Approximate maximum likelihood estimation of two closely spaced sources

The performance of the majority of high resolution algorithms designed for either spectral analysis or Direction-of-Arrival (DoA) estimation drastically degrade when the amplitude sources are highly correlated or when the number of available snapshots is very small and possibly less than the number of sources. Under such circumstances, only Maximum Likelihood (ML) or ML-based techniques can still be effective. The main drawback of such optimal solutions lies in their high computational load. In this paper we propose a computationally efficient approximate ML estimator, in the case of two closely spaced signals, that can be used even in the single snapshot case. Our approach relies on Taylor series expansion of the projection onto the signal subspace and can be implemented through 1-D Fourier transforms. Its effectiveness is illustrated in complicated scenarios with very low sample support and possibly correlated sources, where it is shown to outperform conventional estimators

France numérique 2012 - Plan de développement de l\u27économie du numérique

Permettre à tous les Français d’accéder aux réseaux et services numériques L’accès aux réseaux et aux services numériques est devenu l’une des conditions d’intégration dans notre économie, notre société, notre démocratie, notre culture. L’Internet haut débit constitue aujourd’hui, comme l’eau ou l’électricité, une commodité essentielle. À cet égard, le fait que 2 et 4 millions de Français soient durablement exclus de la société de l’information nécessite la mise en place d’un droit à Internet haut débit pour tous, y compris en Outre-mer, afin que chaque Français ait accès au haut débit d’ici à 2012. L’objectif de généralisation de l’accès à Internet haut débit ne doit pas se limiter aux usages fixes mais aussi couvrir la mobilité, qui concerne désormais 85 % des Français. L’opportunité historique que constitue le dividende numérique, ces fréquences libérées par le passage au tout numérique audiovisuel, doit amener à l’affectation d’une ressource suffisante pour le très haut débit mobile sur l’ensemble du territoire. La France, comme les autres pays développés, va connaître une évolution profonde des usages des nouvelles technologies, qui vont nécessiter l’arrivée de débits de plus en plus importants. Cette évolution vers le très haut débit, aujourd’hui centré sur les zones urbaines les plus denses, doit être favorisée. Le passage au tout numérique audiovisuel va permettre d’ici à 2012, l’arrivée de 18 chaînes gratuites nationales pour tous les Français, y compris en Outre-mer. À cet égard, le dividende numérique sera aussi l’occasion de permettre à tous les Français de recevoir les nouveaux services de télévision, qu’il s’agisse de la télévision mobile personnelle ou de la télévision haute définition. Enfin, un outil d’aide à l’équipement et de formation aux usages du numérique, à destination des seniors sera expérimenté pour leur permettre d’accéder plus facilement aux réseaux numériques. Développer la production et l’offre de contenus numériques Développer la production et l’offre de contenus numériques repose sur un double impératif : d’une part assurer la protection des contenus, d’autre part augmenter la disponibilité des oeuvres et des programmes. Un répertoire national des oeuvres numériques protégées pourrait servir d’ancrage aux technologies de protection de contenus, en permettant aux ayant droits et aux opérateurs de l’Internet de repérer les fichiers protégés et de coopérer pour assurer leur gestion. Une réflexion de fond sur la pertinence des Digital Rights Management (DRM) doit être menée pour aboutir à des standards interopérables partout où elles ne peuvent être supprimées. L’État doit par ailleurs rendre plus accessibles les données publiques pouvant donner lieu à une exploitation commerciale, ce qui peut être réalisé par un portail unifié. Ce rapport propose aussi six mesures de réforme de la commission de la copie privée, visant une plus grande transparence aux yeux du consommateur et des règles de fonctionnement adaptées à l’économie numérique

Synthetic aperture radar demonstration kit for signal processing education

A Synthetic Aperture Radar scale model has been developed to improve signal processing teaching. Based on low frequency ultrasound transmission, it is a low cost demonstration kit. The overall software is directly running on Matlab® and allows easy and realtime modifications. This educational tool can be used to illuminate a scene using different waveforms, and then see the effects on the formed image. It can also be used in a more advanced way to test different signal processing in order to improve image focusing or to reduce computation burden

