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Tesi sul tema "Network"
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1
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
2
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
3
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.
4
Rivas, Antonio Canales. "Network management using active networks". Thesis, De Montfort University, 2006. http://hdl.handle.net/2086/4781.
Testo completo
5
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.
6
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
7
Post, David L. "Network Management: Assessing Internet Network-Element Fault Status Using Neural Networks". Ohio : Ohio University, 2008. http://www.ohiolink.edu/etd/view.cgi?ohiou1220632155.
Testo completo
8
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.
9
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."
10
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.
11
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.
12
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.
13
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.
14
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
15
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.
16
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
17
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
18
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.
19
O'Brien, Mariana G. "Epistemology and networked governance| An actor-network approach to network governance". Thesis, Florida Atlantic University, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=3730734.
Testo completoAbstract (sommario):
This dissertation suggests that network governance theory may have reached an impasse, and in order to pursue its advance, new methods need to be used. It tests the viability of actor-network theory on providing new insights on network governance, which could contribute to the strengthening of network governance theory. The author suggests that actor-network theory may offer both an epistemology and ontology that intents to not impose current definitions and divisions of traditional social science. By doing so, actor-network theory focuses on the performance of associations rather than on the traditional categories of structures, institutions, individuals or groups — characteristic of most network governance studies.
This study tests the viability of actor-network theory in a complex international environmental policy network in the Andean Amazon. It employs Latour’s three-movement method of deployment of controversies, rendering associations traceable again, and reassembling governance. The methodological strategy provides a clean slate to search for a new perspective of network governance, which is based on participants’ perspectives. It is found that associations are established among programs, projects, public policies, among others; and that this associations seem to remain even if organizations, programs, and projects leave the network. Actor-networks’ roles in network governance appear to be not static, and their degree of affiliation ranges from formal to informal associations.
Applying actor-network theory in the study of network governance suggests that action is dislocated, and that groups are in continuous formation. Groups’ boundaries are define and redefine based on participants’ perspectives and associations. Finally, a discussion in regards to the implications of this research for both network governance and actor-network theory is offered.
20
Liu, Guanglei. "Management and Control of Scalable and Resilient Next-Generation Optical Networks". Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/14610.
Testo completoAbstract (sommario):
Two research topics in next-generation optical networks with wavelength-division multiplexing (WDM) technologies were investigated: (1) scalability of network management and control, and (2) resilience/reliability of networks upon faults and attacks.
In scalable network management, the scalability of management information for inter-domain light-path assessment was studied. The light-path assessment was formulated as a decision problem based on decision theory and probabilistic graphical models. It was found that partial information available can provide the desired performance, i.e., a small percentage of erroneous decisions can be traded off to achieve a large saving in the amount of management information.
In network resilience under malicious attacks, the resilience of all-optical networks under in-band crosstalk attacks was investigated with probabilistic graphical models. Graphical models provide an explicit view of the spatial dependencies in attack propagation, as well as computationally efficient approaches, e.g., sum-product algorithm, for studying network resilience. With the proposed cross-layer model of attack propagation, key factors that affect the resilience of the network from the physical layer and the network layer were identified. In addition, analytical results on network resilience were obtained for typical topologies including ring, star, and mesh-torus networks.
In network performance upon failures, traffic-based network reliability was systematically studied. First a uniform deterministic traffic at the network layer was adopted to analyze the impacts of network topology, failure dependency, and failure protection on network reliability. Then a random network layer traffic model with Poisson arrivals was applied to further investigate the effect of network layer traffic distributions on network reliability. Finally, asymptotic results of network reliability metrics with respect to arrival rate were obtained for typical network topologies under heavy load regime.
The main contributions of the thesis include: (1) fundamental understandings of scalable management and resilience of next-generation optical networks with WDM technologies; and (2) the innovative application of probabilistic graphical models, an emerging approach in machine learning, to the research of communication networks.
21
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.
22
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.
23
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.
25
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.
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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.
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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
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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
35
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.
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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.
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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.
