Joël Lemorton

Development and validation of time-series synthesizers of rain attenuation for Ka-band and Q/V-band satellite communication systems

The aim of this paper is to present recent developments in terms of propagation time-series synthesizers, carried out in the framework of the ESA study 16865/03/NL/EC Development of propagation models for telecommunication satellite systems (ONERA Final Report RF 4/07757/DEMR, 2004). The paper is composed of three parts: a review of the initial requirements related to propagation time series for system performance simulation, a description of a collection of rain attenuation time-series synthesizers and of their related input parameters, and a comparative analysis of the output characteristics of these time-series synthesizers as compared with experimental data collected during the OLYMPUS and ITALSAT propagation experiments.

Comparison of various methods for combining propagation effects and predicting loss in low-availability systems in the 20-50 GHZ frequency range

The objective of this paper is to demonstrate the interest of using ‘combined’ prediction models of attenuation (combinations of single propagation effects) for new Ka, V or EHF SatCom systems. These models allow to calculate the attenuation due to gases, clouds, rain and the melting layer. To reach this objective, results of recent propagation campaigns carrying out radioelectrical links in the 20–50 GHz frequency range are used as references. Results from three different propagation experiments are considered in this paper: OLYMPUS results obtained from the DBOPEX database, ITALSAT results obtained by Rutherford Appleton Labs at Chilton (UK) and CELESTE results obtained by ONERA in South of France. Copyright

Classical and On -Demand Rain Attenuation Time Series Synthesis: Principle and Applications

To develop and test real -time Fade Mitigation Techniques control algorithms, propagation time series are needed. An alternative to using real data collected from propagation experiments is to gen erate typical fading time -series making use of climatological characteristics as well as geometrical and radio -electrical parameters of the link. These dynamic channel models must be as global as possible to be used for all the possible link characteristic s. The design of transmission links for interactive SatCom systems can be done in three steps. The first one is based on a worst case link budget requiring an exceeded value for a given percentage of time. For this purpose, ITU -R models can be used. The se cond step consists in the survey of the FMT control loop behavior in some typical cases of impairments. The synthesis of such attenuation events implies a strong need for dynamic channel models in which users can command some events characteristics. It mus t concern in priority the duration of the synthesized rain attenuation event and/or its maximum value. Such channel models are said to produce “on -demand” events. And the last step is the global assessment of the capacity and of the availability of the who le communications system. For such exhaustive studies, time series synthesizers able to reproduce the channel dynamic behavior on a long -term basis (including periods of no rain) are needed. For those reasons, two types of time series synthesizers have bee n developed relying on the same theoretical bases. The first one is directly an improved version of the Maseng -Bakken model which does not produce “on -demand” rain attenuation events. The second channel model enables to command the maximum level and the du ration of rain attenuation events to synthesize. This model can also be used to complete channel models that are not able to produce one sample every second.

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.

A generative MIMO channel model encompassing single satellite and satellite diversity cases

This paper addresses the statistical modeling of MIMO-LMS fading channels. In the absence of accurate experimental results, a statistical model for the characterization of MIMO-LMS channels is proposed based on consolidation of available experimental results for SISO-LMS, SIMO-LMS and MISO-LMS as well as on their extrapolation to the MIMO-LMS and satellite diversity cases of interest.

Methodology of validation of time series synthesize r for the Ka-band satellite propagation channel

To develop and test real-time Fade Mitigation Techniques control algorithms, propagation time series are needed. An alternative to us ing real data collected from propagation experiments is to generate typical fading time -series making use of climatological characteristics as well as geometrical and rad io-electrical parameters of the link. In the framework of the European action COST 280, different channel models have been studied in order to synthesize propagation time se ries. Starting from the availability of these channel models, the next step consists now in evaluating their physical soundness with respect to the dynamics of the propagation channel. The objective of this paper is to present a method of validation of these time series synthesizer s, to be applied with respect to experimental propagation time series. Indeed, if in the past, some testing activities of conventional statistical prediction models have been car ried out especially in the framework of ITU-R, these methods allow only a validation with res pect to long-term statistics. In the present context, new validation techniques have to be developed to assess the short-term behavior of these synthesizers. Starting from a databank of experimental measurements a Principal Component Analysis of the rain fade events is carried out in order to infer the typical characteristics of propagation fade events that h ave to be generated by the time series synthesizers. This analysis allows to identify the most discriminant relations between fade events characteristics: attenuation, fade slope, fad e duration, spectrum characteristics, etc…, in order to check if the generated fade events are representative of the propagation channel dynamics. Then, a short term validation methodology relying on the use of the Mahalanobis distance is proposed. This metric is considered in order to take into account the

Simplifying the propagation environment representation for LMS channel modelling

A deep knowledge of all propagation effects has become an essential issue to design future communication and navigation systems and optimise their performances. Here, we will target Land Mobile Satellite (LMS) systems, with focus on Global Navigation Satellite Systems (GNSS). The urban environment is one of the most critical for LMS systems, since shadowing, multipath fading and time spreading are often present. This study aims at developing more efficient propagation channel models using physical-statistical approaches. In order to build these models, numerical asymptotic tools are to be used to avoid costly extensive measurements. These tools are theoretically valid for large objects. So, it is necessary to know which level of simplification of the environment is acceptable. Thus, this article performs a rigorous analysis of the influence of small scatterers at different levels of the transmission channel (up to the GNSS receiver), using the exact Method of Moments technique as a reference.

Short- And Mid-Term Prediction Techniques Of Propagation Conditions From Weather Radar Observations. Application to resource management in SATCOM systems

This paper discusses possible scenarios for inclusion of forecasting of rain fields in satellite communication system for the purposes of optimizing the use of layer 1 resources (EIRP, frequencies)

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.

Channel modelling in complex urban environments for testing multipath mitigation methods enhanced by antenna array

Multipaths are one of the major sources of errors for satellite navigation systems. The goal of this article is to present some advances on propagation channel modelling for GNSS mobile users and to show how GNSS receiving algorithms are sensitive to the modelling of the channel. Two channel characteristics are analysed in the paper: the resolution of the environment level of detail, and the resolution of the channel, meaning the number of significant echoes in the tapped-delay line. Particular focus is made on mitigation techniques using antenna arrays to reject multipath. The influence of the channel model will be then interpreted considering three different types of GNSS receiver algorithms, namely conventional DLL/PLL, beam forming and SAGE/STAP algorithm.