Accurate Indoor Positioning Based on Beacon Weighting Using RSSI

Abstract

Bluetooth Low Energy (BLE) is one of the technology for indoor positioning. The coordinates in indoor positioning are calculated from the radio signal strength, although distance errors occur between the measured and calculated positions. This paper proposes the method for selecting BLE beacons in multi-point positioning for distance error reduction. The proposed method consists of Learning and Calculation Phase. The correct values used in the proposed method are the values measured with the tape measure. The Learning Phase obtains features from the RSSI distribution of each beacon and uses them to compute the coordinates in the Calculation Phase. The Calculation Phase is used for navigation with an allowable distance error of 0.5 [m] based on a person’s shoulder width. The proposed method calculates the typical value from the Learning Phase based on the probability that it fits within the distance error range of 0.5 [m]. The calculated position uses the logarithmic approximation to convert the beacon’s radio signal strength to the distance. The experiment for measuring the distance error compares the proposed method calculated, the existing method calculated by two-dimensional three-point positioning, and the tape measure-based method. The number of combinations in three-point positioning was also changed to compare the accuracy. The mean distance error compared to the value measured with a tape measure was 1.337 [m] for the existing method and 0.449 [m] for the proposed method. The proposed method is 66.3% less distance error than the existing methods.