Algorithme génétique multi-objectifs adaptatif

International audienceCet article présente une version adaptative d’un algorithme génétique multi-objectif appelé GAME. Ce dernier propose une structuration de la population en plusieurs fronts de Pareto et la définition de diverses fonctions de fitness. La version proposée dans cet article, aGAME, introduit un opérateur d’adaptation dynamique qui alterne les phases d’exploration et d’exploitation au cours de l’exécution de l’algorithme. Ces changements de mode de parcours de l’espace de recherche utilisent des indicateurs de performance afin de maintenir un équilibre entre la "convergence" et la diversité des solutions obtenues. aGAME est comparé à la version de base (GAME) ainsi qu’aux trois meilleurs algorithmes de la compétition CEC 2009, sur des problèmes bi-objectifs avec des contraintes. Cette étude comparative montre que aGAME obtient de meilleurs résultats que les quatre algorithmes auxquels il est comparée. Ces résultats valident l’efficacité de l’opérateur d’adaptation dynamique et les performances globales de l’algorithme

Multi-Pareto-Ranking Evolutionary Algorithm

International audienceThis paper proposes a new multi-objective genetic algorithm, called GAME, to solve constrained optimization problems. GAME uses an elitist archive, but it ranks the population in several Pareto fronts. Then, three types of fitness assignment methods are defined: the fitness of individuals depends on the front they belong to. The crowding distance is also used to preserve diversity. Selection is based on two steps: a Pareto front is first selected, before choosing an individual among the solutions it contains. The probability to choose a given front is computed using three parameters which are tuned using the design of experiments. The influence of the number of Pareto fronts is studied experimentally. Finally GAME's performance is assessed and compared with three other algorithms according to the conditions of the CEC 2009 competition

Designing Smart Adaptive Flooding in MANET using Evolutionary Algorithm

International audienceThis paper deals with broadcasting warning / emergency messages in mobile ad hoc networks. Traditional broadcasting schemes tend to focus on usually high and homogeneous neighborhood densities environments. This paper presents a broadcasting protocol that locally and dynamically adapts its strategy to the neighborhood densities. The behavior of the protocol is tuned using various internal parameters. Multiple combinations of those parameters have been pre-computed as optimal solutions for a range of neighborhood densities, and the most relevant one is dynamically chosen depending on the locally perceived environment. The combinations were determined by coupling an evolutionary algorithm and a network simulator, using a statistically realistic radio-propagation model (Shadowing Pattern). This approach is compared with other probabilistic methods while broadcasting an emergency message in vehicular ad hoc networks with variable and heterogeneous vehicle densities. In such a context, it is expected from the network to enable each node to receive the warning message. The results show that our protocol covers the whole network, whereas other methods only have a probability of 0.57 to 0.9 to cover the entire network

Energetic Performance of Service-oriented Multi-radio Networks: Issues and Perspectives

Wireless devices now hold multiple radio interfaces, allowing to switch from one network to another according to required connectivity and related quality. Still, the selection of the best radio interface for a specific connection is under the responsibility of the end-user in most cases. Integrated multi-radio network management so as to improve the overall performance of the network(s) has led to a number of research efforts over the last few years. However, several challenges remain due to the inherent complexity of the problem. This paper specifically concentrates on the comprehensive analysis of energy-efficient multi-radio networking for pervasive computing. Building upon the service oriented architectural style, we consider pervasive networks of services, which are deployed on the various networked nodes. The issue is then to optimize the energetic performance of the pervasive network through careful selection of the radio link over which service access should be realized for each such access. This leads us to examine first the energetic performance of service access for most common wireless interfaces in use today (Bluetooth, WiFi and GPRS) and then introduce a formal model of service-oriented multi-radio networks. The proposed model enables characterizing the optimal network configuration in terms of energetic performance, which is shown to be a NP-hard problem and thus requires adequate approximation

