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Tesi sul tema "Networks"
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1
Rivas, Antonio Canales. "Network management using active networks". Thesis, De Montfort University, 2006. http://hdl.handle.net/2086/4781.
Testo completo
2
Wells, Daniel David. "Network management for community networks". Thesis, Rhodes University, 2010. http://hdl.handle.net/10962/d1006587.
Testo completoAbstract (sommario):
Community networks (in South Africa and Africa) are often serviced by limited bandwidth network backhauls. Relative to the basic needs of the community, this is an expensive ongoing concern. In many cases the Internet connection is shared among multiple sites. Community networks may also have a lack of technical personnel to maintain a network of this nature. Hence, there is a demand for a system which will monitor and manage bandwidth use, as well as network use. The proposed solution for community networks and the focus within this dissertation, is a system of two parts. A Community Access Point (CAP) is located at each site within the community network. This provides the hosts and servers at that site with access to services on the community network and the Internet, it is the site's router. The CAP provides a web based interface (CAPgui) which allows configuration of the device and viewing of simple monitoring statistics. The Access Concentrator (AC) is the default router for the CAPs and the gateway to the Internet. It provides authenticated and encrypted communication between the network sites. The AC performs several monitoring functions, both for the individual sites and for the upstream Internet connection. The AC provides a means for centrally managing and effectively allocating Internet bandwidth by using the web based interface (ACgui). Bandwidth use can be allocated per user, per host and per site. The system is maintainable, extendable and customisable for different network architectures. The system was deployed successfully to two community networks. The Centre of Excellence (CoE) testbed network is a peri-urban network deployment whereas the Siyakhula Living Lab (SLL) network is a rural deployment. The results gathered conclude that the project was successful as the deployed system is more robust and more manageable than the previous systems.
3
Gaddam, Nishanth. "Network coding in wireless networks". [Ames, Iowa : Iowa State University], 2009. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1468982.
Testo completo
4
Jiang, Shu. "Efficient network camouflaging in wireless networks". Texas A&M University, 2005. http://hdl.handle.net/1969.1/3067.
Testo completoAbstract (sommario):
Camouflaging is about making something invisible or less visible. Network
camouflaging is about hiding certain traffic information (e.g. traffic pattern, traffic
flow identity, etc.) from internal and external eavesdroppers such that important
information cannot be deduced from it for malicious use. It is one of the most challenging
security requirements to meet in computer networks. Existing camouflaging
techniques such as traffic padding, MIX-net, etc., incur significant performance degradation
when protected networks are wireless networks, such as sensor networks and
mobile ad hoc networks. The reason is that wireless networks are typically subject to
resource constraints (e.g. bandwidth, power supply) and possess some unique characteristics
(e.g. broadcast, node mobility) that traditional wired networks do not
possess. This necessitates developing new techniques that take account of properties
of wireless networks and are able to achieve a good balance between performance and
security.
In this three-part dissertation we investigate techniques for providing network
camouflaging services in wireless networks. In the first part, we address a specific
problem in a hierarchical multi-task sensor network, i.e. hiding the links between
observable traffic patterns and user interests. To solve the problem, a temporally constant traffic pattern, called cover traffic pattern, is needed. We describe two traf-
fic padding schemes that implement the cover traffic pattern and provide algorithms
for achieving the optimal energy efficiencies with each scheme. In the second part,
we explore the design of a MIX-net based anonymity system in mobile ad hoc networks.
The objective is to hide the source-destination relationship with respect to
each connection. We survey existing MIX route determination algorithms that do
not account for dynamic network topology changes, which may result in high packet
loss rate and large packet latency. We then introduce adaptive algorithms to overcome
this problem. In the third part, we explore the notion of providing anonymity
support at MAC layer in wireless networks, which employs the broadcast property
of wireless transmission. We design an IEEE 802.11-compliant MAC protocol that
provides receiver anonymity for unicast frames and offers better reliability than pure
broadcast protocol.
5
Bhatia, Anuj. "Voice network for aviation data networks". Thesis, Wichita State University, 2007. http://hdl.handle.net/10057/1500.
Testo completoAbstract (sommario):
Airline companies are always looking for various services they can offer to differentiate them from others and increase there market share. On the other hand passengers in the aircraft always want to be in touch with the rest of the world through phone or internet to make there time more productive. The drive of gaining market share by airline companies and advances in wireless and internet technology has made voice communication possible from the aircraft. Present technologies offer cell phone access or allow voice communication over internet through satellite link. The major disadvantage they pose is the interference of cell phone transmission with navigational system of aircraft and the cost of implementation. Present research work attempts to address the above problem by designing an IP based network which is capable of connecting travelers from aircraft to the rest of the world.Thesis (M.S)-- Wichita State University, College of Engineering, Dept. of Electrical and Computer Engineering
"July 2007."
6
Somalingam, Ramesh Ramvel. "Network performance monitoring for multimedia networks". Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=23939.
Testo completoAbstract (sommario):
Multimedia applications require certain guarantees from the underlying system concerning quality of various parameters, such as the throughput, delay, loss rate etc. We assume that such quality of service (QoS) parameters are normally agreed upon for the duration of a session, and should be maintained throughout that session. If a QoS violation occurs, possibly due to the temporary overload of one of the system components, either the user will notice this and may request a renegotiation of the quality and cost parameters, or the system will automatically do some internal reconfiguration in order to recover from the problem. In the latter case, the system needs to continuously monitor the relevant performance parameters. In this thesis, we develop means for performing such monitoring in the context of a News-on-Demand application. We have designed and implemented a distributed QoS monitoring facility that can be used by distributed multimedia applications for QoS monitoring and QoS violation detection. The system consists of a measurement component and an administrative component. The measurement component is responsible for continuously measuring the end-to-end QoS parameters of connections between the server and client application, while the administrative component is responsible for the overall administration of the monitoring system, which includes raising QoS violation notifications if the quality of service is violated.
7
Alkhawlani, Mohammed Mohssen. "Access network selection in heterogeneous networks". Thesis, De Montfort University, 2008. http://hdl.handle.net/2086/5217.
Testo completoAbstract (sommario):
The future Heterogeneous Wireless Network (HWN) is composed of multiple Radio Access Technologies (RATs), therefore new Radio Resource Management (RRM) schemes and mechanisms are necessary to benefit from the individual characteristics of each RAT and to exploit the gain resulting from jointly considering the whole set of the available radio resources in each RAT. These new RRM schemes have to support mobile users who can access more than one RAT alternatively or simultaneously using a multi-mode terminal. An important RRM consideration for overall HWN stability, resource utilization, user satisfaction, and Quality of Service (QoS) provisioning is the selection of the most optimal and promising Access Network (AN) for a new service request. The RRM mechanism that is responsible for selecting the most optimal and promising AN for a new service request in the HWN is called the initial Access Network Selection (ANS). This thesis explores the issue of ANS in the HWN. Several ANS solutions that attempt to increase the user satisfaction, the operator benefits, and the QoS are designed, implemented, and evaluated. The thesis first presents a comprehensive foundation for the initial ANS in the H\VN. Then, the thesis analyses and develops a generic framework for solving the ANS problem and any other similar optimized selection problem. The advantages and strengths of the developed framework are discussed. Combined Fuzzy Logic (FL), Multiple Criteria Decision Making (MCDM) and Genetic Algorithms (GA) are used to give the developed framework the required scalability, flexibility, and simplicity. The developed framework is used to present and design several novel ANS algorithms that consider the user, the operator, and the QoS view points. Different numbers of RATs, MCDM tools, and FL inference system types are used in each algorithm. A suitable simulation models over the HWN with a new set of performance evolution metrics for the ANS solution are designed and implemented. The simulation results show that the new algorithms have better and more robust performance over the random, the service type, and the terminal speed based selection algorithms that are used as reference algorithms. Our novel algorithms outperform the reference algorithms in- terms of the percentage of the satisfied users who are assigned to the network of their preferences and the percentage of the users who are assigned to networks with stronger signal strength. The new algorithms maximize the operator benefits by saving the high cost network resources and utilizing the usage of the low cost network resources. Usually better results are achieved by assigning the weights using the GA optional component in the implemented algorithms.
8
Jannotti, John 1974. "Network layer support for overlay networks". Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/29274.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2002.Includes bibliographical references (p. 98-103).
Overlay networks are virtual networks formed by cooperating nodes that share an underlying physical network. They represent a flexible and deployable approach for applications to obtain new network semantics without modification of the underlying network, but they suffer from efficiency concerns. This thesis presents two new primitives for implementation in the network layer (i.e., the routers of the physical network). These primitives support the efficient operation and construction of overlay networks. Packet Reflection allows end hosts to request that routers perform specialized routing and duplication for certain packets. Path Painting allows multiple end hosts to determine where their disparate paths to a rendezvous point meet, in order to facilitate overlay topology building that reflects the topology of the underlying network. Both primitives can be incrementally deployed for incremental benefit. This thesis describes a variety applications of these primitives: application level multicast systems with various semantics, an extended Internet Indirect Infrastructure with latency benefits over the original proposal, and an extension to Chord which would allows faster lookups. Experimental results on simulated topologies indicate that when all routers support the proposed primitives, less that 5% overhead (in terms of link usage and latency) remains in two common overlay network usage scenarios. In addition, the benefits gained from deployment are significant even at low deployment levels. At approximately 25% deployment, the primitives have reduced overhead by over 50%. When intelligent deployment strategies are used, link usage overhead is less than 30% at less than 10% deployment. Finally, the results indicate that these benefits affect the area local to the deployed routers, providing a deployment incentive to independent networks.
by John Jannotti.
Ph.D.
9
Kim, MinJi Ph D. Massachusetts Institute of Technology. "Network coding for robust wireless networks". Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/71276.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2012.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student submitted PDF version of thesis.
Includes bibliographical references (p. 157-167).
