Nuzzer: A Large-Scale Device-Free Passive Localization System for Wireless Environments

TLDR

WLANs and mobile devices have spurred interest in wireless localization, yet most work focuses on device‑based active methods, while device‑free passive localization—recently proposed—has been limited to small or controlled settings. This paper designs, implements, and analyzes Nuzzer, a large‑scale device‑free passive localization system that tracks entities in real, multipath‑rich environments. Nuzzer employs probabilistic techniques for single‑entity localization, evaluated analytically and in typical office buildings, and introduces an algorithm to estimate entity counts and coarsely localize them to improve scalability. The system achieves median localization errors below 2 m and demonstrates suitability for a wide range of application domains.

Abstract

The widespread usage of WLANs and mobile devices has fostered the interest in localization systems for wireless environments. The majority of research in the context of wireless-based localization systems has focused on device-based active localization, in which devices are attached to tracked entities. Recently, device-free passive localization (DfP) has been proposed where the tracked entity is neither required to carry devices nor to participate actively in the localization process. Previous studies have focused on small areas and/or controlled environments. In this paper, we present the design, implementation, and analysis of Nuzzer, a large-scale DfP localization system, which tracks entities in real environments, rich in multipath. We first present probabilistic techniques for DfP localization of a single entity and evaluate their performance both analytically and in typical office buildings. Our results show that Nuzzer gives location estimates with less than 2-meters median distance error. We then give an algorithm for estimating the number of entities in an area of interest and localizing them into coarse-grained zones to enhance the scalability of the system. This indicates the suitability of Nuzzer to a large number of application domains.