• Title/Summary/Keyword: Time synchronization

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A Design of Dual Frequency Bands Time Synchronization System for Synchronized-Pseudolite Navigation System

  • Seo, Seungwoo;Park, Junpyo;Suk, Jin-Young;Song, Kiwon
    • Journal of Positioning, Navigation, and Timing
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    • v.3 no.2
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    • pp.71-81
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    • 2014
  • Time synchronization system using dual frequency bands is designed and the error sources are analyzed for alternative synchronized-pseudolite navigation system (S-PNS) which aims at military application. To resolve near/far problem, dual frequency band operation is proposed instead of pulsing transmission which degrades level of reception. In dual frequency operation H/W delay should be considered to eliminate errors caused by inter-frequency bias (IFB) difference between the receivers of the pseudolites and users. When time synchronization is performed across the sea, multipath error is occurred severely since the elevation angle between pseudolites is low so total reflection can be happened. To investigate the difference of multipath effects according to location, pseudolites are set up coastal area and land area and performances are compared. The error source related with tropospheric delay is becoming dominant source as the coverage of the PNS is broadening. The tropospheric delay is measured by master pseudolite receiver directly using own pseudorange and slave pseudorange. Flight test is performed near coastal area using S-PNS equipped with developed time synchronization system and test results are also presented.

Skew Compensation Algorithm for Time Synchronization in Wireless Sensor Networks (무선 센서 네트워크 시간 동기화에 대한 왜곡 보정 알고리즘)

  • Kumar, Shiu;Keshav, Tushar;Jo, Dong Hyeon;Kim, Hui;Lee, Jae Yeong;Jeon, Hye Ji;Jeong, Min A;Lee, Seong-Ro
    • Proceedings of the Korea Information Processing Society Conference
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    • 2013.05a
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    • pp.495-497
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    • 2013
  • Wireless sensor networks (WSNs) have emerged as an attractive and key research area over the last decade. Time synchronization is a vital part of infrastructure for any distributed system. In embedded sensor networks, time synchronization is an essential service for correlating data among nodes and communication scheduling. This is realized by exchanging messages that are time stamped using the local clocks on the nodes. Various time synchronization protocols have been proposed aiming to attain high synchronization accuracy, high efficiency and low communication overhead. However, it requires that the time between resynchronization intervals to be as large as possible to obtain a system which is energy efficient having low communication overhead. This paper presents a simple but effective skew compensation algorithm that measures the skew rate of the sensor nodes with respect to the reference node and calibrates itself to compensate for the difference in the frequencies of the nodes. The proposed method can be incorporated with any existing time synchronization protocol for WSNs.

Time Synchnorinization Scheme for Multi-Hop Wireless Sensor Network (다중 홉 무선 센서네트워크를 위한 시간 동기화 기법)

  • Kim, Gi-Hyeon;Eom, Tae-Hwan;Hong, Won-Kee
    • IEMEK Journal of Embedded Systems and Applications
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    • v.2 no.3
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    • pp.138-144
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    • 2007
  • Wireless Sensor Network(WSN) consists of a lot of light-weight sensor nodes with the capability of wireless communication. Studies have been done to improve stability and fault-tolerancy of WSN because the sensor nodes are basically vulnerable to the harsh environment. Specially, the time synchronization among sensor nodes becomes a challenging issue in WSN. All the local times should always keep the same with each other in the sensor field to perform data aggregation and energy-aware communication in WSN. In this paper, a new time synchronization technique is proposed to operate efficiently irrespective of the number of sensor nodes and the number of hops needed to cover all sensor nodes for synchronization. Simulation results show that the proposed technique has the lowest amount of packet traffic among the several time synchronization techniques.

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An Energy Efficient Time Synchronization Technique Based on WUSB over WBAN Protocol for Wearable Computer Systems (웨어러블 컴퓨터 시스템을 위한 WUSB over WBAN 프로토콜의 에너지 효율적인 시간 동기 기술)

  • Hur, Kyeong;Sohn, Won-Sung
    • Journal of Korea Multimedia Society
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    • v.15 no.7
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    • pp.879-884
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    • 2012
  • In this Paper, we propose an Energy Efficient Time Synchronization technique based on WUSB (Wireless USB) over WBAN (Wireless Body Area Networks) protocol required for Wearable Computer systems. For this purpose, the proposed Time Synchronization algorithm minimizes power consumption and estimates time information with accuracy. It is executed on the basis of WUSB over WBAN protocol at each sensor node comprising peripherals of a wearable computer system. It minimizes power consumption by exchanging time stamp packets and forming a hierarchical structure.

