Feasibility Study of Practical AoA Estimation Using Compressed CSI on Commercial WLAN Devices

Wireless local area network (WLAN)-based localization is key for advanced indoor Internet-of-Things and embedded sensor applications. To further improve the accuracy of indoor localization, attention has been focused on WLAN-based indoor localization using channel-state information (CSI) in addition to the existing information provided by received signal strength (RSS). For easy and low cost installation of wireless sensing, wireless sensing based on standardized protocols and commercial WLAN devices, such as IEEE 802.11ac and IEEE 802.11ax, is necessary. Much previous research used the angle of arrival (AoA), but commercial WLAN devices cannot use directly for AoA estimation. Therefore, we propose a practical method for estimating the AoA to solve four problems: 1) compressed CSI, which cannot be used for AoA estimation directly, 2) the antenna wireline, in which the phase changes depending on the length of the wireline, 3) the antenna spacing, in which the distance between antennas places a restriction on AoA estimation, and 4) antenna individuality, in which the antennas used in actual MIMO communication have different characteristics. We implemented the proposed method on IEEE 802.11ac devices and evaluated it in a lecture room and shield tent. The results indicate that the proposed method can estimate AoA with an average error of 9.1° and reduce the estimation error by 85.4 % compared with a straightforward approach.