Modeling Ka-band scintillation as a fractal process

Abstract

We propose a model that describes the signal fading process due to scintillation in the presence of rain. We analyzed a data set of up-link (30 GHz) and down-link (20 GHz) attenuation values averaged over 1 second intervals. The data are samples relative to 10 significant events, for a total of 180,000 s, recorded at the Spino d'Adda (North of Italy) station using the Olympus satellite.Our analysis is based on the fact that the plot of attenuation versus time recalls the behaviour of a self-similar process. We then make various considerations and propose a fractional Brownian motion model for the scintillation process. We describe the model in detail, with pictures showing the apparent self-similarity of the measured data. We then show that the Hurst parameter of the process is a simple function of the rain fade. We describe a method for producing random data that interpolate the measured samples, while preserving some of their interesting statistical properties. This method can be used for simulating fade countermeasure systems.As a possible application of the model, we show how to optimise fade measurement times for fade countermeasure systems.Nedo Celandroni, Francesco Potortì: Modeling Ka band scintillation as a fractal process

DRS compression applied to MPEG-2 video data transmitted over a satellite channel

“…When considering this type of dynamic adaptive techniques, one should consider that the problem is complicated by a non-negligible delay in the control loop, and by the fact that the attenuation varies with time in a complex way [11]. Consequently, it is necessary to devise a way of using knowledge of the instantaneous attenuation for choosing the coding and DSR compression which are necessary to obtain a given QF.…”

Μοντελοποίηση Καναλιού Και Αξιολόγηση Επίδοσης Ασύρματων Επίγειων Και Δορυφορικών Συστημάτων Επικοινωνιών Νέας Γενιάς Υψηλών Ταχυτήτων

“…low pass with a -80/3 roll-off factor and the non-linear device the appropriate shape at the pdf of the generated time series. The low-pass filter has a characteristic function given in In [Celadroni99], the fractional Brownian motion is proposed for the modeling of scintillation time series. According to the analysis on the physical characterization of scintillation, a difference process is defined W(t 1 , t 2 )=A(t 2 )-A(t 1 ), with A the attenuation values and for sufficient small t=t 2 -t 1 , is the difference process of scintillation.…”

“…This difference process is assumed to be a function of rain attenuation, since scintillation variance depends on scintillation. It is stated in [Celadroni99] that the process W(t,A) is assumed to be normal with zero mean and variance of 2 W σ which is also validated through chi-square tests. Therefore, scintillation is modeled as a fBm process with variance:…”