• The Journal of the Korea Contents Association
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• v.10 no.3
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• pp.53-63
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• 2010

Recently, various monitoring systems are implemented actively by using wireless sensor networks(WSN). When implementing WSN-based monitoring system, there are three important issues to consider. At First, we need to consider a sensor node failure detection method to support the ongoing monitoring. Secondly, because sensor nodes use limited battery power, we need an efficient data filtering method to reduce energy consumption. At Last, a reducing processing overhead method is necessary. The existing Kalman filtering scheme has good performance on data filtering, but it causes too much processing overhead to estimate sensed data. To solve these problems, we, in this paper, propose a new data filtering scheme based on data statical analysis. First, the proposed scheme periodically aggregates node survival massages to support a node failure detection. Secondly, to reduce energy consumption, it sends the sample data with a node survival massage and do data filtering based on those messages. Finally, it analyzes the sample data to estimate filtering range in a server. As a result, each sensor node can use only simple compare operation for filtering data. In addition, we show from our performance analysis that the proposed scheme outperforms the Kalman filtering scheme in terms of the number of sending messages.

• The Journal of the Korea Contents Association
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• v.13 no.1
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• pp.30-39
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• 2013

In recent years, with the development of devices to collect multimedia data such as small CMOS camera sensor and micro phone, studies on wireless multimedia sensor network technologies and their applications that extend the existing wireless sensor network technologies have been actively done. In such applications, various basic schemes such as the processing, storage, and transmission of multimedia data are required. Especially, a security for real world environments is essential. In this paper, in order to defend the sniffing attack in various hacking techniques, we propose a multipath routing scheme for physically avoiding the data transmission path from the risk factors. Our proposed scheme establishes the DEFCON of the sensor nodes that are geographically close to risk factors and the priorities according to the importance of the data. Our proposed scheme performs risk factor detour multipath routing through a safe path considering the DEFCON and data priority. Our experimental results show that although our proposed scheme takes the transmission delay time by about 5% over the existing scheme, it reduces the eavesdropping rate that can attack and intercept data by the risk factor by about 18%.

• Journal of the Korea Society of Computer and Information
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• v.15 no.4
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• pp.83-90
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• 2010

In wireless sensor networks, the data transmitted from the sensor nodes are susceptible to corruption by errors which caused of noisy channels and other factors. In view of the severe energy constraint in Sensor Networks, it is important to use the error control scheme of the energy efficiently. In this paper, we presented RS (Reed-Solomon) codes in terms of their BER performance and power consumption. RS codes work by adding extra redundancy to the data. The encoded data can be stored or transmitted. It could have errors introduced, when the encoded data is recovered. The added redundancy allows a decoder to detect which parts of the received data is corrupted, and corrects them. The number of errors which are able to be corrected by RS code can determine by added redundancy. The results of experiment validate the performance of proposed method to provide high degree of reliability in low-power communication. We could predict the lifetime of RS codes which transmitted at 32 byte a 1 minutes. RS(15, 13), RS(31, 27), RS(63, 57), RS(127,115), and RS(255,239) can keep the days of 173.7, 169.1, 163.9, 150.7, and 149.7 respectively. The evaluation based on packet reception ratio (PRR) indicates that the RS(255,239) extends a sensor node's communication range by up about 3 miters.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.25 no.5
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• pp.719-730
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• 2021

We have demonstrated a sandwich-type ZnO-based piezoelectric energy harvesting nanogenerator, namely ZCZ-NG device, composed of symmetrically stacked layers of ZnO/carbon tape/ZnO structure. Especially, we have adopted a conductive double-sided adhesive carbon tape in an effort to fabricate a high-quality ZCZ-NG device, leading to its superior output performance in terms of the peak-to-peak output voltage. Effects of the device size, ZnO layer thickness, and bending strain rate on the device performance have been investigated by measuring the output voltage. Moreover, to evaluate the effectiveness of the fabricated ZCZ-NG devices, we have experimentally implemented a sensor network testbed which can utilize the output voltages of ZCZ-NG devices. This sensor network testbed consists of several components such as Arduino-based transmitter and receiver nodes, wirelessly transmitting the sensed information of each node. We hope that this research combining the ZnO-based energy harvesting devices and IoT sensor networks will contribute to the development of more advanced energy harvester-driven IoT sensor networks in the future.

• Annual Conference of KIPS
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• 2011.04a
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• pp.576-579
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• 2011

Wireless sensor network are widely all over different fields. Because of its distinguished characteristics, we must take account of the factor of energy consumed when designing routing protocol. Wireless sensor networks consist of small battery powered devices with limited energy resources. Once deployed, the small sensor nodes are usually inaccessible to the user, and thus replacement of the energy source is not feasible. Hence, energy efficiency is a key design issue that needs to be enhanced in order to improve the life span of the network. In BCDCP, all sensors sends data from the CH (Cluster Head) and then to the BS (Base Station). BCDCP works well in a smallscale network however is not preferred in a large scale network since it uses much energy for long distance wireless communication. TBRP can be used for large scale network, but it weakness lies on the fact that the nodedry out of energy easily since it uses multi-hops transmission data to the Base Station. Here, we proposed a routing protocol. A Cluster Based Energy Efficient Tree Routing Protocol (CETRP) in Wireless Sensor Networks (WSNs) to prolong network life time through the balanced energy consumption. CETRP selects Cluster Head of cluster tree shape and uses maximum two hops data transmission to the Cluster Head in every level. We show CETRP outperforms BCDCP and TBRP with several experiments.

