{WiFi GPS} based Combined positioning Algorithm

International audienceIf nowadays, positioning becomes more and more accurate, and covers better and better a territory (indoor and outdoor), it remains territories where traditional (and basic) positioning system (GPS, gsm or WiFi) and hybrid ones (GPS-gsm, GPS-WiFi, GPS-WiFi-gsm,...) are insufficient and requires research investment treating combined positioning. In this paper we propose a GPS-WiFi combined positioning algorithm, based on trilateration technique. Real experiments and other simulation are conduced and demonstrate accuracy gains, even where various criteria dilution of precision (GPS dop s criteria, or ours WiFi geometrical and signal attenuation s dop proposal, or hybrid dop one s) indicate all the disruption of positioning service. A testbed scenario issued from a real urban campus environment validates not only our GPS-WiFi combined positioning algorithm but also an implementation of pertinent positioning techniques and dop s criteria. This work constitutes ?a further ?step to better position everywhere and to ensure continuity of a positioning service

Removing the MAC Retransmission Times from the RTT in TCP

MAC retransmission of packets (for example in a video transfer) raises the RTT and leads to throughput decrease on TCP versions based on RTT for their sending rate. This is not the appropriate effect, because retransmissions are caused by temporary interferences, which often appear in wireless links. This paper deals with the effects of MAC retransmissions. A new TCP option is proposed, which fully takes into account the effect of MAC retransmissions. In this proposition wireless network cards have a timer which is initialised with the value of the option once the packet is sent the first time, and this value is stored in the option each time the packet is retransmitted. The exact time of retransmissions is then known by the source. Simulations show that the proposed mechanism increases throughput

Distance-Dependent RED Policy (DDRED)

International audienceThe network quality of service (QoS) and the congestion control of the transport protocol are important parameters for the performance of a network data transfer. To this end, routers use various queue policies for packet dispatching, and all of them must deal with packet drop. We propose a new algorithm for packet drop in routers. Given that a packet drop wastes all the network resources it has already used, we propose a new policy which favors packets with higher distance from source. It can be simply integrated on top of tail drop or RED (with or without ECN) queue policies. Simulations with NS2 show that long flows are indeed favored compared to short flows, and lead to higher overall resource utilisation without sacrificing TCP fairness

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

Étude de l'interception et du positionnement de trafic {Wi-Fi} dans un environnement hétérogène

International audienceDans le cadre d'une politique de sécurité dans les réseaux sans fils, il est intéressant de pouvoir identifier la position géographique d'une source de données, pour s'assurer de sa légitimé et de son utilisation du réseau. Dans cette optique, nous proposons ici un aperçu des possibilités de capture de trafic mises en relation avec un système de géolocalisation centralisé. Notre axe d'étude porte en particulier sur le matériel courant, librement accessible au plus grand nombre et à un faible coût

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

Video quality estimation of {DCCP} streaming over wireless networks

International audienceThis paper describes a streaming architecture simulation model above Network Simulator 2 (NS2) which allows to define specific transport properties. Multimedia contents are specific because they are time-dependent and they can undergo small deterioration if necessary. We simulate such a congestion control that has the ability to decrease the multimedia quality in case of network congestion in order to decrease packet losses and packet delivery delays. We integrate this video congestion control inside DCCP (Datagram Congestion Control Protocol) and TFRC (TCP Friendly Rate Control). The transcoding of the multimedia contents is realized thanks to the NetMoVie simulation model which is an RTP mixer. We compare the adaptive transport solution to the classic transport solution without any adaptive mechanism. The Peak Signal-to-Noise Ratio (PSNR) of the received multimedia contents is measured and compared for better visualization

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

DNA mechanics as a tool to probe helicase and translocase activity

Helicases and translocases are proteins that use the energy derived from ATP hydrolysis to move along or pump nucleic acid substrates. Single molecule manipulation has proved to be a powerful tool to investigate the mechanochemistry of these motors. Here we first describe the basic mechanical properties of DNA unraveled by single molecule manipulation techniques. Then we demonstrate how the knowledge of these properties has been used to design single molecule assays to address the enzymatic mechanisms of different translocases. We report on four single molecule manipulation systems addressing the mechanism of different helicases using specifically designed DNA substrates: UvrD enzyme activity detection on a stretched nicked DNA molecule, HCV NS3 helicase unwinding of a RNA hairpin under tension, the observation of RecBCD helicase/nuclease forward and backward motion, and T7 gp4 helicase mediated opening of a synthetic DNA replication fork. We then discuss experiments on two dsDNA translocases: the RuvAB motor studied on its natural substrate, the Holliday junction, and the chromosome-segregation motor FtsK, showing its unusual coupling to DNA supercoiling

Broken replication forks trigger heritable DNA breaks in the terminus of a circular chromosome

<p><u>(A) Circular map of the <i>E</i>. <i>coli</i> chromosome</u>: <i>oriC</i>, <i>dif</i> and <i>terD</i> to <i>terB</i> sites are indicated. Numbers refer to the chromosome coordinates (in kb) of MG1655. (<u>B) Linear map of the terminus region:</u> chromosome coordinates are shown increasing from left to right, as in the marker frequency panels (see Figure 1C for example), therefore in the opposite direction to the circular map. In addition to <i>dif</i> and <i>ter</i> sites, the positions of the <i>parS</i>_pMT1 sites used for microscopy experiments are indicated. (<u>C) MFA analysis of terminus DNA loss in the <i>recB</i> mutant</u>: sequence read frequencies of exponential phase cells normalized to the total number of reads were calculated for each strain. Ratios of normalized reads in isogenic wild-type and <i>recB</i> mutant are plotted against chromosomal coordinates (in kb). The profile ratio of the terminus region is enlarged and the profile of the corresponding entire chromosomes is shown in inset. Original normalized profiles used to calculate ratios are shown in <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1007256#pgen.1007256.s005" target="_blank">S1 Fig</a>. The position of <i>dif</i> is indicated by a red arrow. The <i>ter</i> sites that arrest clockwise forks (<i>terC</i>, <i>terB</i>, green arrow) and counter-clockwise forks (<i>terA</i>, <i>terD</i>, blue arrow) are shown. <u>(D) Schematic representation of focus loss in the <i>recB</i> mutant:</u> Time-lapse microscopy experiments showed that loss of a focus in the <i>recB</i> mutant occurs concomitantly with cell division in one of two daughter cells, and that the cell that keeps the focus then generates a focus-less cell at each generation. The percentage of initial events was calculated as the percentage of cell divisions that generate a focus-less cell, not counting the following generations. In this schematic representation, two initial events occurred (generations #2 and #7) out of 9 generations, and focus loss at generation #2 is heritable. Panels shown in this figure were previously published in [<a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1007256#pgen.1007256.ref019" target="_blank">19</a>] and are reproduced here to introduce the phenomenon.</p