Interworking QOS Management Subsystem into IMS-Based Architecture Multi Providers: IMS-IQMSMP

International audienceThe third-generation partnership project 3GPP and 3GPP2 have standardized the IP multimedia subsystem (IMS) to provide ubiquitous and access network-independent IP-based services for next-generation networks via merging cellular networks and the Internet. The IP Multimedia Subsystem (IMS) seems to be the technology that will prevail in Next Generation Networks (NGNs). The users wish to communicate through collections of networks using different protocols; rendering service mapping from one network to another with the similar QoS is a complex issue thereby. The heterogeneous networks are collections of communication platforms using different protocols. This heterogeneity implies the need to offer many different services on the market within short time. In this paper we propose a heterogeneous network model based on the IMS that provides guaranteed QoS. Our method presents, in the first, an informational solution. Decisional information is added to the HSS basis to enrich the knowledge base, which is expressed under the form of "profile of QoS R", where the new information informs directly the decisions to be taken according to the user’s profile (preferences QoS and pricing, bandwidth, location ...). In the second, a solution for multi provider’s context which can allow a subscriber to register with one or more operator(s) according to QoS offered. Thirdly, a mechanism which can be deployed in heterogeneous networks to preserve the original QoS values of the user session and thus eliminate the cumulative effect of QoS rounding across the entire communication path. And it is feasible via the “Interworking QoS Management Sub-network” while adding the new interworking management components, namely: SICs, DIC, QPA AS and HSS-PQoSr

Delay-based strategy for safety message dissemination in Vehicular Ad hoc NETworks: Slotted or continuous?

International audience—The diversity of applications' types in Vehicular Ad hoc NETworks (VANETs) has spawned a large variety of messages that need to be efficiently disseminated between connected vehicles. The most critical messages are those dedicated for safety applications such as road hazardous warning, signal violation warning, etc. The dissemination of this sort of messages is considered as a challenging task in mobile networks where the topology changes dynamically. Indeed, transmitted messages should achieve a high data reachability within a limited transmission delay and an acceptable overhead in a Vehicle to Vehicle (V2V) communication mode. In this work, we focus on a special type of data dissemination protocols based on the delay strategy. The purpose of this paper is to compare two basic distinguished techniques, namely the slotted technique and the continuous technique, and study in depth their impact on the data dissemination performance. A proper selection of the convenient technique according to the application's requirements is consequently deduced. For a faithful and rigorous study, simulations are performed by means of ns-3 simulator under a realistic VANET environment in terms of map layout, mobility pattern and radio model. Simulation results show that contrary to the theoretical reflection, slotted technique is approved as the most appropriate one for safety message dissemination. This technique achieves the same packet data ratio and redundancy ratio, compared to the continuous one, while reducing the data transmission delay

A Redundancy based Protocol for Safety Message Dissemination in Vehicular Ad Hoc Networks

International audienceThe diversity of applications types in vehicular ad hoc networks (VANETs) has spawned a large variety of messages that need to be disseminated in vehicle to vehicle (V2V) communication mode. The most critical messages are those dedicated for safety applications such as accident warning, road hazardous warning, signal violation warning, etc. The dissemination of this sort of messages is a challenging task in VANETs since they should be efficiently transmitted i.e. by achieving high packet delivery within a certain time limit and an acceptable overhead. In this work, we propose a robust and an original data dissemination protocol called Redundancy-based Protocol (RBP). Contrary to most of the density based protocols, the protocol is beaconless. It takes into account the surrounding vehicle density during the broadcasting process through a specific metric, named “packet redundancy ratio”, calculated locally at each vehicle. Based on this metric, each vehicle is able to dynamically determine the probability of rebroadcast in order to mitigate the broadcast storm problem. The simulation results prove that the proposed protocol outperforms the slotted 1- persistence scheme in terms of packet drop ratio, and network load while still maintaining a low End-to-End delay and high packet reachability. This scheme is suitable for safety applications, as well as for further kinds of application by saving the network capacity consumption

SEAD: A simple and efficient adaptive data dissemination protocol in vehicular ad-hoc networks

