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차현수(HyunSoo Cha),유승화(SeungWha Yoo),김기형(Kihyung Kim),김영한(Younghan Kim),이상산(Sangsan Lee) 대한기계학회 2012 대한기계학회 춘추학술대회 Vol.2012 No.11
The past few years have witnessed increased interest in large-scale Industrial Wireless Sensor Network(WSN). General Industrial WSN consists of a large number of low-cost, low power, and short RF range sensor nodes because of the cost saving. In industrial applications, sensor nodes are statically deployed and left unattended to continuously report sensing data(e.g. temperature, pressure, and humidity) to the Base Station(BS). Therefore, energy efficiency is a key challenge in the design and operation Industrial WSN. One of the major reason for worse energy efficiency is the traffic concentration on a small number of sensor nodes. Furthermore, several applications in industrial area require the bounded delay, so the proposed scheme have to support it. In these respect, node clustering can be a efficient solution to solve energy problem and satisfy delay bound in industrial WSN. In this paper we propose a novel clustering algorithm based on information entropy.
개선된 DCT 변환 영역 워터마크를 이용한 이미지 무결성 검증시스템
전인배(Inbae Jeon),최옥경(Okkyung Choi),유승화(Seungwha Yoo) 한국컴퓨터정보학회 2012 한국컴퓨터정보학회 학술발표논문집 Vol.20 No.2
본 논문은 변환영역 기반의 방법 중 DCT 변환영역 워터마크를 이용한 이미지 무결성 검증 시스템을 제안하였다. DCT 변환영역에 워터마크를 삽입하는 것이 공간영역에 삽입하는 것보다 잡음과 일반적인 신호처리나 영상편집, 선형/비선형 필터링, 압축 등의 영상처리에 강하다. 추출된 워터마크가 원본 워터마크와의 유사도 평가에서 임계값보다 크면 이미지에 변형이 없었다고 판단한다. 만약 이미지에 변형이 있을 경우 워터마크가 훼손되어 정확한 정보를 추출하기 어려울 수 있다. 이때 추출기에서 이미지 왜곡을 역변환 시켜 워터마크를 온전하거나 최소화된 훼손으로 추출한다.
산업장 네트워크 환경에서 IEEE 802.15.4e 동적 TSCH 기법
김영준(YoungJun Kim),김기형(Kihyung Kim),유승화(SeungWha Yoo),김영한(Younghan Kim),이상산(Sangsan Lee) 대한기계학회 2012 대한기계학회 춘추학술대회 Vol.2012 No.11
Wireless Sensor Networks(WSN) have begun to take significant roles in various applications but there have been many researches to improve the reliability of data transmission in WSN. The main causes of failure along communication links are external interference and persistent multipath fading. In IEEE 802.15.4e network which is amended version of IEEE 802.15.4 network, the microscopic channel hopping mechanism is used to solve the failure of data communication in WSN. However, the proposed scheme in IEEE 802.15.4e network has a predefined hopping channel pattern. Therefore, sensor node can use the worst channel because the status of channel may be affected several factors (e.g. time, interference, traffic from other device). To solve this problem, we propose a novel channel hopping algorithm which can be operated dynamically based on the real-timely estimated link status.