Full duplex backscatter

Abstract

This paper asks the following question: could we transform the radios found in our personal gadgets into powerful multipurpose scanning devices that can detect and locate tumors, guns, buried human bodies, a la the Star Trek Tricoder? Our key insight is that if radios could measure the backscatter of their own transmissions (i.e. reflections from the environment of their transmissions), then Tricorder-style powerful object detection and localization algorithms could be realized. In this paper we focus specifically on backscatter measurement, we describe novel circuits and algorithms that can be added to existing radios to enable them to accurately and concurrently receive and disentangle their own transmissions' reflections and infer its properties.

Feasibility and limits of wi-fi imaging

“…Wision is also related to recent proposals [10,35] that use techniques like compressive sensing with single-antenna devices and full-duplex radios to detect the presence of any object in a sparse environment. In contrast, Wision addresses the more general problem of transforming Wi-Fi into a camera that creates images of objects.…”

Reusing 60GHz Radios for Mobile Radar Imaging

“…The HXI radios use the On-Off-Keying modulation to generate sine waves in random on-off periods and reports RSS every 50ms. We note that under the same environment, the RSS of the HXI link is actually 17dB 12 weaker than that of the Wilocity chipset. This is because our HXI radio transmits at 0dBm and the cable that connects the horn antenna to the radio introduces 23dB loss (in order to enable mechanical antenna rotation).…”

“…Traditional imaging radars detect the position and shape of an object by emitting RF signals and analyzing the reflected signal [7,8,15,12,36,6,10,34,42]. They typically make use of specialized hardware such as FM circuits and highly directional, large dish antennas, and thus are not suitable for mobile devices.…”

“…Researchers have explored WiFi-band solutions to detect human motion, activity and gestures, and to detect (metal) objects [8,7,15,36,29,40,12]. A recent work built WiFi imaging using OFDM and large phased arrays (available on APs) and discussed the resolution limitation due to its large wavelength [25].…”

“…Acoustic solutions have been used successfully for ranging over short distances [39,49], but are easily disrupted by background noise and fail over longer distances. Prior works on RF imaging use WiFi bands to track human motion and activity [7,8,15,12], detect metal objects [12], and map large obstacles [36]. But they require costly specialized hardware or large antennas unsuitable for mobile devices.…”