Fine-grained network time synchronization using reference broadcasts
ACM SIGOPS Operating Systems Review - OSDI '02: Proceedings of the 5th symposium on Operating systems design and implementation
Improved Doppler Tracking and Correction for Underwater Acoustic Communications
ICASSP '97 Proceedings of the 1997 IEEE International Conference on Acoustics, Speech, and Signal Processing (ICASSP '97) -Volume 1 - Volume 1
Timing-sync protocol for sensor networks
Proceedings of the 1st international conference on Embedded networked sensor systems
The flooding time synchronization protocol
SenSys '04 Proceedings of the 2nd international conference on Embedded networked sensor systems
MU-Sync: a time synchronization protocol for underwater mobile networks
Proceedings of the third ACM international workshop on Underwater Networks
Symbol by symbol Doppler rate estimation for highly mobile underwater OFDM
Proceedings of the Fourth ACM International Workshop on UnderWater Networks
Low-cost medium-range optical underwater modem: short paper
Proceedings of the Fourth ACM International Workshop on UnderWater Networks
IEEE Journal on Selected Areas in Communications
Time synchronization in sensor networks: a survey
IEEE Network: The Magazine of Global Internetworking
Joint time synchronization and tracking for mobile underwater systems
Proceedings of the Eighth ACM International Conference on Underwater Networks and Systems
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Time synchronization is an essential service in underwater networks, required for many functionalities such as MAC, sleep-scheduling, localization, and time-stamping of sensor events. However, there exist two fundamental challenges to underwater synchronization, namely, large propagation delays and substantial node mobility during the synchronization process. While existing underwater time sync solutions have been proposed to address these challenges, they rely on heavy signaling, which is undesirable due to high energy costs. In this paper, we introduce a powerful new approach that incorporates physical layer information, namely an estimate of the Doppler shift. Large Doppler shift has been identified as a major challenge to underwater communication, and current systems implement sophisticated solutions to estimate and track such Doppler shift for each data exchange. While an impediment to communication, we will show that the Doppler shift contains highly useful information that can be leveraged to greatly improve time synchronization. Specifically, it provides an indication of the relative motion between nodes. Our new protocol, called D-sync, strategically exploits this feature to address the timing uncertainty due to node mobility. As such, D-sync can handle substantial mobility, without making any assumptions about the underlying motion, and without extensive signaling. Simulation results show that D-sync significantly outperforms existing time synchronization both in terms of accuracy and energy.