MU-Sync: a time synchronization protocol for underwater mobile networks
MU-Sync: a time synchronization protocol for underwater mobile networks
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DOI：
10.1145/1410107.1410115
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发表时间：
2008-09
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影响因子：
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通讯作者：
N. Chirdchoo;Wee-Seng Soh;K. Chua
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文献类型：
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作者：
N. Chirdchoo;Wee-Seng Soh;K. Chua
虽然目前已经提出了许多适用于陆地无线传感器网络的时间同步算法，但是这些算法都不能直接应用于水声传感器网络。这是因为他们通常假设传播延迟可以忽略不计，而水下的情况并非如此。此外，水下传感器节点往往具有一定程度的移动性，由于风或洋流，这通过引入时变延迟使问题更加复杂。本文提出了一种基于分簇的水声移动的网络同步算法MU-Sync。我们的设计避免了频繁的重新同步估计时钟偏差和偏移。由于水下移动的网络经历时变和长的传播延迟，以前的作品，估计使用一个单一的最小二乘误差线性回归的时钟偏差往往是不准确的。在MU-Sync中，通过对通过消息交换收集的一组本地时间信息执行两次线性回归来估计时钟偏差。第一个线性回归使簇头能够抵消长且变化的传播延迟的影响;第二个回归进而获得估计的偏斜和偏移。在MAC级时间戳的帮助下，我们可以进一步减少那些依赖于消息交换的同步算法通常会遇到的不确定性错误。
Although there are numerous time synchronization algorithms recently proposed for terrestrial wireless sensor networks, none of these could be directly applied to underwater acoustic sensor networks. This is because they typically assume that the propagation delay is negligible, which is not the case in underwater. Furthermore, the sensor nodes in underwater tend to have some degree of mobility due to wind or ocean current, which complicates the problem even more by introducing time-varying delay. In this paper, we propose a cluster-based synchronization algorithm for underwater acoustic mobile networks, called "MU-Sync". Our design avoids frequent re-synchronization by estimating both the clock skew and offset. As underwater mobile networks experience both time-varying and long propagation delay, previous works that estimate the clock skew using a single least square error linear regression tend to be inaccurate. In the MU-Sync, the clock skew is estimated by performing the linear regression twice over a set of local time information gathered through message exchanges. The first linear regression enables the cluster head to offset the effect of long and varying propagation delay; the second regression in turn obtains the estimated skew and offset. With the help of MAC-level time stamping, we can further reduce the nondeterministic errors that are commonly encountered by those synchronization algorithms that rely on message exchanges.