Tesi sul tema "Distributed network with mesh topology"

Network on Chip is a scalable and flexible communication infrastructure for the design of core based System on Chip. Communication performance of a NoC depends heavily on the routing algorithm. Deterministic and adaptive distributed routing algorithms have been advocated in all the current NoC architectural proposals. In this thesis we make a case for the use of source routing for NoCs, especially for regular topologies like mesh. The advantages of source routing include in-order packet delivery; faster and simpler router design; and possibility of mixing non-minimal paths in a mainly minimal routing. We propose a method to compute paths for various communications in such a way that traffic congestion is avoided while ensuring deadlock free routing. We also propose an efficient scheme to encode the paths.

We developed a tool in Matlab that computes paths for source routing for both general and application specific communications. Depending upon the type of traffic, this tool computes paths for source routing by selecting best routing algorithm out of many routing algorithms. The tool uses a constructive path improvement algorithm to compute paths that give more uniform link load distribution. It also generates different types of traffics. We also developed a simulator capable of simulating source routing for mesh topology NoC. The experiments and simulations which we performed were successful and the results show that the advantages of source routing especially lower packet latency more than compensate its disadvantages. The results also demonstrate that source routing can be a good routing candidate for practical core based SoCs design using network on chip communication infrastructure.

In the context of the Internet of Things (IoT), commissioning is the process of securely adding a new device to a network. It covers many different tasks, including the physical deployment of devices and configuration of parameters. It is network installers who need to manually commission each device one by one with the help of commissioning tools. In practice, the first task for a network installer is to identify each device correctly before configuring it with proper parameters. Individually identifying each device, especially in a large network, is a very time-consuming process. This is also known as the identification problem. This project is going to address the problem.A novel device identification approach is presented in the thesis, and there is no human intervention involved in the identification process. Devices are trying to identify themselves based on predefined rules and given information. The approach is therefore called device self-identification, and it is implemented in two different algorithms. One is the centralized device selfidentification, and the other is the distributed device self-identification. In short, only one device participates in the device identification process in the centralized approach, and in the distributed counterpart, every device is part of the identification process.The results of the implementations show the potential of the new way to identify devices in IoT. Devices in both the centralized approach and the distributed approach are able to identify themselves given necessary information about the network. A detailed discussion regarding the two proposed algorithms and the network information is presented in the thesis.
I samband med Internet of Things (IoT) är igångkörning processen att säkert lägga till en ny enhet i ett nätverk. Den täcker många olika uppgifter, inklusive fysisk distribution av enheter och konfigurering av parametrar. Det är nätverksinstallatörer som måste manuellt beställa varje enhet en efter en med hjälp av installationsverktyg. I praktiken är den första uppgiften för en nätverksinstallatör att korrekt identifiera varje enhet innan den konfigureras med lämpliga parametrar. Att identifiera varje enhet speciellt i ett stort nätverk är en mycket tidskrävande process. Detta är också känt som identifieringsproblemet. Detta projekt kommer att ta itu med problemet.En nyhetsidentifieringsmetod presenteras i avhandlingen och det finns ingen mänsklig intervention involverad i identifieringsprocessen. Enheter försöker identifiera sig baserat på fördefinierade regler och information. Tillvägagångssättet kallas därför enhetens självidentifiering och det implementeras i två olika algoritmer, en är centraliserad enhetens självidentifiering och den andra är distribuerad enhetens självidentifiering. Kort sagt, endast en enhet deltar i enhetsidentifieringsprocessen i centraliserat tillvägagångssätt, och i distribuerad motsvarighet är varje enhet en del av identifieringsprocessen.Resultaten av implementationerna visar potentialen för det nya sättet att identifiera enheter i IoT. Enheter i både centraliserat tillvägagångssätt och distribuerat tillvägagångssätt kan identifiera sig med den information som krävs för nätverket. En detaljerad diskussion om de två föreslagna algoritmerna och nätverksinformationen presenteras i avhandlingen.

Dans le domaine des réseaux temps réels critiques embarqués, la tendance est à l'augmentation des exigences en termes d'embarquabilité et de bande passante, cela afin de répondre aux nouveaux défis que proposent les véhicules autonomes et les drones. Pour répondre à ces besoins Safran mets en place un nouveau modèle certifiable de réseau distribué à topologie maillée. Cette thèse Cifre prend place au sein de ce projet, afin de proposer un ensemble de méthodes et d'outils permettant de répondre à ces défis et ainsi améliorer les réseaux critiques embarqués. Dans cet objectif, nous présentons un ensemble d'améliorations au nouveau modèle de réseau de Safran en y incorporant la redondance multi-chemins en lieu et place de la redondance multi-plans actuellement d'usage dans l'aéronautique pour satisfaire les contraintes de tolérances aux pannes. Les travaux de la thèse ont également permis l'adoption de plusieurs mesures améliorants les capacités du réseau. D'autre part, les travaux ont également porté sur la mise en place d'une méthode de calcul de borne pessimiste de pire temps de transmission. En effet, la présence de cycles d'interdépendances entre les flux de données au sein de ces réseaux, amène la très grande majorité des méthodes de calcul actuel à ne pas pouvoir converger vers un résultat. Une partie des travaux a donc consisté à produire une adaptation de l'approche trajectoire permettant d'adresser de tel réseau tout en offrant des optimisations afin d'améliorer le passage à l'échelle. La dernière partie des travaux a consisté à mettre en place une méthodologie de production de configuration réseau satisfaisant les contraintes en termes de tolérance aux pannes, de temps de transmission et d'embarquabilité. Cette méthode basée sur un algorithme génétique multicritères permet également d'optimiser la configuration produite en fonction de plusieurs critères afin d'offrir un résultat plus que satisfaisant. Enfin, les travaux présentés dans cette thèse sont validés à l'aide d'un ensemble complet d'expérimentations permettant de conclure à la pertinence des propositions
In the field of embedded real times critical networks, the current trend is to increase requirements in terms of embeddability and bandwidth, in order to meet the new challenges posed by autonomous vehicles and drones. To meet these needs, Safran is establishing a new certifiable model of a distributed network based on a mesh topology. This thesis is taking place within this project, in order to propose a set of methods and tools to meet these needs and thus improve embedded critical networks.With this objective in view, the thesis consisted, firstly, of presenting a range of improvements to Safran's new network model by incorporating multi-path redundancy in place of the multi-plane redundancy currently used in aeronautics to satisfy fault tolerance constraints. The thesis also led to the adoption of several measures to improve others networks capabilities.Secondly, the work also focused on the implementation of a method for calculating a pessimistic worst-case transmission time bound. The presence of cycles of dependencies between data flows within these networks impedes the vast majority of current computation methods to converge on a result. Part of the work has therefore consisted in producing an adaptation of the trajectory approach that can address such networks, while offering optimizations to improve scaling.The final part of the work involved implementing a methodology to produce network configurations that satisfy constraints in terms of fault tolerance, transmission time, and embeddability. This method, which is based on a multi-criteria genetic algorithm, also enables the configuration produced to be optimized as a function of several criteria in order to offer a more than satisfactory result.Finally, the approaches presented in this thesis are tested using a complete set of experiments, allowing us to conclude that it is pertinent

ITC/USA 2010 Conference Proceedings / The Forty-Sixth Annual International Telemetering Conference and Technical Exhibition / October 25-28, 2010 / Town and Country Resort & Convention Center, San Diego, California
The purpose of this paper is to explain the process to implementing a wireless sensor network in order to improve situational awareness in a dense urban environment. Utilizing a system of wireless nodes with Global Positioning System (GPS) and heart rate sensors, a system was created that was able to give both position and general health conditions. By linking the nodes in a mesh network line of sight barriers were overcome to allow for operation even in an environment full of obstruction.

A thesis submitted to the Faculty of Science and Agriculture in fulfilment of the Degree of Doctor of Philosophy in the Department of Computer Science at the University of Zululand, 2017
InfrastructureWireless Mesh Networks (I-WMNs) are increasingly used to provide network connectivity and Internet access to previously under-served areas in the developing world. It is common for some of these deployments to be battery-powered due to a lack of electrical infrastructure in the targeted areas. Thus, the energy-efficiency of these networks gains additional importance. Topology Control (TC) has been previously reported to improve the energy-efficiency and network performance of wireless ad-hoc networks, including I-WMNs. However,simulation-based studies have been relied upon to reach these conclusions and the study of TC prototypes applicable to I-WMNs has largely been limited to design issues. Thus, the study of the efficacy of TC prototypes as a mechanism for improving energy-fficiency and network performance remains an open issue. The thesis addresses this knowledge gap by studying the dynamic, run-time behaviours and the network topologies created by two standards-compatible TC prototypes. This study provides unique insight into how the prototypes consume computational resources, maintain network connectivity, produce cumulative transceiver power savings and affect the workings of the routing protocol being employed. This study also documents the topology instability caused by transceiver power oscillations produced by the PlainTC prototype. A context-based solution to reduce transceiver power oscillations and the subsequent topology instability is proposed. This solution applies the Principal Component Analysis statistical method to historical network data in order to derive the weights associated with each of the identified context variables. A threshold value is defined that only permits a node to adjust its transceiver power output if the observed change in a node’s context exceeds the threshold. The threshold mechanism is incorporated into the PlainTC+ prototype and is shown to reduce topology instability whilst improving network performance when compared to PlainTC.The results obtained in this study suggest that I-WMN topologies formed by TC are able to closely match the performance of networks that do not employ TC. However, this study shows that TC negatively affects the energy efficiency of the network despite achieving cumulative transceiver power savings.

