Publications

Articles, Thèses, Brevets, Séminaires, Livres, Notes techniques

Recherche

Article de journal

Nonparametric Detection of Nonlinearly Mixed Pixels and Endmember Estimation in Hyperspectral Images

Auteurs : Imbiriba Tales, Bermudez José, Richard Cédric et Tourneret Jean-Yves

IEEE Transactions Image Processing, vol. 25, n° 3, pp. 1136-1151, March, 2016.

Télécharger le document

Mixing phenomena in hyperspectral images depend on a variety of factors, such as the resolution of observation devices, the properties of materials, and how these materials interact with incident light in the scene. Different parametric and nonparametric models have been considered to address hyperspectral unmixing problems. The simplest one is the linear mixing model. Nevertheless, it has been recognized that the mixing phenomena can also be nonlinear. The corresponding nonlinear analysis techniques are necessarily more challenging and complex than those employed for linear unmixing. Within this context, it makes sense to detect the nonlinearly mixed pixels in an image prior to its analysis, and then employ the simplest possible unmixing technique to analyze each pixel. In this paper, we propose a technique for detecting nonlinearly mixed pixels. The detection approach is based on the comparison of the reconstruction errors using both a Gaussian process regression model and a linear regression model. The two errors are combined into a detection statistics for which a probability density function can be reasonably approximated. We also propose an iterative endmember extraction algorithm to be employed in combination with the detection algorithm. The proposed detect-then-unmix strategy, which consists of extracting endmembers, detecting nonlinearly mixed pixels and unmixing, is tested with synthetic and real images.

Lire la suite

Traitement du signal et des images / Observation de la Terre

Article de conférence

Blind Estimation of Unknown Time Delay in Periodic Non-Uniform Sampling : Application to Desynchronized Time Interleaved-ADCS

Auteurs : Vernhes Jean-Adrien, Chabert Marie, Lacaze Bernard, Lesthievent Guy, Baudin Roland et Boucheret Marie-Laure

In Proc. IEEE Int. Conf. on Acoust., Speech Signal Process. (ICASSP), Shanghai, Chine, March 20-25, 2016.

Télécharger le document

Increasing the sampling rate of Analog-to-Digital Converters (ADC) is a main challenge in many fields and especially in telecommunications. Time-Interleaved ADCs (TI-ADC) were introduced as a technical solution to reach high sampling rates by time interleaving and multiplexing several lowrate ADCs at the price of a perfect synchronization between them. Indeed, as the signal reconstruction formulas are derived under the assumption of uniform sampling, a desynchronization between the elementary ADCs must be compensated upstream with an online calibration and expensive hardware corrections of the sampling device. Based on the observation that desynchronized TI-ADCs can be effectively modeled using a Periodic Non-uniform Sampling (PNS) scheme, we develop a general method to blindly estimate the time delays involved in PNS. The proposed strategy exploits the signal stationarity properties and thus is simple and quite generalizable to other applications. Moreover, contrarily to state-ofthe-art methods, it applies to bandpass signals which is the more judicious application framework of the PNS scheme.

Lire la suite

Traitement du signal et des images / Systèmes spatiaux de communication et Autre

A Bayesian Framework for the Multifractal Analysis of Images Uisng Data Augmentation and a Whittle Approximation

Auteurs : Combrexelles Sébastien, Wendt Herwig, Altmann Yoann, Tourneret Jean-Yves, McLaughlin Stephen et Abry Patrice

In Proc. IEEE Int. Conf. Acoust., Speech and Signal Proces. (ICASSP), Shanghai, China, March 20-25, 2016.

Télécharger le document

Texture analysis is an image processing task that can be conducted using the mathematical framework of multifractal analysis to study the regularity fluctuations of image intensity and the practical tools for their assessment, such as (wavelet) leaders. A recently introduced statistical model for leaders enables the Bayesian estimation of multifractal parameters. It significantly improves performance over standard (linear regression based) estimation. However, the computational cost induced by the associated nonstandard posterior distributions limits its application. The present work proposes an alternative Bayesian model for multifractal analysis that leads to more efficient algorithms. It relies on three original contributions: A novel generative model for the Fourier coefficients of log-leaders; an appropriate reparametrization for handling its inherent constraints ; a data-augmented Bayesian model yielding standard conditional posterior distributions that can be sampled exactly. Numerical simulations using synthetic multifractal images demonstrate the excellent performance of the proposed algorithm, both in terms of estimation quality and computational cost.

Lire la suite

Traitement du signal et des images / Observation de la Terre

Impact of SDN on Mobility Management

Auteurs : Tantayakul Kuljaree, Dhaou Riadh et Paillassa Béatrice

In Proc. Advanced Information Networking and Applications (AINA), Crans-Montana, Switzerland, March 23-25, 2016.

Télécharger le document

The software integration with new network architectures via SDN (Software Defined Network) axis appears to be a major evolution of networks. While this paradigm was primarily developed for easy network setup, its ability to integrate services has also to be considered. Thus, the mobility service for which solutions have been proposed in conventional architectures by defining standardized protocols should be rethought in terms of SDN service. Mobile devices might use or move in SDN network. In this paper, we have shown that SDN can be implemented without IP mobility protocol for providing mobility like as Proxy Mobile IPv6 (PMIPv6) that is the solution adopted by 3GPP, with some performance gain.

