• KSII Transactions on Internet and Information Systems (TIIS)
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• v.4 no.3
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• pp.258-272
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• 2010

The low-rate (LR) UWB is a promising technology for the ubiquitous sensor network (USN) due to its extremely low power consumption and simple transceiver implementation. However the limited communication range is a bottleneck for its widespread use. This paper deals with a new frame structure of class 4 active RFID multi-hop relay system based on ISO/IEC 18000-7 standard integrating with IEEE 802.15.4a LR-UWB PHY layer specification, which sets up a connection to USN. As a result of the vital importance of the coverage and throughput in the application of USN, further we analyze the performance of the proposed system considered both impulse radio UWB (IR-UWB) and chirp spread spectrum (CSS). Our simulation results show that the coverage and throughput are remarkably increased.

• Proceedings of the Korea Information Processing Society Conference
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• 2012.04a
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• pp.605-606
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• 2012

In this paper, we consider the problem of scheduling sensor activity to prolong the network lifetime while guaranteeing both discrete target coverage and connectivity among all the active sensors and the sink, called connected target coverage (CTC) problem. We proposed a distributed scheme called Distributed Lifetime-Maximizing Scheme (DLMS) to solve the CTC problem. Our proposed scheme significantly reduces the cost of the construction of the connected cover graphs in comparison with the some conventional schemes. In addition, the energy consumption is more balanced so that the network lifetime will be increased. Our simulation results show that DLMS scheme performs much better than the conventional schemes in terms of the network lifetime.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.10 no.6
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• pp.55-62
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• 2010

Monitoring systems are able to report certain events at region of interest(ROI) and to take an appropriate action. From industrial product line full of robots to fire detection, intrusion detection, smart grid application, environmental pollution alarm system, monitoring system has widely used in diverse industry sector. Recently, due to advance of wireless communication technology and availability of low cost sensors, intelligent and/or smart monitoring systems such as sensor networks has been developed. Several deployment methods are introduced to meet various monitoring needs and deployment performance criteria are also summarized to be used to identify weak point and be useful at designing monitoring systems. Both efficiency during deployment and usefulness after the deployment should be assessed. Efficiency factors during deployment are elapsed time, energy required, deployment cost, safety, sensor node failure rate, scalability. Usefulness factors after deployment are ROI coverage, connectivity, uniformity, target density similarity, energy consumption rate per unit time and so on.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.8A
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• pp.691-701
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• 2011

In rotatable directional sensor networks, maximizing network lifetime while covering all the targets and forwarding the sensed data to the sink is a challenge problem. In this paper, we address the Maximum Directional Cover Tree (MDCT) problem of organizing the directional sensors into a group of non-disjoint subsets to extend the network lifetime. Each subset in which the directional sensors cover all the targets and forward the sensed data to the sink is activated at one time. For the MDCT problem, we first present an energy consumption model which mainly takes into account the energy consumption for rotation work. We also develop the Directional Coverage and Connectivity (DCC)-greedy algorithm to solve the MDCT problem. To evaluate the algorithm, we conduct simulations and show that it can extend the network lifetime.

• Journal of Computing Science and Engineering
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• v.9 no.4
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• pp.163-176
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• 2015

Self-organization of distributed wireless sensor nodes is a critical issue in wireless sensor networks (WSNs), since each sensor node has limited energy, bandwidth, and scalability. These issues prevent sensor nodes from actively collaborating with the other types of sensor nodes deployed in a typical heterogeneous and somewhat hostile environment. The automated self-organization of a WSN becomes more challenging as the number of sensor nodes increases in the network. In this paper, we propose a dynamic self-organized architecture that combines tree topology with a drawn-grid algorithm to automate the self-organization process for WSNs. In order to make our proposed architecture scalable, we assume that all participating active sensor nodes are unaware of their primary locations. In particular, this paper presents two algorithms called active-tree and drawn-grid. The proposed active-tree algorithm uses a tree topology to assign node IDs and define different roles to each participating sensor node. On the other hand, the drawn-grid algorithm divides the sensor nodes into cells with respect to the radio coverage area and the specific roles assigned by the active-tree algorithm. Thus, both proposed algorithms collaborate with each other to automate the self-organizing process for WSNs. The numerical and simulation results demonstrate that the proposed dynamic architecture performs much better than a static architecture in terms of the self-organization of wireless sensor nodes and energy consumption.

