• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2000년도 제15차 학술회의논문집
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• pp.400-400
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• 2000

This paper purposed that verify the validity of Petri Net method for control progressive increase of system complexity, before extend the realized single robot system to multi-robot system. An autonomous mobile robot(AMR) needs decision making, motion control, path planning, tracking a path, obstacle avoidance, and sensor fusion, to complete its task. An AMR integrates and operates these technics through a consistent command system. An error in a command hierarchy which is like duplication or omission of a control command hierarchy for each module results in serious problems. This paper minimizes the error by modeling each module and whole system using Petri Net graphical representation and applies it to the exploration task of an AMR

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2004년도 SMICS 2004 International Symposium on Maritime and Communication Sciences
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• pp.20-23
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• 2004

In non-selective frequency environment, it is difficult to take the advantage of path diversity. In the literature, some methods have been proposed to solve the issue. This paper presents a new method to obtain the resolvable path in Indoor Multi-carrier Code Division Multiple Access (MC-CDMA) system by using downlink beam forming. With the aid of downlink beamforming, the most reliable path is found and chosen for the communication link. The new approach is evaluated in term of bit error rate (BER) and power consumption. The simulation results show that the new approach can get better BER performance. However, the cost of BER improvement is a small degradation in power reservation.

• 한국정밀공학회지
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• 제28권2호
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• pp.168-175
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• 2011

Contouring accuracy of CNC machine tools is very important for high-speed and high-precision machining. In particular, large contour error may occur during corner tracking. In order to reduce the corner contouring error, acceleration and deceleration control or tool-path planning methods have been suggested. However, they do not directly control the corner contouring error. In the meantime, network servo systems are widely used because of their easiness of building and cost effectiveness. Communication latency between the master controller and servo drives, however, may deteriorate contouring accuracy especially during corner tracking. This paper proposes a control strategy that can accurately calculate and directly control the corner contouring error. A prediction control is combined with the above control to cope with communication latency. The proposed control method is evaluated through computer simulation and experiments. The results show its validity and usefulness.

• 한국항해항만학회지
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• 제34권10호
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• pp.769-774
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• 2010

수중 통신 시스템의 성능은 수중채널의 특성에 영향을 받으며, 잔향 및 다중경로(Multi-path)로 인한 지연확산은 데이터 전송 시인접 심벌간의 간섭(Inter Symbol Interference : ISI)의 원인이 되며, 이는 통신 성능 저하의 주 원인이 된다. 본 논문에서는 잔향 및 다중경로로 인한 인접 심벌간의 간섭을 극복하기위해 OFDM(Orthogonal Frequency Division Multiplexing) 변조기법을 이용한 수중에서의 음향통신 실험을 통해 그 성능을 분석하였다. 그 결과 전송속도가 2 kbps인 경우 BER(Bit Error Rate)이 $1.22{\times}10^{-1}$이였으며, 전송속도가 4 kbps인 경우 BER은 $2.47{\times}10^{-2}$이었다.

• 한국전자파학회:학술대회논문집
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• 한국전자파학회 2003년도 종합학술발표회 논문집 Vol.13 No.1
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• pp.594-598
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• 2003

In this paper, we analyze the performance of UWB(Ultra-WideBand) communication system employing Bi-phase modulation and RAKE Receiver under the MAI(Multiple Access Interference) and the OSI(Other System Interference) environment. Using the multi-path channel model recommended by IEEE P802.15.TG3a, the performance degradation Is described with the number of users, the number of RAKE fingers and training sequences. To meet BER 10e-4 for 20 users at the same time, the number of RAKE fingers are proposed from 3 to 32. And the number of training sequences are limited less than 8 to keep the channel estimation error within 3dB

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제8권2호
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• pp.678-690
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• 2014

The current networks do not disclose information about a management domain due to scalability, manageability and commercial reasons. Therefore, it is very hard to calculate an optimal path to the destination. Also, due to poor information sharing, if an error occurs in the intermediate path, it is very difficult to re-search the path and find the best path. Hence, to manage each domain more efficiently, an architecture with top-level path computation node which can obtain information of separate nodes are highly needed This study aims to investigate a federation of a united network around NRN(National Research Network) that could allow resource sharing between countries and also independent resource management for each country. Considering first the aspects that can be accessed from the perspective of a national research network, ICE(Information Control Element) and GFO(Global Federation Organizer)-based architecture is designed as a top-level path computation element to support traffic engineering and applied to the multi-domain network. Then, the federation for the independent management of resources and resource information sharing among national research networks have been examined.

