This paper suggests a method to measure the physical distance between an IoT device and a mobile device (also a Thing) using BLE(Bluetooth Low-Energy profile) interfaces with smaller distance errors. BLE is a well-known technology for the low-power connectivity suitable for IoT devices and also for the proximity with the range of several meters. Apple has already adopted the technic and enhanced it to provide subdivided proximity range levels. But as it is also a variation of RSS-based distance estimation, iBeacon could only provide immediate, near or far status but not a real and accurate distance. To provide the distance using BLE, this paper introduces additional self-correcting beacon to calibrate the reference distance and mitigate errors from environmental factors. By adopting self-correcting beacon while measuring the distance, the average distance error showed less than 10% within the range of 1.5 meters. Some considerations are presented to extend the range to be able to get accurate distances.
Cho, H., Ji, J., Chen, Z., Park, H., & Lee, W. (2015). Measuring a distance between things with improved accuracy. In Procedia Computer Science (Vol. 52, pp. 1083–1088). Elsevier B.V. https://doi.org/10.1016/j.procs.2015.05.119