• Title/Summary/Keyword: Time synchronization

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Design of Time Synchronization Mechanism of Wireless USB over IEEE 802.15.6 (WUSB over IEEE 802.15.6 WBAN 프로토콜의 시각 동기 구조 설계)

  • Hur, Kyeong
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.18 no.7
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    • pp.1619-1627
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    • 2014
  • Wearable computer systems can use the wireless universal serial bus (WUSB) that refers to USB technology that is merged with WiMedia PHY/MAC technical specifications. In this paper, we focus on an integrated system of the wireless USB over the IEEE 802.15.6 wireless body area networks (WBAN) for wireless wearable computer systems supporting U-health services. And a communication structure that performs the time-synchronization is proposed for WUSB over IEEE 802.15.6 hierarchical protocol. Proposed time-synchronization mechanisms adopt the WBAN Polling Access and combine it with a time-synchronization middleware using time stamps. In our performance evaluations, time-synchronization performances with only WBAN Polling Access scheme are analyzed first. After that, performances combined with the time-synchronization middleware are analyzed to evaluate the effectiveness of proposed time-synchronization structure in WUSB over IEEE 802.15.6.

Time Synchronization between IoT Devices in a Private Network using Block-Chain (블록체인을 이용한 사설망에서의 IoT 기기 간 시간 동기화)

  • Ji, Soyeong;Kim, Seungeun;Yun, Eunju;Seo, Dae-Young
    • The Journal of the Institute of Internet, Broadcasting and Communication
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    • v.18 no.5
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    • pp.161-169
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    • 2018
  • This study presents a time synchronization system in decentralized structure by using the blockchain, a core technology of Bitcoin introduced by Satoshi Nakamoto in 2008. In this study, Getting away from existing time synchronization system in centralized structure, A blockchain network has completely decentralized structure using public blockchain. In decentralized structure, Only certain peers among the peers that participate in a blockchain network access the NTP server. Therefore, others can synchronize time without having to go to public network. Furthermore if appropriate time synchronization cycles are established for each peer, time synchronization can be maintained even when connection to public network is completely lost. A time synchronization system in this study has advantages of p2p system and can be also guaranteed reliability and stability because it used digital signature, merkle tree, consensus algorithm which are core characteristics of block chains.

Improvement of Time Synchronization of SpaceWire Network through Time-Code Extension (타임코드 확장을 통한 스페이스와이어 네트워크의 시각 동기화 성능 개선)

  • Ryu, Sang-Moon
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.21 no.4
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    • pp.724-730
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    • 2017
  • SpaceWire invented for spacecrafts has Time-Code defined for time synchronization over SpaceWire network. A Time-Code suffers transmission delay of 14[bit-period] and jitter up to 10[bit-period] whenever it passes through a SpaceWire link, which is the primary cause of time synchronization error. This work presents a simple method to improve the time synchronization which uses two extended Time-Codes. Nodes on a SpaceWire network can find how much delay and jitter a received Time-Code has suffered while it passes through the network, and they can correct time synchronization error with this information. The proposed method was validated in a simulation environment developed based on OMNeT++. The simulation result showed that time synchronization error less than a few bit-periods can be achieved. The proposed method is cost effective and suitable for small-scale SpaceWire network systems.

Time Synchronization with Oceanic Movement Pattern in Underwater Wireless Networks (해수운동의 특성을 활용한 수중 무선 네트워크 시각 동기화)

  • Kim, Sungryul;Park, Seongjin;Yoo, Younghwan
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.38C no.5
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    • pp.486-496
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    • 2013
  • Time synchronization in underwater environment is challenging due to high propagation delay and mobility of sensor nodes. Previous researches do not consider practical issues affecting on the accuracy of time synchronization such as high-channel access delay and relative position between sensor nodes. Also, those protocols using bidirectional message exchange shorten the network lifetime and decrease the network throughput because numerous transmission, reception and unnecessary overhearing can be occurred. Therefore, in our research, we suggest enhanced time synchronization based on features of underwater environment. It controls the instant of transmission by exploiting the feature of an oceanic movement and node deployment. Moreover, the protocol uses more accurate time information by removing channel access delay from the timestamp. The proposed scheme is also practical on the underwater sensor network requiring low-power consumption because the scheme conducts time-synchronization with smaller transmission and reception compared with previous works. Finally, simulation results show that the proposed protocol deceases time error by 2.5ms and 0.56ms compared with TSHL and MU-Sync respectively, reducing energy consumption by 68.4%.

