Benchmarking and Security Considerations of Wi-Fi FTM for Ranging in IoT Devices
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The IEEE 802.11mc standard introduces fine time measurement (Wi-Fi FTM), allowing high-precision synchronization between peers and round-trip time calculation (Wi-Fi RTT) for location estimation - typically with a precision of one to two meters. This has considerable advantages over received signal strength (RSS)-based trilateration, which is prone to errors due to multipath reflections. We examine different commercial radios which support Wi-Fi RTT and benchmark Wi-Fi FTM ranging over different spectrums and bandwidths. Importantly, we find that while Wi-Fi FTM supports localization accuracy to within one to two meters in ideal conditions during outdoor line-of-sight experiments, for indoor environments at short ranges similar accuracy was only achievable on chipsets supporting Wi-Fi FTM on wider (VHT80) channel bandwidths rather than narrower (HT20) channel bandwidths. Finally, we explore the security implications of Wi-Fi FTM and use an on-air sniffer to demonstrate that Wi-Fi FTM messages are unprotected. We consequently propose a threat model with possible mitigations and directions for further research.
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