• KSII Transactions on Internet and Information Systems (TIIS)
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• v.5 no.4
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• pp.684-702
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• 2011

This paper proposes a TDMA-based multichannel medium access control (MAC) protocol for QoS provisioning in mobile ad hoc networks (MANETs) that enables nodes to transmit their packets in distributed channels. The IEEE 802.11 standard supports multichannel operation at the physical (PHY) layer but its MAC protocol is designed only for a single channel. The single channel MAC protocol does not work well in multichannel environment because of the multichannel hidden terminal problem. Our proposed protocol enables nodes to utilize multiple channels by switching channels dynamically, thus increasing network throughput. Although each node of this protocol is equipped with only a single transceiver but it solves the multichannel hidden terminal problem using temporal synchronization. The proposed energy efficient multichannel MAC (EM-MAC) protocol takes the advantage of both multiple channels and TDMA, and achieves aggressive power savings by allowing nodes that are not involved in communications to go into power saving "sleep mode". We consider the problem of providing QoS guarantee to nodes as well as to maintain the most efficient use of scarce bandwidth resources. Our scheme improves network throughput and lifetime significantly, especially when the network is highly congested. The simulation results show that our proposed scheme successfully exploits multiple channels and significantly improves network performance by providing QoS guarantee in MANETs.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.4 no.1
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• pp.5-24
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• 2010

Data fusion is an attractive technology because it allows various trade-offs related to performance metrics, e.g., energy, latency, accuracy, fault-tolerance and security in wireless sensor networks (WSNs). Under a complicated environment, each sensor node must be equipped with more than one type of sensor module to monitor multi-targets, so that the complexity for the fusion process is increased due to the existence of various physical attributes. In this paper, we first investigate the process and performance of multi-attribute fusion in data gathering of WSNs, and then propose a self-adaptive threshold method to balance the different change rates of each attributive data. Furthermore, we present a method to measure the energy-conservation efficiency of multi-attribute fusion. Based on our proposed methods, we design a novel energy equilibrium routing method for WSNs, viz., multi-attribute fusion tree (MAFT). Simulation results demonstrate that MAFT achieves very good performance in terms of the network lifetime.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.14 no.4
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• pp.1419-1436
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• 2020

For an energy harvesting sensor network, when the network lifetime is not the only primary goal, maximizing the network performance under environmental energy harvesting becomes a more critical issue. However, clustering protocols that aim at providing maximum information throughput have not been thoroughly explored in Energy Harvesting Wireless Sensor Networks (EH-WSNs). In this paper, clustering protocols are studied for maximizing the data transmission in the whole network. Based on a long short-term memory (LSTM) energy predictor and node energy consumption and supplement models, an uneven clustering protocol is proposed where the cluster head selection and cluster size control are thoroughly designed for this purpose. Simulations and results verify that the proposed scheme can outperform some classic schemes by having more data packets received by the cluster heads (CHs) and the base station (BS) under these energy constraints. The outcomes of this paper also provide some insights for choosing clustering routing protocols in EH-WSNs, by exploiting the factors such as uneven clustering size, number of clusters, multiple CHs, multihop routing strategy, and energy supplementing period.

• The KIPS Transactions:PartC
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• v.17C no.5
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• pp.427-432
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• 2010

It is important to efficiently elect the cluster header in Hierarchical Sensor Network, because it largely effects on the life duration of the network. Therefore, a recent research is going forward a research activity with regard to life time extension of the whole network for efficient cluster header election. In this paper, we propose the new Cluster Header Election Scheme in which the cluster is divided into Group considering Distance from a Sink, and a cluster header will be elected by node density of the Group. Also, we evaluate the performance of this scheme, and show that this proposed scheme improves network lifetime in Zigbee environment.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.6 no.4
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• pp.208-215
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• 2013

In recent years, many applications in WSN have increasingly interested in data transfer reliability. In this paper, we propose a dynamic grouping transfer mechanism which maintains both reliability and energy efficiency in transmission from a source to a sink. The proposed scheme considers channel error of each node. Then it uses an end-to-end ACK transmission in a group and a hop-by-hop ACK transmission between groups. Consequently this mechanism minimize the cost of packet transfer along with enhancing the network lifetime and reliability.

• Journal of the Korean Society for Precision Engineering
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• v.25 no.2
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• pp.115-122
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• 2008

Mostly used sensors have wired powering and two-way cable systems. It is difficult to employ wired sensor network in ubiquitous era because of a number of sensors and cables. Therefore, sensor networks move from wired systems to wireless systems for the future. However, the power source is a critical obstacle for wireless sensornodes. This research represents the new power source which supplies energy sensor node, maintains over 10 years, and thus replaces batteries with limit of lifetime. The system with piezo materials scavenges extra energies such as vibration and acceleration from the environment. Then it converts the scavenged mechanical energy to electrical energy for powering a sensor, a controller and a circuit for regulating voltage and transmitting sensor value. This study explains the properties of piezo material through theoretical analysis and experiments, and demonstrates powering sensor and transmitting data with stored energy (35mJ) for 14 sec. The developed system provides a solution to overcome the critical problem of making up wireless sensor networks.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2018.05a
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• pp.574-575
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• 2018

The generation of redundant data according to the spatial-temporal correlation in a wireless sensor network that reduces the network lifetime by consuming unnecessary energy. In this paper, data collection experiment through the particulate matter sensor is carried out to confirm the spatial-temporal data redundancy and we propose permitted limit setting method for data transmission to solve this problem. In the proposed method, the data transmission permitted limit is set by using the integrated average value in the cluster. The set permitted limit reduces the redundant data of the member node and it is shows that redundant data reduction is possible even in a variable environment of collected data by resetting the permitted limit in the cluster head.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.12B
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• pp.1426-1434
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• 2009

RFID/USN is considered as a key convergence technology in future ubiquitous network. In RFID/USN, the power saving issue receives a great attention due to limited battery lifetime of sensor node. In this paper, we propose a new power saving algorithm, which takes advantage of long-term sleep period. To provide a full network connectivity and balance the battery consumption among sensor nodes, the proposed algorithm intelligently selects the long-term sleep sensor nodes. With mathematical analysis and simulations, we prove that the proposed algorithm can significantly reduce the power consumption of sensor nodes as compared to existing algorithms.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.8 s.350
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• pp.77-83
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• 2006

In this paper, we have pesented a reliable data transfer mechanism using Directed Diffusion in WSNs (fireless Sensor Networks). This mechanism involves selecting a route with higher reachability and transferring data along the route chosen, which is based on the end-to-end reliability calculated by the dissemination procedure of Interest packets, while each node of a sensor network maintains the only information on its neighborhood. We performed various experiments changing the link error rates and the number of nodes and discovered that this proposed mechanism improves event-to-sink data transfer reliability in WSNs. We also found that this mechanism spreads traffic load over and reduces energy consumption, which in turn prolongs network lifetime.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.11
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• pp.1625-1633
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• 2012

In the lighting industry, a Lighting Emitting Diode (LED) is increasingly used because of many advantages and a eco-friendly product comparing with the conventional lighting. However, the LED lighting has to include various AC/DC converters because the direct current is used for the LED lighting. Among a lot of power converters, the flyback converter is widely used for the LED lighting and includes some electrolytic capacitors for the voltage regulation. But the electrolytic capacitor has shorter lifetime than the LED element. It makes the expected life-time of the converter having the electrolytic capacitor shorter than the LED element. This paper proposes the single-stage PFC flyback converter without electrolytic capacitors. To verify the performance of the proposed converter, simulated and experimental works were carried out.