Gestion de la qualité de service et planification optimale de réseaux de capteurs multimédia sans fil

RÉSUMÉ Un RCSF est constitué d'un certain nombre d'entités (capteurs) géographiquement dispersées, de taille réduite, avec une autonomie et une puissance de traitement réduites. Ces dispositifs sont utilisés pour réaliser, de manière indépendante, des tâches comme la surveillance, le contrôle de processus industriel, etc. Les avancées en microélectronique ont conduit à l'émergence des petites caméras (type CMOS) et microphones accessibles. Ces capteurs audio-visuels peuvent être intégrés dans un RCSF pour former des RCMSF. Dans certains types d'applications, comme la surveillance des frontières, un grand nombre de ce type de capteurs est susceptible d'être déployés, sur de vastes terrains. Un volume considérable de flux audio-visuel (en plus des données) doit être transmis au centre de contrôle (le collecteur, ou SINK) pour analyse et prise de décision. Il y a donc un besoin important en termes de bande passante, avec surtout une forte contrainte en termes de délai de transmission et d'autres paramètres de RCSF. Des solutions pour le routage d'information ont été développées pour des RCSF, mais ces protocoles n'ont pas pris en compte la génération à grande échelle des données multimédia, elles sont par conséquent inadaptées aux RCMSF. Les capteurs typiquement sont omnidirectionnels, c'est-à-dire qu'ils sont capables de capter des signaux qui proviennent de toutes les directions autour d'eux. Les capteurs multimédia, en particulier les capteurs de vidéo, sont de type directionnel. Pour ce type de capteurs, l'aire de captage est limitée à un secteur donné d'un plan tridimensionnel. Malheureusement, les modèles mathématiques développés pour le placement des RCMSF conventionnels ne peuvent pas être appliqués dans le cadre de la configuration et de la planification des réseaux de capteurs directionnels. De nouveaux modèles d'optimisation sont donc nécessaires pour la capture des principaux paramètres caractérisant les capteurs directionnels. Dans cette thèse, nous abordons donc les problèmes clés suivants: le routage des données hétérogènes (scalaires et multimédia) pour les nœuds d'un RCMSF afin d'assurer une meilleure QdS aux usagers; et le déploiement optimisé de capteurs directionnels d'un RCMSF dans un espace tridimensionnel dont le but est couvrir un ensemble de points d'intérêts définis dans tel espace. Notre thèse se compose de trois articles scientifiques, chacun traitant d'une problématique bien spécifique. Le premier article traite du problème du routage d'information pour les RCMSF basé sur la QdS. Nous proposons un nouveau protocole, AntSensNet, basé sur l'heuristique de la colonie de fourmis, qui utilise plusieurs métriques de QdS pour trouver de bonnes routes pour les données multimédia et l'information scalaire. Dans la pratique, le protocole établit d'abord une structure hiérarchique sur le réseau avant de choisir les chemins appropriés pour répondre aux diverses exigences de QdS des différents types de trafic qui circulent dans le réseau. Ceci permet de maximiser l'utilisation des ressources du réseau, tout en améliorant la performance de la transmission de l'information. En outre, AntSensNet est capable d'utiliser un mécanisme efficace d'ordonnancement de paquets et de multiples chemins afin d'obtenir la distorsion minimale au moment où une application fait la transmission de la vidéo dans le réseau. Dans le deuxième article nous continuons avec le sujet de la QdS dans le RCMSFs et, plus spécifiquement, nous abordons la problématique du contrôle d'admission pour ce type de réseau. Grâce au contrôle d'admission, il est possible de déterminer si un réseau est capable de supporter un nouveau flot de données. S'il n'y a pas de contrôle d'admission dans un RCMSF, le performance du réseau sera compromis car les ressources existantes dans le réseau ne seront pas assez pour tous les flots acceptés et cela entraînera beaucoup de problèmes comme la perte de paquets des flots. Nous proposons un nouveau schéma de contrôle d'admission de nouveaux flots multimédia pour un RCMSF. Le système proposé est en mesure de déterminer si un flot de données puisse être admis dans le réseau, compte tenu de l'état actuel des liaisons de communications et l'énergie des nœuds. La décision sur l'acceptation est prise de manière distribuée, sans utiliser une entité centrale. De plus, notre schéma se présente comme un plug-in, et est adaptable à d'éventuels protocoles de routage et MAC utilisés pour la transmission de données dans les RCMSF. Nos résultats de simulation montrent l'efficacité de notre approche pour répondre aux exigences de QdS des nouveaux flots de données. Finalement, notre troisième article traite du problème du déploiement optimal des capteurs multimédia dans un espace 3D. Tel que mentionné ci-dessus, la plupart des capteurs multimédia sont du type directionnel. De surcroît, ces capteurs sont plus coûteux et plus spécialisés que les capteurs scalaires. En conséquence, les déploiements aléatoires, qui sont typiques pour les capteurs scalaires, ne sont ni souhaitables ni adéquats pour les capteurs multimédia. A cet effet, nous proposons un modèle optimal de déploiement 3D de capteurs directionnels. Ce modèle vise à déterminer le nombre minimum de capteurs directionnels connectés, leur emplacement et leur configuration, qui sont nécessaires pour couvrir un ensemble de points de contrôle dans un espace 3D donné. La configuration de chaque capteur déployé est déterminée par trois paramètres : la plage de détection, le champ de vision (FoV) et l'orientation. Nous présentons une formulation « Integer Linear Programming » (ILP) pour trouver la solution exacte du problème et aussi, un algorithme glouton capable de trouver une solution approximative (mais efficace) du problème. Nous évaluons également différentes propriétés des solutions proposées par le biais de nombreuses simulations. Avec ces trois articles on a réussi à résoudre, d'une façon à la fois innovatrice et pratique, les problèmes de routage basé sur la QdS pour les RCMSF et le déploiement de capteurs directionnels, qui sont l'objectif principal de notre recherche.