Challenges

Typical location determination systems require the presence of a physical device that is attached to the person that is being tracked. In addition, they usually require the tracked device to participate actively in the localization process. In this paper, we introduce the concept of Device-free Passive (DfP) localization. A DfP system is envisioned to be able to detect, track, and identify entities that do not carry any device, nor participate actively in the localization process. The system works by monitoring and processing changes in the received physical signals at one or more monitoring points to detect changes in the environment. Applications for DfP systems include intrusion detection and tracking, protecting outdoor assets, such as pipelines, railroad tracks, and perimeters.We describe the DfP system's architecture and the challenges that need to be addressed to materialize a DfP system. We show the feasibility of the system by describing algorithms for implementing different functionalities of a DfP system that works with nominal WiFi equipment. We present two techniques for intrusion detection and a technique for tracking a single intruder. Our results show that the system can achieve very high probability of detection and tracking with very few false positives. We also identify different research directions for addressing the challenges of realizing a DfP system.