• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2003년도 Proceedings of ACRS 2003 ISRS
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• pp.561-563
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• 2003

This study is to present a standardized scheme for providing agriculture-related information at various spatial resolutions of satellite images including LANDSAT +ETM, KOMPSAT-1 EOC, ASTER VNIR and IKONOS panchromatic (Pan) and multi-spectral (M/S) images. The satellite images were interpreted especially for identifying agricultural areas, crop types, agricultural facilities and structures. The results were compared with the land cover/land use classification system suggested by Ministry of Construction & Transportation based on NGIS (National Geographic Information System) and Ministry of Environment based on satellite remote sensing data. The results by IKONOS image will be provided to KOMPSAT-2 project for agricultural application.

• Journal of Communications and Networks
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• 제8권3호
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• pp.275-285
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• 2006

Suitable for multi-input multi-output (MIMO) communications, the joint beamforming space-time block coding (JBSTBC) scheme is proposed for high-speed downlink transmission. The major functionality of the scheme entails space-time block encoder and joint transmit and receive eigen-beamformer (EBF) incorporating with block-ordered layered decoder (BOLD), and its operating principle is described in this paper. Within these functionalities, the joint EBFs will be utilized for decorrelating fading channels to cause an enhancement in the spatial diversity gain. Furthermore, to fortify the capability of layered successive interference cancellation (LSIC) in block-ordered layered decoding process, this paper will develop a simple ad-hoc transmit power discrimination scheme (TPDS) based on a particular power discrimination function (PDF). To confirm the superior behavior of the proposed JBSTBC scheme employing ad-hoc TPDS, computer simulations will be conducted under various channel conditions with the provision of detailed mathematical derivations for clarifying its functionality.

• 한국멀티미디어학회논문지
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• 제24권1호
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• pp.51-57
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• 2021

In this paper, we propose a task distribution scheme in fog computing environment considering opportunistic fog computing nodes. As latency is one of the important performance metric for IoT(Internet of Things) applications, there have been lots of researches on the fog computing system. However, since the load can be concentrated to the specific fog computing nodes due to the spatial and temporal IoT characteristics, the load distribution should be considered to prevent the performance degradation. Therefore, this paper proposes a task distribution scheme which considers the static as well as opportunistic fog computing nodes according to their mobility feature. Especially, based on the task requirements, the proposed scheme supports the delay sensitive task processing at the static fog node and delay in-sensitive tasks by means of the opportunistic fog nodes for the task distribution. Based on the performance evaluation, the proposed scheme shows low service response time compared to the conventional schemes.

• IEIE Transactions on Smart Processing and Computing
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• 제3권5호
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• pp.285-297
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• 2014

This paper presents the results of an investigation into bi-directional communication in spectrum sharing-based cognitive radio (Bi-CR) systems. A Bi-CR system can increase the spectral efficiency significantly by sharing the spectrum and through the bi-directional use of spatial resources for two-way communication. On the other hand, the primary user experiences more interference from the secondary users in a Bi-CR system. Satisfying the interference constraint by simply reducing the transmission power results in performance degradation for secondary users. In addition, secondary users also experience self-interference from echo channels due to full duplexing. These imperfections may weaken the potential benefits of the Bi-CR system. Therefore, a new way to overcome these defects in the Bi-CR system is needed. To address this need, this paper proposes some novel power allocation schemes for the Bi-CR system. This contribution is based on two major analytic environments, i.e., noise-limited and interference-limited environments, for providing useful analysis. This paper first proposes an optimal power allocation (OPA) scheme in a noise-limited environment and then analyzes the achievable sum rates. This OPA scheme has an effect in the noise-limited environment. In addition, a power allocation scheme for the Bi-CR system in an interference-limited environment was also investigated. The numerical results showed that the proposed schemes can achieve the full duplexing gain available from the bi-directional use of spatial resources.

• 한국가구학회지
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• 제28권4호
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• pp.294-304
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• 2017

The purpose of this study is to analyse and derive the color characteristics of childhood children's learning spaces and furniture for improving the color design of those and to present the direction of design and to build up the DB. The study covers products from domestic and overseas infant furniture manufacturers and 11 preschool learning rooms. The study method uses the collected furniture and spatial images to derive a palette of colors and compare color characteristics. The analysis results show that, the domestic infant furniture tend to use a variety of colors with pale tone or use consistent hard wood furniture according to the requirements of adult taste and marketability. Also, it attempts to create a very negative color scheme, but it looks like disorganized, and there is not much color design integrated with the architecture. Thus, color designs ensure that the ordering elements of the color scheme are clearly recognized by applying preferred color tones of childhood, like vivid and bright tone with high chroma and middle or hight Brightness value. Lastly, it should establish guidelines for specific palettes and color scheme, which can be utilized in the design of childhood children's learning spaces and furniture.

