On the Diffusion Function of a Stochastic Transmission System

A brief review is given of the methods of characterisation of linear transmission systems randomly variant in time, with particular emphasis on the statistical hypothesis which leads to the introduction of the scattering function of the channel. In continuation the implications of such a hypothesis are outlined and the different types of tests which may be used are given; the tests are carried out either by means of a double monochromatic excitation of a channel or by a double impulse excitation. The excitation of the channel by white noise could equally lead to the same significant results.