sk Reference; ISBN: 9780123746481 Copyright © 2006, Luis M. Correia. Published by Elsevier Ltd 2001. All rights reserved CHAPTER 4.7 Propagation modelling and channel characterisation parameter estimation techniques must be used. Im- Unfortunately, some of those methods require very large provements in the dedicated algorithms (Multiple Signal amounts of computer resources (both memory and Classification (MUSIC), ESPRIT and Space-Alternating processing time), when applied to scenarios that are large Generalised Expectation (SAGE)) are discussed in Sec- compared to the wavelength, so that they are not yet tion 4.7.4 and examples of applications are presented. within the reach of the telecommunication engineer. The Measurements are then processed to extract the chan- work within this COST Action has tried to reduce this nel's statistical properties. Section 4.7.5 introduces improved empirical path-loss models that are valid for rural and suburban environ- Full moment methods ments as well as office buildings. It is usually assumed Of course those methods have been applied to the that long-term fading is due to a shadowing process and computation of structures, which are limited in size, such different approaches have been studied in an attempt to as (elements of smart) antennas [VeLC02b], [TrSi02], improve the well-known model based on randomly dis- [TrSi03] and [NdHH04]. Here the emphasis was placed tributed Gaussian variables. The rationale behind more on the optimal design of specific antennas, with as another well-established assumption - that long- and the main goal the optimisation of the discrimination of short-term fading should be modelled separately - is the waves impinging on those antennas by numerical called into question, and a new model based on multiple methods described mostly in Section 4.7.4. Paper scattering is described. Lastly, extending the models to [VeLC02b] describes in detail the design of 3D array the wideband case, which is necessary when the relative antennas, which allow signal pick-u