Wireless networks and communications promise to allow improved access to services and information, ubiquitous connectivity, and mobility. However, current wireless networks are not well-equipped to meet the high bandwidth and strict delay requirements of future applications. Wireless networks suffer from frequent losses and low throughput. We aim to provide designs for robust wireless networks. This dissertation presents protocols and algorithms that significantly improve wireless network performance and effectively overcome interference, erasures, and attacks. The key idea behind this dissertation is in understanding that wireless networks are fundamentally different from wired networks, and recognizing that directly applying techniques from wired networks to wireless networks limits performance. The key ingredient underlying our algorithms and protocols is network coding. By recognizing the algebraic nature of information, network coding breaks the convention of routing networks, and allows mixing of information in the intermediate nodes and routers. This mixing has been shown to have numerous performance benefits, e.g. increase in throughput and robustness against losses and failures. We present three protocols and algorithms, each using network coding to harness a different characteristic of the wireless medium. We address the problem of interference, erasures, and attacks in wireless networks with the following network coded designs. -- Algebraic NC exploits strategic interference to provide a distributed, randomized code construction for multi-user wireless networks. Network coding framework simplifies the multi-user wireless network model, and allows us to describe the multi-user wireless networks in an algebraic framework. This algebraic framework provides a randomized, distributed code construction, which we show achieves capacity for multicast connections as well as a certain set of non-multicast connections. -- TCP/NC efficiently and reliably delivers data over unreliable lossy wireless networks. TCP, which was designed for reliable transmission over wired networks, often experiences severe performance degradation in wireless networks. TCP/NC combines network coding's erasure correction capabilities with TCP's congestion control mechanism and reliability. We show that TCP/NC achieves significantly higher throughput than TCP in lossy networks; therefore, TCP/NC is well suited for reliable communication in lossy wireless networks. -- Algebraic Watchdog takes advantage of the broadcast nature of wireless networks to provide a secure global self-checking network. Algebraic Watchdog allows nodes to detect malicious behaviors probabilistically, and police their neighbors locally using overheard messages. Unlike traditional detection protocols which are receiver-based, this protocol gives the senders an active role in checking the nodes downstream. We provide a trellis-based inference algorithm and protocol for detection, and analyze its performance. The main contribution of this dissertation is in providing algorithms and designs for robust wireless networks using network coding. We present how network coding can be applied to overcome the challenges of operating in wireless networks. We present both analytical and simulation results to support that network coded designs, if designed with care, can bring forth significant gains, not only in terms of throughput but also in terms of reliability, security, and robustness.
by MinJi Kim.
Ph.D.
10
Attar, Hani Hasan. "Cooperative Network Coding for wireless networks". Thesis, University of Strathclyde, 2011. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=16782.
Testo completo
11
Otten, Fred. "Network simulation for professional audio networks". Thesis, Rhodes University, 2015. http://hdl.handle.net/10962/d1017935.
Testo completoAbstract (sommario):
Audio Engineers are required to design and deploy large multi-channel sound systems which meet a set of requirements and use networking technologies such as Firewire and Ethernet AVB. Bandwidth utilisation and parameter groupings are among the factors which need to be considered in these designs. An implementation of an extensible, generic simulation framework would allow audio engineers to easily compare protocols and networking technologies and get near real time responses with regards to bandwidth utilisation. Our hypothesis is that an application-level capability can be developed which uses a network simulation framework to enable this process and enhances the audio engineer’s experience of designing and configuring a network. This thesis presents a new, extensible simulation framework which can be utilised to simulate professional audio networks. This framework is utilised to develop an application - AudioNetSim - based on the requirements of an audio engineer. The thesis describes the AudioNetSim models and implementations for Ethernet AVB, Firewire and the AES- 64 control protocol. AudioNetSim enables bandwidth usage determination for any network configuration and connection scenario and is used to compare Firewire and Ethernet AVB bandwidth utilisation. It also applies graph theory to the circular join problem and provides a solution to detect circular joins.
12
Bhatia, Anuj Pendse Ravindra. "Voice network for aviation data networks /". Thesis, A link to full text of this thesis in SOAR, 2007. http://hdl.handle.net/10057/1500.
Testo completo
13
Patterson, Raymond A. "Hybrid Neural networks and network design". Connect to resource, 1995. http://rave.ohiolink.edu/etdc/view.cgi?acc%5Fnum=osu1262707683.
Testo completo
14
Alfred, Asterjadhi. "Network Coding for Cognitive Radio Networks". Doctoral thesis, Università degli studi di Padova, 2011. http://hdl.handle.net/11577/3422021.
Testo completoAbstract (sommario):
Cognitive Radio Networks are a promising technology likely to be deployed in the very near future as a viable solution to the spectrum shortage problems faced by traditional wireless systems. Technological breakthroughs in the field of Software Defined Radios enabled the development of flexible cognitive radio transceivers capable of dynamically changing their transmission parameters in order to efficiently exploit the available wireless resources. This increased capability of cognitive radios to self adapt based on interactions with the surrounding environment makes them the perfect candidates for opportunistic spectrum access in those bands that are assigned to primary users. While these primary users are allowed to access their licensed spectrum resources anytime and anywhere, within the contractual limits imposed by spectrum management authorities, cognitive radios have to scan and identify any unused spectrum in the licensed bands. Most importantly, in order not to interfere with primary users, they have to rapidly vacate the licensed spectrum as soon as the primary user begins to use its legitimate spectrum resources.
The coexistence of cognitive radios with such primary users is very challenging. When considering the natural evolution of cognitive radio networks to more complex systems, the challenges and problems to be faced increase substantially. More specifically, the inherent capability of cognitive radios to base their decisions on their view of the wireless spectrum makes their operation susceptible to a variety of malicious attacks. Hence, in such a challenging environment, mechanisms such as cooperation, learning, and negotiation help cognitive radios make the necessary decisions to ensure reliable communications in a non-interfering manner.
We hereby investigate a novel architectural solution for Cognitive Radio Networks that uses network coding for fast control information exchange among cognitive radios, enabling them to maintain coherent and reliable information regarding the status of the wireless environment. This control information is used by cognitive radios to perform cooperative detection of primary users and efficient reuse of the available spectrum resources while guaranteeing robust communication and a prompt reaction to wireless environmental changes.Le Reti Radio Cognitive sono una tecnologia promettente che potrà essere utilizzata in un futuro molto prossimo, come soluzione possibile al problema di spettro limitato riscontrato nelle reti wireless tradizionali. Le recenti innovazioni tecnologiche su Software Defined Radio hanno permesso lo sviluppo di ricetrasmettitori radio sufficientemente flessibili, in grado di modificare dinamicamente i loro parametri di trasmissione, al fine di sfruttare in modo efficiente le risorse radio disponibili. Questa maggiore capacita di auto-adattarsi in risposta alle interazioni con l'ambiente circostante rende le radio cognitive i candidati ideali per l'accesso opportunistico nelle bande dello spettro radio utilizzate dagli utenti primari. Poiché gli utenti primari hanno diritto ad accedere alle proprie risorse dello spettro in qualsiasi momento e luogo, entro i limiti contrattuali imposti dalle autorità di gestione dello spettro radio, le radio cognitive devono effettuare la scansione e identificare le porzioni dello spettro non utilizzate dagli utenti primari. Inoltre, al fine di non interferire con tali utenti, esse devono liberare rapidamente lo spettro radio, ogniqualvolta l'utente primario inizi ad utilizzare la propria banda di frequenze. La coesistenza tra radio cognitive e utenti primari e' un obiettivo molto ambizioso. Inoltre, quando si considera la normale evoluzione delle reti radio cognitive a sistemi più complessi, le sfide e i problemi da affrontare aumentano notevolmente. In particolare, la capacita intrinseca delle radio cognitive di basare le proprie decisioni sulla propria visione locale dello spettro radio rende il loro funzionamento sensibile a molte tipologie di attacco. Quindi, in tale ambiente, meccanismi come la cooperazione, l'apprendimento e la negoziazione sono di aiuto alle radio cognitive nel prendere le decisioni necessarie a garantire le proprie comunicazioni senza interferire con quelle degli utenti primari. In questa tesi si presenta un'architettura innovativa per le Reti Radio Cognitive che utilizza la tecnica di network coding per lo scambio di informazioni di controllo tra i nodi, riguardo lo stato dell'ambiente radio, in modo rapido, coerente e affidabile. Questa informazione viene successivamente utilizzata dalle radio cognitive per eseguire il rilevamento cooperativo degli utenti primari e il riutilizzo efficiente dello spettro a disposizione, garantendo una comunicazione robusta e una reazione tempestiva ai cambiamenti dello stato delle risorse radio.
15
Suárez-Varela, Macià José Rafael. "Enabling knowledge-defined networks : deep reinforcement learning, graph neural networks and network analytics". Doctoral thesis, Universitat Politècnica de Catalunya, 2020. http://hdl.handle.net/10803/669212.
Testo completoAbstract (sommario):
Significant breakthroughs in the last decade in the Machine Learning (ML) field have ushered in a new era of Artificial Intelligence (AI). Particularly, recent advances in Deep Learning (DL) have enabled to develop a new breed of modeling and optimization tools with a plethora of applications in different fields like natural language processing, or computer vision.
In this context, the Knowledge-Defined Networking (KDN) paradigm highlights the lack of adoption of AI techniques in computer networks and – as a result – proposes a novel architecture that relies on Software-Defined Networking (SDN) and modern network analytics techniques to facilitate the deployment of ML-based solutions for efficient network operation.
This dissertation aims to be a step forward in the realization of Knowledge-Defined Networks. In particular, we focus on the application of AI techniques to control and optimize networks more efficiently and automatically. To this end, we identify two components within the KDN context whose development may be crucial to achieve self-operating networks in the future: (i) the automatic control module, and (ii) the network analytics platform.
The first part of this thesis is devoted to the construction of efficient automatic control modules. First, we explore the application of Deep Reinforcement Learning (DRL) algorithms to optimize the routing configuration in networks. DRL has recently demonstrated an outstanding capability to solve efficiently decision-making problems in other fields. However, first DRL-based attempts to optimize routing in networks have failed to achieve good results, often under-performing traditional heuristics. In contrast to previous DRL-based solutions, we propose a more elaborate network representation that facilitates DRL agents to learn efficient routing strategies. Our evaluation results show that DRL agents using the proposed representation achieve better performance and learn faster how to route traffic in an Optical Transport Network (OTN) use case. Second, we lay the foundations on the use of Graph Neural Networks (GNN) to build ML-based network optimization tools. GNNs are a newly proposed family of DL models specifically tailored to operate and generalize over graphs of variable size and structure. In this thesis, we posit that GNNs are well suited to model the relationships between different network elements inherently represented as graphs (e.g., topology, routing). Particularly, we use a custom GNN architecture to build a routing optimization solution that – unlike previous ML-based proposals – is able to generalize well to topologies, routing configurations, and traffic never seen during the training phase.
