Analyzing passive Wi-Fi fingerprinting for privacy-preserving indoor-positioning

Wi-Fi fingerprinting is the most actively investigated indoor positioning technique, yielding adequate positioning accuracy on existing wireless infrastructures. However, the positioning process commonly requires active 802.11 scans where probe requests are sent out. These frames can easily be captured and used for tracking mobile devices without the users' consent or even awareness. In order to preserve the users' privacy, a fully passive positioning process for Wi-Fi fingerprinting is proposed in this paper. With the presented approach, a mobile device passively listens for beacon frames in monitor mode to determine a valid RSSI fingerprint while not sending out any information. Our passive method is evaluated against common active fingerprinting in a real-world environment. The obtained results yield the conclusion that the proposed approach performs even slightly better in terms of accuracy and precision. Furthermore, less time is needed for obtaining a position fix, while preserving the users' privacy during the acquisition of position updates.