ol for simultaneous prediction of according to GO rules and up to a given maximum both outdoor and indoor radio coverage is presented by number of successive reflections/diffractions (often Lostanlen et al. in [LoCo02a], [CoLA03] and [LoCo05]. called prediction order) are found. In BL algorithms the The model is based on 2D BL in the horizontal plane position of only one terminal (the TX) is usually specified combined with a multiple knife edge diffraction Deygout at the beginning. Then the space is discretised into angular method to include the radial ORT path in the vertical sectors, each one corresponding to a beam which is plane [Deyg66]. The method is therefore of the 2.5D launched forward in the space. Each time a beam en- kind. The adoption of ray launching in the horizontal counters an obstacle it is reflected/diffracted according to plane saves CPU time w.r.t. RT for predictions over GO rules. In BL models unfortunately, space resolution areas. Moreover, the model can treat outdoor to outdoor generally decreases with distance from the TX. For what penetration and predict indoor coverage for outdoor BSs was previously described, RT is suitable for accurate, as well. Building penetration and path loss inside build- point-to-point prediction while BL is more suitable for ings can be computed in two different ways. If no accu- coverage prediction over large areas. Both RT and BL re- rate indoor database is available, each dominant ray produce to a certain extent the multipath propagation impinging on an outer wall of the building is then process. Multidimensional phenomena related to multi- prolonged inside the building according to the following path propagation (time and angle dispersion, space empirical-statistical formula: CHAPTER 4.7 Propagation modelling and channel characterisation Plane 3 Plabe 2 Figure 4.7-10 Example of VPL RT. Lin-building [dB] = the fifth floor is better than in the ground floor, as can be easily experimented in the real world. Outdoor-to-indoor propagation is especially impor- (4