• Journal of Sensor Science and Technology
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• v.27 no.4
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• pp.254-258
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• 2018

A Wi-Fi signal network (WSN) system is introduced in this paper. This system consists of several data-transmitting sensor modules and a data-receiving server. Each sensor module and the server contain a unique intranet IP address. A piezoelectric accelerometer with a bandwidth of 12 kHz, a 24-bit analog-digital converter with a sampling rate of 15.625 kS/s, a 32-bit microprocessor unit, and a 1-Mbps Wi-Fi module are used in the data-transmitting sensor module. A 300-Mbps router and a PC are used in the server. The system is verified using an accelerometer calibrator. The voltage output from the sensor is converted into 24-bit digital data and transmitted via the Wi-Fi module. These data are received by a Wi-Fi router connected to a PC. The input frequencies of the accelerometer calibrator (320 Hz, 640 Hz, and 1280 Hz) are used in the data transfer verification. The received data are compared to the data retrieved directly from the analog-to-digital converter used in the sensor module. The comparison shows that the developed system represents the original data considerably well. Theoretically, the system can acquire vibration signals from 600 sensor modules at an accelerometer bandwidth of 15.625 kHz. However, delay exists owing to software processes, multiplexing between sensor modules, and the use of non-real time operating system. Hence, it is recommended that this system may be used to acquire vibration signals with up to 10 kHz, which is approximately 70% of the theoretical maximum speed of the system. The system can be upgraded using parts with higher performance

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.9 no.6
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• pp.151-158
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• 2010

In line with the requirement of appropriate protocol support for such mission-critical wireless sensor network (WSN) applications as patient monitoring, we investigate the framework for designing medium access control (MAC) schemes. The data traffic in medical systems comes with inherent traffic heterogeneity as well as strict requirement of reliability according to the varied extents of devise-wise criticality in separate cases. This implies that the quality-of-Service (QoS) issues are very distinctly delicate requiring specialized consideration. Besides, there are features in such systems that can be exploited during the design of a MAC scheme. In a monitoring or routine surveillance application, there are degrees of regularity or predictability in traffic as coordinated from a node of central control. The coordinator thus takes on the role of marshaling the resources in a neighborhood of nodes deployed mostly for upstream traffic; in a collision-free scheme, it schedules the time slots for each superframe based on the QoS specifications. In this preliminary study, we identify the key artifacts of such a MAC scheme. We also present basic performance issues like the impact of superframe length on delay incurred, energy efficiency achieved in the network operation as obtained in a typical simulation setup based on this framework.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.5
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• pp.203-210
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• 2011

The current sensor network analyzes the data collected by the sensing of fixed sensor nodes and provides a service. However, this method cannot actively handle the state and the change in the position of people, 'the target for sensing and the change in the environment', including home automation, building automation and real-time road & weather information, and healthcare environment, etc. To support a dynamic situation which is appropriate for an individual in this diverse environment, it is necessary to provide actively differentiated specific information according to the movement of people and the changes in the environment. In this study, a individualized sensor mobile agent middleware which provides the individualized information (the location of fire incidence and the trace for the path of spread), has been realized through the sensor network environment constructed by the installation of wireless sensor nodes mounted with mobile agent middlewares in buildings.

• The Journal of the Korea institute of electronic communication sciences
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• v.10 no.11
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• pp.1265-1270
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• 2015

For the sensor node or collection node operating with a battery in a wireless sensor network, MAC protocols with improved energy efficiency are important performance factors. In this paper, in order to improve the restrictive capability in accordance with the fixed activity period of the duty cycle technology in the MAC protocol for wireless sensor networks, we propose a periodic adaptive wakeup technique based on receive prediction. The proposed technique is through a performance evaluation using the CC2500 RF transceiver and C8051F330 microcontroller based wireless node, to analyze the minimum active period. As a result, it was confirmed that it is possible to improve energy efficiency by adaptively changing the sleep period in accordance with the change of period.

