• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.11A
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• pp.1059-1065
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• 2010

Recently, analog broadcasting are being converted into digital radio broadcasts, Among the various ways that HD Radio is a candidate for the U.S. approach, Digital Radio will transmit a digital signal to existing analog FM/AM. It provides clear sound quality, traffic information, weather information and various value-added services. In addition, the converted digital radio will be able to meet demand to growing demand for analog FM. In this paper, Digital FM Radio system in the same frequency band using electric field strength of the received digital radio broadcasting interference effects were analyzed. And Digital FM Radio Receiver interference effects were analyzed by interference signal power and signal power. Results were confirmed by applying equation at minimum field strength and SNR.

• Journal of Korean Society for Geospatial Information Science
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• v.17 no.2
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• pp.123-131
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• 2009

The telecommunication technology in the 21st century has come up to the standard which could transmit various spatial information by means of on-line and the printing technology using computers has been on a par with presswork in quality. In addition, map users also would like to get various spatial information through on-line directly or indirectly. None the less, the supply system of national base map in our country has maintained the off-line sales method. It is owing to this reason that the nation's supply system has shown a high degree of inefficiency from the viewpoint of the inventory control, rapidity, and economical efficiency as compared with the on-line sales system in the developed countries. This study tried to analyze some problems of the present supply system in order to build up the foundation of the efficient map supply system and also developed the system such as On-demand maps, on-line paying and sales, inventory control, meta dat establishment, and security module, etc. This study tried to analyze some problems of the present supply system in order to build up the foundation of the efficient map supply system and also developed the system such as On-demand maps, on-line paying and sales, inventory control, meta dat establishment, and security module, etc.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.1
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• pp.159-169
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• 1994

A multichannel optical slotted ring network is designed using a wavelength division multiplexing(WDM) technique and photonic packet switching devices. The electronics speed bottleneck is removed out of the ring, which allows utilization of the full bandwidth for the optical fiber transmission medium. The ring channel adopts a slotted ring concept with a destination cell remove strategy for the eing access mechanism. The slot size in the ring is selected as the same as that of ATM based cell in order to be used as B-ISDN Access Networks. In this paper, we devised a mathematical method to measure the average transfer delay characteristics of the network. The analytical method turned out to yield accurate results over a broad range of parameters in comparison to simulation results. From the study, we observed the average transfer delay of the network as the network parameters vary.

• Journal of Internet Computing and Services
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• v.8 no.1
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• pp.79-85
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• 2007

As the use of the computer and networks generalized, the various tasks which are requested secrets can be processed such os the banking transaction. And because of increasing of data exchange, Internet, and mobile networks, the method which is not connected only but also used with many users has been changed. Especially because of the structural problem of the Internet, a lot of information is leaked out when we use the Internet banking. If we check the Internet banking by using an existing cypher method which is either simple of slow, a credit card number, an account number or password will be leaked out. Because the security of information doesn't meet our expectation, we need more powerful cryptography. But, the wasted space-time which is required shouldn,t be ignored when the whole transferred data are encrypted. So, by using both the Elliptic Curve algorithm which is based on mobile networks and the partial encryption of the DTD of XML in this essay, we will implement more faster cypher method of the partial XML.

• Proceedings of the KAIS Fall Conference
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• 2009.05a
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• pp.587-590
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• 2009

천식환자의 폐활량 측정 및 관리는 정기적으로 검사되어 관리될 필요가 있는 매우 중요한 관리 항목이다. 본 연구는 천식환자의 폐활량을 정기적으로 관리할 수 있도록 PC-기반 폐활량기를 이용한 천식환자의 폐활량 측정 및 관리 시스템의 설계 및 구현에 관한 연구이다. 폐활량 검사는 크게 3종류 구성되며, 본 연구는 노력성 폐활량 검사(Forced Vital Capacity Test)를 1차적으로 설계 및 구현 방법을 제안하였다. FVC 검사의 목적은 폐질환의 진단, 중증도 그리고 치료효과 판정, 기관지 천식의 진단 및 관리, 수술시 마취방식의 결정 등으로 무엇보다 정확한 검사와 정기적인 검사를 필요로 하는 중요한 검사이다. FVC 검사는 검사과정에서 천식환자에게 많은 노력을 필요로 하는 힘든 검사로서 검사자의 도움이 필수적이므로 폐활량 검사 프로그램 개발에 있어 고려되어 알고리즘이 효율적으로 개발되어야 한다. 본 시스템은 휴대형 폐활량기(Spirometer)를 PC에 연결하고, 폐활량을 측정할 수 있도록 구성되었고, 검사 내용은 PC의 DB에 저장하고, 추후에 정기적으로 서버의 DB로 전송함으로서 보다 더 폭넓은 관리를 가능하도록 하며 천식환자는 서버가 제공하는 웹 사이트를 이용함으로서 자신의 건강관리를 가능하도록 구성된다. FVC 검사 프로그램은 정확한 검사와 편리한 사용자 인터페이스를 제공하도록 설계 및 구현하였고 따라서 자체 개발된 폐활량기를 PC-기반 프로그램으로 제어 가능함으로서 추후 다양한 임상실험의 데이터 확보, 기능의 확장과 성능의 개선을 할 수 있고, 좀 더 편리하고, 정확한 폐활량측정이 가능 할 것이다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37A no.10
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• pp.827-833
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• 2012