• 한국통신학회논문지
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• 제30권7A호
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• pp.568-577
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• 2005

본 논문에서는 시공간 블록 부호화한 공간 다중화 시스템에서 수신안테나의 수를 송신 안테나 수의 반을 사용했을 경우, 감소하는 비트 오류 성능을 개선하기 위해, 채널 상태와 관련한 귀환 정보를 이용하여 각 송신 안테나마다 적응적으로 전송률을 할당하고 전력을 제어하는 시스템을 제안하곤 그 성능을 분석한다. 성능 분석 결과, 8개의 송신 안테나와 4개의 수신 안테나를 사용한 경우, 안테나 쌍마다 전송률과 전력을 할당하는 간단한 알고리즘을 이용하면, 동일한 전송률과 전력을 사용한 개루프 방식에 비하여, BER이 10$^{-3}$인 구간에서 약 4.5dB의 성능이 향상하는 것을 알 수 있다.

• 한국정보처리학회논문지
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• 제3권6호
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• pp.1636-1645
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• 1996

본 논문에서는 패턴을 효과적으로 분류하기 위하여 화상자료의 특성인 이웃 화소 간의 종속성을 잘 표현해 주는 깁스확률장의 크리크를 바탕으로 2차원 조건부 모멘트 를 제안하였다. 이 알고리즘 구축은 공간정보를 갖는 조건부 모멘트를 이용하여 특정 벡터를 추출하는 과정과 패턴을 분류하는 과정으로 분리하여 생각한다. 특정벡터를 추출하는 과정은 하나의 패턴에 대해 깁스분포의 크리크로 표현된 파라미터를 추정한 다음, 2차원 조건부 모멘트들을 계산하여 특정벡터로부터 제안된 판별거리함수를 계 산하여 여러 원형 패턴 가운데 최소거리를 산출한 미지의 패턴을 원형패턴으로 분류 한다. 제안된 방법의 성능을 검증하기 위하여 대문자와 소문자 52자로 된 훈련 데이 타를 만들어 486 PC 66Mhz에서 실험을 한 결과 97.5% 이상의 분류성능이 있음을 밝혔 다.

• Journal of Communications and Networks
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• 제9권2호
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• pp.159-166
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• 2007

In this paper, we propose an efficient and robust interference mitigation technique based on a nullsteering multi-user multiple-input multiple-output (MU-MIMO) spatial division multiple access (SDMA) scheme for frequency sharing between IMT-advanced and fixed satellite service (FSS) in the 3400-4200 and 4500-4800 MHz bands. In the proposed scheme, the pre-existing precoding matrix for SDMA unitary precoded (UPC) MIMO proposed by the authors is modified to construct nulls in the spatial spectrum corresponding to the direction angles of the victim FSS earth station (ES). Furthermore, a numerical formula to calculate the power of the interference signal received at the FSS ES when IMT-Advanced base stations (BS) are operated with the interference mitigation technique is presented. This formula can be derived in closed form and is simply implemented with the help of simulation, resulting in significantly reduced time to obtain the solution. Finally, the frequency sharing results are analyzed in the co-channel and adjacent channel with respect to minimum separation distance and direction of FSS earth station (DOE). Simulation results indicate that the proposed mitigation scheme is highly efficient in terms of reducing the separation distance as well as robust against DOE estimation errors.

• 대한전자공학회논문지TC
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• 제43권4호
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• pp.31-38
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• 2006

본 논문에서는 지연된 귀환 채널 정보를 가지는 STBC-공간다중화 OFDM 시스템을 위한 전처리기 구조를 제안한다. 보통 MIMO 시스템을 위한 전처리기는 귀환 채널 상태 정보를 송신단이 완벽하게 안다는 가정 하에 설계된다. 하지만 실제 시스템에서는 귀환 채널 지연과 링크 오류가 존재하므로 송신단이 부정확한 귀환 채널 정보를 사용하게 되어 시스템 성능이 감소한다. 제안된 전처리기는 이러한 성능 감쇠를 STBC가 제공하는 다이버시티 이득으로 보상할 수 있는 구조로 설계된다. 본 논문에서 제안하는 전처리 기법은 수신단에서 전처리 코드북의 색인을 송신단에 귀환하고 송신단은 전처리 행렬, 부반송파의 상관도, 채널의 자기 상관도를 고려하여 전송 심볼을 전처리한다 모의실험을 통해 STBC-SM OFDM 시스템이 도플러 주파수가 60Hz 이상이 되면 $SER=10^{-3}$ 이하에서 기존의 전처리된 MIMO-OFDM 시스템의 코드북 선택기법에 비해 성능이 우수함을 확인하였다.

• 한국정보통신학회논문지
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• 제21권3호
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• pp.516-522
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• 2017

본 논문에서는 다중 안테나 구조 중 일부 송신 안테나만 활성화하고 활성 안테나의 인덱스를 통해 정보를 전송하는 일반화 공간변조(Generalized Spatial Modulation)시스템을 위한 최대우도 신호 검파 방법을 제안한다. 제안 최대 우도 수신기는 기존의 채널 정보 오차에 강인한 최대 우도 수신기와 비교하여 공분산 행렬을 추정할 때 후보 해 집합을 확률적으로 추출하여 공분산 행렬을 추정함으로써 시스템 복잡도를 크게 줄이도록 한다. 모의 실험을 통해 제안 최대 우도 수신기가 기존의 채널 정보 오차를 고려하지 않는 수신기보다 높은 수신 성능을 가지며, 기존 강인 최대우도 수신기와 비교하여 동일한 비트 오류율 성능을 가지면서도 큰 폭으로 계산 복잡도를 낮춤을 확인하였다.