The second part of this thesis investigates the design of practical and efficient network analytics solutions in the KDN context. Network analytics tools are crucial to provide the control plane with a rich and timely view of the network state. However this is not a trivial task considering that all this information turns typically into big data in real-world networks. In this context, we analyze the main aspects that should be considered when measuring and classifying traffic in SDN (e.g., scalability, accuracy, cost). As a result, we propose a practical solution that produces flow-level measurement reports similar to those of NetFlow/IPFIX in traditional networks. The proposed system relies only on native features of OpenFlow – currently among the most established standards in SDN – and incorporates mechanisms to maintain efficiently flow-level statistics in commodity switches and report them asynchronously to the control plane. Additionally, a system that combines ML and Deep Packet Inspection (DPI) identifies the applications that generate each traffic flow.La evolución del campo del Aprendizaje Maquina (ML) en la última década ha dado lugar a una nueva era de la Inteligencia Artificial (AI). En concreto, algunos avances en el campo del Aprendizaje Profundo (DL) han permitido desarrollar nuevas herramientas de modelado y optimización con múltiples aplicaciones en campos como el procesado de lenguaje natural, o la visión artificial. En este contexto, el paradigma de Redes Definidas por Conocimiento (KDN) destaca la falta de adopción de técnicas de AI en redes y, como resultado, propone una nueva arquitectura basada en Redes Definidas por Software (SDN) y en técnicas modernas de análisis de red para facilitar el despliegue de soluciones basadas en ML. Esta tesis pretende representar un avance en la realización de redes basadas en KDN. En particular, investiga la aplicación de técnicas de AI para operar las redes de forma más eficiente y automática. Para ello, identificamos dos componentes en el contexto de KDN cuyo desarrollo puede resultar esencial para conseguir redes operadas autónomamente en el futuro: (i) el módulo de control automático y (ii) la plataforma de análisis de red. La primera parte de esta tesis aborda la construcción del módulo de control automático. En primer lugar, se explora el uso de algoritmos de Aprendizaje Profundo por Refuerzo (DRL) para optimizar el encaminamiento de tráfico en redes. DRL ha demostrado una capacidad sobresaliente para resolver problemas de toma de decisiones en otros campos. Sin embargo, los primeros trabajos que han aplicado DRL a la optimización del encaminamiento en redes no han conseguido rendimientos satisfactorios. Frente a dichas soluciones previas, proponemos una representación más elaborada de la red que facilita a los agentes DRL aprender estrategias de encaminamiento eficientes. Nuestra evaluación muestra que cuando los agentes DRL utilizan la representación propuesta logran mayor rendimiento y aprenden más rápido cómo encaminar el tráfico en un caso práctico en Redes de Transporte Ópticas (OTN). En segundo lugar, se presentan las bases sobre la utilización de Redes Neuronales de Grafos (GNN) para construir herramientas de optimización de red. Las GNN constituyen una nueva familia de modelos de DL específicamente diseñados para operar y generalizar sobre grafos de tamaño y estructura variables. Esta tesis destaca la idoneidad de las GNN para modelar las relaciones entre diferentes elementos de red que se representan intrínsecamente como grafos (p. ej., topología, encaminamiento). En particular, utilizamos una arquitectura GNN específicamente diseñada para optimizar el encaminamiento de tráfico que, a diferencia de las propuestas anteriores basadas en ML, es capaz de generalizar correctamente sobre topologías, configuraciones de encaminamiento y tráfico nunca vistos durante el entrenamiento La segunda parte de esta tesis investiga el diseño de herramientas de análisis de red eficientes en el contexto de KDN. El análisis de red resulta esencial para proporcionar al plano de control una visión completa y actualizada del estado de la red. No obstante, esto no es una tarea trivial considerando que esta información representa una cantidad masiva de datos en despliegues de red reales. Esta parte de la tesis analiza los principales aspectos a considerar a la hora de medir y clasificar el tráfico en SDN (p. ej., escalabilidad, exactitud, coste). Como resultado, se propone una solución práctica que genera informes de medidas de tráfico a nivel de flujo similares a los de NetFlow/IPFIX en redes tradicionales. El sistema propuesto utiliza sólo funciones soportadas por OpenFlow, actualmente uno de los estándares más consolidados en SDN, y permite mantener de forma eficiente estadísticas de tráfico en conmutadores con características básicas y enviarlas de forma asíncrona hacia el plano de control. Asimismo, un sistema que combina ML e Inspección Profunda de Paquetes (DPI) identifica las aplicaciones que generan cada flujo de tráfico.
16
Lü, Wenzhen. "Network development for competitive advantage, a study of subsidiary networks and alliance networks". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/NQ58404.pdf.
Testo completo
17
Ellerbrock, Thomas M. "Multilayer neural networks learnability, network generation, and network simplification /". [S.l. : s.n.], 1999. http://deposit.ddb.de/cgi-bin/dokserv?idn=958467897.
Testo completo
18
Schuhart, Russell G. "Hacking social networks examining the viability of using computer network attack against social networks". Thesis, Monterey, Calif. : Naval Postgraduate School, 2007. http://bosun.nps.edu/uhtbin/hyperion.exe/07Mar%5FSchuhart.pdf.
Testo completoAbstract (sommario):
Thesis (M.S. in Information Systems and Operations)--Naval Postgraduate School, March 2007.Thesis Advisor(s): David Tucker. "March 2007." Includes bibliographical references (p. 55-56). Also available in print.
19
Schultz, Paul. "Stability Concepts of Networked Infrastructure Networks". Doctoral thesis, Humboldt-Universität zu Berlin, 2018. http://dx.doi.org/10.18452/19310.
Testo completoAbstract (sommario):
Aktuell unterliegt unsere Stromversorgung mit der Energiewende einer Transformation, welche letzten Endes auch Änderungen der Struktur des Stromnetzes bedingt. Jenes ist ein hochkomplexes System aus unzähligen Erzeugern und Verbrauchern die miteinander wechselwirken. Im Lichte dessen leiten sich, (nicht nur) für zukünftige Stromnetze, einige methodischen Fragen ab. Wie kann die Stabilität verschiedener Betriebszustände oder Szenarien miteinander verglichen werdem? Welches sind die neuralgischen Punkte eines Stromnetzes? Zu welchem Grad bestimmt die Netzwerkstruktur die Systemstabilität? Im Zentrum der vorliegenden Dissertation steht dabei das emergente Phänomen der Synchronisation in Oszillatornetzwerken sowie dessen Stabilität. Im Bezug auf Stromnetze ist die Synchronisation dadurch gekennzeichnet, dass alle Erzeuger und Verbraucher mit der Netzfrequenz im Takt schwingen. Mit probabilistischen Stabilitätsmaßen lässt sich die Systemstabilität auf verschiedene Art quantifizieren. Neben einer Untersuchung möglicher Beschränkungen werden zwei neue probabilistische Maße entwickelt. Dabei spielen insbesondere die Häufigkeit und Dauer von Störungen sowie die Einhaltung der Betriebsgrenzen eine Rolle. Weiterhin wird der Einfluss kleiner Netzwerkstrukturen, sogenannter Motive, auf die Stabilität herausgearbeitet. Hierzu werden die Stabilitätsmaße in statistischen Verfahren mit charakteristischen Größen aus der Netzwerktheorie verknüpft. Es zeigt sich dann, dass das Auftreten spezieller Motive die Systemstabilität erhöht, wohingegen andere diese herabsetzen. Diese Zusammenhänge zwischen Netzwerkmotiven und Stabilität der Synchronisation erweitern die Kenntnisse über Zusammenhänge zwischen Struktur und Stabilität komplexer Systeme. Darüber hinaus erweitern die neu entwickelten probabilistischen Stabilitätsmaße das Methodenspektrum der nichtlinearen Dynamik zur Stabilitätsanalyse, insbesondere für Systeme auf komplexen Netzwerken mit vielen Freiheitsgraden.In the light of the energy transition, power systems undergo a major transformation enabled by appropriate modifications of the grid’s underlying structure. This network constitutes the complex interaction of numerous producers and consumers. The power grid is additionally subject to intermittent disturbances that also include large deviations. These aspects prompt methodological problems for (future) power grids in particular and complex systems in general. How can the stability of different operating points or scenarios be compared? What are the critical components of the network? To which extent is the stability of an operating point determined by the network structure? This dissertation focusses on the emergent phenomenon of synchronisation on networks. In power grids, this corresponds to all units working at the same rhythm – the rated grid frequency. Regarding an analysis with so-called probabilistic stability measures, important limitations are discussed and novel approaches are developed. In particular, the new measures consider repeated perturbations as well as operational bounds on transient deviations. Moreover, the influence of small network structures, so-called motifs, on the stability is investigated. For this purpose, the stability measures are paired with network characteristics using statistical approaches. On this basis, it turns out that, while the abundance of special motifs enhances stability, others typically diminish it. In conclusion, the development of analysis methods and their comparison with network characteristics uncovers relationships between network motifs and the stability of synchronisation. These results are general to a large class of complex systems and build a foundation to future research in this direction. In addition to that, the novel probabilistic stability measures extend the range of methods in nonlinear dynamics by important aspects, especially for high-dimensional complex systems.
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Lordan, Oriol. "Airline route networks : a complex network approach". Doctoral thesis, Universitat Politècnica de Catalunya, 2014. http://hdl.handle.net/10803/144526.
