The Constant Tone Extension (CTE) function introduced since Bluetooth Low Energy 5.1 greatly improves indoor Bluetooth Low Energy localization. These small, low-energy beacons transmit signals that Bluetooth-enabled devices can use to calculate proximity and positioning. This technology enables continuous navigation, location-based services, indoor wayfinding, and so on. The new feature, used together with an appropriate antenna array, can calculate the Angle of Arrival (AoA) and Angle of Departure (AoD). This study is solely concerned with AoA mode analysis.

Estimating AoA is challenging, especially indoors. Multipath signals, which greatly corrupt results in such a complex environment, cannot be ignored. The low-energy equipment used in BLE frequently results in a substantial frequency offset, which cannot be overlooked. Several elements are thoroughly examined in order to comprehend the positioning algorithm.

The processing of I/Q data is the first step in the prokect. Then we look at how frequency offset is created and how it affects estimation. We use maximum likelihood to calculate frequency offset after modeling the data structure. Following that, numerous AoA estimation and multipath-solving methods are discussed. We discuss the operation of a 4x4 URA and the advantages and disadvantages of having multiple antennas. A virtual antenna (VA) solution addresses hardware limitations, but it fails when it comes to multipath. Finally, we model AOA estimation and use the estimated angles to localize. The Matlab algorithm, as well as the LS and TLS methods, are introduced.

In this paper, we propose an end-to-end indoor BLE positioning solution. The algorithm is tested using a Matlab simulation. The multipath scenario is created by simulating an empty room with raytracing and focusing on first-order reflection routes. The simulation demonstrates that Toeplitz Reconstruction (TR) works best with the appropriate settings. Over 90% of the results in a 4-by-4 uniform rectangular array (URA) have position errors of less than 0.14 meters. In about 60% of cases, increasing the size of the 8-by-8 Uniform Rectangular Array (URA) results in a position accuracy of less than 0.1 meters.

Following the simulation, a real-world experiment is conducted to assess the solutions' practicability and efficacy. To reduce uncontrolled multipath interference, the experiment was carried out outside. The TR method has a distance inaccuracy of 0.4 m, whereas conventional methods have a distance inaccuracy of 0.1-0.2 m. The most difficult challenge is estimating elevation angles, which necessitates additional research. The results of azimuth angle estimation studies match those of 1-D AoA estimation studies. Even with a high prediction error for elevation angle, the distance error is lower than in previous positioning research.

Finally, we make recommendations for future research. This could include optimizing algorithm parameters, taking antenna-related factors into account, changing CTE configurations, and so on.