----------ABSTRACT A Wireless Sensor Network (WSN) consists of a set of embedded processing units, called sensors, communicating via wireless links, whose main function is the collection of parameters related to the surrounding environment, such as temperature, pressure or the presence/motion of objects. WSN are expected to have many applications in various fields, such as industrial processes, military surveillance, observation and monitoring of habitat, etc. The availability of inexpensive hardware such as CMOS cameras and microphones that are able to ubiquitously capture multimedia content from the environment has fostered the development of Wireless Multimedia Sensor Networks (WMSNs), i.e., networks of wirelessly interconnected devices that allow retrieving video and audio streams, still images, and scalar sensor data. In addition to the ability to retrieve multimedia data, WMSNs will be able to store, process in real time, correlate and fuse multimedia data originated from heterogeneous sources, and perform actions on the environment based on the content gathered. Many applications require the sensor network paradigm to be rethought in view of the need for mechanisms to deliver multimedia content with a certain level of quality of service (QoS). Due to high bandwidth, processing and stringent Qos requirements existing solutions are not feasible for WMSNs. Since the need to minimize the energy consumption has driven most of the research in sensor networks so far, there is a need to create mechanisms to efficiently deliver application-level QoS, and to map these requirements to network-layer metrics such as latency or delay. Additionally, in WSNs, an omnidirectional sensing model is often assumed where each sensor can equally detect its environment in each direction. Instead, multimedia sensors, specially video sensor, are directional sensors. A directional sensor is characterized by its sensing region which can be viewed as a sector in a three-dimensional plane. Therefore, it can only choose one active sector (or direction) at any time instant. Unfortunately, the many methods developed for deploying traditional WSNs cannot directly be used for optimizing and configuring directional WMSNs due to the different parameters involved. Therefore, new optimization models which capture the primary parameters characterizing directional sensors are necessary. The issues aforementioned are crucial challenges for the development of WMSNs. In this thesis, we are interested in the following aspects: routing of heterogeneous data (scalar and multimedia) from the nodes of a WMSN to the sink in order to provide better QoS experience to users; and an optimized deployment of directional sensors of a WMSN in a three-dimensional surface with the objective to cover all the control points as defined in such a space. Our thesis runs through three scientific papers, each addressing a specific problem. In our first paper, we address the problem of data routing based on different QoS metrics in a WMSN. We propose a new protocol AntSensNet, based on the traditional ant-based algorithm. The AntSensNet protocol builds a hierarchical structure on the network before choosing suitable paths to meet various QoS requirements from different kinds of traffic, thus maximizing network utilization, while improving its performance. In addition, AntSensNet is able to use a efficient multipath video packet scheduling in order to get minimum video distortion transmission. In the second paper, we address the problem of connection admission control for WMSNs. With admission control, it is possible to determine whether a network is capable of supporting a new data stream. Without admission control in a WMSN, the network performance will be compromised because the existing resources within the network cannot be enough for all the flows accepted and this will cause many problems such as packet loss and congestion. Taking multiple parameters into account, we propose a novel connection admission control scheme for the multimedia traffic circulating in the network. The proposed scheme is able to determine if a new flow can be admitted in the network considering the current link states and the energy of the nodes. The decision about accepting is taken in a distributed way, without trusting in a central entity to take this decision. In addition, our scheme works like a plug-in, being easily adaptable to any routing and MAC protocols. Our simulation results show the effectiveness of our approach to satisfy QoS requirements of flows and achieve fair bandwidth utilization and low jitter. Finally, in the third paper, we address the problem of optimal deployment of directional sensors in a 3D space. We have already mentioned that conventional methods to deploy omnidirectional sensors are not suitable to deploy directional sensors. To remedy this deficiency, we propose a mathematical model which aims at to determine the minimum number of connected directional multimedia sensor nodes and their configuration, needed to cover a set of control points in a given 3D space. The configuration of each deployed sensor is determined by three parameters: sensing range, field of view and orientation. We present the exact ILP formulation for the problem and an approximate (but computationally efficient) greedy algorithm solution. We also evaluate different properties of the proposed solutions through extensive simulations. Overall, the proposed solutions in this thesis are both innovative and practical. With these three papers, we have been successfully resolved the problems of a QoS-based routing protocol for WMSN and an optimal deployment of directional sensors in a 3D space, which are the components of the main objective of this thesis

