Clutter removal for Wi-Fi-based passive bistatic radar

Abstract

We address the problem of static clutter removal in Wi-Fi-based passive bistatic radars. Our goal is to detect slowly moving targets in highly cluttered indoor environments, using Orthogonal Frequency-Division Multiplexing signals from the 802.11n and 802.11ac Wi-Fi standards as sources of opportunity. We propose alternatives to the commonly used Extended Cancellation Algorithm (ECA) clutter removal method. Those alternatives are compared to ECA with simulations using an innovative metric based on CA-CFAR detection, and validated with experimental measurements using two Universal Software Radio Peripherals, along with a fan and an electric train as radar targets. The conclusion of that analysis is that, thanks to the decoupled range and Doppler radar processing, simple novel methods such as Average Removal are efficient alternatives to the computationally intensive ECA which is currently the stateof-the-art in CR.

Super resolution passive radars based on 802.11ax Wi‐Fi signals for human movement detection

“…First subsection aims at showing the statistical consistency of the proposed MOS metric. Moreover, the threshold defined in (20) and its relation to SNR conditions are also discussed. The second subsection starts by defining the various scenarios that will be used to compare the proposed MOS method with other MOS methods.…”

“…Moreover, obtaining the amplitude and Doppler frequency pairs for a given range allows to filter out the static clutter. For human movement detection, the static clutter creates a crucial problem since the energy of the clutter echoes is usually higher than the echoes from humans [20]. Thus, human echoes can be concealed by the static clutter echoes.…”

Experimental Implementation of a Multi-Antenna 802.11ax-based Passive Bistatic Radar for Human Target Detection

“…There is thus an error on the estimated speed due to the unknown projection factor ε r . Elements for whichv r = 0 are here referred to as static clutter and cancelled with Average Removal [6].…”

“…that the phase difference between antennas is still present at this stage. By neglecting the noise term in the RCĤ from (6) and considering that the phase Φ l has been calibrated to Φ 0 for each antenna l, the Doppler FFT applied onĤ gives the RDAC expressed as follows:…”

“…However this work relies on old versions of 802.11 standards featuring a low bandwidth (< 20 MHz), yielding a range resolution above 10 m, which is not suited for indoor monitoring. Our recent works perform range and speed processing separately in a decoupled approach with channel estimation and Doppler Fast Fourier Transform (FFT) respectively and leverage the 802.11ac Wi-Fi standard, featuring a bandwidth up to 160 MHz, to obtain a range resolution of 0.9375 m [5], [6].…”