Issue No. 07 - July (2014 vol. 13)
DOI Bookmark: http://doi.ieeecomputersociety.org/10.1109/TMC.2013.108
Zhenjiang Li , School of Computer Engineering, Nanyang Technological University, Singapore
Wenwei Chen , School of Computer Engineering, Nanyang Technological University, Singapore
Cheng Li , School of Computer Engineering, Nanyang Technological University, Singapore
Mo Li , School of Computer Engineering, Nanyang Technological University, Singapore
Xiang-Yang Li , Department of Computer Science, Illinois Institute of Technology, Chicago, IL, USA
Yunhao Liu , School of Software and TNLIST, Tsinghua University, Beijing, China
In this paper, we propose a novel clock calibration approach called FLIGHT, which leverages the fact that the fluorescent light intensity changes with a stable period that equals half of the alternating current’s. By tuning to the light emitted from indoor fluorescent lamps, FLIGHT can intelligently extract the light period information and achieve network wide time calibration by referring to such a common time reference. The light period can be also viewed as an indoor context indicator. As sampling the light sensor consumes substantially less energy, FLIGHT provides us a lightweight clock calibration and time synchronization solution. In addition, FLIGHT suits various mobility-enabled scenarios and it can work well even when the network is temporarily disconnected. We address a series of practical challenges and implement FLIGHT in TelosB motes. We conduct comprehensive experiments using a 12-node test-bed in both static and mobile environments. Over one-week measurement suggests that compared with existing technologies, FLIGHT can achieve tightly synchronized time with low energy consumption. We further leverage the periodical pattern and upgrade FLIGHT to recognize the ambient indoor/outdoor context, based on which the on/off states of a variety of location-based services can be controlled automatically for mobile devices.
Clocks, Synchronization, Calibration, Lighting, Context, Educational institutions, Laboratories
Z. Li, W. Chen, C. Li, M. Li, X. Li and Y. Liu, "FLIGHT: Clock Calibration and Context Recognition Using Fluorescent Lighting," in IEEE Transactions on Mobile Computing, vol. 13, no. 7, pp. 1495-1508, 2014.