- evaluating the fading depth in different environments terest SO far, like mobile cellular phones, this was obvi- and for different system bandwidths, while allowing to ously realistic. Although moving scatterers are certainly use any of the described approaches, starting either from always present, their influence is negligible, at least in the environment characteristics or from the PDP of the outdoor environments, due to their scattering cross- propagation channel. section being small compared with fixed scatterers With the emergence of third generation systems, [Cox73]. improvements in digital signal processing hardware, and For indoor environments, the scattering cross-section the increasing demand for a larger capacity, the spatial of moving objects (persons, doors, windows, etc.) still domain appears to be one of the last frontiers for cannot be neglected compared with fixed scattering exploiting the possibility of increasing systems capacity. objects (e.g. walls and furniture). Furthermore, for some This can be achieved by using different types of antenna, applications, e.g. wireless LANs, MTs are usually fixed at either the BS, or the MT, or both; therefore, new during operation, whereas quite often some scatterers are antenna and signal processing techniques are emerging, moving in the environment [KaFr01]. including smart antennas, either adaptive or switched Some of the few investigations of the influence of beam, spatial diversity combining, and MIMO. moving scatterers that can be found in the literature are A lot of work has been done concerning the imple- related to the temporal power fluctuations of a narrow- mentation of algorithms for achieving the desired link band channel, e.g. [HMVT94]. For a more comprehen- quality and system capacity using these techniques; sive and more universal treatment, however, wideband however, it is not clear how the values of short-term measurements are necessary. For this purpose, wideband fading depth observed by the different systems, working measurements were 