• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.8
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• pp.843-850
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• 2016

This paper introduces a novel modulation scheme for vehicular communication in taking advantage of existing LED lights available on a car. Our proposed 2-Phase Shift Keying (2-PSK) is a spatial modulation approach in which a pair of LED light sources in a car (either rear LEDs or front LEDs) is used as a transmitter. A typical camera (i.e. low frame rate at no greater than 30fps) that either a global shutter camera or a rolling shutter camera can be used as a receiver. The modulation scheme is a part of our Image Sensor Communication proposal submitted to IEEE 802.15.7r1 (TG7r1) recently. Also, a neural network approach is applied to improve the performance of LEDs detection and decoding under the noisy situation. Later, some analysis and experiment results are presented to indicate the performance of our system

• Journal of Digital Contents Society
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• v.9 no.2
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• pp.261-268
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• 2008

Recently, inn the ubiquitous home where a variety of home devices and sensors are inter-connected, various services can be provided through wired and wireless networks invisibly. The convenience of users can be maximized by using intelligent and adaptive interoperability technologies in the home. In this paper, it is designed u-apartment that connected parking system of intelligental form and medical service system based on USN environment with existing apartment. Intelligental form parking system is designed specific structure architecture for effective improvement of parking space and medical service system propose a design about health management of future. In this paper, we propose integrated u-apartment design with parking system and medical equipment using RFID system in ubiquitous environment.

• Proceedings of the IEEK Conference
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• 2003.07d
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• pp.1315-1318
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• 2003

Wastewater treatment processes are usually located in the outskirts of cities. But these processes should be dealt with continuous maintenance by expert operators. Therefore, in this paper, unmaned and automated control system is designed for the SBR(Sequencing Batch Reactor) plant. This plant is constructed in Gimhae city. Networks and wireless modules are employed for the data transmission. A local controller is in the SBR plant as a client and a monitoring system is located in the other place as a server. Remote control and monitoring system are constructed at the laboratory of ours. Measured data from plant sensors are translated to the remote site using communication modules, and then the data could be displayed and analyzed by means of remote monitoring and control systems.

• Journal of Sensor Science and Technology
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• v.27 no.3
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• pp.175-181
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• 2018

In this paper, we introduce a new dimming control method in a visible light communication (VLC) system wherein byteinversion is adopted for flicker-free transmission. In the VLC transmitter, the original and the inverted data were sent sequentially and the remnant time in one period was used for the dimming control of the LED light. In the VLC receiver, only the original data was recovered using the gating signal whose width was the same as the length of the original data. In our experiments, the dimming control ranges were measured to be 22%-53%, 11%-76%, and 5%-88% of the CW LED light when the data rates were 9.6, 19.2, and 38.4 kbps, respectively. In this system, we used a 240-Hz sync pulse whose period was 4.16 ms, which was shorter than the maximum flickering time period of 5 ms that is generally considered to be safe. This configuration is very simple and useful in constructing indoor wireless sensor networks using the flicker-free LED lamps with dimming control capability.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.5
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• pp.416-421
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• 2011

Nowadays, the increasing demands upon mobile devices such as wireless sensor networks and the recent advent of low power electrical devices such as MEMS make such renewable power sources attractive. A vibration-driven MEMS lead zirconate titanate $Pb(Zr,Ti)O_3$ (PZT) cantilever device is developed for energy harvesting application. This paper presents a piezoelectric based energy harvester which is suitable for power generating from conventional vibration and has in providing energy for low power electron ic devices. The PZT cantilever is used d33 mode to get the electrical power. The PZT cantilever based energy harvester with the dimension of 7 mm${\times}$3 mm${\times}$0.03 mm is fabricated using micromachining technologies. This PZT cantilever has the mechanical resonance frequency with a 900 Hz. With these conditions, we get experimentally the 37 uW output power from this device with the application of 1g acceleration using the 900 Hz vibration. From this study, we show the feasibility of one of energy harvesting candidates using PZT based structure. This PZT energy harvester could be used for various applications such a batteryless micro sensors and micro power generators.

