Commodity WiFi Can Capture Your Respiration Even the Motion Interference Exists

Abstract

As one widely used wireless technique, WiFi has the potential to perform non-contact monitoring of respiration. While pioneering works have demonstrated promising performance, they inevitably ignore the impact of pervasive motion interference caused by non-target body areas or nearby surrounding interferers. Furthermore, motion interference has a significant negative impact on the accuracy of respiration monitoring due to signal aliasing, which further decays the recognition accuracy of these systems. To tackle these limitations, by employing a novel beamforming algorithm, we propose Wi-Spatial , an anti-motion interference respiration monitoring system based on commodity WiFi devices that can robustly mitigate the motion interference of non-target persons and further effectively extract the respiration signals from the target person. Wi-Spatial first enables stable beam pattern generation of channel state information (CSI) via adaptive phase shift compensation. Then, a directional nulling beamforming (DN-BF) scheme that directs the main lobe toward the target subject while adaptively placing beam nulls in the directions corresponding to the interferer is proposed to enhance the signal response in the area where the target subject is located. Extensive experiments have demonstrated that Wi-Spatial achieves high performance in monitoring respiration under various intensity motion inferences, especially in high-intensity motion interference, with a median absolute deviation of 0.41 bpm, which outperforms the state-of-the-art solutions by \(28\% \) .