Time Synchronization Performance Improvement based on PN sequence for Advanced T-DMB system (PN 시퀀스 기반 Advanced T-DMB 시간 동기 방법)

  • Bae, Jae-Hwui;Kim, Young-Su;Lim, Jong-Soo;Song, Yun-Jeong;Lee, Soo-In;Han, Dong-Seog
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.35 no.4B
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    • pp.670-676
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    • 2010
  • A time synchronization method for Advanced T-DMB is proposed using PN sequence inserted in PRS for the transmission of hierarchical modulation mode information. The time synchronization offset is estimated through the cross-correlation of the PN sequence and the received PRS. The performance of the proposed method is analyzed by the BER analysis in mobile channel and the results are shown.

An Optimized Time-synchronization Method for Simulator Interworking

  • Kwon, Jaewoo;Kim, Jingyu;Woo, Sang Hyo Arman
    • Journal of Korea Multimedia Society
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    • v.22 no.8
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    • pp.887-896
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    • 2019
  • In this paper, we discuss an optimization approach for time-synchronizations in networked simulators. This method is a sub-technology that is required to combine heterogeneous simulators into a single simulation. In previous time-synchronization studies, they had built a network system among networked simulators. The network system collects network packets and adds time-stamps to the networked packets based on the time that occurs in events of simulation objects in the individual simulators. Then, it sorts them in chronological order. Finally, the network system applies time-synchronization to each simulator participating in interworking sequentially. However, the previous approaches have a limitation in that other participating simulators should wait for while processing an event in a simulator in a time stamp order. In this paper, we attempt to solve the problem by optimizing time-synchronizations in networked simulation environments. In order to prove the practicality of our approach, we have conducted an experiment. Finally, we discuss the contributions of this paper.

Precision Time Synchronization System over Wireless Networks for TDOA-based Real Time Locating Systems (TDOA 기반의 실시간 위치 측정 시스템을 위한 정밀 무선 시각 동기 시스템)

  • Cho, Hyun-Tae;Jung, Yeon-Su;Jang, Hyun-Sung;Park, In-Gu;Baek, Yun-Ju
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.34 no.1B
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    • pp.86-97
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    • 2009
  • RTLS is a system for automatically locating and tracking people and objects. The TDOA-based RTLS determines the location of the tag by calculating the time differences of a signal received from the tag. In TDOA-based RTLS, time synchronization is essential to calculate the time difference between readers. This paper presents a precision time synchronization method for TDOA-based RTLS over IEEE 802.15.4. In order to achieve precision time synchronization in IEEE 802.15.4 radio, we analyzed the error factors of delay and jitter. We also deal with the implementation of hardware assisted time stamping and the Kalman filtering method to minimize the error factors. In addition, this paper described the experiments and performance evaluation of the proposed precision time synchronization method in IEEE 802.15.4 radio. The results show that the nodes in a network can maintain their clocks to within 10 nanoseconds offset from the reference clock.

A Survey of Time Synchronization Techniques in Underwater Acoustic Networks (수중 음향 네트워크를 위한 시간 동기화 기술 동향 분석에 대한 연구)

  • Cho, A-Ra;Yun, Changho;Lim, Yong-Kon
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.39C no.3
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    • pp.264-274
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    • 2014
  • Time synchronization becomes a critical issue in underwater acoustic networks (UANets) because nodes cooperate together or individually work by communicating each other in diverse underwater applications. Compared with the time synchronization approaches in terrestrial networks, several intrinsic limitations of UANets (e.g., the unavailability of GPS, long propagation delay, mobility due to currents, limited energy consumption, or low data rate) need to be considered in synchronizing the timing among underwater nodes. For the purpose of developing more efficient time synchronization protocols for UANets, we review the existing approaches, which estimate both the clock offset and the clock skew of underwater nodes. Finally, we outline the state-of-the art time synchronization protocols for UANets by comparing and summarizing them according to their synchronization characteristics.

A Time Synchronization Algorithm for a Time-Slot Reservation Based MAC in Mobile Ad-Hoc Networks (모바일 애드혹 네트워크에서 MAC 기반 타임 슬롯 예약을 위한 시간 동기화 알고리즘)

  • Heo, Ung;He, Yushan;You, Kang-Soo;Choi, Jae-Ho
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.48 no.4
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    • pp.37-46
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    • 2011
  • Time synchronization plays an important role in mobile communication systems, particularly, when an accurate time-division mechanism among the communication entities is required. We present a new time synchronization algorithm for a wireless mobile ad-hoc network assuming that communication link is managed by a time-slot reservation-based medium access control protocol. The central idea is to reduce time synchronization packet collisions by exploiting the advantages found in reference broadcasting. In addition, we adopt a sophisticated clock updating scheme to ensure the time synchronization convergence. To verify the performance of our algorithm, a set of network simulations has been performed under various mobile ad-hoc network scenarios using the OPNET. The results obtained from the simulations show that the proposed method outperforms the conventional TSF method in terms of synchronization accuracy and convergence time.

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.