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Understanding Advanced Bluetooth Angle Estimation Techniques for Real-Time Locationing
Bluetooth Angle of Arrival (AoA) and Angle of Departure (AoD) are techniques used for real-time locationing. The basic idea behind these techniques is to measure phase differences between received RF signals and then numerically compute AoA or AoD based on these phase differences. By using these angle readings, it is then possible to build systems that track mobile devices, people and other assets, usually in indoor environments. In Angle of Arrival, the device being tracked transmits a beacon data packet using one antenna. The AoA beacon has supplemental data (unmodulated carrier wave) added at the end of the beacon packet. This data is then IQ-sampled by the receiver, which has an antenna array, and the antennas in the array are switched during receiving of the supplemental data. The receiver usually stays in a fixed position. By using the phase difference of the samples from different antennas, we can calculate the AoA of the beacon at the receiver. In Angle of Departure, a transmitter located in a known position sends a Bluetooth beacon, simultaneously switching the transmitting antenna. The listening device has only one antenna, but knows the sequence of switching. The device is then able to calculate the angle from which the transmitter is sending. By combining angle results from different beacons and their locations, the receiver is then able to triangulate its own position in the space. Algorithms for estimating the angle are not trivial. This is especially true because in a real-life indoor environment we can experience heavy multi-pathing and signal polarization issues. In addition, radio level errors and numerical accuracy affect the results. The required algorithms are not computationally cheap and require RAM, which is valuable in an embedded system.
--- Datum: 27.02.2018 Uhrzeit: 16:00 Uhr - 16:30 Uhr Ort: Conference Counter NCC Ost