Testo completoAbstract (sommario):
Communication via air routes is an important issue in a world organized around a web-like city network. In this context, the robustness of network infrastructures, e.g. air transport networks, are a central issue in transport geography. Disruption of communication links by intentional causes (e.g., terrorist attack on an airport) or unintentional (e.g., weather inclemency) could be a serious drawback for countries, regions and airlines. Policymakers and the management of airlines and alliances should be able to reduce the effects of such interruptions in order to ensure good communication through air transport (i.e., maximize the robustness of their network at a reasonable cost). The literature review of the study of air transport route networks through an analysis of complex networks has highlighted a lack of contributions to the study of the topology and the robustness of such networks, which contrasts with advances undertaken for other transport networks or communication systems. The literatura survey suggests areas in which research should be undertaken, based on the existing literature in other areas and from three different perspectives: global route networks, airline alliances and airlines. The aim of this research is to develop a better understanding of air traffic and, in particular, to be able to assess the potential damage of any airport being inoperative for a continent, country or airline.
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Nerini, Matteo. "Network Slicing for IEEE 802.11 Wireless Networks". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2020. http://amslaurea.unibo.it/21149/.
Testo completoAbstract (sommario):
Future networks will pave the way for a myriad of applications with different requirements. In such a context, the today’s one-size-fits-all approach will not be able to efficiently address the different demands that verticals impose in terms of QoS and involved data volumes. To this end, network slicing is a new network paradigm which may provide the needed flexibility. It allows to offer multiple logical networks over a common infrastructure, tailored to the services which run on the network.
In today’s Wi-Fi networks, all the users are connected to the same wireless channel, which allows service differentiation only at the traffic level. Thus, in this study, we propose a standard-compliant network slicing approach for the radio access segment of Wi-Fi, often neglected by the literature on network slicing.
We present two algorithms to realize network slicing at the access level. The first assigns resources according to the requirements of the slices in a static way. On the other hand, the second, more advanced, dynamically configures the slices according to the network conditions and relevant KPIs. These techniques can be applied to the IEEE 802.11 standard and, in general, to all the protocols that use Carrier Sensing Multiple Access (CSMA) as channel access technique.
The proposed algorithms were validated through extensive simulations, conducted with ns-3 network simulator and accompanied by theoretical calculations. Particular attention, often neglected in similar simulation-based works, has been paid to the electromagnetic properties of the spectrum, which play a fundamental role in radio communications.
From the conducted simulations, we found that our slicing approaches largely outperform the today’s Wi-Fi access technique. They allow to reach higher goodput (i.e. a lower error probability) and lower latency, when needed. At the same time, tailored slicing saves energy to low-power devices and increases the spectrum efficiency.
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Saxena, Paresh. "Systematic network coding for lossy line networks". Doctoral thesis, Universitat Autònoma de Barcelona, 2015. http://hdl.handle.net/10803/287982.
Testo completoAbstract (sommario):
Esta tesis doctoral se centra en esquemas de codificación de red sistemáticos (SNC por sus siglas en inglés para systematic network coding) a nivel de paquete para proporcionar resistencia a la pérdida de paquetes en redes lineales con pérdidas. En la teoría, la codificación de red ( network coding ) es conocida por la mejora en rendimiento y fiabilidad en redes con pérdidas. Sin embargo, la traducción de la teoría del network coding en soluciones prácticas comprende algunos desafíos críticos. Esta tesis aborda estos desafíos e investiga soluciones de network coding que puedan ser usadas en la práctica para diferentes instancias de redes lineales con pérdidas.
Los objetivos principales de esta tesis doctoral son: 1) desarrollar un modelo matricial que permita el tratamiento analítico de network coding para redes con pérdidas, 2) investigar de manera semi-analítica el rendimiento alcanzable y la fiabilidad para redes lineales, un simple pero útil modelo de red conceptual, 3) desarrollar esquemas prácticos de network coding para redes lineales que superen significativamente el rendimiento del estado del arte en esquemas basados puramente en la correción de borrado hacia adelante (FEC por sus siglas en ingles para forward erasure correction), y 4) estar en línea con los esfuerzos del equipo de trabajo de la investigación en internet, Internet Research Task Force (IRTF) y presentar contribuciones. Las contribuciones de esta tesis, tal que se cumplen los objetivos son las siguientes.
Primero, investigamos el uso de SNC en redes con pérdida de un solo salto. Desarrollamos un modelo matricial para este caso sin re-codificar en la red. Esto nos permite comparar códigos separables de máxima distancia (MDS por su sigla en inglés) con SNC cuando se usan únicamente como FEC. Derivamos la mínima distancia de SNC y mostramos que SNC puede proporcionar fiabilidad tan cercana al MDS como se desee y lo permita el tamaño del campo. Simulamos aplicaciones prácticas a nivel de capa de aplicación de la pila de protocolos con dos resultados concretos. Primero, se muestra que utilizando decodificación progresiva de SNC se alcanzan retardos más bajos que con un código MDS y segundo, se obtiene una distribución óptima del ancho de banda para la tasa de network coding mientras se aplica SNC in redes con bandas limitadas.
Segundo, investigamos la aplicación de SNC en redes de dos saltos con pérdidas. Extendemos el modelo matricial para redes con un nodo intermedio. Usando el planteamiento semi-análitico, estudiamos y caracterizamos la fiabilidad y tasa alcanzable como una función de la tasa de network coding y de la capacidad de la red. Simulamos las aplicaciones prácticas en la capa de enlace del estándar Digital Video Broadcasting via Satellite-Second Generation (DVB-S2). Proponemos un marco con arquitectura y encapsulamiento tal que se pueda usar network coding en protocolos de la capa de enlace del DVB-S2.
Tercero, extendemos el modelo matricial para una red con varios nodos intermedios. Esto nos permite entender el marco matemático de mapear entidades de comunicaciones con entidades matemáticas en diferentes nodos intermedios de la red. Analizamos la fiabilidad, las tasas alcanzables, el retardo y la complejidad de los esquemas de network coding de manera semi-analítica y probamos que nuestros resultados están en línea con los resultados de la teoría de la información. Finalmente, desarrollamos un esquema inteligente de re-codificación de network coding que incluye la planificación de paquetes en los nodos intermedios. Nuestra propuesta proporciona menor retardo y menor complejidad comparada con el estado del arte en esquemas de network coding.This dissertation focuses on packet-level systematic network coding (SNC) schemes to provide resilience to packet losses in lossy line networks. In theory, network coding is known to improve throughput and reliability of lossy networks. However, the translation of the network coding theory into efficient practical network coding solutions involves some critical challenges. This dissertation addresses those challenges and investigates on network coding solutions that can be utilized in practice for different instances of the lossy line networks. The main objectives of this dissertation are: 1) to develop a matricial model that allows analytical treatment of network coding for lossy networks, 2) semi-analytical investigation of achievable throughput and reliability for line networks, a simple yet useful conceptual network model, 3) to develop practical network coding schemes for line networks that significantly outperform state-of-the-art purely forward erasure correction (FEC)-based schemes and 4) to be in line with Internet Research Task Force (IRTF) efforts and eventually contribute. The contributions of this thesis, such that the objectives are met are as follows. First, we investigate the application of SNC in one-hop lossy networks. We develop a matricial model for the case without re-encoding in the network. This allows us to compare maximum distance separable (MDS) codes with SNC when used as FEC only. We derive the minimum distance of SNC and show that SNC can provide as closed as wished to MDS reliability as the field sizes is allowed to grow. We simulate practical applications at application layer of the protocol stack with two concrete results. First, it is shown that by using progressive decoding SNC achieves smaller delay than the MDS code and second, an optimal bandwidth distribution for network coding rate is obtained while applying SNC in band-limited networks. Second, we investigate the application of SNC in two-hop lossy networks. We extend the matricial model for the networks with one intermediate node. Using the semi-analytical approach, we study and characterize the reliability and achievable rate as a function of network coding rate and capacity of the network. We simulate practical applications at link layer of Digital Video Broadcasting via Satellite-Second Generation (DVB-S2). We propose an architectural and encapsulation framework so that network coding can be used over the state-of-the-art protocols at link layer of DVB-S2. Third, we extend the matricial model for the network with several intermediate nodes. This allows us to understand the mathematical framework of mapping communication entities to mathematical entities at different intermediate nodes of the network. We analyze semi-analytically reliability, achievable rates, delay and complexity of network coding schemes and prove that our results are inline with information theoretical results. Finally, we develop a smart re-encoding network coding scheme that includes packet scheduling at the intermediate nodes. Our proposal is shown to provide smaller delay and smaller complexity than state-of-the-art network coding schemes.
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Tseliou, Georgia. "Network virtualization in next generation cellular networks". Doctoral thesis, Universitat Politècnica de Catalunya, 2019. http://hdl.handle.net/10803/667301.
Testo completoAbstract (sommario):
The complexity of operation and management of emerging cellular networks significantly increases, as they evolve to correspond to increasing QoS needs, data rates and diversity of offered services. Thus critical challenges appear regarding their performance. At the same time, network sustainability pushes toward the utilization of haring Radio Access Network (RAN) infrastructure between Mobile Network Operators (MNOs). This requires advanced network management techniques which have to be developed based on characteristics of these networks and traffic demands. Therefore it is necessary to provide solutions enabling the creation of logically isolated network partitions over shared physical network infrastructure. Multiple heterogeneous virtual networks should simultaneously coexist and support resource aggregation so as to appear as a single resource to serve different traffic types on demand.
