• Journal of Advanced Marine Engineering and Technology
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• v.40 no.9
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• pp.799-804
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• 2016

Broadband powerline communication (BPLC) uses distribution lines as a medium for achieving effective bidirectional data communication along with electric current flow. As the material characteristics of power lines are not good at the communication channel, the development of power line communication (PLC) systems for internet, voice, and data services requires measurement-based models of the transfer characteristics of the network suitable for performance analysis by simulation. In this paper, an analytic model describing a complex transfer function is presented to obtain the attenuation and path parameters for a multipath power line model. The calculated results demonstrated frequency-selective fading in multipath channels and signal attenuation with frequency, and were in good agreement with the experimental results. Inductive coupling units are used as couplers for coupling the signal to the power line to avoid physical connections to the distribution line. The inductance of the ferrite core, which depends on the frequency, determines the cut-off frequency of the inductive coupler. Coupling loss can be minimized by increasing the number of windings around the coupler. Coupling efficiency was improved by more than 6 dB with three windings compared to the results obtained with one winding.

• Proceedings of the IEEK Conference
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• 2000.06a
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• pp.41-44
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• 2000

In this paper, an improved timing synchronization method for OFDM system is proposed. In multipath fading channels, timing offset estimation algorithm based on simple correlation metric can cause inter-symbol interference (ISI). The proposed algorithm promises accurate timing offset estimation, which can be achieved by simple windowing. The estimation errors in several multipath channels are evaluated in computer simulations.

• Proceedings of the IEEK Conference
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• 2000.11a
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• pp.69-72
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• 2000

In CDMA systems, the performance of the typical multipath searcher degrades much according as the signal to noise ratio becomes low. In this paper, multipath searcher algorithm is proposed based on sliding window to overcome this drawback. In searcher systems, correlation values between incoming and local PN sequences are used to acquire multipath components. Therefore more accurate distributions of correlation values obtained through this proposed algorithm enables to get higher detection probability. In computer simulations, it is verified that proposed algorithm has better performances in Rayleigh fading channel and Gaussian channel.

• Proceedings of the IEEK Conference
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• 2001.09a
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• pp.69-72
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• 2001

본 논문에서는 디지털 통신 시스템의 블라인드 등화에 있어서, 다중레벨 modulus를 기준 신호로 사용하여 등화기의 탭 계수 갱신 식에 사용되는 오차 신호를 형성함으로써 등화기의 블라인드 수렴 특성을 개선한 다중레벨 modulus 알고리즘들의 성능을 분석하였다. 다중경로 채널 하에서 QAM 신호점에 대해 컴퓨터 모의실험을 통하여 단일/다중레벨 modulus 알고리즘(SMMA)과 기존의 modified constant modulus algorithm(MCMA) 및 최근에 제안된 다중레벨 modulus 알고리즘(MMA) 등의 블라인드 수렴 및 정상 상태 성능을 비교하였다.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.4 no.3
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• pp.30-36
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• 1993

This paper presents the RAKE receiver over a multipath fading channel. This interference between the propagation paths in a multipath fading causes a serious degradation in the mobile communication environment. In order to derive the path interference and reduce the fading effect, the RAKE receiver is used. As a result, the RAKE receiver gives a better performance than the DS / SS receiver over a multipath fading channel.

• Journal of the Korean Professional Engineers Association
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• v.26 no.3
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• pp.26-33
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• 1993

위성을 이용한 DAMA-SCPC 지구국시스템의 경우 대체적으로 전송경로상에서 발생되는 에러를 제어하는 방법으로 FEC 기법을 채택하고 있다. 본 고에서는 DAMA -SCPC 지구국 시스템의 설계에 적용할 수 있도록 길쌈부호와 Viterbi 복호법, 그리고 (m-1)/m의 부호율을 위한 소기식 길쌈부호에 대해 살펴보고, 상용화 FEC CODEC 제품 중 가격이 비교적 저렴하고 다양한 기능을 제공하는 QUALCOM사의 Q0256 CODEC의 구성 및 제공 기능에 대해 분석한 후, 이 FEC CODEC을 DAMA-SCPC 지구국 시스템의 채널부에 적용시킬 때의 내장 부가 장치와 제공 기능들의 설계 및 이용 방안에 대해 고찰하였다.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.04a
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• pp.821-824
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• 1999

콘크리트 케이슨 제작장(Casting Bed)내에 케이슨의 제작 및 이동경로가 되는 이동통로(Trough)를 형성하고 거푸집과 이동통로를 겸할 수 있도록 고안한 소핏폼(Soffit Form)을 설치함으로써, 제작된 케이슨 하부로 케이슨 부양용 에어로 고(Aero Go)가 양방향으로 자유로이 이동할수 있게 하여 제작에서 운반까지의 각 단계별 공정이 일직선상에서 공장식 연속 조립공정으로 진행되며, 또한 별도의 대차 및 회수시설이 불필요한 공장형 일관 제작 시스템에 의한 다단계 케이슨 제작, 운반 및 진수방법이다.

• 제어로봇시스템학회:학술대회논문집
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• 1991.10a
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• pp.1057-1062
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• 1991

Recently, due to the development of new technology and products, FA has been accelerating for obtaining high-quality and saving of resources and power. Introduction of automation to the field which has bad working condition is needed and welding is one of these field. In this study, solving algorithm for down hand control which requires in the automatic are welding system is proposed. For the verification of the algorithm, numerical examples are shown and visualization is carried out using developed graphic tools.

• Proceedings of the IEEK Conference
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• 2003.07a
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• pp.206-209
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• 2003

본 논문에서 제안하는 알고리즘은 심벌 타이밍 jitter 를 최소화하기 위해 가장 강한 신호를 주기적으로 감시하고, 그 신호를 적응적으로 DLL(Delayed Locked Loop)의 기준 신호로 정한다. 결과적으로 제안된 알고리즘은 DLL 추적 실패를 피할 수 있고, 기존의 알고리즘에 비하여 DLL의 정상 상태 추적 오류가 작다. 모의실험을 통하여 제안된 알고리즘의 정상상태 DLL 추적오류가 작고 다중 경로 상황에서 DLL 추적 실패를 피할 수 있음을 확인 하였다. 따라서 본 논문에서 제안하는 알고리즘은 OFDM 의 시간동기 복원 알고리즘에 적합하다.

• Proceedings of the IEEK Conference
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• 2001.06a
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• pp.353-356
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• 2001

In WCDMA systems, it is difficult to use high level modulation schemes in Rayleigh fading channel. Components of Multipath interference give signals much inteferences. Multipath interference cancellation is one of the method to overcome this problem. In this paper, multistage PIC algorithm is used to verify a performance of multipath interference cancellation. It is algorithm gradually canceling the multipath interferences as a stage number is increases. In computer simulations, it is verified that multipath interference cancelation is necessary and using its algorithm give much better performances than not using.