Indoor Positioning using BLE Beacons and User Equipments in Factory Environment

For indoor position estimation where global navigation satellite system (GNSS) cannot be used, methods using received signal strength indicator (RSSI) from bluetooth low energy (BLE) beacons have been considered. However, in factory environments where there are many metallic objects, the positioning accuracy may deteriorate significantly due to radio wave reflection and diffraction. Therefore, it is necessary to install a large number of line-of-sight (LOS) beacons in the environment and select LOS beacons for positioning. This paper proposes a method to select beacons based on RSSI variance in addition on RSSI from beacons. By selecting beacons with consideration of the variance, it is possible to exclude non line-of-sight (NLOS) beacons. Experimental results show that the proposed method reduces the average positioning error by 0.119[m] compared to the conventional method that considers only the RSSI. In addition, it is time-consuming and costly to install many beacons whose locations are known in the environment. Therefore, this paper also proposes a positioning method using user equipments (UEs) that are not required to be prior installation in the environment. The experimental results show that the proposed method reduces the average positioning error by 0.362[m] compared to the conventional method that uses only beacons.