• Proceedings of the Korean Information Science Society Conference
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• 2008.06d
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• pp.313-317
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• 2008

유비쿼터스 환경에 대한 관심이 증폭됨에 따라, 센서는 다양한 어플리케이션들에서 점점 더 많이 사용되고 있다. 이러한 센서 시스템에서, 최소 개의 센서를 가지고 대상 공간이 복수 개의 센서에 의해 완전히 센싱되게 하기 위해서는, 센서를 어디에 배치하느냐가 중요한 문제이다. 또한 복수 개의 센서에 의해 센싱된 데이터로부터 의미 있는 정보를 추출하기 위해서는 센서 서로 간의 거리가 너무 가까워서는 안 된다. (최소거리 요건). 이를 위하여 우리는 TRE-based approach 라고 하는, 최소거리 요건을 만족하며 3-coverage 문제를 해결하는 방법을 제안하며, 이를 기반으로 3-coverage 문제를 3 차원으로 확장시킬 때 가능한 센싱 coverage 모델과 그 확장 가능성에 대해 논의한다.

• 한국정보통신설비학회:학술대회논문집
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• 2005.08a
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• pp.349-357
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• 2005

In this paper, a new clustering algorithm using the Guaranteed Minimum Coverage (GMC) is proposed. In the new protocol, an appropriate distribution of clusterheads is accomplished by guaranteeing a stochastic coverage at each clusterhead(CH)s. Using this protocol, the communication cost from clusterheads to their member nodes and the load variance in each clusterheads are reduced. Therefore, the network lifetime can be extended and the fair energy consumption for all CHs can be achieved

• Proceedings of the Korea Information Processing Society Conference
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• 2010.11a
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• pp.1718-1720
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• 2010

저 전력 무선 센서 네트워크와 마이크로 센서를 결합하여 환경이나 상황을 인지하고 모니터링을 통해 수집된 정보를 사람에게 전하는 WSN(Wireless Sensor Network) 기술에 대한 많은 연구가 진행되고 있다. 본 논문은 바이너리 모델을 사용하여 단순 탐지 확률을 표현하는 기존 시뮬레이터들의 Coverage 표현의 한계를 극복하기 위해 Heat-map을 이용한 시뮬레이터를 개발했다. 이 시스템은 기존 바이너리 모델을 확장하고, GIS를 사용하여 지형정보를 함께 가시화함으로써 서비스 지형에 대한 센서 네트워크 구성뿐만 아니라 수명예측 메커니즘을 이용한 에너지 소모에 따른 노드의 수명을 가시화 한다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2010.05a
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• pp.856-859
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• 2010

WSN is composed of a lot of small sensors with the limited hardware resources. In WSN, at the initial stage, sensor nodes are randomly deployed over the region of interest, and self-configure the clustered networks by grouping a bunch of sensor nodes and selecting a cluster header among them. Specially, in Mobile-WSN environment, in which the administrator's intervention is restricted, the self-configuration capability is essential to establish a power-conservative Mobile-WSN which provides broad sensing coverage and communication coverage. In this paper, we propose a self-configuration routing protocol for Mobile-WSN, which consists of step-wise novel protocols for initial deployment, effective joining and removal of sensor nodes, which result in reducing overall power consumption, and extending the lifetime of network.

• Proceedings of the Korean Information Science Society Conference
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• 2008.06a
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• pp.261-262
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• 2008

Due to technological advances, the manufacturing of small and low cost of sensors becomes technically and economically feasible. In recent years, an increasing interest in using Wireless Sensor Network (WSN) in various applications, including large scale environment monitoring, battle field surveillance, security management and location tracking. In these applications, hundreds of sensor nodes are left to be unattended to report monitored data to users. Since sensor nodes are placed randomly and sometimes are deployed in underwater. It is impossible to replace batteries often when batteries run out. Therefore, reducing energy consumption is the most important design consideration for sensor networks.