Published on: 03-Jul-2017
Experiments in Singapore show that powerline electromagnetic radiation contains time information with error down to 50 milliseconds.
A research through collaboration among NTU, UIUC Advanced Digital Sciences Center (ADSC), and SUTD received the best paper award at the 2017 International Conference on Information Processing in Sensor Networks (IPSN), a prestigious conference on sensor networks. This research explores the natural timestamps in the power grid's frequency fluctuations sensed from the powerline electromagnetic radiation (EMR).
The research team, headed by Dr. Rui Tan (left), an assistant professor of computer science and engineering at NTU and an adjunct senior research scientist at ADSC, aims to secure the clocks of devices in power grids against potential cyber attacks. If the clocks aren't right, the power system can't run properly and could have catastrophic consequences. Many critical infrastructures still use legacy clock synchronization protocols that were developed 30 to 40 years ago, leaving them especially susceptible to attacks. Recent approaches, including GPS, FM radio or Wi-Fi beacons, have their problems, such as being power hungry, too expensive, or susceptible to network delays and outages.
In this award-winning research, the team investigated the time accuracy of EMR natural timestamps on two different IoT platforms: a high-end single board computer with a customized EMR antenna and a low-end mote with a normal conductor wire acting as an EMR antenna. As the power grid frequency is continuously and near-randomly fluctuating, and identical across a large geographic area, it gives researchers a fingerprint of the time. If the fluctuations are captured, one device's fluctuations can be compared to the fluctuation of a data trace collected somewhere else. This helps researchers know the time when the nodes captured the fluctuations. The team calls the inferred time as powerline forensic time. The research shows that both IoT platforms can achieve lower sub-second accuracy in capturing the powerline forensic time. Based on the time fingerprints, clock synchronization protocols no longer suffer from the delays in transmitting synchronization packets, which has been a longstanding issue for almost all clock synchronization protocols based on message exchange.
The lead researcher, Dr. Yang Li, demonstrated their prototype clock synchronization system based on the power grid frequency fingerprints. They have installed the prototype sensors across Singapore, at their homes, at NTU, and at ADSC. The sensors stream the real-time fingerprints to a server, which evaluates the time accuracy of the fingerprints. The team is planning on developing a product based on the technique that could be commercialized.
Prior to this IPSN paper, the team has also published a paper in the 2016 IEEE Real-Time Systems Symposium (RTSS) on obtaining the natural timestamps directly from wall power sockets. These natural timestamps are more accurate, giving sub-millisecond accuracy.
The research was funded under the Energy Innovation Research Programme (EIRP, Award No. NRF2014EWTEIRP002-026), administrated by the Energy Market Authority (EMA). The EIRP is a competitive grant call initiative driven by the Energy Innovation Programme, and funded by the National Research Foundation (NRF).
Yang Li, Rui Tan, David Yau. Natural Timestamping Using Powerline Electromagnetic Radiation. In The 16th ACM/IEEE International Conference on Information Processing in Sensor Networks (IPSN), April 18-21, 2017, Pittsburgh, PA, USA.
Sreejaya Viswanathan, Rui Tan, David Yau. Exploiting Power Grid for Accurate and Secure Clock Synchronization in Industrial IoT. In The 37th IEEE Real-Time Systems Symposium (RTSS), November 29 - December 2, 2016, Porto Portugal.
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