Retour d’expérience sur différentes applications de réseau actif

Active network technologies, started by D. Tennenhouse’s work atmit in 1995 have led a lot of promises on the evolution of data networks. Active networks aim at integrating new application-level functionalities into active nodes within the network, in a flexible and extensible way. The research works on active networks have raised at the same time as the definition of new open network architectures (e.g., Tina model) and the deployment of intelligent networks merging telecom networks with distributed systems fields. This concept of “programmable networks” led to many technology-oriented projects, but has not identified relevant applications highlighting the benefits of the technology. During the three last years, our laboratory has tackled this gap and prototyped some use cases of open programmable networks. The paper gives an overview of each of these use cases and focuses on the integration with existing network elements both at transfer and management planes. Then it presents some assessments and perspectives. We show that programmable networks are optimizing globally resources to be deployed although they impose an overhead at node level, thanks to efficient integration choices. We present two scenarios of deployment of current programmable network platforms within the same network configuration than a realwan network.     

Potentialités des séquences d’étalement chaotiques pour l’amélioration duTEEB d’un systèmeDS-CDMA asynchrone

The use of chaotic sequences as spectral spreading sequences in a Direct Sequence-Code Division Multiple Access is proposed in this paper. The simulation of the system is performed with the system simulator Omnisys. The chaotic spreading sequences are generated from a non-linear recursive equation. The Bit Error Rate of this system is compared with theBER of the same system using binary Gold sequences. The results show that chaotic sequences can improve performances in terms of allowable number of users.     

Modélisation des discontinuités d’un objectif radar par des points brillants

In order to study the scattering of a monochromatic electromagnetic wave by a complex radar target, specialists usually modelize the target by a discrete scatterers model. The majority of the scatterers are represented by specular points of reflexion on the surface of the target, but the radar cross section (rcs) is also a function of surface discontinuities. In this article, we develop a method which allows us to replace the discontinuities by groups of point contributors of which the positions and thercs are given. Eventhough thercs are generally functions which decrease as the frequency increases, which can at times be neglected, it can be shown there exists quite frequentlyrcs which are independent of the wavelength. General formulae are given. It is emphasized that the physical optic integral may be used to calculatercs eventhough the conditions of application are not correct. For this reason a number of coefficients including the polarisations are used. The formulae of these coefficients are given. As a result an evaluation of thercs may be simplified, and the same method may be used to study the specular regions and the surface discontinuities.     

Reconnaissance des défauts et traitement d’images pour les composés III–V

This paper resumes the most recent results in the field of defect detection and analysis in III–V compounds by image analysis. The correlation of the defects with the specifications of the integrated circuits is especially emphasized. The production of integrated circuits or optoelectronic integrated circuits from III–V compounds is intended to bring large improvements in speed, power and radiation or thermal hardness. Such a development requires a precise control of the material quality and we will consider the relation between microscopic imperfections and device specifications through imaging techniques. This paper contents five chapters respectively devoted to: crystal growing and dislocation imaging; possible role of the deep centerEl2 in GaAs; correlation of defects withFet specifications; infrared transmission and scattering imaging; numerical processing and instruments. Computer assisted processing of image now gives a large aptitude for image transformation synthesis and recording; it allows also to conceive numerical processing and instruments. Computer assisted processing of images gives a large aptitude for image transformation, synthesis and recording; it allows to conceive a diagnostic of the quality of the wafer with respect to the structure that is be elaborated on.     

À propos de la conception de systèmes d’aide aux déplacements des déficients visuels

This paper aims to contribute to studies related to visual handicap in order to reduce/eliminate it with new technologies. It addresses shortly the main principle of 3D world human perception, the main rules for environmental pertinent data acquisition and their processing. The proposed state of art on blind people travel assisting aids (taa) allow to understand the requirements for new aids design. A few examples of research project show how solution from new information technologies (such as artificial vision, virtual reality, high densityvlsi, tactile systems, GPS, wireless networks, etc) can be integrated in new systems. These examples allow also to determine which concepts should be targeted when designing any new travel assistance for blind people autonomous and safe displacement, and to characterise new devices.     

Diffraction d’ondes électromagnétiques impulsionnelles par des obstacles métalliques

Transient scattering problem by perfectly conducting bodies is treated, directly in time domain, using the distribution theory. New integral equations for solving two dimensional scattering problems are established. Applications to metallic structures responses to electro-magnetic pulses (Emp)illumination are presented.