• Title/Summary/Keyword: Time synchronization

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A Distributed Time Synchronization Technique for OFDMA-based Wireless Mesh Communication Systems Using Bio-inspired Algorithm (생체모방 알고리즘을 이용한 OFDMA 무선 메쉬 통신시스템의 분산 시간 동기화 기법 연구)

  • Kim, Mi-Jeong;Lee, Yun-Jae;Cho, Yong-Soo
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.38A no.12
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    • pp.1069-1078
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    • 2013
  • In this paper, we propose a distributed time synchronization technique for OFDMA- based wireless mesh communication systems. The proposed technique employs the bio-inspired algorithm for self-time synchronization in the physical layer. To achieve the network synchronicity, the proposed technique updates the transmission time and the FFT window using the TDoA information of received signals from the neighbor nodes. The proposed technique can achieve fast self-synchronization among nodes with a simple algorithm, without the need of a centralized controller. The performance of the proposed time synchronization technique is evaluated by simulation in terms of convergence speed and convergence probability.

Method of Master Receiver Selection Using DOP for Time Synchronization in TDOA-Based Localization (TDOA 기반 위치탐지를 위한 DOP을 이용한 시각동기화 주수신기 선택 기법)

  • Kim, Sanhae;Song, Kyuha;Kwak, Hyungyu
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.41 no.9
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    • pp.1069-1080
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    • 2016
  • TDOA(Time Difference Of Arrival)-based localization system such as the passive surveillance system performs the time synchronization between the receivers after separated installing multiple receivers to set the same clock for all receivers. And it estimates 2D(or 3D) location of the target by solving intersection of the multiple hyperbola(or hyperboloid) using TDOA. To perform time synchronization, one receiver must be set to the master, and it provide the reference data to compensate the clock of the rest of the slaves. The positioning accuracy of TDOA-based localization system is changed in accordance with the master that is selected among multiple receivers. So, the optimum receiver which is selected among multiple receivers must be set to master to get best performance in the considered deployment of receivers. In this paper, we propose a selection scheme of master receiver for time synchronization using DOP(Dilution Of Precision) which is based on location of the target and the multiple receivers. The proposed scheme has low complexity and short processing time, and it is easy to automate in the TDOA-based localization systems.

The Time Synchronization Signals of the GNSS Receiver for KSLV-II and Their Performance Assessment (한국형발사체 위성항법수신기의 시각동기신호 생성 및 성능 평가)

  • Kwon, Byung-Moon;Shin, Yong-Sul;Ma, Keun-Su;Yun, Kwang-Ho;Seo, Hung-Seok
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.47 no.11
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    • pp.812-820
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    • 2019
  • The GNSS receiver for KSLV(Korea Space Launch Vehicle)-II provides real-time navigation data as well as precise time and time interval. The precise time signals provided by the GNSS receiver that can be used for the time synchronization between onboard systems, and between the onboard systems and ground stations have the forms of the 1PPS(One Pulse Per Second) and IRIG-B(Inter-Range Instrumentation Group Time Code B) which are synchronized with UTC(Coordinated Universal Time). A signal for timing faults also informs whether the time synchronization signals are available or not. This paper describes the time synchronization signals of the GNSS receiver for KSLV-II and their performance assessment.

Recursive Time Synchronization Method Based on GPIO Signal Delay Compensation and EMA Filter (GPIO EMA 신호 지연 보상 및 필터 기반 재귀적 시간 동기화 기법)

  • Kwon, Young-Woo;Nam, Ki Gon;Choi, Joon-Young
    • IEMEK Journal of Embedded Systems and Applications
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    • v.15 no.1
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    • pp.17-23
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    • 2020
  • We propose a system time synchronization method between embedded Linux-based distributed control devices by using Transmission Control Protocol (TCP) communication and General Purpose Input Output (GPIO) device. The GPIO signal is used as the trigger signal for synchronization and the TCP communication is used to transfer the system time of master Linux, which serves as the reference clock, to slave Linux. Precise synchronization performance is achieved by measuring and compensating for the propagation delay of GPIO signal and the acquisition and setting latency of Linux system time. We build an experimental setup consisting of two embedded Linux systems, and perform extensive experiments to verify the performance of the proposed synchronization method.

Improvement of Time Synchronization over Space Wire Link (스페이스와이어 링크의 시각 동기 성능 개선)

  • Ryu, Sang-Moon
    • Journal of Institute of Control, Robotics and Systems
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    • v.15 no.11
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    • pp.1144-1149
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    • 2009
  • This paper deals with the time synchronization problem over SpaceWire links. SpaceWire is a standard for high-speed links and networks between spacecraft components, which was invented for better, cheaper, faster on-board data handling in spacecraft. The standard defines Time-Code for time distribution over SpaceWire network. When a Time-Code is transmitted, transmission delay and jitter is unavoidable. In this paper, a mechanism to remove Time-Code transmission delay and jitter over SpaceWire links is proposed and implemented with FPGA for validation. The proposed mechanism achieves high resolution clock synchronization over SpaceWire links, complies with the standard and can be easily adopted over SpaceWire network.

