I. Introduction
In recent years wireless digital communications had an enormous impact in daily life which required and still requires the development of new devices. Therefore the need of effective and economical test facilities to evaluate the functionality of the devices, in various wireless channels, is a key issue. in particular it is important to evaluate the transmission quality and robustness of the digital signals, employed by these wireless devices, in non-line-of-sight (NLOS) channels, where only scattered waves arrive to the receiver, and in line-of-sight (LOS) channels, in which there is also a direct link between the transmitting and the receiving antenna. in the first case, the field structure is modelled by a Rayleigh field model; in the second one, the field structure is modelled by a Rice field model. from a physical point of view, the Rayleigh distribution is well justified, as the received signal is assumed to be a superposition of a large number of randomly phased waves. More important are the LOS channels where the received signal is the combination of a dominant component, due to the direct link between the transmitting and the receiving antenna, and multiple scattered waves. in this last case, i.e., in a LOS channel, the fading depth on the received signal can be measured by means of the Rice factor, , as explained in the following. Each LOS channel is characterized by its own value. A NLOS channel is a particular case of LOS channel obtained when .