A high-accuracy phase-based ranging solution with Bluetooth Low Energy (BLE)

Nowadays, indoor positioning and asset tracking have become popular and essential for many applications and use-cases. As Bluetooth Low Energy (BLE) is widely deployed in smart tags, smart-phones, and smart-devices, adding functionality to support localization and asset tracking is crucial. In order to locate a device, either the angle or range to the device needs to be calculated. In this paper, we focus on a phase-based solution to calculate the range between devices. We introduce a multi-carrier phase-based ranging solution compatible with the BLE standard that utilizes BLE channel hopping to exchange tones in the entire 2.4 GHz frequency band to mitigate the multi-path fading problem. We recognize that in the BLE standard, slow channel-hopping, long packet size and frame spacing between two consecutive communications (named T_IFS) affect ranging error/accuracy, in the case of crystal offset and phase-noise. Therefore, we introduce a new mathematical model to analyze the impact of the BLE link layer protocol on the ranging error. Finally, we evaluate the accuracy of our proposed solution through modelling, by considering the results of real experiments and by validating the correctness of our mathematical model for the ranging error.