Profile Measurement and Distribution Statistics of Amplitude Scintillation Within the Lowest Tropospheric Layers Using Karasawa Model

Abstract

Characterizing the variation dynamics of amplitude scintillation within the lowest layers of the troposphere is important for many communication system applications. It provides fast fade statistics used to determine the non-rain-induced fade margin needed for implementing effective fade mitigation techniques on both terrestrial and satellite radio channels. This study employed three-year in-situ data of primary radio-climatic factors (temperature and relative humidity) and radio channel parameters (frequency, elevation angle, and antenna diameter) for estimating tropospheric amplitude scintillation and evaluating its vertical profile over Akure, Nigeria, using the Karasawa scintillation model. The radio-climatic parameters were measured at five altitudinal layers from the surface to a height of 200 m at 50 m interval on a 220 m-tall mast using a Davis Vantage Pro2 automatic weather station at 30 min interval. The extracted data spanned January 2008 to December 2010 (3 years). Radio link parameters frequency, elevation angle, and antenna diameter, with values of 12.5 GHz, 53°, and 0.9 m, respectively, were employed for the computation of scintillation amplitude (χ) and intensity (σ) along with the weather variables. From the results, the histogram of annual scintillation intensity at all levels was well approximated by the stable probability density function (pdf) distribution model. The magnitude of scintillation intensity was found to be much higher during the rainy season than during the dry season. Minimal differences, between 2 and 8% in magnitude, were observed in the annual averaged amplitude across the levels, but the rainy-dry season dichotomy was conspicuous following monthly analysis. An allowance of 0.5 dB and 0.38 dB is required to counteract the effects of scintillation amplitude fade and enhancement, respectively, at this location.