• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2011.10a
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• pp.255-258
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• 2011

Wi-Fi is a rapidly spreading communications network with Smart phone's publication, the technology has become Ubiquitous-based core network which is connected to personal computers, laptops, and tablet PC. Wi-Fi can send currently a variety of data standard due to developed wireless LAN communications network. One of Wi-Fi standard protocols, which is IEEE 802.11n, use 2.4GHz and 5GHz band. 2.4GHz band is used for 802.11b/g protocol because wavelength is long, diffraction and receiving distance is enough to connect other device. 5GHz band has more available channels to use than 2.4GHz band, so there is no frequency interference of other wireless device such as Bluetooth, RFID. Moreover, there is low interference between channels due to small users in each bandwidth level. In the thesis, we are going to analyze 802.11a/b/g protocol which has used since the beginning of Wi-Fi protocol and 802.11n protocol which is used lately. Furthermore, we look into development and direction for standardization of the next generation wireless LANs which are 802.11ac and 802.11ad. In addition, we will consider for the security, vulnerabilities and its countermeasure in Wireless LAN.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.47 no.6
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• pp.93-102
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• 2010

Existing web based information service system solutions show limitations in mobile information services, as well as problems such as uncertain error messages, and difficulty providing swift assistance or real time emergency support. In order to solve these deficiencies, a realtime wireless remote control system has been designed and implemented in this thesis, which is capable of managing and monitoring remote systems using mobile communication devices (Mobile Phone, PDA, Smart Phone) for realtime control. Proposed systems are applied at remote places, for instance 'office building', and a nursery school like 'kindergarten'. In the case of implemented at office building, it can be managing and controlling at real time all sorts of the sensor information that are installed at office building system environment through wire(web environment) or wireless(mobile device). In the other case at kindergarten system that are providing the real-time wireless remote control and monitoring system can be monitoring activity of kindergarten children with a mobile phone of authentication user. The security functions of proposed systems include mobile device user authentication and target system access control. The proposed systems allow real-time user authentication function and system access control function that improve the security of resource administrators and mobile device users, and provides not only uninterrupted services, but also real time mobile service environments.

• Journal of Sensor Science and Technology
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• v.27 no.2
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• pp.86-92
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• 2018

In recent times, motion capture technology using inertial measurement unit (IMU) sensors has been actively used in sports. In this study, we developed a canoe paddle, installed with an IMU and a water level sensor, as a system tool for training and calibration purposes in water sports. The hardware was fabricated to control an attitude heading reference system (AHRS) module, a water level sensor, a communication module, and a wireless charging circuit. We also developed an application program for the mobile device that processes paddling motion data from the paddling operation and also visualizes it. An AHRS module with acceleration, gyro, and geomagnetic sensors each having three axes, and a resistive water level sensor that senses the immersion depth in the water of the paddle represented the paddle motion. The motion data transmitted from the paddle device is internally decoded and classified by the application program in the mobile device to perform visualization and to operate functions of the mobile training/correction system. To conclude, we tried to provide mobile knowledge service through paddle sport data using this technique. The developed system works reasonably well to be used as a basic training and posture correction tool for paddle sports; the transmission delay time of the sensor system is measured within 90 ms, and it shows that there is no complication in its practical usage.

• The Journal of Korean Institute for Practical Engineering Education
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• v.5 no.1
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• pp.34-39
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• 2013

This paper suggests an input device that allows a user not only to naturally interact with education contents in virtual environment but also to sense haptic feedback according to his/her interaction. The proposed system measures a user's motion and then creates haptic feedback based on the measured position. To create haptic information in response to a user's interaction with educational contents in virtual environment, we develop a motion input device which consists of a motion controller, a haptic actuator, a wireless communication module, and a motion sensor. To measure a user's motion input, an accelerometer is used as the motion sensor. The experiment shows that the proposed system creates continuous haptic sensation without any jerky motion or vibration.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.12 no.2
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• pp.38-44
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• 2013

In this paper, we designed and implemented a mobile video transmission device with 1080i resolution and 30fps frame rate using wireless multi-access technologies. The video acquisition delay time of 16us and jitter of 21ms for this equipment were obtained, respectively. The device is designed to access various communication networks. In order to evaluate the performance of its video transmission capability, a server and monitoring viewer are implemented. In the performance test using LTE network, 211ms delay time was obtained at 3Mbps transmission. Rendering of 1fps frame rate at the 265kbps transmission was confirmed for the transmission test using Inmarsat network.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.12
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• pp.2277-2285
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• 2008