LEO Satellite Time Synchronization Architecture

  • Kwon, Ki-Ho;Kim, Day-Young;Lee, Jong-In;Kim, Hak-Jung;Lee, Sang-Jeong
    • Proceedings of the Korean Institute of Navigation and Port Research Conference
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    • v.1
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    • pp.367-370
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    • 2006
  • A GPS-based time synchronization technique employing a refined HW circuitry and SW algorithm is considered as fine time-management system for Low Earth Orbit (LEO) remote sensing satellites. By synchronizing the On-Board Time (OBT) within satellites to the GPS 1PPS, a very expensive, highly accurate on-board clock is not required to determine the precise on-board time management. Also, the satellite command generation in ground stations and postprocessing of earth observation data which a particular image is acquired. This paper analyses on-orbit verification of the existing satellite time sync architecture and presents a new time sync architecture, operation and relation between the OBT and the GPS time.

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Issues in structural health monitoring employing smart sensors

  • Nagayama, T.;Sim, S.H.;Miyamori, Y.;Spencer, B.F. Jr.
    • Smart Structures and Systems
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    • v.3 no.3
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    • pp.299-320
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    • 2007
  • Smart sensors densely distributed over structures can provide rich information for structural monitoring using their onboard wireless communication and computational capabilities. However, issues such as time synchronization error, data loss, and dealing with large amounts of harvested data have limited the implementation of full-fledged systems. Limited network resources (e.g. battery power, storage space, bandwidth, etc.) make these issues quite challenging. This paper first investigates the effects of time synchronization error and data loss, aiming to clarify requirements on synchronization accuracy and communication reliability in SHM applications. Coordinated computing is then examined as a way to manage large amounts of data.

CoAP-based Time Synchronization Algorithm in Sensor Network (센서 네트워크에서의 CoAP 기반 시각 동기화 기법)

  • Kim, Nac-Woo;Son, Seung-Chul;Park, Il-Kyun;Yu, Hong-Yeon;Lee, Byung-Tak
    • Journal of the Institute of Electronics and Information Engineers
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    • v.52 no.3
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    • pp.39-47
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    • 2015
  • In this paper, we propose a new time synchronization algorithm using CoAP(constrained-application protocol) in sensor network environment, which handles a technique that synchronizes an explicit timestamp between sensor nodes not including an additional module for time-setting and sensor node gateway linked to internet time server. CoAP is a standard protocol for sensor data communication among sensor nodes and sensor node gateway to be built much less memory and power supply in constrained network surroundings including serious network jitter, packet losses, etc. We have supplied an exact time synchronization implementation among small and cheap IP-based sensor nodes or non-IP based sensor nodes and sensor node gateway in sensor network using CoAP message header's option extension. On behalf of conventional network time synchronization method, as our approach uses an exclusive protocol 'CoAP' in sensor network, it is not to become an additional burden for synchronization service to sensor nodes or sensor node gateway. This method has an average error about 2ms comparing to NTP service and offers a low-cost and robust network time synchronization algorithm.

A Study of High-Precision Time-Synchronization for TDoA-Based Location Estimation (TDoA 기반의 위치 추정을 위한 초정밀 시각동기에 관한 연구)

  • Kim, Jae Wan;Eom, Doo Seop
    • KIPS Transactions on Computer and Communication Systems
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    • v.2 no.1
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    • pp.7-14
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    • 2013
  • Presently, there are many different technologies used for position detection. However, as signal-receiving devices operating in different locations must detect the precise position of objects located at long distances, it is essential to know the precise time at which an object's or a user's terminal device sends a signal. For this purpose, the existing time of arrival (ToA) technology is not sufficiently reliable, and the existing time difference of arrival (TDoA) technology is more suitable. If a TDoA-based electric surveillance system and other tracking devices fail to achieve precise time-synchronization between devices with separation distance operation, it is impossible to obtain correct TDoA values from the signals sent by the signal-receiving devices; this failure to obtain the correct values directly affects the location estimation error. For this reason, the technology for achieving precise time synchronization between signal-receiving devices in separation distance operation, among the technologies previously mentioned, is a core technology for detecting TDoA-based locations. In this paper, the accuracy of the proposed time synchronization and the measurement error in the TDoA-based location detection technology is evaluated. The TDoA-based location measurement error is significantly improved when using the proposed method for time-synchronization error reduction.

A comparison of Coarse Time Synchronization Algorithms for OFDM system (OFDM 시스템을 위한 여러 가지 거친 시간 동기검출 방식의 비교)

  • Son, Seung-Ho;Kim, Joon-Tae
    • Proceedings of the IEEK Conference
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    • 2007.07a
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    • pp.123-124
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    • 2007
  • In this paper a comparison of several coarse time synchronization(CTS) algorithms for OFDM is presented. The goal of a CTS is to achieve a timing estimate that avoids IST in the receiver. Five coarse timing estimation algorithms are examined and their performances are compared associated with hardware complexity. Simulations has been performed for DVB-T 2K system in thee different channels.

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