• The KIPS Transactions:PartD
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• v.10D no.3
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• pp.387-398
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• 2003

Materialized views have received much attention for query performance improvement. They need to be refreshed whenever their underlying data sources are updated. They could be recomputed from scratch or they could be incrementally refreshed by reflecting only those portions of updates that affect them. With emergence of XML as the standard for data exchange on the Web, active research is under way on effectively storing and retrieving XML documents. In this paper, we describe a performance study on the incremental refresh of XML materialized views for the case where XML documents are stored in a relational DBMS, and XML materialized views are maintained with incremental refresh. We describe implementation of a prototype XML storage system that supports XML materialized views and their incremental refresh, and report the performance results obtained with the implemented system through a detailed set of experiments on the incremental refresh of XML materialized views. The results show that the XML view maintenance with incremental refresh outperforms the ordinary view recomputation.

• Journal of KIISE:Computer Systems and Theory
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• v.26 no.9
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• pp.1135-1144
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• 1999

본 논문에서 우리는 셀룰러 통신 시스템을 위한 위치갱신과 위치질의 비용을 줄일 수 있는 새로운 위치관리 기법을 제안한다. 위치갱신 및 위치질의 비용을 줄이기 위하여, 제안한 위치관리 기법은 사용자 지역성을 사용한다. 사용자 지역성은 이동 지역성과 호 지역성으로 이루어진다. 이동 지역성을 갖는 이동단말들을 위한 위치갱신은 지역 PVLR(Proxy-Visitor Location Register) 갱신에 의해 위치갱신 비용을 줄일 수 있다. 호 지역성을 갖는 이동단말들을 위한 위치질의는 지역 PVLR 질의에 의해 위치질의 비용을 줄일 수 있다. 분석 모델을 통하여, 제안한 기법의 성능 분석과 IS-41 표준과 제안 기법과의 성능을 비교한다. 사용된 비교 척도는 네트워크 비용, 데이타베이스 비용 그리고 호 설정 지연이다. 이들 모든 척도들에 대해서, 제안 기법이 IS-41 표준에서 정의된 위치관리 기법보다 더 좋은 성능을 보인다. 또한 비교 결과는 CMR(Call-to-Mobility Ratio)에 상관없이 제안 기법이 IS-41 기법보다 성능이 좋음을 보여준다. Abstract In this paper, we propose a new location management scheme for cellular communication systems with the goal of reducing both location update and query cost. In order to reduce both location update and query cost, the proposed scheme uses user locality. User locality consists of movement and call locality. For mobile terminals with movement locality, location update cost is reduced by local PVLR(Proxy-Visitor Location Register) update. Location query cost is reduced by local PVLR query for mobile terminals with call locality. Through analytical models, we analyze the performance of the proposed scheme and compare it with that of the IS-41 scheme. The measures of comparison used are the network cost, the database cost, and the call set up delay. For all these measures, the proposed scheme performs better than the location management scheme defined in the IS-41 standard. Result comparison also shows that the our scheme performs better than the IS-41 scheme, regardless of CMR(Call-to-Mobility Ratio).

• Journal of the Institute of Convergence Signal Processing
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• v.5 no.3
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• pp.205-209
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• 2004

The K-means algorithm is the most widely used method among the codebook generation algorithms in vector quantization. In this paper, we propose a codebook generation algorithm using a new updating condition to enhance the codebook performance. The conventional K-means algorithm uses a fixed weight of the distance for all training iterations, but the proposed method uses different weights according to the updating condition from the new codevectors for training iterations. Then, different weights can be applied to generate codevectors at each iteration according to this condition, and it can have a similar effect to variable weights. Experimental results show that the proposed algorithm has the better codebook performance than that of K-means algorithm.

• Proceedings of the Korean Information Science Society Conference
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• 2004.10c
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• pp.340-342
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• 2004

정보통신 기술의 발달로 사용자는 이동간에도 지속적인 인터넷 서비스를 받길 원한다. 이에 이동성 지원을 위한 많은 연구들이 있었다. 이동성 지원을 위한 HMIPV6환경에서 이동노드(Mobile Node)가 새로운 MAP 도메인으로 이동하거나 처음으로 MAP 도메인에 진입할 때 이동 노드는 홈 에이전트(Home Agent)와 상대 노드(Correspondent Node)에게 자신의 바인딩 정보를 갱신 하여야만 한다. 이 때 이동노드는 MAP 도메인 내에서 LCoA와 RCoA를 MAP에게 바인딩을 하고 자신의 HoA(Home Address)를 이용하여 홈 에이전트와 상대노드에게 바인딩 갱신 메시지를 보내어 바인딩 정보를 갱신한다. 본 논문은 이동 노드가 지역 바인딩 갱신(LBU)메시지와 함께 보내는 바인딩 갱신 메시지를 이용하여 MAP가 이동노드 대신 바인딩 갱신 메시지를 보냄으로써 시그널링을 줄이는 방안을 제시하고자 한다.

