• Title/Summary/Keyword: Time synchronization

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An Efficient symbol Synchronization Scheme with an Interpolator for Receiving in OFDM (OFDM 방식의 수신기를 위한 보간기의 효율적인 심볼 동기방법의 성능분석)

  • 김동옥;윤종호
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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    • pp.574-577
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    • 2002
  • In this paper, we propose a new symbol time synchronization scheme suitable for the OFDM system with an interpolator. The proposed performs the following three steps. In the first step, the coarse symbol time synchronization is achieved by continuously measuring the average power of the received envelope signal. Based on this average power, the detection possibility for the symbol time synchronization is determined. If the signal is sufficient for synchronization, we next perform a relatively accurate symbol time synchronization by measuring the correlation a short training signal and the received envelope signal. Finally, an additional frequency synchronization is performed with a long training signal to correct symbol synchronization errors caused by the phase rotation. From the simulation results, one can see that the proposed synchronization scheme provides a good synchronization performance over frequency selective channels.

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A Study on Implementation of IRIG-B Protocol for Time Synchronization of IEC 61850 based Merging Unit (IEC 61850 기반 병합단위장치의 시간 동기화를 위한 IRIG-B 프로토콜 구현에 관한 연구)

  • Kim, Gwan-Su;Lee, Hong-Hee;Kim, Byung-Jin
    • The Transactions of the Korean Institute of Power Electronics
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    • v.13 no.4
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    • pp.303-310
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    • 2008
  • Recently, IEC 61850 supports the standardized communication technique in both station bus and process bus, and presents substation automation model. In order to implement the IEC 61850 based communication in a substation using the MU (merging unit) which is one of the important data acquisition equipments in substation automation, the time synchronization is demanded for cooperative operation between the devices. This paper proposes the precision time synchronization technique using IRIG-B protocol to develop the MU under IEC 61850 communication protocol. The proposed technique is implemented and its performance is verified experimentally.

A Study on the Construction of Ground Test Segment for the Time Synchronization System Using the Geostationary Satellite (정지궤도 위성을 이용한 시각동기 지상시스템 시험장비 구축에 관한 연구)

  • Lee, Sang-Cherl;Kim, Bang-Yeop
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.32 no.5
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    • pp.104-108
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    • 2004
  • The most of the CDMA mobile communication depends on the GPS for the time synchronization. Then, we must prepare alternative system against the unusable GPS like a unexpectable accident or strategic purpose by the USA government. In this study, we have constructed ground test segment for the time synchronization system using the geostationary satellite. In addition. we have designed, manufactured and tested the transmitting and receiving board to receive 1 PPS signal from atomic clock for transmitting stored data in buffer to satellite modem and to produce 1 PPS signal from satellite modem for measuring time delay.

Forensic Investigation Procedure for Real-time Synchronization Service (실시간 동기화 서비스에 대한 포렌식 조사 절차에 관한 연구)

  • Lee, Jeehee;Jung, Hyunji;Lee, Sangjin
    • Journal of the Korea Institute of Information Security & Cryptology
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    • v.22 no.6
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    • pp.1363-1374
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    • 2012
  • The number and use of Internet connected devices has dramatically increased in the last several years. Therefore many services synchronizing data in real-time is increasing such as mail, calendar and storage service. This service provides convenience to users. However, after devices are seized, the data could be changed because of characteristic about real-time synchronization. Therefore digital investigation could be difficult by this service. This work investigates the traces on each local device and proposes a method for the preservation of real-time synchronized data. Based on these, we propose the procedures of real-time synchronization data.

Global Time Synchronization for Wireless Sensor Networks (무선 센서 네트워크를 위한 전역 시각 동기 기법)

  • Hwang, So-Young;Yu, Don-Hui;Joo, Jae-Heum;Won, Sung-Hyun
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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    • pp.84-86
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    • 2010
  • Time information and time synchronization are fundamental building blocks in wireless sensor networks since many sensor network applications need time information for object tracking, consistent state updates, duplicate detection and temporal order delivery. Various time synchronization protocols have been proposed for sensor networks because of the characteristics of sensor networks which have limited computing power and resources. However, none of these protocols have been designed with time representation scheme in mind. Global time format such as UTC TOD (Universal Time Coordinated, Time Of Day) is very useful in sensor network applications. In this paper we propose time keeping and synchronization method for global time presentation in wireless sensor networks.

