• Journal of the Korean Society for Precision Engineering
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• v.14 no.4
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• pp.46-55
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• 1997

This paper presents the development of intelligent performance management of computer communication networks for larger-scale integrated systems and the demonstration of its efficacy using computer simula- tion. The innermost core of the performance management is based on fuzzy set theory. This fuzzy perfor- mance manager has learning ability by using principles of neuro-fuzzy model, neuralnetwork, genetic algo- rithm(GA). Two types of performance managers are described in this paper. One is the Neuro-Fuzzy Per- formance Manager(NFPM) of which learning ability is based on the conventional gradient method, and the other is GA-based Neuro-Fuzzy Performance Manager(GNFPM)with its learning ability based on a genetic algorithm. These performance managers have been evaluated via discrete event simulation of a computer network.

• Journal of Communications and Networks
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• v.12 no.5
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• pp.492-498
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• 2010

In this paper, a new distributed space-time coded (DS-TCed) non-orthogonal decode-and-forward (NDF) protocol with source antenna switching (SAS) is proposed, where two antennas associated with each radio frequency chain can be alternatively used in the first and second phases. Several DSTC schemes for the NDF with SAS (NDF-SAS) protocol are proposed and their average pairwise error probability for the error-free source-relay (SR) channel is also derived. The simulation results show that the NDF-SAS protocol achieves larger diversity order than the NDF protocol under the error-free and erroneous SR channels.

• Journal of Communications and Networks
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• v.12 no.5
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• pp.399-405
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• 2010

Blind equalization techniques have been used in broadcast and multipoint communications. In this paper, two criteria of minimizing Euclidian distance between two probability density functions (PDFs) for adaptive blind equalizers are presented. For PDF calculation, Parzen window estimator is used. One criterion is to use a set of randomly generated desired symbols at the receiver so that PDF of the generated symbols matches that of the transmitted symbols. The second method is to use a set of Dirac delta functions in place of the PDF of the transmitted symbols. From the simulation results, the proposed methods significantly outperform the constant modulus algorithm in multipath channel environments.

• Journal of Communications and Networks
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• v.12 no.5
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• pp.459-465
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• 2010

A new blind equalization algorithm that is based on maximizing the probability that the constant modulus errors concentrate near zero is proposed. The cost function of the proposed algorithm is to maximize the probability that the equalizer output power is equal to the constant modulus of the transmitted symbols. Two blind information-theoretic learning (ITL) algorithms based on constant modulus error signals are also introduced: One for minimizing the Euclidean probability density function distance and the other for minimizing the constant modulus error entropy. The relations between the algorithms and their characteristics are investigated, and their performance is compared and analyzed through simulations in multi-path channel environments. The proposed algorithm has a lower computational complexity and a faster convergence speed than the other ITL algorithms that are based on a constant modulus error. The error samples of the proposed blind algorithm exhibit more concentrated density functions and superior error rate performance in severe multi-path channel environments when compared with the other algorithms.

• Proceedings of the Korean Information Science Society Conference
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• 2002.04a
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• pp.136-138
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• 2002

