• 정보처리학회논문지C
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• 제12C권5호
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• pp.665-672
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• 2005

본 논문에서는 웨이블릿 변환과 보간법을 이용하여 OFDM(Orthogonal Frequency Division Multiplexing)시스템을 위한 새로운 파일럿 지원 채널 추정 기법을 소개한다. 웨이블릿 변환의 AWGN(Additive White Gaussian Noise) 감쇄능력이 뛰어남으로 인해 파일럿 채널은 아주 정확하게 추정될 수 있고, 이렇게 추정된 파일럿 데이터는 남아있는 다른 데이터 심볼 채널에 대해 2차 다항식 보간법을 하는데 사용된다. Short WATM(Wireless Asynchronous Transfer Mode)채널에 대한 모의실험 결과를 통해, 이 추정기를 쓴 OFDM 시스템의 성능은 완벽한 CSI(Channel State Information)에서 발생하는 BER(Bit Error Ratio) 성능과 거의 비슷한 것을 확인할 수 있다.

• 통합자연과학논문집
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• 제10권4호
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• pp.216-224
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• 2017

In the terrain of the Korean peninsula, mountainous and flat lands are complexly distributed in small areas. Therefore, local severe weather develops and disappears in a short time due to the influence of the terrain. Particularly in the case of local severe weather with heavy wind that has the greatest influence on aviation meteorology, the scale is very small, and it occurs and disappears in a short time, so it is impossible to predict with fragmentary data alone. So, we use weather radar to detect and predict local severe weather. However, due to the development of wireless communication services and the rapid increase of wireless devices, radio wave jamming and interference problems occur. In this research, we confirmed through the cases that when the radio interference echo which is one of the non-precipitation echoes that occur during the operation of the weather radar is displayed in the image, its form and shape are shown in a long bar shape, and have a strong dBZ. We also found the cause of the interference through the radio tracking process, and solved through the frequency channel negotiation and AP output minimizing. The more wireless devices increase as information communication technology develops in the future, the more emphasized the problem of radio wave interference will be, and we must make the radio interference eliminated through the development of the radio interference cancellation algorithm.

• 전자공학회논문지S
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• 제35S권9호
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• pp.104-110
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• 1998

본 논문에서는 구현이 용이한 전이중 통신용 비선형 반향제거기의 회로구조를 제안하고자 한다. 이 회로구조는 선형 반향제거기의 FIR 구조를 사용하면서 단지 약간의 탭만 부가함으로서 선형신호 뿐만 아니라 하이브리드나 데이타 변환기 등에서 발생하는 비선형 반향신호도 제거할 수 있도록 설계되었다. 부가되는 탭의 수는 비선형 반향성분을 어느 정도까지 제거할 것인가에 의해서 좌우된다. 본 구조를 사용하여 컴퓨터 프로그램을 작성하고 시뮬레이션을 수행한 결과, 적은 탭을 추가시키는 것으로 비선형 반향신호에 대해 좋은 반향제거 효과를 나타냄을 확인하였다.

• 전자공학회논문지SC
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• 제47권6호
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• pp.27-32
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• 2010

오늘날 FMCW 레이더 시스템은 차량의 능동 안전 시스템에 널리 활용되어지고 있다. 레이더 시스템에서 탐지확률을 높이고 오경보율을 줄이기 위해서는 정지타겟을 포함한 클러터 성분을 제거하고 관심 있는 이동타겟을 효과적으로 탐지하기 위한 알고리즘이 필요하다. 본 논문에서는 이동타겟 탐지 및 클러터 제거 알고리즘을 제안한다. 먼저 제안된 이동타겟 비트주파수 검출 필터를 이용하여 클러터를 제거한다. 검출된 이동타겟 비트주파수들을 이용하여 데이터-결합 한 후, 제로-도플러 제거 알고리즘을 이용하여 남아있는 클러터를 제거한다. 이 알고리즘을 검증하기 위해 실제 FMCW 레이더를 이용하여 도로 상에서 실험하였다.

• 천문학회보
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• 제37권1호
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• pp.88.2-88.2
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• 2012

We investigate solar flare occurrence rate and daily flare probability depending on McIntosh sunspot classification, its area, and its area change. For this we use the NOAA active region and GOES solar flare data for 15 years (from January 1996 to December 2010). We consider the most flare-productive 10 sunspot classification: 'Dko', 'Dai', 'Eai', 'Fai', 'Dki', 'Dkc', 'Eki', 'Ekc', 'Fki', and 'Fkc'. Sunspot area and its change can be a proxy of magnetic flux and its emergence/cancellation, respectively. we classify each sunspot group into two sub-groups: 'Large' and 'Small'. In addition, for each group, we classify it into three sub-groups according to sunspot group area change: 'Decrease', 'Steady', and 'Increase'. As a result, in the case of compact groups, their flare occurrence rates and daily flare probabilities noticeably increase with sunspot group area. We also find that the flare occurrence rates and daily flare probabilities for the 'Increase' sub-groups are noticeably higher than those for the other sub-groups. In case of the (M+X)-class flares of 'Dkc' group, the flare occurrence rate of the 'Increase' sub-group is three times higher than that of the 'Steady' sub-group. Mean flare occurrence rates and flare probabilities for all sunspot regions increase with the following order: 'Steady', 'Decrease', and 'Increase'. Our results statistically demonstrate that magnetic flux and its emergence enhance major solar flare occurrence. We are going to forecast solar flares based on these results and NOAA scale.

