Search

The attenuation due to rain is one of the main impairments in satellite communications. It is well known that rain attenuation is dependent on the elevation angle of the link, being more severe at low elevation angles; this has a definite impact on the design of TLC and data download systems based on low earth orbit (LEO) satellites. As measurements at various elevation angles are seldom available, it is necessary to use prediction and scaling models. This paper presents a simple model to scale long-term rain attenuation statistics as a function of link elevation angle. The model receives as input the known complementary cumulative distribution (CCDF) at a specific elevation and generates the CCDF scaled at other elevation angles.

With the raising interest in aircraft-based visible light communication (VLC) systems, characterizing the amount of sunlight scattered by clouds becomes important for modelling the incoming solar radiation. In fact, sunlight comes through the aircraft windows and affects the receivers as a form of disturbance. In this regard, this paper proposes a Monte Carlo photon transport simulator that provides the spatial scattering function of a water cloud with an arbitrary liquid water content, when it is illuminated by the sunlight coming from a given direction.

The transmission of optical waves through the atmosphere can be severely hampered by adverse weather. This chapter is a state-of-the-art assessment of the models quantifying laser beam attenuation by fog and hydrometeors. The approach used here is, first, to set-up a microphysical model of the interaction between an optical wave and the atmospheric particles, which works as a benchmark. Then, a number of empirical formulas used in the engineering practice are validated against the model. The former are based on simple relations between attenuation and easily-accessible quantities, such as the visibility or the precipitation rate.

This contribution presents a model to generate time series of rain attenuation by adapting a large set of rain attenuation measurements to different locations. The proposed model allows generating rainy and not rainy conditions for multiple stations in a large geographical area, reproducing the actual spatial and temporal variability of the rain process, with limited computational effort. Single site and joint statistics of rain attenuation obtained by the time series of measurements are discussed. The model is used to show the effectiveness, in terms of link margin, of gateway networks in smart diversity arrangement, for different separation distances among sites.

In this paper, we propose a novel method for rain sensing using dual-frequency measurements at 25 and 38 GHz from small-scale Tokyo Tech millimeter-wave network. A real-time algorithm was developed for estimating the rain rate using ITU-R relationships and new coefficients to consider the effects of the rain Drop Size Distribution (DSD). The results show that the proposed algorithm provides the estimation in very good agreement with rain gauge data.

The objective of this paper is to describe recent activities and investigations on FSO and the excellent results achieved within international COST actions (like COST 270, COST 291, COST 297 (HAPCOS)) and the 6(th) EU-framework programme (like SatNEx and CAPANINA). In a first part, the FSO technology is briefly discussed. Then its behaviour in different networking architectures is explained to elaborate its potential and suitability for the future Next Generation Networks (NGN). In a second part, the recent investigations in airborne and satellite application scenarios are discussed. Then, the short-range FSO systems built for last mile connectivity are explained. Finally, our recent investigation results on modelling the FSO channel under fog conditions and atmospheric turbulence are presented. Additionally, some recent major performance improvement results obtained by employing hybrid systems and using some specific modulation and coding schemes are presented.

This contribution is intended to provide a preliminary quantification of the expected atmospheric impairments suffered from a radio wave at frequency above 50 GHz, as it could be theoretically derived by extrapolating the present theoretical and experimental knowledge. We have addressed the role of gases, clouds, scintillation and rain (with emphasis also on the impact of the hydrometeor size distribution) on the attenuation level, the melting layer characteristics and the depolarization of the electromagnetic waves travelling through the atmosphere.