Improving AOA Accuracy in BLE-Based Localization With a Hierarchical Estimation Framework and Phase Correction Mechanism

With the rapid development of the Internet of Things (IoT) technology, location-based services (LBSs) are gaining significant attention for their potential applications. Among the various LBS methods, angle of arrival (AOA) is attracting attention due to its simplicity and ease of implementation. However, in practical applications, the Bluetooth low-energy (BLE)-based 2-D antenna array encounters the problem of constant tone extension (CTE) frequency deviation (FD), which introduces phase impairments. Additionally, the support of periodical advertising (PA) event in Bluetooth poses a challenge for ensuring excellent angle estimation performance in periodic physical (PHY) channels, as the channel overlaps with the Wi-Fi frequency band. To address these challenges, we propose a hierarchical angle estimation (HAE) framework based on the phase difference of single reference antenna. The framework comprises three layers: the data acquisition layer, the phase restoration layer, and the multichannel estimation layer with angle collection solver. The HAE framework enables phase correction and accurate estimation over periodic PHY channels. We validate the proposed method on a real hardware system and demonstrate that it achieves a high level of precision and stability in the estimation of angles, which makes it suitable for practical LBSs applications in challenging environments.