1,135 research outputs found

    Optimization in Telecommunication Networks

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    Network design and network synthesis have been the classical optimization problems intelecommunication for a long time. In the recent past, there have been many technologicaldevelopments such as digitization of information, optical networks, internet, and wirelessnetworks. These developments have led to a series of new optimization problems. Thismanuscript gives an overview of the developments in solving both classical and moderntelecom optimization problems.We start with a short historical overview of the technological developments. Then,the classical (still actual) network design and synthesis problems are described with anemphasis on the latest developments on modelling and solving them. Classical results suchas Menger’s disjoint paths theorem, and Ford-Fulkerson’s max-flow-min-cut theorem, butalso Gomory-Hu trees and the Okamura-Seymour cut-condition, will be related to themodels described. Finally, we describe recent optimization problems such as routing andwavelength assignment, and grooming in optical networks.operations research and management science;

    Availability Constrained Routing And Wavelength Assignment And Survivability In Optical Wdm Networks

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    Tez (Doktora) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2009Thesis (PhD) -- İstanbul Technical University, Institute of Science and Technology, 2009Bu çalışmada, optik ağlarda kullanılabilirlik kısıtı altında yol ve dalgaboyu atama konusu farklı sürdürülebilirlik politikaları altında çalışılmış ve elde edilen sonuçlar benzetim aracılığıyla doğrulanarak sunulmuştur. Öncelikle paylaşılan yol koruması altında sınırsız kaynak bulunması durumunda kullanılabilirlik kısıtı altında yol ve dalgaboyu atamaya yönelik planlama amaçlı bağlantı kurma yöntemleri sezgisel ve optimizasyona dayalı olarak önerilmiştir. Sonrasında bu teknikler kısıtlı kaynak altında ve farklılaştırılmış kullanılabilirlik düzeyi gereksinimleri ile gelen bağlantı isteklerinin olması koşulu altında çalışabilecek şekilde adapte edilmiş ve başarımları sınanmıştır. Önerilen tekniklerin literatürde yaygın olarak bilinen bağlantı kurma tekniklerinin başarımını bağlantı düşürme olasılığı ve bağlantı kullanılabilirliği açısından yükselttiği, bunun yanında yedek kaynak tüketim fazlasını da gözeterek kabul edilir bir düzeyde tuttuğu gözlenmiştir. Özellikle optimizasyon tabanlı bağlantı kurma tekniğinin, farklılaştırılmış bağlantı isteklerinin bulunduğu ortamda kaynak tüketimini de düşürdüğü gösterilmiştir. Son olarak da, segmanlı koruma için önceden önerilmiş bir kullanılabilirlik analizine rastlanamadığı için, paylaşılan segmanlı koruma için kullanılabilirlik analizi yöntemi önerilerek benzetim aracılığıyla doğrulanmıştır. Bu analiz kullanılarak da segmanlı koruma altında kullanılabilirliği gözeten yol ve dalgaboyu atama yöntemleri oluşturularak başarımları kaynak kısıtlı ve kaynakça zengin ortamlarda denenerek uygulanabilirlikleri belirlenmiştir.In this study, we have proposed availability aware routing and wavelength assignment schemes for optical networks under different survivability policies. The proposed techniques are evaluated by simulation. First, we have proposed heuristic and optimization driven connection provisioning schemes under shared backup path protection in resource plentiful environment. Then, the proposed schemes are modified to work in resource limited environment where connections arrive with differentiated availability requirements. The proposed techniques are compared to a conventional reliable connection provisioning algorithm. The simulation results show that the proposed techniques lead to lower connection blocking probability and better connection availability. Besides this, it is also shown that the proposed techniques also keep the resource overbuild due to protection in a feasible range. Moreover, the experimental results also show that the optimization driven technique leads to a decreased resource overbuild under resource limited environment for connection arrivals with differentiated availability requirements. The last part of this work deals with shared segment protection. Since there is no specific availability analysis method for shared segment protection, an availability analysis method for this protection scheme is proposed and validated by simulation. Based on this analysis, availability aware connection provisioning schemes are constructed, their performance is evaluated in resource plentiful and resource scarce environments, and the applicability of the schemes are determined in terms of environmental constraints.DoktoraPh

    Survivable mesh-network design & optimization to support multiple QoP service classes

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    Every second, vast amounts of data are transferred over communication systems around the world, and as a result, the demands on optical infrastructures are extending beyond the traditional, ring-based architecture. The range of content and services available from the Internet is increasing, and network operations are constantly under pressure to expand their optical networks in order to keep pace with the ever increasing demand for higher speed and more reliable links

    Heuristic for the design of fault tolerant logical topology.

