On the Feasibility of Phase-based BLE Ranging for Accurate Pedestrian Tracking

Indoor localization based on Bluetooth Low Energy (BLE) is traditionally implemented by matching Received Signal Strength (RSS) fingerprints of nearby BLE nodes. Depending on the node density, pure RSS-based BLE localization only provides room-level or zone-level accuracies. For pedestrian tracking, BLE-based RSS fingerprinting is often fused with Pedestrian Dead Reckoning (PDR) using Inertial Measurement Units (IMU), which can provide up to $1-2 \mathrm{~m}$ accuracy. Recently, a phase-based BLE ranging method has been developed, which can accurately measure the distance between two BLE devices. Initial experiments on a moving platform showed promising results for accurate localization. In this work, the feasibility of this technology for pedestrian tracking is evaluated. On-body phase-based BLE and IMU measurements are performed in an industrial lab environment with four BLE anchors. A hybrid Particle Filter (PF) algorithm is designed, which fuses phase-based BLE ranging, PDR, and a range correction algorithm. Our proposed PF algorithm achieves a median and p75 error of $0.70 \mathbf{m}$ and $1.03 \mathbf{~ m}$ respectively, which outperforms traditional RSS-based (hybrid) BLE localization algoritms.