Drift Correction of Inertial Indoor Tracking using Peer Collaboration and Strategic Beacons Placement

Due to the limitations of existing Global Navigation and Satellite Systems in non-line-of-sight environments, Indoor Tracking Systems (ITS) have been extensively discussed in the literature. These systems are split into two main categories: infrastructure-based and infrastructure-less. For infrastructure-based ITS, the challenge is the cost of deploying and maintaining infrastructure. For infrastructure-less ITS, mostly based on inertial sensors, the challenge is the accumulation of errors due to noisy sensors. This paper proposes a collaborative ITS that balances accuracy and cost to address these challenges. Our approach combines three techniques. First, each mobile device estimates its location using a Pedestrian Dead Reckoning (PDR) algorithm. Second, we rely on a collaborative scheme where mobile devices exchange their estimated locations when close to each other to correct those estimates. Third, we deploy a limited number of fixed Bluetooth Low-Energy (BLE) beacons to correct those estimates further, using a spatial indexing technique to identify strategic locations for placing the beacons. We show that collaboration between mobile devices coupled with only two beacons, with a density of 1 beacon every $4200 \mathrm{~m}^{2}$, increases the accuracy of a baseline PDR algorithm by up to 23%. With four beacons, with a density of 1 beacon for every $2100 \mathrm{~m}^{2}$, our solution offers an accuracy of 5.7 meters, corresponding to a 52% accuracy improvement compared to the PDR.