• 전자공학회논문지B
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• 제30B권4호
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• pp.104-115
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• 1993

The motion compensated coding (MCC) technique, which exploits the temporal redundancies in the moving images with the motion estimation technique,is one of the most popular techniques currently used. Recently, a variable block size(VBS) motion estimation scheme has been utilized to improve the performance of the motion compensted coding. This scheme allows large blocks to the used when smaller blocks provide little gain, saving rates for areas containing more complex motion. Hence, a new VBS motion estimation scheme with a hierarchical structure is proposed in this paper, in order to combine the motion vector coding technique efficiently. Topmost level motion vector, which is obtained by the gain/cost motion estimation technique with selective motion prediction method, is always transmitted. Thus, the hierarchical VBS motion estimation scheme can efficiently exploit the redundancies among neighboring motion vectors, providing an efficient motion vector encoding scheme. Also, a restricted search with respect to the topmost level motion vector enables more flexible and efficient motion estimation for the remaining lower level blocks. Computer simulations on the high resolution image sequence show that, the VBS motion estimation scheme provides a performance improvement of 0.6~0.7 dB, in terms of PSNR, compared to the fixed block size motion estimation scheme.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 학술대회 논문집 정보 및 제어부문
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• pp.484-486
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• 2005

Passenger safety is a primary concern of railway system but, it has been urgent issue that dozens of people are killed every year when they falloff from train platforms. Recently, advancements in IT have enabled applying vision sensors to railway environments, such as CCTV and stereo camera sensors. In this paper, we propose a stereoscopic video coding scheme for subway accident monitoring system. The proposed scheme is designed for providing flexible video among various displays, such as control center, station employees and train driver. We uses MPEG-2 standard for coding the left-view sequence and IBMDC for predicting the P- and B-types of frames of the right-view sequence. IBMDC predicts matching block by interpolating both motion and disparity predicted macroblocks. To provide efficient stereoscopic video service. we define both temporally and spatially scalable layers for each eye's-view by using the concept of Spatio-Temporal scalability. According to the experimental results. we expect the proposed functionalities will play a key role in establishing highly flexible stereoscopic video codec for ubiquitous display environment where devices and network connections are heterogeneous.

• 한국공간정보시스템학회 논문지
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• 제8권1호
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• pp.59-75
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• 2006

최근 가장 활발하고 많은 연구가 이루어지는 시스템중의 하나는 교통 제어 시스템이다. 이 시스템을 효과적으로 지원하기 위해서는 이동체를 효과적으로 저장하고, 시간 혹은 시공간 질의를 효과적으로 수행하기 위하여 높은 성능을 가진 이동체 데이터베이스 시스템이 필요하다. 빠른 이동체 데이터베이스 시스템의 성능은 병렬 색인을 이용하여 구축될 수 있다. 이 논문에서는 시공간 인접성과 이동체 특성에 기반한 디클러스터링 정책을 제시한다. 이동체의 진행 방향에 대한 예측을 통하여 색인의 노드에 대한 성장을 예측하고, 이를 토대로 병렬 색인을 구축한다. 실험 결과 제시된 기법은 기존의 다른 정책에 비하여 최대 15%이상의 성능 향상이 있다. 이 결과는 단일 디스크를 사용할 때에 비하여 디스크 당 50%이상의 성능향상 결과이다.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2008년도 지능정보 및 응용 학술대회
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• pp.91-94
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• 2008

모바일 기기와 무선 통신 기술이 발달함에 따라 모바일 기기에서 수집 또는 변경되는 대용량 시공간 데이터를 서버와 현장에서 동기화하는 서비스의 제공이 가능해졌다. 다수의 모바일 기기에서 변경된 대용량 시공간 데이터를 서버와 동기화하는 효율적인 양방향 동기화 프로토콜이 필요하다. 그러나 다수의 모바일 기기에 대하여 동기화 작업을 수행할 때 처리 시간이 길어지는 문제가 있다. 이 논문에서는 다수의 양방향 동기화 작업에 대하여 다중 큐를 이용하여 서버에서 동시 수행하는 처리기법에 대하여 제안한다.

• ETRI Journal
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• 제43권1호
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• pp.40-52
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• 2021

DNS (Domain Name System) tunnels almost obscure the true network activities of users, which makes it challenging for the gateway or censorship equipment to identify malicious or unpermitted network behaviors. An efficient way to address this problem is to conduct a temporal-spatial analysis on the tunnel traffic. Nevertheless, current studies on this topic limit the DNS tunnel to those with a single protocol, whereas more than one protocol may be used simultaneously. In this paper, we concentrate on the refined identification of two protocols mixed in a DNS tunnel. A feature set is first derived from DNS query and response flows, which is incorporated with deep neural networks to construct a regression model. We benchmark the proposed method with captured DNS tunnel traffic, the experimental results show that the proposed scheme can achieve identification accuracy of more than 90%. To the best of our knowledge, the proposed scheme is the first to estimate the ratios of two mixed protocols in DNS tunnels.