International audienceVehicular ad-hoc network (VANET) is becoming a promising technology for improving the efficiency and the safety of intelligent transportation systems by deploying a wide variety of applications. Smart vehicles are expected to continuously exchange a huge amount of data either through safety or non-safety messages dedicated for road safety or infotainment and passenger comfort applications, respectively. One of the main challenges posed by the study of VANET is the data dissemination design by which messages have to be efficiently disseminated in a high vehicular speed, intermittent connectivity, and highly dynamic topology. In particular, broadcast mechanism should guarantee fast and reliable data delivery within a limited wireless bandwidth in order to fit the real time applications’ requirements. In this work, we propose a simple and efficient adaptive data dissemination protocol called “SEAD”. On the one hand, the originality of this work lies in its simplicity and efficiency regardless the application’s type. Simplicity is achieved through a beaconless strategy adopted to take into account the surrounding vehicles’ density. Thanks to a metric locally measured, each vehicle is able to dynamically define an appropriate probability of rebroadcast to mitigate the broadcast storm problem. Efficiency is manifested by reducing excessive retransmitted messages and hence promoting the network capacity and the transmission delay. The simulation results show that the proposed protocol offers very low packet drop ratio and network load while still maintaining a low end-to-end delay and a high packet delivery. On the other hand, SEAD protocol presents a robust data dissemination mechanism which is suitable either for safety applications or for other kinds of application. This mechanism is able to adapt the protocol performance in terms of packet delivery ratio to the application’s requirements

Exploitation des antennes multiples pour l'optimisation dans les réseaux sans fil

Les récentes avancées dans le domaine du traitement d'antennes et dans la microélectronique ont fait naître la technologie des antennes intelligentes connue sous le nom de "smart antennas". Considérée comme rupture technologique pour les réseaux sans fil, les systèmes d'antennes intelligentes pourraient répondre aux exigences de plus en plus fortes des applications et services en termes de débit, de capacité et de connectivité. Aujourd'hui, les smart antennas sont exploitées pour développer plusieurs technologies incluant les systèmes de commutation de faisceaux, les antennes adaptatives et les systèmes MIMO (Multiple Input Multiple Output). L'utilisation des antennes MIMO a été reconnue comme une technologie-clé, capable d'accroître considérablement la capacité des réseaux sans fil en exploitant différemment et mieux le spectre radio. Elle fait partie des récents et futurs standards tels que le 3GPP-LTE et le IEEE-802.11n. Dans cette thèse, nous nous sommes intéressés à l'exploitation des techniques multi-antennes dans le contexte des réseaux mobiles. Nous nous sommes focalisés principalement sur deux axes de recherche : la formation de faisceaux et le multiplexage spatial. Dans une première étude, nous avons proposé un schéma de formation de faisceaux, basé sur la technique LCMV (Linearly Constrained Minimum Variance) et permettant de former des faisceaux plus adaptés en cas de mobilité. Dans cette solution, l'incertitude sur la localisation des nœuds est compensée par des faisceaux de largeurs adaptées. De plus, dans le cas où les paramètres (vitesse et direction) de mouvement des nœuds sont connus, nous avons proposé d'exploiter des techniques simples d'extrapolation afin de limiter les calculs complexes des méthodes de poursuite continue (tracking), très consommatrices en ressources. Dans une seconde étude, nous avons proposé une solution d'ordonnancement basée sur la technique du multiplexage spatial qui est une caractéristique fondamentale des systèmes MIMO. L'algorithme proposé (SCLS : Stream-Controlled Multiple Access) exploite les informations inter-couches (cross-layer) : environnement radio de la couche PHY et charge de trafic de la couche LIEN. Il permet de choisir l'ensemble des liens à activer simultanément et détermine sur chacun de ces liens, le nombre d'antennes à utiliser pour transmettre des flux parallèles. SCLS permet ainsi de minimiser le temps nécessaire pour satisfaire les demandes de trafic et de maximiser le débit global utilisé à chaque instant. Dans la troisième étude, nous avons considéré la problématique d'estimation des directions d'arrivée et de départ. Nous avons proposé un algorithme (E-Capon) d'estimation conjointe de ces directions ainsi que du retard de propagation des trajets multiples dans un canal MIMO. Nous nous sommes basés sur la méthode de Capon qui permet de réduire la complexité de traitement pour offrir une estimation rapide et robuste des informations relatives à la localisation des nœuds. Notre objectif est de concevoir une technique mieux adaptée aux changements dynamiques de topologie que l'on peut observer dans les réseaux sans fil.Recent advances in antennas processing and microelectronics have helped for the emergence of smart antennas and their use in public telecommunication systems. This technology allows sophisticated signal processing and provides significant performance benefits such as increased spectral efficiencies, reduced power consumption, interference cancellation, increased communication reliability and better connectivity. Smart antennas represent a broad variety of antenna technologies that significantly differ in terms of performance and transceiver complexity. The different antennas technologies include switched-beam antennas, adaptive array antennas and multiple-input multiple-output (MIMO) systems. The latter is already being implemented in latest generation equipments and standards like 3GPP-LTE and IEEE 802.11n. The focus of this thesis is to explore the various capabilities of smart antennas and to propose new mechanisms and systems for their use. In particular, we were interested in exploiting two multi-antenna systems' capabilities: spatial multiplexing and beamforming. In the first part of this thesis, we propose a new dynamic beamforming technique for mobile ad hoc networks, based on the LCMV beamformer. Mobiles nodes derive the weight vectors to form dynamic beams more adapted to their mobility parameters. The proposed scheme allows to form dynamic beams with less complexity but more adapted to possible uncertainty on mobile node locations.. Performance evaluations show that the proposed approach enhances system capacity and connectivity while reducing localization overhead and beam forming complexity. In the second part of this thesis, we design and evaluate a joint stream control and link TDMA-based scheduling algorithm (SCLS) for MIMO wireless mesh networks. SCLS is a cross layer resource allocation scheme that selects links to be activated simultaneously and determines the optimal number of streams to be used on each of them. This selection is based on streams' channel gains, traffic demands and interference levels. The proposed algorithm optimizes both the frame length and network capacity and throughput. In the third part, a joint Angle of Arrival (AOA), Angle of Departure (AOD) and Delay of Arrival algorithm, based on the Capon Beamformer, is proposed. These physical parameters of the received signals are needed to develop advanced antenna systems and other applications such as localization in indoor environments.The proposed algorithm reduces both complexity and computation time compared to subspace-based existing methods. The proposed approach works even if the number of multipaths exceeds the number of antenna elements.EVRY-INT (912282302) / SudocSudocFranceF

