Ieee transactions on antennas and propagation

Current high-throughput satellite (HTS) systems for broadband distributed user access are designed following two main concepts: ▸ The use of Ka band radio frequency (RF) links both for the forward and for the return link; this choice is due to the congestion of lower frequency bands and to the relatively large bandwidth available in the Ka band. Moreover, the RF technology in the Ka band is mature [1], [2]. ▸ The use of multispot coverage: this technique is largely applied to increase the system throughput through frequency reuse and system reconfigurability [2], [3].

Satellite communication and propagation experiments through the alphasat Q/V band Aldo Paraboni technology demonstration payload

MultiEXCELL, a new rainfall model oriented to the analysis of radio propagation impairments which was developed on the basis of a comprehensive rain field database collected by the weather radar sited in Spino d'Adda (Italy), is presented. Single rain cells are modeled by an analytical exponential profile which best represents real single-peaked rain structures. The rain cells' probability of occurrence is analytically derived from the local rainfall statistics. The spatial features of the rain field at mid- and large-scale are investigated through their natural aggregative process. The clusters (aggregates) of cells are studied in terms of distance between individual cells, number of cells per aggregate, and distance between aggregates. Finally, the fractional area covered by rain, which the rainfall spatial correlation strongly depends on, is derived from radar data through the comparison with the same quantity provided by global long-term numerical weather products. The MultiEXCELL procedure for the generation of spatially correlated synthetic rain fields is duly presented and the model's accurateness is preliminary assessed against the available radar dataset. Although MultiEXCELL is mainly oriented to propagation-related applications, its cellular approach may reveal useful also in hydrology, for the prediction/management of water resources, and in meteorology, for the nowcasting of the temporal evolution of rain structures.

MultiEXCELL: A New Rain Field Model for Propagation Applications

Millimeter wave (mmWave) communication is a key technology for fifth generation (5G) and beyond communication networks. However, the communication quality of the radio link can be largely affected by rain attenuation, which should be carefully taken into consideration when calculating the link budget. In this paper, we present results of weather data collected with a PWS100 disdrometer and mmWave channel measurements at 25.84 GHz (K band) and 77.52 GHz (E band) using a custom-designed channel sounder. The rain statistics, including rain intensity, rain events, and rain drop size distribution (DSD) are investigated for one year. The rain attenuation is predicted using the DSD model with Mie scattering and from the model in ITU-R P.838-3. The distance factor in ITU-R P.530-17 is found to be inappropriate for a short-range link. The wet antenna effect is investigated and additional protection of the antenna radomes is demonstrated to reduce the wet antenna effect on the measured attenuation.

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Rain statistics investigation and rain attenuation modeling for millimeter wave short-range fixed links.

The impact of cloud impairments on satellite links is increasing with the employment of higher frequency bands. In this paper, a model for predicting cloud attenuation statistics for satellite communication systems operating from $Ka$ -band to optical range is presented. The cloud attenuation must be accurately quantified for the reliable design of satellite communication systems. A stochastic dynamic model for the generation of integrated liquid water content (ILWC) fields is proposed. The model is based on the stochastic differential equations and incorporates the spatial and temporal behavior of ILWC. Classifying the cloud types based on the cloud vertical extent and using the microphysical properties of clouds, the well-known Mie scattering theory and the global statistics for ILWC by International Telecommunications Union–Radio (ITU-R), a unified space-time model for the prediction of induced attenuation due to clouds for frequencies above $Ka$ -band up to optical range is presented. The proposed model is tested in terms of first order statistics, compared first with ITU-R P.840-6 model and then with data obtained in the literature, showing encouraging results. Moreover, the probability of cloud occurrence for optical satellite single and site diversity system is calculated. Finally, the limitations and the applicability of the proposed model are discussed.