본 논문에서는 이동 통신 시스템에서 사용자의 이동성 패턴과 움직임 정보를 이용한 새로운 위치 갱신 기법을 소개한다. 현재 상용화된 대다수의 셀룰러 시스템은 지리적 영역을 위치갱신 영역으로 나누고, 사용자는 이전 위치 영역에서 새로운 위치 영역으로 이동할 때마다 위치갱신 연산을 수행한다. 이제까지 제안된 기존 기법들은 개별 사용자의 이동성과 호도착률, 더욱이 각 위치 영역에서의 사용자의 움직임 패턴을 고려하는데 미흡하였다. 특히, 사용자가 낮은 CMR을 갖거나 특정 위치 영역으로 이동할 경우가 많아지면 쓸모 없는 위치 갱신 횟수의 증가로 인하여 과도한 네트워크 트래픽이 야기된다. 이러한 상황에서 위치 갱신의 비용을 줄이기 위해서는 사용자들의 움직임 정보를 적절히 반영하여 각 위치 영역에서 위치 갱신의 수행 여부를 결정하는 효율적인 기법이 요구된다. 본 논문에서는 위치영역 내에 상주하는 이동단말들의 움직임 정보와 개별 사용자의 이등 패턴 정보를 효율적으로 이용하여 위치 갱신의 횟수를 줄일 수 있는 새로운 위치 갱신 기법을 제안한다. 수학적 모델링을 통한 제안 기업의 성능은 CMR이 낮고 사용자가 특정 위치 영역으로 이동할 확률이 높은 경우, 기존의 IS-41과 TLA 기법보다 낮은 위치관리 비용을 보여준다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.2 no.4
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• pp.473-484
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• 1998

The current interconnection charge regimes is based in fully distributed costing method. Basically this method doesn't give the incument carrier the incentive to promote efficient business operations. In this paper, 1 suggest the adoption of price cap regulation to interconnection charge as incentive schemes and review important considerations in its applications. Additionally I suggest the basic structure of the network costing model for applications of incremental costing method.

• Proceedings of the Korea Society of Information Technology Applications Conference
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• 2005.11a
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• pp.315-318
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• 2005

Lots of researches have been focusing on ubiquitous computing which means wherever, whenever, whatever the required information must be accessible. In ubiquitous computing environment, ubiquitous sensor network (USN) is the basis technology for gathering and transferring the required information. However sensor network characteristically has more severe vulnerability than the existing networks do. The paper presents operation of secure protocols for delivering information in secure in ubiquitous computing environment and show improvement of the secure transferring protocol.

• The Journal of Information Technology
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• v.12 no.1
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• pp.21-27
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• 2009

Telecommunications infrastructure based on circuit switch network is rswidly migrating to "all IP" network. However migration to IP has betw slower thaw in mawy other ve "icals because the potis ial risks and adve se impact of se vice impedi is s that may result from a migration ofttw outweigh the btwefi s of IP network. IP Telephony network has several strattgy for the replace is rof the existing Privatto nranch Exchangt, the construction of new IP networks cswible of suwoo "ing multiple communication se vices and applications, includirattgytelephony and the t ofgration of the remainiratexisting Privatto nranch Exchangts t oo new IP tfor the repfrastructure. ThTele "icle suggts s the IP tfor the network infrastructure for migration.

• Journal of Korean Institute of Industrial Engineers
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• v.31 no.1
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• pp.1-9
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• 2005

This paper proposes the heuristic algorithm for the generalized GT problems to consider the restrictions which are given the number of machine cell and maximum number of machines in machine cell as well as minimum number of machines in machine cell. This approach is split into two phase. In the first phase, we use the similarity coefficient which proposes and calculates the similarity values about each pair of all machines and sort these values descending order. If we have a machine pair which has the largest similarity coefficient and adheres strictly to the constraint about birds of a different feather (BODF) in a machine cell, then we assign the machine to the machine cell. In the second phase, we assign parts into machine cell with the smallest number of exceptional elements. The results give a machine-part grouping. The proposed algorithm is compared to the Modified p-median model for machine-part grouping.

• Journal of Korea Multimedia Society
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• v.18 no.11
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• pp.1261-1267
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• 2015

The problem of underwater target detection and classification has been attracted a substantial amount of attention and studied from many researchers for both military and non-military purposes. The difficulty is complicate due to various environmental conditions. In this paper, we study classifier ensemble methods for active sonar target classification to improve the classification performance. In general, classifier ensemble method is useful for classifiers whose variances relatively large such as decision trees and neural networks. Bagging, Random selection samples, Random subspace and Rotation forest are selected as classifier ensemble methods. Using the four ensemble methods based on 31 neural network classifiers, the classification tests were carried out and performances were compared.