Hence in this thesis, we study RAN virtualization and slicing solutions destined to tackle these challenges. In the first part, we present our approach to map virtual network elements onto radio resources of the substrate physical network, in a dense multi-tier LTE-A scenario owned by a MNO. We propose a virtualization solution at BS level, where baseband modules of distributed BSs, interconnected via logical point-to-point X2 interface, cooperate to reallocate radio resources on a traffic need basis. Our proposal enhances system performance by achieving 53% throughput gain compared with benchmark schemes without substantial signaling overhead. In the second part of the thesis, we concentrate on facilitating resource provisioning between multiple Virtual MNOs (MVNOs), by integrating the capacity broker in the 3GPP network management architecture with minimum set of enhancements. A MNO owns the network and provides RAN access on demand to several MVNOs. Furthermore we propose an algorithm for on-demand resource allocation considering two types of traffic. Our proposal achieves 50% more admitted requests without Service Level Agreement (SLA) violation compared with benchmark schemes. In the third part, we devise and study a solution for BS agnostic network slicing leveraging BS virtualization in a multi-tenant scenario. This scenario is composed of different traffic types (e.g., tight latency requirements and high data rate demands) along with BSs characterized by different access and transport capabilities (i.e., Remote Radio Heads, RRHs, Small Cells, SCs and future 5G NodeBs, gNBs with various functional splits having ideal and non-ideal transport network). Our solution achieves 67% average spectrum usage gain and 16.6% Baseband Unit processing load reduction compared with baseline scenarios. Finally, we conclude the thesis by providing insightful research challenges for future works.La complejidad de la operación y la gestión de las emergentes redes celulares aumenta a medida que evolucionan para hacer frente a las crecientes necesidades de calidad de servicio (QoS), las tasas de datos y la diversidad de los servicios ofrecidos. De esta forma aparecen desafíos críticos con respecto a su rendimiento. Al mismo tiempo, la sostenibilidad de la red empuja hacia la utilización de la infraestructura de red de acceso radio (RAN) compartida entre operadores de redes móviles (MNO). Esto requiere técnicas avanzadas de gestión de redes que deben desarrollarse en función de las características especiales de estas redes y las demandas de tráfico. Por lo tanto, es necesario proporcionar soluciones que permitan la creación de particiones de red aisladas lógicamente sobre la infraestructura de red física compartida. Para ello, en esta tesis, estudiamos las soluciones de virtualización de la RAN destinadas a abordar estos desafíos. En la primera parte de la tesis, nos centramos en mapear elementos de red virtual en recursos de radio de la red física, en un escenario LTE-A de múltiples niveles que es propiedad de un solo MNO. Proponemos una solución de virtualización a nivel de estación base (BS), donde los módulos de banda base de BSs distribuidas, interconectadas a través de la interfaz lógica X2, cooperan para reasignar los recursos radio en función de las necesidades de tráfico. Nuestra propuesta mejora el rendimiento del sistema al obtener un rendimiento 53% en comparación con esquemas de referencia. En la segunda parte de la tesis, nos concentramos en facilitar el aprovisionamiento de recursos entre muchos operadores de redes virtuales móviles (MVNO), al integrar el capacity broker en la arquitectura de administración de red 3GPP con un conjunto míinimo de mejoras. En este escenario, un MNO es el propietario de la red y proporciona acceso bajo demanda (en inglés on-demand) a varios MVNOs. Además, para aprovechar al máximo las capacidades del capacity broker, proponemos un algoritmo para la asignación de recursos bajo demanda, considerando dos tipos de tráfico con distintas características. Nuestra propuesta alcanza 50% más de solicitudes admitidas sin violación del Acuerdo de Nivel de Servicio (SLA) en comparación con otros esquemas. En la tercera parte de la tesis, estudiamos una solución para el slicing de red independiente del tipo de BS, considerando la virtualización de BS en un escenario de múltiples MVNOs (multi-tenants). Este escenario se compone de diferentes tipos de tráfico (por ejemplo, usuarios con requisitos de latencia estrictos y usuarios con altas demandas de velocidad de datos) junto con BSs caracterizadas por diferentes capacidades de acceso y transporte (por ejemplo, Remote Radio Heads, RRHs, Small cells, SC y 5G NodeBs, gNBs con varias divisiones funcionales que tienen una red de transporte ideal y no ideal). Nuestra solución logra una ganancia promedio de uso de espectro de 67% y una reducción de la carga de procesamiento de la banda base de 16.6% en comparación con escenarios de referencia. Finalmente, concluimos la tesis al proporcionando los desafíos y retos de investigación para trabajos futuros.
24
Yang, Weilai. "Pricing Network Resources for Differentiated Service Networks". Diss., Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/5227.
Testo completoAbstract (sommario):
We developed a price-based resource allocation scheme for Differentiated Service (DiffServ) data networks. The DiffServ framework was proposed to provide multiple QoS classes over IP networks. Since the provider supports multiple service classes, we need a differentiated pricing scheme, as supposed to the flat-rate scheme employed by the Internet service providers of today. Charging efficiently is a big issue. The utility of a client correlates to the amount of bandwidth allocated. One difficulty we face is that determining the appropriate amount of bandwidth to provision and allocate is problematic due to different time scales, multiple QoS classes and the unpredictable nature of users.
To approach this problem, we designed a pricing strategy for Admission Control and bandwidth assignment. Despite the variety of existing pricing strategies, the common theme is that the appropriate pricing policy rewards users for behaving in ways to improve the overall utilization and performance of the network. Among existing schemes, we chose auction because it is scalable, and efficiently and fairly shares resources. Our pricing model takes the system's availability and each customer's requirements as inputs and outputs the set of clients who are admitted into the network and their allocated resource. Each client proposes a desired bandwidth and a price that they are willing to pay for it. The service provider collects this information and produces parameters for each class of service they provide. This information is used to decide which customers to admit.
We proposed an optimal solution to the problem of maximizing the provider's revenue for the special case where there is only one bottleneck link in the network. Then for the generalized network, we resort to a simple but effective heuristic method. We validate both the optimal solution and the heuristic algorithm with simulations driven by a real traffic scenario. Finally, we allow customers to bid on the duration for which the service is needed. Then we study the performance of those heuristic algorithms in this new setting and propose possible improvements.
25
Alesand, Alexander. "Emulating 3G Network Characteristics on WiFi Networks". Thesis, Linköpings universitet, Programvara och system, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-122040.
Testo completoAbstract (sommario):
Mobile applications should work regardless of which type of wireless interface is used, and should be able to conceal unstable connections from the user to improve user experience. Therefore, network testing is important when developing mobile applications, but it is a challenge to reproduce network conditions when using real cellular networks since the test engineer has no control over the quality of the cellular network. Existing software tools can restrict bandwidth and add latency to the connection, but these tools do not accurately emulate cellular networks. This thesis proposes a system where it is possible to shape the network traffic for connected devices to mimic the network patterns of a real cellular connection when running on a WiFi connection. The design presented in this thesis is intended for testing mobile applications under diverse 3G connection parameters, such as latency, bandwidth and other characteristics. This thesis was conducted at Spotify, a company that provides a music streaming service which is a frequent user of network data traffic. The 3G emulator was evaluated using the Spotify Android application by measuring the correlation between packet traces from a real 3G connection and the 3G emulator. This correlation was compared to the correlation between packet traces from a real 3G connection and the current network emulator at Spotify. The evaluation shows that the proposed 3G emulator outperforms the current network emulator when performing tests on the Spotify application for Android. By using this emulator, we expect the network testing to become more effective as any 3G condition can be tested with repeatable results.
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Malmgren, Göran. "Network Planning of Single Frequency Broadcasting Networks". Licentiate thesis, KTH, Signaler, sensorer och system, 1996. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-28559.
Testo completo
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Tan, Hailun Computer Science & Engineering Faculty of Engineering UNSW. "Secure network programming in wireless sensor networks". Awarded By:University of New South Wales. Computer Science & Engineering, 2010. http://handle.unsw.edu.au/1959.4/44835.
Testo completoAbstract (sommario):
Network programming is one of the most important applications in Wireless Sensor Networks as It provides an efficient way to update program Images running on sensor nodes without physical access to them. Securing these updates, however, remains a challenging and important issue, given the open deployment environment of sensor nodes. Though several security schemes have been proposed to impose the authenticity and Integrity protection on network programming applications, they are either energy Inefficient as they tend to use digital signature or lacks the data confidentiality. In addition, due to the absence of secure memory management in the current sensor hardware, the attacker could inject malicious code into the program flash by exploiting buffer overflow In the memory despite the secure code dissemination. The contribution of this thesis Is to provide two software-based security protocols and one hardware-based remote attestation protocol for network programming application. Our first protocol deploys multiple one-way key chains for a multi-hop sensor network. The scheme Is shown to be lower In computational, power consumption and communication costs yet still able to secure multi??hop propagation of program images. Our second protocol utilizes an Iterative hash structure to the data packets in network programming application, ensuring the data confidentiality and authenticity. In addition, we Integrated confidentiality and DoS-attack-resistance in a multi??hop code dissemination protocol. Our final solution is a hardware-based remote attestation protocol for verification of running codes on sensor nodes. An additional piece of tamper-proof hardware, Trusted Platform Module (TPM), is imposed into the sensor nodes. It secures the sensitive information (e.g., the session key) from attackers and monitors any platform environment changes with the Internal registers. With these features of TPM, the code Injection attack could be detected and removed when the contaminated nodes are challenged in our remote attestation protocol. We implement the first two software-based protocols with Deluge as the reference network programming protocol in TinyOS, evaluate them with the extensive simulation using TOSSIM and validate the simulation results with experiments using Tmote. We implement the remote attestation protocol on Fleck, a sensor platform developed by CSIRO that Integrates an Atmel TPM chip.
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Tang, Jeffrey. "Tolerating network errors in system area networks". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/MQ62973.pdf.
Testo completo
29
Hildebrand, Matthias. "Optimized network access in heterogeneous wireless networks". Kassel : Kassel Univ. Press, 2005. http://deposit.d-nb.de/cgi-bin/dokserv?idn=977677540.
Testo completo
30
Lee, Anna H. "Simplified random network codes for multicast networks". Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/33306.
Testo completoAbstract (sommario):
Thesis (M. Eng. and S.B.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2005.Includes bibliographical references (p. 43).
Network coding is a method of data transmission across a network which involves coding at intermediate nodes. Network coding is particularly attractive for multicast. Building on the work done on random linear network codes, we develop a constrained, simplified code construction suitable for multicast in wireless networks. We analyze bounds on sufficient code size and code success probability via an algebraic framework for network coding. We also present simulation results that compare generalized random network codes with our code construction. Issues unique to the simplified code are explored and a relaxation of the code to improve code performance is discussed.
by Anna H. Lee.
M.Eng.and S.B.
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Shi, Xiaomeng Ph D. Massachusetts Institute of Technology. "Energy aware network coding in wireless networks". Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/78533.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2012.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 97-104).