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Low Power Time Synchronization for Wireless Sensor Networks Using Density-Driven Scheduling

  • Lim, HoChul;Kim, HyungWon
    • Journal of information and communication convergence engineering
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    • v.16 no.2
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    • pp.84-92
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    • 2018
  • For large wireless sensor networks running on battery power, the time synchronization of all sensor nodes is becoming a crucial task for waking up sensor nodes with exact timing and controlling transmission and reception timing. However, as network size increases, this synchronization process tends to require long processing time consume significant power. Furthermore, a naïve synchronization scheduler may leave some nodes unsynchronized. This paper proposes a power-efficient scheduling algorithm for time synchronization utilizing the notion of density, which is defined by the number of neighboring nodes within wireless range. The proposed scheduling algorithm elects a sequence of minimal reference nodes that can complete the synchronization with the smallest possible number of hops and lowest possible power consumption. Additionally, it ensures coverage of all sensor nodes utilizing a two-pass synchronization scheduling process. We implemented the proposed synchronization algorithm in a network simulator. Extensive simulation results demonstrate that the proposed algorithm can reduce the power consumption required for the periodic synchronization process by up to 40% for large sensor networks compared to a simplistic multi-hop synchronization method.

Time Synchronization over SpaceWire Network using Hop Count Information (홉 카운트 정보를 이용한 스페이스와이어 네트워크 시각동기화 방안)

  • Ryu, Sang-Moon
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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    • pp.715-718
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    • 2016
  • SpaceWire invented for on-board data handling in a spacecraft has Time-Code defined for time synchronization over SpaceWire network. Delay and jitter of the transmission of Time-Code caused when a Time-Code travels through a network are the main reasons of time synchronization error. This work proposes a scheme that can reduce the time synchronization error by using extended Time-Codes. The proposed scheme can remove both transmission jitter and transmission delay. The scheme will be validated in a simulation environment built with OMNeT++.

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원격지의 시각동기를 위한 일반적인 방법에 대한 고찰

  • Kim, Bang-Yeop;Lee, Sang-Cherl
    • Aerospace Engineering and Technology
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    • v.2 no.1
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    • pp.98-107
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    • 2003
  • In this study, a survey of time synchronization methods between the remote places. Generally, there are many kinds of time synchronization methods for distant places and they can be grouped three categories according to the type of time transfer methods. The three methods are ground based network, GPS/NAVSTAR and geostationary satellite. Especially, the relay base stations for wireless digital communication are operated based on the timing signal service of the GPS/NAVSTAR satellite network. And as the back-up of the timing signal service of the GPS/NAVSTAR, the geostationary satellite based time synchronization method have researched. In this short paper, the brief explanations about each category were presented.

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Design of Performance Monitoring System for eLoran Time Synchronization Service (eLoran 시각동기 성능 모니터링 시스템 설계)

  • Seo, Kiyeol;Son, Pyo-Woong;Han, Younghoon;Park, Sang-Hyun;Lee, Jong-Cheol
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.27 no.6
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    • pp.815-821
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    • 2021
  • This study addresses on the design of performance monitoring system for the time synchronization service of the enhanced long-range navigation (eLoran) system, which has a representative ground-wave radio broadcast system capable of providing positioning, navigation, timing and data (PNT&D) services. The limitations of time-synchronized systems due to the signal vulnerabilities of the global navigation satellite system (GNSS) are explained, and the performance monitoring system for the eLoran timing service as a backup to the GNSS is proposed. The time synchronization service using eLoran system as well as system configurations and the user requirements in the differential Loran (dLoran) system are described to monitor the time synchronization performance. The results of the designed system are presented for long-term operation in the eLoran testbed environment. As the results of time performance monitoring, we were able to verify the time synchronization precision within 43.71 ns without corrections, 22.52 ns with corrections. Based on these results, the eLoran system can be utilized as a precise time synchronization source for GPS timing backup.

Design and Evaluation of PMU Performance Measurement and GPS Monitoring System for Power Grid Stabilization

  • Yang, Sung-Hoon;Lee, Chang Bok;Lee, Young Kyu;Lee, Jong Koo
    • Journal of Positioning, Navigation, and Timing
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    • v.4 no.2
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    • pp.67-72
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    • 2015
  • Power grid techniques are distributed over general power systems ranging from power stations to power transmission, power distribution, and users. To monitor and control the elements and performance of a power system in real time in the extensive area of power generation, power transmission, wide-area monitoring (WAM) and control techniques are required (Sattinger et al. 2007). Also, to efficiently operate a power grid, integrated techniques of information and communication technology are required for the application of communication network and relevant equipment, computing, and system control software. WAM should make a precise power grid measurement of more than once per cycle by time synchronization using GPS. By collecting the measurement values of a power grid from substations located at faraway regions through remote communication, the current status of the entire power grid system can be examined. However, for GPS that is used in general national industries, unexpected dangerous situations have occurred due to its deterioration and jamming. Currently, the power grid is based on a synchronization system using GPS. Thus, interruption of the time synchronization system of the power system due to the failure or abnormal condition of GPS would have enormous effects on each field such as economy, security, and the lives of the public due to the destruction of the synchronization system of the national power grid. Developed countries have an emergency substitute system in preparation for this abnormal situation of GPS. Therefore, in Korea, a system that is used to prepare for the interruption of GPS reception should also be established on a long-term basis; but prior to this, it is required that an evaluation technique for the time synchronization performance of a GPS receiver using an atomic clock within the power grid. In this study, a monitoring system of time synchronization based on GPS at a power grid was implemented, and the results were presented.