• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.3B
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• pp.179-187
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• 2002

This paper proposes and analyzes the iterative groupwise equal-delay interference cancellation(IGEIC) algorithm for coherent detection of an asynchronous wideband DS-CDMA system in a single cell over multipath fading channels. The IGEIC algorithm divide users in a system into several groups, and subtract out interference signal from the received signal as many as the number of users within a user group, iteratively. The IGEIC algorithm is also classified into the iterative groupwise equal-delay serial interference cancellation(IGESIC) algorithm and the iterative groupwise equal-delay parallel interference cancellation(IGEPIC) algorithm. In the case of perfect correlation for spreading codes, it shows that the performance of IGESIC and IGEPIC algorithm is the same after interference cancellation of as many as the number of users within a user group, but the performance of IGEPIC algorithm is superior to the IGESIC algorithm just before fecal cancellation within a user group. The results show that (he performance of the two proposed algorithms are also superior to the SIC algorithm by 3dB.

• The KIPS Transactions:PartA
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• v.16A no.5
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• pp.319-326
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• 2009

Since string operations were applied to computational biology area, various data structures and algorithms for computing efficient string operations have been studied. The longest common substring problem is an operation to find the longest matching substring in more than two strings, and maximal repeat of string problem is an operation to find substrings repeated more than once in the given string. These operations are importantly used in the string processing area such as pattern matching and likelihood measurement. In this paper, we present algorithms to compute the longest common substring of two strings and to find the maximal repeat of string using three-dimensional $n{\times}n{\times}n$ processors on RMESH(Reconfigurable MESH). Our algorithms have O(1) time complexity.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2010.11a
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• pp.171-174
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• 2010

무선 통신 환경에서 간섭과 잡음으로 인한 채널 추정 오류는 데이터 검출을 위한 등화 성능을 현저하게 저하시킨다. 포스트 프로세싱은 채널 추정 이후에 이러한 추정 오류를 줄이기 위한 작업이며, 여기서는 소수의 채널 계수만이 무선 채널의 다중 경로에 의한 신호 성분을 갖는 무선 채널의 특성을 이용하여 신호 성분을 포함하지 않은 계수를 선별하고 이를 제거함으로써 채널 추정 오류를 줄이는 방법을 위한 순환 알고리즘을 제안한다. 기존 알고리즘은 잡음 분산을 기준으로 문턱값을 결정하고, 그 문턱 값보다 작은 계수는 신호성분을 포함하지 않는다고 간주하여 이를 제거하였다. 제안된 순환 알고리즘은 잡음 분산의 추정치를 반복이 진행됨에 따라 갱신하여 이를 기준으로 구한 문턱값을 이용한 포스트 프로세싱을 반복함으로써 채널 추정 성능을 개선시킨다. 제안된 방법은 기존의 방법과 유사한 복잡도를 갖는 반복 횟수를 적용하는 경우에 월등히 성능이 개선되며, 특히 반복 횟수를 조절함으로써 처리 시간과 채널 추정 성능을 최적화할 수 있는 유연성을 갖고 있다.

• Proceedings of the Korea Information Processing Society Conference
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• 2019.05a
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• pp.412-414
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• 2019

경로 계획은 에이전트가 로봇이 특정 목적지에 도착할 수 있도록 에이전트가 수집한 정보를 바탕으로 경로를 설정하는 작업을 뜻한다. 부분 관측만 가능한 맵인 경우 에이전트 이동마다 새로 수집되는 정보들을 바탕으로 마르코프 의사결정 과정을 사용한 가치 반복 알고리즘이 널리 사용되지만, 제안된 가치 반복 알고리즘 사용 시 매 행동마다 모든 공간의 최적 경로를 계산하기 때문에 시간이 오래 걸리는 문제점이 있다. 이에 본 논문에서는 에이전트가 한 번에 탐색하는 범위가 제한되어 있다는 점에 착안하여 탐색 반경 내에 속하는 공간의 가치 함수 값을 미리 추정하여 효율적으로 최적의 경로를 추정하는 가치 반복 알고리즘을 제안한다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.10C
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• pp.1387-1394
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• 2004

Turbo code, a kind of error correction coding technique, has been used in the field of digital mobile communication systems. And it is well known about the fact that turbo code has better the BER performance as the number of decoding iterations increases in the AWGN channel environment. However, as the number of decoding iterations is increased under the several channel environments, any further iteration results in very little improvement, and it requires much delay, computation and power consumption in proportion to the number of decoding iterations. In this paper, it proposes the efficient iterative decoding stop criterion algorithm which can largely reduce the average number of decoding iterations of turbo code. Through simulations, it is verifying that the proposed algorithm can efficiently stop the iterative decoding by using the variance value of error probability for the soft output value, and can largely reduce the average number of decoding iterations without BER performance degradation. As a result of simulation, the average number of decoding iterations for the proposed algorithm is reduced by about 2.25% ~14.31％ and 3.79％ ~14.38% respectively compared to conventional schemes, and power consumption is saved in proportion to the number of decoding iterations.

