• Journal of Information Processing Systems
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• v.2 no.1
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• pp.44-47
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• 2006

One of the critical issues in a sensor network concerns the detection of changes in data streams. Recently presented change detection schemes primarily use a sliding window model to detect changes. In such a model, a distance function is used to compare two sliding windows. Therefore, the performance of the change detection scheme is greatly influenced by the distance function. With regard to sensor nodes, however, energy consumption constitutes a critical design concern because the change detection scheme is implemented in a sensor node, which is a small battery-powered device. In this paper, we present a comparative study of various distance functions in terms of execution time, energy consumption, and detecting accuracy through simulation of speech signal data. The simulation result demonstrates that the Euclidean distance function has the highest performance while consuming a low amount of power. We believe our work is the first attempt to undertake a comparative study of distance functions in terms of execution time, energy consumption, and accuracy detection.

• Journal of Communications and Networks
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• v.5 no.4
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• pp.386-393
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• 2003

Future wireless networks are expected to achieve high bit rates at low cost, enabling multimedia and QoS-based services over the wireless medium. The impulse radio ultra-wide band (IR-UWB) technique is a promising candidate in the deployment of such networks, thanks to its potential robustness and capacity. In the past, most of the UWB research focused on hardware and physical layer aspects in order to solve the technological challenges posed by IR-UWB. UWB peculiar characteristics may, however, also stimulate innovative higher layers’ design. This work addresses MAC issues for UWB communication systems. Key areas such as medium sharing, MAC organization, packet scheduling and power control are reviewed. The impact of UWB on the above functions is discussed, and areas which require UWB specific design are identified. Finally, novel MAC functions enabled by UWB specific features, i.e., precise ranging and positioning, are presented.

• ETRI Journal
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• v.27 no.3
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• pp.250-256
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• 2005

A novel planar polarization-agile microstrip subarray is proposed and its performance assessed by a thorough numerical investigation. The subarray consists of five square patches with a central element, directly coupled to a pair of microstrip feed lines by a cross-shaped aperture, which spreads the power outwards to the other patches through a network of suitable connections. By properly exciting the antenna at its input ports, any kind of polarization of the radiated field can be accomplished with fairly low cross-polarization levels. Moreover, since only two feed lines are required to drive the whole subarray, polarization agility is simply and attractively achieved by a single phase-shift circuit. The design concept is described and the results of the analyses and simulations performed by two completely independent full-wave approaches are presented and discussed.

• ETRI Journal
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• v.42 no.4
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• pp.585-595
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• 2020

Integration of multiple communication technologies in a smart grid (SG) enables employing cognitive radio (CR) technology for improving reliability and security with low latency by adaptively and effectively allocating spectral resources. The versatile features of the CR enable the smart meter to select either the unlicensed or the licensed band for transmitting data to the utility company, thus reducing communication outage. Demand response management is regarded as the control unit of the SG that balances the load by regulating the real-time price that benefits both the utility company and consumers. In this study, joint allocation of the transmission power to the smart meter and consumer's demand is formulated as a two stage multi-armed bandit game in which the players select their optimal strategies noncooperatively without having any prior information about the media. Furthermore, based on historical rewards of the player, a real-time pricing adaptation method is proposed. The latter is validated through numerical results.

• Convergence Security Journal
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• v.10 no.2
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• pp.11-17
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• 2010

Recent technological advances allow us to envision a future where large numbers of low-power, inexpensive sensor devices are densely embedded in the physical environment, operating together in a wireless network. This paper considers localization for mobile sensors; localization must be invoked periodically to enable the sensors to track their location. Localizing more frequently allows the sensors to more accurately track their location in the presence of mobility. In this paper, we test and analyze the accuracy of a moving node localization by Received Signal Strength (RSS).

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.1
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• pp.197-203
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• 2010

The problem of location awareness in wireless sensor networks where nodes use GPS (Global Positioning System), remains challenging problem, when considering the required large energy consumption during the localization phase. In this paper we designed hardware for GPS based localization and propose a framework, called ELS, to consume low cost energy. In the ELS framework, sensor nodes are equipped with GPS. Because GPS spends large energy for position awareness, conventional localization algorithms cannot use GPS-device. We try to find a solution for efficient energy expenditure of GPS. Finally, we derive optimal transmission power of GPS data and a scheme of localization through experiment and simulation.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.60 no.4
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• pp.167-171
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• 2011

In this paper, $2{\times}4$ microstrip patch antenna are proposed to implement K-band satellite communications. The microstrip feed line are inset into the radiation patch to match input impedance. Also the same current in each elements are excited by Kirchhoff's low. The elements distance of proposed array antenna are optimized $0.8{\lambda}_g$ to minimize a mutual coupling and maximize a gain. A power divider network are employed to distribute T-junction divider. As result, the proposed antenna get gain of 14[dBi] at 10.525[GHz].

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1579_1580
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• 2009

다양한 환경에서 WBAN/USN 시스템이 적용됨에 따라 해당 시스템의 효율적인 전력 운용 및 통신 방식이 중요해 지고 있다. 이에 본 논문은 센서 간 효율적인 운용 방식으로 ID 기반의 통신 시스템을 제안 하였다. 보다 효율적인 시스템 동작을 위해 센서 노드에 웨이크업 모듈과 자가 전원 차단 회로를 구현함으로써 센서 노드의 보다 효율적인 전력 사용이 가능하도록 하였다. 웨이크업 모듈 구현을 통해 싱크노드가 원하는 센서 노드만 동작 가능하도록 하였으며, 일반적인 센서노드와는 달리 센서 데이터 전송 후 시스템 전력을 차단하는 회로를 구현함으로써 시스템의 불용 전력을 최소화 하였다. 또한 제안한 시스템을 직접 제작하고 실제 ID 기반으로 통신이 가능한지 검증함으로써 다양한 WBAN/USN 시스템에 적용 가능함을 보였다.

• International Journal of Contents
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• v.4 no.2
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• pp.1-6
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• 2008

Pre schools with state of the art facilities that would provide not just academic excellence but also ensure the safety and provide efficient healthcare to their pupils relative to Atopic Dermatitis with Asthma is the main objective of this research One of the most promising applications of sensor networks is for human healthcare monitoring. Due to recent technological advances in sensor, low power microelectronics and miniaturization, and wireless networking enable the design and proliferation of this wireless sensor networks capable of autonomously monitoring and controlling environments. Thus, this research presents the utilization of such microelectronic sensor and plots the hardware and software architecture of a wireless sensor network system with real-time pupil monitoring that integrates vital sign sensors, location sensor and allergen sensor. This proposed architecture for wearable sensors can be used as active tags which can track pupil's location within the school's premises, identify possible atopic dermatitis with asthma allergens, it would monitor and generate a health status report of the pupil.

• Journal of information and communication convergence engineering
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• v.6 no.2
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• pp.158-163
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• 2008

The MB-OFDM based UWB communication system is a personal area network specification aiming to provide 480Mbps peak data rate over 528 MHz spectrum. As the corresponding baseband modem operates at high clock rate, its complexity should be optimized for low power consumption. A set of modem design parameters is suggested including the AD bit width, the clipping level and the quantization level at the Viterbi decoder input as well as the trace-back depth of the Viterbi decoder. The data throughput is used to evaluate the performance of the receiver and a recommended set of design parameter values is presented to aid efficient modem implementation.