Translating BLE Received Signals across different Smartphones

Abstract

This report constitutes the final product of my internship, where research was conducted on the differences of the Bluetooth Low Energy signal reception between 2 different phones (p1, p2) and eventually, the possibility of developing a translation function that could be used to predict the signal strength reception of p1, by considering the signal strength reception of p2. Such model would be particularly useful to applications related to Indoor Localization/Positioning, as these are often based on the BLE signal strength. For the development of this model, the influence of several parameters was assessed, such as: a) the distance between a phone and a beacon, b) their orientations and c) the number of concurrently broadcasting beacons, and all were found to be significant. Furthermore, it was discovered that as long as there is no movement in the system, the BLE signal reception at a specific channel has low variations and so, even a few samples can be representative for each channel. The evaluation of the translation functions was quite promising. Ultimately, by taking advantage of a specific Android's behaviour during the training phase, it became possible to identify the channels of incoming BLE signals. This information was then used to significantly enhance the performance of the translations under specific circumstances (i.e. the channels can be identified during the operational phase too).