Dual-Target Body Model For Device-Free Localization Applications

A dual-target model for quantitative evaluation of the influence of two people standing or moving in the surroundings of a radio link is presented here. This physical model, based on the scalar diffraction theory, is able to predict the effects of the attenuation of the electromagnetic (EM) wavefield generated by a RF transmitter caused by the presence of two people standing or moving in the area covered by a radio link. This model allows to relate, for each link, the RSS measurements at the receiver to the position, size and orientation, of two people located in the link area. Unlike complex EM frameworks that cannot be adopted for real-or near real-time applications, the proposed model can be employed for crowd sensing, occupancy estimation and people counting applications for both indoor and outdoor scenarios. In addition, it paves the way to a complete multi-target body model. This novel model toolkit gets over the restrictions of existing simplified multi-body models for DFL applications that exploit linear superposition of single-body effects. The proposed tool is based on the dual knife-edge approach and on a simplified EM body model, but yet effective for DFL applications. Finally, the experimental part shows some preliminary results on the dual-target applications by exploiting RF measurements obtained with WiFi-compliant radio devices working in the 5 GHz band.