• Journal of Korea Multimedia Society
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• v.9 no.11
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• pp.1395-1409
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• 2006

A spatial data warehouse has spatial data cube composed of multi-dimensional data for efficient OLAP(On-Line Analytical Processing) operations. A spatial data cube supporting concept hierarchies holds huge amount of data so that many researches have studied a incremental update method for minimum modification of a spatial data cube. The Cube, however, compressed by eliminating prefix and suffix redundancy has coalescing paths that cause update inconsistencies for some updates can affect the aggregate value of coalesced cell that has no relationship with the update. In this paper, we propose incremental batch update method of a spatial data cube. The proposed method uses duplicated nodes and extended node structure to avoid update inconsistencies. If any collision is detected during update procedure, the shared node is duplicated and the duplicate is updated. As a result, compressed spatial data cube that includes concept hierarchies can be updated incrementally with no inconsistency. In performance evaluation, we show the proposed method is more efficient than other naive update methods.

• Proceedings of the Korean Information Science Society Conference
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• 2001.10c
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• pp.10-12
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• 2001

와이드 이슈 슈퍼스칼라 프로세서에서 값 예측기는 한 명령어의 결과를 미리 예측하여 명령들 간의 데이터 종속관계를 극복하고 실행함으로써 명령어 수준 병렬성(Instruction Level Parallesim ILP)을 향상시키는 기법이다. 본 논문에서는 명령어 수준 병렬성을 이용하여 성능을 향상시키기 위하여 데이터 값을 미리 예측하여 병렬로 이슈하고 수행하는 값 예측기의 성능을 비교분석 한다. 먼저 값 예측기 종류별로 성능을 측정한다 그리고 테이블의 갱신시점, 트레이스 캐시 유무 및 명령윈도우 크기에 따른 값 예측기의 성능영향을 평가분석 한다. 성능분석 결과 최근 값 예측기가 간소한 하드웨어 구성에도 불구하고 우수한 성능을 보였다. 그리고 예측테이블 갱신시점과 트레이스캐시의 사용이 값 예측기의 성능향상에 영향을 주었다.

• Journal of KIISE:Databases
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• v.34 no.2
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• pp.153-165
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• 2007

XML is widely used in various applications as the standard for representing and exchanging data on the Web. XML Schema is the standard schema for XML and an XML document generated based on the XML Schema is called 'Valid XML document'. The XML Schema validity should be guaranteed after the XML document is updated. In this paper, we design an efficient method that verifies XML Schema validity before update, and so eliminates unnecessary validations. Also, we propose validation algorithms for each update. In addition, we propose the mapping between XML data and XML Schema and a storage method for XML Schema in order to efficiently extract the schema information for the validation. Finally, we compare the performance of the validation according to the storage methods.

• Journal of Korea Spatial Information System Society
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• v.8 no.3
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• pp.117-130
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• 2006

With the rapid development of technologies related to Ubiquitous Sensor Network (USN), sensors are being utilized in various application areas. In general, the data sensed by each sensor node on ubiquitous sensor networks are stored into the central server for efficient search. Because update is delayed to reduce the cost of update in this environment, uncertain data can be stored in the central server. In addition, Uncertain data make query processing produce wrong results in the central server. Thus, this paper examines how to process uncertain data in ubiquitous sensor networks and suggests a new index for efficient processing of uncertain data. The index reduces the cost of update by delaying update in uncertainty areas. Uncertainty areas are areas where uncertain data are likely to exist. In addition, it solves the problem of low accuracy in search resulting from update delay by delaying update only for specific update areas. Lastly, we analyze the performance of the index and prove the superiority of its performance by comparing its performance evaluation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.3C
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• pp.157-162
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• 2011

For blind equalization of communication channels, concurrent equalization is useful to improve convergence characteristics. However, the concurrent equalization will result in limited performance enhancement by continuing concurrent adaptation with two algorithms after the equalizer converges to steady-state. In this paper, to improve the convergence characteristics and steady-state performance of the concurrent equalization, proposed is a new concurrent equalization technique with variable step-size parameter and weight-based tap coefficients update. The proposed concurrent vsCMA+DD equalization calculates weight factors using error signals of the variable step-size CMA (vsCMA) and DD (decision-directed) algorithm, and then updates the two equalizers based on the weights respectively. The proposed method, first, improves the error performance of the CMA by the vsCMA, and enhances the steady-state performance as well as the convergence speed further by the weight-based tap coefficients update. The performance improvement by the proposed scheme is verified through simulations.

• Proceedings of the Korean Information Science Society Conference
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• 2004.04a
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• pp.757-759
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• 2004

무선 통신 기술이 급속히 발전하면서 이동 중 데이터 통신이 가능하도록 하기 위한 연구가 활발하게 이루어지고 있다. 본 논문에서는 효율적인 이동성 제공 방안으로 멀티캐스트 기반 이동성 제공 방안을 제안하고 모의실험을 통하여 TCP 트래픽에 대한 성능을 분석하였다. 본 논문에서 제안한 방안은 이동 단말이 외부 도메인 내에서 핸드오프 시 자신의 위치 갱신을 멀티캐스트 그룹에 조인하는 방법으로 바인딩 갱신에 따른 추가적인 신호를 지역 내에서 처리함으로써 Mobile IPv6와 Hierarchical Mobile IPv6 보다 TCP 처리율을 높임을 알 수 있었다.