• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.12
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• pp.2249-2260
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• 2017

IMO (International Maritime Organization) has been providing GMDSS (Global Maritime Distress and Safety System) and mandating to install distress and safety systems according to SOLAS. Digital-HF(High-Frequency) coast station communication system maintains interoperability between ship and coast station and digital data exchange in maritime mobile service by digitizing existing analog base voice communication. In this paper, we analyze ITU-R M. 1798-1 established by ITU for digital HF communications and propose Advanced annex2 and new Annex 5 to improve the problems of the existing Annex 2 and Annex 4. The proposed OFDM protocol basically adopts ARQ (Automatic Retransmission Request) which retransmits when an error occurs in a half-duplex manner between an information transmitting side (ISS) and an information receiving side (IRS) and we propose a digital HF communication system and its operational concept which is more reliable and superior than the existing ITU-R M. 1798 by implementing technical development on implementation and performance improvement.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2001.05a
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• pp.359-362
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• 2001

Analog communication systems using AM, FM modem have been developed. Digital communication systems using digital modems, which is by expansion of digital hardware skill have been recently developed. In order to accomplish a reliable communication it is important to overcome ocean environmental channel characteristics such as transmission loss, ambient noise and multipath effect etc. Specially, the effect of multipath is the most important element that determines the performance of underwater communication system in shallow water. Multipath channel can be divided a vertical and horizontal channel. the former is defined the channel to have large path-delay times between a direct wave and reflected waves. The latter shows relatively small path-delay times between a direct and reflected waves in compared with a vertical channel. In this paper, The performance of FSK, PSK and DPSK modem with respect to the vertical and horizontal multipath communication channels it described and compared.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.18 no.2
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• pp.192-201
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• 1993

According to technical advances of telecommunication, communication network has changed to digital transmission from analog transmission network. In the long run, current network will be altered into ISDN which makes end-to-end digital communication. This transition of communication network brings about an important questions for networking plan, administration, and speech quality in order to achieve the effective and advanced telecommunication. Speech quality criterions and degradation factors of digital communication system differ from those of existing analog system because of other characteristics like single echo. It is, therefore, necessary to design new criterions and specifications for digital communication network. This Paper describes the relation between speech communication and speech transmission quality and describes the implementation of model system for quality evaluation of digital speech communication network. In addition, some applications of model system implemented are proposed.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.7
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• pp.641-647
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• 2015

In this paper, Analyzed the multi-channel signal processing algorithms for digital-transponder. To analyze suitable multi-channel signal processing algorithms, compare algorithms about four criteria. Four criteria are as follows, perfect reconstruction, interference rejection, resource usage and power consumption. Analysis for each algorithm in accordance with these four criteria. then propose the multi-channel signal processing algorithms for digital satellite communication system.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.13 no.2
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• pp.127-137
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• 1988

In this paper, the extracting method for the control subcode in digital audio systems is pressented. And also the subcode format to display on the screen and a extracting method of the control signals within the DAS information are described. The extracted control signal from DAS is analyzed in the microprocessor systems and the microprocessor systems generate the screen information and then transmit to the CRT controller by the proposed protool.

• Information and Communications Magazine
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• v.21 no.7
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• pp.156-167
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• 2004

이동통신은 아날로그 음성을 전달하는1세대의 아날로그 이동 전화로부터 시작하여 2세대의 디지털 이동통신에서는 디지털 음성 전화 및 단문서비스를 제공하였으며, 3세대 이동통신시스템인 IMT-2000(International Mobile Telecommunications-2000)으로는 동기 방식 cdma2000과 비동기 방식의 W-CDMA에서는 2Mbps급 이상의 데이터 서비스를 제공한다. 현재 서비스 중이거나 계획 중인 WCDMA, cdma2000 1x,cdma2000 1x EVDO와 EVDV는 이동 멀티미디어 서비스의 제공을 목표로 설계되었으나, 현재 이들 3세대 시스템은 2세대 시스템에 비하여 기술적으로 진보된 개념들을 도입하였음에도 불구하고, 서비스 제공 관점에서 2세대 시스템과의 차별화에 성공적으로 대처하지 못하고 있고, 2세대 시스템이 이동전화 서비스를 제공하는데 있어 용량 부족의 문제가 없으므로 사업자들이 신규 투자에 매우 소극적인 상황이다.(중략)

