BLE Indoor Localization based on Improved RSSI and Trilateration

Bluetooth low energy (BLE) operating in the ISM band is prone to signal fluctuations, which affect the received signal strength indicator (RSSI). RSSI is the backbone of most widely used localization algorithms and thus such fluctuations will have a negative impact on the location estimation accuracy. This paper proposes an accurate solution for indoor localization for medical applications. This work shows how to overcome RSSI instability due to equipment and environment, and to calculate the distances of a target from readers. Then the distances are used to get the coordinates of the target by means of improved trilateration algorithm. The proposed localization is based on the following: scanning only one BLE advertising channel, introducing a hard fluctuations removal filter, a weighted Kalman filter before distances calculation, and a weighted trilateration for position calculation. Test results confirm that the proposed system has an error of less than 0.5m for 95% of readings in line of sight testing. Also, the system is scalable and optimized in terms of cost and power consumption.