Energy is one of the most important considerations in designing reliable low-power wireless communication networks. We focus on the problem of energy aware network coding. In particular, we investigate practical energy efficient network code design for wireless body area networks (WBAN). We first consider converge-cast in a star-shaped topology, in which a central base station (BS), or hub, manages and communicates directly with a set of nodes. We then consider a wireless-relay channel, in which a relay node assists in the transmission of data from a source to a destination. This wireless relay channel can be seen as a simplified extended star network, where nodes have relay capabilities. The objective is to investigate the use of network coding in these scenarios, with the goal of achieving reliability under low-energy and lower-power constraints. More specifically, in a star network, we propose a simple network layer protocol, study the mean energy to complete uploads of given packets from the nodes to the BS using a Markov chain model, and show through numerical examples that when reception energy is taken into account, the incorporation of network coding offers reductions in energy use. The amount of achievable gains depends on the number of nodes in the network, the degree of asymmetry in channel conditions experienced by different nodes, and the relative difference between transmitting and receiving power at the nodes. We also demonstrate the compatibility of the proposed scheme with the IEEE 802.15.6 WBAN standard by describing ways of incorporating network coding into systems compliant to the standard. For a wireless relay channel, we explore the strategic use of network coding according to both throughput and energy metrics. In the relay channel, a single source communicates to a single sink through the aid of a half-duplex relay. The fluid flow model is used to describe the case where both the source and the relay are coding, and Markov chain models are proposed to describe packet evolution if only the source or only the relay is coding. Although we do not attempt to explicitly categorize the optimal network coding strategies in the relay channel under different system parameters, we provide a framework for deciding whether and where to code, taking into account of throughput maximization and energy depletion constraints.
by Xiaomeng Shi.
Ph.D.
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Bays, Leonardo Richter. "Virtual network embedding in software-defined networks". reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2017. http://hdl.handle.net/10183/178658.
Testo completoAbstract (sommario):
Pesquisas acadêmicas em virtualização de redes vêm sendo realizadas durante diversos anos, nos quais diferentes abordagens de alocação de redes virtuais foram propostas. Tais abordagens, no entanto, negligenciam requisitos operacionais importantes impostos por plataformas de virtualização. No caso de virtualização baseada em SDN/OpenFlow, um exemplo fundamental de tais requisitos operacionais é a disponibilidade de espaço de memória para armazenar regras em dispositivos OpenFlow. Diante dessas circunstâncias, argumentamos que a alocação de redes virtuais deve ser realizada com certo grau de conhecimento sobre infraestruturas físicas; caso contrário, após instanciadas, tais redes podem sofrer instabilidade ou desempenho insatisfatório. Considerando redes físicas baseadas em SDN/OpenFlow como um cenário importante de virtualização, propõe-se um arcabouço baseado na coordenação entre a alocação de redes virtuais e redes OpenFlow para realizar a instanciação de redes virtuais de forma adequada. A abordagem proposta desdobra-se nas seguintes contribuições principais: uma abstração de infraestruturas virtuais que permite que um requisitante represente os detalhes de seus requerimentos de rede de maneira aprofundada; um compilador ciente de privacidade que é capaz de pré-processar requisições com tal grau de detalhamento, ofuscando informações sensíveis e derivando requisitos operacionais computáveis; um modelo para a alocação de redes virtuais que visa a maximizar a viabilidade no nível físico. Resultados obtidos por meio de uma avaliação da nossa abordagem evidenciam que considerar tais requisitos operacionais, bem como computá-los de forma precisa, é imprescindível para garantir a “saúde” das redes virtuais hospedadas na plataforma de virtualização considerada.Research on network virtualization has been active for a number of years, during which a number of virtual network embedding (VNE) approaches have been proposed. These approaches, however, neglect important operational requirements imposed by the underlying virtualization platforms. In the case of SDN/OpenFlow-based virtualization, a crucial example of an operational requirement is the availability of enough memory space for storing flow rules in OpenFlow devices. Due to these circumstances, we advocate that VNE must be performed with some degree of knowledge of the underlying physical networks, otherwise the deployment may suffer from unpredictable or even unsatisfactory performance. Considering SDN/OpenFlow-based physical networks as an important virtualization scenario, we propose a framework based on VNE and OpenFlow coordination for proper deployment of virtual networks (VNs). The proposed approach unfolds in the following main contributions a virtual infrastructure abstraction that allows a service provider to represent the details of his/her VN requirements in a comprehensive manner; a privacy-aware compiler that is able to preprocess this detailed VN request in order to obfuscate sensitive information and derive computable operational requirements; a model for embedding requested VNs that aims at maximizing their feasibility at the physical level. Results obtained through an evaluation of our framework demonstrate that taking such operational requirements into account, as well as accurately assessing them, is of paramount importance to ensure the “health” of VNs hosted on top of the virtualization platform.
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Dai, Wenhan. "Quantum networks : state transmission and network operation". Thesis, Massachusetts Institute of Technology, 2020. https://hdl.handle.net/1721.1/128289.
Testo completoAbstract (sommario):
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Thesis: Ph. D., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2020
Cataloged from student-submitted the PDF of thesis.
Includes bibliographical references (pages 147-155).
Quantum information science is believed to create the next technological revolution. As key ingredients of quantum information science, quantum networks enable various technologies such as secure communication, distributed quantum sensing, quantum cloud computing, and next-generation positioning, navigation, and timing. The main task of quantum networks is to enable quantum communication among different nodes in the network. This includes the topics such as the transmission of quantum states involving multiple parties, the processing of quantum information at end nodes, and the distribution of entanglement among remote nodes. Since quantum communication has its own peculiar properties that have no classical counterparts, the protocols and strategies designed for classical communication networks are not well-suited for quantum ones. This calls for new concepts, paradigms, and methodologies tailored for quantum networks.
To that end, this thesis studies the design and operation of quantum networks, with focus on the following three topics: state transmission, queueing delay, and remote entanglement distribution. The first part develops protocols to broadcast quantum states from a transmitter to N different receivers. The protocols exhibit resource tradeoffs between multiparty entanglement, broadcast classical bits (bcbits), and broadcast quantum bits (bqubits), where the latter two are new types of resources put forth in this thesis. We prove that to send 1 bqubit to N receivers using shared entanglement, O(logN) bcbits are both necessary and sufficient. We also show that the protocols can be implemented using poly(N) basic gates composed of single-qubit gates and CNOT gates. The second part introduces a tractable model for analyzing the queuing delay of quantum data, referred to as quantum queuing delay (QQD).
The model employs a dynamic programming formalism and accounts for practical aspects such as the finite memory size. Using this model, we develop a cognitive-memory-based policy for memory management and show that this policy can decrease the average queuing delay exponentially with respect to memory size. The third part offers a design of remote entanglement distribution (RED) protocols that maximize the entanglement distribution rate (EDR). We introduce the concept of enodes, representing the entangled quantum bit (qubit) pairs in the network. This concept enables us to design the optimal RED protocols based on the solutions of some linear programming problems. Moreover, we investigate RED in a homogeneous repeater chain, which is a building block for many quantum networks. In particular, we determine the maximum EDR for homogeneous repeater chains in a closed form. The contributions of this work provide guidelines for the design and implementation of quantum networks.
by Wenhan Dai.
Ph. D.
Ph.D. Massachusetts Institute of Technology, Department of Aeronautics and Astronautics
34
Rastogi, Preeti. "Assessing Wireless Network Dependability Using Neural Networks". Ohio University / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1129134364.
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Chambers, Mark Andrew. "Queuing network construction using artificial neural networks /". The Ohio State University, 2000. http://rave.ohiolink.edu/etdc/view?acc_num=osu1488193665234291.
Testo completo
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Taiwo, Olugbenga Adekunle. "Network access selection in heterogeneous wireless networks". Master's thesis, University of Cape Town, 2013. http://hdl.handle.net/11427/16832.
Testo completoAbstract (sommario):
In heterogeneous wireless networks (HWNs), both single-homed and multi-homed terminals are supported to provide connectivity to users. A multiservice single-homed multi-mode terminal can support multiple types of services, such as voice call, file download and video streaming simultaneously on any one of the available radio access technologies (RATs) such as Wireless Local Area Network (WLAN), and Long Term Evolution (LTE). Consequently, a single-homed multi-mode terminal having multiple on-going calls may need to perform a vertical handover from one RAT to another. One of the major issues in HWNs is how to select the most suitable RAT for multiple handoff calls, and the selection of a suitable RAT for multiple-calls from a single-homed multi-mode terminal in HWNs is a group decision problem. This is because a single-homed multi-mode terminal can connect to only one RAT at a time, and therefore multiple handoff calls from the terminal have to be handed over to the same RAT. In making group decision for multiple-calls, the quality of service (QoS) requirements for individual calls needs to be considered. Thus, the RAT that most satisfies the QoS requirements of individual calls is selected as the most suitable RAT for the multiple-calls. Whereas most research efforts in HWNs have concentrated on developing vertical handoff decision schemes for a single call from a multi-mode terminal, not much has been reported in the literature on RAT-selection for multiple-calls from a single-homed multi-mode terminal in next generation wireless networks (NGWNs). In addition, not much has been done to investigate the sensitivity of RAT-selection criteria for multiple-calls in NGWNs. Therefore, this dissertation addresses these issues by focusing on following two main aspects: (1) comparative analysis of four candidate multi-criteria group decision-making (MCGDM) schemes that could be adapted for making RAT-selection decisions for multiple-calls, and (2) development of a new RAT-selection scheme named the consensus RAT-selection model. In comparative analysis of the candidate RAT-selection schemes, four MCGDM schemes namely: distance to the ideal alternative-group decision making (DIA-GDM), multiplicative exponent weighting-group decision making (MEW-GDM), simply additive weighting-group decision making (SAW-GDM), technique for order preference by similarity to Ideal solution-group decision making (TOPSIS-GDM) are considered. The performance of the multiple-calls RAT-selection schemes is evaluated using the MATLAB simulation tool. The results show that DIA-GDM and TOPSIS-GDM schemes are more suitable for multiple handoff calls than SAW-GDM and MEW-GDM schemes. This is because they are consistent and less-sensitive in making RAT-selection decision than the other two schemes, with regards to RAT-selection criteria (service price, data rate, security, battery power consumption and network delay) in HWNs. In addition, the newly developed RAT-selection scheme incorporates RAT-consensus level for improving RAT-selection decisions for multiple-calls. Numerical results conducted in MATLAB validate the effectiveness and performance of the newly proposed RAT-selection scheme for multiple-calls in HWNs.