• Journal of Korea Multimedia Society
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• v.9 no.2
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• pp.172-188
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• 2006

Sensor localization is one of the fundamental problems in wireless sensor networks. Previous localization algorithms can be classified into two categories, the GGB (Global Geometry-Based) approaches and the LGB (Local Geometry-Based). In the GGB approaches, there are a fixed set of reference nodes of which the coordinates are pre-determined. Other nodes determine their positions based on the distances from the fixed reference nodes. In the LGB approaches, meanwhile, the reference node set is not fixed, but grows up dynamically. Most GGB algorithms assume that the nodes are deployed in a convex shape area. They fail if either nodes are in a concave shape area or there are obstacles that block the communications between nodes. Meanwhile, the LGB approach is vulnerable to the errors in the distance estimations. In this paper, we propose new localization algorithms to cope with those two limits. The key technique employed in our algorithms is to determine, in a fully distributed fashion, if a node is in the line-of-sight from another. Based on the technique, we present two localization algorithms, one for anchor-based, another for anchor-free localization, and compare them with the previous algorithms.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2012.10a
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• pp.394-397
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• 2012

Wireless sensor network is configured to be able to collect information collected from the various sensors, real-world environment wireless network. In this paper, the information collected from the wireless sensor networks in the real world using AR (Augmented Reality) data by projecting, in a variety of ways, the information collected from the wireless sensor network is utilized, which more intuitive is intended to provide to users. In this paper, stored in the DB table and the information collected from the wireless sensor network, wireless LAN (Access Point) that are placed in the sensor field and the terminal attached to the geomagnetic sensor, terminal position, after correction using acceleration sensors and augmented reality the aim is to visualize the data stored in the DB table using.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.3
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• pp.755-761
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• 2013

Medium access control (MAC) protocols for wireless sensor networks make sensor nodes on state for energy-efficiency only when necessary. In this paper we present an energy efficient priority-based MAC protocol for energy-harvesting Wireless Sensor Networks (WSNs). For support priority-based packet transmission the proposed EEPB-MAC protocol uses the modified IEEE 802.15.4 beacon frames including priority bit, sender node address, and NAV value fields. A receiver node periodically wakes up, receives sender beacon frames, selects data sending sender, and broadcasts a beacon frame containing the selected sender's address. A receiver node selects sender node according to sender's data priority. A receiver nodes also adjust wake up period based on their energy states. Hence, the energy consumption of receiver node can be minimized. Through simulations and analytical analysis, we evaluate the performance of our proposed the EEPB-MAC protocol and compare it against the previous MACs. Results have shown that our protocol outperforms other MAC in terms of energy consumption, higher priority packet delivery delay.

• Journal of KIISE:Information Networking
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• v.33 no.2
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• pp.131-138
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• 2006

To achieve security in wireless sensor networks(WSN), it is important to be able to encrypt and authenticate messages sent among sensor nodes. Due to resource constraints, many key agreement schemes used in general networks such as Diffie-Hellman and public-key based schemes are not suitable for wireless sensor networks. The current pre-distribution of secret keys uses q-composite random key and it randomly allocates keys. But there exists high probability not to be public-key among sensor nodes and it is not efficient to find public-key because of the problem for time and energy consumption. To remove problems in pre-distribution of secret keys, we propose a new cryptographic key management protocol, which is based on the clustering scheme but does not depend on probabilistic key. The protocol can increase efficiency to manage keys because, before distributing keys in bootstrap, using public-key shared among nodes can remove processes to send or to receive key among sensors. Also, to find outcompromised nodes safely on network, it selves safety problem by applying a function of lightweight attack-detection mechanism.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.9C
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• pp.573-580
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• 2011

WSNs (Wireless Sensor Networks) are becoming more widely used in various fields, and improving localization performance is a crucial and essential issue for sensor network applications. In this paper, we propose a low-complexity localization mechanism for WSNs that operates in 3D (Three-Dimensional) space. The basic idea is to use aerial vehicles or flying objects that are deliberately equipped with the anchor nodes. These anchor nodes periodically broadcast beacon signals containing their current locations, and the unknown nodes receive these signals as soon as they enter the communication range of the anchors. We estimate the locations of the unknown nodes based on the proposed scheme that transforms the 3D problem into 2D computations to reduce the complexity of 3D localization. Simulated results show that our approach is an effective scheme for 3D self-positioning in WSNs.

• The Journal of the Korea Contents Association
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• v.6 no.12
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• pp.40-49
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• 2006

As a promising integrated circuit, wireless communication and micro-computing technology, the technology of sensor network that will lead the information technology industries of the next generation and realize the ubiquitous computing is one of the most active research topics and its research activities are also making today. From now on, each node, the network formation, and even the sensor network itself will interact with the generic network and evolve dynamically according to environmental changes in a process of continual creation and extinction. Therefore, address-internetworking between sensor network and generic network which are used different address mechanism is required. In this paper, we propose a static address-internetworking scheme for interactive networking between a sensor network and the Internet. The proposed scheme that possess a gateway approach to perform the protocol translation from one protocol to another, an overlay approach to constructs an overlay network on the WSNs and enables static internetworking between a sensor network address scheme based on Zigbee and the Internet address scheme based on the Internet Protocol. In addition, we verify the proposed scheme by an interconnection experiment.