Approximate maximum likelihood direction of arrival estimation for two closely spaced sources

Abstract—Most high resolution direction of arrival (DoA) estimation algorithms exploit an eigen decomposition of the sample covariance matrix (SCM). However, their performance dramatically degrade in case of correlated sources or low number of snapshots. In contrast, the maximum likelihood (ML) DoA estimator is more robust to these drawbacks but suffers from a too expensive computational cost which can prevent its use in practice. In this paper, we propose an asymptotic simplification of the ML criterion in the case of two closely spaced sources. This approximated ML estimator can be implemented using only 1-D Fourier transforms. We show that this solution is as accurate as the exact ML one and outperforms all high-resolution techniques in case of correlated sources. This solution can also be used in the single snapshot case where very few algorithms are known to be effective

Phylogeography, Risk Factors and Genetic History of Hepatitis C Virus in Gabon, Central Africa

BACKGROUND: The epidemiological and molecular characteristics of hepatitis C virus (HCV) infection in the general population have been poorly investigated in Africa. The aim of this study was to determine the prevalence, genotype distribution and epidemic history of HCV in the Gabonese general population. METHODS/PRINCIPAL FINDINGS: A total of 4042 sera collected from adults in 220 villages in all nine administrative areas of the country were screened for antibodies to HCV. HCV NS5B region sequencing was performed for molecular characterization and population genetic analyses. Of 4042 tested sera, 455 (11.2%) were positive. The seroprevalence of HCV varied significantly by administrative area, with the highest rate in Ogooue-Lolo province (20.4%) and the lowest in Ogooue-Maritine province (3.7%). History of parenteral injections, past hospital admission and age over 55 years were independent risk factors for HCV infection (p<0.0001). Phylogenetic analyses showed that 91.9% of the strains were genotype 4 (HCV-4), 5.7% genotype 1 and 2.2% genotype 2. HCV-4 strains were highly heterogeneous, with more than eight subtypes; subtype 4e predominated (57.3%). Coalescence analyses indicated that subtype 4e was the oldest, with an estimated most recent common ancestor of 1702 [95% CI, 1418-1884]. The epidemic profile indicated that it spread exponentially during the first part of the 20th century, probably by iatrogenic transmission. CONCLUSIONS/SIGNIFICANCE: These results confirm the endemicity of HCV subtype 4e in Gabon and show that its spread is due to a cohort effect, with previous, possibly iatrogenic events. More extensive epidemiological studies are needed to better characterize the route of transmission and the dissemination of HCV in Gabon

A mission management system for a fleet of gliders

International audienceThe objective of AGLIMMS project, whose acronym stands for Acoustic GLIders Mission Management System, is to efficiently coordinate a fleet of underwater gliders whose missions are to obtain physical, chemical, biological and/or acoustic measurements on a large 3D sea area. This paper describes planning and supervision functions under development and their integration in a global centralised architecture. A demonstration with three SeaExplorer from Alseamar is planned late 2019

On ordered normally distributed vector parameter estimates

The ordered values of a sample of observations are called the order statistics of the sample and are among the most important functions of a set of random variables in probability and statistics. However the study of ordered estimates seems to have been overlooked in maximum-likelihood estimation. Therefore it is the aim of this communication to give an insight into the relevance of order statistics in maximum-likelihood estimation by providing a second-order statistical prediction of ordered normally distributed estimates. Indeed, this second-order statistical prediction allows to refine the asymptotic performance analysis of the mean square error (MSE) of maximum likelihood estimators (MLEs) of a subset of the parameters. A closer look to the bivariate case highlights the possible impact of estimates ordering on MSE, impact which is not negligible in (very) high resolution scenarios

Temporal signature of a ‘beyond-viewpoint’ exemplar-level processing in visual object recognition

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