Ichnaea: A Low-Overhead Robust WLAN Device-Free Passive Localization System

WLAN Device-free passive (DfP) indoor localization is an emerging technology enabling the localization of entities that do not carry any devices nor participate actively in the localization process using the already installed wireless infrastructure. Current state-of-the-art DfP localization systems require a large overhead to construct an RF profile for the environment, that is then used as a reference for either motion detection or tracking. These profiles are also not robust to changes in the environment, requiring frequent manual maintenance or reconstruction. In this paper, we present the design, implementation and evaluation of Ichnaea, an accurate, robust, and low-overhead DfP localization system. Ichnaea uses a lightweight, typically two minutes, training period to learn the silence profile of the environment. It then applies statistical anomaly detection techniques and particle filtering, while adapting to changes in the environment, to provide its localization capabilities using standard WiFi hardware. Evaluation of Ichnaea in three typical testbeds with a side-by-side comparison to the state-of-the-art WLAN DfP systems shows that it can achieve a worst case median distance error of 2.5 m while requiring significantly lower deployment overhead and being robust to environment changes.