37
Cheng, Jerry. "Collaborative network security for heterogeneous mobile networks". Diss., Restricted to subscribing institutions, 2007. http://proquest.umi.com/pqdweb?did=1472132471&sid=1&Fmt=2&clientId=1564&RQT=309&VName=PQD.
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Glidden, Todd P. "Privacy for mobile networks via network virtualization". Thesis, Monterey, Calif. : Naval Postgraduate School, 2009. http://edocs.nps.edu/npspubs/scholarly/theses/2009/March/09Mar%5FGlidden.pdf.
Testo completoAbstract (sommario):
Thesis (M.S. in Computer Science)--Naval Postgraduate School, March 2009.Thesis Advisor(s): Singh, Gurminder ; Gibson, John. "March 2009." Description based on title screen as viewed on April 23, 2009. Author(s) subject terms: Privacy, mobile networks, first responders, mobile file sharing, data dissemination. Includes bibliographical references (p. 47-49). Also available in print.
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Lim, Tiong Hoo. "Dependable network protocols in wireless sensor networks". Thesis, University of York, 2013. http://etheses.whiterose.ac.uk/4903/.
Testo completoAbstract (sommario):
This thesis is concerned with the dependability of Wireless Sensor Networks (WSNs). We propose an approach, inspired by the immune system, that allows individual nodes to detect, diagnose and recover from different failures by switching between different protocols using a multi-modal switching mechanism. A causal link between different failures in WSN is identified. Existing fault tolerance in WSNs approaches are examined. From the survey, it is identified that various attempts have been made to improve the fault tolerance of the communication protocol especially in the routing protocols. Although tests have been performed to evaluate the communication protocols prior to deployment, failures in WSNs are still being reported when deployed in real environments. A Systematic Protocol Evaluation Technique (SPET) is proposed and applied to evaluate the dependability of the proposed multi-modal protocol and reduce the uncertainties in the experiment and to demonstrate the confidence in the measurements taken from experiments.
40
Bakri, Sihem. "Towards enforcing network slicing in 5G networks". Electronic Thesis or Diss., Sorbonne université, 2021. http://www.theses.fr/2021SORUS067.
Testo completoAbstract (sommario):
Les architectures de réseaux sans fil actuelles, de type « une taille pour tous », ne peuvent pas prendre en charge ces critères de services hétérogènes de nouvelle génération 5G. Par conséquent, la recherche autour de la 5G vise à fournir des architectures et des mécanismes plus adéquats pour répondre à ce besoin. L'architecture 5G est conçue pour répondre aux exigences variées et contradictoires des services, en termes de latence, de bande passante et de fiabilité, qui ne peuvent être assurées par la même infrastructure du réseau. Dans ce contexte, le découpage du réseau fourni par la virtualisation du réseau permet de diviser l'infrastructure en différentes tranches, chaque tranche est adaptée aux besoins spécifiques des services, où elle permet à différents services (comme l'automobile, l'Internet des objets...) d'être fournis par différentes instances de la tranche du réseau. Les chercheurs ont défini trois grandes classes de services de découpage en réseau, qui sont: enhanced Mobile BroadBand (eMBB), massive Machine Type Communication (mMTC), and ultra-Reliable and Low-Latency Communication (uRLLC). L'un des principaux défis du déploiement des tranches de réseau est le découpage du réseau d'accès radio (RAN). En effet, la gestion des ressources RAN et leur partage entre les tranches de réseau est une tâche particulièrement difficile. Cette thèse propose des solutions qui visent à améliorer les performances du réseau et d'introduire de la flexibilité et une plus grande utilisation des ressources du réseau, en fournissant de manière précise et dynamique aux tranches de réseau activées les quantités de ressources appropriées pour répondre à leurs divers besoinsThe current architecture “one size fits all” of 4G network cannot support the next-generation 5G heterogeneous services criteria. Therefore, research around 5G aims to provide more adequate architectures and mechanisms to deal with this purpose. The 5G architecture is envisioned to accommodate the diverse and conflicting demands of services in terms of latency, bandwidth, and reliability, which cannot be sustained by the same network infrastructure. In this context, network slicing provided by network virtualization allows the infrastructure to be divided into different slices. Each slice is tailored to meet specific service requirements allowing different services (such as automotive, Internet of Things, etc.) to be provided by different network slice instances. Each of these instances consists of a set of virtual network functions that run on the same infrastructure with specially adapted orchestration. Three main service classes of network slicing have been defined by the researchers as follows: Enhanced Mobile Broadband (eMBB), massive Machine Type Communication (mMTC), and ultra-Reliable and Low-Latency Communication (uRLLC). One of the main challenges when it comes to deploying Network Slices is slicing the Radio Access Network (RAN). Indeed, managing RAN resources and sharing them among Network Slices is an increasingly difficult task, which needs to be properly designed. This thesis proposes solutions that aim to improve network performance, and introduce flexibility and greater utilization of network resources by accurately and dynamically provisioning the activated network slices with the appropriate amounts of resources to meet their diverse requirements
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Abrahamsen, Morten Hoie. "Sensemaking in networks Using network pictures to understand network change". Thesis, University of Manchester, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.506619.
Testo completo
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Kim, Anthony Eli. "On network coding capacity : matroidal networks and network capacity regions". Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/62657.
Testo completoAbstract (sommario):
Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2010.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 68-70).
One fundamental problem in the field of network coding is to determine the network coding capacity of networks under various network coding schemes. In this thesis, we address the problem with two approaches: matroidal networks and capacity regions. In our matroidal approach, we prove the converse of the theorem which states that, if a network is scalar-linearly solvable then it is a matroidal network associated with a representable matroid over a finite field. As a consequence, we obtain a correspondence between scalar-linearly solvable networks and representable matroids over finite fields in the framework of matroidal networks. We prove a theorem about the scalar-linear solvability of networks and field characteristics. We provide a method for generating scalar-linearly solvable networks that are potentially different from the networks that we already know are scalar-linearly solvable. In our capacity region approach, we define a multi-dimensional object, called the network capacity region, associated with networks that is analogous to the rate regions in information theory. For the network routing capacity region, we show that the region is a computable rational polytope and provide exact algorithms and approximation heuristics for computing the region. For the network linear coding capacity region, we construct a computable rational polytope, with respect to a given finite field, that inner bounds the linear coding capacity region and provide exact algorithms and approximation heuristics for computing the polytope. The exact algorithms and approximation heuristics we present are not polynomial time schemes and may depend on the output size.
by Anthony Eli Kim.
M.Eng.
43
Hollingshad, Nicholas W. "A Non-equilibrium Approach to Scale Free Networks". Thesis, University of North Texas, 2012. https://digital.library.unt.edu/ark:/67531/metadc149609/.
Testo completoAbstract (sommario):
Many processes and systems in nature and society can be characterized as large numbers of discrete elements that are (usually non-uniformly) interrelated. These networks were long thought to be random, but in the late 1990s, Barabási and Albert found that an underlying structure did in fact exist in many natural and technological networks that are now referred to as scale free. Since then, researchers have gained a much deeper understanding of this particular form of complexity, largely by combining graph theory, statistical physics, and advances in computing technology. This dissertation focuses on out-of-equilibrium dynamic processes as they unfold on these complex networks. Diffusion in networks of non-interacting nodes is shown to be temporally complex, while equilibrium is represented by a stable state with Poissonian fluctuations. Scale free networks achieve equilibrium very quickly compared to regular networks, and the most efficient are those with the lowest inverse power law exponent. Temporally complex diffusion also occurs in networks with interacting nodes under a cooperative decision-making model. At a critical value of the cooperation parameter, the most efficient scale free network achieves consensus almost as quickly as the equivalent all-to-all network. This finding suggests that the ubiquity of scale free networks in nature is due to Zipf's principle of least effort. It also suggests that an efficient scale free network structure may be optimal for real networks that require high connectivity but are hampered by high link costs.
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Do-Duy, Tan. "Design of network coding functionality for 5G networks". Doctoral thesis, Universitat Autònoma de Barcelona, 2018. http://hdl.handle.net/10803/665972.
