Search

A simple yet effective time diversity model, referred to as Time Diversity Stratiform Convective EXCELL (TD-SCEX), is presented. The model, conceived to support the design of EHF Earth–space communication systems implementing Fade Mitigation Techniques, takes advantage of the Stratiform Convective EXponential CELL (SC EXCELL) model to predict the joint rain attenuation statistics and, hence, the time diversity gain, starting from the geometrical and electrical characteristics of the link, as well as from the joint rain rate statistics. The model performance is evaluated against the data collected in Milan, Madrid, and Spino d’Adda at Ka-, $Q$ -, and $V$ -bands in the framework of different long-term propagation campaigns. Results indicate that TD-SCEX is a useful tool to predict the effectiveness of time diversity in improving the performance of EHF Earth–space communication systems. [ABSTRACT FROM AUTHOR]

A frequency scaling model aiming to predict total tropospheric attenuation time series at EHF is presented. One version of the model [total attenuation frequency scaling (TAFS)] is more accurate but, besides the reference attenuation time series at low frequency, it also requires additional ancillary inputs (e.g., radiometric data and information on the raindrop size distribution); a second version (S-TAFS) is simpler, though at the expenses of a slightly worse performance. Both TAFS and simplified TAFS (S-TAFS) first rely on isolating the attenuation induced by different atmospheric constituents, each of which is separately up-scaled to the target frequency. The two methods are tested against a full year of data collected at Ka-band and $Q$ -band at Politecnico di Milano, Milan, Italy, in the framework of the Alphasat Aldo Paraboni propagation experiment. Results indicate that both methods offer a very good accuracy in scaling the total attenuation from Ka- to $Q$ -bands, both in terms of first-order statistics and of time series. This corroborates the use of TAFS and S-TAFS to predict the total tropospheric attenuation at much higher frequency bands (e.g., the $W$ -band), for which no measurements are currently available, starting from the largely available Ka-band measurements. [ABSTRACT FROM AUTHOR]

A model is presented that extends the applicability of the propagation data collected during a long measurements campaign in a particular site and for a particular radiolink, to a generic link in a generic site. In fact, the objective of the model is to create a set of attenuation time series to be used in the design of advanced TLC systems. The model assumes that the marked differences of the rain statistics observed in various locations are, in first approximation, mainly due to the different frequency of occurrence of the various rainy events rather than to their shape. Starting from this assumption the model selects, from a large database of rain attenuation events collected in a particular site, a subset that, after an appropriate frequency and elevation scaling, can be used to represent time series of attenuation recorded in other experimental conditions (as for both site and link). The model has been applied to the attenuation data collected at Spino d'Adda (Milan, Italy) during the ITALSAT propagation campaign in order to simulate attenuation time series in several different links and sites. The model demonstrated good performance both in link conditions and climates, similar and different from the Spino d'Adda ones. [ABSTRACT FROM AUTHOR]

We report experimental statistics on the peak factor of rain attenuation time series at 18.7 GHz, in a 37.7° slant path to satellite Italsat, near Milan (Northern Italy). The peak factor is substantially independent of the month of the year, and significantly dependent on the maximum attenuation of the rain event An empirical best-fit formula summarizes the results. The results can be useful to test mathematical synthesizers of rain attenuation time series. [ABSTRACT FROM AUTHOR]

Abstract-In the framework of the ITALSAT campaign various European institutions carried out propagation measurements at V band. In this frequency band, signal reception in a satellite-to- Earth or Earth-to-satellite path may suffer severely from signal attenuation due to meteorological effects such as rain, snow, hail, fog, clouds, etc., where rain provides the most significant contribution. In this paper, a joint analysis of the ITALSAT propagation measurement campaigns at 39.6 GHz (precisely 39.592 GHz) carried out at both Oberpfaffenhofen, close to Munich, Germany, and Spino d'Adda, close to Milan, Italy, is presented. For both stations long-term attenuation statistics are available and reveal that signal attenuation due to meteorological effects depends very much on the season and on the time of the day. Signal attenuation can be compensated by an appropriate fade margin. In this paper, we show that the required fade margin to guarantee a target link availability has to be chosen very carefully, since it depends very much on the time interval upon which availability is defined. We consider complete years, ITU-R recommendations, all single months of the year, worst months, and spring, summer, fall, and winter. Furthermore, we evaluate diurnal variations for four time intervals: 00:00-06:00, 06:00-12:00, 12:00-18:00, and 18:00-24:00. [ABSTRACT FROM AUTHOR]

The experimental characterization of tropospheric effects on electromagnetic waves relies on the reception of a beacon signal transmitted by a satellite. The total tropospheric attenuation can be derived from these measurements in combination with additional information, specifically the attenuation due to atmospheric gases, in turn derived from ancillary instruments or data sources. When available, this information is obtained from a cosited radiometer. This article presents three alternative procedures to estimate the gas attenuation that can be used in the absence of this instrument. The first one makes use of zenith total delay data obtained from the global navigation satellite system (GNSS) receivers and additional meteorological data. The second one relies on atmospheric profiles gathered from radiosonde observations and/or numerical weather prediction (NWP) products. The third one only makes use of standard atmospheric profiles. The accuracy of the procedures, when used in this application, is compared with the reference total tropospheric attenuation derived with the support of radiometric data, exploiting the Alphasat beacon measurements collected in Milan, Italy, in 2017. The results indicate that a better accuracy (average root mean square (rms) error below 0.1 dB when compared with the use of a radiometer) is achieved by using GNSS data because of their finer temporal resolution. Nonetheless, the three procedures can be equally recommended, their use being conditioned to the availability of the appropriate data in the area around the experimental site. [ABSTRACT FROM AUTHOR]

The results from 1 year of data collected during an electromagnetic wave propagation experiment at ${E}$ -band are presented. The research activity originates from the collaboration between Politecnico di Milano, Milan, Italy, and the Huawei European Microwave Centre in Milan, which installed short (325 m) terrestrial links operating at 73 and 83 GHz, connecting two buildings in the university main campus. The received power data are processed, using a novel approach, to identify rain events and to remove the wet antenna effect, with the aim of accurately quantifying the fade induced by precipitation, $A_{R}$. Moreover, $A_{R}$ is estimated by taking advantage of the ancillary data collected by the laser-based disdrometer collocated with the link transceivers. The results definitely point out the higher prediction accuracy achieved by exploiting the information on the rain drop size. A full year of data are used as reference to test the accuracy of the statistical prediction model for terrestrial links currently recommended by the ITU-R, which reveals a large overestimation. Finally, alternative models providing a higher accuracy are proposed and their accuracy assessed. [ABSTRACT FROM AUTHOR]