Scientists in Germany have demonstrated a startling new form of surveillance: identifying people using nothing more than ordinary WiFi signals. By analyzing how radio waves bounce around a room, researchers can effectively “see” and recognize individuals — even if they are not carrying a device and even if their phone is turned off.
It’s not too different from what I can tell. They seem to just exploit the fact that beamforming information (BFI) is transmitted back to the access point. BFI is ultimately not so different from CSI. What they exploit is that they can just listen in and intercept the BSI without access to the AP.
Interesting. I didn’t actually read into BFI details, thank you