Accurate Indoor Localization for Bluetooth Low Energy Backscatter

With wide deployments of Bluetooth Low Energy (BLE) infrastructures and recent advances in backscatter communications, BLE backscatter based indoor localization becomes a promising solution for asset management and object tracking due to its low cost and near-zero power consumption. Despite extensive localization techniques, none can meet the high accuracy, protocol compatibility, and low-power consumption requirements in BLE backscatter localization. To fill this gap, this paper presents B2Loc, the first BLE backscatter localization system that enables decimeter-level localization for low-power backscatter tags with existing BLE infrastructures. The key insight is to design a low-power backscatter modulation to create a frequency-constant and phase-continuous Constant Tone Extension (CTE) field for backscatter localization while guaranteeing communication compatibility with the commodity BLE. In addition, B2Loc also fully exploits the signal propagation signatures and the BLE backscatter characteristic to improve localization performance. We fabricate μW-level backscatter tags with off-the-shelf components and evaluate the performance using commodity BLE infrastructures. The results show that B2Loc achieves decimeter-level median localization accuracy even deployed in multipath-rich indoor environments.