• Journal of IKEEE
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• v.11 no.4
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• pp.322-330
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• 2007

Recent advances in wireless networks and low-cost, low-power design have led to active research in large-scale networks of small, wireless, low power sensors and actuators, In large-scale networks, lots of timing-synchronization protocols already exist (such as NTP, GPS), In ad-hoc networks, especially wireless sensor networks, it is hard to synchronize all nodes in networks because it has no infrastructure. In addition, sensor nodes have low-power CPU (it cannot perform the complex computation), low batteries, and even they have to have active and inactive section by periods. Therefore, new approach to time synchronization is needed for wireless sensor networks, In this paper, I propose Energy-Efficient Time Synchronization (EETS) protocol providing network-wide time synchronization in wireless sensor networks, The algorithm is organized two phase, In first phase, I make a hierarchical tree with sensor nodes by broadcasting "Level Discovery" packet. In second phase, I synchronize them by exchanging time stamp packets, And I also consider send time, access time and propagation time. I have shown the performance of EETS comparing Timing-sync Protocol for Sensor Networks (TPSN) and Reference Broadcast Synchronization (RBS) about energy efficiency and time synchronization accuracy using NESLsim.

• Smart Structures and Systems
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• v.6 no.3
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• pp.263-275
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• 2010

In the last decade, wireless sensor networks have emerged as a promising technology that could accelerate progress in the field of structural monitoring. The main advantages of wireless sensor networks compared to conventional monitoring technologies are fast deployment, small interference with the surroundings, self-organization, flexibility and scalability. These features could enable mass application of monitoring systems, even on smaller structures. However, since wireless sensor network nodes are battery powered and data communication is the most energy consuming task, transferring all the acquired raw data through the network would dramatically limit system lifetime. Hence, data reduction has to be achieved at the node level in order to meet the system lifetime requirements of real life applications. The objective of this paper is to discuss some general aspects of data processing and management in monitoring systems based on wireless sensor networks, to present a prototype monitoring system for civil engineering structures, and to illustrate long-term field test results.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.8
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• pp.1511-1518
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• 2008

Wireless sensor network is a network that consists of small wireless sensor nodes. Sensor nodes transfer the sensed data about the objects or environment to the sink through wireless channel. The energy dissipation by wireless transmission is the primary factor of energy dissipation in the sensor node. To utilize the limitted resource at the sensor node, it is required to reduce the number of wireless transmission. In the paper, we proposes a new energy efficient method, NRMC, to reduce the energy dissipation by using the compression technique - DPCM, Wavlet, Quantization, RLC. With NTRC, the life time of sensor network could be increased.

• Journal of Sensor Science and Technology
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• v.17 no.3
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• pp.168-177
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• 2008

An indoor environmental monitoring system using IEEE 802.15.4 based wireless sensor network is proposed to monitor the amount of pollutant entering to the room from outside and also the amount of pollutant that is generated in indoor by the building materials itself or human activities. Small-size, low-power wireless sensor node and low power electrochemical sensor board is designed to measure the condition of indoor environment in buildings such as home, offices, commercial premises and schools. In this paper, two query models, the broadcasting query protocol and flooding query protocol, were designed and programmed as a query-based routing protocol in wireless sensor network for an environment monitoring system. The flooding query routing protocol in environment monitoring is very effective as a power saving routing protocol and reliable data transmission between sensor nodes.

• Journal of The Institute of Information and Telecommunication Facilities Engineering
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• v.5 no.1
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• pp.13-24
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• 2006

This paper proposes a wireless management system for a pet dog using wireless sensor network. The developed intelligent wireless management system is compose of a central control system, auto-feeder, miniguidance robot, and wireless sensing devices. The developed system uses three types of sensed data such as light, temperature, md sounds from a pet dog and surrounded environment respectively. The presented design method using these data provides an efficient way to controlling and monitoring the pet dog. The implemented system can be used as a design framework of portable device for the pet management.