• ETRI Journal
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• 제34권1호
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• pp.9-16
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• 2012

Precoding in the multiple-input multiple-output orthogonal frequency division multiplexing system is investigated. In conventional wideband precoding (WBP), only one precoder, obtained from the decomposition of the subcarrier independent channel matrix, is used for all subcarriers. With an investigation of the relationship between the subcarrier independent channel matrix and the temporal/frequency channels, an improved WBP scheme is proposed for practical scenarios in which a part of subcarriers are allocated to a user. The improved WBP scheme is a generalized scheme of which narrow-band precoding and conventional WBP schemes are special modes. Simulation results demonstrate that the improved WBP scheme almost achieves the optimum performance of a single precoder and outperforms the conventional WBP scheme in terms of the bit error ratio and ergodic capacity with slight complexity increase. The largest advantage of the improved WBP scheme on signal-to-noise ratio in simulation results is over 2.1 dB.

• Journal of Information Display
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• 제11권4호
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• pp.154-159
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• 2010

Single-sustainer driving is an AC PDP driving scheme to reduce the circuitry by maintaining the sustain electrode at ground level. To date, however, the research on the discharge characteristics in such driving scheme is insufficient. In this study, the panel performance and discharge characteristics of the single-sustainer driving scheme were observed while varying the address electrode condition. In single-sustainer driving, the address electrode is strongly involved in the sustain discharge when the former is maintained at ground level, and the dependence of the luminous efficacy on the sustain voltage is different from that in the conventional driving scheme. The dependence of the luminous efficacy on the sustain voltage appeared similar, however, to that in the conventional driving scheme when the address electrode was floated in single-sustainer driving. In the investigation of the temporal evolution of the sustain discharge using an IICCD camera, it was found that the sustain discharge in single-sustainer driving with a floating address electrode is similar to that in the conventional driving scheme, and the strong plasma formation region was located in the vicinity of the MgO surface, which seems to be related to the lifetime of a PDP with single-sustainer driving. In the investigation of the operation characteristics, the PDP that was operated with a floated address electrode showed a narrower dynamic operation margin, but a longer lifetime was expected.

• 한국방송∙미디어공학회:학술대회논문집
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• 한국방송공학회 2006년도 학술대회
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• pp.307-312
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• 2006

Protection to the multimedia contents is inevitable to ensure that only authorized users be able to access the protected contents for consumption. Since protection mechanisms need to be designed efficiently by exploiting the type of the contents, we propose a protection scheme for the video bitstream encoded by Scalable Video Coding (SVC) technique. Our scheme exploits the property of SVC in which a video is encoded into spatial, temporal, and quality scalability layers. By applying our proposed protection scheme to the appropriate scalability layers we can effectively control the SVC contents completely or partially. Each layer can be flexibly protected with different encryption keys or even with different encryption algorithms. The algorithms that are used to protect each layer are described by the standardized protection description tool, which is the MPEG-21 Intellectual Property Management and Protection (IPMP) Components. In this paper, we present the design of the proposed layered SVC protection scheme, its implementation and experimental results. The experiment result shows that the proposed layered SVC protection scheme is very effective and can easily be applied.

• Journal of Information Processing Systems
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• 제13권5호
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• pp.1410-1429
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• 2017

Mobility arises naturally in the Internet of Things networks, since the location of mobile objects, e.g., mobile agents, mobile software, mobile things, or users with wireless hardware, changes as they move. Tracking their current location is essential to mobile computing. To overcome the scalability problem, hierarchical architectures of location databases have been proposed. When location updates and lookups for mobile objects are localized, these architectures become effective. However, the network signaling costs and the execution number of database operations increase particularly when the scale of the architectures and the numbers of databases becomes large to accommodate a great number of objects. This disadvantage can be alleviated by a location caching scheme which exploits the spatial and temporal locality in location lookup. In this paper, we propose a hierarchical location caching scheme, which acclimates the existing location caching scheme to a hierarchical architecture of location databases. The performance analysis indicates that the adjustment of such thresholds has an impact on cost reduction in the proposed scheme.

• 한국정보과학회논문지:정보통신
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• 제31권5호
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• pp.460-468
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• 2004

Quality of Service (QoS) 제약을 통한 자원관리 정책은 사용자에 의해 요구되는 서비스를 보장해줄 수 있는 장점을 가지고 있다. 쿼럼 시스템은 중복되어 저장되어 있는 데이타의 무결성과 가용성을 보장해 줄 수 있는 특성을 의미한다. 이 논문에서 우리는 사용자의 응용프로그램이 요구하는 시스템 자원 및 네트워크 자원의 QoS를 만족시킬 수 있는 쿼럼 기반의 자원관리방법을 제안한다. 또한 우리는 쿼럼 시스템내의 자원에서 실행되고 있는 응용프로그램의 실행시간을 통하여 자원의 상태예측을 하고 기대되는 자원의 서비스 수준을 유지하기 위한 자원의 재구성기법을 제안하고 있다. 자원의 재구성은 현재의 가용한 쿼럼내의 자원의 집합을 요구되는 서비스 수준으로 새롭게 재구성하는 것을 의미한다. 자원 재구성 정책의 효율성을 평가하기 위해서 우리는 인공심장혈류해석 병렬 프로그램을 사용하였다. 실험결과는 자원의 재구성 방식이 자원의 재구성 방식을 채택하지 않은 경우와 비교해서 응용프로그램의 실행완료시간을 감소시킬 뿐 아니라 실행환경의 안정성을 증가시키고 있다.