Amélioration du filtrage non linéaire dans les modèles d'état par ré-estimation de l'état passé

National audienceCet article propose une amélioration du comportement des techniques de filtrage dans les modèles d'état non linéaires. Pour cela, on introduit des techniques de filtrage de type Kalman étendu, "sans parfum" ou particulaire qui exploitent en particulier la concaténation des équations d'état et d'observation afin de limiter les effets des non linéarités dans la propagation de l'état et d’améliorer l’estimation de l'état 'instant antérieur. On vérifie que les performances obtenues par ces nouveaux algorithmes améliorent souvent les algorithmes de filtrage classiques correspondants

Equilibrage spectral d'une famille de signaux et séquences d'étalement pour le CDMA

National audienceCet article présente une technique de génération de bases orthogonales de signaux, dont les spectres sont optimisés conjointement au moyen d'un critère d'égalisation de l'énergie dans un ensemble de sous-bandes prescrites. Le procédé développé permet en particulier, pour les communications numériques CDMA, de construire en grand nombre des familles de séquences orthogonales dont les spectres sont similaires. On peut ainsi s'affranchir de l'emploi des séquences de mélange dont la synchronisation peut s'avérer délicate dans des contextes tels que les communications sous-marines. On présente ici l'équilibrage obtenu à partir de séquences initiales appartenant à la famille des séquences de Walsh. On illustre de plus l'intérêt de la blancheur spectrale pour la robustesse de la réception vis à vis de canaux multitrajets dans les communications à spectre étalé

Une nouvelle classe d'opérateurs de Teager-Kaiser multidimensionnels basée sur les dérivées directionnelles d'ordre supérieur

This work aims at introducing some energy operators linked to Teager-Kaiser energy operator and its associated higher order versions and expand them to multidimensional signals. These operators are very useful for analyzing oscillatory signals with time-varying amplitude and frequency (AM-FM). We prove that gradient tensors combined with Kronecker powers allow to express these operators by directional derivatives along any n-D vector. In particular, we show that the construction of a large class of non linear operators for AM-FM multidimensional signal demodulation is possible. Also, a new scalar function using the directional derivative along a vector giving the ”sign” of the frequency components is introduced. An application of this model to local n-D AM-FM signal is presented and related demodulation error rates estimates. To show the effectiveness and the robustness of our method in term of envelope and frequency components extraction, results obtained on synthetic and real data are compared to multi-dimensional energy separation algorithm and to our recently introduced n-D operator

Spectral balancing techniques application to CDMA and UWB signaling

International audienceThis paper presents techniques for generating orthogonal bases of signals with jointly optimized spectra, in the sense that they are made as close as possible. To this end, we propose new criteria, the minimization of which leads to signals with close energy inside a set of prescribed subbands. We present a first algorithm that performs this spectrum balancing and that we apply to Walsh-Hadamard codes. As an example, we build balanced Walsh codes in CDMA comunications. Alternatively, we propose another way to perform spectrum balancing in two steps and that makes use of joint diagonalization techniques. As an example application, we show how balancing of Prolate Spheroidal Wave Functions (PSWFs) can be used to build orthogonal families of brief impulses with flat spectra that are of potential interest for Ultra Wide Band (UWB) communications

The parametric propagation in underwater acoustics : experimental results

In underwater acoustics, detection of buried objects in sediments (cables, mines, . . . ) is a complex problem. Indeed, in order to ensure sufficient penetration depth in marine sediments, low frequencies have to be used, implying a low resolution. A solution proposed to solve this problem is the parametric emission based on the nonlinear properties of seawater. This method can generate a low frequency wave from two directional high frequencies beams. The aim of this work is to present experimental results of a parametric propagation. Experiments have been carried out in a water tank in various configurations. These experimental measurements are then compared with simulation results obtained with a numerical model based on a fractional-step method presented at the Underwater Acoustic Measurements conference in 2011

Bases équilibrées et signalisation multidimensionnelle

On envisage ici le problème de la construction d'une base orthonormée, relativement au produit scalaire euclidien, dont les éléments ont tous la même norme vis à vis d'un autre produit scalaire. On propose un algorithme itératif pour réaliser cette opération. Une application possible de cette méthode vise à construire des bases de signalisation pour les modulations numériques multi-dimensionnelles possédant une proportion d'énergie bornée hors d'une bande de fréquences prescrite. Par ailleurs, pour quantifier le gain lié à l'augmentation de dimensionnallité des modulations PSK, on propose une nouvelle formule asymptotique de probabilité d'erreur pour de telles modulations

MIMO communications for inhome PLC networks: measurements and results up to 100 MHz

International audiencePower Line Communications (PLC) is used for information exchange over the lines installed for delivering the electrical power. Inhome PLC is a technology which delivers telecom services to every corner of a household through already existing electrical wiring. In recent years, PLC has emerged as a potential candidate for domestic high bit rate services. The current inhome PLC technology, based on Single-Input Single-Output (SISO) configuration, under achieves the capacity offered by the physical PLC channel. The inhome PLC channel offers multiple signal feed ports as, usually, it comprises of three wires: Phase, Neutral and Protective Earth. The measurements and results presented in this paper demonstrate that up to 90% enhancement in inhome PLC channel capacity is possible by using multiple-input multiple-output (MIMO) technique

On transforming spectral peaks in voice conversion

International audienceThis paper explores the benefits of transforming spectral peaks in voice conversion. First, in examining classic GMMbased transformation with cepstral coefficients, we show that the lack of transformed data variance ("over-smoothing") can be related to the choice of spectral parameterization. Consequently, we propose an alternative parameterization using spectral peaks. The peaks are transformed using HMMs with Gaussian state distributions. Two learning variants and post-processing treating peak evolution in time are also examined. In comparing the different transformation approaches, spectral peaks are shown to offer higher interspeaker feature correlation and yield higher transformed data variance than their cepstral coefficient counterparts

On the use of spectral peak parameters in voice conversion

International audienceThis paper addresses the problem of low transformed data variance, or "over-smoothing," in spectral transformation for Voice Conversion. In examining a classic GMM-based transformation with cepstral coefficients, we show that this problem lies, not only in the transformation model (as commonly assumed), but also in the choice of spectral parameterization. Consequently, we propose an alternative method for spectral transformation using spectral peaks and an HMM with Gaussian state distributions. The spectral peaks are shown to offer higher inter-speaker feature correlation and yield higher transformed data variance than their cepstral coefficient counterparts. Additionally, the accuracy of the transformed envelopes is examined

A new approach to maneuvring target tracking in passive multisensor environment

International audienceThis paper present a new approach to the multisensor Bearing-Only Tracking applications (BOT). Usually, a centralized data fusion scheme which involves a stacked vector of all the sensor measurements is applied using a single estimation filter which copes with the non-linear relation between the states and the measurements. The aforementioned approach is asymptotically optimal but suffers from the computational burden due to the augmented measurement vector and transmission aleas like delays generated by the bottleneck that occurs at the fusion center. Alternatively, since the Cartesian target positions can be determined by fusing at least 2 infrared sensor measurements in 2D case, one can use a local linear filter to estimate the target motion parameters, then a state fusion formula based on the Likelihood of the expected overall local measurements is applied to obtain the global estimate. The simulation results show that the proposed approach performance is equivalent to the centralized fusion schema in terms of tracking accuracy but exhibits the advantages of the decentralized fusion schema like parallel processing architecture and robustness against transmission delays. In addition, the low complexity of the obtained algorithm is well suited for real-time applications