• 보건행정학회지
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• 제15권4호
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• pp.26-45
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• 2005

The purposes of this study were to Identify the .level of measurement on quality Indicators and evaluate the existing indicators in order to determine the priority of quality indicators' application in Korean general hospitals. A survey was conducted using a questionnaire. The subjects were quality managers working at general hospital having over 300 beds. The criteria were relevance, reliability, precision, impact, application, and preference to evaluate quality indicators. According to these six criteria, each indicator was evaluated on a five point scale(5: excellent, 1: poor). The response rate was $40.4\%$. The hospitals have monitored the average of 3.8 indicators(median 4). The indicators such as return to operating room, unplanned readmission, cancellation of booked operations, death, hospital infection, cesarean section rate, volume per disease or procedure, readmission, re-operation, blood transfusion, and post-procedural complications were frequently measured. The top ten quality indicators in the evaluation by its relevance, validity, reliability, impact, preference and application were decubitus ulcer, clean wound infection, fall, unplanned return to operation room, transfusion reactions, foreign body left In during procedure, unplanned readmission, wound infection after contaminated surgery, postoperative hemorrhage/hematoma, and cesarean section rate in order. The high priority quality indicators frequently measured could be used as primary national indicators. Standardized guidelines about monitoring indicators and the utilization will preliminarily be needed to compare and reuse the data for various purposes and improve the quality of care continuously.

• 디지털산업정보학회논문지
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• 제14권3호
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• pp.11-20
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• 2018

Smart devices refer to various devices and control equipment such as health care devices, imaging devices, motor devices and wearable devices that use wireless network communication (e.g., Wi-fi, Bluetooth, LTE). Commercial services using such devices are found in a wide range of fields, including home networks, health care and medical services, entertainment and toys. Studies on smart devices have also been actively undertaken by academia and industry alike, as the penetration rate of smartphones grew and the technological progress made with the fourth industrial revolution bring about great convenience for users. While services offered through smart devices come with convenience, there is also various security threats that can lead to financial loss or even a loss of life in the case of terrorist attacks. As attacks that are committed through smart devices tend to pick up where attacks based on wireless internet left off, more research is needed on related security topics. As such, this paper seeks to design an access control method for reinforced security for smart devices. After registering and authenticating the smart device from the user's smart phone and service provider, a safe communication protocol is designed. Then to secure the integrity and confidentiality of the communication data, a management process such as for device renewal or cancellation is designed. Safety and security of the existing systems against attacks are also evaluated. In doing so, an improved efficiency by approximately 44% compared to the encryption processing speed of the existing system was verified.

• 한국통신학회논문지
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• 제30권5C호
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• pp.338-343
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• 2005

다중 송수신 안테나(Multiple Input Multiple Output : MIMO) 시스템은 높은 데이터율 뿐만 아니라 효율적인 주파수 자원의 활용을 필요로 하는 차세대 이동 통신 시스템에 가장 적합한 시스템 중 하나로 주목받고 있다. 그에 따라 MIMO 전송 데이터율을 높이기 위해 2개의 송신 안테나를 기본으로 하는 STTC 부호화 그룹을 다수 형성하여 전송하고 수신단에서 다른 그룹의 간섭을 제거하는 BLAST-STTC 기법이 제안되었다. 본 논문에서는 모든 그룹이 최대 다이버시티 이득을 얻는 동시에 간섭 제거 기법의 성능을 향상시킬 수 있는 역순서화된 반복 복호화 기법을 제안한다. 그리고 모의실험을 통해 제안된 기법과 기존 기법의 프레임 오류확률(Frame Error Rate : FER) 성능을 비교한다.

• 한국통신학회논문지
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• 제36권6C호
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• pp.337-342
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• 2011

2009년 Arikan에 의해 처음 제안된 극 부호(polar codes)는 실용적인 부 복호화 복잡도로 채널 용량을 달성하는 것이 종영된 채널 부호이다. 채널 양극화(channel polarization) 현상을 이용하는 극 부호는 현재 보안 및 데이터 압축 등에 응용되어 활발히 연구되고 있다. 본 논문에서는 극 부호의 실제 통신 시스템 적용을 고려하여, 유한한 길이와 고정 부호율을 갖는 극 부호의 설계 방법을 제안한다. 그리고 모의실험을 통하여 경험적으로 찾아낸 가장 우수한 성능을 보이는 극 부호의 성능과 설계 방법을 제시한다.

• ETRI Journal
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• 제38권6호
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• pp.1042-1051
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• 2016

The mobile hotspot network (MHN), which is capable of providing a data rate of gigabits per second at high speed, is considered a potential use case of the future enhanced mobile broadband for 5G. Because a unidirectional network deployment has been considered for an MHN, non-orthogonal multiple access (NOMA) can be employed to improve the system performance. For a practical implementation of NOMA under an MHN highway scenario where multiple pieces of MHN terminal equipment are served through the same beam simultaneously, a NOMA transceiver is proposed in this paper. For the NOMA transmitter, Gray-coded QAM constellation mapping is extended to arbitrary modulation order q. For the NOMA receiver, successive interference cancellation (SIC) is no longer necessary, and instead, a parallel demodulation is proposed. The numerical and simulation results suggest that the proposed NOMA transceiver outperforms the conventional NOMA SIC receiver and can be flexibly used for an MHN highway scenario.