Ad hoc networks are emerging as a cost-effective, yet, powerful tool for communication. These systems, where networks can emerge and converge on-the-fly, are guided by the forward-looking goals of providing ubiquitous connectivity and constant access to information. Due to power and bandwidth constraints, the vulnerability of the wireless medium, and the multi-hop nature of ad hoc networks, these networks are becoming increasingly complex dynamic systems. Besides, modern radios are empowered to be reconfigurable, which harbors the temptation to exploit the system. To understand the implications of these issues, some of which pose significant challenges to efficient network design, we study topology control using game theory. We develop a game-theoretic framework of topology control that broadly captures the radio parameters, one or more of which can be tuned under the purview of topology control. In this dissertation, we consider two parameters, viz. transmit power and channel, and study the impact of controlling these on the emergent topologies. We first examine the impact of node selfishness on the network connectivity and energy efficiency under two levels of selfishness: (a) nodes cooperate and forward packets for one another, but selfishly minimize transmit power levels and; (b) nodes selectively forward packets and selfishly control transmit powers. In the former case, we characterize all the Nash Equilibria of the game and evaluate the energy efficiency of the induced topologies. We develop a better-response-based dynamic that guarantees convergence to the minimal maximum power topology. We extend our analysis to dynamic networks where nodes have limited knowledge about network connectivity, and examine the tradeoff between network performance and the cost of obtaining knowledge. Due to the high cost of maintaining knowledge in networks that are dynamic, mobility actually helps in information-constrained networks. In the latter case, nodes selfishly adapt their transmit powers to minimize their energy consumption, taking into account partial packet forwarding in the network. This work quantifies the energy efficiency gains obtained by cooperation and corroborates the need for incentivizing nodes to forward packets in decentralized, energy-limited networks. We then examine the impact of selfish behavior on spectral efficiency and interference minimization in multi-channel systems. We develop a distributed channel assignment algorithm to minimize the spectral footprint of a network while establishing an interference-free connected network. In spite of selfish channel selections, the network spectrum utilization is shown to be within 12% of the minimum on average. We then extend the analysis to dynamic networks where nodes have incomplete network state knowledge, and quantify the price of ignorance. Under the limitations on the number of available channels and radio interfaces, we analyze the channel assignment game with respect to interference minimization and network connectivity goals. By quantifying the interference in multi-channel networks, we illuminate the interference reduction that can be achieved by utilizing orthogonal channels and by distributing interference over multiple channels. In spite of the non-cooperative behavior of nodes, we observe that the selfish channel selection algorithm achieves load balancing. Distributing the network control to autonomous agents leaves open the possibility that nodes can act selfishly and the overall system is compromised. We advance the need for considering selfish behavior from the outset, during protocol design. To overcome the effects of selfishness, we show that the performance of a non-cooperative network can be enhanced by appropriately incentivizing selfish nodes.
Ph. D.

Thesis (M.S. in Information Technology Management)--Naval Postgraduate School, September 2007.
Thesis Advisor(s): Bordetsky, Alex. "September 2007." Description based on title screen as viewed on Oct. 22, 2007. Includes bibliographical references (p. 93-95). Also available in print.

Doutoramento em Engenharia Electrotécnica
In the modern society, new devices, applications and technologies, with sophisticated capabilities, are converging in the same network infrastructure. Users are also increasingly demanding in personal preferences and expectations, desiring Internet connectivity anytime and everywhere. These aspects have triggered many research efforts, since the current Internet is reaching a breaking point trying to provide enough flexibility for users and profits for operators, while dealing with the complex requirements raised by the recent evolution. Fully aligned with the future Internet research, many solutions have been proposed to enhance the current Internet-based architectures and protocols, in order to become context-aware, that is, to be dynamically adapted to the change of the information characterizing any network entity. In this sense, the presented Thesis proposes a new architecture that allows to create several networks with different characteristics according to their context, on the top of a single Wireless Mesh Network (WMN), which infrastructure and protocols are very flexible and self-adaptable. More specifically, this Thesis models the context of users, which can span from their security, cost and mobility preferences, devices’ capabilities or services’ quality requirements, in order to turn a WMN into a set of logical networks. Each logical network is configured to meet a set of user context needs (for instance, support of high mobility and low security). To implement this user-centric architecture, this Thesis uses the network virtualization, which has often been advocated as a mean to deploy independent network architectures and services towards the future Internet, while allowing a dynamic resource management. This way, network virtualization can allow a flexible and programmable configuration of a WMN, in order to be shared by multiple logical networks (or virtual networks - VNs). Moreover, the high level of isolation introduced by network virtualization can be used to differentiate the protocols and mechanisms of each context-aware VN. This architecture raises several challenges to control and manage the VNs on-demand, in response to user and WMN dynamics. In this context, we target the mechanisms to: (i) discover and select the VN to assign to an user; (ii) create, adapt and remove the VN topologies and routes. We also explore how the rate of variation of the user context requirements can be considered to improve the performance and reduce the complexity of the VN control and management. Finally, due to the scalability limitations of centralized control solutions, we propose a mechanism to distribute the control functionalities along the architectural entities, which can cooperate to control and manage the VNs in a distributed way.
Na sociedade actual, novos dispositivos, aplicações e tecnologias, com capacidades sofisticadas, estão a convergir na mesma infra-estrutura de rede. Os utilizadores são também cada vez mais exigentes nas suas preferências e expectativas pessoais, desejando conetividade `a Internet em qualquer hora e lugar. Estes aspectos têm desencadeado muitos esforços de investigação, dado que a Internet atual está a atingir um ponto de rutura ao tentar promover flexibilidade para os utilizadores e lucros para os operadores, enquanto lida com as exigências complexas associadas `a recente evolução. Em sintonia com a linha de investigação para a Internet do futuro, muitas soluções têm sido propostas para melhorar as arquiteturas e protocolos da Internet atual, de forma a torná-los sensíveis ao contexto, isto é, adaptá-los dinamicamente `a alteração da informação que caracteriza qualquer entidade de rede. Neste sentido, a presente Tese propõe uma nova arquitetura que permite criar várias redes com diferentes características de acordo com o contexto das mesmas, sobre uma única rede em malha sem fios (WMN), cuja infra-estructura e protocolos são muito flexíveis e auto-adaptáveis. Mais especificamente, esta Tese modela o contexto dos utilizadores, que pode abranger as suas preferências de segurança, custo e mobilidade, capacidades dos seus dispositivos ou requisitos de qualidade dos seus serviços, de forma a transformar uma WMN num conjunto de redes lógicas. Cada rede lógica ´e configurada para satisfazer um conjunto de necessidades de contexto do utilizador (como exemplo, suporte de mobilidade elevada e de baixa seguran¸ca). Para implementar esta arquitetura centrada no utilizador, esta Tese utiliza a virtualização de redes, que tem muitas vezes sido defendida como um meio para implementar arquiteturas e serviços de rede de uma forma independente, enquanto permite uma gestão dinâmica dos recursos. Desta forma, a virtualização de redes pode permitir uma configuração flexível e programável de uma WMN, a fim de ser partilhada por várias redes lógicas (ou redes virtuais - VNs). Além disso, o grau de isolamento introduzido pela virtualização de redes pode ser utilizado para diferenciar os protocolos e mecanismos de cada VN baseada em contexto. Esta arquitetura levanta vários desafios para controlar e gerir as VNs em tempo real, e em resposta `a dinâmica dos utilizadores e da WMN. Neste contexto, abordamos os mecanismos para: (i) descobrir e selecionar a VN a atribuir a um utilizador; (ii) criar, adaptar e remover as topologias e rotas das VNs. Também exploramos a possibilidade de considerar a taxa de variação dos requisitos de contexto dos utilizadores de forma a melhorar o desempenho e reduzir a complexidade do controlo e gestão das VNs. Finalmente, devido ´as limitações de escalabilidade das soluções de controlo centralizadas, propomos um mecanismo para distribuir as funcionalidades de controlo ao longo das entidades da arquitectura, que podem cooperar para controlar e gerir as VNs de uma forma distribuída.

Thesis (Ph. D.)--Computing, Georgia Institute of Technology, 2006.
Mihail, Milena, Committee Chair ; Ammar, Mostafa, Committee Member ; Dovrolis, Constantinos, Committee Member ; Faloutsos, Michalis, Committee Member ; Zegura, Ellen, Committee Member.

Approved for public release, distribution is unlimited
The objective of this research is to analyze the network performance and sensor functionality, efficacy and usability of IEEE 802.x wireless MESH networks within a DoD Tactical network environment. Multiple sensor configurations operating with wireless MESH network technologies will be researched and analyzed for performance in expeditionary environment situations. Specifically, this thesis will attempt establish the foundation for the development of wireless MESH "network health" models by examining the performance of sensors operating within a MESH network and define which network performance metrics equate to good quality of service. This research will experiment with different application, sensor, and network configurations of currently available COTS components, such as, voice, video and data hardware. This thesis will lay the groundwork for wireless network MESH predictability, which will enable the optimal use of sensors within a tactical network environment.
Lieutenant Commander, United States Navy

Thesis (M.S. in Information Technology Management)--Naval Postgraduate School, March 2005.
Thesis Advisor(s): Alexander Bordetsky. Includes bibliographical references (p. 49-50). Also available online.

