• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.9A
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• pp.1339-1345
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• 1999

In this paper we propose the digital information hiding technique by which we use the combination of random sequence and Hadamard matrix to hide multiple information. The prior work used only one random sequence multiplied by information signal to lower the energy level of information signal and thus it is difficult for a third party to detect the information signal or jam it. But because we have to use the orthogonal code for hiding key in order to hide multiple information in the same digital image, only the use of random sequence that are not uncorrelated has some problems in the information hiding scheme. Thus we present a new information hiding scheme that can be used in hiding multiple information by the use of random sequence that spreads the energy level of the data to be hidden and Hadamard matrix that makes the random sequence uncorrelated.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.4 no.2
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• pp.389-395
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• 2000

Digital Watermarking is a research area which aims at hiding secret information in digital multimedia content such as images, audio, and video. In this paper, we propose a new watermarking method with visually recognizable symbols into the digital images using wavelet transform, spread spectrum method and multilevel threshold value in considering the wavelet coefficients. The information of watermark can be extracted by subtracting wavelet coefficients with the original image and the watermarked image. The results of this experiment show that the proposed algorithm was superior to other similar watermarking algorithms. We showed Watermarking algorithm in JPEG lossy compression, resizing, LSB(Least Significant Bit) masking, and filtering.

• Journal of the Korea Society of Computer and Information
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• v.8 no.4
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• pp.126-131
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• 2003

While the advantages of multicast delivery over multiple unicast deliveries is undeniable, the deployment of the IP multicast protocol has been limited to network domains under single administrative control. Deployment of inter-domain multicast delivery has been slow due to both technical and administrative reasons. For this reasons overlay multicasting technologies are recently proposed. We propose a End-Host Multicast Tree Protocol (EMTP) that searches two levels of the tree at a time until reaching to a leaf node and can select the nearest node that a new node try to join in the tree. Even if there is no available degree of the desirable node that a new node want to join, selecting the node as a potential parent by EMTP can reduce the number of tree switching with robustness of the tree and bring to ruduce the data delivery time.

• The Journal of the Acoustical Society of Korea
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• v.20 no.6
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• pp.82-86
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• 2001

In this Paper, we Propose synthetic aperture technique for twin-line may. Sin91e-line way is required long aperture size in order to achieve high SNR and angular resolution in shallow water Ultra low frequency signal from far-field has left-right ambiguity at sing1e-line array. To resolve these Problems, we'd like to adopt the synthetic aperture technique to twin-line array. The synthetic aperture method adopts coherent processing of sub-aperture signals at successive tine intervals in the beam domain. The proposed method shows low nile error and improved angular resolution. In simulation result, average sidelobe level is reduced about 7〔dB〕when the array Peformed 5-synthesis.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2007.10a
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• pp.347-350
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• 2007

Adaptive arrays have been proposed as an effective means of mitigating Multiple Access Interference (MAI) and improving the performance of existing and future wireless communication systems. In this paper, we apply the analytical method proposed to analyse the theoretical Mean Bit Error Rate (BER) of an uncoded IS-95 based CDMA system with an array antenna at the BS in a Ricean fading environment. We present a modified expression for the Signal to Interference plus Noise (SINR) ratio as a function of the number of users, number of antennas and noise levels. We also verify the analytical results by means of simulations by considering different user and channel scenarios.

• Journal of KIISE:Computer Systems and Theory
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• v.26 no.9
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• pp.1112-1125
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• 1999

최근 들어 멀티미디어를 지원하는 응용들의 서비스 품질 보장과 멀티캐스트 지원에 대한 요구가 증가되고 있으나 기존의 멀티캐스트 프로토콜로는 이러한 요구를 수용할 수 없는 문제가 발생하고 있다. 현재 인터넷에서 사용되고 있는 라우팅 메커니즘은 네트워크 자원 정보나 세션의 QoS 요구사항을 고려하지 않고 단순히 종단간의 연결에만 초점을 맞추고 있기 때문이다. 따라서 본 논문에서는 멀티캐스트 환경에서 서비스 품질보장을 지원하기 위한 새로운 프로토콜, LayeredQoS을 제안한다. 다중의 CP (Central Point)를 채택하고 각각의 CP에 적절한 QoS 레벨을 부여하여 사용함으로써 대역폭의 공유정도를 높일 뿐만 아니라 전체 트리 비용을 감소시켜 궁극적으로 네트워크 처리량이 증가되도록 하였다. 또한 시뮬레이션 방법을 통하여 다른 프로토콜보다 나은 성능을 가지는 것으로 평가하였다.Abstract Many emerging multimedia applications often require a guaranteed quality of service and multicast connection. But the traditional multicast protocol can't meet the needs since the routing mechanisms deployed in today's Internet are focused on connectivity, not on resource availability in the network or QoS requirements of flows. In this paper, we present LayeredQoS, a new QoS-based multicast routing algorithm. We adopt the multiple CPs(Central Points) and allocate QoS-levels for each CP in order to improve the degree of resource sharing and decrease the total tree cost, and then network throughput is increased. The proposed protocol is verified by simulations and it is shown that the performance of LayeredQoS is much better than the existing protocols.

