SUMMARYKnowledge about the dynamic characteristics of rain attenuation is of utmost importance for many applications in terrestrial and satellite communication systems operating at frequencies above 10 GHz: Long-term rain rate statistics and rain rate duration statistics are usually available from meteorological data. In this paper, a spatial-temporal analysis is employed in order to evaluate the rain attenuation power spectrum of a terrestrial/satellite path. The predicted power spectrum is compared with experimental data. Based on the spectral analysis of rainfall rate a method for converting rain rate duration statistics to link fade duration statistics is also proposed. Fade duration statistics are presented for terrestrial and satellite links and compared with available experimental data. The agreement between the predicted results and the experimental data has been found to be quite encouraging. Finally, numerical results are presented for various climatic zones, elevation angles and frequencies. Some very useful conclusions concerning the dynamic properties of rain attenuation for a microwave path are deduced.

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Route diversity systems as available means to improve the rain outage performance are examined by comparison to tandem systems. A general and somewhat rigorous analysis for the evaluation of the joint probability on a pair of opposite hops has been performed, which is valid for any frequency. The total rain outage performance has been shown explicitly to be given approximately by the summation of joint probabilities on pair hops of the diversity system. Finally, a general and compact algorithm for the evaluation of the path length enlargement effect has been constructed which is valid for any frequency, above 10 GHz and single hop‐length of the corresponding tandem system.

The main propagation effect on interference between adjacent Earth‐space paths is differential rain attenuation. In the present paper, a revised method to predict the rain differential attenuation statistics is proposed which is based on a model convective rain cell structure of the rainfall medium and the assumption that the point rainfall statistics follows a lognormal form. Moreover, the revised model analyzes the general problem of differential attenuation taking into account the difference of elevation angles of the slant paths under consideration. The numerical results are referred to the interference problem from an adjacent satellite located in symmetrical geostationary positions in relation to the intended satellite and examine the significance of the difference of elevation angles for various parameters of the problem.

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Abstract. For frequencies above 10 GHz, which are of high importance in current satellite systems, interference is mainly aggravated because of the following reasons: potentially existing differential rain attenuation along the wanted and interfering paths as well as depolarization induced by the rainfall medium. The latter source concerns, of course, satellite systems using the frequency-sharing technique. In the present paper an already proposed method to predict the degradation of the carrier-to-interference (C/I) ratio due to the above sources is properly modified by taking into account ice crystals and raindrop canting angle effects. The novel assumptions reflect upon the more accurate estimation of cross-polarization discrimination and thus contribute to the reliable design of the system being interfered with. The present results are compared with the so far existing ones. The sensitivity of various parameters affecting the interference performance of the system is investigated. As a general conclusion, the inclusion of the ice crystals along with the raindrop canting angle effects may be of importance in some cases, such as the operation in the K band combined with the circular incident polarization, for the accurate estimation of the degradation of the total (C/I) ratio.

A stochastic dynamic model for the induced rain attenuation on multiple radio links is presented in this paper. The model is considered as a generalization of the well-known and wellaccepted Maseng-Bakken model in -dimensions. It incorporates the spatial and time behavior of the rain attenuation phenomena and provides an analytical expression for the transition probability distribution. It consists of a system of stochastic differential equations (SDEs), which, except for the solid mathematical formulation of the correlated rain attenuation stochastic processes, constitutes the general framework for the calculation of other statistical quantities useful for the radio system designers. The long-term statistics and the dynamic properties of rain attenuation are used for the parameterization of the model, without the constraint of any built-in assumptions of the rain field. Finally, the proposed model is used for the generation of correlated rain attenuation time series on multiple satellite communication slant paths and especially to diversity schemes, including site and orbital (angle) diversity. The derived results from the model are tested with respect to experimental long-term statistics for various geometries with very encouraging results. The limitations and the ranges of applicability of the model for Earth-space diversity systems are reported, and the sensitivity of the model on the crucial parameters is discussed.Index Terms-Rain attenuation, satellite link, spatial structure, stochastic differential equations (SDEs).