• 방송공학회논문지
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• 제11권1호
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• pp.100-106
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• 2006

본 논문에서는 지상파 디지털 방송시스템의 단일 주파수망 (SFN; Single Frequency Network) 구성을 위해 DTV (Digital Television)의 TxID (Transmitter Identification)용 저간섭 ZCD (Zero Correlation Duration) 확산코드를 제시하였다. ZCD 확산 코드는 코드발생기의 구현이 용이함과 동시에 ZCD 특성을 가짐으로 인해서, TxID에서 발생되는 인접코드 간섭 (ICI; Inter Code Interference) 및 다중경로 간섭 (MPI; Multi-Path Interference) 문제를 확산코딩기법을 이용하여 근원적으로 해결해주는 역할을 하고 있으며, 주기를 가변적으로 조절할 수 있어 TxID를 위한 워터마킹 (Watermarking)시에 발생하는 Truncated error 를 제거할 수 있다. 본 논문에서는 AWGN (Additive White Gaussian Noise) 잡음 및 ICI, MPI와 같은 다양한 간섭환경을 모의실험에 반영하여 도출된 DER (Detection Error Rate) 특성을 분석함으로써, TxID용 저간섭 ZCD 확산코드의 유용성을 입증하였다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.895-898
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• 2003

The higher precision is demanded in modem manufacturing and it requires the more accurate servo controller. Cross-coupling control (CCC) has been developed to improve contouring motion. In this paper we introduce a new nonlinear CCC that is based on contour-error-vector using a parametric curve interpolator. A vector from the actual tool position to the nearest point on the desire path is directly adopted. The contour-error-vector is determined by constructing a tangential vector of nearest point on desired curve and determining the vector perpendicular to this tangential vector from the actual tool position. Moreover, the vector CCC can apply directly and easily to free-form curves include convex and concave form. The experimental results on a three-axis CNC machine center show that the present approach significantly improves motion accuracy in multi-axis motion

• 한국통신학회논문지
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• 제17권9호
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• pp.1020-1028
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• 1992

본 논문에서는 TCM(Trellis Coded Modulation)에서 연집에러 검출 및 최대 확률론적 복호 방식으로 구성된 연집에러 정정을 위한 적응 복호방식을 제시하고 있다. 복호기는 보통 비터비 복호기로서 동작하고, 미터비 복호기에 의해 정정될 수 없는 에러가 검출될 경우 연집 에러 정정 모드로 절환된다. 이동통신에서의 채널특성인 연집에러가 빈번히 발생하는 다경로 페이딩 채널에서 적응 복호방식을 이용한 TCM은 기존의 방식에 비해 비트오율면에서 향상된 성능을 나타내고 있다.

• 한국통신학회논문지
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• 제31권10C호
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• pp.956-963
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• 2006

네트워크 가상 환경에서 다중 참여자 일관성 유지와 3D 장면의 동적데이터 공유를 연구한다. 클라이언트-서버구조의 분산 가상환경에서 일관성은 상태정보 교환으로 유지되며, 교환되는 동적데이터의 갱신메시지가 자주 브로드캐스트 되면 패킷 지연에 의한 jerk를 일으키므로 데드레커닝 알고리즘을 이용한 이동경로를 예측하여 네트워크 병목을 줄인다. 동적데이터 경로예측은 데드레커닝 수렴간격의 타당성을 실험하여 공유객체 위치를 근거로 예측값과 실제 상태 값과의 오차가 한계값 이상일 때 이전 위치를 보간하고, VRML EAI를 이용하여 3D 가상공간의 동적 데이터 공유를 구현한다.