PERFORMANCE ANALYSIS OF BLE 5.1 NEW FEATURE ANGLE OF ARRIVAL FOR RELATIVE POSITIONING
Keywords: Bluetooth Low Energy, Bluetooth 5.1, Angle of Arrival, Direction Finding, Relative Positioning
Abstract. The official release of Bluetooth Core Specification, version 5.1 in 2019, provides a new feature for direction determination. It introduces a fine-grained angle measurement capability including Angle of Arriva (AoA) and Angle of Departure, which is deemed essential to the development of Internet of Things applications for localization or relative positioning within the area where Global Navigation Satellite System signals cannot be received. In this paper, we set up a series of experiments to empirically evaluate the direction of the Bluetooth Low Energy transmitter based on the AoA mechanism using the commercialised equipment. The experimental evaluation is performed, for the first time to date, under four different testing environments and other various conditions to inspect the fidelity of angle measurement against the high accuracy given in the specifications. In details, an ideal environment (i.e., anechoic chamber with no multi-path effect), an underground mine, an open area and a typical office area are all tested comprehensively. The experimental results reveal that the ideal environment has the best performance with the minimum error and conforms with the provided datasheet. The worst case occurs on the data collected from the office area. We also find a regular pattern always showing up repeatedly on the error plots based on the measurement results and scrutinize the truthfulness of this rule by adding more innumerable tests conducted in the office. Our results show that the performance of accuracy does depend on the data channel selection due to the multi-path effect.