A Redundancy based Protocol for Safety Message Dissemination in Vehicular Ad Hoc Networks

International audienceThe diversity of applications types in vehicular ad hoc networks (VANETs) has spawned a large variety of messages that need to be disseminated in vehicle to vehicle (V2V) communication mode. The most critical messages are those dedicated for safety applications such as accident warning, road hazardous warning, signal violation warning, etc. The dissemination of this sort of messages is a challenging task in VANETs since they should be efficiently transmitted i.e. by achieving high packet delivery within a certain time limit and an acceptable overhead. In this work, we propose a robust and an original data dissemination protocol called Redundancy-based Protocol (RBP). Contrary to most of the density based protocols, the protocol is beaconless. It takes into account the surrounding vehicle density during the broadcasting process through a specific metric, named “packet redundancy ratio”, calculated locally at each vehicle. Based on this metric, each vehicle is able to dynamically determine the probability of rebroadcast in order to mitigate the broadcast storm problem. The simulation results prove that the proposed protocol outperforms the slotted 1- persistence scheme in terms of packet drop ratio, and network load while still maintaining a low End-to-End delay and high packet reachability. This scheme is suitable for safety applications, as well as for further kinds of application by saving the network capacity consumption

Revue de performance du secteur des TIC Tunisie, 2009/2010

Version anglaise disponible dans la Bibliothèque numérique du CRDI: Tunisia ICT sector performance review, 2009/201

Tunisia ICT sector performance review, 2009/2010

French version available in IDRC Digital Library: Revue de performance du secteur des TIC Tunisie, 2009/2010This analysis aims to enable telecom sector development. In 2010 the competitive landscape is characterized by a duopoly situation on the fixed-line level, a one-year monopoly for services linked to 3G, the intervention of three operators on the mobile level, and five private ISPs with one operator. Despite the fact that the liberalization experience is relatively young (dating from the beginning of 2000), gains have been remarkable, particularly in the fields of skills development and job creation. With the entrance of a third operator, the telecom sector advances towards a new development stage with diversification and innovative services

A Framework for Automatic Web Service Discovery Based on Semantics and NLP Techniques

As a greater number of Web Services are made available today, automatic discovery is recognized as an important task. To promote the automation of service discovery, different semantic languages have been created that allow describing the functionality of services in a machine interpretable form using Semantic Web technologies. The problem is that users do not have intimate knowledge about semantic Web service languages and related toolkits. In this paper, we propose a discovery framework that enables semantic Web service discovery based on keywords written in natural language. We describe a novel approach for automatic discovery of semantic Web services which employs Natural Language Processing techniques to match a user request, expressed in natural language, with a semantic Web service description. Additionally, we present an efficient semantic matching technique to compute the semantic distance between ontological concepts