Micro scale site diversity in satellite and tropospheric communication systems affected by rain attenuation

This paper reports experimental results of the performance of site diversity (SD) systems for sites distance, D, ranging from 500 m (micro scale SD) to 4500 m (small scale SD), at 19.77 GHz, in 31.6° and 30.6° slant paths in Central (Fucino) and Northern Italy (Gera Lario), respectively. The results have been derived by using the synthetic storm technique applied to a large set of rain rate data collected along two linear arrays of 7 rain gauges. Tested against the values of the SD gain predicted by Hodge's empirical formula, our results agree with these predictions down to D~1.7 km, i.e., in the range of validity of Hodge's formula. For D<1.7 km, our results are still likely to be sound and SD gain for D=500<750 m is about the same as that found for D~2 km, namely 15-30% of the single link rain attenuation, the latter expressed in decibels. Micro scale SD can be useful in small cells, or even in large user premises, at carrier frequencies above 10 GHz, in communications systems based on the "sky station" or "sky tower" concept (tropospheric communication systems), or in conventional geostationary satellite systems. The main findings are independent of frequency and elevation angle.