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Title: Resilient clock synchronization using power grid voltage
Authors: Rabadi, Dima
Tan, Rui
Yau, David K. Y.
Viswanathan, Sreejaya
Zheng, Hao
Cheng, Peng
Keywords: Engineering::Computer science and engineering
Issue Date: 2019
Source: Rabadi, D., Tan, R., Yau, D. K. Y., Viswanathan, S., Zheng, H. & Cheng, P. (2019). Resilient clock synchronization using power grid voltage. ACM Transactions On Cyber-Physical Systems, 3(3), 31--.
Journal: ACM Transactions on Cyber-Physical Systems
Abstract: Many clock synchronization protocols based on message passing, e.g., the Network Time Protocol (NTP), assume symmetric network delays to estimate the one-way packet transmission time as half of the round-Trip time. As a result, asymmetric network delays caused by either network congestion or malicious packet delays can cause significant synchronization errors. This article exploits sinusoidal voltage signals of an alternating current (AC) power grid to limit the impact of the asymmetric network delays on these clock synchronization protocols. Our extensive measurements show that the voltage signals at geographically distributed locations in a city are highly synchronized. Leveraging calibrated voltage phases, we develop a new clock synchronization protocol that we call Grid Time Protocol (GTP), which allows direct measurement of one-way packet transmission times between its slave and master nodes, subject to an analytic condition that can be easily verified in practice. The direct measurements render GTP resilient against asymmetric network delays under this condition. A prototype implementation of GTP maintains sub-millisecond synchronization accuracy for two nodes tens of kilometers apart in the presence of malicious packet delays. The result has been demonstrated for both Singapore and Hangzhou, China. Simulations driven by real network delay measurements between Singapore and Hangzhou under both normal and congested network conditions also show the synchronization accuracy improvement by GTP. We believe that GTP is suitable for grid-connected distributed systems that are currently served by NTP but desire higher resilience against unfavorable network dynamics and packet delay attacks.
ISSN: 2378-962X
DOI: 10.1145/3342048
Rights: © 2019 Association for Computing Machinery. All rights reserved. This paper was published in ACM Transactions on Cyber-Physical Systems and is made available with permission of Association for Computing Machinery.
Fulltext Permission: open
Fulltext Availability: With Fulltext
Appears in Collections:SCSE Journal Articles

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