• Proceedings of the Korean Society for Information Management Conference
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• 1995.08a
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• pp.67-70
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• 1995

디지털도서관은 데이터를 디지털화하여 수집ㆍ축적하고, 네트워크를 통해 이용가능한 도서관이라 할 수 있으며. 계산, 데이터축적, 통신관련 기술을 이용하여 완전한 정보서비스를 제공하는 것이 목적이다. 다양한 정보를 디지털화하기 위해서는 멀티미디어기술. 대용량의 데이터축적기술. 통신을 위한 컴퓨터네트워크기술 등이 기반이 되므로 여러 분야와 관련이 되는 것은 틀림없으나 결국 도서관의 역할을 하는 시스템을 만드는 것이 목적이다. 본 연구에서는 디지털도서관 설계시 개념화하고 범주화하여야 할 디지털도서관의 기능, 구조, 범위, 요소기술, 고려사항 등에 대하여 논한다.

• 한국공간정보시스템학회:학술대회논문집
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• 2005.11a
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• pp.93-98
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• 2005

u-city의 구축에는 정보통신관련 전문가가 주도적으로 참여하고 있으며, u-city는 정보통신 인프라 설치, 도시정보관제센터 건립 및 시스템 구축 운영, 디지털 컨텐츠서비스 제공으로 구성된다. 디지털 컨텐츠의 주요구성요소는 서비스생활환경컨텐츠, 도시관리컨텐츠, 상거래컨텐츠로서 공공포탈서비스를 통해 지역 사회에 제공된다. 본고는 디지털 컨텐츠에 추가될 수 있는 컨텐츠로서 건설교통부와 한국토지공사에서 추진하고 있는 국토정보화사업의 개요와 장점을 소개하고 u-city와 연계하며, 향후 u-city의 구축에서 도시계획가 참여의 필요성을 제시한다.

• Information and Communications Magazine
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• v.13 no.8
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• pp.70-81
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• 1996

위성통신시스템의 효율적인 성능분석을 위하여 기존의 통신시스템 시뮬레이션 Tool을 수정 보완하여 위성의 각종 파라미터들의 변화에 따른 전체 위성통신시스템의 성능분석을 디지털 전송 방식에 대하여 수행하였다. 상 하 각각 한 채널씩의 인접채널 간섭을 고려하여 성능분석을 실시한 결과 위성통신시스템에서 단일 반송파를 사용할 경우 시스템의 위상천이, 군지연 특성과 같은 위상관련 특성들이 전체 성능에 결정적인 영향을 미치는 것을 알 수 있다.

• Journal of the Korean Institute of Intelligent Systems
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• v.18 no.5
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• pp.724-729
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• 2008

This paper presents the calculation of the required bandwidth of common frequency bandwidth applying queueing theory for maximizing the efficiency of frequency resource of WPAN(Wireless Personal Area Network) based Digital acoustic and communication devices. It assumed that LBT device(ZigBee) and FH devices (DCP, RFID and Bluetooth) coexist in the common frequency band for WPAN based Digital acoustic and communication devices. Frequency hopping (FH) and listen before talk (LBT) have been used for interference avoidance in the short range device (SRD). The LBT system transmits data after searching for usable frequency bandwidth in the radio wave environment. However, the FH system transmits data without searching for usable frequency bandwidth. The queuing theory is employed to model the FH and LBT system, respectively. As a result, the throughput for each channel was analyzed by processing the usage frequency and the interval of service time for each channel statistically. When common frequency bandwidth is shared with SRD using 250mW, it was known that about 35 channels were required at the condition of throughput 84%, which was determined with the input condition of Gaussian distribution implying safety communication. Therefore, the common frequency bandwidth is estimated with multiplying the number of channel by the bandwidth per channel. These methodology will be useful for the efficient usage of frequency bandwidth.