• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.1
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• pp.129-137
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• 2010

There are a lot of multimedia functions getting included in mobile devices recently, not only simple audio but visual functions as well, such as video playing, game and web browsing. Such the visual multimedia functions brought the strong requirement for much bigger LCD Display and high resolution. And the brightness of LCD is also one of major requirements and it is required to be more bright. However, LCD brightness is limited to increase because of power consumption. It occupies nearly 30% of the whole system power. This thesis suggests an effective and simple method of adjusting the LCD backlight brightness, considering a characteristic of battery and user pattern.

• IEMEK Journal of Embedded Systems and Applications
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• v.8 no.5
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• pp.285-293
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• 2013

The procedure of the arbitration which is the tag collision is essential because the multiple tags response simultaneously in the same frequency to the request of the Reader. This procedure is known as Anti-collision and it is a key technology in the RFID system. In this paper, we propose the Bit Pattern Prediction Algorithm(BPPA) for the efficient identification of the multiple tags. The BPPA is based on the tree algorithm using the time slot and identify the tag quickly and efficiently using accurate bit pattern prediction method. Through mathematical performance analysis, We proved that the BPPA is an O(n) algorithm by analyzing the worst-case time complexity and the BPPA's performance is improved compared to existing algorithms. Through MATLAB simulation experiments, we verified that the BPPA require the average 1.2 times query per one tag identification and the BPPA ensure stable performance regardless of the number of the tags.

• Journal of The Korean Association of Information Education
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• v.18 no.2
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• pp.325-334
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• 2014

There are management and price problems that have been caused by requirement of RFID reader, Fingerprint Identification System and Clicker for the construct of automatic attendance system to check the students' attendance accurately and quickly. Therefore, in the thesis, we developed smartphone based attendance check system by utilizing Wi-Fi and the smartphones that has been already built without using additional equipments and establishing construction of system additionally. It recognizes date, time, location and the seat number in classroom if a student logs the attendance chocking application in and it also allows students to get lecture feedback and check attendance by taking quizzes and questionnaires that are related to the lecture. As a result, by applying the attendance check system, instructors state that it is convenient since the app allows instructors to communicate with students though the quizzes and questionnaires. Especially, the instructors state that it is convenient because the results of the quizzes, questionnaires and attendance can be downloaded it the from of Excel files.

• Journal of the Korean Institute of Intelligent Systems
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• v.26 no.1
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• pp.82-86
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• 2016

This paper proposes a method for the immobilization of motorbike brakes in conjunction with near-field communication (NFC) technology in order to meet the increasing demand for security and convenience of motorbike drivers. We thought about the concept of wireless key, NFC security devices and automatic solenoid valve for setting the lock and unlock module. This paper propose the design and development of an innovative anti-theft alarm system for motorcycles using NFC smart devices based on RFID system, the basis of IoT and AES(advanced encryption standard) encryption Algorithm. The design concept is based on NFC communication strategy between the vehicle and owner. To do this concept, we designed motorcycle smart key system with general-purpose NFC system and the automatic solenoid valve for setting the lock and unlock module. First, we designed control unit and NFC card reader for motorcycle smart key system. Then we propose an AES encryption algorithm and prove that the motorcycle key system is controllable by showing the result of implementing and testing, after installing.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2007.10a
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• pp.921-924
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• 2007

In this paper, we have implemented a ubiquitous healthcare system that can measure and check human's health in anytime and anywhere. The implemented prototype are composed of both front-end and back-end. The front-end have several groups: environment sensor group such as temperature, humidity, photo, voice sensor, health sensor group such as blood pressure, heart beat, electrocardiogram, spo2 sensor, gateway for wired/wireless communication, and RFlD reader to identify personal. The back-end has a serial forwarder to propagate measurment results, monitor program, and medical information server. The implemented sensor node constructs a sensor network using the Zigbee protocol and is ported the TinyOS. The data gathering base node is linux-based terminal that can transfer a sensed medial data through wireless LAN. And, the medical information server stores the processed medical data and can promptly notify the urgent status to the connected medical team. Through our experiments, we've confirmed the possibility of ubiquitous healthcare system based on sensor network using the Zigbee.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.2A
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• pp.177-183
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• 2009

