Etude de performance d’un système de communication ECMA-368 dans un canal réaliste Ultra Large Bande

L’ECMA-368 est une norme récente, qui décrit la couche physique ULB (PHY-UWB) pour un réseau personnel sans fil (WPAN). Dans cet article, nous allons concevoir et évaluer les performances en termes de taux d'erreur binaire (TEB) d’un système de communication qui respecte la norme ECMA-368 en utilisant les différents modèles de canal ULB définis par la norme IEEE802.15.3a et avec l’ensemble des débits binaires

Reduction of power envelope fluctuations in OFDM signals by using neural networks

One of the main drawbacks of Orthogonal Frequency Division Multiplexing (OFDM) are the large fluctuations of its power envelope. In this letter, a novel and efficient scheme based on Multilayer Perceptron (MLP) Neural Networks (NN) is proposed. The NN synthesizes the Active Constellation Expansion - (ACE) technique which is able to drastically reduce envelope fluctuations. This is achieved with much lower complexity, faster convergence, and better performance compared to previously available methods.This work has been partly funded by the projects MULTI-ADAPTIVE (TEC2008-06327-C03-02), COMONSENS (CSD2008-00010), and the AECI Program of Research Cooperation with Morocco.Publicad

Reduction of the envelope fluctuations of multi-carrier modulations using adaptive neural fuzzy inference systems

In this paper, a novel scheme for reducing the envelope fluctuations in multi-carrier signals applying Adaptive Neural Fuzzy Inference Systems (ANFIS) is proposed and analyzed. Once trained with signals with very low envelope fluctuations, such as those obtained by the Active Constellation Expansion - Approximate Gradient Project (ACE-AGP) algorithm, ANFIS approximately reaches a similar reduction as with ACE-AGP for multi-carrier signals without the complexity and the large convergence time of conventional ACE-AGP. We show that our approach is less complex than other previous schemes and with better performanceThis work has been partly funded by projects MULTI-ADAPTIVE (TEC2008-06327-C03-02), COMONSENS (CSD2008-00010) and AECI Program of Research Cooperation with Morocco (A/027714/09)Publicad

High power amplifier pre-distorter based on neural-fuzzy systems for OFDM signals

In this paper, a novel High Power Amplifier (HPA) pre-distorter based on Adaptive Networks - Fuzzy Inference Systems (ANFIS) for Orthogonal Frequency Division Multiplexing (OFDM) signals is proposed and analyzed. Models of Traveling Wave Tube Amplifiers (TWTA) and Solid State Power Amplifiers (SSPA), both memoryless and with memory, have been used for evaluation of the proposed technique. After training, the ANFIS linearizes the HPA response and thus, the obtained signal is extremely similar to the original. An average Error Vector Magnitude (EVM) of 10-6 can be easily obtained with our proposal. As a consequence, the Bit Error Rate (BER) degradation is negligible showing a better performance than what can be achieved with other methods available in the literature. Moreover, the complexity of the proposed scheme is reducedThis work was supported in part by projectsMULTIADAPTIVE (TEC2008-06327-C03-02) and AECI Program of Research Cooperation with MoroccoPublicad

Implementation of an Affordable Method for MPS Diagnosis from Urine Screening to Enzymatic Confirmation: Results of a Pilot Study in Morocco

Background: Rapid and accurate diagnosis of mucopolysaccharidoses (MPS) is still a challenge due to poor access to screening and diagnostic methods and to their extensive clinical heterogeneity. The aim of this work is to perform laboratory biochemical testing for confirming the diagnosis of mucopolysaccharidosis (MPS) for the first time in Morocco. Methods: Over a period of twelve months, 88 patients suspected of having Mucopolysaccharidosis (MPS) were referred to our laboratory. Quantitative and qualitative urine glycosaminoglycan (GAG) analyses were performed, and enzyme activity was assayed on dried blood spots (DBS) using fluorogenic substrates. Enzyme activity was measured as normal, low, or undetectable. Results: Of the 88 patients studied, 26 were confirmed to have MPS; 19 MPS I (Hurler syndrome; OMIM #607014/Hurler-Scheie syndrome; OMIM #607015), 2 MPS II (Hunter syndrome; OMIM #309900), 2 MPS IIIA (Sanfilippo syndrome; OMIM #252900), 1 MPS IIIB (Sanfilippo syndrome; OMIM #252920) and 2 MPS VI (Maroteaux-Lamy syndrome; OMIM #253200). Parental consanguinity was present in 80.76% of cases. Qualitative urinary glycosaminoglycan (uGAGs) assays showed abnormal profiles in 31 cases, and further quantitative urinary GAG evaluation and Thin Layer Chromatography (TLC) provided important additional information about the likely MPS diagnosis. The final diagnosis was confirmed by specific enzyme activity analysis in the DBS samples. Conclusions: The present study shows that the adoption of combined urinary substrate analysis and enzyme assays using dried blood spots can facilitate such diagnosis, offer an important tool for an appropriate supporting care, and a specific therapy, when available