The goal of the thesis is to design the star-based mesh topology by introducing multiple pan-coordinators (hub/switches) under a multipath-fading environment and to improve the data transaction rate of a network which usually gets worst when there is a single pan-coordinator for synchronization of devices in conventional mesh topology; also reduce the hop-count as least as possible. Most of the work has been done on NS-2 network simulator; therefore the research model which has been used here is a simulation model. Altogether 3 simulations have been done. The first scenario is done on a simplest mesh network with a single coordinator and a radio propagation model which has been used is two-ray ground reflection model. The second scenario simulation is similar to the first scenario but in-order to provide multi-path signal fading and highly congested environment the propagation model which has been used this time is shadowing model. The final simulation which has been done is of multiple-star based mesh topology it also uses the similar radio propagation model which has been defined for second scenario. An intensive performance measurement of all the three simulations has been done in terms of transactions made per-second, packet drop rate along with an analysis of packet drop. An hop-count is also measured between star and mesh topology. For multiple star based mesh topology it can be assumed if multiple stars with a routing capability can be used then nodes in a network will be synchronized or re-synchronized with least number of hops in the congested network with a near-by pan-coordinator (hub/switch). One of the major applications of this topology can be automobile manufacturing industry where alot of machines are installed in a congested network and monitoring of every area is mandatory for swift production.

We present tools for a network topology based characterization of heterogeneity in multiagent systems, thereby providing a framework for the analysis and design of heterogeneous multiagent networks from a network structure view-point. In heterogeneous networks, agents with a diverse set of resources coordinate with each other. Coordination among different agents and the structure of the underlying network topology have significant impacts on the overall behavior and functionality of the system. Using constructs from graph theory, a qualitative as well as a quantitative analysis is performed to examine an inter-relationship between the network topology and the distribution of agents with various capabilities in heterogeneous networks. Our goal is to allow agents maximally exploit heterogeneous resources available within the network through local interactions, thus exploring a promise heterogeneous networks hold to accomplish complicated tasks by leveraging upon the assorted capabilities of agents. For a reliable operations of such systems, the issue of security against intrusions and malicious agents is also addressed. We provide a scheme to secure a network against a sequence of intruder attacks through a set of heterogeneous guards. Moreover, robustness of networked systems against noise corruption and structural changes in the underlying network topology is also examined.

Distributed networks, meaning a network in which several agents work together unanimously to perform some task in order to reach goals has become a field with a wide range of applications. One such applications may exist in the form of drones with a purpose of observing and detecting forest fires. In such applications it can be of paramount importance to be able to agree over some opinions or values between the agents. This value could be something such as event detection or a general direction to fly in. However in such a network there might not exist a central hub and it would not be possible for all drones to communicate directly with each other. In order for such a network to be able to reach consensus or agreement, values have to be exchanged between the agents. This thesis focuses on a subset of this problem known as distributed averaging. In the thesis it is investigated how a networks ability to detect forest fires and communicate both efficiently and quickly can change when the number of agents are adjusted in the network. The results showed that, when operating in a fixed area, for a small network of drones the increasing effective energy cost per drone were higher, than that of a larger network. It was also discovered that the speed at which a network could reach an agreement was not necessarily affected by the size of the network. But as the field area being observed was increased, adverse effects were observed in terms of communication and event detection.
Distribuerade nätverk bestående av flera agenter som har som uppgift att tillsammans nå gemensamma resultat har blivit allt mer populärt. Ett sådant användningsområde är hur drönare kan användas för att observera och upptäcka skogsbränder över en given yta. I en sådan tillämpning är det av stor vikt att drönarnätverket kan kommunicera och kongruera över värden nätverket delar med varandra. Dessa värden kan representera händelser som nätverket har som uppgift att upptäcka eller en riktning för drönarna att flyga i. Det är inte alltid garanterat att det finns en central kommunikationscentral för sådana nätverk, utan blir beroende på att kommunicera med varandra för att utbyta och kongruera över värden. Den här rapporten fokuserar på en avgränsad del av det ovanstående problemet som kallas för distribuerat konsensusvärde (eng. distributed averaging). Rapporten undersöker hur ett sådant nätverks konvergeringsförmåga, totala energikostnad samt täckning påverkas när fler drönare tillförs till nätverket. När arbetsytan var satt till statisk storlek visade resultaten att den tillförda energikostnaden per drönare var högre för små nätverk än för större nätverk. Det visades också att hastigheten som nätverket når ett kongruerande värde inte nödvändigtvis påverkas av storleken av nätverket. När arbetsytan ökade i takt med storleken på nätverket observerades däremot motsatt effekt för energikostnad och hastigheten för att nå ett konsensusvärde.

Wireless inter-robot communication enables robot teams to cooperatively solve complex problems that cannot be addressed by a single robot. Applications for cooperative robot teams include search and rescue, exploration and surveillance. Communication is one of the most important components in future autonomous robot systems and is essential for core functions such as inter-robot coordination, neighbour discovery and cooperative control algorithms. In environments where communication infrastructure does not exist, decentralised multi-hop networks can be constructed using only the radios on-board each robot. These are known as wireless mesh networks (WMNs). However existing WMNs have limited capacity to support even small robot teams. There is a need for WMNs where links act like dedicated point-to-point connections such as in wired networks. Addressing this problem requires a fundamentally new approach to WMN construction and this thesis is the first comprehensive study in the multi-robot literature to address these challenges. In this thesis, we propose a new class of communication systems called zero mutual interference (ZMI) networks that are able to emulate the point-to-point properties of a wired network over a WMN implementation. We instantiate the ZMI network using a multi-radio multi-channel architecture that autonomously adapts its topology and channel allocations such that all network edges communicate at the full capacity of the radio hardware. We implement the ZMI network on a 100-radio testbed with up to 20-individual nodes and verify its theoretical properties. Mobile robot experiments also demonstrate these properties are practically achievable. The results are an encouraging indication that the ZMI network approach can facilitate the communication demands of large cooperative robot teams deployed in practical problems such as data pipe-lining, decentralised optimisation, decentralised data fusion and sensor networks.

Thesis (M.S. in Information Technology Management and M.S. in Computer Science)--Naval Postgraduate School, March 2005.
Thesis Advisor(s): Alexander Bordetsky, Gilbert M. Lundy. Includes bibliographical references (p. 69-75). Also available online.

In questo lavoro di tesi verrà presentata l’implementazione di due algoritmi di Deployment e gestione di uno sciame di dispositivi UAV (Unmanned Aerial Vehicles). L’interesse scientifico su cui si fonda quest'analisi ha origine nelle enormi potenzialità degli UAV che garantiscono un'esplorazione aerea di aree pericolose in contesti di emergenze quali ad esempio scenari post catastrofe. La problematica principale affrontata sarà quella della gestione continuativa dell'area disastrata fornendo un algoritmo di schedulazione della cooperazione degli UAV alternando periodi attivi con quelli di ricarica dei dispositivi.

Approved for public release, distribution is unlimited
Wireless mesh mobile ad hoc networks (MANETs) provide the military with the opportunity to spread information superiority to the tactical battlespace in support of network-centric warfare (NCW). These mesh networks provide the tactical networking framework for providing improved situational awareness through ubiquitous sharing of information including remote sensor and targeting data. The Naval Postgraduate School's Tactical Network Topology (TNT) project sponsored by US Special Operations Command seeks to adapt commercial off the shelf (COTS) information technology for use in military operational environments. These TNT experiments rely on a variety of airborne nodes including tethered balloon and UAVs such as the Tern to provide reachback from nodes on the ground to the Tactical Operations Center (TOC) as well as to simulate the information and traffic streams expected from UAVs conducting surveillance missions and fixed persistent sensor nodes. Airborne mesh nodes have unique requirements that can be implemented with COTS technology including single board computers and compact flash.
Lieutenant, United States Navy

Peer-to-peer networks and mobile ad hoc networks are emerging distributed networks that share several similarities. Fundamental among these similarities is the decentralized role of each participating node to route messages on behalf of other nodes, and thereby, collectively realizing communication between any pair of nodes. Messages are routed on a topology graph that is determined by the peer relationship between nodes. Although routing is fairly straightforward when the topology graph is static, dynamic variations in the peer relationship that often occur in peer-to-peer and mobile ad hoc networks present challenges to routing. In this thesis, we examine the interplay between routing messages and network topology design in two classes of these networks -- unstructured peer-to-peer networks and sparsely-connected mobile ad hoc networks. In unstructured peer-to-peer networks, we add structure to overlay topologies to support file sharing. Specifically, we investigate the advantages of designing overlay topologies with small-world properties to improve (a) search protocol performance and (b) network utilization. We show, using simulation, that "small-world-like" overlay topologies where every node has many close neighbors and few random neighbors exhibit high chances of locating files close to the source of file search query. This improvement in search protocol performance is achieved while decreasing the traffic load on the links in the underlying network. In the context of sparsely-connected mobile ad hoc networks where nodes provide connectivity via mobility, we present a protocol for routing in space and time where the message forwarding decision involves not only where to forward (space), but also when to forward (time). We introduce space-time routing tables and develop methods to compute these routing tables for those instances of ad hoc networks where node mobility is predictable over either a finite horizon or indefinitely due to periodicity in node motion. Furthermore, when the node mobility is unpredictable, we investigate several forwarding heuristics to address the scarcity in transmission opportunities in these sparsely-connected ad hoc networks. In particular, we present the advantages of fragmenting messages and augmenting them with erasure codes to improve the end-to-end message delivery performance.