• Proceedings of the Korea Information Processing Society Conference
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• 2005.05a
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• pp.55-58
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• 2005

In multi-level storage system with snapshot data, some snapshots which are from selection portions of the base tables are kept in main memory. So how to efficiently refresh snapshots in response to changes on their base tables for preserving consistency which requires snapshots reflect the current state of the base tables referenced by the snapshot query is a very import research issue. In this paper, a method for efficiently refreshing snapshots is proposed. In this method, it uses a data structure to store metadata which contains some necessary information of every snapshot and an updating log that records the history of changes on its base tables. Synchronization process scans the metadata and refreshing process is executed using appropriate logs after it finds anyone of the snapshot need to be refreshed.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.7
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• pp.1282-1295
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• 1994

In this paper, a hierarchical cluster multiprocessor system based on a hierarchical bus system is proposed and its cache coherency protocol is designed and implemented. The hierarchical cluster architecture aims at elimination the system bottleneck of the existing single bus system by adding a hierarchy of buses as the number of clusters is increased. Therefore the system is easy to scale up to a large number of processors. The proposed cache protocol is designed to be adapted to the general N-level (N>2) hierarchical cluster architecture. The original pended protocol is extended to implement the cache protocol on the system bus and cache coherency operations for this protocol are explained.

• 한국공간정보시스템학회:학술대회논문집
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• 1999.06a
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• pp.231-246
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• 1999

일반적으로 스키마 통합이란 각 응용들의 관점에 따라 다르게 표현된 스키마들을 하나의 스키마로 통합하는 것을 말한다. GIS 데이타베이스는 일반 데이타베이스와는 달리 개체에 대한 속성 정보 뿐만 아니라 기하 등과 같은 공간 정보를 가지고 있다. 특히, GIS 응용에서 정의된 개체들의 공간 표현은 관점에 따라 다양한 기하 서브스키마들로 표현된다. 따라서 GIS 데이타베이스를 위한 스키마 통합에서 서로 다른 기하 서브스키마들을 통합하는 것이 무엇보다 중요하다. 본 논문에서는 GIS 데이타베이스의 스키마통합을 위해서 기하 서브스키마들의 통합 문제를 중점적으로 다룬다 먼저 기하 서브스키마들의 통합에서 발생하는 충돌들을 개체의 기하를 중심으로 동일 개체간의 기하 충돌과 다른 개체간의 기하 충돌로 분류하여 정의한다. 그리고 이 충돌들을 해결하기 위한 충돌 해결 방법으로 각 충돌들의 특성을 고려하여 상위 레벨의 기하 서브스키마 선택, 기하의 다중 표현, 구성 요소의 공유, 개체들 간의 상세화 등을 제시한다. 또한, 통합된 스키마에 대하여 가상 스키마를 표현하는 방법을 제시하여, 통합되기 전의 스키마들을 통합된 스키마로부터 유도될 수 있음을 보인다. 본 논문에서는 GIS 데이타베이스 스키마를 기술하기 위하여 ISO/TC211의 개념적 스키마 언어인 EXPRESS-G를 이용한다.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.12
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• pp.1-6
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• 2008

In this paper, bias control circuit structure have been employed to improve the power added efficiency of the CMOS class-E power amplifier on low input power level. The gate and drain bias voltage has been controlled with the envelope of the input RF signal. The proposed CMOS class-E power amplifier using bias controlled circuit has been improved the PAE on low output power level. The operating frequency is 2.14GHz and the output power is 22dBm to 25dBm. In addition to, it has been evident that the designed the structure has showed more than a 80% increase in PAE for flatness over all input power level, respectively.