Wireless communication systems employed in buildings (such as WiFi)
can be used for bistatic radar to track targets moving in the building.
The transmit and receive hardware and software can be readily
implemented using Gnu radio. The general processing steps at the
receive include Doppler frequency extraction, using FFT or
MUSIC-algorithm based processing, following by Viterbi or BCJR
algorithm to smooth the frequency trajectory, followed by track
extraction using an extended Kalman filter. The method has been
implemented and tested using real hardware.