Passive Detection of Moving Targets with Dynamic Speed Using Wi-Fi

Device-free passive detection is an emerging technology to detect whether there exists any moving entities in the area of interests without attaching any device to them. It is an essential primitive for a broad range of applications including intrusion detection for safety precautions, patient monitoring in hospitals, child and elder care at home, etc. Despite the prevalent signal feature Received Signal Strength (RSS), most robust and reliable solutions resort to finer-grained channel descriptor at physical layer, e.g., the Channel State Information (CSI) in the 802.11n standard. Among a large body of emerging techniques, however, few of them have explored full potentials of CSI for human detection. Moreover, space diversity supported by nowadays popular multi-antenna systems are not investigated to the comparable extent as frequency diversity. In this chapter, we propose a novel scheme for device-free PAssive Detection of moving humans with dynamic Speed (PADS). Both amplitude and phase information of CSI are extracted and shaped into sensitive metrics for target detection; and CSI across multi-antennas in MIMO systems are further exploited to improve the detection accuracy and robustness. We prototype PADS on commercial Wi-Fi devices, and experimental results in different scenarios demonstrate that PADS achieves great performance improvement in spite of dynamic human movements. (This chapter is based on our previously published paper. Ⓒ[2014] IEEE. Reprinted, with permission, from Qian et al. (PADS: passive detection of moving targets with dynamic speed using PHY layer information. In: 2014 20th IEEE international conference on parallel and distributed systems (ICPADS), pp 1–8, 2014).)