Dans le cadre des réseaux ad hoc à grande envergure, le concept de clusterisation peut être mis à profit afin de faire face aux problèmes de passage à l'échelle et d'accroître les performances du système. Tout d’abord, cette thèse présente notre algorithme de clusterisation TBCA ‘Tiered based Clustering algorithm’, ayant pour objectif d’organiser le processus de clusterisation en couches et de réduire au maximum le trafic de contrôle associé à la phase d’établissement et de maintenance de l’infrastructure virtuelle générée. La formation et la maintenance d’une infrastructure virtuelle ne sont pas une fin en soi. Dans cet axe, on a exploité les apports de notre mécanisme de clusterisation conjointement avec le mode veille, à travers la proposition de l’approche de conservation d’énergie baptisée CPPCM ‘Cluster based Prioritized Power Conservation Mechanism’ avec deux variantes. Notre objectif principal est de réduire la consommation d’énergie tout en assurant l’acheminement des paquets de données sans endurer des temps d’attente importants aux niveaux des files d’attente des nœuds impliqués dans le transfert. Nous avons proposé aussi un algorithme de routage LCR ‘Layered Cluster based Routing’ se basant sur l’existence d’une infrastructure virtuelle. L’exploitation des apports de notre mécanisme TBCA et la limitation des tâches de routage additionnelles à un sous ensemble de nœuds sont des atouts pour assurer le passage à l’échelle de notre algorithme. / Relying on a virtual infrastructure seems a promising approach to overcome the scalability problem in large scale ad hoc networks. First, we propose a clustering mechanism, TBCA ‘Tiered based Clustering algorithm’, operating in a layered manner and exploiting the eventual collision to accelerate the clustering process. Our mechanism does not necessitate any type of neighbourhood knowledge, trying to alleviate the network from some control messages exchanged during the clustering and maintenance process. Since the energy consumption is still a critical issue, we combining a clustering technique and the power saving mode in order to conserve energy without affecting network performance. The main contribution of our power saving approach lies on the differentiation among packets based on the amount of network resources they have been so far consumed. Besides, the proposed structure of the beacon interval can be adjusted dynamically and locally by each node according to its own specific requirements. We propose also a routing algorithm, LCR ‘Layered Cluster based Routing’. The basic idea consists on assigning additional tasks to a limited set of dominating nodes, satisfying specific requirements while exploiting the benefits of our clustering algorithm TBCA.

Nos travaux se positionnent dans le cadre de l'algorithmique distribuée et plus particulièrement des réseaux ad hoc. Les réseaux ad hoc sont auto-organisés en permettant des échanges directs entre nœuds mobiles et ne reposent sur aucune infrastructure. Chaque nœud peut se déplacer librement et indépendamment des autres impliquant une modification perpétuelle de la topologie. Dans ce contexte, la probabilité que des défaillances surviennent dans le réseau est importante. Ces défaillances gênent le bon fonctionnement du réseau et peuvent même entrainer une paralysie de celui-ci. C'est pourquoi la conception de solutions pour de tels réseaux nécessitent des mécanismes de gestion de fautes. Parmi ceux-ci, l'approche d'auto-stabilisation permet à un système de gérer les fautes transitoires. Nous étendons cette approche pour répondre aux principaux problèmes liés à la mobilité des nœuds. Notre objectif est de répondre à un double besoin d'auto-organisation du réseau et d'optimisation du nombre de messages échangés. Notre approche consiste à découper le réseau en clusters afin de lui donner une structure hiérarchique. Cette dernière rend l'utilisation du réseau plus efficace et plus performante. L'algorithme que nous avons développé à cet effet est auto-stabilisant et n'est basé que sur des connaissances locales. Nous exploitons cette solution pour proposer deux utilisations efficaces : la diffusion d'informations dans le réseau et le routage. La diffusion d'informations exploite un arbre couvrant inter-clusters, construit sans surcoût, en parallèle de la clusterisation. Le routage quant à lui exploite cet arbre pour permettre à la fois d'optimiser le délai de bout en bout et le nombre de messages échangés. / Our work relies in the domain of distributed system, more preciselly ad hoc networks. Ad hoc networks are self-organized allowing direct exchanges between mobile nodes and do not rely on any infrastruture. Each node can move freely and independently of each others involving continuous topology variability. In this context, the probability that a failure occurs in the network is high. These failures hinder the proper functioning of the network and even causes its paralysis. Therefore, designing solutions for such networks requires fault management mechanisms. Among these, a self-stabilizating approach allows the system to withstand transient faults. We extend this approach to answer the problems induced by nodes mobility. We have two main objectives: a self-organizing network and optimizing number of exchanged messages. Our approach consists in dividing the network into clusters in order to give it a hierarchical structure. This solution allows a more efficient and effective network use. The algorithm that we developed for this purpose is a self-stabilizing algorithm based only on local informations. Based on this solution, we propose two efficient use cases: Information broadcast and a routing protocol. Information broadcast uses an inter-cluster spanning tree, generated without any overhead. In the same time as the clustering process. The routing protocol uses this tree for both round trip and number of exchanged messages optimization.

