1,721,203 research outputs found
On the Relationship Between the Spatial Correlation of Point Rain Rate and of Rain Attenuation on Earth-Space Radio Links
No full textThis contribution presents an analytical expression to predict the spatial correlation of the rain attenuation A impairing two Earth-space radio links in a site diversity configuration (A) as a function of the spatial correlation of the rain precipitation affecting the area (R), of the distance between the two stations d and of the electrical and geometrical characteristics of the links. Well-established properties of the rain field (i.e. quasi-ergodicity and spatial stationarity) are exploited in the derivation of the proposed analytical expression, whose accuracy is evaluated by means of an extensive set of rain field data collected by the NIMROD weather radar network in the UK. Results indicate a satisfactory prediction performance in the 10-50 GHz frequency range, with negligible dependence on the site separation distance d and on the electrical and geometrical characteristics of the system
Characterization of Indoor Visible Light Communication Channels and Design of a DCO-OFDM System
No full textA physically based method for the conversion of rainfall statistics from long to short integration time
No full textA new physically based methodology for the derivation of the complementary cumulative distribution function (CCDF) of point rain
rate with 1-minute integration time, P(R)1, from a rain rate CCDF with longer integration time, P(R)T , up to 60 min is presented. The method
is based on the simulation of the integration process of a virtual raingauge, over which the population of synthetic exponential cells, provided by
the EXCELL model for the representation of the local meteorological environment, translate according to the local mean yearly wind velocity
at the 600 hPa isobar level, extracted from the ERA-15 database. The performance of the proposed conversion method is assessed against an
extensive database of rainfall statistics measured in various climatic regions and with different integration times. Results, compared with those
achieved by the ITU-R conversion method currently in force, highlight the benefits of using a physical approach to the conversion of rainfall statistics
Preliminary results from a physically-based methodology for the evaluation of a time diversity system
No full textThe SC EXCELL Model for the Prediction of Monthly Rain Attenuation Statistics
No full textThis contribution presents the prediction of monthly rain attenuation statistics by means of the Stratiform/Convective (SC) EXCELL model. The assumption put forth in this contribution is that, although developed for the prediction of yearly statistics, thanks to its solid physical basis, SC EXCELL can be applied as is also to estimate monthly rain attenuation statistics, provided that suitable inputs (i.e. monthly rain rate statistics and monthly rain height) are used. Preliminary tests are carried out to validate this assumption against the extensive set of rain attenuation data collected at the experimental station of Spino d’Adda during the Italsat propagation experiment (years 1994-2000). The results obtained indicate that SC EXCELL offers satisfactory predictions both of yearly and monthly rain attenuation statistics, the accuracy of the latter being mainly limited by the statistical stability of the measurements
The SC EXCELL model for prediction of rain attenuation on terrestrial radio links
No full textThe SC EXCELL (Stratiform/Convective EXponential CELL) model, originally devised for the prediction of the complementary cumulative distribution function of rain attenuation (henceforth P(A)) on Earth-space radio links, is tested here in its ability to predict also the P(A) on terrestrial links. Thanks to its physical soundness in representing the rainfall environment, the proposed method does not require any calibration procedure on existing data, as is typically the case of most of the semi-empirical models proposed so far. When tested against the global DBSG3 database made available by the International Telecommunication Union - Radiocommunication Sector (ITU-R), the proposed model shows an improvement in the prediction accuracy with respect to the method currently recommended by the ITU-R
Joint Effects of Clouds and Rain on EHF Satellite Communication Systems
No full textThis contribution addresses the evaluation of the simultaneous impact of clouds and rain on electromagnetic waves in the EHF band. To this aim, MultiEXCELL and SMOC, two physically-based models recently developed to synthesize realistic rain and cloud fields, are employed. Taking advantage of their physical soundness, the two models are combined to derive, as an example, the simultaneous attenuation due to rain and clouds on a geostationary link operating at 39.6 GHz, as well as the gain that a two-site diversity system would achieve
The impact of space and time averaging on the spatial correlation of rainfall
Full text linkNowadays a huge amount of data is available for the statistical characterization of rainfall worldwide, although unfortunately not always with the adequate spatial and temporal resolution required for the very high demanding telecommunication applications. On the basis of the NIMROD radar network composite rain maps, first, this paper investigates separately the impact of space or time integration on the spatial correlation of rainfall r, a key parameter for most Propagation Impairment Mitigation Techniques (PIMTs), as well as for many prediction models such as time-space rain field generators. Analytical formulations are proposed to model the average trend of r with the distance d between two sites as a function of the integration time T or the integration area A, which, in turn, can be used to de-integrate the spatial correlation information estimated respectively from networks of raingauges with long integration time or from radar data with coarse spatial resolution. As an example, the last part of the paper compares the spatial rain decorrelation trends estimated by a database of radar maps collected in Northern Italy with the ones de-integrated from products of meteorological re-analyses (ERA40) or Earth Observation missions (TMPA 3B42)
A model for rain attenuation prediction in single and site diversity earth-satellite links
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