Systems and methods for breathing detection and rate estimation using wireless communication signals

A method for estimating a breathing rate, comprising:

• receiving at a first wireless communication device a wireless signal from a second wireless communication device;
• measuring, by the first wireless communication device, a plurality of channel state information (CSI) data points from the wireless signal, wherein breathing-related motion over time changes the CSI data points between the first and second communication devices;
• selecting, by the first wireless communication device, an initial reference CSI data point from the plurality of CSI data points;
• computing, by the first wireless communication device, a first perturbation index curve for the wireless signal using the initial reference CSI data point and a portion of the plurality of CSI data points;
• finding, by the first wireless communication device, an optimal reference CSI data point from within the plurality of CSI data points associated with a maximum perturbance index value from within the first perturbation index curve;
• computing, by the first wireless communication device, a second perturbation index curve for the wireless signal using the optimal reference CSI data point and a portion of the plurality of CSI data points subsequent to the optimal reference CSI;
• and
• determining, by the first wireless communication device, the breathing rate from the second perturbation index curve using a frequency analysis.