Correction techniques for the phase noise, carrier frequency offset (CFO), and sampling frequency offset (SFO) that corrupt raw CSI measurements from non-coherent commodity radios, restoring the phase stability required for sensing.
Presents linear and conjugate multiplication methods for estimating carrier and sampling frequency offsets from consecutive CSI packets, and the compensation filters applied before phase-sensitive feature extraction.
Covers unwrapping algorithms, linear phase fitting, and outlier rejection needed to sanitize CSI phase data from commodity Wi-Fi NICs that lack tight transmitter-receiver clock synchronization.