No. 3 (2005)
Published:
2005-09-30
ARTICLES FROM THIS ISSUE
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Telecommunications, multiple criteria analysis and knowledge theory
Abstract
Telecommunications requires multiple criteria analysis and decision support. It is shown how some basic facts from telecommunications and informational sciences can be used to formulate a rational theory of intuition, developed as a complement of multiple criteria decision support. This paper presents a method called creative space used for integrating various approaches to knowledge creation and based on SECI spiral, I5 system and rational theory of intuition. Questions of supporting new technology creation by constructing specialized creative environments similar to decision support environments are also indicated.
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On the performance analysis of a heuristic approach dedicated to a multiobjective dynamic routing model
Abstract
In previous works the features and a complete formulation for circuit-switched networks of a multiple objective dynamic routing method (MODR) of periodic state dependent routing type were presented. The aim of the model is to resolve a very complex network bi-objective dynamic routing problem, by recurring to a heuristic for synchronous path selection enabling to obtain a good compromise solution in terms of two network performance measures. In this paper we present a study on the performance of variants of the MODR heuristic of synchronous path selection by using relaxations of the values previously calculated for the two network objective functions. This study permitted the development of an improved version of the initial heuristic. Also a comparison of the analytical values of the network objective functions obtained with selected variants of the initial heuristic with the corresponding results from a known reference method, the real time network routing (RTNR) method, given by a discrete-event simulator for single-service networks, is presented.
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Swarm intelligence for network routing optimization
Abstract
This paper presents the results of a comparative study of network routing approaches. Recent advances in the field suggest that swarm intelligence may offer a robust, high quality solution. The overall aim of the study was to develop a framework to facilitate the empirical evaluation of a swarm intelligence routing approach compared to a conventional static and dynamic routing approach. This paper presents a framework for the simulation of computer networks, collection of performance statistics, generation and reuse of network topologies and traffic patterns.
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Distributed asynchronous algorithms in the Internet – new routing and traffic control methods
Abstract
The paper presents several new algorithms concerning the third (network) and the fourth (transport) layer of ISO/OSI network model. For the third layer two classes of the shortest paths algorithms – label correcting and auction algorithms – are proposed. For the fourth layer an application of price decomposition to network optimization and Internet congestion control is suggested.
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Optimization approach with ρ-proximal convexification for Internet traffic control
Abstract
The optimization flow control algorithm for traffic control in computer networks, introduced by Steven H. Low, works only for concave utility functions. This assumption is rather optimistic and leads to several problems, especially with streaming applications. In an earlier paper we introduced a modification of the algorithm based on the idea of proximal convexification. In this paper we extend this approach, replacing the proximal method with the ρ-proximal method. The new method mixes the quadratic proximal term with higher-order terms, achieving better results. The algorithms are compared in a simple numerical experiment.
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Telecommunications network design and max-min optimization problem
Abstract
Telecommunications networks are facing increasing demand for Internet services. Therefore, the problem of telecommunications network design with the objective to maximize service data flows and provide fair treatment of all services is very up-to-date. In this application, the so-called maxmin fair (MMF) solution concept is widely used to formulate the resource allocation scheme. It assumes that the worst service performance is maximized and the solution is additionally regularized with the lexicographic maximization of the second worst performance, the third one, etc. In this paper we discuss solution algorithms for MMF problems related to telecommunications network design. Due to lexicographic maximization of ordered quantities, theMMF solution concept cannot be tackled by the standard optimization model (mathematical programme). However, one can formulate a sequential lexicographic optimization procedure. The basic procedure is applicable only for convex models, thus it allows to deal with basic design problems but fails if practical discrete restrictions commonly arriving in telecommunications network design are to be taken into account. Then, however, alternative sequential approaches allowing to solve non-convex MMF problems can be used.
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Software tools for a multilayer network design
Abstract
Today’s long haul and metro high-speed networks are mainly based on synchronous digital hierarchy (SDH) or its American equivalent synchronous optical network (SONET) and wavelength division multiplex (WDM). On the other hand, the large amount of traffic growth during the last years has been caused mainly by Internet protocol (IP) traffic. Traditionally, the IP-router based networks and the cross-connect based synchronous networks are often planned and operated separately. However, in line with new developments such as generalized multiprotocol label switching (GMPLS), network providers begin to realize that the convergence of these two worlds promises significant benefits. A set of software tools to support the network designer has been developed and used on various kinds of real world network planning problems arising in the SDH/WDM context. This includes, among others, 1+1 protection planning, static restoration and dual homing issues. These tools are extended with additional features to handle aspects of the IP/SDH interplay in a GMPLS environment. The two main components are an AMPL based integer model (solved via CPLEX) and a heuristic implemented in C++.
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Structural modeling and systems analysis of uneasy factors for realizing safe, secure and reliable society
Abstract
In this paper we try to extract various uneasy factors in our life. Then, we try to construct structural models among these factors using Decision Making Trial and Evaluation Laboratory (DEMATEL). For the purpose of analyzing priority among these factors we revised the DEMATEL and found effective factors to be resolved in order to realize future safe, secure and reliable (SSR) society.
