Clock synchronization in distributed real-time systems
IEEE Transactions on Computers - Special Issue on Real-Time Systems
Timing-sync protocol for sensor networks
Proceedings of the 1st international conference on Embedded networked sensor systems
Fine-grained network time synchronization using reference broadcasts
OSDI '02 Proceedings of the 5th symposium on Operating systems design and implementationCopyright restrictions prevent ACM from being able to make the PDFs for this conference available for downloading
Global Clock Synchronization in Sensor Networks
IEEE Transactions on Computers
Time synchronization in sensor networks: a survey
IEEE Network: The Magazine of Global Internetworking
Localization and synchronization for 3D underwater acoustic sensor networks
UIC'07 Proceedings of the 4th international conference on Ubiquitous Intelligence and Computing
D-sync: Doppler-based time synchronization for mobile underwater sensor networks
Proceedings of the Fifth ACM International Workshop on UnderWater Networks
Scheduling granularity in underwater acoustic networks
Proceedings of the Sixth ACM International Workshop on Underwater Networks
A coordination architecture for UUV fleets
Intelligent Service Robotics
Joint time synchronization and tracking for mobile underwater systems
Proceedings of the Eighth ACM International Conference on Underwater Networks and Systems
Analog Integrated Circuits and Signal Processing
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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.