A Canonical Genetic Algorithm for Blind Inversion of Linear Channels

It is well known the relationship between source separation and blind deconvolution: If a filtered version of an unknown i.i.d. signal is observed, temporal independence between samples can be used to retrieve the original signal, in the same manner as spatial independence is used for source separation. In this paper we propose the use of a Genetic Algorithm (GA) to blindly invert linear channels. The use of GA is justified in the case of small number of samples, where other gradient-like methods fails because of poor estimation of statistics

Receptor avanzado de comunicaciones para acceso multiusuario asíncrono

The use of digital antenna arrays to increase the efficiency of a communication link is studied. Specifically, a Time Reference Multi-beamformer/conformer system, is proposed. The goal is the simultaneous demodulation of BPSK-users, regardless their co-channel nature (in frequency and time). For this purpose, the proposed system resorts to the statistical independence of the impinging user signals and to the spatial diversity introduced by the array. A robust High Order Statistics Combiner will be developed. Its potential stands out in the presented simulations, which illustrate the good performance of the designed multiuser system both in the acquisition and tracking.Peer ReviewedPostprint (published version

Factorisation d'un spectre d'ordre quatre et application en identification aveugle

Dans cet article, nous énonçons une condition nécessaire et suffisante de factorisabilité d'un spectre d'ordre quatre. Ensuite, nous décrivons deux algorithmes de factorisation d'un spectre d'ordre quatre. Le premier utilise un nombre minimum de données du trispectre pour reconstruire la phase du système tandis que le second utilise toutes les données du trispectre et fournit une solution optimale au sens des moindres carrés. Cette solution est en première approximation équivalente à celle donnée par la méthode de maximisation du kurtosis [3, 1, 7]. Finalement, on utilise à nouveau la relation sur laquelle est basée la condition nécessaire et suffisante afin d'améliorer la qualité de l'estimation des phases du trispectre

New Results on the Evaluation of Equalizers Performance

In this paper, we present a new upper bound on the probability of error in PAM systems. The main feature of this bound is that it depends on the variance and fourth-order cumulant of the measurable equalizer output and on the a-priori known statistics of the channel input. It can therefore be useful for an aposteriori evaluation of the equalization accuracy in a blind equalization context

A Canonical Genetic Algorithm for Blind Inversion of Linear Channels

Abstract. It is well known the relationship between source separation and blind deconvolution: If a filtered version of an unknown i.i.d. signal is observed, temporal independence between samples can be used to retrieve the original signal, in the same manner as spatial independence is used for source separation. In this paper we propose the use of a Genetic Algorithm (GA) to blindly invert linear channels. The use of GA is justified in the case of small number of samples, where other gradient-like methods fails because of poor estimation of statistics

A Fast Algorithm For Sparse Multichannel Blind Deconvolution

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)We have addressed blind deconvolution in a multichannel framework. Recently, a robust solution to this problem based on a Bayesian approach called sparse multichannel blind deconvolution (SMBD) was proposed in the literature with interesting results. However, its computational complexity can be high. We have proposed a fast algorithm based on the minimum entropy deconvolution, which is considerably less expensive. We designed the deconvolution filter to minimize a normalized version of the hybrid l(1)/l(2)-norm loss function. This is in contrast to the SMBD, in which the hybrid l(1)/l(2)-norm function is used as a regularization term to directly determine the deconvolved signal. Results with synthetic data determined that the performance of the obtained deconvolution filter was similar to the one obtained in a supervised framework. Similar results were also obtained in a real marine data set for both techniques.811V7V16CAPESCNPqPetrobrasCoordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Egalisation autodidacte adaptative : Application aux systèmes d'accès multiples à répartition dans le temps

L'égalisation adaptative, autodidacte ou entraînée, nécessite en général un temps de convergence qui s'accomode mal des systèmes d'accès multiples à répartition dans le temps (AMRT), systèmes dans lesquels la transmission s'effectue en mode paquets. Par ailleurs le nombre d'applications utilisant ce type d'accès ne cesse de croître. De ce point de vue, il paraît opportun de réfléchir à des solutions permettant à un égaliseur de converger sur des paquets (ou blocs) courts, comportant quelques dizaines de symboles. Parmi les applications visées on peut citer, de manière non exhaustive, le GSM, le DECT, etc. Dans chacun de ces systèmes, le bloc comporte une séquence connue dont la longueur s'avère généralement insuffisante pour permettre la convergence d'un égaliseur adaptatif entraîné. Au travers de cet article nous allons montrer que l'égaliseur autodidacte adaptatif récemment introduit par Labat et al peut s'accomoder de cette contrainte, avec une complexité raisonnable