• The Journal of the Korea Contents Association
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• v.4 no.4
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• pp.197-203
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• 2004

In mobile network, the maintenance o( host grouping or the multicast delivery tree for multicasting algorithm becomes a major issues. In this paper, we explore the issues of mobile Multicast scheme using Mobile-IPv6, and addresses case when a mobile host is a source as well as a recipient of a given multicast operation using MLD(Multicast Listener Discovery) scheme, and the proposed MLD-based multicasting protocol asks its HA(Home Agent) to stop forwarding multicast for group using tunneling. We examine and compare our model to existing approaches by proposed cost model, and observe an improved ferformacne.

• Journal of KIISE:Computer Systems and Theory
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• v.26 no.6
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• pp.683-692
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• 1999

관계형 데이터베이스 시스템에서 결합 연산자는 데이터베이스 질의를 구성하는 연산자들 중 가장 많은 처리시간을 요구한다. 따라서 이러한 결합연산자를 효율적으로 처리하기 위해 많은 병렬 알고리즘들이 소개되었다. 그 중 하이브리드 해쉬 결합 알고리즘은 가장 우수한 것으로 알려져왔다. 그러나 이 알고리즘은 여러 노드로 데이터를 분할하는 과정에서 데이터의 편중 문제가 발생하며, 이는 전체 시스템의 성능을 크게 저하시키게된다. 본 논문에서는 이러한 데이터 편중문제를 해결한 변형된 하이퍼퀵 정렬을 이용한 병렬 결합 알고리즘을 non-equijoin을 위한 알고리즘으로 확장하였다. 또한 T805로 연결된 하이퍼큐브 구조 시스템에서 시뮬레이션하여 얻은 결과를 수치 계산적 비용모델의 결과와 비교를 통해 변형된 하이퍼 퀵 정렬을 이용한 병렬 결합 알고리즘의 성능을 분석하고 , 비용모델의 타당성을 입증하였다.

• Proceedings of the Korean Information Science Society Conference
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• 2000.04b
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• pp.39-41
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• 2000

공간조인 연산은 지리정보시스템의 연산 중 매우 높은 처리비용을 요구하는 연산이다. DOT 공간 색인 기법은 전통적인 데이터베이스 시스템의 주색인 기법을 적용할 수 있으며, 공간객체의 상호 인접성이 유지되도록 Hilbert 값으로 정렬되어 클러스터링 된다. 이러한 특징을 이용한 DOT공간 조인 알고리즘은 적정한 버퍼크기를 유지하는 경우 잘 알려진 R-tree를 이용한 공간조인 알고리즘에 비해 디스크 액세스면에서 유리한 장점이 있으나, 조인가능영역 산출시 많은 양의 공간변환 연산을 필요로 하므로 전체적인 성능이 만족스럽지 못하다. 본 논문은 DOT 공간조인 알고리즘의 성능을 향상시키기 위하여 이러한 공간변환 연사의 횟수를 최소화시킨 효율적인 여과단계처리 방법을 제시하며, 이를 적용한 DOT공간조인 알고리즘과 R-tree 공간조인 알고리즘의 실행시간을 비교 분석하여 DOT 공간조인 알고리즘이 최대 약 2배까지 우수한 성능을 가지고 있음을 보인다.

• Annual Conference of KIPS
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• 2000.10a
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• pp.837-840
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• 2000

For secure communications in using multicast applications such as Cable-TV, It is essential for us to manage shared keys to encrypt/decrypt data through crypto algorithm as DES, which is called Group Key Management. In GKM, It is a hot issue that reduces the number of join/leave operation and subgroup key in key tree model. In this paper, we propose optimized mechanism of group key management required for providing multicast security.

• Proceedings of the Korean Information Science Society Conference
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• 2001.04b
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• pp.22-24
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• 2001

A new GIS software Spatial Database Engine(SDE) has been developed to integrated with spatial database that combines conventional and spatially related data. As we known well in the traditional relation database system, the query evaluation techniques are a well-researched subject, many useful and efficient algorithms have been proposed, but in the spatial database system, it is a litter difference with the traditionally ones. Based on the Query Graph Model(QGM), we implemented our own query evaulation plan in the SDE, which can deal with the full functionality query statement SELECT-FROM-WHERE_GROUPBY-HAVING, and treat the spatial data and non-spatial data seamlessly. We proposed a novel multi way join algorithm base on nest loop that may be attractive.