The receiver performance is degraded by nonlinear memory problem in communication system. The pre-distorter techniques are an effective technique to compensate for the nonlinear distortion of the HPA without memory effects. However, memory effect of HPA can no longer be ignored when data signal is transmitted in high speed. Many adaptive pre-distorter schemes have been studied to compensate for memory effect problem of HPA in transmitter. The complexity and cost of satellite will increase when using adaptive pre-distorter in satellite communication system. In this paper, we propose receiver feedback closed loop pre-distortion technique in order to compensate for nonlinear problem of HPA with memory problem. The purpose of this paper is to reduce complexity and cost of satellite design by using only pre-distorter at terrestrial station.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.2C
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• pp.145-152
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• 2009

Ultra-wideband communication systems for impulse radio have merits that are possible for either high resolution ranging system or radio determination. Conventionally, in order to accomplish these functions, the rapid analog to digital convertor (ADC) is necessary to apply radio determination system operating in time domain. However, considering that low rate - wireless personal area network (LR-WPAN) aims to low-cost hardware implementation, the expensive ADC converting GHz sampling per second is not appropriate. So, this paper introduces the high resolution ranging system operating in frequency domain with using low sampling rate ADC, and a new non-coherent ranging scheme utilizing analog Frequency Modulation (FM) mode for the frequency domain transformation. To verify the superiority of the proposed ranging algorithm working in frequency domain, the suggested IEEE 802.15.4a TG channel model is used to exploit affirmative features of the proposed algorithm with conducting the simulation results.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.12A
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• pp.1172-1176
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• 2008

In this paper, we describe the implementation and performance of a dual-mode Software Define Radio (SDR) smart antenna base station system. SDR technology enables a communication system to be reconfigured through software downloads to the flexible hardware platform that is implemented using programmable devices such as Digital Signal Processors (DSPs), Field Programmable Gate Arrays (FPGAs), and microprocessors. The presented base station channel card comprises the physical layer (pHY) including the baseband modem as well as the beamforming module. This channel card is designed to support TDD High-Speed Downlink Packet Access (HSDPA) as well as Wireless Broadband Portable Internet (WiBro) utilizing the SDR technology. We first describe the operations and functions required in WiBro and TDD HSDPA. Then, we explain the channel card design procedure and hardware implementation. Finally, we evaluate WiBro and TDD HSDPA performance by simulation and actual channel-card-based processing. Our smart antenna base-station dual-mode channel card shows flexibility and tremendous performance gains in terms of communication capacity and cell coverage.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39B no.10
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• pp.708-714
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• 2014

Wireless sensor networks (WSNs) generally consist of densely deployed sensor nodes that depend on batteries for energy. Having a large number of densely deployed sensor nodes causes energy waste and high redundancy in sensor data transmissions. The problems of power limitation and high redundancy in sensing coverage can be solved by appropriate scheduling of node activity among sensor nodes. In this paper, we propose a cellular automata based node scheduling algorithm for prolonging network lifetime with a balance of energy savings among nodes while achieving high coverage quality. Based on a cellular automata framework, we propose a new mathematical model for the node scheduling algorithm. The proposed algorithm uses local interaction based on environmental state signaling for making scheduling decisions. We analyze the system behavior and derive steady states of the proposed system. Simulation results show that the proposed algorithm outperforms existing protocols by providing energy balance with significant energy savings while maintaining sensing coverage quality.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.3
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• pp.263-268
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• 2002

DFDM is a good candidate for beyond-3G high-speed wireless communication application because of the robustness to the intersymbol interference and multipath fading. However. an OFDM signal has a serious problem of the high PAPR, which results in the significant nonlinear distortion when it passes through a nonlinear high power amplifier. We propose a new PAPR reduction method using pre-emphasis and clipping. Via the proposed method, the OFDM output signal can have a low PAPR and BER improvement. Then. de-emphasis process is requisite in OFDM receiver. PAPR is reduced to about 5.7 ㏈ at the CCDF= 10$\^$-3/ when the subcarrier number is 16, QPSK modulation is used. pre-emphasis change point Is 3/9 of the peak amplitude of the IFFT output and clipping level is 11 in the IFFT output amplitude. The required SNR at BER=10$\^$-3/ the proposed system is improved by 2 dB than that of the original OFDM system.