Experimental Analysis of Received Signals Strength in Bluetooth Low Energy in Crowd Environments

Abstract

The Bluetooth Low Energy sensor detects smartphones by sending notifications to users when their smartphones enter the range. Indeed, the crowded environment influences detection because of the human body, which is 80% water. The main challenge here is the sensitivity of the Received Signal Strength Indicator (RSSI) values to environment changes, particularly in the crowded environment, which results in signal propagation or radio map changes. Therefore, distance estimation's accuracy and efficiency depend heavily on the accuracy of the measured RSSI values and radio propagation exponent. This paper aims to study the RSSI variations at different transmission distances and develop a radio waves propagation model to minimize the distance estimation error. Moreover, we analyzed the differences between measured values and estimated values of distance. The experimental result, acquired through practical experiments in a real-world environment, shows the relative error (RE) of estimation distance is 0.06 with the presence of 16.5 dBm RSSI maximum variation between crowded and uncrowded environment. Furthermore, we have also perceived that environmental specific radio waves propagation exponent significantly affects distance estimation accuracy in BLE modules. This indicates that the logarithmic distance propagation model is suitable for path-loss modeling in a crowded environment. The validity of the propagation model was further verified by comparisons between the measured and predicted distance. To explore the findings, experiments were conducted in Al-Madinah Mosque. This study's outcomes will further facilitate the development and design of several applications for the crowding environment.