• The KIPS Transactions:PartC
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• v.14C no.2
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• pp.185-190
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• 2007

The efficient node energy utilization is one of important performance factors in wireless sensor networks because sensor nodes operate with limited battery power. To extend the lifetime of the wireless sensor networks, maintaining balanced power consumption between sensor nodes is more important than reducing each energy consumption of the sensor node in the network. In this paper, we proposed a cluster formation algorithm to extend the lifetime of the networks and to maintain a balanced energy consumption of nodes. To obtain it, we add a tiny slot in a round frame, which enables to exchange the residual energy messages between the base station (BS). cluster heads, and nodes. The performance of the proposed protocol has been examined and evaluated with the NS 2 simulator. As a result of simulation, we have confirmed that our proposed algorithm show the better performance in terms of lifetime than LEACH. Consequently, our proposed protocol can effectively extend the network lifetime without other critical overhead and performance degradation.

• The KIPS Transactions:PartC
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• v.15C no.4
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• pp.303-310
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• 2008

To increase the lifetime of ad-hoc networks, a ratio of energy consumption for each node should be kept constant by equally distributing network traffic loads into all of the nodes. In this paper, we propose a modified AODV routing protocol to determine a possible route by considering a remaining battery capacity of a node and the degree of its usage. In addition, to reduce the amount of energy consumption during the path rediscovery process due to the huge amount of the AODV control messages the limited number of possible routes are stored into a routing table of a source node. When some links of a route fail, another possible path can be looked up in the table before the route discovery process should be initiated. We have tested our proposed method with a conventional AODV and a MMBCR method which is one of the power-efficient energy routing protocols based on the three performance metrics, i.e., the total remaining battery capacity, network lifetime and the ratio of data packets received by the destination node to compare their performance.

• Proceedings of the Korea Information Processing Society Conference
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• 2010.04a
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• pp.623-626
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• 2010

최근 무선 네트워크 기술이 점차 각광을 받으면서 다양한 애드 혹 환경에서의 라우팅 프로토콜이 제안되고 있다. 하지만 애드 혹 네트워크라는 환경의 특성 상 보안상 취약한 문제점을 가지고 있으며, 기존의 유선 네트워크 환경에서 제안되었던 보안 라우팅 프로토콜을 적용시키기 힘들다는 문제점이 있다. 이에 따라 보안성을 보완한 새로운 애드 혹 라우팅 프로토콜이 제안되었지만 다양한 무선 네트워크 환경의 변화에 유동적으로 대응하기 힘들고 보안적인 측면에 집중을 한 나머지 에너지소모 측면에서는 단점을 노출하고 있다. 본 논문에서는 다양한 애드 혹 네트워크 환경에 적용 가능하고, 기존의 보안 라우팅 프로토콜에 비해 에너지 효율적인 보안 라우팅 프로토콜을 제안하고자 한다. 보안 정보의 보호를 위해 Tree 구조를 도입하고 보안 단계를 통한 Multi-path를 구성하여 악의적인 노드의 Dropping Attack에 대비하고, 예기치 못한 Data Packet의 손실에 대해서도 효율적으로 대처하게 하였다. 실험 결과 악의적인 노드가 존재하는 네트워크 환경에서 기존의 애드 혹 네트워크 보안 라우팅 프로토콜보다 21%정도의 패킷 전송 성공률을 높일 수 있었으며 또한 각 노드의 에너지를 균등하게 소모함으로써 전체적인 네트워크의 생존시간이 연장되는 것을 확인할 수 있었다.

• Proceedings of the Korea Information Processing Society Conference
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• 2006.05a
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• pp.1073-1076
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• 2006

유비쿼터스 센서 네트워크의 성능을 판단하는 중요한 지표로 감지된 정보를 실시간으로 전송하는 능력과 네트워크의 최대 생존시간을 들 수 있다. 하지만 대부분의 무선센서 에너지원은 배터리로 구성되어 있음으로 인해 실시간 정보전송을 위해 통신모듈의 전원을 자주 사용하게 되면 조기에 네트워크의 생존력을 잃게 되는 문제가 발생할 수 있으며 그와 반대로 에너지소모를 낮추기 위해 전송 주기를 길게 하면 전송지연이 발생되어 위급한 상황에서 시스템이 즉시 대응하지 못하는 문제가 발생할 수 있다. 본 논문에서는 통신모듈을 DUAL BAND로 이중화하고 송수신모드를 세분화하여 각 모듈에 공급되는 에너지를 상황에 맞게 제어하는 방법을 제안하며 제안한 방법을 적용하여 에너지 소모량과 전송지연시간을 계산한 결과, 중요한 군사적 목적이나 위험방지를 위한 실시간 감시 목적으로 사용할 경우 실시간전송과 효율적 에너지사용을 동시에 만족시킴을 확인할 수 있었다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.7
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• pp.1549-1555
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• 2009

