• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.9
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• pp.4429-4445
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• 2019

As low-power and low-rate WSNs are being widely used for industrial applications, the scheduling of such applications becomes a critical issue to guarantee meeting the stringent requirements of determinism and tight latencies. This paper studies the link scheduling problem for real-time industrial applications in time-slotted channel hopping (TSCH) networks. We propose a heuristic algorithm for centralized link scheduling referred to as path-collision aware least laxity first (PC-LLF) algorithm, which dynamically prioritizes the packets based on the laxity time to the end-to-end deadlines and the amount of collisions that messages might deal with along their designated paths to the destination device. We propose schedulability analysis of real-time applications scheduled under our prioritization approach over TSCH networks, based on the literature on real-time schedulability analysis of multiprocessors and distributed systems. We show that our methodology provides an improved schedulability condition with respect to the existing approaches. Performance evaluation studies quantify to quantify the performance of our proposed approach under a variety of scenarios.

• Proceedings of the Korea Information Processing Society Conference
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• 2013.11a
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• pp.233-236
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• 2013

본 논문에서는 무선 주파수 자원의 부족문제가 대두됨에 따라 TV White Space(TVWS) 주파수 대역을 효과적으로 사용하기 위한 IEEE 802.15.4m TVWS Multi-channel Cluster PAN(TMCTP)을 소개하고 NS-3 를 이용하여 Association 시간과 Uplink, Downlink 데이터 전송시간에 대한 성능평가를 한다. 성능평가 결과에 대하여 분석하고 향후 TMCTP 의 추가할 부분에 대하여 도출한다.

• Proceedings of the Korea Information Processing Society Conference
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• 2009.04a
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• pp.762-765
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• 2009

무선 센서 네트워크상에서 센서노드의 소프트웨어 변경, 패치 등의 작업을 위해서 센서노드별로 ISP와 같은 케이블을 이용하여 프로그램 해야 한다. 이는 네트워크 내에 존재하는 노드의 수가 소량인 경우 크게 문제되지 않지만 대량의 노드로 구성된 경우 프로그래밍을 위한 시간적인 측면과 투여되는 인력적인 측면에서 매우 높은 비용이 소요된다. 본 논문에서는 현재 많이 사용하고 있는 IEEE 802.15.4기반의 단일-홉 무선 센서 네트워크 환경에서 노드의 수와 무관하게 고속 병렬로 센서노드 내부의 프로그램을 무선으로 업데이트 할 수 있는 기법을 제시하고 실험을 통하여 그 성능을 검증한다.

• Proceedings of the Korea Information Processing Society Conference
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• 2007.11a
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• pp.819-822
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• 2007

최근 유비쿼터스 환경 실현을 위해서 무선 센서 네트워크에 관한 많은 연구가 진행되고 있다. IEEE 802.15.4 에 기반한 ZigBee 에 관한 연구는 이미 많은 진행이 되어 있다. 최근에는 IPv6 기술이 이슈화 되면서 무선 센서 네트워크 환경에도 IPv6 주소를 사용 할 수 있을 것으로 기대되고 있다. 본 논문에서는 IPv6 주소를 갖는 센서가 서비스를 제공하기만 하는 기존의 패러다임에서 벗어나 센서가 서비스를 찾는 모델을 제시한다. 그래서 IPv6 주소를 갖는 센서 네트워크의 보다 효율적인 서비스 디스커버리를 위해 객체 타입을 IPv6 주소의 일부분으로 정의해 준다. 이러한 객체타입을 이용한 IPv6 기반의 센서 네트워크의 효율성을 본 논문에서 검증한다.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.12 no.4
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• pp.211-221
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• 2012

The development of wireless sensor networks (WSNs) is progressed slowly due to limited resources, but it is in progress to the development of the latest IP-based IP-WSN by the development of hardware and power management technology. IPv6 over Low power WPAN (6LoWPAN) is capable of IPv6-built low-power devices. In these IP-based WSNs, existing IP-based techniques which was impossible in WSNs becomes possible. 6LoWPAN is based on the IEEE 802.15.4 sensor networks and is a IPv6-supported technology. Host-based mobility management scheme in IP-WSNs are not suitable due to the additional signaling, network-based mobility management scheme is more suitable. In this paper, we propose an enhanced PMIPv6-based route optimization scheme which consider multi-6LoWPAN network environments. All SLMA (Sensor Local Mobility Anchor) of the 6LoWPAN domain are connected with the SPIG (Sensor Proxy Internetworking Gateway) and performs distributed mobility control for the 6LoWPAN-based inter-domain operations. All information of SLMA in 6LoWPAN domain is maintained by SMAG (Sensor Mobile Access Gateway), and then is performed the route optimization quickly. The status information of the route optimization from SPIG is stored to SLMA and it is supported without additional signaling.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.49 no.7
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• pp.56-64
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• 2012