A dissertation submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science in Engineering, 2016 / The design and implementation of network coding into a location based ad- dressing algorithm for VANET has been investigated. Theoretical analysis of the network coding algorithm has been done by using a simplified topology called the ladder topology. The theoretical models were shown to describe the way that network coding and standard location based addressing works over the VANET network. All tests were performed over simulation. Network coding was shown to improve performance by a factor of 1.5 to 2 times in both simulation and theoretical models. The theoretical models demonstrate a fundamental limit to how much network coding can improve performance by, and these were confirmed by the simulations. Network coding does have a susceptibility to interference, but the other benefits of the techniques are substantial despite this. Network coding demonstrates strong possibilities for future development for VANET protocols. The ladder topology is an important tool for future analysis. / GS

Acoustic networks of autonomous underwater vehicles (AUVs) show great promise, but a lack of simulation tools and reliance on protocols originally developed for terrestrial radio networks has hindered progress. This work addresses both issues. A new simulator of underwater communication among AUVs provides accurate communication modeling and flexible vehicle behavior, while a new routing protocol, location-aware source routing (LASR) provides superior network performance. The new simulator was used to evaluate communication without networking, and then with networking using the coding or dynamic source routing (DSR) protocols. The results confirmed that a network was essential to ensure effective fleet-wide communication. The flooding protocol provided extremely reliable communication but with low message volumes. The DSR protocol, a popular routing protocol due to its effectiveness in terrestrial radio networks, proved to be a bad choice in an acoustic environment: in most cases, it suffered from both poor reliability and low message volumes. Due to the high acoustic latency, even moderate vehicle speeds caused the network topology to change faster than DSR could adapt. DSR's reliance on shortest-path routing also proved to be a significant disadvantage. Several DSR optimizations were also tested; most proved to be unhelpful or actually harmful in an underwater acoustic network. LASR was developed to address the problems noted in flooding and DSR. LASR was loosely derived from DSR, most significantly retaining source routes and the reply/request route discovery technique. However, LASR added features which proved, in simulation, to be significant advantages -- two of the most effective were a link/route metric and a node tracking system. To replace shortest-path routing, LASR used the expected transmission count (ETX) metric. / This allowed LASR to make more informed routing decisions which greatly increased performance compared to DSR. The node tracking system was the most novel addition: using only implicit communication coupled with the use of time-division multiple access (TDMA), the tracking system provided predicted node locations. These predictions made it possible for LASR to proactively respond to topology changes. In most cases, LASR outperformed flooding and DSR in message delivery reliability and message delivery volume. / by Edward A. Carlson. / Thesis (Ph.D.)--Florida Atlantic University, 2009. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2009. Mode of access: World Wide Web.

Controlling the cooperative behaviors of a fleet of autonomous underwater vehicles in a stochastic, complex environment is a formidable challenge in artificial intelligence. The complexity arises from the challenges of limited navigation and communication capabilities of underwater environment. A time critical cooperative operation by acoustic networks of Multiple Cooperative Vehicles (MCVs) necessitates a robust task allocation mechanism and an efficient path planning model. In this work, we present solutions to investigate two aspects of the cooperative schema for multiple underwater vehicles under realistic underwater acoustic communications: a Location-aided Task Allocation Framework (LAAF) algorithm for multi-target task assignment and a mathematical programming model, the Grid-based Multi-Objective Optimal Programming (GMOOP), for finding an optimal vehicle command decision given a set of objectives and constraints. We demonstrate that, the location-aided auction strategies perform significantly better than the generic auction algorithm in terms of effective task allocation time and information bandwidth requirements. In a typical task assignment scenario, the time needed in the LAAF algorithm is only a fraction compared to the generic auction algorithm. On the other hand; the GMOOP path planning technique provides a unique means for multi-objective tasks by cooperative agents with limited communication capabilities. Under different environmental settings, the GMOOP path planning technique is proved to provide a method with balance of sufficient expressive power and flexibility, and its solution algorithms tractable in terms of mission completion time, with a limited increase of overhead in acoustic communication. Prior to this work, existing multi-objective action selection methods were limited to robust networks where constant communication available. / The dynamic task allocation, together with the GMOOP path planning controller, provides a comprehensive solution to the search-classify tasks for cooperative AUVs. / by Yueyue Deng. / Thesis (Ph.D.)--Florida Atlantic University, 2010. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2010. Mode of access: World Wide Web.

