Nicolas Jeannin

Smart gateways for terabit/s satellite

To reach the terabit per second of throughput, telecommunication satellites cannot make use of frequency below Ka band only. Therefore, the use of broad portion of the spectrum available at Q/V (40/50 GHz) band is foreseen for the feeder link. This study presents the evaluation of performances of different macro-diversity schemes that may allow mitigating the deep fades experienced at Q/V bands by introducing cooperation and a limited redundancy between the different gateways of the system. Two different solutions are firstly described. The performances resulting from the use of those assumptions are derived in a second stage.

A Large-Scale Space-Time Stochastic Simulation Toolof Rain Attenuation for the Design and Optimization of Adaptive Satellite Communication Systems Operating between 10 and 50 GHz

The design and optimization of propagation impairment techniques for space telecommunication systems operating at frequencies above 20 GHz require a precise knowledge of the propagation channel both in space and time. For that purpose, space-time channel models have to be developed. In this paper the description of a model for the simulation of long-term rain attenuation time series correlated both in space and time is described. It relies on the definition of a stochastic rain field simulator constrained by the rain amount outputs of the ERA-40 reanalysis meteorological database. With this methodology, realistic propagation conditions can be generated at the scale of satellite coverage (i.e., over Europe or USA) for many years. To increase the temporal resolution, a stochastic interpolation algorithm is used to generate spatially correlated time series sampled at 1 Hz, providing that way valuable inputs for the study of the performances of propagation impairment techniques required for adaptive SatCom systems operating at Ka band and above.

Distribution of Tropospheric Water Vapor in Clear and Cloudy Conditions from Microwave Radiometric Profiling

Abstract A dataset gathered over 369 days in various midlatitude sites with a 12-frequency microwave radiometric profiler is used to analyze the statistical distribution of tropospheric water vapor content (WVC) in clear and cloudy conditions. The WVC distribution inside intervals of temperature is analyzed. WVC is found to be well fitted by a Weibull distribution. The two Weibull parameters, the scale (λ) and shape (k), are temperature (T) dependent; k is almost constant, around 2.6, for clear conditions. For cloudy conditions, at T −10°C, k displays a maximum in such a way that skewness, which is positive in most conditions, reverses to negative in a temperature region approximately centered around 0°C (i.e., at a level where the occurrence of cumulus clouds is high). Analytical λ(T) and k(T) relations are proposed. The WVC spatial distribution can thus be described as a function of T. The mean WVC vertical profiles for clear and cloudy conditions are well described b...

Inter-annual variability, risk and confidence intervals associated with propagation statistics. Part I: theory of estimation

SUMMARY This set of two companion papers aims at providing a statistical framework to quantify the inter-annual variability observed on the statistics of rain attenuation or rainfall rate derived from Earth-space propagation measurements. This part I is more specifically devoted to the theoretical study of the variance of estimation of empirical complementary cumulative distribution functions (ECCDFs) derived from Earth-space rain attenuation or rainfall rate time series. To focus the analysis on the statistical variability but without loss of generality, synthetic rain attenuation time series are considered. A large variability on the ECCDFs, which depends on the duration of the synthetic data, is first put into evidence. The variance of estimation is then derived from the properties of the statistical estimator. The formulation is validated numerically, by comparison with the ECCDF variances derived from the synthetic data. The variance of the fluctuations around the CCDF is then shown to be dependent on the average of the correlation function of the time series, on the probability level and on the measurement duration. This variance of estimation is needed as a prerequisite in conjunction with the knowledge of the climatic variability to characterize the yearly fluctuations of propagation statistics computed from experimental time series. The extensions from simulations to experiments as well as the application to system planning are detailed in part II. Copyright

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

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.

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

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 large scale, high resolution channel model for propagation impairment techniques design and optimization

As the impairments due to rain on the propagation channel for frequency bands such as Ka or Q/V have to be compensated by adaptive fade mitigation techniques, optimized radio resource management needs to be implemented, which requires a coarse knowledge of spatio-temporal dynamic of the attenuation due to rain. In this paper a model able to emulate the space-time dynamic of the attenuation due to rain on a satellite coverage is presented. It consists of a stochastic model that is constrained by the outputs of a reanalysis model. The spatial resolution of the modeling is of 1 km and the temporal one of 0.1 h. A stochastic interpolation model is then used to get a temporal resolution of 1s more suitable to study fade dynamic.

Inter‐annual variability, risk and confidence intervals associated with propagation statistics. Part II: parameterization and applications

SUMMARY This set of two companion papers aims at providing a model for the inter-annual variability of earth-space propagation statistics and for the inherent risk and CIs. In part I, it was proposed to model the yearly variance σ² of empirical complementary CDFs so that where is the variance of estimation, the inter-annual climatic variance and p the long-term probability. Particularly, an analytical formulation of was derived and parameterized from synthetic rain attenuation data. Considering the statistical framework developed in part I, this part II is specifically devoted to the parameterization of the variance of estimation from experimental data of rain attenuation and rainfall rate. Then, a methodology to model and parameterize worldwide the inter-annual climatic variance is presented. The model of yearly variance of the empirical complementary CDFs is finally compared against yearly experimental variances derived from data collected worldwide. The knowledge of this variability is very useful for system design as it allows the risk on a required availability and associated with a given propagation margin to be quantified. Copyright

A Review of Channel Simulators for Heterogeneous Microwave Networks

A review is performed of the current simulation tools able to produce simultaneous dynamic fading, due to a range of mechanisms, experienced by heterogeneous networks of SHF and EHF radio links. The primary focus is fading due to rain. A taxonomy of tools is proposed, based on the methods used to generate fields of meteorological parameters. The capabilities, deficiencies, and futures of these tools are discussed, and a series of research questions are proposed.

Scintillation modelling in troposphere using Multiple Phase Screen

Microwaves propagation modelling in clear air troposphere i.e. without rain is investigated. Large scale variations of refractivity are computed from mesoscale meteorological modelling. Small scale variations are deduced from large scale considering that the inertial regime of Kolmogorov spectrum is established. The propagation effects are estimated applying launching ray to take into account large scale refractivity effects and resolution of Parabolic Wave Equation with Multiple Phase Screen technique for small scale. The proposed approach has been evaluated versus earth satellite measurements of log-amplitude scintillation measured at Louvain-la-Neuve.