Pseudo-ranging based on round-trip time of bluetooth low energy beacons

Abstract

This paper presents a utilization of Bluetooth Low Energy (BLE) for a pseudo-ranging determination in indoor positioning systems. Most of BLE-based ranging techniques rely on Received Signal Strength Indicator (RSSI) of the broadcasting beacons, which has a shortcoming as it is highly sensitive to the surroundings or the orientation of the device. Therefore, this paper proposes the two-way Time-of-Flight (ToF) approach for ranging of BLE beacons. The Round-Trip Time (RTT) of the beacons has been measured using a CPU clock cycle generated by an external Temperature Compensated Crystal Oscillator (TCXO), and the pseudo-ranging calculation has been performed afterwards. The study results indicate that the accuracy can be improved by considering the RTT from the advertising channel that gives the best RSSI. The equation representing the relationship between the RTT and distance has been derived.