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DOI:
Journal of Software:2009.20(zk):266-277

线性传感器网络时间同步协议
徐朝农,徐勇军,邓志东
(清华大学 智能技术与系统国家重点实验室,北京 100084;中国科学院 计算技术研究所,北京 100190)
Timing-Sync Protocol for Linear Sensor Networks
XU Chao-Nong,XU Yong-Jun,DENG Zhi-Dong
()
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Received:May 01, 2009    Revised:July 23, 2009
> 中文摘要: 由于存在着高同步误差和高功耗的特点,尤其当网络拓扑为多跳线状时,经典的双向报文交换同步机制不适合于无线传感器网络中的一些应用.提出了TPLSN时间同步协议.两个组件,包括:改进的双向报文交换同步机制和时钟飘移补偿机制是TPLSN成功之关键.进一步讨论了TPLSN同步误差随跳数增长的现象.在一个与Mica2兼容的测试床上对TPLSN进行了性能评估.距离时间基准节点9跳的节点的同步误差小于20μs,同步误差随跳数的增长率小于1μs/跳,同步误差随重同步周期的增长率为0.017μs/s.此外,同步一个n跳的线状网络只需要2n个报文,这也是所有基于双向报文交换同步机制的同步协议最小所需的报文数.理论分析表明:近似精度、双向报文交换的不对称性和相对时钟飘移因素对两个相邻节点之间的同步误差有很大的影响.进而,线状网络的时钟序对同步误差的累积至关重要.
Abstract:Due to the features of high synchronization error and high power consumption, the classic synchronization scheme of two-way packets exchange is unfit for some applications in wireless sensor networks, especially for networks with multi-hop linear topology. This paper proposes a time synchronization protocol named Timing-sync Protocol for Linear Sensor Networks (TPLSN). The synchronization scheme of enhanced two-way packets exchange and the scheme of clock skew compensation are keys to the success of TPLSN. The phenomenon of its synchronization error accumulation over hop count is also investigated. TPLSN is evaluated on a Mica2-compatible test bed. Its synchronization error is less than 20μs for the node which is 9 hops away from the time beacon node, the increase ratio of synchronization error to hop count is less than 1μs per hop, and the increase ratio of synchronization error to resynchronization cycle is 0.017μs per second. Further, to synchronize all nodes in an n-hop linear wireless sensor network, only 2n packets are needed, which is least for any synchronization protocol based on synchronization scheme of two-way packet exchange. Theoretical analysis shows that three factors, including the approximated accuracy, the asymmetry of two-way packets exchange, and the clock skew, have great influences on time offset between two adjacent nodes. Furthermore, the clock frequency order of the linear network is found to be vital to the accumulation of synchronization error over hop count.
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基金项目:Supported by the National Natural Science Foundation of China under Grant Nos.90820305, 60621062, 60772070 (国家自然科学基金); the National High-Tech Research and Development Plan of China under Grant Nos.2007AA041702, 2009AA01Z126 (国家高技术研究发展计划(863)); the China P Supported by the National Natural Science Foundation of China under Grant Nos.90820305, 60621062, 60772070 (国家自然科学基金); the National High-Tech Research and Development Plan of China under Grant Nos.2007AA041702, 2009AA01Z126 (国家高技术研究发展计划(863)); the China P
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徐朝农,徐勇军,邓志东.线性传感器网络时间同步协议.软件学报,2009,20(zk):266-277

XU Chao-Nong,XU Yong-Jun,DENG Zhi-Dong.Timing-Sync Protocol for Linear Sensor Networks.Journal of Software,2009,20(zk):266-277