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Proceedings ArticleDOI

Using meteorological data for clear sky and cloud attenuation in Belgium and India

TL;DR: In this paper, a concurrent radiometer is used to measure the brightness temperature, which enables the accurate estimation of the total attenuation along the path in the absence of scattering, and produce the Integrated Liquid Water (ILW) and Integrated Water Vapour (IWV) content.
Abstract: Future High Throughput Satellite Communication Systems and Earth Observation Satellite Data Download foresee the use of frequencies in Ka band and above because those frequency bands offer advantages in terms of bandwidth and capacity. In that frequency range, the degradation due to the troposphere becomes important and the designers need a better estimate of the degradations and more specifically the attenuation due to gases and clouds. Even if the specific attenuation is small, except in the frequency band where resonance is present (such as 60 GHz for oxygen), it is always present. The meteorological data available worldwide are now currently used for the estimation of the attenuation due to oxygen, water vapour and clouds [1] [2]. Satellite propagation campaigns are ongoing for the accurate determination of attenuation models in Ka and Q band, using for example the Alphasat satellite from the European Space Agency [3], at 19.7 GHz and 39.4 GHz. The beacon receivers measure directly the power of the beacon received from the satellite but they suffer from various types of instabilities due to tracking inaccuracies, temperature effects, etc and cannot measure the total attenuation of the beacon, in the absence of an external reference (excess attenuation measurement). A concurrent radiometer measures the brightness temperature, enables the accurate estimation of the total attenuation along the path in the absence of scattering, and produce the Integrated Liquid Water (ILW) and Integrated Water Vapour (IWV) content. The cost of the equipment is however high and only a few experimenters use a radiometer [4].
Citations
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Journal ArticleDOI
TL;DR: An empirical model is proposed for prediction of attenuation due to clouds and fog based on the Rayleigh approximation model and proved to be better than the ITU-R model.
Abstract: The latest trends in mobile technology have increased the need for higher spectrum bands from every sector of using wireless applications. As the internet is growing rapidly it has increased the need for wireless services, which require radio spectrum and thus becoming more congested. Engineers show that due to high demand for spectrum, government authorities are regularly introducing schemes to regulate the use of spectrum. New researches are enhancing to resolve the crisis. In order to fix the spectrum for future technologies, propagation studies are required. In this paper an empirical model is proposed for prediction of attenuation due to clouds and fog based on the Rayleigh approximation model. In this model a new concept of calculating dielectric constants of water are also introduced. The implementation results of the proposed model are compared with the other cloud attenuation models. The proposed model proved to be better than the ITU-R model.

10 citations

References
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Journal ArticleDOI
TL;DR: In this paper, the authors improved the accuracy of the simplified method for water-vapor attenuation at millimeter-wave on Earth-space links by taking into account the dependence of the water vapor mass absorption coefficient on the reference site altitude, which is investigated by taking advantage of an extensive set of radiosonde observations (RAOBS) collected in several sites worldwide.
Abstract: This contribution focuses on improving the accuracy of the simplified method currently recommended by the ITU-R for the prediction of water-vapor attenuation at millimeter-wave on Earth-space links (Annex 2, paragraph 2.3 of recommendation ITU-R P.676-10), which receives as input only the local integrated water-vapor content $V$ . The main improvement to such model originates from taking into account the dependence of the water-vapor mass absorption coefficient $a_{V}$ on the reference site altitude, which is investigated by taking advantage of an extensive set of radiosonde observations (RAOBS) collected in several sites worldwide and characterized by high accuracy and reliability. Tested against attenuation estimates obtained from the mass absorption models coupled with the mentioned RAOBS data, the model’s prediction accuracy turns out to improve significantly with respect to the current recommendation and to be less dependent both on the operational frequency (20–100 GHz range) and on the considered site.

23 citations

Proceedings ArticleDOI
10 Apr 2016
TL;DR: In this paper, the first phase (data preprocessing), daily files of normalized duration are developed and a flag vector is generated. Excess attenuation and total attenuation are separately calculated in the following processing phases, and the reference level is calculated on an event-by-event basis, and obtained from GNSS-based gas attenuation in the second one.
Abstract: Universidad Politecnica de Madrid (UPM) is participating in the Alphasat propagation experiment by measuring the copolar level of the Q-Band beacon at 39.4 GHz. In this paper the processing procedures are discussed and exemplified by their application to the first year of measurements (April 2014 to March 2015). In the first phase (data pre-processing), daily files of normalized duration are developed and a flag vector is generated. Excess attenuation and total attenuation are separately calculated in the following processing phases. The reference level is calculated on an event-by-event basis in the first case, and obtained from GNSS-based gas attenuation in the second one. The different procedures are described and some examples of events are presented together with statistics of the first year of measurements.

11 citations