Energy-Efficient Time Synchronization Based on Nonlinear Clock Skew Tracking for Underwater Acoustic Networks

Time synchronization plays an important role in the scheduling and position technologies of sensor nodes in underwater acoustic networks (UANs). The time synchronization (TS) algorithms face challenges such as high requirements of energy efficiency, the estimation accuracy of the time-varying clock...

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Main Authors: Di Liu, Min Zhu, Dong Li, Xiaofang Fang, Yanbo Wu
Format: Article
Language:English
Published: MDPI AG 2021-07-01
Series:Sensors
Subjects:
Online Access:https://www.mdpi.com/1424-8220/21/15/5018
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spelling doaj-95ee3081db30403f8e8865eda60b93d62021-08-06T15:31:11ZengMDPI AGSensors1424-82202021-07-01215018501810.3390/s21155018Energy-Efficient Time Synchronization Based on Nonlinear Clock Skew Tracking for Underwater Acoustic NetworksDi Liu0Min Zhu1Dong Li2Xiaofang Fang3Yanbo Wu4Ocean Acoustic Technology Center, Institute of Acoustics, Chinese Academy of Sciences, Beijing 100190, ChinaOcean Acoustic Technology Center, Institute of Acoustics, Chinese Academy of Sciences, Beijing 100190, ChinaOcean Acoustic Technology Center, Institute of Acoustics, Chinese Academy of Sciences, Beijing 100190, ChinaOcean Acoustic Technology Center, Institute of Acoustics, Chinese Academy of Sciences, Beijing 100190, ChinaOcean Acoustic Technology Center, Institute of Acoustics, Chinese Academy of Sciences, Beijing 100190, ChinaTime synchronization plays an important role in the scheduling and position technologies of sensor nodes in underwater acoustic networks (UANs). The time synchronization (TS) algorithms face challenges such as high requirements of energy efficiency, the estimation accuracy of the time-varying clock skew and the suppression of the impulsive noise. To achieve accurate time synchronization for UANs, an energy-efficient TS method based on nonlinear clock skew tracking (NCST) is proposed. First, based on the sea trial temperature data and the crystal oscillators’ temperature–frequency characteristics, a nonlinear model is established to characterize the dynamic of clock skews. Second, a single-way communication scheme based on a receiver-only (RO) paradigm is used in the NCST-TS to save limited energy. Meanwhile, impulsive noises are considered during the communication process and the Gaussian mixture model (GMM) is employed to fit receiving timestamp errors caused by non-Gaussian noise. To combat the nonlinear and non-Gaussian problem, the particle filter (PF)-based algorithm is used to track the time-varying clock state and an accurate posterior probability density function under the GMM error model is also given in PF. The simulation results show that under the GMM error model, the accumulative Root Mean Square Errors (RMSE) of NCST-TS can be reduced from 10<sup>−4</sup> s to 10<sup>−5</sup> s compared with existing protocols. It also outperforms the other TS algorithms in the aspect of energy efficiency.https://www.mdpi.com/1424-8220/21/15/5018underwater acoustic networkstime synchronizationnonlinear clock skew
collection DOAJ
language English
format Article
sources DOAJ
author Di Liu
Min Zhu
Dong Li
Xiaofang Fang
Yanbo Wu
spellingShingle Di Liu
Min Zhu
Dong Li
Xiaofang Fang
Yanbo Wu
Energy-Efficient Time Synchronization Based on Nonlinear Clock Skew Tracking for Underwater Acoustic Networks
Sensors
underwater acoustic networks
time synchronization
nonlinear clock skew
author_facet Di Liu
Min Zhu
Dong Li
Xiaofang Fang
Yanbo Wu
author_sort Di Liu
title Energy-Efficient Time Synchronization Based on Nonlinear Clock Skew Tracking for Underwater Acoustic Networks
title_short Energy-Efficient Time Synchronization Based on Nonlinear Clock Skew Tracking for Underwater Acoustic Networks
title_full Energy-Efficient Time Synchronization Based on Nonlinear Clock Skew Tracking for Underwater Acoustic Networks
title_fullStr Energy-Efficient Time Synchronization Based on Nonlinear Clock Skew Tracking for Underwater Acoustic Networks
title_full_unstemmed Energy-Efficient Time Synchronization Based on Nonlinear Clock Skew Tracking for Underwater Acoustic Networks
title_sort energy-efficient time synchronization based on nonlinear clock skew tracking for underwater acoustic networks
publisher MDPI AG
series Sensors
issn 1424-8220
publishDate 2021-07-01
description Time synchronization plays an important role in the scheduling and position technologies of sensor nodes in underwater acoustic networks (UANs). The time synchronization (TS) algorithms face challenges such as high requirements of energy efficiency, the estimation accuracy of the time-varying clock skew and the suppression of the impulsive noise. To achieve accurate time synchronization for UANs, an energy-efficient TS method based on nonlinear clock skew tracking (NCST) is proposed. First, based on the sea trial temperature data and the crystal oscillators’ temperature–frequency characteristics, a nonlinear model is established to characterize the dynamic of clock skews. Second, a single-way communication scheme based on a receiver-only (RO) paradigm is used in the NCST-TS to save limited energy. Meanwhile, impulsive noises are considered during the communication process and the Gaussian mixture model (GMM) is employed to fit receiving timestamp errors caused by non-Gaussian noise. To combat the nonlinear and non-Gaussian problem, the particle filter (PF)-based algorithm is used to track the time-varying clock state and an accurate posterior probability density function under the GMM error model is also given in PF. The simulation results show that under the GMM error model, the accumulative Root Mean Square Errors (RMSE) of NCST-TS can be reduced from 10<sup>−4</sup> s to 10<sup>−5</sup> s compared with existing protocols. It also outperforms the other TS algorithms in the aspect of energy efficiency.
topic underwater acoustic networks
time synchronization
nonlinear clock skew
url https://www.mdpi.com/1424-8220/21/15/5018
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AT minzhu energyefficienttimesynchronizationbasedonnonlinearclockskewtrackingforunderwateracousticnetworks
AT dongli energyefficienttimesynchronizationbasedonnonlinearclockskewtrackingforunderwateracousticnetworks
AT xiaofangfang energyefficienttimesynchronizationbasedonnonlinearclockskewtrackingforunderwateracousticnetworks
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