n as the origin O of a cylindrical reference system and pate in the propagation process. As far as field strength the map is divided into angular sectors of given amplitude CHAPTER 4.7 Propagation modelling and channel characterisation . For each sector the average building height Ha is environment. Real (as opposed to effective) electromag- computed and a height tolerance Ah is set. Then, all netic parameters must be used for each single structure buildings well above average height (with H > Ha + Ah) composing the environment. are selected. Buildings of average height (i.e. with Ha - Ah Only FDTD has been used for deterministic field < H < Ha + Ah) are selected only if they have at least one prediction within COST 273. In [Schä03], an FDTD wall almost perpendicular (within a given angular tolerance method is used to investigate wave propagation between to the radial coordinate). This means that they are selected adjacent rooms in Hospitals in the frequency range from if they ideally could back-scatter energy toward the ellipse 42.6 MHz to 300 MHz. For an accurate simulation of (hence from the TX to the RX). Once classes A to C are propagation in such complex environments as hospital identified, the corresponding buildings are collected into rooms, with metallic layers in walls and with structures the simplified map and duplicates discarded. If more than that are small compared to the wavelength such as slots in one RX (TX) is present (ex. receiver path) the whole metal layers, numerical tools based on the solution of algorithm is performed once for every RX (TX) and each Maxwell's equations and a detailed description of each time the new buildings are added into the simplified map. layer composing each room wall are necessary. Wave In Figure 4.7-8 a simple case in the city of Helsinki is propagation between two adjacent rooms is investigated shown. It is shown in [DeFA04] that in this case the CPU for different frequencies and polarisations and results are time of an RT prediction can be reduced from 2131 compa