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.     

Architectures de systèmes monopuces en radio fréquence: solutions pour une faible consommation

This paper is a discussion on 2.45 GHzrf SoC for low cost applications. Starting from cost considerations, design of analogue, digital and mixed parts is discussed. In this context, some topologies and some technological choices are proposed. The possible use of the presented solutions in the 802.15.4 standard is also analysed. Thus, using a comparative analysis, this paper shows the interest of a Zero-if direct conversion associated withfsk modulation. The communication protocol impact on the design is also discussed. Many topology drawbacks are also highlighted for Low-costrf SoC.     

Un environnement de conception de systèmes distribués basé sur UML

This paper introduces a new environment for developing distributed systems. It is based on theTurtle uml profile. Analysis and design phases, described in previous papers, have been extended with an additional deployment phase. In this new step,Turtle components are deployed over hardware execution nodes, and nodes are connected together throughout links,Turtle deployment diagrams are given a formal semantics inRt-lotos, therefore following the approach used forTurtle analysis and design diagrams. Moreover, the paper presents a Java code generator which outputs appropriate Java code forTurtle deployment diagrams. This code is automatically deployable on networks because it implements node communication using network protocols such asUdp orRmi. ttool, the turtle toolkit has been extended to support these new diagrams and code generators. The attack of protected data exchanged throughout securedHttp sessions serves as example.     

Amélioration des performances des systèmes à haut débit par une méthode de réduction de la diaphonie dans les câbles multiconducteurs de télécommunications

dsl (Digital Subscriber Line) technology provides low cost access to the consumers and sources of information for any one subscribing to classical analogical telephony. Indeed xdsl services enable high-speed digital transmission on conventional telephone lines. For sixteen years that the internet has risen, a great number of offers proposing increasing bit rate have been developed. Considering this increasing demand of high bit rate access, telecommunication operators perpetually work on finding solutions to optimize the copper lines channel. In that way, we present here a new method of crosstalk reduction in a multiconductor telecommunication cable. Interests and limitations of this method are presented and some simulations on a frequency band extending to 30 MHz will picture those theoretical results.     

Conception des systèmes de protection des réseaux d’énergie à basse tension contre les impulsions électromagnétiques à haute altitude et la foudre

An exoatmospheric nuclear burst creates, by interactions photonsmatters, an electromagnetic field (electromagnetic pulse- Emp ). Its coupling with links,particularly overhead power ac supply lines of ground stations, induced a parasitic electrical pulse fast and intense, susceptible to perturb, damage or destroy down stream electrical or electronic equipments. Otherwise, the lightning can also generates, on the same links, electrical pulses with some différents characteristics. After a quick recall of the problem and specifications, the design methodology of protective devices against this pulse created by nemp and lightning, for ac power lines, is given. This method implement computed aided design (cad)and specific experimental ways. The protection efficiency is evaluated and validated, exemples of achievements described.     

Comparaison de la fiabilité opérationnelle des modules optiques équipant les systémes à 34 Mbit/s de France télécom

The purpose of the joint research programme conducted by the CNET and Alcatel CIT on various France Telecom 34 Mbit/s multimode optical links (0.85 and 1.3 μm) is to assess their behaviour versus time, compare their operational reliability and the different types of optoelectronic components used. Traceability on the entire product life cycle was performed using a micro-computer data base. Data was recorded from the begin-ning (January 1985) until the end of the first quarter of 1990. Analysis of the results obtained has taken into account the influence of storage and the failure analyses carried out on rejected components. The results obtained on 0.85 μm optical transmit modules have been used to elaborate a modelling procedure for reliability predictions.     

Démarche de conception d’une plate-forme monopuce de réception de radiodiffusion numérique DRM

The newdrm standard for digital radio broadcast in theam band requires integrated devices for radio receivers at low cost and very low power. A chipset has been developed based on anarm9 dual-core architecture. This paper introduces the application itself, and then presents the development process followed to design such a chip covering the hardware/software partitioning, the architecture definition and all the validation issues. Therf part that partially drives the baseband is also briefly presented. The legal aspects are also investigated. Then as a conclusion, this paper presents the next steps of this development and the methodological gap in the system on chip design process.     

Théorie asymptotique de la diffraction en optique physique appliquée aux antennes à réflecteur

In physical optics approximation, the high frequency asymptotic analysis is used to obtain the scattered field from a given reflector. The results for a circular flat reflector are compared with numerical exact solution. The derived physical optics diffraction coefficientsare found to be numerically in good agreement with those of the geometrical theory of diffraction (GID).Transition functions are introduced in those coefficients to remove the singularities at stradow and reflection boundaries. This asymptotic analysis is generalized for reflectors of arbitrary shape. The derived formal expression of diffraction dyadic is shown to be similar to the one of GTD only for axially symmetric reflectors. In this case, the diffracted field has a simple practical formula. Results for a paraboloid reflector fed by a short dipole are compared to physical optics solution.     

Le système cellulaire de télécommunication avec les mobiles

Cept has undertaken to standardize a new land mobile cellular system in the 900 MHz band, which will enable the compatibility of services throughout Europe. The specifications of this second generation cellular system are under study by the special group « Systèmes mobiles publics de radiocommunication » (gsm). This paper intends to give a general overview of this system, based on the work going on withingsm. It concentrates mainly on the services aspects, and the system architecture, interfaces and protocols. In order to illustrate the global working of the system, the example of a mobile terminated call establishment is given.