• Proceedings of the Korea Information Processing Society Conference
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• 2016.10a
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• pp.559-561
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• 2016

로그 테이터 속에서 시간차를 두고 발생하는 트랜잭션 혹은 이벤트를 감지하는 일은 유통, 마케팅, 금융 등 다양한 분야에서 활용될 수 있다. 데이터베이스 분야에서 반복되는 패턴을 감지하는 알고리즘은 종종 소개되었지만, 데이터의 특성과 트랜잭션 간의 시간 간격을 고려한 연관 규칙 탐색 알고리즘 연구는 빈약했다. 본 논문에서는 정해진 구간에서 반복되는 패턴을 찾거나 주어진 아이템에 대한 주기를 찾는 등의 기존연구와 달리 전체 데이터베이스를 스캔하여 찾을 수 있는 연관 규칙과 그 연관 규칙이 반복되는 시간 간격을 함께 탐색하는 알고리즘을 제안한다. 또한, 제안하는 알고리즘의 처리시간에 대한 실험을 통해 성능을 확인한다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.17 no.8
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• pp.891-897
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• 1992

A local iterative Image restoration method Is Introduced that processes with varying iteration numbers according to the local statistics. In general almost of the Iterative method applies Its algorithm to the whole Image without considering the local pixel informations, which Is not so effective for the processing time. Usually the edges or details have an Important role In visual effect. So in this paper we process the edges or the details many times while In the flat region we just pass over or decrease iterations. This method shows good MSE (Mean Square Error) improvement, better subjective qualify and reduced processing time.

• Communications for Statistical Applications and Methods
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• v.16 no.3
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• pp.409-419
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• 2009

In this article, an explicit solution of the EM algorithm for the image deburring is presented. To obtain the restore image from the strictly iterative EM algorithm is quite time-consumed and impractical in particular when the underlying observed image is not small and the number of iterations required to converge is large. The explicit solution provides a quite reasonable restore image although it exploits the approximation in the outside of the valid area of image, and also allows to obtain the effective EM solutions without iteration process in real-time in practice by using the discrete finite Fourier transformation.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.41 no.3
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• pp.73-81
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• 2004

To extract the creditable features in fingerprint image, many people use the thinning algorithm that has a very important position in the preprocessing. In this paper, we propose the robust parallel thinning algorithm that can preserve the connectivity of the binarized fingerprint image, make the thinnest skeleton with 1-pixel width and get near to the medial axis extremely. The proposed thinning method repeats three sub-iterations. The first sub-iteration takes off only the outer boundary pixel by using the interior points. To extract the one side skeletons, the second sub-iteration finds the skeletons with 2-pixel width. The third sub-iteration prunes the needless pixels with 2-pixel width existing in the obtained skeletons and then the proposed thinning algorithm has the robustness against the rotation and noise and can make the balanced medial axis. To evaluate the performance of the proposed thinning algorithm we compare with and analyze the previous algorithms.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.24 no.12
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• pp.1632-1638
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• 2020

In this paper, we investigate a multi-beam satellite communication system where multiple terminals transmit information signals to the gateway via a satellite. The satellite is equipped with phased array antennas to form multiple spot beams of which bandwidths are not identically allocated. We formulate an optimization problem to maximize fairness of beam bandwidth allocation. In order to solve the problem, we propose two heuristic algorithms; iterative beam bandwidth allocation (IBBA) and request ratio-based beam bandwidth allocation (RRBBA) algorithms. The IBBA algorithm iteratively equalizes the ratio of allocated bandwidth of each beam to their resource request while the RRBBA algorithm allocates beam bandwidth calculated from the ratio. Simulation results show that the IBBA algorithm has close fairness performance to the optimum while the RRBBA algorithm has less performance than the IBBA algorithm at the price of reduced computational complexity.