Investigation de la gestion de qualité de service dans le réseau UMTS

Bit rate announced for the future standards of telecommunication, as well as the level of integration reached are, as many factors, determining for the establishment of new applications in mobile terminals. Nowadays, mobile video streaming services are possible. Mobile users expect to receive multimedia traffic with some performance guarantees, so we must ensure the necessary quality of service during the video transmission. This paper aims at investigating quality of service issue inUmts network. More specifically, we explore the main challenge of quality of service management to dynamically optimize the distribution of load inUmts networks. Our investigation is organized in the following way. We formalize the optimization problem which is based on the graph theory and modellingUmts network as well as mobile users and applications to be used. The simulation of our optimization model show a clear improvement of the quality of service perceived by anUmts user in terms of bit rate, blocking and connection drop.     

Utilisation de la corrélation pondérée dans un processus de détection d’intrusions

Generally, an intruder must perform several actions, organized in an intrusion scenario, to achieve his or her malicious objectives. Actions are modeled by their pre and post conditions, which are a set of logical predicates or negations of predicates. Pre conditions of an action correspond to conditions the system’s state must satisfy to perform the action. Post conditions correspond to the effects of executing the action on the system’s state. When an intruder begins his intrusion, we can deduce, from the alerts generated byidss (Intrusion Detection Systems), several possible scenarios, by correlating attacks, that lead to multiple intrusion objectives. However, with no further analysis, we are not able to decide which are the most plausible ones among the possible scenarios. We propose in this paper to define an order over the possible scenarios by weighting the correlation relations between successive attacks composing the scenarios. These weights reflect to what level executing some actions are necessary to execute some action B. We will see that to be satisfactory, the comparison operator between two scenarios must satisfy some properties.     

Minimisation de la consommation d’Énergie dans les réseaux ad hoc

An ad hoc network is a collection of wireless devices forming a temporary network independently of any administration or fixed infrastructure. The main benefits of this new generation of mobile networks are flexibility and their low cost. Wireless devices have maximum utility when they can be used “anywhere at anytime “. However, one of the greatest limitations to that goal is the finite power supplies. Since batteries provide limited power, a general constraint of wireless communication is the short continuous operation time of mobile terminals. This constraint is more important for the ad hoc networks, since every terminal has to perform the functions of a router. Therefore, energy consumption should be a crucial issue while designing new communication protocols and particularly ad hoc routing protocols. We propose, in this paper, some extensions to the most important on-demand routing algorithm,Aodv (Ad hoc On demand Distance Vector). The discovery mechanism in these extensions uses energy as a routing metric. These algorithms improve the network survivability by maintaining the network connectivity, which is the strong requirement for a high-quality communication. They carry out this objective with low message overhead for computing routes and without affecting the other network protocol layers.     

Utilisation d’un analyseur syntaxique pour la reconnaissance de la parole continue

The author describes the syntactic analyzer which is used in the system keal for continuous speech recognition. After detection of the words in an utterance by a lexical analyzer, the syntactic analyzer builds all the possible syntactic structures according to a context free grammar previously defined by means of a compiled metalanguage. This analyzer allows, in some cases, to correct some errors such as omission and insertion of phonemes by the phonemic analyzer, or non-detection of short words by the lexical analyzer. This program enables presently the recognition of 65 % of utterances in simple dialogs. A few seconds are enough to recognize a sentence.     

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.     

Détermination des directions de normale d’onde de signaux variant dans le temps. Application aux émissions naturelles TBF détectées à bord de satellites

A method for studying the polarization of an electromagnetic plane wave, the characteristics of which vary rapidly in time, is described. This method is based upon the concept of the (instantaneous) complex representation of a polarized signal. It is possible in particular to yield the wave normal direction as a function of both time and frequency. The accuracy of the method is studied, as a function of both the signal-to-noise ratio and of the eccentricity of the polarization ellipse. This method is applied to the determination of wave normal directions of natural Vlf signals propagating in the whistler mode within the magneto sphere. Important variations in the propagation characteristics of the signals are evidenced.     

Modélisation d’un anneauSDH pour les besoins de la gestion de fautes

When an anomaly occurs in aSDH network, many notifications are emitted towards the supervision center. The emission of these notifications is the result of the signals treatment on the level of the objects describing the network. This document describes the modeling process of the behavior and the interaction between the objects intervening in the data processing of faults management. It gives a methodology ofSDH network model construction for the needs for faults situations diagnosis.