Self-Stabilizing Message Routing in Mobile ad hoc Networks

We present a self-stabilizing algorithm for routing messages between arbitrary pairs of nodes in a mobile ad hoc network. Our algorithm assumes the availability of a reliable GPS service, which supplies mobile nodes with accurate information about real time and about their own geographical locations. The GPS service provides an external, shared source of consistency for mobile nodes, allowing them to label and timestamp messages, and thereby aiding in recovery from failures. Our algorithm utilizes a Virtual Infrastructure programming abstraction layer, consisting of mobile client nodes, virtual stationary timed machines called Virtual Stationary Automata (VSAs), and a local broadcast service connecting VSAs and mobile clients. VSAs are associated with predetermined regions in the plane, and are emulated in a self-stabilizing manner by the mobile nodes. VSAs are relatively stable in the face of node mobility and failure, and can be used to simplify algorithm development for mobile networks. Our routing algorithm consists of three subalgorithms: [(1)] a VSA-to-VSA geographical routing algorithm, [2] a mobile client location management algorithm, and [3] the main algorithm, which utilizes both location management and geographical routing. All three subalgorithms are self-stabilizing, and consequently, the entire algorithm is also self-stabilizing

Reliable & Efficient Data Centric Storage for Data Management in Wireless Sensor Networks

Wireless Sensor Networks (WSNs) have become a mature technology aimed at performing environmental monitoring and data collection. Nonetheless, harnessing the power of a WSN presents a number of research challenges. WSN application developers have to deal both with the business logic of the application and with WSN's issues, such as those related to networking (routing), storage, and transport. A middleware can cope with this emerging complexity, and can provide the necessary abstractions for the definition, creation and maintenance of applications. The final goal of most WSN applications is to gather data from the environment, and to transport such data to the user applications, that usually resides outside the WSN. Techniques for data collection can be based on external storage, local storage and in-network storage. External storage sends data to the sink (a centralized data collector that provides data to the users through other networks) as soon as they are collected. This paradigm implies the continuous presence of a sink in the WSN, and data can hardly be pre-processed before sent to the sink. Moreover, these transport mechanisms create an hotspot on the sensors around the sink. Local storage stores data on a set of sensors that depends on the identity of the sensor collecting them, and implies that requests for data must be broadcast to all the sensors, since the sink can hardly know in advance the identity of the sensors that collected the data the sink is interested in. In-network storage and in particular Data Centric Storage (DCS) stores data on a set of sensors that depend on a meta-datum describing the data. DCS is a paradigm that is promising for Data Management in WSNs, since it addresses the problem of scalability (DCS employs unicast communications to manage WSNs), allows in-network data preprocessing and can mitigate hot-spots insurgence. This thesis studies the use of DCS for Data Management in middleware for WSNs. Since WSNs can feature different paradigms for data routing (geographical routing and more traditional tree routing), this thesis introduces two different DCS protocols for these two different kinds of WNSs. Q-NiGHT is based on geographical routing and it can manage the quantity of resources that are assigned to the storage of different meta-data, and implements a load balance for the data storage over the sensors in the WSN. Z-DaSt is built on top of ZigBee networks, and exploits the standard ZigBee mechanisms to harness the power of ZigBee routing protocol and network formation mechanisms. Dependability is another issue that was subject to research work. Most current approaches employ replication as the mean to ensure data availability. A possible enhancement is the use of erasure coding to improve the persistence of data while saving on memory usage on the sensors. Finally, erasure coding was applied also to gossiping algorithms, to realize an efficient data management. The technique is compared to the state-of-the-art to identify the benefits it can provide to data collection algorithms and to data availability techniques

Distributed Systems and Mobile Computing

The book is about Distributed Systems and Mobile Computing. This is a branch of Computer Science devoted to the study of systems whose components are in different physical locations and have limited communication capabilities. Such components may be static, often organized in a network, or may be able to move in a discrete or continuous environment. The theoretical study of such systems has applications ranging from swarms of mobile robots (e.g., drones) to sensor networks, autonomous intelligent vehicles, the Internet of Things, and crawlers on the Web. The book includes five articles. Two of them are about networks: the first one studies the formation of networks by agents that interact randomly and have the ability to form connections; the second one is a study of clustering models and algorithms. The three remaining articles are concerned with autonomous mobile robots operating in continuous space. One article studies the classical gathering problem, where all robots have to reach a common location, and proposes a fast algorithm for robots that are endowed with a compass but have limited visibility. The last two articles deal with the evacuations problem, where two robots have to locate an exit point and evacuate a region in the shortest possible time