Nowadays, in many mobile device environment, while the demand for using web service is increasing, there are many limitations on web-browsing in wireless network because of various restrictions and problems in reality. We need improvement in function of mobile web service engine because we can't be satisfied with the multiple demands by using previous capacity of web server in rapidly changing web environment. Therefore, this paper improves the service environment for web service users by introducing intermediary technology to web service. This paper embodies intermediary based web service framework for improvement of the function of mobile web service and for the interoperability of mobile device and web server.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2017.10a
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• pp.668-670
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• 2017

Visible Light Communication, which is promising as a next generation near field wireless communications, has been increased study and application case due to the development of LED technology. However, there are few application cases to IoT service due to the necessity of separate equipment for communication and limitation of light transmission to obstacles. In this paper, it propose a portable VLC transceiver module that can be connected to USB OTG and dedicated application for control to realization position possible necessary technique. The string input from the dedicated application is sent to the VLC module via USB OTG to transmit and receive data between the modules. As string transmission experiment result, it is confirmed that ASCII code transmission between VLC transceiver modules is possible through control of the implemented dedicated application.

• 한국HCI학회:학술대회논문집
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• 2008.02a
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• pp.280-285
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• 2008

ZigBee is Low Power and Low Data Rate Wireless Communication protocol. It apply to much Ubiquitous Sensor Network. ZigBee PAN is two type PAN. One is Beacon Enabled PAN, the other is Non Beacon Enabled PAN. To support Low Power in Non Beacon Enabled PAN, End-Device enter Active status at End-Device's wishing time and send a data. So, Router does not know End-Device sends a data time. To solving this problem, Router must always exist to Active status. In this case, Router receive a power supply always in Non Beacon Enabled PAN. But Router does not receive a power supply always, Router can not normal operation, such as Router use a battery. To solve this problem, Router will be support low power. In this paper, we will present Router's Low Power Algorithm. And we suggest 'PAN Time'. Device use 'PAN Time' for PAN synchronous. Router using Low Power Algorithm can be enter to inactive status. So Non Beacon Enabled PAN of Router support the low power mode Therefore Router does not receive a power supply always, Router can normal operation.

• Journal of the Korea Society of Computer and Information
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• v.12 no.5
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• pp.83-92
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• 2007

In this paper, we present a design and implementation of three dimensional pointing device using Inertial Navigation System(INS) that acquires coordinates and location information without environmental dependancy. The INS measures coordinates based on the data from gyroscope and accelerometer and corrects the measured data from accelerometer using Kalman-Filter. In order to implement the idea of three dimensional pointing device, we choose a three dimensional Space-recognition mouse and use RFIC wireless communication to send a measured data to receiver for printing out the coordinate on display equipment. Based on INS and Kalman-Filter theoretical knowledge, we design and implement a three dimensional pointing device and verified the usability as an input device that can capture a human's move. also, we describe the applicability of this device in ubiquitous computing environment.

• Proceedings of the KSR Conference
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• 2011.05a
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• pp.895-903
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• 2011

The Seoul Metropolitan Rapid Transit Corporation(SMRT) is studying the New Train Control System based on Wireless Communication(CBTC System : Communication Based Train Control System) to overcome the limitations of the existing system and to deal with the switch to the new system. The SMRT's New Train Control System Based on three main elements(train position detecting, radio communication and train control) is being developed in 3 stages. Currently, the development of the train position detecting element with the RFID system and the train position detecting device and the radio communication element with RTIS and DSRC had been developed and equipped on 3 stations(Songpa~Garak Market~Munjeong, 7.3km) of Subway Line 8 in the pilot. Such a basic infrastructure of the SMRT's New Train Control System is having an efficiency test by using the real-time Train Monitoring System and Currently, the third element, the train control(ATP/ATO/ATS/Interlocking) for the study is in progress. Also, the developed system is expected to validate the performance and safety in the next three stage. This paper shows about major developments of the SMRT's New Train Control System and our future plans.