• Proceedings of the KIEE Conference
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• 2005.10c
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• pp.302-304
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• 2005

무선통신기술의 발달은 Smart열차제어시스템 개발의 동기를 제공하였다. Smart열차제어시스템의 진로제어장치도 무선통신기술을 적용하고 있다. 본 논문에서는 기존연동장치의 특징, 연동논리를 포함한 Smart 진로제어시스템의 개요 등을 검토하여 새로운 연동도표를 제안하고 있다.

• Journal of KIISE:Information Networking
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• v.35 no.2
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• pp.112-119
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• 2008

Today, A matter of concern of home network technology increase. The standard of communication between home network devices are required. IEEE 802.1 AVB(Audio/Video Bridging) specifies transmission method for time-sensitive data between these devices using Ethernet in bridged local area networks. IEEE 802.1 AVB and IEEE 1588 PTP(Precision Time Protocol) have various message type for grandmaster selection and synchronize the devices. These messages bring on complexity protocol. We propose a method that uses Single TimeSync frame in order to the problem. Our proposal is appropriate process complexity and low transmission delay for home network by using the TimeSync frame. Furthermore, after all devices are adjusted to the single TimeSync frame, a resource reservation, a forwarding and queueing rule are needed for a time-sensitive application.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38C no.2
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• pp.141-154
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• 2013

The technology of precise time-synchronization between signal receive devices for separation distance operation can be a key point for the technology with TDoA-based system. We propose a new method for the higher accuracy of system's time-synchronization in this paper, which uses OCXO and DPLL with high accuracy to achieve phase synchronization at 1 pps (pulse per second) of signal. And the method receive time value from a GPS satellite. Essentially, the performance of GPS with high accuracy refers to long-term frequency stability for its reliability. As per the characteristic, as the GPS timing signals are synchronized continuously, the accuracy of time-synchronization gets improved proportionally. Therefore, if the time synchronization is accomplished, the accuracy of the synchronization can be up to 0.001 ppb (part per billion). Through the improved accuracy of the time-synchronization, the measurement error of TDOA-based location detection technology is evaluated. Consequently, we verify that TDoA-based location measurement error can be greatly improved via using the improved method for time-synchronization error.

• Journal of KIISE:Computer Systems and Theory
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• v.29 no.6
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• pp.331-339
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• 2002

This paper presents a garbage collection protocol for checkpoints and message logs which are staved on the stable storage or volatile storage for fault tolerancy. The previous works of garbage collections in coordinated checkpointing protocol delete all the checkpoints except for the last checkpoints on earth processes. But implemented in top of reliable communication protocol like as TCP/IP, rollback recovery protocol based on only last checkpoints makes sympathetic rollback. We show that the old checkpoints or message logs except for the last checkpoints have to be preserved in order to replay the lost message. And we define the conditions for garbage collection of checkpoints and message logs for lost messages and present the garbage collection algorithm for checkpoints and message logs in coordinated checkpointing protocol. Since the proposed algorithm uses process information for lost message piggybacked with messages, the additional messages for garbage collection is not required The proposed garbage collection algorithm makes 'the lazy garbage collectioneffect', because relying on the piggybacked checked checkpoint information in send/receive message. But 'the lazy garbage collection effect'does not break the consistency of the whole systems.

• Science of Emotion and Sensibility
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• v.6 no.4
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• pp.15-23
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• 2003

Recently, there have been many attempts to develop BCI (brain computer interface) based on EEG (electroencephalogram). Measurement and analysis of EEG evoked by particular stimulation is important for the design of brain wave pattern and interface of BCI. The purpose of this study is to develop a general-purpose system that measures subject's reaction time after audio-visual stimulation which can work together with any other biosignal measurement systems. The entire system is divided into four modules, which are stimulation signal generation, reaction time measurement, evoked potential measurement and synchronization. Stimulation signal generation module was implemented by means of Flash. Measurement of the reaction time (the period between the answer request and the subject reaction) was achieved by self-made microcontroller system. EEG measurement was performed using the ready-made hardware and software without any modification. Synchronization of all modules was achieved by, first, the black-and-white signals on the stimulation screen synchronized with the problem presentation and the answer request, second, the photodetectors sensing the signals. The proposed method offers easy design of purpose-specific system only by adding simple modules (reaction time measurement, synchronization) to the ready-made stimulation and EEG system, and therefore, it is expected to accelerate the researches requiring the measurement of evoked response and reaction time.