• Proceedings of the Acoustical Society of Korea Conference
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• 1991.06a
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• pp.7-10
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• 1991

In a text-to-speech system, sound units (phonemes, words, or phrases, etc.) can be concatenated together to produce required utterance. The quality of the resulting speech is dependent on factors including the phonological/prosodic contour, the quality of basic concatenation units, and how well the units join together. Thus although the quality of each basic sound unit is high, if occur the discontinuity in the concatenation part then the quality of synthesis speech is decrease. To solve this problem, a smoothing operation should be carried out in concatenation parts. But a major problem is that, as yet, no method of parameter smoothing is available for joining the segment together. Thus in this paper, we proposed a new aigorithm that smoothing the unnatural discountinuous parts which can be occured in speech waveform editing. This algorithm used the exponential smoothing method.

• Annual Conference of KIPS
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• 2018.05a
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• pp.300-303
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• 2018

최근, 불균일 기억 장치 접근 (NUMA) 구조가 부각됨에 따라 NUMA 구조 기반의 관계 연산 기법들이 제안되고 있다. 본 논문에서는 NUMA 구조 기반의 효율적인 해시 조인 기법을 제안한다. NUMA 구조에서 조인 속성 값의 분포가 편중된 릴레이션들 간의 조인은 NUMA 노드들 간의 부하 불균형과 과도한 원격 메모리 접근을 발생시킬 수 있다. 제안 기법에서는 근사 히스토그램을 이용하여 조인 속성 값의 분포를 파악하고, 이를 기반으로 원격 메모리 접근을 줄이는 전달 방안을 제안한다. 실험에서는 입력 릴레이션들에 대해 조인 속성 값의 분포를 변화시키면서 제안 기법에 대한 성능을 평가한다.

• Annual Conference of KIPS
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• 2020.05a
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• pp.44-46
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• 2020

Aggregating data with an optimal delay, which is a critical problem in Wireless Sensor Networks applications, is proven as NP-hard. In this paper, we focus on optimizing the aggregation delay by presenting an idea for channel and timeslot co-scheduling data aggregation in MWSNs. The proposed scheme, which names Break and Join, maximizes the number of sensor nodes to be scheduled in a working period, so that the overall number of working periods and data collection delay are reduced.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.11 s.353
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• pp.54-67
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• 2006

Low Rate WPAN (Wireless Personal Area Network) designed for low power and low cost wireless communication is an important technology to realize ubiquitous environment. IEEE 802.15.4 and ZigBee Alliance recommend the SKKE (Symmetric-Key Key Establishment) protocol for key establishment and management. The SKKE algorithm has security weakness such as the absence of authentication process or electric signature in key generation and exchange when devices join the role of coordinators. In this paper, we propose new key establishment and security algorithm based on public key encryption to solve low rate WPAN security problems. Also, to improve PLC AMR system's weaknesses in communication reliability and security, we propose a new AMR system model based on IEEE 802.15.4 and we apply our security algorithm to AMR profile for security enhancement.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.1A
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• pp.90-95
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• 2000

In the Ordered Core Based Tree(OCBT) protocol, a core location is the most important feature to affect the performance. In this paper, the location placement of multiple level cores is studied. The proposed algorithm isthat each node in the network evaluates a sum of shortest path costs from all the other nodes and the entirenetwork is divided into a hierarchy region to have 3-logical level(Small, Medium, Large). The node to have thelowest cost in each S-Region is decided to be a core node. Then, the core nodes in the each S-Region evaluatea sum of shortest path costs from all the other core nodes in the same M-Region. The core node to have thelowest cost is decided to be the upper level core node. Similarly the highest level core node is decided in theL-Region. The proposed algoritthm is compared with conventional two methods to put the core nodes in thenetwork One is the random method to put the core nodes randomly. The other is the center method to locatethe core node at the nearest node from the center of each S-Region and then to locate the highest level corenode at the nearest core node from the center of the entire network. Extensive simulations are performed in theview of mean tree cost and join latency. Simulation results show that the proposed algorithm has betterperformance than random method or center method.