The Relay node placement problem is one of the most important requirements for many wireless sensor networks because the lifetime of sensor networks is closely related with the placement of relay nodes which receive sensed data from sensor nodes and forward them to the base station. Relay node placement problem has focused at minimization of dissipated total energy of the sensor nodes in whole networks. However, minimum total energy causes the unbalance of consumed energy in sensor nodes due to different distances between relay nodes and sensor nodes. This paper proposes the concept of energy balance ratio and finds the locations of relay nodes using objective functions which maximize the energy balance ratio. Maximizing this ratio results in maximizing the network lifetime by minimizing the energy consumption of large-scale sensor networks. However, finding a solution to relay node placement problem is NP-hard and it is very difficult to get exact solutions. Therefore, we get approximate solutions to EBR-RNP problem which considers both energy balance ratio and relay node placement using constraint programming.

• KIISE Transactions on Computing Practices
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• v.23 no.2
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• pp.122-127
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• 2017

The data link layer operates reliable internode communication in the OSI reference model. Generally, the forward error correction (FEC) method is used in the data link layer of the wireless sensor network (WSN) environment that has a high frequency of errors. However, the FEC method consumes a significant amount of energy due to its high error correction rate, which negatively affects the networks' lifespan. In contrast with battery-based technology, energy is regularly recharged in the solar-powered WSN to meet higher energy needs than required for basic operation of existing nodes. By efficiently utilizing this surplus energy, the proposed energy-aware FEC method can reduce the data loss rate with no decrement of the network lifetime. The method employs a trade-off relationship between the energy and data loss rate by adjusting the parity length in the FEC method to the energy state in each node. The performance of the proposed scheme was verified through a simulation.

• Journal of KIISE:Computer Systems and Theory
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• v.37 no.1
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• pp.55-59
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• 2010

Most applications for solar-powered wireless sensor networks are usually deployed in remote areas without a continuous connection to the external networks and a regular maintenance by an administrator. In this case, sensory data has to be stored in the network as much as possible until it is uploaded by the data mule. For this purpose, a balanced data distribution over the network should be performed, and this can be achieved efficiently by taking the amount of available energy and storage into account, in the system layer of each node. In this paper, we introduce a simple but very efficient data distribution algorithm, by which each solar-powered node utilizes the harvested energy and the storage space maximally. This scheme running on each node determines the amount of energy which can be used for a data distribution as well as the amount of data which should be transferred to each neighbor, by using the local information of energy and storage status.

• Journal of Energy Engineering
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• v.26 no.3
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• pp.123-130
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• 2017

The district heating system has been successfully implemented with higher efficiency levels of energy production and reduction of carbon emissions during heat generation. Traditionally the system consisted of small number of production and demand sites, but, recently it has evolved into a network with large number of sites interconnected each other. By connecting multiple sites into a network, heat from low-cost production sites can be supplied to distant demand sites so as to lower the total operation cost. In this study, we simulate and analyze distict heating networks focused on critical links. a critical link is defined as a link in which capacity is fully utilized. If a newtork has critical links, then those cricial links become bottlenecks and it is difficult to improve the overall network efficiency.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.12
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• pp.4991-4996
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• 2010

Clustering method in wireless sensor network is the technique that forms the cluster to aggregate the data and transmit them at the same time that they can use the energy efficiently. Even though cluster group model is based on clustering, it differs from previous method that reducing the total energy consumption by separating energy overload to cluster group head and cluster head. In this thesis, I calculate the optimal cluster group number and cluster number in this kind of cluster group model according to threshold of energy consumption model. By using that I can minimize the total energy consumption in sensor network and maximize the network lifetime. I also show that proposed cluster group model is better than previous clustering method at the point of network energy efficiency.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.12
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• pp.6469-6477
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• 2013

As the Internet has grown, energy consumption and GHG emission from internet use have become issues in recent years. On the other hand, such interest in greening the Internet has focused on edge devices, and there is a lack of deeper related studies of the energy wasted by excessive network-connectivity and the savings potential in wired network equipment. This study presents the background and reasonability of studies on the energy efficiency of wired networks in terms of the environment, economy and energy resources. The energy consumption and savings potential of network equipment were also estimated and the major factors of energy consumption was analyzed based on the data, and future studies for the Internet are presented.