A Remote Capacity Utilization Estimator for WLANs

In WLANs, the capacity of a node is not fixed and can vary dramatically due to the shared nature of the medium under the IEEE 802.11 MAC mechanism. There are two main methods of capacity estimation in WLANs: Active methods based upon probing packets that consume the bandwidth of the channel and do not scale well. Passive methods based upon analyzing the transmitted packets that avoid the overhead of transmitting probe packets and perform with greater accuracy. Furthermore, passive methods can be implemented locally or remotely. Local passive methods require an additional dissemination mechanism in order to communicate the capacity information to other network nodes which adds complexity and can be unreliable under adverse network conditions. On the other hand, remote passive methods do not require a dissemination mechanism and so can be simpler to implement and also do not suffer from communication reliability issues. Many applications (e.g. ANDSF etc) can benefit from utilizing this capacity information. Therefore, in this thesis we propose a new remote passive Capacity Utilization estimator performed by neighbour nodes. However, there will be an error associated with the measurements owing to the differences in the wireless medium as observed by the different nodes’ location. The main undertaking of this thesis is to address this issue. An error model is developed to analyse the main sources of error and to determine their impact on the accuracy of the estimator. Arising from this model, a number of modifications are implemented to improve the accuracy of the estimator. The network simulator ns2 is used to investigate the performance of the estimator and the results from a range of different test scenarios indicate its feasibility and accuracy as a passive remote method. Finally, the estimator is deployed in a node saturation detection scheme where it is shown to outperform two other similar schemes based upon queue observation and probing with ping packets

Recent Advances in Wireless Communications and Networks

This book focuses on the current hottest issues from the lowest layers to the upper layers of wireless communication networks and provides "real-time" research progress on these issues. The authors have made every effort to systematically organize the information on these topics to make it easily accessible to readers of any level. This book also maintains the balance between current research results and their theoretical support. In this book, a variety of novel techniques in wireless communications and networks are investigated. The authors attempt to present these topics in detail. Insightful and reader-friendly descriptions are presented to nourish readers of any level, from practicing and knowledgeable communication engineers to beginning or professional researchers. All interested readers can easily find noteworthy materials in much greater detail than in previous publications and in the references cited in these chapters

Enabling architectures for QoS provisioning

Nowadays, new multimedia services have been deployed with stringent requirements for Quality of Service (QoS). The QoS provisioning is faced with the heterogeneity of system components. This thesis presents two research: on architectures for QoS management at the application layer, fulfilled mainly by software components; and on distributed software architectures for routing devices providing desired QoS at the underlying communication layer. At the application layer, the QoS architecture we propose, based on the Quality Driven Delivery (QDD) framework, deals with the increasing amount of QoS information of a distributed system. Based on various QoS information models we define for key actors of a distributed system, a QoS information base is generated using QoS information collecting and analysis tools. To translate QoS information among different components, we propose mechanisms to build QoS mapping rules from statistical data. Experiments demonstrate that efficient QoS decisions can be made effectively regarding the contribution of all system components with the help of the QoS information management system. At the underlying layer, we investigate distributed and scalable software architectures for QoS-enabled devices. Due to the huge volume of traffic to be switched, the traditional software model used for current generation routers, where the control card of the router performs all the processing tasks, is no longer appropriate in the near future. We propose a new scalable and distributed architecture to fully exploit the hardware platforms of the next generation routers, and to improve the quality of routers, particularly with respect to scalability and to a lesser extent to resiliency and availability. Our proposal is a distributed software framework where control tasks are shared among the control and line cards of the router. Specific architectures for routing, signaling protocols and routing table management are developed. We investigate the challenges for such distributed architectures and proposed various solutions to overcome them. Based on a general distributed software framework, an efficient scalable distributed architecture for MPLS/LDP and different scalable distributed schemes for the routing table manager (RTM) are developed. We also evaluate the performance of proposed distributed schemes and discuss where to deploy these architectures depending on the type of routers (i.e., their hardware capacity