Time Synchronization by Consecutive Broadcast for Wireless Sensor Networks (연속 방송 패킷 전송에 의한 무선 센서 네트워크의 시각 동기화)

  • Bae, Shi-Kyu
    • The KIPS Transactions:PartC
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    • v.19C no.3
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    • pp.209-214
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    • 2012
  • Time synchronization is important role in a network, especially in Wireless Sensor Network (WSN) which is required for time-critical applications such as surveillance, tracking, data fusion and scheduling. Time synchronization in WSN should meet the other different requirements than the one in other networks because WSN has critical resource constraints, especially power consumption. This paper presents a new time synchronization scheme for WSN, which is energy efficient by reducing communication overhead. Simulation test shows this new scheme has better energy efficiency and performance of accuracy than existing schemes proposed previously.

An Energy-efficient Pair-wise Time Synchronization Protocol for Wireless Networks (에너지 효율적인 무선 네트워크용 상호 시각 동기화 프로토콜)

  • Bae, Shi-Kyu
    • Journal of Korea Multimedia Society
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    • v.19 no.10
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    • pp.1808-1815
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    • 2016
  • TPSN(Timing-sync Protocol for Sensor Networks), the representative of time synchronization protocol, has been already developed to provide time synchronization among nodes in wireless sensor networks. Even though the TPSN's method has been referenced by so many other time synchronization schemes for resource-constrained networks like wireless sensor networks or low power personal area networks, it has some inefficiency in terms of power consumption and network-wide synchronization time (or called convergence time). The main reason is that each node in TPSN needs waiting delay to solve the collision problem due to simultaneous transmission among competing nodes, which causes more power consumption and longer network convergence time for a network-wide synchronization. In this paper an improved scheme is proposed by changing message exchange method among nodes. The proposed scheme not only shortens network-wide synchronization time, but also reduce collision traffic which lead to needless power consumption. The proposed scheme's performance has been evaluated and compared with an original scheme by simulation. The results are shown to be better than the original algorithm used in TPSN.

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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    • 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.

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Design and Implementation of Precision Time Synchronization in Wireless Networks Using ZigBee (ZigBee를 이용한 무선 네트워크 환경에서의 정밀 시각 동기 기법 설계 및 구현)

  • Cho, Hyun-Tae;Son, Sang-Hyun;Baek, Yun-Ju
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.33 no.5A
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    • pp.561-570
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    • 2008
  • Time synchronization is essential for a number of network applications such as high speed communication and parallel/distribution processing systems. As the era of ubiquitous computing is ushered in, the high precise time synchronization in wireless networks have been required in. This paper presents the design ana the implementation of the high precision time synchronization in wireless networks using ZigBee. To achieve high precision requirements, we have tried to analyze and reduce error factors such as the latency and jitters of a protocol stack on wireless environments. In addition, this paper includes some experiments and performance evaluations of our system. The result is that we established for nodes in a network to maintain their elects to within a 50 nanosecond offset from the reference clock.

An Internet Time Synchronization Model using Dynamic Linear Model (동적선형모델을 적용한 인터넷 시각동기 모델)

  • Yu, Dong-Hui;Hwang, So-Young;Kim, Yong-Ho
    • The KIPS Transactions:PartC
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    • v.10C no.6
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    • pp.711-716
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    • 2003
  • We propose a new Interet time synchronization model using danamic linear model and introduce the characteristics of internet transmission delays. SNTP(Simple Network Time Protocol) has been widely used as a time synchronization method on the Internet. While SNTP provides a very simple usage, SNTP may not provide the stable services, since SNTP does not consider the several essential error factors. In order to overcome the instabitily of SNTP, we analyze the process of time estimation of SNTP and find the difference between forward transmission delay and backward transmission delay operates the main error on the estimation of an time offset.

EETS : Energy- Efficient Time Synchronization for Wireless Sensor Networks (무선 센서 네트워크에서 에너지 효율성을 고려한 시간 동기 알고리즘)

  • Kim, Soo-Joong;Hong, Sung-Hwa;Eom, Doo-Seop
    • Journal of IKEEE
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    • v.11 no.4
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    • pp.322-330
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    • 2007
  • Recent advances in wireless networks and low-cost, low-power design have led to active research in large-scale networks of small, wireless, low power sensors and actuators, In large-scale networks, lots of timing-synchronization protocols already exist (such as NTP, GPS), In ad-hoc networks, especially wireless sensor networks, it is hard to synchronize all nodes in networks because it has no infrastructure. In addition, sensor nodes have low-power CPU (it cannot perform the complex computation), low batteries, and even they have to have active and inactive section by periods. Therefore, new approach to time synchronization is needed for wireless sensor networks, In this paper, I propose Energy-Efficient Time Synchronization (EETS) protocol providing network-wide time synchronization in wireless sensor networks, The algorithm is organized two phase, In first phase, I make a hierarchical tree with sensor nodes by broadcasting "Level Discovery" packet. In second phase, I synchronize them by exchanging time stamp packets, And I also consider send time, access time and propagation time. I have shown the performance of EETS comparing Timing-sync Protocol for Sensor Networks (TPSN) and Reference Broadcast Synchronization (RBS) about energy efficiency and time synchronization accuracy using NESLsim.

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