Statistical behavior of signals from the wideband signal

Optical and radio signals that have been scattered by random refractive-index structure must be described statistically in systems-oriented codes and other applications. The general nature of the statistics that would best describe such signals has been an open question for some time, with different models being used close to the medium (log-normal) and far from it (Rician). Signal behavior in the intermediate zone, which is the relevant distance regime for radiowave communication through the structured ionosphere and through striated, high-altitude nuclear plasmas, has been difficult to characterize in a general and systematic way. The Wideband satellite experiment, with its multiple, coherent frequencies and its variety of observing geometries, has provided a wealth of data upon which to base a general model. In this work, careful and detailed analysis has been performed of VHF, UHF, and L-band data from the Wideband receiving stations at Ancon, Kwajalein, Stanford, and Poker Flat to establish the statistical behavior of scattered signals over a wide range of scattering strength, Fresnel-zone size (which sets the effective distance), and scattering geometry. Histograms of intensity and phase were compared, by means of chi-square testing, with probability density functions derived from four leading signal-statistical hypotheses: log-normal; generalized Gaussian, of which Rice statistics are a special case; two-component, which invokes the log-normal and generalized Gaussian hypotheses in different regimes of the signal fluctuation spectrum; and Nakagami-m, which is an approximation to generalized Gaussian statistics addressing only the behavior of signal intensity.