Protocoles de routage sans connaissance de voisinage pour réseaux radio multi-sauts

L'efficacité énergétique constitue l'objectif clef pour la conception des protocoles de communication pour des réseaux de capteurs radio multi-sauts. Beaucoup d'efforts ont été réalisés à différents niveaux de la pile protocolaire à travers des algorithmes d'agrégation spatiale et temporelle des données, des protocoles de routage efficaces en énergie, et des couches d'accès au médium avec des mécanismes d'ordonnancement permettant de mettre la radio en état d'endormissement afin d'économiser l'énergie. Pour autant, ces protocoles utilisent de façon importante des paquets de contrôle et de découverte du voisinage qui sont coûteux en énergie. En outre, cela se fait très souvent sans aucune interaction entre les différentes couches de la pile. Ces travaux de thèse s'intéressent donc particulièrement à la problématique de l'énergie des réseaux de capteurs à travers des protocoles de routage et d'accès au médium. Les contributions de cette thèse se résument de la manière suivante : Nous nous sommes tout d'abord intéressés à la problématique de l'énergie au niveau routage. Dans cette partie, les contributions se subdivisent en deux parties. Dans un premier temps, nous avons proposé une analyse théorique de la consommation d'énergie des protocoles de routage des réseaux radio multi-sauts d'appréhender au mieux les avantages et les inconvénients des uns et des autres en présence des modèles de trafic variables, un diamètre du réseau variable également et un modèle radio qui permet de modéliser les erreurs de réception des paquets. À l'issue de cette première étude, nous sommes parvenus à la conclusion que pour être économe en énergie, un protocole de routage doit avoir des approches similaires à celle des protocoles de routage géographique sans message hello. Puis, dans un second temps, nous introduisons une étude de l'influence des stratégies de relayage dans un voisinage à 1 saut sur les métriques de performance comme le taux de livraison, le nombre de messages dupliqués et la consommation d'énergie. Cette étude est suivie par une première proposition de protocole de routage géographique sans message hello (Pizza-Forwarding (PF)) exploitant des zones de relayage optimisées et sans aucune hypothèse sur les propriétés du canal radio. Dans le but de réduire considérablement la consommation de PF, nous proposons de le combiner avec une adaptation d'un protocole MAC asynchrone efficace en énergie à travers une approche transversale. La combinaison de ces deux approches montre un gain significatif en terme d'économie d'énergie avec des très bon taux de livraison et cela quels que soient les scénarios et la nature de la topologique.Energy-efficient communication protocol is a primary design goal for Wireless Sensor Networks (WSNs). Many efforts have been done to save energy anywhere in the protocol stack through temporal and spatial data aggregation schemes, energy-aware routing protocols, activity scheduling and energy-efficient MAC protocols with duty cycle. However both control packets and beacons remain which induces a huge waste energy. Moreover, their design follows the classical layered approach with the principle of modularity in system development, which can lead to a poor performance in WSNs. This thesis focuses on the issues of energy in WSNs through energy-efficient routing and medium access control protocols. The constributions of this thesis can be summarized as follows: First, we are interested on the energy issues at the routing layer for multihop wireless sensor networks (WSNs). We propose a mathematical framework to model and analyze the energy consumption of routing protocols in multihop WSNs by taking into account the protocol parameters, the traffic pattern and the network characteristics defined by the medium channel properties, the dynamic topology behavior, the network diameter and the node density. In this study, we show that Beacon-less routing protocol should be a best candidate to save energy in WSNs. We investigate the performance of some existing relay selection schemes which are used by Beacon-less routing protocols. Extensive simulations are proposed to evaluate their performance locally in terms of packet delivery ratio, duplicated packet and delay. Then, we extend the work in multihop wiriless networks and develop an optimal solution, Enhanced Nearest Forwarding within Radius, which tries to minimize the per-hop expected number of retranmissions in order to save energy. We present a new beaconless routing protocol called Pizza-Forwarding (PF) without any assumption on the radio environment: neither the radio range nor symmetric radio links nor radio properties (shadowing, etc.) are assumed or restricted. A classical greedy mode is proposed. To overcome the hole problem, packets are forwarded to an optimal node in the two hop neighbor following a reactive and optimized neighborhood discovery. In order to save energy due to idle listening and overhearing, we propose to combine PF's main concepts with an energy-efficient MAC protocol to provide a joint MAC/routing protocol suitable for a real radio environment. Performance results lead to conclude to the powerful behavior of PFMAC.VILLEURBANNE-DOC'INSA-Bib. elec. (692669901) / SudocSudocFranceF