In this paper, we propose an improved anti-collision algorithm. We have designed an anti-collision unit using this algorithm for the 18000-6 Type C Class 1 Generation 2 standard (Gen2). The Gen2 standard uses a Q-algorithm for incremental method on the Dynamic Slot-Aloha algorithm. It has basically enhanced performance over the Slot-Aloha algorithm. Unfortunately, there are several non-clarified parts: initial $Q_{fp}$ value, weighted C, and the ending point of the algorithm. If an incorrect value is selected, it causes degradation in performance. Thus we propose an improved anti-collision algorithm by clearly defining the vague parts of the existing algorithm. Simulation results showed an improved performance of up to 34.8% using an optimized value of C and the initial $Q_{fp}$ value. With the ending condition, performance is 34.7%. The anti-collision unit is designed using the Verilog HDL. The module was synthesized using Synopsys' Design Compiler and the TSMC $0.2{\mu}m$ standard cell library. The synthesized result yielded 3,847 gates, and was guaranteed under the proposed working frequency of 19.2MHz.

• International Journal of Fuzzy Logic and Intelligent Systems
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• v.7 no.4
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• pp.228-235
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• 2007

The main purpose of this paper is to manage the container property effectively at the container yard by applying the RTLS technology to the field of port logistics. Yet, many kinds of noises happen to be inputted with the distance value(between the reader and the tag) which is to be inputted into the location identification algorithm, which makes the distance value jumped due to the system noise of the ultrasonic sensor module and the measurement noise. The Kalman Filter is widely used to prevent this jump occurrence; the noises are eliminated by using the EKF(Extended Kalman Filter) while considering that the distance information of the ultrasonic sensor is non-linear. Also, the 3D RTLS system at the port container yard suggested in this research is designed not to be interrupted for its ultrasonic transmission by positioning the antenna at the front of each sector of the container where the active tags are installed. We positioned the readers, which function as antennas for location identification, to four places randomly in the absolute coordinate and let the positions of the active tags identified by using the distance data delivered from the active tags. For the location identification algorithm used in this paper, the triangulation measurement that is most used in general is applied and newly reorganized to calculate the position of the container. In the first experiment, we dealt with the error resulting in the angle and the distance of the ultrasonic sensor module, which is the most important in the hardware performance; in the second, we evaluated the performance of the location identification algorithm, which is the most important in the software performance, and tested the noise cancellation effects for the EKF. According to the experiment result, the ultrasonic sensor showed an average of 3 to 5cm error up to $45^{\circ}$ in case of $60^{\circ}$ or more, non-reliable linear distances were obtained. In addition, the evaluation of the algorithm performance showed an average of $4^{\circ}{\sim}5^{\circ}$ error due to the error of the linear distance-this error is negligible for most container location identifications. Lastly, the experiment results of noise cancellation and jump preservation by using the EKF showed that noises were removed in the distance information which was entered from the input of the ultrasonic sensor and as a result, only signal was extracted; thus, jumps were able to be removed and the exact distance information between the ultrasonic sensors could be obtained.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2006.05a
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• pp.957-960
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• 2006

In this paper, we studied the location estimation algorithm of a spatial 3 dimension which extend the location estimation algorithm of a plane 2 dimension in 2.45GHz band RTLS(Real time location system). We used TDOA scheme which need not a time of transmission information of the tag and estimated 3 dimension coordinates. Also, estimated intersection of hyperbolic curve to X, Y coordinate of the tag at 2D coordinates searching area, $300m\times300m$ and LOS propagation environments. And, we estimated Z coordinate ultimately using X, Y coordinate. The location estimation algorithm of a spatial 3 dimension satisfies the RTLS specification requirement, 3m radius accuracy. From the result, we confirm that the location of tag which similar to actual coordinate in the case to an ideal received offset. However, we verified that the location of tag which escapes from a radius 3m within error range when received offset increased. Therefore, as the future work we are consider enhanced location accuracy of a spatial 3 dimension in RTLS system which using the decrease scheme of reader offset or the discriminate scheme of the estimation location.