On the Prediction of Joint Rain Attenuation Statistics in Earth-Space Diversity Systems Using Copulas

The present paper proposes a novel model based on Copulas for predicting the outage probability experienced in Earth-space site diversity systems. In satellite communication networks, the increase of the operating frequencies above 10 GHz, which is mainly driven by the need of higher bandwidth, results in heavier signal attenuation due to various atmospheric effects. Precipitation and mainly rain induce high attenuation over earth-space links and is the most important factor limiting both links´ availability and reliability. In order to mitigate the rain fade effects to the links performance the site diversity technique can be employed. In the present paper, a new method for predicting the joint complementary cumulative distribution function (CCDF) of the rain attenuation using the Copulas functions is presented. The advantages of using Copulas are: (i) the single site rain attenuation is not required to be statistically modeled and (ii) only one parameter is employed to couple the two random variables corresponding to the rain attenuation of each one of the two links. The proposed model is compared to the model recommended by the International Telecommunication Union (ITU) in ITU-R P. 618-10 and it is shown to perform much better. Finally, the model is evaluated for micro scale and large scale diversity scenarios with very encouraging results.