Um dos grandes avanços na área da computação nas últimas décadas refere-se aos sistemas distribuídos. O uso de tais sistemas tem crescido vertiginosamente nos últimos anos. Com o surgimento e uso de tecnologias de redes sem-fio, os sistemas ganharam mobilidade e dinamismo. Pessoas podem entrar ou sair de seus locais de trabalho, de entretenimento ou mesmo de suas casas com seus computadores móveis; redes podem ser formadas ou extintas conforme a dinâmica de um grupo de pessoas; e novos serviços podem ser disponibilizados ou interrompidos. Em sistemas como tais, um sistema de localização de serviços automático é fundamental para acompanhar as contínuas modificações na rede. A localização de serviços permite que, em uma rede de endereçamento estático ou dinâmico, dispositivos e serviços possam ser encontrados de modo completamente automático. A presente dissertação propõe um sistema de localização lógica (endereçamento) de serviços e dispositivos em uma rede local ou geograficamente distribuída, indo ao encontro às necessidades de controle de sistemas distribuídos dinâmicos, contribuindo ao mesmo tempo com questões de usabilidade e configuração automática de redes. O sistema, também, busca resolver questões relacionadas ao uso dos serviços entre redes protegidas por firewalls ou que utilizam configurações de NAT. / In the last decades, one of the most important progresses in computation is related to the distributed systems. The usage of these systems has increased a lot, in the last years. Due the emergence of wireless technologies, systems have acquired mobility and dynamism. People can enter or leave places, such as home, workplaces and entertainment spots, caring their mobile computers; networks can be formed or extinguished in accordance with the people dynamism; and new services can be available or interrupted. At these systems, a service location system is needed to keep track of the unceasing modifications in the network. The service location enables that services and devices can be found, at dynamic or static networks. This master thesis proposes a system for location of the logical addresses of services and devices at local or wide area networks. This work contributes to issues related to distributed systems control, usability and automatic network configuration. This system also solves questions related to service usage between networks using firewalls or NAT. Besides that, other points related to network interconnections in distributed systems, for example, using the Internet, are raised and solved.

The scalability of QUIC-TCP was examined by expanding previous developmental 11-node, 4-flow topology to over 30 nodes with 11 flows to validate QUIC-TCP for larger networks. The topology was simulated using ns-2 network simulator with the same ns-2 module of FAST-TCP modified to produce QUIC-TCP agent that the original development used. A symmetrical topology and a random topology were examined. Fairness, aggregate throughput and the object of the utility function were used as validation criteria. It was shown through simulation that QUICTCP optimized the utility function and demonstrated a good balance between aggregate throughput and fairness; therefore QUIC-TCP is indeed scalable to larger networks. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2013.

Cognitive radio technology that enables dynamic spectrum access has been a promising solution for the spectrum scarcity problem. Cognitive radio networks enable the communication on both licensed and unlicensed channels, having the potential to better solve the interference and collision issues. Channel assignment is of great importance in cognitive radio networks. When operating on licensed channels, the objective is to exploit spectrum holes through cognitive communication, giving priority to the primary users. In this dissertation, we focus on the development of efficient channel assignment algorithms and protocols to improve network performance for cognitive radio wireless networks. The first contribution is on channel assignment for cognitive radio wireless sensor networks aiming to provide robust topology control, as well as to increase network throughput and data delivery rate. The approach is then extended to specific cognitive radio network applications achieving improved performances. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2016. / FAU Electronic Theses and Dissertations Collection

A Wireless Sensor Network (WSN) is composed of low-cost electronic devices with sensing, data storage and transmitting capabilities, powered by batteries. There are extensive studies in the field of WSN investigating different algorithms and protocols for data collection. A data collector can be static or mobile. Using a mobile data collector can extend network lifetime and can be used to collect sensor data in hardly accessible locations, partitioned networks, and delay-tolerant networks. The implementation of the mobile data collector in our study consists of combining two different platforms: the Crossbow sensor hardware and the NXT Legos. We developed an application for data collection and sensor querying support. Another important contribution is designing a semi-autonomous robot control. This hardware prototype implementation shows the benefits of using a mobile data collector in WSN. It also serves as a reference in developing future applications for mobile WSNs. / by Pedro L. Heshike. / Thesis (M.S.C.S.)--Florida Atlantic University, 2011. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2011. Mode of access: World Wide Web.