L'informatique en nuage (Cloud Computing) a émergé comme un nouveau paradigme pour offrir des ressources informatiques à la demande et pour externaliser des infrastructures logicielles et matérielles. Le Cloud Computing est rapidement et fondamentalement en train de révolutionner la façon dont les services informatiques sont mis à disposition et gérés. Ces services peuvent être demandés à partir d’un ou plusieurs fournisseurs de Cloud d’où le besoin de la mise en réseau entre les composants des services informatiques distribués dans des emplacements géographiquement répartis. Les utilisateurs du Cloud veulent aussi déployer et instancier facilement leurs ressources entre les différentes plateformes hétérogènes de Cloud Computing. Les fournisseurs de Cloud assurent la mise à disposition des ressources de calcul sous forme des machines virtuelles à leurs utilisateurs. Par contre, ces clients veulent aussi la mise en réseau entre leurs ressources virtuelles. En plus, ils veulent non seulement contrôler et gérer leurs applications, mais aussi contrôler la connectivité réseau et déployer des fonctions et des services de réseaux complexes dans leurs infrastructures virtuelles dédiées. Les besoins des utilisateurs avaient évolué au-delà d'avoir une simple machine virtuelle à l'acquisition de ressources et de services virtuels complexes, flexibles, élastiques et intelligents. L'objectif de cette thèse est de permettre le placement et l’instanciation des ressources complexes dans des infrastructures de Cloud distribués tout en permettant aux utilisateurs le contrôle et la gestion de leurs ressources. En plus, notre objectif est d'assurer la convergence entre les services de cloud et de réseau. Pour atteindre cela, nous proposons des algorithmes de mapping d’infrastructures virtuelles dans les centres de données et dans le réseau tout en respectant les exigences des utilisateurs. Avec l'apparition du Cloud Computing, les réseaux traditionnels sont étendus et renforcés avec des réseaux logiciels reposant sur la virtualisation des ressources et des fonctions réseaux. En plus, le nouveau paradigme d'architecture réseau (Software Defined Networks) est particulièrement pertinent car il vise à offrir la programmation du réseau et à découpler, dans un équipement réseau, la partie plan de données de la partie plan de contrôle. Dans ce contexte, la première partie propose des algorithmes optimaux (exacts) et heuristiques de placement pour trouver le meilleur mapping entre les demandes des utilisateurs et les infrastructures sous-jacentes, tout en respectant les exigences exprimées dans les demandes. Cela inclut des contraintes de localisation permettant de placer une partie des ressources virtuelles dans le même nœud physique. Ces contraintes assurent aussi le placement des ressources dans des nœuds distincts. Les algorithmes proposés assurent le placement simultané des nœuds et des liens virtuels sur l’infrastructure physique. Nous avons proposé aussi un algorithme heuristique afin d’accélérer le temps de résolution et de réduire la complexité du problème. L'approche proposée se base sur la technique de décomposition des graphes et la technique de couplage des graphes bipartis. Dans la troisième partie, nous proposons un cadriciel open source (framework) permettant d’assurer la mise en réseau dynamique entre des ressources Cloud distribués et l’instanciation des fonctions réseau dans l’infrastructure virtuelle de l’utilisateur. Ce cadriciel permettra de déployer et d’activer les composants réseaux afin de mettre en place les demandes des utilisateurs. Cette solution se base sur un gestionnaire des ressources réseaux "Cloud Network Gateway Manager" et des passerelles logicielles permettant d’établir la connectivité dynamique et à la demande entre des ressources cloud et réseau. Le CNG-Manager offre le contrôle de la partie réseau et prend en charge le déploiement des fonctions réseau nécessaires dans l'infrastructure virtuelle des utilisateurs
Cloud computing emerged as a new paradigm for on-demand provisioning of IT resources and for infrastructure externalization and is rapidly and fundamentally revolutionizing the way IT is delivered and managed. The resulting incremental Cloud adoption is fostering to some extent cloud providers cooperation and increasing the needs of tenants and the complexity of their demands. Tenants need to network their distributed and geographically spread cloud resources and services. They also want to easily accomplish their deployments and instantiations across heterogeneous cloud platforms. Traditional cloud providers focus on compute resources provisioning and offer mostly virtual machines to tenants and cloud services consumers who actually expect full-fledged (complete) networking of their virtual and dedicated resources. They not only want to control and manage their applications but also control connectivity to easily deploy complex network functions and services in their dedicated virtual infrastructures. The needs of users are thus growing beyond the simple provisioning of virtual machines to the acquisition of complex, flexible, elastic and intelligent virtual resources and services. The goal of this thesis is to enable the provisioning and instantiation of this type of more complex resources while empowering tenants with control and management capabilities and to enable the convergence of cloud and network services. To reach these goals, the thesis proposes mapping algorithms for optimized in-data center and in-network resources hosting according to the tenants' virtual infrastructures requests. In parallel to the apparition of cloud services, traditional networks are being extended and enhanced with software networks relying on the virtualization of network resources and functions especially through network resources and functions virtualization. Software Defined Networks are especially relevant as they decouple network control and data forwarding and provide the needed network programmability and system and network management capabilities. In such a context, the first part proposes optimal (exact) and heuristic placement algorithms to find the best mapping between the tenants' requests and the hosting infrastructures while respecting the objectives expressed in the demands. This includes localization constraints to place some of the virtual resources and services in the same host and to distribute other resources in distinct hosts. The proposed algorithms achieve simultaneous node (host) and link (connection) mappings. A heuristic algorithm is proposed to address the poor scalability and high complexity of the exact solution(s). The heuristic scales much better and is several orders of magnitude more efficient in terms of convergence time towards near optimal and optimal solutions. This is achieved by reducing complexity of the mapping process using topological patterns to map virtual graph requests to physical graphs representing respectively the tenants' requests and the providers' physical infrastructures. The proposed approach relies on graph decomposition into topology patterns and bipartite graphs matching techniques. The third part propose an open source Cloud Networking framework to achieve cloud and network resources provisioning and instantiation in order to respectively host and activate the tenants' virtual resources and services. This framework enables and facilitates dynamic networking of distributed cloud services and applications. This solution relies on a Cloud Network Gateway Manager and gateways to establish dynamic connectivity between cloud and network resources. The CNG-Manager provides the application networking control and supports the deployment of the needed underlying network functions in the tenant desired infrastructure (or slice since the physical infrastructure is shared by multiple tenants with each tenant receiving a dedicated and isolated portion/share of the physical resources)

