Apparatus and method for performing passive sensing

A non-transitory computer-readable storage medium storing instructions that when executed by a computer cause the computer to perform a method for passing sensing using wireless digital communications, wherein said wireless digital communications are frame-based with a predefined frame structure, said method comprising:

• receiving a reference signal into a reference channel, wherein said reference signal comprises a direct version of a radio frequency transmission as part of said wireless digital communications;
• receiving a surveillance signal into a surveillance channel;
• detecting and extracting portions of the reference signal corresponding to data transmissions based on said predefined frame structure;
• extracting portions of the surveillance signal corresponding to the extracted portions of the reference signal;
• performing a cross-correlation on the extracted portions of the reference signal and the surveillance signal to determine a range-Doppler surface;
• and providing a real-time display of said range-Doppler surface and/or of information derived therefrom.

A system that passes sensing using wireless digital communications, wherein said wireless digital communications are frame-based with a predefined frame structure, said system comprising a circuit that:

• receives a reference signal into a reference channel, wherein said reference signal comprises a direct version of a radio frequency transmission as part of said wireless digital communications;
• receives a surveillance signal into a surveillance channel;
• detecting and extracting portions of the reference signal corresponding to data transmissions based on said predefined frame structure;
• extracts portions of the surveillance signal corresponding to the extracted portions of the reference signal;
• performs a cross-correlation on the extracted portions of the reference signal and the surveillance signal to determine a range-Doppler surface;
• and providing a real-time display of said range-Doppler surface and/or of information derived therefrom.