• Journal of the Korea Society of Computer and Information
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• v.27 no.12
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• pp.9-16
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• 2022

In this paper, we propose a plan to design and utilize the RDBS(Record Block Data file management System) so that data can be recovered when data files in the Combat Management System are mismatched. The CMS(Combat Management System) manages the same files in multiple IPN(Infomation Processing Node) repositories to support multiplexing. However, mismatches in data files can occur due to equipment maintenance or user immaturity. The existing CMS does not manage the history of changes in data files, and when a mismatch occurs, data file were synchronized based on the latest date. But, It is difficult to say that files with the latest date have the highest reliability, and once the file synchronization has progressed, it cannot be recovered with pre-synchronization data. To solve this problem, data was stored and synchronized in units of record blocks using RDBS proposed in this paper, and the Rsync algorithm was used to reduce the overhead of file synchronization due to units of record blocks. SW applied with RDBS was tested for performance in a simulated environment, and it was confirmed that it could be applied to CMS through normal operation confirmation.

• Proceedings of the KIEE Conference
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• 2008.04c
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• pp.224-226
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• 2008

본 논문에서는 매트릭스 컨버터를 이용하여 풍력을 에너지원으로한 영구자석형 동기 발전기의 계통연계방법을 제안하고 시뮬레이션으로 타당성을 검증한다. 풍속의 변화에 따라 영구자석형 동기발전기 속도가 변하며, 발전기 속도의 변화로 인해 발전전압의 크기와 주파수가 변한다. 이렇게 가변하는 발전 전압과 주파수를 계통전압의 고정된 전압 크기와 주파수로 변환하는 전력변환장치로써 기존의 PWM AC/DC/AC 컨버터 대신에 매트릭스 컨버터를 사용하여 직접적으로 AC-AC 변환을 한다. 매트릭스 컨버터가 가지고 있는, DC 링크단의 대용량 캐패시터가 필요없고; 양방향전력흐름을 제어할 수 있고, 사용자가 원하는 출력전압의 크기, 주파수, 역률을 임의로 제어 할 수 있는 이점을 사용하여 매트릭스 컨버터를 이용한 영구자석형 동기발전기의 계통연계에 대한 시뮬레이션 결과를 소개한다.

• Electronics and Telecommunications Trends
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• v.32 no.3
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• pp.98-106
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• 2017

GPS 등과 같은 위성항법 시스템은 정밀한 시각동기가 요구되는 동기식 이동통신망, 전력망, 금융망과 같은 분야와 사용자의 정밀한 위치를 요구하는 차량 내비게이션, 항공기 및 자동차, 측지 측량분야는 물론 향후 드론 및 자율주행 차량 등과 같은 다양한 응용분야에서 그 활용도가 증가될 것이다. 또한, 스마트폰에서는 기본적으로 위성항법 칩셋이 내장되어 사용자 위치를 제공하고 있다. 이렇듯 다양한 분야에서 활용되는 위성항법 수신 칩셋 또는 수신 시스템의 기능 및 성능을 다양한 환경에서 검증할 필요성이 대두되고 있다. 본고에서는 다양한 검증 환경을 제공할 수 있는 위성항법 신호생성기의 국외기술 동향을 살펴보고, 미래부 출연사업인 GNSS 전파교란 검증플랫폼 과제를 통해 개발된 GNSS 전파혼신 신호발생장치에서 확보한 실제 GPS 신호와 동기를 유지한 신호생성기술 개발 현황을 소개한다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.12A
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• pp.1120-1135
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• 2005

In this paper, We have design and implement the network synchronization module for NG-SDH system having 120 Gbps capacity. and also evaluate the performance of it. We also propose analyzing algorithm clock characterisrics on NG-SDH node clock based on the evaluation results.

• Journal of the Korean Institute of Telematics and Electronics
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• v.21 no.6
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• pp.105-114
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• 1984

A fast pseudo-noise (PN) sequence acquisition algorithm for the direct-sequence (DS) spread spectrum system is proposed. The basic concept of the algorithm has been adopted from that of the classical sliding correlator. Mathematical modeling, analysis and computer simulation of the proposed system have been done. The results of analysis and computer simulation show that the acquisition system yields a significant performance improvement over the sliding correlator. Its acquisition time takes only 45 ms when signal-to-noise ratio(SNR) is -18dB. The algorithm developed has been implemented in hardware and its experimental result is also given.