals, buildings located within an ellipse of focuses TX Project Information Society Technologies (IST) Models and RX, and of given eccentricity are selected. and Simulations for Network Planning and Control - IST Usually the eccentricity value is chosen SO that the Project (MOMENTUM). Since the model must work in terminals are completely surrounded by buildings. different deployment scenarios (macro-, microcellular and indoor), algorithms to handle transition between (B) buildings which can be directly 'seen' from either the areas with digital terrain and urban databases of different TX, the RX or both terminals, therefore generating resolution have been developed. first- or second-order rays. This step is performed by running a simple geometric visibility tool de- Geometric database simplification embedded from a RT tool. Urban field prediction tools are always run over a discrete (C) buildings not belonging to category A and B but set of test spots, a route or a limited area such as a cell or which are likely to have an impact on propagation a portion of a city. Since computation time strongly because of their height (greater than average) or depends on the size of the input database, it is necessary orientation, i.e. generating low-order rays. to minimise its size by selecting only the active area of the Referring to the ellipse mentioned in (A), its centre is topology, i.e. only the buildings or obstacles that partici- chose