Service Oriented Mobile Computing

La diffusione di concetti quali Pervasive e Mobile Computing introduce nell'ambito dei sistemi distribuiti due aspetti fondamentali: la mobilità dell'utente e l'interazione con l'ambiente circostante, favorite anche dal crescente utilizzo di dispositivi mobili dotati di connettività wireless come prodotti di consumo. Per estendere le funzionalità introdotte nell'ambito dei sistemi distribuiti dalle Architetture Orientate ai Servizi (SOA) e dal paradigma peer-to-peer anche a dispositivi dalle risorse limitate (in termini di capacità computazionale, memoria e batteria), è necessario disporre di un middleware leggero e progettato tenendo in considerazione tali caratteristiche. In questa tesi viene presentato NAM (Networked Autonomic Machine), un formalismo che descrive in modo esaustivo un sistema di questo tipo; si tratta di un modello teorico per la definizione di entità hardware e software in grado di condividere le proprie risorse in modo completamente altruistico. In particolare, il lavoro si concentra sulla definizione e gestione di un determinato tipo di risorse, i servizi, che possono essere offerti ed utilizzati da dispositivi mobili, mediante meccanismi di composizione e migrazione. NSAM (Networked Service-oriented Autonomic Machine) è una specializzazione di NAM per la condivisione di servizi in una rete peer-to-peer, ed è basato su tre concetti fondamentali: schemi di overlay, composizione dinamica di servizi e auto-configurazione dei peer. Nella tesi vengono presentate anche diverse attività applicative, che fanno riferimento all'utilizzo di due middleware sviluppati dal gruppo di Sistemi Distribuiti (DSG) dell'Università di Parma: SP2A (Service Oriented Peer-to-peer Architecture), framework per lo sviluppo di applicazioni distribuite attraverso la condivisione di risorse in una rete peer-to-peer, e Jxta-Soap che consente la condivisione di Web Services in una rete peer-to-peer JXTA. Le applicazioni realizzate spaziano dall'ambito della logistica, alla creazione di comunità per l'e-learning, all'Ambient Intelligence alla gestione delle emergenze, ed hanno come denominatore comune la creazione di reti eterogenee e la condivisione di risorse anche tra dispositivi mobili. Viene inoltre messo in evidenza come tali applicazioni possano essere ottimizzate mediante l'introduzione del framework NAM descritto, per consentire la condivisione di diversi tipi di risorse in modo efficiente e proattivo

Interaktive latenzkritische Anwendungen in mobilen Ad-hoc Netzen

In this thesis we discuss the challenges that latency-sensitive interactive applications face in mobile ad-hoc networks. By using multi-player games as an example, we argue that the traditional client-server architecture is unsuitable for this new environment. We consequently create a novel communication architecture as well as quality of service mechanisms that can support the network requirements of such applications in mobile environments. By using a number of distributed zone servers that are selected and managed dynamically by our server selection algorithm, we provide a scalable approach that offers the necessary redundancy. Furthermore, we propose additional quality of service mechanisms to reduce latency and packet loss for interactive applications. We evaluate our approach through network simulation and realistic mobile gaming scenarios. The performance of our evaluation is checked against real-world measurements.In dieser Arbeit werden die Probleme und Herausforderungen von latenz-kritischen interactiven Computeranwendungen in mobilen Ad-hoc Netzen untersucht. Am Beispiel von Mehrbenutzercomputerspielen zeigen wir, dass traditionelle Client-Server Architekturen für diese neuen Umgebungen ungeeignet sind. Im Rahmen dieser Arbeit wird daher eine neue Kommunikationsarchitektur sowie verschiedene Mechanismen zur Erhöhung der Dienstgüte vorgeschlagen. Mit Hilfe von Zonenserver, die durch den Serverauswahlalgorithmus ausgesucht und verwaltet werden zeigen wir einen Ansatz auf, der sowohl bezüglich der Netzgröße skalierbar ist als auch die notwendige Redundanz bereitstellt. Wir zeigen die Funktionalität und die Leistung unseres Ansatzes mit Hilfe von Netzsimulationen bei denen realistische Szenarien für mobiles Spielen simuliert werden. Der hierbei benutze Netzsimulator wurde dafür auf Basis von eigenen Messungen verbessert und für das jeweilige Szenario passend eingestellt