447 research outputs found
Sonet Network Design Problems
This paper presents a new method and a constraint-based objective function to
solve two problems related to the design of optical telecommunication networks,
namely the Synchronous Optical Network Ring Assignment Problem (SRAP) and the
Intra-ring Synchronous Optical Network Design Problem (IDP). These network
topology problems can be represented as a graph partitioning with capacity
constraints as shown in previous works. We present here a new objective
function and a new local search algorithm to solve these problems. Experiments
conducted in Comet allow us to compare our method to previous ones and show
that we obtain better results
Optimization in Telecommunication Networks
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 Mengerâs disjoint paths theorem, and Ford-Fulkersonâs 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;
An Improved Upper Bound for the Ring Loading Problem
The Ring Loading Problem emerged in the 1990s to model an important special
case of telecommunication networks (SONET rings) which gained attention from
practitioners and theorists alike. Given an undirected cycle on nodes
together with non-negative demands between any pair of nodes, the Ring Loading
Problem asks for an unsplittable routing of the demands such that the maximum
cumulated demand on any edge is minimized. Let be the value of such a
solution. In the relaxed version of the problem, each demand can be split into
two parts where the first part is routed clockwise while the second part is
routed counter-clockwise. Denote with the maximum load of a minimum split
routing solution. In a landmark paper, Schrijver, Seymour and Winkler [SSW98]
showed that , where is the maximum demand value. They
also found (implicitly) an instance of the Ring Loading Problem with . Recently, Skutella [Sku16] improved these bounds by showing that , and there exists an instance with .
We contribute to this line of research by showing that . We
also take a first step towards lower and upper bounds for small instances
Minimizing SONET ADMs in unidirectional WDM rings with grooming ratio 3
We consider traffic grooming in WDM unidirectional rings with all-to-all uniform unitary traffic. We determine the minimum number of SONET/SDH add-drop multiplexers (ADMs) required when the grooming ratio is 3. In fact, using tools of design theory, we solve the equivalent edge partitioning problem: find a partition of the edges of the complete graph on n vertices (K_n) into subgraphs having at most 3 edges and in which the total number of vertices has to be minimized
Traffic Grooming in Unidirectional WDM Rings with Bounded Degree Request Graph
Traffic grooming is a major issue in optical networks. It refers to grouping
low rate signals into higher speed streams, in order to reduce the equipment
cost. In SONET WDM networks, this cost is mostly given by the number of
electronic terminations, namely ADMs. We consider the case when the topology is
a unidirectional ring. In graph-theoretical terms, the traffic grooming problem
in this case consists in partitioning the edges of a request graph into
subgraphs with a maximum number of edges, while minimizing the total number of
vertices of the decomposition. We consider the case when the request graph has
bounded maximum degree , and our aim is to design a network being able
to support any request graph satisfying the degree constraints. The existing
theoretical models in the literature are much more rigid, and do not allow such
adaptability. We formalize the problem, and solve the cases (for all
values of ) and (except the case C=4). We also provide lower
and upper bounds for the general case
Drop cost and wavelength optimal two-period grooming with ratio 4
We study grooming for two-period optical networks, a variation of the traffic
grooming problem for WDM ring networks introduced by Colbourn, Quattrocchi, and
Syrotiuk. In the two-period grooming problem, during the first period of time,
there is all-to-all uniform traffic among nodes, each request using
of the bandwidth; and during the second period, there is all-to-all uniform
traffic only among a subset of nodes, each request now being allowed to
use of the bandwidth, where . We determine the minimum drop cost
(minimum number of ADMs) for any and C=4 and . To do
this, we use tools of graph decompositions. Indeed the two-period grooming
problem corresponds to minimizing the total number of vertices in a partition
of the edges of the complete graph into subgraphs, where each subgraph
has at most edges and where furthermore it contains at most edges of
the complete graph on specified vertices. Subject to the condition that the
two-period grooming has the least drop cost, the minimum number of wavelengths
required is also determined in each case
Edge-partitioning regular graphs for ring traffic grooming with a priori placement od the ADMs
We study the following graph partitioning problem: Given two positive integers C
and Î, find the least integer M(C,Î) such that the edges of any graph with maximum degree at
most Î can be partitioned into subgraphs with at most C edges and each vertex appears in at most
M(C,Î) subgraphs. This problem is naturally motivated by traffic grooming, which is a major
issue in optical networks. Namely, we introduce a new pseudodynamic model of traffic grooming in
unidirectional rings, in which the aim is to design a network able to support any request graph with
a given bounded degree. We show that optimizing the equipment cost under this model is essentially
equivalent to determining the parameter M(C, Î). We establish the value of M(C, Î) for almost all
values of C and Î, leaving open only the case where Î â„ 5 is odd, Î (mod 2C) is between 3 and
C â 1, C â„ 4, and the request graph does not contain a perfect matching. For these open cases, we
provide upper bounds that differ from the optimal value by at most one.Peer ReviewedPostprint (published version
Grooming
chapter VI.27International audienceState-of-the-art on traffic grooming with a design theory approac
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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