The IoT refers to the idea of internetworking physical devices, vehicles, buildings, and any other item embedded with the appropriate electronics, software, sensors, actuators, and network connectivity to allows them to interchange data and to provide highly effective new services. In this thesis we focus on the communications issues of the IoT in relation to mobility and we provide different solutions to alleviate the impact of these potential problems and to guarantee the information delivery in mobile scenarios. Our reference context is a Smart City where various mobile devices collaboratively participate, periodically sending information from their sensors. We assume that these services are located in platforms based in cloud infrastructures where the information is protected through the use of virtualisation ensuring their security and privacy. This thesis is structured into seven chapters. We first detail our objectives and identify the current problems we intend to address. Next, we provide a thorough review of the state of the art of all the areas involved in our work, highlighting how we improved the existing solutions with our research. The overall approach of the solutions we propose in this thesis use prototypes that encompasses and integrates different technologies and standards in a small infrastructure, using real devices in real scenarios with two of the most commonly used networks around the world: WiFi and 802.15.4 to efficiently solve the problems we originally identified. We focussed on protocols based on a producer/consumer paradigm, namely AMQP and particularly MQTT. We observed the behaviour of these protocols using in lab experiments and in external environments, using a mesh wireless network as the backbone network. Various issues raised by mobility were taken into consideration, and thus, we repeated the tests with different messages sizes and different inter-message periodicity, in order to model different possible applications. We also present a model for dimensioning the number of sources for mobile nodes and calculating the number of buffers required in the mobile node as a function of the number of sources and the size of the messages. We included a mechanism for avoiding data loss based on intermediate buffering adapted to the MQTT protocol that, in conjunction with the use of an alternative to the Network Manager in certain contexts, improves the connection establishment for wireless mobile clients. We also performed a detailed study of the jitter behaviour of a mobile node when transmitting messages with this proposal while moving through a real outdoor scenario. To emulate simple IoT networks we used the Cooja simulator to study and determine the effects on the probability of delivering messages when both publishers and subscribers were added to different scenarios. Finally we present an approach that combines the MQTT protocol with DTN which we specifically designed for constrained environments and guarantees that important information will never be lost. The advantage of our proposed solutions is that they make an IoT system more resilient to changes in the point of attachment of the mobile devices in an IoT network without requiring IoT application & service developers to explicitly consider this issue. Moreover, our solutions do not require additional support from the network through protocols such as MobileIP or LISP. We close the thesis by providing some conclusions, and identifying future lines of work which we unable to address here.
Internet de las cosas (IoT) se refiere a la idea de interconectar sensores, actuadores, dispositivos físicos, vehículos, edificios y cualquier elemento dotado de la electrónica, así como del software y de la conectividad de red que los hace capaces de intercambiar datos para proporcionar servicios altamente efectivos. En esta tesis nos centramos en temas relacionados con la comunicación de sistemas IoT, específicamente en situaciones de movilidad y en los problemas que esto conlleva. Con este fin ofrecemos diferentes soluciones que alivian su impacto y garantizan la entrega de información en estas situaciones. El contexto de referencia es una ciudad inteligente donde varios dispositivos móviles participan de forma colaborativa enviando periódicamente información desde sus sensores hacia servicios ubicados en plataformas en la nube (cloud computing) donde mediante el uso de virtualización, la información está protegida garantizando su seguridad y privacidad. Las soluciones propuestas en esta tesis se enfocan en probar sobre una pequeña infraestructura un prototipo que abarca e integra diferentes tecnologías y estándares para resolver eficientemente los problemas previamente identificados. Hemos enfocado nuestro esfuerzo en el uso de dispositivos sobre escenarios reales con dos de las redes más extendidas en todo el mundo: WiFi y enlaces 802.15.4. Nos enfocamos en protocolos que ofrecen el paradigma productor/consumidor como el protocolo avanzado de colas de mensajes (AMQP) y particularmente el protocolo de transporte de mensajes telemétricos (MQTT), observamos su comportamiento a través de experimentos en laboratorio y en pruebas al aire libre, repitiendo las pruebas con diferentes tamaños de mensajes y diferente periodicidad entre mensajes. Para modelar las diferentes posibles aplicaciones de la propuesta, se tomaron en consideración varias cuestiones planteadas por la movilidad, resultando en un modelo para dimensionar eficientemente el número de fuentes para un nodo móvil y para calcular el tamaño requerido del buffer, en función del número de fuentes y del tamaño de los mensajes. Proponemos un mecanismo adaptado al protocolo MQTT que evita la pérdida de datos en clientes móviles, basado en un buffer intermedio entre la producción y publicación de mensajes que, en conjunto con el uso de una alternativa al gestor de conexiones inalámbricas "Network Manager", en ciertos contextos mejora el establecimiento de las conexiones. Para la evaluación de esta propuesta se presenta un estudio detallado de un nodo móvil que se mueve en un escenario real al aire libre, donde estudiamos el comportamiento del jitter y la transmisión de mensajes. Además, hemos utilizado emuladores de redes IoT para estudiar y determinar los efectos sobre la probabilidad de entrega de mensajes, cuando se agregan tanto publicadores como suscriptores a diferentes escenarios. Finalmente, se presenta una solución totalmente orientada a entornos con dispositivos de recursos limitados que combina los protocolos MQTT con redes tolerantes a retardos (DTN) para garantizar la entrega de información. La ventaja de las soluciones que proponemos reside en el hecho de que los sistemas IoT se vuelven resilientes a la movilidad y a los cambios de punto de acceso, permitiendo así que los desarrolladores creen fácilmente aplicaciones y servicios IoT evitando considerar estos problema. Otra ventaja de nuestras soluciones es que no necesitan soporte adicional de la red como sucede con protocolos como MobileIP o el protocolo que separa el identificador del localizador (LISP). Se destaca cómo hemos mejorado las soluciones existentes hasta el momento de la escritura de esta disertación, y se identifican futuras líneas de actuación que no han sido contempladas.
Internet de les coses (IoT) es refereix a la idea d'interconnectar sensors, actuadors, dispositius físics, vehicles, edificis i qualsevol element dotat de l'electrònica, així com del programari i de la connectivitat de xarxa que els fa capaces d'intercanviar dades per proporcionar serveis altament efectius. En aquesta tesi ens centrem en temes relacionats amb la comunicació de sistemes IoT, específicament en situacions de mobilitat i en els problemes que això comporta. A aquest efecte oferim diferents solucions que alleugeren el seu impacte i garanteixen el lliurament d'informació en aquestes situacions. El context de referència és una ciutat intel·ligent on diversos dispositius mòbils participen de forma col·laborativa enviant periòdicament informació des dels seus sensors cap a serveis situats en plataformes en el núvol (cloud computing) on mitjançant l'ús de virtualització, la informació està protegida garantint la seva seguretat i privadesa. Les solucions proposades en aquesta tesi s'enfoquen a provar sobre una xicoteta infraestructura un prototip que abasta i integra diferents tecnologies i estàndards per a resoldre eficientment els problemes prèviament identificats. Hem enfocat el nostre esforç en l'ús de dispositius sobre escenaris reals amb dos de les xarxes més esteses a tot el món: WiFi i enllaços 802.15.4. Ens enfoquem en protocols que ofereixen el paradigma productor/consumidor com el protocol avançat de cues de missatges (AMQP) i particularment el protocol de transport de missatges telemètrics (MQTT), observem el seu comportament a través d'experiments en laboratori i en proves a l'aire lliure, repetint les proves amb diferents grandàries de missatges i diferent periodicitat entre missatges. Per a modelar les diferents possibles aplicacions de la proposta, es van prendre en consideració diverses qüestions plantejades per la mobilitat, resultant en un model per a dimensionar eficientment el nombre de fonts per a un node mòbil i per a calcular la grandària requerida del buffer, en funció del nombre de fonts i de la grandària dels missatges. Proposem un mecanisme adaptat al protocol MQTT que evita la pèrdua de dades per a clients mòbils, basat en un buffer intermedi entre la producció i publicació de missatges que en conjunt amb l'ús d'una alternativa al gestor de connexions sense fils "Network Manager'', en certs contextos millora l'establiment de les connexions. Per a l'avaluació d'aquesta proposta es presenta un estudi detallat d'un node mòbil que es mou en un escenari real a l'aire lliure, on estudiem el comportament del jitter i la transmissió de missatges. A més, hem utilitzat emuladors de xarxes IoT per a estudiar i determinar els efectes sobre la probabilitat de lliurament de missatges, quan s'agreguen tant publicadors com subscriptors a diferents escenaris. Finalment, es presenta una solució totalment orientada a entorns amb dispositius de recursos limitats que combina els protocols MQTT amb xarxes tolerants a retards (DTN) per a garantir el lliurament d'informació. L'avantatge de les solucions que proposem resideix en el fet que els sistemes IoT es tornen resilients a la mobilitat i als canvis de punt d'accés, permetent així que els desenvolupadors creuen fàcilment aplicacions i serveis IoT evitant considerar aquests problema. Un altre avantatge de les nostres solucions és que no necessiten suport addicional de la xarxa com succeeix amb protocols com MobileIP o el protocol que separa l'identificador del localitzador (LISP). Es destaca com hem millorat les solucions existents fins al moment de l'escriptura d'aquesta dissertació, i s'identifican futures línies d'actuació que no han sigut contemplades.
Luzuriaga Quichimbo, JE. (2017). Managing Mobility for Distributed Smart Cities Services [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/84744
TESIS

Denna rapport behandlar prestandaproblem i den nyligen standardiserade Mesh kommunikationsstandarden (IEEE 802.11s). I denna rapport, undersöker och förbättra vi ett förhållande som resulterar i reduktion av genomströmningen i en kedja av noder topologi. IEEE802.11s är mycket lovande med många fördelar för både IoT-systemen och trådlösa nätverk i båda hemmet och arbete.Vi arbetar med frågan om orättvisa när CSMA/CA tillämpas, vilket orsakar genomströmningsreduktion på grund av paketförluster och indikerar svältning. Vi analyserar konsekvenserna av Collision Avoidance (CA) mekanism och föreslår en ersättning för CA som är både rättvist och samtidigt kan upprätthålla undvikande av kollisioner. Vi implementera detta i en simulator och resultatet visar på betydligt högre end-to-end-genomströmning än standard CSMA/CA och inga paketförluster på grund av buffertspill.
This thesis rapport deals with the performance issues of the newly standardized Wireless mesh protocol (IEEE 802.11s). In this thesis, we work on improving the conditions that results in throughput degradation in a chain of nodes topology. The mesh standard is very promising with many advantages for both IoT systems and home wireless networks.We work on the issue of unfairness when CSMA/CA is applied, which causes throughput degradation due to packet loss and indicates starvation. We analyze the implication of the Collision Avoidance (CA) mechanism and propose a replacement for the CA that is both fair and able to maintain collision avoidance. We implement this in a simulator and the result shows significantly higher end-to-end throughput compared to the original CSMA/CA and no packet loss due to buffer overflow.