A smart grid is the next generation power grid which combines the existing power grid with information technology, so an energy efficient power grid can be provided. In this paper, in order to build an efficient smart grid an AMI system, which gears with the existing home network and provides an user friendly management function, is proposed. The proposed AMI system, which is based on an extended home network, consists of various functional units; smart meters, communication modules, home gateway, security modules, meter data management modules (MDMM), electric power application modules and so on. The proposed home network system, which can reduce electric power consumption and transmit data more effectively, is designed by using IEEE 802.15.4. The extended home gateway can exchange energy consumption information with the outside management system via web services. The proposed AMI system is designed to enable two-way communication between the home gateway and MDMM via the Internet. The AES(Advanced Encryption Standard) algorithm, which is a symmetric block cipher algorithm, is used to ensure secure information exchange. Even though the results in this study could be limited to our experimental environment, the result of the simulation test shows that the proposed system reduces electric power consumption by 4~42% on average compared to the case of using no control.

• Journal of Sensor Science and Technology
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• v.15 no.5
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• pp.362-370
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• 2006

The wireless sensor network (WSN) based ECG and body temperature measuring system for ubiquitous health-care were designed and developed. The system was composed of a wireless sensor network node, base station and server computer for the continuous monitoring of ECG signals and body temperatures of patients at home or hospital. ECG signal and body temperature data, important vital signals which are commonly used in clinical and trauma care, were displayed on a graphical user interface (GUI). The data transfer from sensor nodes on patients' body to server computer was accomplished through a base-station connected to a server computer using Zigbee compatible IEEE802.15.4 standard wireless communication. Real-time as well as historical, ECG data of elderly persons or patients, can also be retrieved and played back to assist the diagnosis. The ubiquitous health care system presented in this study can effectively reduce social medical expenses, which will be increased greatly in the coming aging society.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.48 no.4
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• pp.35-42
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• 2011

Link quality assessment is a crucial part of sensor network formation to stably operate large-scale wireless sensor networks (WSNs). A stability of path consisting of several nodes strongly depends on all link quality between pair of consecutive nodes. Thus it is very important to assess the link quality on the stage of building a routing path. In this paper, we present a link quality assessment method, Hybrid Link Quality Metric (HQLM), which uses both of LQI and RSSI from RF chip of sensor nodes to minimize set-up time and energy consumption for network formation. The HQLM not only reduces the time and energy consumption, but also provides complementary cooperation of LQI and RSSI. In order to evaluate the validity and efficiency of the proposed method, we measure PDR (Packet Delivery Rate) by exchanging multiple messages and then, compare PDR to the result of HQLM for evaluation. From the research being carried out, we can conclude that the HQLM performs better than either LQI- or RSSI-based metric in terms of recall, precision, and matching on link quality.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2007.10a
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• pp.477-481
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• 2007

The emergency patient who occurs from the place where it is various the control which is quick must come to accomplish in Ubiquitous environment. In the body of the patient or the old person the organism signal sensor about under attaching condition of the patient at real-time about under the monitor ring about under disposing the control which is quick against the emergency patient does to become accomplished at the case real-time when the above will get in the body of the patient or the old person. Using ZigBee (802.15.4) system base on Shor wireless communication protocol because of complement wireless of hospital. This system use ZigBee (802.15.4) system to get for electrocardiogram, blood pressure and pulse bio-sensors. This paper constructs Bio-Sensor communication monitoring system and transmission rate and the delay which it follows possibility and node occurrence rate of wireless sensor network construction hour transmission session it leads and it verifies the effectiveness.

• The Journal of the Korea Contents Association
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• v.9 no.7
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• pp.76-85
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• 2009

UWB signal with high resolution capability can be used to estimate ranging and positioning in wireless personal area network. The node works on its local clock and the frequency differences of nodes have serious affects on ranging algorithms estimating locations of mobile nodes. The low rate UWB, IEEE802.15.4a, describes asynchronous two way ranging methods such as TWR and SDS-TWR working without any additional network synchronization, but the algorithms can not eliminate the effect of clock frequency differences. Therefore, the mechanisms to characterize the crystal difference is essential in typical UWB PHY implementations. In high rate UWB, characterizing of crystal offset with tracking loop is not required. But, detection of the clock frequency offset between the local clock and remote clock can be performed if there is little noise induced jitter. In this paper, we complete related ranging equations of high rate UWB based on TWR with relative frequency offset, and analyze a residual error in the ideal equations. We also evaluate the performance of the relative frequency offset algorithm by simulation and analyze the ranging errors according to the number of TWR to compensate coarse clock resolution. The results show that the relative frequency offset compensation and many times of TWR enhance the performance to converge to a limited ranging errors even with coarse clock resolutions.