8 research outputs found

    Enabling Technology in Optical Fiber Communications: From Device, System to Networking

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    This book explores the enabling technology in optical fiber communications. It focuses on the state-of-the-art advances from fundamental theories, devices, and subsystems to networking applications as well as future perspectives of optical fiber communications. The topics cover include integrated photonics, fiber optics, fiber and free-space optical communications, and optical networking

    New Models and Algorithms in Telecommunication Networks

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    The telecommunications industry is growing very fast and frequently faces technological developments. Due to the competition between service providers and high expected reliability from their customers, they should be able first, to migrate their networks to the novel advancements in order to be able to meet their customers’ latest requirements and second, to optimally use the resources in order to maximize their profitability. Many researchers have studied different scenarios for Network Migration Problem (NMP). In these studies, a comparison between the legacy and new technologies is investigated in terms of time frames, reduction in expenditures, revenue increases, etc. There have been no prior studies considering the operational costs of NMP e.g., technicians, engineers and travels. The first contribution of the thesis is to propose a two-phase algorithm based on the solution of column generation models that builds a migration plan with minimum overall migration time or cost. The second contribution is an improved decomposition model for NMP by removing the symmetry between the network connections. We apply a branch-and-price algorithm in order to obtain an epsolin-optimal ILP solution. The third contribution of the thesis is to propose a new methodology for Wavelength Defragmentation Problem to recover the capacity of WDM networks in dynamic environments and optimize resource usages. Since rerouting the lightpaths in an arbitrary order may result in a huge number of disruptions, an algorithm based on a nested column generation technique is proposed. The solution is an optimized configuration in terms of resource usage (number of links) that is reachable by no disruptions from the current provisioning. All the algorithms presented in this thesis are based on Column Generation method, a decomposition framework to tackle large-scale optimization problems

    Efficiency and fairness in an elastic optical network under heavy traffic

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    Orientador: Helio WaldmanDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de ComputaçãoResumo: O crescimento do tráfego na rede mundial de computadores tem impulsionado a pesquisa em tecnologias que consigam usar a infraestrutura já instalada da forma mais eficiente possível. Essa infraestrutura é, em maior parte, composta de fibra óptica. Para aumentar sua eficiência foi proposta uma nova geração de redes ópticas, chamadas redes elásticas, que adotam um paradigma flexível de ocupação do espectro óptico aumentando substancialmente seu aproveitamento. Contudo, um ambiente heterogêneo no qual diferentes classes de tráfego convivem pode levar a uma competição e discriminação de algumas classes em detrimento de outras. Neste trabalho estudamos políticas de alocação espectral que visam garantir um eficiente uso da banda óptica, mantendo uma alta ocupação do espectro e eliminando a discriminação entre classes de acesso em uma rede sob alta carga de tráfegoAbstract: The traffic growth in the global computer network has driven the research on technologies that are able to use the infrastructure already installed as efficiently as possible. This infrastructure is, for the most part, composed of optical networks. In order to increase its efficiency, a new generation of optical networks, called elastic networks, was proposed adopting a flexible paradigm of optical spectrum occupancy, substantially increasing its utilization. However, a heterogeneous environment where different classes of traffic coexist can lead to competition and discrimination of some classes to the detriment of others. This work studies spectral allocation policies aimed at guaranteeing an efficient use of the optical bandwidth, maintaining a high spectral occupation and eliminating the discrimination between access classes in a network under a heavy trafficMestradoTelecomunicações e TelemáticaMestre em Engenharia Elétrica1554016CAPE

