L. da Silva Mello

Unified method for the prediction of rain attenuation in satellite and terrestrial links

In this paper, a semi-empirical method for the prediction of rain attenuation in slant paths and terrestrial links is proposed. The method uses the same simplified model of equivalent rain cell that is the basis for the ITU-R rain attenuation prediction methods but, additionally, the concept of an effective rain rate is introduced. This allows the use of the full rainfall rate distribution for the prediction of the rain attenuation distribution and the unification of the slant path and terrestrial links prediction algorithms. The numerical coefficients in the method’s expressions were derived by multiple non-linear regressions using the experimental data currently available in the ITU-R data banks. Test results indicate that the proposed method provides significant improvement over the current ITU-R methods.

Review of Rain Attenuation Studies in Tropical and Equatorial Regions in Brazil

This paper presents a review of rain attenuation studies based on measurements performed since 1987 in tropical and equatorial regions of Brazil. The terrestrial measurements include long term measurements for frequencies between 11 and 38 GHz at 20 links. The satellite measurements have been performed in the Ku band using radiometers and beacon receivers at 10 sites

Rain Attenuation Time Series Synthesizer Based on the Gamma Distribution

This letter describes the application of rain attenuation time series synthesizers to terrestrial links in tropical regions. A model based on the Gamma distribution is developed and results are compared to those obtained with a lognormal synthesizer. The model parameters were retrieved from data collected during two years of experimental measurements at terrestrial links operating at 15 GHz. Long-term statistics of rain attenuation and fade slope obtained from synthesized time series are tested against the corresponding ones derived from experimental data. Useful empirical expressions for the synthesizers dynamics parameters are derived.

Rainfall induced satellite beacon attenuation on three 12 GHz links in equatorial and tropical Brazil

This paper presents the results for the statistical analysis of rainfall induced attenuation on three satellite beacon links located in the equatorial and tropical regions of Brazil. The results and database obtained during the course of this study may be of help in the design of cost-effective satellite communication systems in regions subjected to heavy rainfall regimes.

Fade slope statistics for three 12-GHz satellite beacon links in Brazil

The fade slope is defined as the rate of increase or decrease of attenuation over time. The possible correlation between the statistics of fade slope values and attenuation levels is investigated. Results show a direct positive correlation between the mean values of fade slope and the attenuation levels. The distributions of fade slope values present a degree of skewness toward the negative values that makes the curves depart from the Gaussian distribution observed by other authors.

Modeling of effective rainfall rate based on attenuation measurements in converging terrestrial links

In this paper, the statistical characterization of the effective rainfall rate parameter is investigated based on the cumulative distribution of measured signal attenuation in converging links with different path lengths, spatial orientations and operation frequencies. Results indicate that the lognormal distribution provides the best fit for the effective rainfall rate. Also, an empirical expression for the effective rainfall rate as a function of path length and link orientation was obtained.

Modified rain attenuation prediction method considering the effect of wind direction

The method currently recommended by the ITU-R for the prediction of rain attenuation in terrestrial line-of sight links considers an equivalent path length over which the rain intensity is assumed to be constant. In other methods, the spatial and temporal variations of the rainfall rate along the path are characterized by an effective rainfall rate that is dependent on the actual path length. Based on experimental measurements, this paper presents a modified effective rainfall rate method that includes the prevailing wind direction during rainy conditions as an additional parameter for the prediction of rain attenuation. The wind direction, which can be obtained from meteorological databases with global coverage, is shown to significantly improve prediction accuracy.

Evaluation of ITU-R rain attenuation prediction methods for terrestrial links

In this paper, the evolution of ITU-R rain attenuation prediction methods from previous versions to the most recent one is evaluated in terms of their performance in predicting attenuation, as compared to experimental data collected from 77 terrestrial links located in 16 countries. Test results indicate that the current version performs better than the previous one. However, a prediction method that introduces the concept of effective rain rate and uses the full rainfall rate distribution for the prediction of the rain attenuation distribution is also included in the comparison and outperforms current ITU-R model.

Coexistence of aeronautical mobile telemetry and IMT systems in the 1300–1518 MHz band

This paper presents an evaluation of the adjacent channel operation between Aeronautical Mobile System (AMT) and International Mobile Telecommunication (IMT) systems operating at 1300-1518 MHz frequency band. Three proposed IMT band allocations are considered. Analytical results of interference calculations are compared with simulation results obtained with the SEAMCAT software. Coordination distances between the AMT and IMT systems are obtained.

SFN channel measurements in ISDB-T broadcast system

Distributed radio transmission schemes, as Single Frequency Networks (SFN), can improve signal coverage for digital television (DTV) broadcasting. In this paper, field measurement carried out in a suburban SFN with two synchronized transmitters is reported. It is found that the radio signal coverage of the distributed transmission scheme is distinctly improved when compared to a single transmitter system. Preliminary results