• Structural Engineering and Mechanics
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• v.49 no.4
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• pp.509-521
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• 2014

In this paper two protocols of Wireless Sensor Networks (WSN) are examined through both a simulation and a case study. The simulation was performed with the optimized network (OPNET) simulator while comparing the performance of the Ad-Hoc on demand Distance Vector (AODV) and the Dynamic Source Routing (DSR) protocols. This is compared and shown with real-world measurement of deflection from eight wireless sensor nodes. The wireless sensor response results were compared with accelerometer sensors for validation purposes. It was found that although the computer simulation suggests the AODV protocol is more accurate, in the case study no distinct difference was found. However, it was shown that AODV is still more beneficial in the field as it has a longer battery life enabling longer surveying times. This is a significant finding as a large factor in determining the use of wireless network sensors as a method of assessing structural response has been their short battery life. Thus if protocols which enhance battery life, such as the AODV protocol, are employed it may be possible in the future to couple wireless networks with solar power extending their monitoring periods.

• Journal of The Institute of Information and Telecommunication Facilities Engineering
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• v.7 no.1
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• pp.1-13
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• 2007

This paper proposes a wireless management system for a pet dog using wireless sensor network. The developed intelligent wireless management system is compose of a central control system, auto-feeder, mini-guidance robot, and wireless sensing devices. The developed system uses three types of sensed data such as light, temperature, and sounds from a pet dog and surrounded environment respectively. The presented design method using these data provides an efficient way to controlling and monitoring the pet dog. The implemented system can be used as a design framework of portable device for the pet management.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.1
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• pp.122-127
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• 2016

In this paper, new spectrum sensing schemes based on analog/RF front-end processing are introduced for IoT wireless sensor networks. While the conventional approaches for wireless channel cognition have been issued in signal processing area, the RF spectrum cognition concept makes it feasible to achieve cognitive wireless sensor networks (C-WSNs). The spectrum cognition at RF processing is categorized as four kinds of sensing mechanisms. Two recent reseaches are described as promising candidates for the C-WSN. One senses spectrum by the frequency discriminating receiver, the other senses and detects from the frequency selective super-regenerative receiver. The introduced systems with simple and low-power RF architectures play dual roles of channel sensing and demodulation. simultaneously. Therefore, introduced spectrum sensing receivers can be one of the best candidates for IoT wireless sensor devices in C-WSN environments.

• Journal of Institute of Control, Robotics and Systems
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• v.18 no.8
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• pp.780-786
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• 2012

Surveillance has become one of promising application areas of wireless sensor networks which allow for pervasive monitoring of concerned environmental phenomena by facilitating context awareness through sensor fusion. Existing systems that depend on a postmortem context analysis of sensor data on a centralized server expose several shortcomings, including a single point of failure, wasteful energy consumption due to unnecessary data transfer as well as deficiency of scalability. As an opposite direction, this paper proposes an energy-efficient distributed context-aware surveillance in which sensor nodes in the wireless sensor network collaborate with neighbors in a distributed manner to analyze and aware surrounding context. We design and implement multi-modal sensor stations for use as sensor nodes in our wireless sensor network implementing our distributed context awareness. This paper presents an initial experimental performance result of our proposed system. Results show that multi-modal sensor performance of our sensor station, a key enabling factor for distributed context awareness, is comparable to each independent sensor setting. They also show that its initial performance of context-awareness is satisfactory for a set of introductory surveillance scenarios in the current interim stage of our ongoing research.

• Structural Monitoring and Maintenance
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• v.1 no.1
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• pp.47-67
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• 2014

This study has been motivated to examine the performance of a wireless sensor system under the typhoons as well as to analyze the effect of the typhoons on the bridge's vibration responses and the variation of cable forces. During the long-term field experiment on a real cable-stayed bridge in years 2011-2012, the bridge had experienced two consecutive typhoons, Bolaven and Tembin, and the wireless sensor system had recorded data of wind speeds and vibration responses from a few survived sensor nodes. In this paper, the wireless structural health monitoring of stay cables under the two consecutive typhoons is presented. Firstly, the wireless monitoring system for cable-stayed bridge is described. Multi-scale vibration sensor nodes are utilized to measure both acceleration and PZT dynamic strain from stay cables. Also, cable forces are estimated by a tension force monitoring software based on vibration properties. Secondly, the cable-stayed bridge with the wireless monitoring system is described and its wireless monitoring capacities for deck and cables are evaluated. Finally, the structural health monitoring of stay cables under the attack of the two typhoons is described. Wind-induced deck vibration, cable vibration and cable force variation are examined based on the field measurements in the cable-stayed bridge under the two consecutive typhoons.