Tilejunction: Mitigating Signal Noise for Fingerprint-Based Indoor Localization

In indoor localization based on Wi-Fi fingerprinting, a target sends its received signal strength indicator (RSSI) of access points (APs) to a server to estimate its position. Traditionally, the server estimates the target position by matching the RSSI with the fingerprints stored in the database. Due to signal noise in fingerprint collection and target measurement, this often results in a geographically disperse set of reference points (RPs), leading to unsatisfactory estimation accuracy. To mitigate the noise problem, we propose a novel, efficient, and highly accurate localization scheme termed Tilejunction. Based on only the first two moments of the measured signal, Tilejunction maps the target RSSI of each AP to a convex hull termed signal "tile" where the target is likely within. Using a novel comparison metric for random signals, we formulate a linear programming (LP) problem to localize the target at the junction of the tiles. To further improve its computational efficiency, Tilejunction employs an information-theoretic measure to keep only those APs whose signals show sufficient differentiation in the site. It also partitions the site into multiple clusters to substantially reduce the search space in the LP optimization. We have implemented Tilejunction. Our extensive simulation and experimental measurements show that it outperforms other recent state-of-the-art approaches (e.g. RADAR, KL-divergence, etc.) with significantly lower localization error (often by more than 30 percent).