Study of real-time estimation of the power attenuation due to rainfall along microwave link

The problem of rainfall monitoring is a topic task in areas where precipitations are characterized by high intensity and very fast development. Tuscany is a region interested by flood and logistic problems due to strong intensity storms. The topic task is to find a rainfall method that can permit to monitor in real time risk areas so that, in case of hazard, citizens can be alerted earlier. Nowadays rain gauges, weather radar, microwave networks and satellite sensing are the most employed approaches to the task of rainfall monitoring. Unfortunately, all of these methods show substantial weakness that, in different ways, limit their employment in any scenario. Although the attenuation of a microwave link is not entirely due to rain, and generally the precipitation events are characterized by a simultaneous multiple status of water, from the point of view of both the probability of occurrence and the severity of effect, the rain scattering is however the most important of the hydrometeor phenomena, especially for operative frequencies above 10 GHz. In this thesis a novel method for rainfall monitoring has been proposed: it is based on the employment of an opportunistic commercial kit for satellite internet services, operating in KA-band. Since the signals within this band are particularly affected by hydrometeors fading, in order to guarantee a continuity of the service in all-weather conditions, the employed device needs to carry out a continuous adjustment of the uplink transmitted power in function of the intensity of the signal received from the satellite. This mechanism, that gives to the service a certain weather independency, is the basic principle of the proposed low-cost digital rain gauge. This power-control technique, essential for KA-band satellite internet applications, can be exploited to measure in real time the signal fading induced by hydrometeors along the Tropospheric segment of the Earth-space link. The proposed algorithm is named Rainfall rate EsTimation - Attenuation Based (RET-AB): it consists on collecting data with the KA-band system and then it processes them in order to retrieve the cumulated rainfall rate along the microwave link. Two measurement campaign have been held in order to validate the results obtained by the whole system.