Wider is Better? Contact-free Vibration Sensing via Different COTS-RF Technologies

Vibration sensing is crucial to human life and work, as vibrations indicate the status of their respective sources (e.g., heartbeat to human health condition). Given the inconvenience of contact sensing, both academia and industry have been intensively exploring contact-free vibration sensing, with several major developments leveraging radio-frequency (RF) technologies made very recently. However, a measurement study systematically comparing these options is still missing. In this paper, we choose to evaluate five representative commercial off-the-shelf (COTS) RF technologies with different carrier frequencies, bandwidths, and waveform designs. We first unify the sensing data format and processing pipeline, and also propose a novel metric v-SNR to quantify sensing quality. Then our extensive evaluations start from controlled experiments for benchmarking, followed by investigations on two real-world applications: machinery vibration measurement and vital sign monitoring. Our comprehensive study reveals that Wi-Fi performs the worst among all five technologies, while a lesser-known UWB-based technology achieves the best overall performance, and others have respective pros and cons in different scenarios.