2,613 research outputs found
Routing and wavelength assignment in WDM optical networks
In this thesis, we focus on the routing and wavelength assignment problems in WDM all-optical networks. Since the general problem is difficult (NP-complete), we classify the problem into several models with different formulations. Our objectives are to analyze some subclasses of routing and wavelength assignment problems; to understand their special properties; to estimate algorithm bounds and performance; and, to design efficient heuristic algorithms. These goals are important because results that follow can help engineers design efficient network topologies and protocols, and eventually provide end-users with cost-effective high bandwidth.;We first study the off-line wavelength assignment problem in single fiber ring and tree networks: an optimal algorithm and an exact characterization of the optimal solution is given for binary and ternary tree topologies; an open problem based on path length restriction on trees, mentioned in the literature, is solved; and bounds are given for path-length and covering restrictions of the problem on ring networks. Then we consider multifiber optical networks, in which each link has several parallel fibers. We extend a stochastic model from the single-fiber case to the multifiber case and show that multifiber links can improve performance significantly. For some specific networks, such as ring and tree networks, we obtain some performance bounds. The bounds support our multifiber stochastic model conclusion. For practical importance, we also consider a WDM optical ring network architecture configuration problem as well as cost-effectiveness. We propose several WDM ring networks with limited fiber switching and limited wavelength conversion and these networks achieve almost optimal wavelength utilization. Attacking resource allocation within an WDM optical ring network to reduce overall equipment cost, we design a new algorithm and our simulation results indicate improvement of about 25%. This thesis also includes a new coloring problem partition-coloring and its applications.;In summary, the contributions in this thesis include several heuristic algorithms and theoretical tight upper bounds for both single fiber and multifiber all-optical networks. In particular, for ring networks we have proposed several network architectures to improve wavelength utilization and devised a new algorithm that combines routing and wavelength assignment to reduce hardware costs
Forwarding and optical indices of 4-regular circulant networks
An all-to-all routing in a graph is a set of oriented paths of , with
exactly one path for each ordered pair of vertices. The load of an edge under
an all-to-all routing is the number of times it is used (in either
direction) by paths of , and the maximum load of an edge is denoted by
. The edge-forwarding index is the minimum of
over all possible all-to-all routings , and the arc-forwarding index
is defined similarly by taking direction into
consideration, where an arc is an ordered pair of adjacent vertices. Denote by
the minimum number of colours required to colour the paths of such
that any two paths having an edge in common receive distinct colours. The
optical index is defined to be the minimum of over all possible
, and the directed optical index is defined
similarly by requiring that any two paths having an arc in common receive
distinct colours. In this paper we obtain lower and upper bounds on these four
invariants for -regular circulant graphs with connection set , . We give approximation algorithms with performance ratio a
small constant for the corresponding forwarding index and routing and
wavelength assignment problems for some families of -regular circulant
graphs.Comment: 19 pages, no figure in Journal of Discrete Algorithms 201
Methods and problems of wavelength-routing in all-optical networks
We give a survey of recent theoretical results obtained for wavelength-routing in all-optical networks. The survey is based on the previous survey in [Beauquier, B., Bermond, J-C., Gargano, L., Hell, P., Perennes, S., Vaccaro, U.: Graph problems arising from wavelength-routing in all-optical networks. In: Proc. of the 2nd Workshop on Optics and Computer Science, part of IPPS'97, 1997]. We focus our survey on the current research directions and on the used methods. We also state several open problems connected with this line of research, and give an overview of several related research directions
Scalable dimensioning of resilient Lambda Grids
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Multiclass scheduling algorithms for the DAVID metro network
AbstractâThe data and voice integration over dense wavelength-division-multiplexing (DAVID) project proposes a metro network architecture based on several wavelength-division-multiplexing (WDM) rings interconnected via a bufferless optical switch called Hub. The Hub provides a programmable interconnection among rings on the basis of the outcome of a scheduling algorithm. Nodes connected to rings groom traffic from Internet protocol routers and Ethernet switches and share ring resources. In this paper, we address the problem of designing efficient centralized scheduling algorithms for supporting multiclass traffic services in the DAVID metro network. Two traffic classes are considered: a best-effort class, and a high-priority class with bandwidth guarantees. We define the multiclass scheduling problem at the Hub considering two different node architectures: a simpler one that relies on a complete separation between transmission and reception resources (i.e., WDM channels) and a more complex one in which nodes fully share transmission and reception channels using an erasure stage to drop received packets, thereby allowing wavelength reuse. We propose both optimum and heuristic solutions, and evaluate their performance by simulation, showing that heuristic solutions exhibit a behavior very close to the optimum solution. Index TermsâData and voice integration over dense wavelength-division multiplexing (DAVID), metropolitan area network, multiclass scheduling, optical ring, wavelength-division multiplexing (WDM). I
Measurement Based Reconfigurations in Optical Ring Metro Networks
Single-hop wavelength division multiplexing (WDM) optical ring networks operating in packet mode are one of themost promising architectures for the design of innovative metropolitan network (metro) architectures. They permit a cost-effective design, with a good combination of optical and electronic technologies, while supporting features like restoration and reconfiguration that are essential in any metro scenario. In this article, we address the tunability requirements that lead to an effective resource usage and permit reconfiguration in optical WDM metros.We introduce reconfiguration algorithms that, on the basis of traffic measurements, adapt the network configuration to traffic demands to optimize performance. Using a specific network architecture as a reference case, the paper aims at the broader goal of showing which are the advantages fostered by innovative network designs exploiting the features of optical technologies
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