L'informatique en nuage (Cloud Computing) a émergé comme un nouveau paradigme pour offrir des ressources informatiques à la demande et pour externaliser des infrastructures logicielles et matérielles. Le Cloud Computing est rapidement et fondamentalement en train de révolutionner la façon dont les services informatiques sont mis à disposition et gérés. Ces services peuvent être demandés à partir d’un ou plusieurs fournisseurs de Cloud d’où le besoin de la mise en réseau entre les composants des services informatiques distribués dans des emplacements géographiquement répartis. Les utilisateurs du Cloud veulent aussi déployer et instancier facilement leurs ressources entre les différentes plateformes hétérogènes de Cloud Computing. Les fournisseurs de Cloud assurent la mise à disposition des ressources de calcul sous forme des machines virtuelles à leurs utilisateurs. Par contre, ces clients veulent aussi la mise en réseau entre leurs ressources virtuelles. En plus, ils veulent non seulement contrôler et gérer leurs applications, mais aussi contrôler la connectivité réseau et déployer des fonctions et des services de réseaux complexes dans leurs infrastructures virtuelles dédiées. Les besoins des utilisateurs avaient évolué au-delà d'avoir une simple machine virtuelle à l'acquisition de ressources et de services virtuels complexes, flexibles, élastiques et intelligents. L'objectif de cette thèse est de permettre le placement et l’instanciation des ressources complexes dans des infrastructures de Cloud distribués tout en permettant aux utilisateurs le contrôle et la gestion de leurs ressources. En plus, notre objectif est d'assurer la convergence entre les services de cloud et de réseau. Pour atteindre cela, nous proposons des algorithmes de mapping d’infrastructures virtuelles dans les centres de données et dans le réseau tout en respectant les exigences des utilisateurs. Avec l'apparition du Cloud Computing, les réseaux traditionnels sont étendus et renforcés avec des réseaux logiciels reposant sur la virtualisation des ressources et des fonctions réseaux. En plus, le nouveau paradigme d'architecture réseau (Software Defined Networks) est particulièrement pertinent car il vise à offrir la programmation du réseau et à découpler, dans un équipement réseau, la partie plan de données de la partie plan de contrôle. Dans ce contexte, la première partie propose des algorithmes optimaux (exacts) et heuristiques de placement pour trouver le meilleur mapping entre les demandes des utilisateurs et les infrastructures sous-jacentes, tout en respectant les exigences exprimées dans les demandes. Cela inclut des contraintes de localisation permettant de placer une partie des ressources virtuelles dans le même nœud physique. Ces contraintes assurent aussi le placement des ressources dans des nœuds distincts. Les algorithmes proposés assurent le placement simultané des nœuds et des liens virtuels sur l’infrastructure physique. Nous avons proposé aussi un algorithme heuristique afin d’accélérer le temps de résolution et de réduire la complexité du problème. L'approche proposée se base sur la technique de décomposition des graphes et la technique de couplage des graphes bipartis. Dans la troisième partie, nous proposons un cadriciel open source (framework) permettant d’assurer la mise en réseau dynamique entre des ressources Cloud distribués et l’instanciation des fonctions réseau dans l’infrastructure virtuelle de l’utilisateur. Ce cadriciel permettra de déployer et d’activer les composants réseaux afin de mettre en place les demandes des utilisateurs. Cette solution se base sur un gestionnaire des ressources réseaux "Cloud Network Gateway Manager" et des passerelles logicielles permettant d’établir la connectivité dynamique et à la demande entre des ressources cloud et réseau. Le CNG-Manager offre le contrôle de la partie réseau et prend en charge le déploiement des fonctions réseau nécessaires dans l'infrastructure virtuelle des utilisateurs
Cloud computing emerged as a new paradigm for on-demand provisioning of IT resources and for infrastructure externalization and is rapidly and fundamentally revolutionizing the way IT is delivered and managed. The resulting incremental Cloud adoption is fostering to some extent cloud providers cooperation and increasing the needs of tenants and the complexity of their demands. Tenants need to network their distributed and geographically spread cloud resources and services. They also want to easily accomplish their deployments and instantiations across heterogeneous cloud platforms. Traditional cloud providers focus on compute resources provisioning and offer mostly virtual machines to tenants and cloud services consumers who actually expect full-fledged (complete) networking of their virtual and dedicated resources. They not only want to control and manage their applications but also control connectivity to easily deploy complex network functions and services in their dedicated virtual infrastructures. The needs of users are thus growing beyond the simple provisioning of virtual machines to the acquisition of complex, flexible, elastic and intelligent virtual resources and services. The goal of this thesis is to enable the provisioning and instantiation of this type of more complex resources while empowering tenants with control and management capabilities and to enable the convergence of cloud and network services. To reach these goals, the thesis proposes mapping algorithms for optimized in-data center and in-network resources hosting according to the tenants' virtual infrastructures requests. In parallel to the apparition of cloud services, traditional networks are being extended and enhanced with software networks relying on the virtualization of network resources and functions especially through network resources and functions virtualization. Software Defined Networks are especially relevant as they decouple network control and data forwarding and provide the needed network programmability and system and network management capabilities. In such a context, the first part proposes optimal (exact) and heuristic placement algorithms to find the best mapping between the tenants' requests and the hosting infrastructures while respecting the objectives expressed in the demands. This includes localization constraints to place some of the virtual resources and services in the same host and to distribute other resources in distinct hosts. The proposed algorithms achieve simultaneous node (host) and link (connection) mappings. A heuristic algorithm is proposed to address the poor scalability and high complexity of the exact solution(s). The heuristic scales much better and is several orders of magnitude more efficient in terms of convergence time towards near optimal and optimal solutions. This is achieved by reducing complexity of the mapping process using topological patterns to map virtual graph requests to physical graphs representing respectively the tenants' requests and the providers' physical infrastructures. The proposed approach relies on graph decomposition into topology patterns and bipartite graphs matching techniques. The third part propose an open source Cloud Networking framework to achieve cloud and network resources provisioning and instantiation in order to respectively host and activate the tenants' virtual resources and services. This framework enables and facilitates dynamic networking of distributed cloud services and applications. This solution relies on a Cloud Network Gateway Manager and gateways to establish dynamic connectivity between cloud and network resources. The CNG-Manager provides the application networking control and supports the deployment of the needed underlying network functions in the tenant desired infrastructure (or slice since the physical infrastructure is shared by multiple tenants with each tenant receiving a dedicated and isolated portion/share of the physical resources)

Thesis (M.S. in Operations Research and M.S. in Applied Mathematics)--Naval Postgraduate School, June 2008.
Thesis Advisor(s): Alderson, David ; Zhou, Hong. "June 2008." Description based on title screen as viewed on August 22, 2008. Includes bibliographical references (p. 39-40). Also available in print.

This thesis discuss about the problem with mobility of stations in IP networks, concretely protocol Mobile IP and about the problems with this protocol in MANET networks, with the scope on Motorola MESH. First part is about design integration of protocol Mobile IP in this networks with usage Tropos 5210 MetroMesh routers and Cisco components (router, switch) to design and configure wireless MESH network, than connect this network with Cisco components and try to implement Mobile IP into this network. Second part is about design and configure wireless network from Cisco Wireless Access Points and about succesfully implementation of Mobile IP protocol into this network. In the last part is some tests of the function and quality of this topology.

Les performances du reseau de communication representent la principale limitation des machines paralleles a memoire distribuee. Cette these traite de l'etude et la realisation de reseaux d'interconnexion permettant l'amelioration des performances des communications dans les machines paralleles mimd a passage de messages. Plusieurs architectures sont proposees dans deux cas tres differents. Tout d'abord dans le cas d'une machine cellulaire dont le but est d'offrir une tres grande puissance de calcul en interconnectant un grand nombre de processeurs tres simples. Une premiere solution permet de repousser la limitation technologique que represente le nombre de plots par chip. Deux autres solutions sont utilisees dans le but de reduire la latence des communications distantes par modification de la topologie du reseau. L'evaluation des solutions est faite apres implementation complete du reseau d'interconnexion. Ensuite dans le cas d'une machine parallele formee a partir de stations de travail interconnectees a travers un reseau local utilisant des liens hauts debits (par ex. Atm). Les solutions proposees traitent de l'adaptation de l'atm au calcul parallele. Les points abordes sont la taille des messages, le mode de communication sans connexion, et le controle a l'acces. Un simulateur de reseau a ete developpe pour l'evaluation des solutions proposees. Dans les deux cas, des modeles analytiques sont developpes pour predire la latence du reseau et mieux analyser les resultats experimentaux

Fueled by the rapid advancement in digital and wireless technologies, the ever-increasing capabilities of wireless devices have placed upon us a tremendous challenge - how to put all of this capability to effective use. Individually, wireless devices have outpaced the ability of users to optimally configure them. Collectively, the complexity is far more daunting. Research in cognitive networks seeks to provide a solution to the diffculty of effectively using the expanding capabilities of wireless networks by embedding greater degrees of intelligence within the network itself. In this dissertation, we address some fundamental questions related to cognitive networks, such as "What is a cognitive network?" and "What methods may be used to design a cognitive network?" We relate cognitive networks to a common artificial intelligence (AI) framework, the multi-agent system (MAS). We also discuss the key elements of learning and reasoning, with the ability to learn being the primary differentiator for a cognitive network. Having discussed some of the fundamentals, we proceed to further illustrate the cognitive networking principle by applying it to two problems: multichannel topology control for dynamic spectrum access (DSA) and routing in a mobile ad hoc network (MANET). The multichannel topology control problem involves confguring secondary network parameters to minimize the probability that the secondary network will cause an outage to a primary user in the future. This requires the secondary network to estimate an outage potential map, essentially a spatial map of predicted primary user density, which must be learned using prior observations of spectral occupancy made by secondary nodes. Due to the complexity of the objective function, we provide a suboptimal heuristic and compare its performance against heuristics targeting power-based and interference-based topology control objectives. We also develop a genetic algorithm to provide reference solutions since obtaining optimal solutions is impractical. We show how our approach to this problem qualifies as a cognitive network. In presenting our second application, we address the role of network state observations in cognitive networking. Essentially, we need a way to quantify how much information is needed regarding the state of the network to achieve a desired level of performance. This question is applicable to networking in general, but becomes increasingly important in the cognitive network context because of the potential volume of information that may be desired for decision-making. In this case, the application is routing in MANETs. Current MANET routing protocols are largely adapted from routing algorithms developed for wired networks. Although optimal routing in wired networks is grounded in dynamic programming, the critical assumption, static link costs and states, that enables the use of dynamic programming for wired networks need not apply to MANETs. We present a link-level model of a MANET, which models the network as a stochastically varying graph that possesses the Markov property. We present the Markov decision process as the appropriate framework for computing optimal routing policies for such networks. We then proceed to analyze the relationship between optimal policy and link state information as a function of minimum distance from the forwarding node. The applications that we focus on are quite different, both in their models as well as their objectives. This difference is intentional and signficant because it disassociates the technology, i.e. cognitive networks, from the application of the technology. As a consequence, the versatility of the cognitive networks concept is demonstrated. Simultaneously, we are able to address two open problems and provide useful results, as well as new perspective, on both multichannel topology control and MANET routing. This material is posted here with permission from the IEEE. Such permission of the IEEE does not in any way imply IEEE endorsement of any of Virginia Tech library's products or services. Internal or personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution must be obtained from the IEEE by writing to pubs-permissions@ieee.org. By choosing to view this material, you agree to all provisions of the copyright laws protecting it.
Ph. D.

This thesis is focused on smart buildings where communication and automatization technologies are deployed. It includes overview and description of frequently applied network protocols in smart homes and their side by side comparison with an emphasis on Thread networking protocol. The next chapters describe details and parameters of used development boards provided by NXP Semiconductors and their implementation in a smart home model. Subsequent chapters are focused on hardware and software components which are the basis for smart home model’s internal workings. The last chapter highlights how a physical model of a smart home was developed with suggestions for future improvements.