Lire la suite

Réseaux / Systèmes spatiaux de communication

A Maximum Likelihood Based Unscented Kalman Filter for Multipath Mitigation in a Multi-correlator Based GNSS Receiver

Auteurs : Cheng Cheng, Quan Pan, Calmettes Vincent et Tourneret Jean-Yves

In Proc. IEEE International Conference on Acoustic, Speech and Signal Processing (ICASSP), Shanghai, China, March 20-25, 2016.

Télécharger le document

In complex environments, the presence or absence of multipath signals not only depends on the relative motion between the GNSS receiver and navigation satellites, but also on the environment where the receiver is located. Thus it is difficult to use a specific propagation model to accurately capture the dynamics of multipath signal parameters when the GNSS receiver is moving in urban canyons or other severe obstructions. This paper introduces a statistical model for the line-of-sight and multipath signals received by a GNSS receiver. A multi-correlator based GNSS receiver is also exploited with the advantage to fully characterizing the impact of multipath signals on the correlation function by providing samples of the whole correlation function. Finally, a maximum likelihood-based unscented Kalman filter is investigated to estimate the line-of-sight and multipath signal parameters. Numerical simulations clearly validate the effectiveness of the proposed approach.

Lire la suite

Traitement du signal et des images / Localisation et navigation

Unmixing Multitemporal Hyperspectral Images with Variability: An Online Algorithm

Auteurs : Thouvenin Pierre-Antoine, Dobigeon Nicolas et Tourneret Jean-Yves

In Proc. IEEE International Conference on Acoustic, Speech and Signal Processing (ICASSP), Shanghai, China, March 20-25, 2016.

Télécharger le document

Hyperspectral unmixing consists in determining the reference spectral signatures composing a hyperspectral image and their relative abundance fractions in each pixel. In practice, the identified signatures may be affected by a significant spectral variability resulting for instance from the temporal evolution of the imaged scene. This phenomenon can be accounted for by using a perturbed linear mixing model. This paper studies an online estimation algorithm for the parameters of this extended linear mixing model. This algorithm is of interest for the practical applications where the size of the hyper-spectral images precludes the use of batch procedures. The performance of the proposed method is evaluated on synthetic data.

Lire la suite

Traitement du signal et des images / Observation de la Terre

Séminaire

High Performance Satellite AIS and Radar Data Fusion for Maritime Surveillance

Auteur : Manzoni Vieira Fábio

Seminars of TeSA, Toulouse, March 9, 2016.

Télécharger le document

Maritime surveillance can be performed with information from cooperative souces that include vessel monitoring systems or using radars or image sensors. A solution to deal with the diversity of surveillance scenarios in the presence of non-cooperative ships is the integration of both kinds of sources. Considering an Automatic Identification System (AIS) and a Low Pulse Repetition Frequency Synthetic Aperture Radar (LPRF SAR), a research on improved data fusion techniques is desired to reach high performance in maritime surveillance and is the main subject of this research.

Lire la suite

Traitement du signal et des images / Localisation et navigation

Optimisation de bout-en-bout du démarrage des connexions TCP

Auteur : Chaput Emmanuel

Seminars of TeSA, Toulouse, March 9, 2016.

Télécharger le document

Dans cette thèse, nous proposons un mécanisme appelé Initial Spreading qui permet une optimisation remarquable des performances de TCP pour les connexions de petites tailles, représentant plus de 90% des connexions échangées dans l’Internet. Cette solution est d’autant plus intéressante que pour certaines technologies telles qu’un lien satellite, le temps d’aller retour particulièrement long est très pénalisant, et des solutions spécifiques ont du être implantées qui empêchent l’intégration du satellite dans un système de communication plus large. Nous montrons que l’Initial Spreading est non seulement plus performant, mais surtout plus général car pertinent dans toutes les situations. De plus, peu intrusif, il ne compromet aucune des évolutions de TCP passées ou à venir.

Lire la suite

Réseaux / Systèmes spatiaux de communication

Brevet

Procédé et Dispositif de Mesure des Produits d'Intermodulation par Réflexion d'Ondes Electromagnétiques sur un Objet

Auteurs : Sombrin Jacques B., Albert Isabelle, Soubercaze-Pun Geoffroy et Capet Nicolas

n° FR3025319 A1, March 4, 2016.

Lire la suite

Traitement du signal et des images / Systèmes spatiaux de communication

Article de journal

Splitting up an Optical Beam in a Polarized Component Added to an Unpolarized Component

Auteur : Lacaze Bernard

Journal of Modern Optics, vol. 63, n°15, pp. 1525-1528, March, 2016.

Télécharger le document

The decomposition of an optical beam in a polarized part added to an unpolarized part was studied by G.G. Stokes among numerous other works. Today, the problem is no longer a trigonometric manipulation proper to monochromatic waves, but a problem handling stationary processes with band spectra. In literature, the question seems to be: given some spectral properties and some propagation medium, can we obtain a decomposition? Furthermore, in the case of a positive answer, we have to provide devices for exhibiting solutions. In a linear framework, the problem always has a solution (and even an infinity) whatever the chosen polarization direction. In this paper, we study the links which appear most often between the members of the decomposition.

Lire la suite

Traitement du signal et des images / Autre

ADRESSE

7 boulevard de la Gare
31500 Toulouse
France

CONTACT


CNES
Thales Alenia Space
Collins Aerospace
Toulouse INP
ISEA-SUPAERO
IPSA
ENAC
IMT Atlantique