Testo completoAbstract (sommario):
La codificación de red (NC) ha surgido recientemente como una nueva solución para mejorar el rendimiento de la red en términos de rendimiento y fiabilidad. Sin embargo, la naturaleza multiusuario de NC y su aplicabilidad inherente a la ingeniería de flujo versátil en todas las capas de la pila de protocolos requieren nuevos enfoques de diseño de sistemas inalámbricos. El objetivo de esta tesis es estudiar el diseño de NC como una funcionalidad de red ofrecida a los diseñadores de servicios de comunicación inalámbrica 5G. El diseño facilitaría el control del rendimiento de la red, la confiabilidad y la conectividad a través de redes inalámbricas 5G. Las contribuciones de esta tesis son las siguientes. Primero desarrollamos un diseño de Funcionalidad de codificación de red como una caja de herramientas de dominios de diseño NC y mostramos cómo se puede integrar en las infraestructuras virtualizadas actuales. En segundo lugar, evaluamos el rendimiento de longitud finita de diferentes códigos de red usando matrices aleatorias vs Pascal. Modelamos el proceso de codificación, recodificación y decodificación de diferentes esquemas de codificación en notación de matriz y las correspondientes probabilidades de error. A continuación, proponemos un algoritmo de búsqueda binaria para identificar la velocidad de codificación óptima para algunas tasas de pérdida de paquetes de destino específicas dada una longitud de bloque de codificación predefinida. Nos enfocaremos en los códigos de logro de capacidad y los esquemas de codificación con la programación de escenarios representativos y mostraremos la compensación de la tasa de retardo alcanzable entre los códigos aleatorios y los códigos estructurados con la programación. En la última parte de esta tesis, validamos el diseño de NCF propuesto para un caso de uso completo para mejorar la conectividad de los dispositivos de red móvil ad-hoc (MANET) sobre las redes convergidas de nubes satelitales en aplicaciones de emergencia. La idea clave es que en un escenario de emergencia puede no haber acceso directo a la niebla o la computación en la nube, que luego se proporcionará por satélite y los únicos recursos computacionales locales disponibles son los dispositivos MANET. Para resolver esta situación, definimos un NCF a nivel de paquetes con entradas de objetivos de calidad del servicio de datos, restricciones de computación local y estadísticas por ruta. Las salidas son tasas de codificación centralmente optimizadas que equilibran los recursos computacionales por nodo y la cobertura resultante.Network coding (NC) has recently emerged as a new solution for improving network performance in terms of throughput and reliability. However, the multi-user nature of NC and its inherent applicability to versatile flow engineering across all layers of the protocol stack, call for novel wireless system design approaches. The goal of this thesis is to study the design of NC as a network functionality offered to the 5G wireless communication service designers. The design would facilitate the control of network throughput, reliability, and connectivity over 5G wireless networks. The contributions of this thesis are the following. We first develop a design of Network Coding Functionality as a toolbox of NC design domains and show how it can be integrated in current virtualized infrastructures. Second, we evaluate the finite-length performance of different network codes using random vs Pascal matrices. We model the encoding, re-encoding, and decoding process of different coding schemes in matrix notation and corresponding error probabilities. We then propose a binary searching algorithm to identify optimal coding rate for some specific target packet loss rates given a pre-defined coding block-length. We will focus on capacity-achieving codes and coding schemes with scheduling for representative scenarios and show the achievable rate-delay trade-off between random codes and structured codes with scheduling. In the last part of this thesis, we validate the proposed NCF design for a complete use case to enhance connectivity of Mobile Ad-hoc Network (MANET) devices over converged satellite-cloud networks in emergency applications. The key insight is that in an emergency scenario there may not be direct access to fog or cloud computing, which will then be provided via satellite and the only local computational resources available are the MANET devices. To solve this situation, we define a packet-level NCF with inputs from data service quality targets, local computation constraints and per-path statistics. Outputs are centrally-optimized coding rates balancing per-node computational resources and resulting coverage.
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Zhao, Wenrui. "Routing and Network Design in Delay Tolerant Networks". Diss., Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/14085.
Testo completoAbstract (sommario):
Delay tolerant networks (DTNs) are a class of emerging networks that exhibit significantly different characteristics from today's Internet, such as intermittent connectivity, large delay, and high loss rates. DTNs have important applications in disaster relief, military, rural Internet access, environmental sensing and surveillance, interplanetary communication, underwater sensing, and vehicular communication. While not the common case for networking, DTNs represent some of the most critical cases, where the ability to communicate can make a huge difference for human lives.
Supporting effective communication in DTNs, however, is challenging. First, with intermittent connectivity, DTNs are often extremely limited in capacity. Second, given resource limitations and uncertainty in DTNs, it is critical to deliver data efficiently and robustly. The situation is especially acute for multicast which sends data to multiple destinations.
This thesis seeks to address these two issues. To enhance network capacity in DTNs, we propose a message ferrying scheme that exploits the use of special mobile nodes (called message ferries) and controlled device mobility to deliver data. Message ferries are utilized to transport data via mobility between sources and destinations. We develop a foundation for the control of the mobility of message ferries, and nodes if possible, to cooperatively deliver data under a variety of conditions. We also study another approach which deploys new nodes called throwboxes to enhance capacity. Throwboxes are small and inexpensive wireless devices. By relaying data between mobile nodes, throwboxes are able to create data transfer opportunities that otherwise would not exist. We systematically investigate the issues of deployment and routing, and develop algorithms for various deployment and routing approaches. Based on extensive evaluation, we obtain several findings to guide the design and operation of throwbox-augmented DTNs.
To address the issue of efficient and robust data delivery, we focus on DTN multicasting. Given the unique characteristics of DTNs, traditional solutions such as IP multicast can not be simply ported to DTNs. We identify the limitations of IP multicast semantics in DTNs and define new semantic models for DTN multicast. Based on these semantic models, we develop and evaluate several multicast routing algorithms with different routing strategies.
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Sevgi, Cuneyt. "Network Dimensioning In Randomly Deployed Wireless Sensor Networks". Phd thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/2/12611213/index.pdf.
Testo completoAbstract (sommario):
In this study, we considered a heterogeneous, clustered WSN, which consists of two
types of nodes (clusterheads and sensor nodes) deployed randomly over a sensing field.
We investigated two cases based on how clusterheads can reach the sink: direct and
multi-hop communication cases. Network dimensioning problems in randomly deployed
WSNs are among the most challenging ones as the attributes of these networks are
mostly non-deterministic. We focused on a number of network dimensioning problems
based on the connected coverage concept, which is the degree of coverage achieved by
only the connected devices. To evaluate connected coverage, we introduced the term
cluster size, which is the expected value of the area covered by a clusterhead together
with sensor nodes connected to it. We derived formulas for the cluster size and validated
them by computer simulations. By using the cluster size formulas, we proposed
a method to dimension a WSN for given targeted connected coverage.
Furthermore, we formulated cost optimization problems for direct and multi-hop
communication cases. These formulations utilize not only cluster size formulas but also
the well-connectivity concept. We suggested some search heuristics to solve these optimization
problems. Additionally, we justified that, in practical cases, node heterogeneity
can provide lower cost solutions. We also investigated the lifetime of WSNs and for
mulated a cost optimization problem with connected coverage and lifetime constraints.
By solving this optimization problem, one can determine the number of nodes of each
type and the initial energies of each type of node that leads to lowest cost solution while
satisfying the minimum connected coverage and minimum lifetime requirements.
47
Andresen, Christian André. "Properties of fracture networks and other network systems". Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for fysikk, 2009. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-5074.
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Chaltseva, Anna. "Network state estimation in wireless multi-hop networks". Licentiate thesis, Luleå tekniska universitet, Datavetenskap, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-26357.
Testo completoAbstract (sommario):
Multi-hop wireless networks in general and those built upon IEEE 802.11 standard in particular are known for their highly dynamic and unstable performance. The commonly accepted way for improving the situation is to jointly optimize the performance of protocols across different communications layers. Being able to characterize a state of the network is essential to enable the cross-layer optimization. This licentiate thesis investigates methods for passive characterization of network state at medium access control and transport layers based on information accessible from the corresponding layers below.Firstly, the thesis investigates a possibility for characterizing traffic intensity relying solely on the statistics of measurements from the physical layer. An advantage of this method is that it does not require decoding of the captured packets, by this accounting for the effect from long-range interferences introduced by transmissions at the border of the communication range of a receiver.Secondly, a question of predicting TCP throughput over a multi-hop wireless path is addressed. The proposed predictor is a practically usable function of statistically significant parameters at transport, medium access control and physical communication layers. The presented model is able to predict the TCP throughput with 99% accuracy, which provides an essential input for various cross-layer optimization processes.Finally, during the course of the experimental work the issues of accuracy of simulation-based modeling of communication processes were investigated. The thesis is concluded by presenting a comparative study of the performance characteristics measured in a single channel multi-hop wireless network test-bed and the corresponding measurements obtained from popular network simulators ns-2 and ns-3 when configured with identical settings. The thesis presents the evaluation of the mismatch between the results obtained in the test-bed and the simulators with their standard empirical radio models.Godkänd; 2012; 20111215 (anncha); LICENTIATSEMINARIUM Ämnesområde: Datorkommunikation/Computer Networking Examinator: Docent Evgeny Osipov, Institutionen för system- och rymdteknik, Luleå tekniska universitet Diskutant: Universitetslektor Olov Schelén, Luleå tekniska universitet samt Xarepo AB, Luleå Tid: Måndag den 20 februari 2012 kl 10.00 Plats: A1514 Demostudion, Luleå tekniska universitet
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Fan, Bo Electrical Engineering & Telecommunications Faculty of Engineering UNSW. "Sharing network measurements on peer-to-peer networks". Publisher:University of New South Wales. Electrical Engineering & Telecommunications, 2007. http://handle.unsw.edu.au/1959.4/40762.
Testo completoAbstract (sommario):
With the extremely rapid development of the Internet in recent years, emerging peer-to-peer network overlays are meeting the requirements of a more sophisticated communications environment, providing a useful substrate for applications such as scalable file sharing, data storage, large-scale multicast, web-cache, and publish-subscribe services. Due to its design flexibility, peer-to-peer networks can offer features including self-organization, fault-tolerance, scalability, load-balancing, locality and anonymity. As the Internet grows, there is an urgent requirement to understand real-time network performance degradation. Measurement tools currently used are ping, traceroute and variations of these. SNMP (Simple Network Management Protocol) is also used by network administrators to monitor local networks. However, ping and traceroute can only be used temporarily, SNMP can only be deployed at certain points in networks and these tools are incapable of sharing network measurements among end-users. Due to the distributed nature of networking performance data, peer-to-peer overlay networks present an attractive platform to distribute this information among Internet users. This thesis aims at investigating the desirable locality property of peer-to-peer overlays to create an application to share Internet measurement performance. When measurement data are distributed amongst users, it needs to be localized in the network allowing users to retrieve it when external Internet links fail. Thus, network locality and robustness are the most desirable properties. Although some unstructured overlays also integrate locality in design, they fail to reach rarely located data items. Consequently, structured overlays are chosen because they can locate a rare data item deterministically and they can perform well during network failures. In structured peer-to-peer overlays, Tapestry, Pastry and Chord with proximity neighbour selection, were studied due to their explicit notion of locality. To differentiate the level of locality and resiliency in these protocols, P2Psim simulations were performed. The results show that Tapestry is the more suitable peer-to-peer substrate to build such an application due to its superior localizing data performance. Furthermore, due to the routing similarity between Tapestry and Pastry, an implementation that shares network measurement information was developed on freepastry, verifying the application feasibility. This project also contributes to the extension of P2Psim to integrate with GT-ITM and link failures.
50
Yuan, Fenghua. "Lightweight network management design for wireless sensor networks". Online access for everyone, 2007. http://www.dissertations.wsu.edu/Thesis/Fall2007/F_Yuan_081307.pdf.
Testo completo