Les algorithmes distribués de consensus sont des algorithmes itératifs de faible complexité où les nœuds de capteurs voisins interagissent les uns avec les autres pour parvenir à un accord commun sans unité coordinatrice. Comme les nœuds dans un réseau de capteurs sans fil ont une puissance de calcul et une batterie limitées, ces algorithmes distribués doivent parvenir à un consensus en peu de temps et avec peu d’échange de messages. La première partie de cette thèse s’est basée sur l’étude et la comparaison des différents algorithmes de consensus en mode synchrone et asynchrone en termes de vitesse de convergence et taux de communications. La seconde partie de nos travaux concerne l’application de ces algorithmes de consensus au problème de la détection de trous de couverture dans les réseaux de capteurs sans fil.Ce problème de couverture fournit aussi le contexte de la suite de nos travaux. Il se décrit comme étant la façon dont une région d’intérêt est surveillée par des capteurs. Différentes approches géométriques ont été proposées mais elles sont limitées par la nécessité de connaitre exactement la position des capteurs ; or cette information peut ne pas être disponible si les dispositifs de localisation comme par exemple le GPS ne sont pas sur les capteurs. À partir de l’outil mathématique appelé topologie algébrique, nous avons développé un algorithme distribué de détection de trous de couverture qui recherche une fonction harmonique d’un réseau, c’est-à-dire annulant l’opérateur du Laplacien de dimension 1. Cette fonction harmonique est reliée au groupe d’homologie H1 qui recense les trous de couverture. Une fois une fonction harmonique obtenue, la détection des trous se réalise par une simple marche aléatoire dans le réseau
Distributed consensus algorithms are iterative algorithms of low complexity where neighboring sensors interact with each other to reach an agreement without coordinating unit. As the nodes in a wireless sensor network have limited computing power and limited battery, these distributed algorithms must reach a consensus in a short time and with little message exchange. The first part of this thesis is based on the study and comparison of different consensus algorithms synchronously and asynchronously in terms of convergence speed and communication rates. The second part of our work concerns the application of these consensus algorithms to the problem of detecting coverage holes in wireless sensor networks.This coverage problem also provides the context for the continuation of our work. This problem is described as how a region of interest is monitored by sensors. Different geometrical approaches have been proposed but are limited by the need to know exactly the position of the sensors; but this information may not be available if the locating devices such as GPS are not on the sensors. From the mathematical tool called algebraic topology, we have developed a distributed algorithm of coverage hole detection searching a harmonic function of a network, that is to say canceling the operator of the 1-dimensional Laplacian. This harmonic function is connected to the homology group H1 which identifies the coverage holes. Once a harmonic function obtained, detection of the holes is realized by a simple random walk in the network

Commercial provisioning of file synchronization services (FSS) relies entirely on protocols that utilize a remote central server that is often located in the cloud to host important files. Updates at user computers are propagated to the central server and from the central server to other sources in need of such updates. Therefore, a synchronization operation between two computers located on the same network often results in file data transmission to and from this local network at least twice. This introduces an unnecessary bandwidth usage on a user’s local network and has become an issue, especially since there is an increase in the demands for internet resources. This thesis work presents a new file synchronization protocol towards FSS known as LAPSync (location-aware protocol for remote file synchronization). This paper also proposes a hierarchical synchronization mechanism by utilizing LAPSync. Our proposed solution relies on the ability of LAPSync clients to acquire knowledge about the location of clients participating in the synchronization operation to construct a hierarchical synchronization path. Finally, we implement our protocol into a prototype and conduct experiments to compare with drop-box (a popular file synchronization service). The results obtained show that LAPSync offers a reduction in bandwidth usage when the files to be synchronized exist on the same local network

Approved for public release, distribution is unlimited
This thesis analyzes the potential impact of incorporating wireless technologies, specifically an 802.11 mesh layer architecture and 802.16 Orthogonal Frequency Division Multiplexing, in order to effectively and more efficiently transmit data and create a symbiotic operational picture between Coast Guard Cutters, their boarding teams, Coast Guard Operation Centers, and various external agencies. Two distinct collaborative software programs, Groove Virtual Office and the Naval Postgraduate School's Situational Awareness Agent, are utilized over the Tactical Mesh and OFDM network configurations to improve the Common Operating Picture of involved units within a marine environment to evaluate their potential impact for the Coast Guard. This is being done to increase the effectiveness and efficiency of Coast Guard units while they carry out their Law Enforcement and Homeland Security Missions. Through multiple field experiments, including Tactical Network Topology and nuclear component sensing with Lawrence Livermore National Laboratory, we utilize commercial off the shelf (COTS) equipment and software to evaluate their impact on these missions.
Lieutenant Commander, United States Coast Guard
Lieutenant, United States Coast Guard

La deuxième décennie du millénaire actuel peut être résumée en une courte phrase : l'essor des données. Le nombre de sources de données s'est multiplié : du streaming audio-vidéo aux réseaux sociaux et à l'Internet des Objets, en passant par les montres intelligentes, les équipements industriels et les véhicules personnels, pour n'en citer que quelques-unes. Le plus souvent, ces sources forment des réseaux afin d'échanger des informations. En conséquence directe, le domaine du Traitement de Signal sur Graphe a prospéré et a évolué. Son but : traiter et donner un sens à tout le déluge de données environnant. Dans ce contexte, le but principal de cette thèse est de développer des méthodes et des algorithmes capables d'utiliser des flots de données, de manière distribuée, afin d'inférer les réseaux sous-jacents qui relient ces flots. Ensuite, ces topologies de réseau estimées peuvent être utilisées avec des outils développés pour le Traitement de Signal sur Graphe afin de traiter et d'analyser les données supportées par des graphes. Après une brève introduction suivie d'exemples motivants, nous développons et proposons d'abord un algorithme en ligne, distribué et adaptatif pour l'inférence de topologies de graphes pour les flots de données qui sont linéairement dépendants. Une analyse de la méthode s'ensuit, afin d'établir des relations entre les performances et les paramètres nécessaires à l'algorithme. Nous menons ensuite une série d'expériences afin de valider l'analyse et de comparer ses performances avec celles d'une autre méthode proposée dans la littérature. La contribution suivante est un algorithme doté des mêmes capacités en ligne, distribuées et adaptatives, mais adapté à l'inférence de liens entre des données qui interagissent de manière non-linéaire. À ce titre, nous proposons un modèle additif simple mais efficace qui utilise l'usine du noyau reproduisant afin de modéliser lesdites non-linéarités. Les résultats de son analyse sont convaincants, tandis que les expériences menées sur des données biomédicales donnent des réseaux estimés qui présentent un comportement prédit par la littérature médicale. Enfin, une troisième proposition d'algorithme est faite, qui vise à améliorer le modèle non-linéaire en lui permettant d'échapper aux contraintes induites par l'additivité. Ainsi, le nouveau modèle proposé est aussi général que possible, et utilise une manière naturelle et intuitive d'imposer la parcimonie des liens, basée sur le concept de dérivés partiels. Nous analysons également l'algorithme proposé, afin d'établir les conditions de stabilité et les relations entre ses paramètres et ses performances. Une série d'expériences est menée, montrant comment le modèle général est capable de mieux saisir les liens non-linéaires entre les données, tandis que les réseaux estimés se comportent de manière cohérente avec les estimations précédentes
The second decade of the current millennium can be summarized in one short phrase: the advent of data. There has been a surge in the number of data sources: from audio-video streaming, social networks and the Internet of Things, to smartwatches, industrial equipment and personal vehicles, just to name a few. More often than not, these sources form networks in order to exchange information. As a direct consequence, the field of Graph Signal Processing has been thriving and evolving. Its aim: process and make sense of all the surrounding data deluge.In this context, the main goal of this thesis is developing methods and algorithms capable of using data streams, in a distributed fashion, in order to infer the underlying networks that link these streams. Then, these estimated network topologies can be used with tools developed for Graph Signal Processing in order to process and analyze data supported by graphs. After a brief introduction followed by motivating examples, we first develop and propose an online, distributed and adaptive algorithm for graph topology inference for data streams which are linearly dependent. An analysis of the method ensues, in order to establish relations between performance and the input parameters of the algorithm. We then run a set of experiments in order to validate the analysis, as well as compare its performance with that of another proposed method of the literature.The next contribution is in the shape of an algorithm endowed with the same online, distributed and adaptive capacities, but adapted to inferring links between data that interact non-linearly. As such, we propose a simple yet effective additive model which makes use of the reproducing kernel machinery in order to model said nonlinearities. The results if its analysis are convincing, while experiments ran on biomedical data yield estimated networks which exhibit behavior predicted by medical literature.Finally, a third algorithm proposition is made, which aims to improve the nonlinear model by allowing it to escape the constraints induced by additivity. As such, the newly proposed model is as general as possible, and makes use of a natural and intuitive manner of imposing link sparsity, based on the concept of partial derivatives. We analyze this proposed algorithm as well, in order to establish stability conditions and relations between its parameters and its performance. A set of experiments are ran, showcasing how the general model is able to better capture nonlinear links in the data, while the estimated networks behave coherently with previous estimates

碩士
國立交通大學
資訊工程系所
93
This thesis base on the mobility of wireless network, and the restriction of wired network, we combine wireless ad hoc network, wireless mesh network (WMN), and wired network to generate a new architecture. This thesis solve the problem of wireless devices signals decay with the distance, and provide a secure authentication way. We use fixed node of WMN to help other movable nodes exchange information with AAA servers to do authentication, authorization, and accounting. In order to save the packet transferring on wireless network, we distributed AAA servers on WMN. Using (n,k) threshold secret sharing to do separate private key, and proactive secret sharing to update it. Moreover, this may avoid being attack. After mobile nodes authenticated, AAA servers issue a short-lived certificate for it to access services or communicate with other mobile nodes. Finally, we compare the advantage and disadvantage with distributed and centralized AAA server on WMN.

