A comprehensive meteorologically oriented methodology for the prediction of wave propagation parameters in telecommunication applications beyond 10 GHz

Abstract

This paper presents a new approach for the prediction of propagation parameters (such as rain attenuation, site diversity gain, interference by rain scattering, etc.) in telecommunication applications beyond 10 GHz. It consists of a comprehensive theory allowing the full exploitation of the large amount of meteorological data available today. The method is based on a recently devised statistical model of the rain horizontal structure (Capsoni et al., this issue), whose parameters can be determined on the basis of the local statistical distribution of the point rainfall intensity. A test of the ability of this method in predicting attenuation statistics is performed using data collected in Europe with the satellites SIRIO and OTS (COST 205, 1985). The excellent results obtained encourage the application of the model to the statistical prediction of other parameters pertaining to propagation. 1. FOREWORD This paper presents a new approach for the prediction of propagation parameters (such as rain attenuation, site diversity gain, interference by rain scattering, etc.) in telecommunication applications beyond 10 GHz. It consists of a comprehensive theory allowing the full exploitation of the many meteorological These considerations are here applied to the rain cell model proposed by Capsoni et al. [this issue]. It is shown how they lead to a very accurate attenuation prediction method which is described in detail step by step and assessed against data collected during the COST 205 project in Europe [COST 205, 19853.It is noted that this is only an example of an applidata acquired by radars and rain gauges. cation of the principles here presented, which areThe basic concept underlying this theory is that more general and, due to their applicability to many the rain structures causing "events" of interest for parameters, they offer a tool for linking these parampropagation of radio waves (rain cells, stratified rain, eters to each other (which is necessary when data etc.) are quite similar at each site, at least in their must be extrapolated to different conditions or corngeneral characteristics, and what characterizes the bined in order to evaluate an overall system perlocal behavior is the different probabilities of oc-formance). currence of these structures. It follows that, if we know them with sufficient 2. THE SUPERPOSITION PRINCIPLEaccuracy and possess good models for their description, the problem of predicting propagation parame-Let us suppose that the random process describing ters reduces to that of determining their probability a given propagation parameter is generated by the of occurrence. movement of the abovementioned rain structures in

HYCELL—A new hybrid model of the rain horizontal distribution for propagation studies: 2. Statistical modeling of the rain rate field

“…The computation of the third derivative of P r with respect to lnR would be facilitated by the use of an analytical approximation of P r . In such a way, Capsoni et al [1987a] proposed to approximate P r by a function differentiable with respect to lnR, in the form:…”

“…The method relies on the rain cell modeling by EXCELL [Capsoni et al, 1987a[Capsoni et al, , 1987b and allows one to fill in the observation area A o with a population of cells having exponential profiles and rotational symmetry. To determine the rain cell spatial density over A o , Goldhirsh [2000] uses the analytic formulation of Capsoni et al [1987b], slightly corrected by Awaka [1989].…”

HYCELL—A new hybrid model of the rain horizontal distribution for propagation studies: 1. Modeling of the rain cell

“…When discussing the structure of rain field without considering the peak number inside the rain entities as a criterion of classification, it seems more correct to use the term ''rain area.'' In the past, in the literature about the rain field structure in relation with the radioelectric propagation, the above distinction was not considered and the term ''rain cell'' was mainly used [Misme and Waldteufel, 1980;Crane, 1982Crane, , 1996Crane and Shieh, 1989;Capsoni et al, 1987aCapsoni et al, , 1987b. In the present work, focused on the propagation problem, this convention is used, firstly not to confuse the reader and, secondly, because we consider mainly rain entities of small area and because, as will be recalled below, most small rain areas have a single maximum and thus deserve to be termed ''cell.…”

“…These basic considerations underline the difficulty to model the rain rate horizontal distribution within the cells by means of a single mathematical function. Indeed, if an exponential function, as defined by Capsoni et al [1987b], accounts for the spatial extent of the stratiform component, it is not always adapted to the description of the rain rate horizontal distribution in the convective part of the cell. Moreover, isolated punctual maxima of the rain rate are not observed in nature.…”

“…[6] In this context, Capsoni et al [1987aCapsoni et al [ , 1987b proposed to model the horizontal structure of rain cells by the EXCELL model. According EXCELL, the rain cells are of elliptic shape and the rain rate R within the cells decays exponentially around a single maximum.…”