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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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Kumar, Abhishek. "Network Data Streaming: Algorithms for Network Measurement and Monitoring". Diss., Available online, Georgia Institute of Technology, 2005, 2005. http://etd.gatech.edu/theses/available/etd-11172005-143837/.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--Computing, Georgia Institute of Technology, 2006.Dr. Mostafa Ammar, Committee Member ; Dr. Mark Crovella, Committee Member ; Dr. Constantinos Dovrolis, Committee Member ; Dr. Ellen Zegura, Committee Chair ; Dr. Jun Xu, Committee Chair. Vita. Includes bibliographical references.
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Brande, Julia K. Jr. "Computer Network Routing with a Fuzzy Neural Network". Diss., Virginia Tech, 1997. http://hdl.handle.net/10919/29685.
Testo completoAbstract (sommario):
The growing usage of computer networks is requiring improvements in network technologies and management techniques so users will receive high quality service. As more individuals transmit data through a computer network, the quality of service received by the users begins to degrade. A major aspect of computer networks that is vital to quality of service is data routing. A more effective method for routing data through a computer network can assist with the new problems being encountered with today's growing networks.
Effective routing algorithms use various techniques to determine the most appropriate route for transmitting data. Determining the best route through a wide area network (WAN), requires the routing algorithm to obtain information concerning all of the nodes, links, and devices present on the network. The most relevant routing information involves various measures that are often obtained in an imprecise or inaccurate manner, thus suggesting that fuzzy reasoning is a natural method to employ in an improved routing scheme. The neural network is deemed as a suitable accompaniment because it maintains the ability to learn in dynamic situations. Once the neural network is initially designed, any alterations in the computer routing environment can easily be learned by this adaptive artificial intelligence method. The capability to learn and adapt is essential in today's rapidly growing and changing computer networks. These techniques, fuzzy reasoning and neural networks, when combined together provide a very effective routing algorithm for computer networks.
Computer simulation is employed to prove the new fuzzy routing algorithm outperforms the Shortest Path First (SPF) algorithm in most computer network situations. The benefits increase as the computer network migrates from a stable network to a more variable one. The advantages of applying this fuzzy routing algorithm are apparent when considering the dynamic nature of modern computer networks.Ph. D.
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Alexander, David. "A Network Metadata Infrastructure for Locating Network Devices". Ohio University / OhioLINK, 2004. http://www.ohiolink.edu/etd/view.cgi?ohiou1088176648.
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Naidoo, Vaughn. "Policy Based Network management of legacy network elements in next generation networks for Voice Services". Thesis, University of the Western Cape, 2002. http://etd.uwc.ac.za/index.php?module=etd&action=viewtitle&id=gen8Srv25Nme4_5830_1370595582.
Testo completo
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Habib, Farooq. "Interplay between network configurations and network governance mechanisms in supply networks a systematic literature review". Thesis, Cranfield University, 2012. http://dspace.lib.cranfield.ac.uk/handle/1826/7879.
Testo completoAbstract (sommario):
Purpose: This work systematically reviews the extant academic management literature on supply networks. It specifically examines how network configurations and network governance mechanisms influence each other in supply networks.
Design: 125 analytical and empirical studies were identified using an evidence-based approach to review the literature mainly published between 1985 and 2012.
Synthesis: Drawing on a multi-disciplinary theoretical foundation, this work develops an integrative framework to identify three distinct yet interdependent themes that characterize the study of supply networks: a) Network Configurations (structures and relationships); b) Network Governance Mechanisms (formal and informal); and c) The Interplay between Network Configurations and Network Governance Mechanisms.
Findings: Network configurations and network governance mechanisms mutually influence each other and cannot be considered in isolation. Formal and informal governance mechanisms provide better control when used as complements rather than as substitutes. The choice of governance mechanism depends on the nature of exchange; role of management; desired level of control; level of flexibility in formal contracts; and complementary role of formal and informal governance mechanism.
Research implications: This nascent field has thematic and methodological research opportunities for academics. Comparative network analysis using longitudinal case studies offers a rich area for further study.
