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Article

Mitigation of CSI Temporal Phase Rotation with B2B Calibration Method for Fine-Grained Motion Detection Analysis on Commodity Wi-Fi Devices

School of Environment and Society, Tokyo Institute of Technology, Tokyo 152-8552, Japan
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Author to whom correspondence should be addressed.
Sensors 2018, 18(11), 3795; https://doi.org/10.3390/s18113795
Submission received: 10 October 2018 / Revised: 30 October 2018 / Accepted: 31 October 2018 / Published: 6 November 2018
(This article belongs to the Special Issue Wireless Sensors Networks in Activity Detection and Context Awareness)

Abstract

Limitations of optical devices for motion sensing such as small coverage, sensitivity to obstacles, and privacy exposure result in the need for improvement. As motion sensing based on radio frequency signals is not constrained by the limitation above, channel state information (CSI) from Wi-Fi devices could be used to improve sensing performance under the above circumstances. Unfortunately, CSI phase cannot be practically obtained due to the temporal phase rotation generated from Wi-Fi chips. Therefore, it would be rather complicated to realize motion analysis, especially the direction of motion. To mitigate the issue, this paper proposes a CSI calibration method that employs a back-to-back channel between Wi-Fi transceivers for phase rotation removal while preserving the original CSI phase. Through experiment, calibrated CSI showed a high similarity to the channel without phase rotation measured using a Vector Network Analyzer (VNA). Another experiment was conducted to observe Doppler frequency due to simple hand gestures using the Wavelet transform. A visual analysis revealed that the Doppler frequency of calibrated CSI could correctly capture the motion pattern. To the best of the authors’ knowledge, this is the first calibration method that maintains the original CSI and is applicable for in-depth motion analysis.
Keywords: Wi-FI; channel state information; motion sensing; device-free; phase calibration; wavelet transform Wi-FI; channel state information; motion sensing; device-free; phase calibration; wavelet transform

Share and Cite

MDPI and ACS Style

Keerativoranan, N.; Haniz, A.; Saito, K.; Takada, J.-i. Mitigation of CSI Temporal Phase Rotation with B2B Calibration Method for Fine-Grained Motion Detection Analysis on Commodity Wi-Fi Devices. Sensors 2018, 18, 3795. https://doi.org/10.3390/s18113795

AMA Style

Keerativoranan N, Haniz A, Saito K, Takada J-i. Mitigation of CSI Temporal Phase Rotation with B2B Calibration Method for Fine-Grained Motion Detection Analysis on Commodity Wi-Fi Devices. Sensors. 2018; 18(11):3795. https://doi.org/10.3390/s18113795

Chicago/Turabian Style

Keerativoranan, Nopphon, Azril Haniz, Kentaro Saito, and Jun-ichi Takada. 2018. "Mitigation of CSI Temporal Phase Rotation with B2B Calibration Method for Fine-Grained Motion Detection Analysis on Commodity Wi-Fi Devices" Sensors 18, no. 11: 3795. https://doi.org/10.3390/s18113795

APA Style

Keerativoranan, N., Haniz, A., Saito, K., & Takada, J.-i. (2018). Mitigation of CSI Temporal Phase Rotation with B2B Calibration Method for Fine-Grained Motion Detection Analysis on Commodity Wi-Fi Devices. Sensors, 18(11), 3795. https://doi.org/10.3390/s18113795

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