Este trabalho estuda a implementação do sistema de Quorum associado ao algoritmo epidêmico Gossip, a implementação de um novo algoritmo de economia de energia - o PWSave - e o protocolo de roteamento AODV em um cenário com e sem falhas de uma rede ad hoc com mobilidade. Optou-se por implementar este trabalho em um ambiente de simulação, dado que a modelagem matemática da associação do Gossip, Quorum e PWSave com os 80 nós - quantidade de nós escolhida para o ambiente de simulação - apresentaria maior complexidade e demora ao abranger todas as variáveis de ambiente desse conjunto de soluções para cada nó presente na rede. A rotina de programação - com o uso de loops para os trabalhos repetitivos - presente no ambiente de simulação permite que os experimentos sejam efetuados mais rapidamente e com menor probabilidade de erros. Os estudos [1], [2] demonstraram, respectivamente, que soluções abrangendo o algoritmo epidêmico Gossip e o sistema de compartilhamento de dados Quorum apresentam resultados favoráveis para uma rede ad hoc com alta mobilidade. Em [1] é apresentado um cenário muito próximo ao implementado neste trabalho, com a utilização do algoritmo Gossip ao protocolo de roteamento Ad-Hoc On-Demand Distance Vector (AODV). Os parâmetros analisados foram os mesmos, a saber: routes requests (RREQ), perda de pacote, vazão e latência. Os resultados do cenário simulado mostram uma diminuição no número de RREQs em uma rede ad hoc, e os demais parâmetros, medidos no ambiente de simulação, são pouco afetados. De acordo com [2] constata-se que há um aumento da resiliência e da vazão da rede e uma menor sobrecarga causada pela distribuição da informação na rede ad hoc pelo sistema de Quorum. A associação do algoritmo Gossip com o sistema de Quorum resultou em uma diminuição considerável de RREQs e perda de pacotes, mas o parâmetro de consumo de energia, que deve ser um fator importante em uma rede ad hoc e/ou uma rede sensor, não apresentou nenhuma melhora. Portanto, foi implementada uma solução adicional ao Gossip e ao Quorum, com o desenvolvimento de um novo algoritmo de economia de energia denominado de PWSave, no simulador Glomosim com o protocolo de roteamento AODV. O PWSave é responsável pelo adormecimento dos nós da rede que não estejam processando informações, ou seja, os nós, no momento do adormecimento, não poderão trocar dados ou auxiliar na formação de rotas da rede. O PWSave associado ao Gossip e ao sistema de Quorum apresenta resultados que refletem ma diminuição no consumo de energia próxima a 10% em comparação com a solução da associação do Gossip com o sistema de Quorum sem a implementação de PWSave. Os resultados da simulação mostram que a associação de Gossip, Quorum e PWSave acarreta uma redução no número de RREQs e na taxa de perda de pacotes sem degradar muito características de fluxo e latência, além de propiciar uma considerável economia no consumo de energia. / This work studies the implementation of the Quorum system associated with the Gossip algorithm, the implementation of a new power saving algorithm - the PWSave - and the routing protocol AODV in a scenario with and without failures of an ad hoc network with mobility. It has been chosen to implement this work in an environment of simulation, because the mathematical modeling of the association of Gossip, Quorum and PWSave with 80 nodes - number of nodes that has been chosen for the simulation environment - would present a higher complexity and delay to address all environment variables of the solutions set for each node present in the network. The programming routine - with the use of loops for the repetitive works - present in the simulation environment allows the experiments to be performed faster and with less probability of errors. The studies [1], [2] have shown, respectively, that solutions covering the Gossip epidemic algorithm and the system for sharing data Quorum show favorable results for an ad hoc network with high mobility. In [1] is presented a scenario very close to that implemented in this work, using the Gossip algorithm associated to the routing protocol Ad-Hoc On-Demand Distance Vector (AODV). The parameters analyzed were the same: routes requests (RREQ), packet loss, throughput and latency. The simulated scenario results show a decrease in the number of RREQs in an ad hoc network, and the other parameters, measured in the simulation environment, are little afected. According to [2] it is noted that there is an increase in the resilience and throughput of the network and a lower overload caused by the distribution of the information in the ad hoc network by the Quorum system. The association of the Gossip algorithm with the Quorum system resulted in a considerable decrease of RREQs and packet loss, but the parameter of energy consumption, which is an important factor in an ad hoc network and/or a sensor network, shows no improvement. Therefore, an additional solution was associated to the Gossip and to the Quorum, with the development of a new power saving algorithm named PWSave, in the simulator Glomosim with the routing protocol AODV. The PWSave is responsable for the sleeping state of the network nodes when they are not processing information: the nodes at the time of sleep cannot exchange data or assist in the building of network routes. The PWSave associated with the Gossip and Quorum system provides a decrease of the energy consumption close to 10% compared to the association solution of the Gossip with the Quorum system without the PWSave implementation. The results of simulation show that the association of the Gossip, Quorum and PWSave produces a reduction in the number of RREQs and in the rate of packets loss without degrading much the throughput and latency characteristics, providing a considerable energy consumption economy.