• Proceedings of the Korean Information Science Society Conference
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• 2006.06d
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• pp.154-156
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• 2006

본 논문은 기존의 혼잡 제어 기술이 전체 노드들을 위해 설계 되어 싱크 주변에서 생성되는 특별한 혼잡을 해결 할 수가 없기 때문에 싱크 주변 노드를 위한 혼잡 제어 기술을 제안한다. 싱크 주변에서 일어나는 'Bottle Neck' 문제가 일어났을 경우 데이터의 분석에 의한 우선순위결정과 타임 스케줄을 이용한 순차적인 데이터 전송으로 혼잡을 줄이고 그로 인해 데이터의 의미 있는 전송과 신뢰성을 동시에 만족시킨다. 또한 이 기술은 멀티 싱크 또는 모바일 싱크에도 적용 시킬 수 있고, 기존의 전체 노드를 위한 혼잡 제어 기술과 제시하는 기술을 혼용하여 사용할 수도 있다. 본 논문이 제안하는 기법은 혼잡 제어를 하지 않은 상태에서의 데이터 전달 방식에 비해 데드라인 만료 비율이 1.5%이상 감소하였고 프레임 손실율 또한 28%이상 감소하였다.

• Proceedings of the Korean Information Science Society Conference
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• 2006.06d
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• pp.145-147
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• 2006

본 논문에서는 센서네트워크와 RFID 네트워크가 결합되어 있는 환경에서 센서 노드의 특성을 이용한 RFID 리더 충돌 방지 방법을 제안한다. 세부적으로 이웃 센서 노드 정보 확인 단계, 관리 노드로부터 리더 충돌 확인 단계, 태그 리드 단계를 포함한다. 리더와 센서가 결합되어 있는 환경에서, 센서 노드들간의 거리에 따라 리더들 간의 동기를 맞추어 충돌을 방지함으로써, 전체 시스템의 부하를 감소시키고, 시스템을 관리하는데 자원 낭비를 방지하며, 시스템의 처리율 및 효율을 향상시킬 수 있다.

• Proceedings of the KSR Conference
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• 2011.05a
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• pp.1550-1555
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• 2011

This paper presents the system interface standard that are associated with additional devices like sensor nodes as well as fire monitoring panel, panic button and emergency call in city railroad environment. Existing fire monitoring panel, panic button and emergency call system is responsible for fire detection and alarm, emergency alarm and communication with the manager. Recently, researches that are associated with NVR-based intelligent integrated surveillance systems and existing alarm system are activated but most of the system is dedicated to it existing. In order to expand devices that is supported other monitoring function, separate device configuration or modification of integrated surveillance system are inevitable. In this study, interface standard between standard controller, integrated command center and each device that facilitate additional expansion of integrated surveillance system and avoid the extra cost is presented.

• Proceedings of the KSR Conference
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• 2011.05a
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• pp.1414-1419
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• 2011

In this paper we study the modeling to quantitatively assess the failure rate of USN system designed for fault-tolerant architecture, aiming at applying the world's best domestic USN technology to safety-critical railways. In order to apply the USN system to the safety-critical field like a train control sector that the failures of controllers may cause severe railway accidents such as train collision and derailment, the quantitative reliability and safety evaluation recommended in IEC 62278 must be preceded. We also develop the evaluation model for overall system failure rate for the distributed network structure, which is the characteristics of USN system. Especially, we allocate reliability targets to component units, and present an availability evaluation plan through the plan on the quantitative achievement of failure rate for sensor nodes, gateways, radio-communication network and servers, along with the failure rate model of the overall system considering network operational features.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2009.04a
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• pp.110-113
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• 2009

본 연구에서는 무선센서노드을 이용하여 강판형 철도교량의 전형적인 손상유형인 거더부의 휨강성 저하와 지점부의 볼트풀림을 효과적으로 모니터링할 수 있는 하이브리드 모니터링 기법을 제안하였다. 이를 위해 다음과 같은 연구가 수행되었다. 첫째, 본 연구진에 의해 개발된 가속도 및 임피던스기반 무선센서노드를 간략하게 소개하였다. 둘째, 가속도 및 임피던스 신호를 이용하여 효과적인 손상모니터링이 가능한 기법들을 선정하였다. 마지막으로, 개발된 가속도 및 임피던스기반 무선센서노드를 모형 강판형 철도교에 설치하고, 일련의 손상 시나리오에 따른 하이브리드 모니터링을 수행하여 무선센서노드 및 모니터링 기법의 성능을 평가하였다.