    Fairness versus efficiency in spectrum allocation on elastic optical networks

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    Orientador: Helio WaldmanDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de ComputaçãoResumo: O crescimento do tráfego na rede mundial de computadores tem impulsionado a pesquisa em tecnologias que consigam usar a infraestrutura já instalada da forma mais eficiente possível. Essa infraestrutura é, em maior parte, composta de fibra óptica. Para aumentar sua eficiência, foi proposto que a próxima geração de redes ópticas se utilize do paradigma flexível, que aumenta o aproveitamento do espectro em até 40%. Entretanto, a alocação eficiente de recursos gera diversos problemas, entre eles, a discriminação de classes de acesso para tráfego multiclasses. Dessa forma, nesse trabalho, as políticas de alocação espectral que visam a eliminação da discriminação de classes são estudadas e seu desempenho comparado com as políticas que visam somente a eficiência. Assim, o estudo apresenta uma análise quantitativa do trade-off entre eficiência espectral e imparcialidade na alocação espectral. Os resultados apontam que o uso de imparcialidade pode gerar ganho no tráfego total agregado médio de um sistema óptico para certas configurações e em carga de tráfego altaAbstract: The traffic growth on the global computer network have been boosting the research on technologies that are able to use the installed infrastructure in the most efficient way. This infrastructure is, in most part, composed by optical fiber. To improve its efficiency, it was proposed that the next generation of optical networks uses the flexible paradigm, which improves the spectrum use by up to 40%. However, the efficient use of resources generates several problems, between them, the discrimination of access classes on multiclass traffic. Thus, on this work, the spectrum allocation policies that aim to end the discrimination of classes are studied and their performance are compared with the policies that aim only efficiency. Therefore, the study presents a quantitative analysis on the trade-off between spectral efficiency and fairness on spectrum allocation. The obtained results showed that, by applying fairness in the spectrum allocation, the mean total throughput of the network can be increased for certain settings and high traffic loadMestradoTelecomunicações e TelemáticaMestre em Engenharia Elétrica159677/2015-7CNP

    Next generation control of transport networks

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    It is widely understood by telecom operators and industry analysts that bandwidth demand is increasing dramatically, year on year, with typical growth figures of 50% for Internet-based traffic [5]. This trend means that the consumers will have both a wide variety of devices attaching to their networks and a range of high bandwidth service requirements. The corresponding impact is the effect on the traffic engineered network (often referred to as the “transport network”) to ensure that the current rate of growth of network traffic is supported and meets predicted future demands. As traffic demands increase and newer services continuously arise, novel network elements are needed to provide more flexibility, scalability, resilience, and adaptability to today’s transport network. The transport network provides transparent traffic engineered communication of user, application, and device traffic between attached clients (software and hardware) and establishing and maintaining point-to-point or point-to-multipoint connections. The research documented in this thesis was based on three initial research questions posed while performing research at British Telecom research labs and investigating control of transport networks of future transport networks: 1. How can we meet Internet bandwidth growth yet minimise network costs? 2. Which enabling network technologies might be leveraged to control network layers and functions cooperatively, instead of separated network layer and technology control? 3. Is it possible to utilise both centralised and distributed control mechanisms for automation and traffic optimisation? This thesis aims to provide the classification, motivation, invention, and evolution of a next generation control framework for transport networks, and special consideration of delivering broadcast video traffic to UK subscribers. The document outlines pertinent telecoms technology and current art, how requirements I gathered, and research I conducted, and by which the transport control framework functional components are identified and selected, and by which method the architecture was implemented and applied to key research projects requiring next generation control capabilities, both at British Telecom and the wider research community. Finally, in the closing chapters, the thesis outlines the next steps for ongoing research and development of the transport network framework and key areas for further study

    Control plane routing in photonic networks

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    The work described in the thesis investigates the features of control plane functionality for routing wavelength paths to serve a set of sub-wavelength demands. The work takes account of routing problems only found in physical network layers, notably analogue transmission impairments. Much work exists on routing connections for dynamic Wavelength-Routed Optical Networks (WRON) and to demonstrate their advantages over static photonic networks. However, the question of how agile the WRON should be has not been addressed quantitatively. A categorization of switching speeds is extended, and compared with the reasons for requiring network agility. The increase of effective network capacity achieved with increased agility is quantified through new simulations. It is demonstrated that this benefit only occurs within a certain window of network fill; achievement of significant gain from a more-agile network may be prevented by the operator’s chosen tolerable blocking probability. The Wavelength Path Sharing (WPS) scheme uses semi-static wavelengths to form unidirectional photonic shared buses, reducing the need for photonic agility. Making WPS more practical, novel improved routing algorithms are proposed and evaluated for both execution time and performance, offering significant benefit in speed at modest cost in efficiency. Photonic viability is the question of whether a path that the control plane can configure will work with an acceptable bit error rate (BER) despite the physical transmission impairments encountered. It is shown that, although there is no single approach that is simple, quick to execute and generally applicable at this time, under stated conditions approximations may be made to achieve a general solution that will be fast enough to enable some applications of agility. The presented algorithms, analysis of optimal network agility and viability assessment approaches can be applied in the analysis and design of future photonic control planes and network architectures
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