Protection des données visuelles (analyse des fonctions de hachage perceptuel)

Avec une croissance considérable dans le domaine de la technologie multimédia et de la forte disponibilité des logiciels de traitement d'image, il est désormais facile de manipuler les images numériques. En même temps, il est devenu possible de réaliser des contrefaçons très élaborées, en laissant très peu de traces. Cela présente un grave problème, en particulier, si l'authenticité de l'image numérique est exigée. L'authentification des images devrait se baser sur leurs contenus visuels et non pas sur leurs contenus binaires. Par conséquent, pour authentifier une image, il faut tolérer quelques manipulations acceptables que pourrait subir une image telles que la compression JPEG et l'ajout de bruit Gaussien. En effet, ces manipulations préservent l'aspect visuel de l'image. En même temps un système de hachage perceptuel doit être suffisamment fragile pour détecter les manipulations malveillantes qui modifient l'interprétation du contenu sémantique de l'image comme l'ajout de nouveaux objets, la suppression ou la modification majeure d'objets existants.Dans cette thèse, nous nous intéressons aux fonctions de hachage perceptuel pour l'authentification et le contrôle d'intégrité des images numériques. Dans ce but, nous présentons tous les aspects relatifs aux fonctions de hachage perceptuel. Puis, nous exposons les contraintes qu'un système de hachage perceptuel doit satisfaire pour répondre aux exigences souhaitées au niveau de la robustesse des signatures perceptuelles. Enfin, nous présentons une méthode permettant d'améliorer la robustesse et la sécurité d'un système dehachage perceptuel.The widespread use of multimedia technology has made it relatively easy to manipulate and tamper visual data. In particular, digital image processing and image manipulation tools offer facilities to intentionally alter image content without leaving perceptual traces. This presents a serious problem, particularly if the authenticity of the digital image is required. The image authentication should be based on their visual content and not on their binary content. Therefore, to authenticate an image, some acceptable manipulations that could undergoes an image, such as JPEG compression and Gaussian noise addition, must tolerated. Indeed, these manipulations preserve the visual appearance of the image. At the same time a perceptual hashing system should be sufficiently sensitive to detect malicious manipulations that modify the interpretation of the semantic content of the imagesuch as adding new objects, deleting or major modification of existing objects.In this thesis, we focus on perceptual hash functions for authentication and integrityverification of digital images. For this purpose, we present all aspects of perceptual hashfunctions. Then, we discuss the constraints that perceptual hashing system must satisfy tomeet desired level of robustness of perceptual signatures. Finally, we present a method toimprove the robustness and security of a system of perceptual hashing.MONTPELLIER-BU Sciences (341722106) / SudocSudocFranceF

A proposed method for determination of weighted despreading sequences for a DS/CDMA system

The steeping chip weighting waveforms are used in multiple access interference cancellation by emphasizing the received spreading signal, therefore, that allows to solve the problem of orthogonality for the chip waveforms. Our paper presents a useful method based on fuzzy systems to determine the despreading sequences weighted by the steeping chip weighting waveforms for Direct Sequence Code Division Multiple Access DS/CDMA. The validity of our proposed method has been tested by numerical examples for an Additive White Gaussian Noise channels and shows that the parameter values of the chip weighting waveforms are good and the Bit Error Rate performance of the system does not undergone any degradation