Transcriptional Mutagenesis Induced by 8-Oxoguanine in Mammalian Cells

Most of the somatic cells of adult metazoans, including mammals, do not undergo continuous cycles of replication. Instead, they are quiescent and devote most of their metabolic activity to gene expression. The mutagenic consequences of exposure to DNA–damaging agents are well documented, but less is known about the impact of DNA lesions on transcription. To investigate this impact, we developed a luciferase-based expression system. This system consists of two types of construct composed of a DNA template containing an 8-oxoguanine, paired either with a thymine or a cytosine, placed at defined positions along the transcribed strand of the reporter gene. Analyses of luciferase gene expression from the two types of construct showed that efficient but error-prone transcriptional bypass of 8-oxoguanine occurred in vivo, and that this lesion was not repaired by the transcription-coupled repair machinery in mammalian cells. The analysis of luciferase activity expressed from 8OG:T-containing constructs indicated that the magnitude of erroneous transcription events involving 8-oxoguanine depended on the sequence contexts surrounding the lesion. Additionally, sequencing of the transcript population expressed from these constructs showed that RNA polymerase II mostly inserted an adenine opposite to 8-oxoguanine. Analysis of luciferase expression from 8OG:C-containing constructs showed that the generated aberrant mRNAs led to the production of mutant proteins with the potential to induce a long-term phenotypical change. These findings reveal that erroneous transcription over DNA lesions may induce phenotypical changes with the potential to alter the fate of non-replicating cells

Mobilité et coopération dans un système réparti de caches vidéo

L'accroissement de la capacité des réseaux d'interconnexion ainsi que la démocratisation des communications électroniques ont provoqué l'émergence de nouveaux types de services tels que la transmission de vidéos à la demande. De plus, l'apparition des réseaux mobiles et le développement des capacités des périphériques nomades ont rendu possible le rendu de ces services sur des clients mobiles. Cependant la diffusion des oeuvres multimédia diffère de celle des données habituelles en posant des problèmes particuliers tels que le volume d'informations à faire transiter, ou encore les contraintes de temps-réel importantes. La mobilité des clients peut quant à elle entraîner des coupures de services en cas de mauvaise gestion. Le projet MoVie vise à concevoir une plate-forme de diffusion de séquences multimédia multi-serveurs pour des clients mobiles, principalement ceux des réseaux de téléphonie mobile de 3e génération. Ces travaux décrivent SysMoVie, couche intermédiaire venant s'insérer de manière transparente entre des serveurs vidéo déjà existants et des clients mobiles. Nous avons pris le parti de ne modifier ni les périphériques clients, ni les serveurs. La thèse que nous défendons est que le déploiement d'un ensemble de caches distribués coopératifs permet d'assurer l'extensibilité du système, d'optimiser la qualité du service offert aux utilisateurs et de supprimer les coupures des diffusions dues à la mobilité.BELFORT-BU L. FEBVRE (900102102) / SudocSudocFranceF

Energy-efficient Middleware-layer Multi-radio Networking: An Assessment in the Area of Service Discovery Abstract

The massive deployment of mobile networks together with the emergence of powerful portable devices has given rise to pervasive computing environments. In such environments, mobile users may discover and access services offered in surrounding networks using Service Discovery Protocols (SDPs). However, several SDPs are currently in use, each one designed for a specific target network architecture and setting. As a result, in today’s multi-radio networking environment, SDPs do not equally suit each radio interface. In order to provide effective service discovery in multi-radio networks, the most resource-efficient radio interface should be chosen with respect to two main criteria: the adequacy of the interface against the SDP to be used, and energy saving, which is crucial for battery-powered devices. Toward this goal, this article assesses how to effectively take advantage of the multiple radio interfaces now embedded within wireless devices with respect to energy consumption, from the standpoint of service discovery and access. It further investigates the adequacy of legacy SDPs with the various networks, so as to classify the most appropriate networks for each SDP. Exploitation of these results is finally investigated with the description of an energy-efficient algorithm for SDP-based context sensing in a multi-radio pervasive environment

Service Discovery in Multi-radio Networks: An Assessment of Existing Protocols

The wide deployment of mobile networks and the emergence of powerful portable devices has given core to pervasive computing. As particularly addressed by Beyond 3G (B3G) networks, the recent evolution of mobile networks introduces the convergence of wireless technologies, where several radio interfaces are to be used concurrently. Thus, B3G-aware applications shall make the most effective use of this connectivity. In pervasive environments, mobile users may discover and access services offered on the networks using Service Discovery Protocols (SDPs). Several SDPs are currently in use, each one designed for specific target network architecture and setting. Thus, in a multi-radio environment, each SDP does not equally suit each radio interface. In order to provide effective service discovery in multi-radio networks, the most resource efficient interface shall be chosen with respect to two main criteria: the adequacy of the radio interface against the SDP to be used, and energy saving, which is crucial for battery-powered devices. Toward this goal, this paper assesses how to exploit multiple radio interfaces from the standpoint of service discovery and access with respect to energy consumption, and the adequacy of the legacy SDPs with the various networks, so as to classify the most appropriate networks for each SDP