30 research outputs found
Dimensionamento de redes ópticas multicamada
Doutoramento em Engenharia ElectrónicaEste trabalho apresenta um estudo sobre o dimensionamento
de redes ópticas, com vistas a obter um modelo de
dimensionamento para redes de transporte sobreviventes.
No estudo utilizou-se uma abordagem estatística em detrimento
à determinística.
Inicialmente, apresentam-se as principais tecnologias e
diferentes arquitecturas utilizadas nas redes ópticas de
transporte. Bem como os principais esquemas de sobrevivência
e modos de transporte.
São identificadas variáveis necessárias e apresenta-se um
modelo dimensionamento para redes de transporte, tendo-se
dado ênfase às redes com topologia em malha e considerando
os modos de transporte opaco, transparente e translúcido.
É feita uma análise rigorosa das características das topologias
de redes de transporte reais, e desenvolve-se um gerador de
topologias de redes de transporte, para testar a validade dos
modelos desenvolvidos. Também é implementado um algoritmo
genético para a obtenção de uma topologia optimizada para um
dado tráfego.
São propostas expressões para o cálculo de variáveis não
determinísticas, nomeadamente, para o número médio de
saltos de um pedido, coeficiente de protecção e coeficiente
de restauro. Para as duas últimas, também é analisado o
impacto do modelo de tráfego. Verifica-se que os resultados
obtidos pelas expressões propostas são similares às obtidas
por cálculo numérico, e que o modelo de tráfego não influencia
significativamente os valores obtidos para os coeficientes.
Finalmente, é demonstrado que o modelo proposto é útil para o
dimensionamento e cálculo dos custos de capital de redes com
informação incompleta.This work presents a study on the dimensioning of optical
networks, aiming to obtain a dimensioning model for survivable
optical transport networks. The study relies on a statistical
approach rather than a deterministic approach.
Initially, enabling technologies and different architectures usually
employed in optical transport networks are presented. The main
survivability schemes and transport modes are also presented.
Useful variables are identified and a transport network
dimensioning model is presented, with emphasis on mesh-based
network topologies, and considering opaque, transparent and
translucent transport modes.
A rigorous analysis on the characteristics of real-world transport
networks is done, and a topology generator is developed.
The topology generator is used for testing and validating the
developed models. A genetic algorithm for obtaining an optimized
topology for a given traffic load is implemented as well.
Expressions for calculating non-deterministic variables are
proposed, namely for the average number of hops per demand,
protection and restoration coefficient. For the last two, the impact
of the traffic model was analyzed. It is shown that results
obtained from the proposed expressions are quite similar to the
ones obtained from numeric calculation. Moreover, the traffic
model does not influence significantly the values obtained for the
coefficients.
Finally, it is shown that the proposed model is useful for the
dimensioning and calculation of capital expenditures of networks
in absence of complete information.FCT - SFRH/BD/27545/200
Telecommunication Systems
This book is based on both industrial and academic research efforts in which a number of recent advancements and rare insights into telecommunication systems are well presented. The volume is organized into four parts: "Telecommunication Protocol, Optimization, and Security Frameworks", "Next-Generation Optical Access Technologies", "Convergence of Wireless-Optical Networks" and "Advanced Relay and Antenna Systems for Smart Networks." Chapters within these parts are self-contained and cross-referenced to facilitate further study
Solar gamma ray monitor for OSO-H (0.3-10 MeV)
A gamma ray experiment to be flown aboard the OSO-7 spacecraft is described along with a history of the development of the experiment, a description of the gamma ray detector and its operation, and a short preliminary review of the scientific information obtained during the instruments' lifetime. The gamma ray detector operated an average of 18 hours a day for approximately 15 months. The majority of the data was collected in the solar and antisolar direction, but data at right angles to the spacecraft-sun line was also accumulated. In all, at least two full scans of the celestial sphere were completed
Differentiated quality-of-recovery and quality-of-protection in survivable WDM mesh networks
In the modern telecommunication business, there is a need to provide different Quality-of-Recovery (QoR) and Quality-of-Protection (QoP) classes in order to accommodate as many customers as possible, and to optimize the protection capacity cost. Prevalent protection methods to provide specific QoS related to protection are based on pre-defined shape protection structures (topologies), e.g., p -cycles and p -trees. Although some of these protection patterns are known to provide a good trade-off among the different protection parameters, their shapes can limit their deployment in some specific network conditions, e.g., a constrained link spare capacity budget and traffic distribution. In this thesis, we propose to re-think the design process of protection schemes in survivable WDM networks by adopting a hew design approach where the shapes of the protection structures are decided based on the targeted QoR and QoP guarantees, and not the reverse. We focus on the degree of pre-configuration of the protection topologies, and use fully and partially pre-cross connected p -structures, and dynamically cross connected p -structures. In QoR differentiation, we develop different approaches for pre-configuring the protection capacity in order to strike different balances between the protection cost and the availability requirements in the network; while in the QoP differentiation, we focus on the shaping of the protection structures to provide different grades of protection including single and dual-link failure protection. The new research directions proposed and developed in this thesis are intended to help network operators to effectively support different Quality-of-Recovery and Quality-of-Protection classes. All new ideas have been translated into mathematical models for which we propose practical and efficient design methods in order to optimize the inherent cost to the different designs of protection schemes. Furthermore, we establish a quantitative relation between the degree of pre-configuration of the protection structures and their costs in terms of protection capacity. Our most significant contributions are the design and development of Pre-Configured Protection Structure (p-structure) and Pre-Configured Protection Extended-Tree (p -etree) based schemes. Thanks to the column generation modeling and solution approaches, we propose a new design approach of protection schemes where we deploy just enough protection to provide different quality of recovery and protection classe
Modelling, Dimensioning and Optimization of 5G Communication Networks, Resources and Services
This reprint aims to collect state-of-the-art research contributions that address challenges in the emerging 5G networks design, dimensioning and optimization. Designing, dimensioning and optimization of communication networks resources and services have been an inseparable part of telecom network development. The latter must convey a large volume of traffic, providing service to traffic streams with highly differentiated requirements in terms of bit-rate and service time, required quality of service and quality of experience parameters. Such a communication infrastructure presents many important challenges, such as the study of necessary multi-layer cooperation, new protocols, performance evaluation of different network parts, low layer network design, network management and security issues, and new technologies in general, which will be discussed in this book
Enabling Technology in Optical Fiber Communications: From Device, System to Networking
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
Experimental and numerical analyses on the behavior of civil and marine steel structures
Bolts and welds in combination occur most commonly during the construction phase of a building when the design load changes, when there are unforeseen difficulties in make-up or matching of bolt holes, or in retrofit of existing structures. Due to the different load-displacement behavior of the bolts and welds, the behavior of the combination connections may change in different conditions. Pretensioned high-strength bolts and longitudinal fillet welds in combination has been studied both experimentally and numerically. Slip-dependent surface frictional and ductile fracture models have been incorporated in the numerical analysis to address the strain compatibility between bolts and welds. Effects of critical variables, e.g., bolt pattern, faying surface, weld size, weld location, and weld/bolt strength ratio have simulated and discussed. Similarly, the fatigue behavior of stiffened panels under variable amplitude loading has been investigated. These panels are commonly found in steel structures, such as naval vessels and bridges subjected to random variable loading. An experimental fatigue test was conducted for the stiffened box girder under variable amplitude loading. An XFEM-based fatigue crack prediction approach was proposed based on the crack closure concept. Prediction were made using the proposed approach considering the loading history effect as well as stiffener effect, and residual stresses due to welding