Algorithm for Adaptive Filtering of Distance Measurements via Wi-Fi FTM

• Marcos Stenner UFJF http://orcid.org/0009-0001-5830-2947
• Edelberto Franco Silva UFJF https://orcid.org/0000-0002-0058-9260
• Alex B. Vieira UFJF https://orcid.org/0000-0003-0821-126X
• Rodrigo Mendes Peixoto UFJF https://orcid.org/0009-0007-0506-327X
• Michael Zancanella UFJF https://orcid.org/0009-0007-6827-5421
• Emmanuel Okwu UFJF

DOI: https://doi.org/10.5753/sbrc.2025.5836

Abstract

Distance measurement using the Fine Time Measurement (FTM) protocol, which is part of Wi-Fi specifications, presents significant limitations due to multipath. This work proposes an asymmetric adaptive filter to improve FTM measurements, taking into account intrinsic characteristics of this protocol. The developed algorithm implements a filter with parameters adjusted considering the target velocity and FTM’s tendency to overestimate distances. Experiments demonstrated that the method reduces the average measurement error by up to 50% when compared to pure FTM. Its low computational complexity makes it especially suitable for implementation in embedded systems. The results indicate that the solution is effective for real-time distance measurement applications using Wi-Fi, including in low-cost hardware.

Keywords: ESP32, Adaptive Filter, FTM, IoT, Indoor Positioning, Wi-Fi

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