• Proceedings of the Korean Information Science Society Conference
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• 2011.06a
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• pp.416-419
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• 2011

무선 센서 네트워크 환경에서 효율적인 데이터 수집 기업은 핵심적인 기반 기술이다. 클러스터 기반의 데이터 수집 기법은 데이터 병합 (aggregation) 의 효율을 최대화 시켜 센서 노드들의 에너지 소모를 최소화 시킨다. 하지만 기존의 클러스터링 기법은 균일한 네트워크 환경만을 고려하여 불균일하게 배포될 수 있는 실제 환경에는 적합하지 않다. 본 논문에서는 기존 기업들의 문제점을 해결하기 위해 불균일한 네트워크 환경에서도 에너지 효율적인 클러스터를 구축할 수 있는 기업을 제안한다. 제안하는 기법은 클러스터 헤드를 기준으로 최단 거리 홉 카운트 기법을 통해 논리적인 거리를 기반으로 클러스터 멤버를 구성한다. 이를 통해 불균일한 네트워크 환경에서도 클러스터들 간에 균형적인 멀티-홉 클러스터를 구축하여 네트워크 수명을 최대화 시킨다. 제안하는 기법의 우수성을 모이기 위해 기존 기법과 시뮬레이션을 통해 성능을 비교평가 하였다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2007.06a
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• pp.340-343
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• 2007

To effectively manage a electric lamp on a remote place, it is required to identify a status of the lamp or the place. however, since there is no methods to notify the status of sensor to the central management system in a lamp system based on the non-networked sensor, it is difficult to manage the lamps remotely. In this paper, we propose the lamp management system to acquire the various status informations of lamps using more than two sensors. To get the status remotely, the system exploits a wireless network based on the ZigBee. The benefit of this system is to help the efficient decision makings of administrators.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.2
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• pp.188-194
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• 2014

Recently, indoor localization systems based on wireless sensor networks have received a great deal of attention because they help achieve high accuracy in position determination by using various algorithms. In order to minimize the error in the estimated azimuth that can occur owing to sensor drift and recursive calculation in these algorithms, we propose a novel relative azimuth estimation algorithm. The advantages of the proposed technique in an indoor environment are that an improved weight average filter is used to effectively reduce impulse noise from the raw data acquired from nodes with inherent errors and a rotational displacement algorithm is applied to obtain a precise relative azimuth without using additional sensors, which can be affected by electromagnetic noise. Results from simulations show that the proposed filter reduces the impulse noise, and the acquired estimation error does not accumulate with time by using proposed algorithm.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.3
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• pp.1052-1070
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• 2016

Wireless Body Area Networks (WBANs) have received a lot of attention as a promising technology for medical and healthcare applications. A WBAN should guarantee energy efficiency, data reliability, and low data latency because it uses tiny sensors that have limited energy and deals with medical data that needs to be timely and correctly transferred. To satisfy this requirement, many multi-radio multi-channel MAC protocols have been proposed, but these cannot be implemented on current off-the-shelf sensor nodes because they do not support multi-radio transceivers. Thus, recently single-radio multi-channel MAC protocols have been proposed; however, these methods are energy inefficient due to data duplication. This paper proposes a TDMA-based single-radio, multi-channel MAC protocol that uses the Unbalanced Star+Mesh topology to satisfy the requirements of WBANs. Our analytical analysis together experiments using real sensor nodes show that the proposed protocol outperforms existing methods in terms of energy efficiency, reliability, and low data latency.

• Journal of Sensor Science and Technology
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• v.20 no.6
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• pp.420-427
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• 2011

The population of elderly people increases rapidly as our society moves towards the aged one. Healthcare for the elderly becomes an important issue and falling down is one of the critical problems although not well recognized. In this study, a fall detection system was developed using a 3-axis accelerometer. Analyzing fall patterns, we took into account the degree of impact, posture angle, the repetitions of similar movements and the activities after a potential fall and proposed an algorithm of fall detection. Information of the fall sensor was sent to a remote healthcare server through the wireless networks of Zigbee and WLAN. Our system was designed to monitor multiples users. 12 persons participated in experiment and each one performed 24 different movements. Our proposed algorithm was compared with other reported ones. Our method produced the excellent results having a sensitivity of 96.4 % and a specificity of 100 % whereas other methods had a sensitivity range between 87.5 % and 94.8 % and a specificity range between 63.5 % and 83.3 %.