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Intelligent decision system based on the evidential reasoning approach and its applications
Abstract
Intelligent decision system (IDS) is a window-based software package that has been developed on the basis of the evidential reasoning (ER) approach, a recent development in handling hybrid multiple criteria decision analysis (MCDA) problems with uncertainties. In this paper, the evidential reasoning approach will be briefly described first, and its major differences from and the relationships with conventional MCDA methods will also be discussed. Then the main features, advantages and benefits of IDS will be demonstrated and explained using two application examples: supplier pre-qualification assessment and customer satisfaction survey analysis, which have been investigated as part of the research projects led by the authors and funded by the UK government and the EC. It is concluded in the paper that the ER approach can be used not only to deal with problems that traditional methods can solve, but also to model and analyse more complicated decision problems that traditional methods are incapable of handling.
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Structural representations of unstructured knowledge
Abstract
Knowledge should be represented in a formal, structured manner if we want to process and manage it. Unfortunately a source knowledge presented in many documents has informal, unstructured shape. The goal of these considerations is to present the methods of translation from the textual, unstructured knowledge to the structured knowledge, preserving textual form.
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Event mining based on observations of the system
Abstract
Event mining is becoming a challenging area of research. Events in system analysis is not a new concept. It has been used in Petri nets, stochastic modeling, etc. However, there are new opportunities that come from the lage amount of data that is stored in various databases. In this paper we will focus on formulating the event mining tasks that consider observations of the system as well as internal and external events.
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Time series denoising with wavelet transform
Abstract
This paper concerns the possibilities of applying wavelet analysis to discovering and reducing distortions occurring in time series.Wavelet analysis basics are briefly reviewed. WaveShrink method including three most common shrinking variants (hard, soft, and non-negative garrote shrinkage functions) is described. Another wavelet-based filtering method, with parameters depending on the length of wavelets, is introduced. Sample results of filtering follow the descriptions of both methods. Additionally the results of the use of both filtering methods are compared. Examples in this paper deal only with the simplest “mother” wavelet function – Haar basic wavelet function.
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Influence of temperature and aging on polarization mode dispersion of tight-buffered optical fibers and cables
Abstract
This paper presents results of laboratory tests investigating influence of temperature on polarization mode dispersion (PMD) in variety of single mode optical fibers and cables. Research was focused primarily on tight-buffered fibers, where most pronounced effects resulting from buffer shrinkage or expansion were expected. The goal was to verify performance of optical fiber cable exposed to extreme temperatures and to compare behavior of different cables. Very strong temperature dependence of PMD was detected in standard single mode fibers with 0.9 mm tight buffer, commonly used in indoor cables, and in complete cable with such fiber. However, both nonzero dispersion-shifted fibers, spun during drawing and optical unit used in optical ground wire (OPGW), where 12 fibers are stranded showed good stability of PMD during thermal cycling. The same optical unit extracted from OPGW exhibited excellent PMD stability also during accelerated life test.
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Evolutionary paths in wireless communication systems
Abstract
The paper contains a review and analysis of evolutionary paths of seven most important, from network development strategy point of view, wireless communication systems, especially the WLAN operating according to the IEEE 802.11 standard. With respect to WLAN, trends related to evolution toward mobile network and self organizing network as well as toward integration of WLAN and GSM using GPRS are presented. Concerning WLAN architecture development, evolution paths toward distributed controlled network as well as centrally coordinated and controlled network are described. Moreover, analysis includes cellular mobile radio systems, wireless personal networks, wide area wireless packet data systems, satellite-based mobile systems, paging/messaging systems and cordless telephones. With respect to these systems, general evolution process and trends associated with this process are described.
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The Kummer confluent hypergeometric function and some of its applications in the theory of azimuthally magnetized circular ferrite waveguides
Abstract
Examples of the application of the confluent hypergeometric functions in miscellaneous areas of the theoretical physics are presented. It is suggested these functions to be utilized as a universal means for solution of a large number of problems, leading to: cylindrical, incomplete gamma, Coulomb wave, Airy, Kelvin, Bateman, Weber’s parabolic cylinder, logarithmic-integral and exponential integral functions, generalized Laguerre, Poisson-Charlier and Hermit polynomials, integral sine and cosine, Fresnel and probability integrals, etc. (whose complete list is given), which are their special cases. The employment of such an approach would permit to develop general methods for integration of these tasks, to generalize results of different directions of physics and to find the common features of various phenomena, governed by equations, pertaining to the same family. Emphasis is placed here on the use of the Kummer function in the field of microwaves: the cases of normal and slow rotationally symmetric TE modes propagation in the azimuthally magnetized circular ferrite waveguide are considered. Lemmas on the properties of the argument, real and imaginary parts, and positive purely imaginary (real) zeros of the function mentioned in the complex (real) domain, of importance in the solution of boundary-value problem stated for normal (slow) waves, are substantiated analytically or numerically. A theorem for the identity of positive purely imaginary and real zeros of the complex respectively real Kummer function for certain parameters, is proved numerically. Tables and graphs support the results established. The terms for wave transmission are obtained as four bilaterally open intervals of variation of the quantities, specifying the fields. It turns out that the normal (slow) modes may exist in one (two) region(s). The theoretically predicted phase curves for the first waves of the two TE sets examined show that the structure explored is suitable for ferrite control components design.