Cloud Attenuation Statistics Prediction From Ka -Band to Optical Frequencies: Integrated Liquid Water Content Field Synthesizer

Next generations of satellite communication systems demand the use of high frequency bands and the effect of the troposphere at these frequencies has a major impact in the signal attenuation. In this context, the objective of the work presented in this paper is to take advantage of the Weather Research and Forecasting (WRF) system, capable of providing reanalysis and forecasts at high resolution, to be able to simulate the atmospheric conditions, to finally estimate the signal attenuation for slant path satellite links beyond 10 GHz. This is of paramount importance to effectively supplant the lack of measurements for the design of new satellite systems.

http://ieeexplore.ieee.org/iel7/6526699/6546197/06546505.pdf

Use of WRF model to characterize propagation effects in the troposphere

In Recommendation ITU-R P.1853-1, a stochastic approach is proposed to generate long-term rain attenuation time series , including rain and no rain periods anywhere in the world. Nevertheless, its dynamic properties have been validated so far from experimental rain attenuation time series collected at mid-latitudes only. In the present paper, an effort is conducted to derive analytically the first- and second-order statistical properties of the ITU rain attenuation time-series synthesizer. It is then shown that the ITU synthesizer does not reproduce the first-order statistics (particularly the rain attenuation cumulative distribution function CDF), however, given as input parameters. It also prevents any rain attenuation correlation function other than exponential to be reproduced, which could be penalizing if a worldwide synthesizer that accounts for the local climatology has to be defined. Therefore, a new rain attenuation time-series synthesizer is proposed. It assumes a mixed Dirac-lognormal modeling of the absolute rain attenuation CDF and relies on a stochastic generation in the Fourier plane. It is then shown analytically that the new synthesizer reproduces much better the first-order statistics given as input parameters and enables any rain attenuation correlation function to be reproduced. The ability of each synthesizer to reproduce absolute rain attenuation CDFs given by Recommendation ITU-R P.618 is finally compared on a worldwide basis. It is then concluded that the new rain attenuation time-series synthesizer reproduces the rain attenuation CDF much better, preserves the rain attenuation dynamics of the current ITU synthesizer for simulations at mid-latitudes, and, if it proves to be necessary for worldwide applications, is able to reproduce any rain attenuation correlation function.

A Rain Attenuation Time-Series Synthesizer Based on a Dirac and Lognormal Distribution

ONERA, the French Aerospace Lab, and CNES, the French Space Agency, are currently running a Ka -band propagation experiment at the Guiana Space Centre (CSG) in Kourou (French Guiana). A rain gauge and a beacon receiver able to record the 20.2 GHz beacon signal of the Amazonas 3 satellite have been deployed. The equipment is operational since January 1, 2017, and the duration of the experiment has been set to three years. This letter addresses some results of the first year of measurements (from January 2017 to December 2017). The annual and monthly complementary cumulative distribution functions of rainfall rate and rain attenuation are presented as well as a comparison with the rain attenuation prediction method recommended in ITU-R P.618-13.

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Propagation Experiment at Ka -Band in French Guiana: First Year of Measurements

A worldwide modelling of integrated liquid water and water vapor content distributions is proposed and evaluated. The knowledge of those distributions is valuable to predict attenuation for Earth-space communication systems operating at frequencies higher than 10 GHz.

Statistical Distribution of Integrated Liquid Water and Water Vapor Content From Meteorological Reanalysis

This paper proposes the use of a Numerical Weather Prediction (NWP) model to emulate site diversity statistics. Particularly, the Weather Research and Forecasting (WRF) model coupled with an Electromagnetic Module (EMM) is used here to generate rain attenuation time series in four sites in south of France. Rain attenuation statistics derived from WRF simulations are then compared to experimental propagation data, collected in single site and site diversity configurations.

L. Castanet

Papers

Use of WRF model to characterize propagation effects in the troposphere

A Rain Attenuation Time-Series Synthesizer Based on a Dirac and Lognormal Distribution

Propagation Experiment at Ka -Band in French Guiana: First Year of Measurements

Statistical Distribution of Integrated Liquid Water and Water Vapor Content From Meteorological Reanalysis

Use of WRF to generate site diversity statistics in south of France