Special Issue Article
TSROD: Time Synchronization By Reducing Ocean¬ís Delay In Underwater Wireless Networks
|Ms.R.Vaishnavi karthika1, Mr.M.N.Karuppusamy2
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Underwater wireless sensor networks (UWSNs) is essential for an investigators. It requires time synchronization service or a lot of applications. However, in order to do time synchronization in UWSNs, three issues have to be considered. A first, acoustic channel features long propagation delays, which make the conventional two-way delay measurements quite inefficient and inaccurate. Second, since all nodes change continuously with water currents, underwater networks are a highly dynamic network, which makes the synchronization protocols for static networks are not suitable here. Last but not the least, the underwater nodes are usually charged by power unit, for which it is hard (if not impossible) to get replaced. Synchronization protocols which need frequent message exchanges do not fit here. A new brand time synchronization algorithm, TSROD is specifically designed for mobile UWSNs. In TSROD, the spatial correlation of the sensor node mobility is effectively employed to improve the accuracy of the estimation of the fast-changing long propagation delay. In addition, the ratio of valid reference messages is much higher than other synchronization protocols, which makes TSROD quite energy efficient. Furthermore, with multiple runs of linear regression as well as the calibration process, both skew and offset is well estimated and compensated. To handle time synchronization error, kalman filter or averaging filter estimate the unknown variable means target location in underwater containing random error which greatly increases the accuracy of the time synchronization algorithm.