碩士
國立政治大學
資訊科學學系
96
In wireless mesh networks, such as WLAN (IEEE 802.11s), WMAN (IEEE 802.16), etc., each node should forward packets of neighboring nodes toward gateway using multi-hop routing mechanism. In wireless mesh network, as the density of network nodes increases, the RF interference will increase and the throughput of each node will drop rapidly. In our research, we use the geometry to resolve the RF interference problem by rebuilding network topology. We try to minimize the interference between neighboring nodes and improve the throughput in wireless mesh network. We transform the network topology problem into geometry problem and define the line intersection problem in geometric graph, then check path intersection in the geometric graph. If line intersection occurs in the graph, we remove the intersection line from the graph and re-plan the region by triangulation algorithm. When the network topology is built up, we use a standard deviation formula to improve network performance by removing longer links. The line intersection algorithm and triangulation algorithm, both of time complexity O(n log n), are used to find the minimal interference solution. At the end of our research, we use network simulator to verify if the proposed methods can help to meet all those performance expectations.

碩士
中興大學
電機工程學系所
95
This thesis presents a decentralized clustering and gateway selection algorithm for wireless ad-hoc sensor networks. Each sensor uses a random waiting timer and local criteria to determine whether to form a new cluster or to join a current cluster and utilizes the messages transmitted during hierarchical clustering to choose distributed gateways such that communication for adjacent clusters and adaptive distributed topology control can be achieved. The algorithm operates without a centralized controller, it operates asynchronously, and does not require that the location of the sensors be known a priori. A performance analysis of the topology management and the energy requirements of the algorithm are used to study the behaviors of the proposed algorithm. The performance of the algorithm is described analytically and via simulation.

Nowadays, every electronic system, ranging from a small mobile phone to a satellite sent into space, has a System-on-Chip (SoC). Over the years, SoCs have undergone rapid evolution and are still progressing at a swift pace. But, due to this explosive evolution of semiconductor industry, the devices are scaling down at a rapid rate and hence, the SoCs today have become communication-centric. However, the existing bus architectures comprising of wires for global interconnection in SoC Designs are undergoing a design crisis as they are not able to keep up with the rate of scaling down of devices. In response to this crisis,Network-on-Chip (NoC) is an upcoming archetype, and is becoming a leading contender to replace the conventional bus architectures. Many Network-on-Chip topologies have been introduced in an attempt to tackle various chip architecture needs and routing techniques. A network simulator NS2 has been utilized in an attempt to simulate the functioning of some of the topologies like Mesh, Binary Tree, Torus and Butterfly Fat Tree (BFT). Their performances in various traffic scenarios has been assessed and compared taking throughput, maximum end-to-end latency and dropping probability as parameters. It can be inferred from simulation results that with respect to throughput and dropping probability, Torus topology has an upper hand over the others whereas BFT topology provides lower latency as compared to others. The Mesh topology is well-suited for incorporating regular-sized processing elements on a single chip. It is also quite simpler to design and incorporate various routing protocols into it as opposed to others. Thus, to validate the functioning of NoC on hardware, 4×4 Mesh architecture has been designed in VHDL and the same has been synthesized for Virtex II Pro FPGA.

碩士
國立臺灣大學
資訊工程學研究所
99
In IEEE 802.11, channel resources are very limited and scarce. Thus channel assignment schemes which can effectively utilize available channels is one of the important issues in multi-channel wireless mesh networks. There are two approaches for channel assignment: centralized and distributed. We focus on distributed channel assignment, i.e., each node chooses its channel based on local information. The advantages of distributed approach are better flexibility and fault-tolerance. However, the problem of distributed channel assignment is channel oscillation which results that the channel assignment cannot converge for a long time and nodes change its channel repeatedly, and therefore the network throughput is throttled. In this thesis, we propose a new distributed channel assignment scheme to solve the channel oscillation problem, and to maximize the network throughput. Performance evaluation shows that our proposed algorithm improves the throughput and end-to-end delay in comparison to previously proposed distributed channel assignment schemes.

碩士
國立中興大學
電機工程學系所
96
Wireless sensor network is a wireless network consisting autonomous devices using sensor which equipped with a radio transceiver. In general, wireless environment is vulnerable for many kinds of security. Therefore, a secure wireless transmission attack is obviously very important. A clustering-based secure communication protocol is proposed to resolve this problem. There are three phases in the protocol. In the first phase, the sensor in the network is needed to be verified their identifications during forming clustering topology construction. In the second phase, sensors need to manage their communication keys of intra-cluster and inter-cluster. In the third phase, sensors are required to renew keys periodically. Then we show the secure protocol can form a security agreement and can effectively protect network from attack. When the sensor network encounters a spam attack, it forms quarantined regions by using clustering mode. Authentication is needed if message pass through a quarantined region. Or the message can select a different route by passing the quarantined region. Simulation result shows that using authentication in quarantined regions is cost effective.

碩士
國立臺灣科技大學
電機工程系
98
IEEE 802.16 standard defines an election-based transmission timing(EBTT) scheme for coordinated distributed mesh network which can guarantee a collision-free environment for control subframe. And it use three-way handshaking mechanism for data scheduling. But three-way handshake mechanism has some problems such as the nodes which are two-hop neighbors cannot receive the schedule information. It causes the primary interference(PI) or the secondary interference(SI). The minislot utilization will be decreased. In order to solve the above-mentioned problems, we proposed a pre-decided distributed scheduling scheme(PDS). And we also proposed a two-way handshake mechanism that is suitable for PDS. Finally, we proposed a mechanism to relay the schedule information. Let the nodes which are two-hop neighbors can receive the schedule information. After combining these three schemes, we can ensure to avoid PI and SI to achieve high minislot utilization. We compare our scheme and the IEEE 802.16 standard. The simulation results show our scheme improve the node throughput significantly. The average packet delay and fairness also better than IEEE 802.16 standard.

博士
國立交通大學
資訊科學與工程研究所
98
The Wireless Mesh Network (WMN) is a cost-effective solution for backbone networks in both metropolitan and rural areas and can be used as temporary broadband access for emergent and tactic purposes. Without the need of wires, WMNs are easy to deploy and reconstruct to satisfy the dynamic needs. The IEEE 802.16 mesh CDS-mode network is a candidate of next-generation WMNs, which provides the “collision-free” property unique to traditional IEEE 802.11 based WMNs. In this dissertation, we propose several schemes for this new network to enhance its scheduling efficiency on the control plane and its QoS support on the data plane. In addition, we also point out the issues of network initialization of this network on random topologies and propose a scheme to solve these issues. The performances of our proposed schemes are evaluated using both analyses and simulations. Our analytical and numerical results show that our proposed schemes can significantly enhance the performance of the IEEE 802.16 mesh CDS-mode network and benefits upper-layer applications.

碩士
國立臺灣科技大學
電機工程系
96
In IEEE 802.16 mesh network, the transmission signaling and data scheduling method significantly affect the performance and capacity of the system. This paper propose a physical layer uses OFDMA-TDMA in the data subframe to improve data scheduling flexibility and spectrum efficiency. Because local nodes don’t know the exact scheduling information of 2-hop neighbors, the grant messages sent back by the receiver have the chance to collide with other’s decision, known as request invalid, and thus decreases throughput and increase access delay. Therefore, this paper provide an unique slot selection mechanism, known as hash selection scheme (HSS), to against the issue by allowing the node in the network to schedule data with a shifting basis. We compare three different slot selection mechanism, which include normal, random and HSS, on both primary interference scenario (PIS) and secondary interference scenario (SIS) with different topologies. Simulation results show that HSS is 35% better in throughput than others and reduces the request invalid ratio to 0.05% in the relative low loading system. In the relative heavy loading system, HSS is only 10% better in throughput than others and the request invalid ratio reach to 27%. In the full loading system, HSS improve the throughput anymore, and request invalid ratio is the same as others.

Thesis (Ph.D.)--State University of New York at Buffalo, 2006.
Title from PDF title page (viewed on July. 21, 2006) Available through UMI ProQuest Digital Dissertations. Thesis adviser: Batta, Rajan, Nagi, Rakesh. Includes bibliographical references.

We address several problems that arise in a multihop wireless mesh network. First, we study the problem of joint congestion control, routing and MAC layer scheduling. We formulate the problem as an aggregate utility maximization problem and apply duality theory to decompose the problem into two sub-problems, namely, network layer congestion control and routing problem, and MAC layer scheduling problem. Given the link “prices", the source adjusts its rate based on the cost of the least-cost path to the destination, and sends traffic to the destination along the least-cost path, while link scheduling is carried out based on link prices. Optimal link scheduling for a wireless network is known to be NP-hard. We explore the use of a known centralized greedy heuristic, and develop a distributed algorithm that can schedule independent links based on local information. While the link scheduling algorithm above is for a given set of link prices, the solution to our problem depends on the sequence of price vectors generated by the price update algorithm. This leads us to study convergence issues related to the price update algorithm. Next, we develop a practical protocol which maximizes aggregate utility in a wireless mesh network. We simulate our protocol using Qualnet 4.5 and compare the result with a baseline protocol that uses IEEE 802.11 for link scheduling and AODV for routing. Our proposed protocol requires the durations of slots and subslots to be defined. We develop an approach in which given a single cell wireless mesh network using IEEE 802.11 as a reliable message delivery mechanism, one can find upper and lower bounds on the durations of slots. We employ stochastic ordering to compare distributions of random variables and using some properties of stochastic ordering along with the central limit theorem, we devise a way to compute the above mentioned bounds on the durations. In the second part, we shift our focus to model delays incurred by application packets sent over a WLAN. In this section we model the WLAN as a Random Polling System. The packet arrival process at each node i is assumed to be a stationary and independent increment random process with mean ai and second moment a(2)i . The packet lengths at node i are assumed to be i.i.d random variables Pi with finite mean and second moment. Utilizing available results, we obtain expressions for mean packet delay. Extensive simulations are conducted to verify the analytical results.