A robust time synchronization approach for underwater networks with inconsistent timestamps

Abstract

To achieve time synchronization in underwater networks, a linear regression is often applied over a set of sendingreceiving timestamps, assuming the participating timestamps are consistent. In this paper, we show that collisions, which are not uncommon during signal exchange in underwater environment, would lead to inconsistent timestamps. These inconsistent timestamps are outliers. However, existing synchronization approaches ignore the presence of outliers. To obtain a reliable synchronization, we propose a robust algorithm that identifies and eliminates the outliers by employing Cook's distance before applying linear regression. We justify the proposed algorithm in a mobile underwater environment through extensive simulations.

BE-Sync: A Bandwidth Efficient Time Synchronization for Underwater Wireless Sensor Networks

“…The simulations run 10,000 times in Python Jupyter Notebook on a machine running Intel i7 2 GHz processor and 16 GB RAM. Root mean square error (RMSE) is estimated for determining the rate at which error grows for RSUN [9] and BE-Sync. As evident from Fig.…”

“…7, NHPP adjusts for it, and packets are sent only when collision probability is low. Hence, error after synchronization is lower as compared to RSUN [9] and MU-Sync [2]. The error in BE-Sync is at least an order of magnitude lower than RSUN when probability of packet collision is low and three orders of magnitude lower than MU-Sync.…”

“…E 2 DTS algorithm is applicable for time synchronization under conditions of node mobility. RSUN [9] or robust synchronization for underwater networks takes packet collision into account which is mostly ignored in time synchronization protocols. Low bandwidth and high network traffic in UWSNs could lead to packet collisions and data loss, and hence, proper back-off technique needs to be applied before the time synchronization process begins.…”

SLSMP: Time Synchronization and Localization Using Seawater Movement Pattern in Underwater Wireless Networks

“…In addition the performance of those protocols is nondeterministic since relative distance between nodes is changed by their own absolute position which is difficult to know in underwater scenarios. Khandoker et al [8] have proposed synchronization using node mobility designed by Gauss-Markov model and kinematic model. However, it cannot precisely describe the exact mobility pattern because seawater movement is dynamically changed.…”