Practical Implications: The complexity surrounding the conflicting roles of managers at the organisation and network levels poses a significant challenge during the development and implementation stage of strategic network policies.
Originality/value: This review reveals that formal and informal governance mechanisms provide better control when used as complements rather than as substitutes.
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Khorramzadeh, Yasamin. "Network Reliability: Theory, Estimation, and Applications". Diss., Virginia Tech, 2015. http://hdl.handle.net/10919/64383.
Testo completoAbstract (sommario):
Network reliability is the probabilistic measure that determines whether a network remains functional when its elements fail at random. Definition of functionality varies depending on the problem of interest, thus network reliability has much potential as a unifying framework to study a broad range of problems arising in complex network contexts. However, since its introduction in the 1950's, network reliability has remained more of an interesting theoretical construct than a practical tool. In large part, this is due to well-established complexity costs for both its evaluation and approximation, which has led to the classification of network reliability as a NP-Hard problem. In this dissertation we present an algorithm to estimate network reliability and then utilize it to evaluate the reliability of large networks under various descriptions of functionality.
The primary goal of this dissertation is to pose network reliability as a general scheme that provides a practical and efficiently computable observable to distinguish different networks. Employing this concept, we are able to demonstrate how local structural changes can impose global consequences. We further use network reliability to assess the most critical network entities which ensure a network's reliability. We investigate each of these aspects of reliability by demonstrating some example applications.Ph. D.
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鄧沛權 e Pui-kuen Tang. "Business network: network marketing : analysis of network marketing using business network theories". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1997. http://hub.hku.hk/bib/B31268316.
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Tang, Pui-kuen. "Business network : network marketing : analysis of network marketing using business network theories /". Hong Kong : University of Hong Kong, 1997. http://sunzi.lib.hku.hk/hkuto/record.jsp?B18840127.
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Avidan, Lenoy. "Dynamic Shifting of Virtual Network Topologies for Network Attack Prevention". DigitalCommons@CalPoly, 2019. https://digitalcommons.calpoly.edu/theses/1986.
Testo completoAbstract (sommario):
Computer networks were not designed with security in mind, making research into the subject of network security vital. Virtual Networks are similar to computer networks, except the components of a Virtual Network are in software rather than hardware. With the constant threat of attacks on networks, security is always a big concern, and Virtual Networks are no different. Virtual Networks have many potential attack vectors similar to physical networks, making research into Virtual Network security of great importance. Virtual Networks, since they are composed of virtualized network components, have the ability to dynamically change topologies. In this paper, we explore Virtual Networks and their ability to quickly shift their network topology. We investigate the potential use of this flexibility to protect network resources and defend against malicious activities.
To show the ability of reactively shifting a Virtual Network’s topology to se- cure a network, we create a set of four experiments, each with a different dynamic topology shift, or “dynamic defense”. These four groups of experiments are called the Server Protection, Isolated Subnet, Distributed Port Group, and Standard Port Group experiments. The Server Protection experiments involve detecting an attack against a server and shifting the server behind a protected subnet. The other three sets of experiments, called Attacker Prevention experiments, involve detecting a malicious node in the internal network and initiating a dynamic de- fense to move the attacker behind a protected subnet. Each Attacker Prevention experiment utilizes a different dynamic defense to prevent the malicious node from attacking the rest of the Virtual Network. For each experiment, we run 6 different network attacks to validate the effectiveness of the dynamic defenses. The network attacks utilized for each experiment are ICMP Flooding, TCP Syn Flooding, Smurf attack, ARP Spoofing, DNS Spoofing, and NMAP Scanning. Our validation shows that our dynamic defenses, outside of the standard port group, are very effective in stopping each attack, consistently lowering the at- tacks’ success rate significantly. The Standard Port Group was the one dynamic defense that is ineffective, though there are also a couple of experiments that could benefit from being run with more attackers and with different situations to fully understand the effectiveness of the defenses. We believe that, as Virtual Networks become more common and utilized outside of data centers, the ability to dynamically shift topology can be used for network security purposes.