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    Wavelength division multiplexing (WDM) in optical fiber networks is widely viewed as the savior for its potential to satisfy the huge bandwidth requirement of network users. Optical cross connect (OCX) in WDM network facilitates the switching of signal on any wavelength from any input port to any output port. As a result, it is possible to establish ligthpaths between any pair of nodes. The set of lightpaths established over fiber links defines logical topology. In our thesis, we proposed a heuristic approach for the design of fault tolerant logical topology. Our design approach generalizes the design protection concept and enforces wavelength continuity constraint in a multi-hop optical network. In our work, we first designed logical topology for fault free state of the network. We, then, added additional lightpaths for each single link failure scenario. Numerical results clearly show that our approach outperforms Shared path protection and Dedicated path protection. Our simulation result shows that our approach is feasible for large networks. (Abstract shortened by UMI.) Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis2005 .S24. Source: Masters Abstracts International, Volume: 44-03, page: 1413. Thesis (M.Sc.)--University of Windsor (Canada), 2005

    Survivable network design with stepwise incremental cost function

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    Modern society has become more and more dependent on information services, transferred in both public and private network, than ever before. The use of integration of computers with telecommunications has created a so-called “Information Age”. The advent of high capacity digital telecommunication facilities has made it possible for the huge amount of traffic to be carried in an economical and efficient method, in recent years. These facilities, which are used to carry much higher capacities than the traditional ones, also result in the network’s vulnerability to the failure of network facilities, i.e. a single link failure. This thesis is concerned with the technology by which the spare capacity on the link of mesh networks is placed in order to protect the active traffic from network failure with a minimal cost. Although there have been many works to address the issue all of these works have been developed based on the assumption that the link cost with its capacity is linear. In fact, the linear cost functions does not reflect the reality that optic fiber cables with the specific amount of capacities are only available, in other words, the link cost function is stepwise rather than linear. Therefore, all existing algorithms developed for the linear assumption may not be applicable properly for the stepwise case. A novel heuristic algorithm is proposed to solve the problem in this thesis. The algorithm is composed of two parts as follows. In part one, a maximum flow algorithm is employed to work out the maximal amount of feasible spare paths consisting of spare capacities in the network to re-route the disrupted traffic at the event of network failure. In part two, a newly proposed algorithm is used to find an alternative path on which to place the non-rerouted traffic on the failed link with the minimum network cost increment. The superiority of the algorithm is presented over other algorithms published in this area

    Autonomously Reconfigurable Artificial Neural Network on a Chip

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    Artificial neural network (ANN), an established bio-inspired computing paradigm, has proved very effective in a variety of real-world problems and particularly useful for various emerging biomedical applications using specialized ANN hardware. Unfortunately, these ANN-based systems are increasingly vulnerable to both transient and permanent faults due to unrelenting advances in CMOS technology scaling, which sometimes can be catastrophic. The considerable resource and energy consumption and the lack of dynamic adaptability make conventional fault-tolerant techniques unsuitable for future portable medical solutions. Inspired by the self-healing and self-recovery mechanisms of human nervous system, this research seeks to address reliability issues of ANN-based hardware by proposing an Autonomously Reconfigurable Artificial Neural Network (ARANN) architectural framework. Leveraging the homogeneous structural characteristics of neural networks, ARANN is capable of adapting its structures and operations, both algorithmically and microarchitecturally, to react to unexpected neuron failures. Specifically, we propose three key techniques --- Distributed ANN, Decoupled Virtual-to-Physical Neuron Mapping, and Dual-Layer Synchronization --- to achieve cost-effective structural adaptation and ensure accurate system recovery. Moreover, an ARANN-enabled self-optimizing workflow is presented to adaptively explore a "Pareto-optimal" neural network structure for a given application, on the fly. Implemented and demonstrated on a Virtex-5 FPGA, ARANN can cover and adapt 93% chip area (neurons) with less than 1% chip overhead and O(n) reconfiguration latency. A detailed performance analysis has been completed based on various recovery scenarios

    Optimization methods for topological design of interconnected ring networks

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    Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1994.Includes bibliographical references (leaves 177-179).by Valery Brodsky.M.S
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