  An indoor localization approach uses Wi-Fi Access Points (APs) to estimate
the Direction of Arrival (DoA) of the WiFi signals. This paper demonstrates
FIND, a tool for Fine INDoor localization based on a software-defined radio,
which receives Wi-Fi frames in the 80 MHz band with four antennas. To the best
of our knowledge, it is the first-ever prototype that extracts from such frames
data in both frequency and time domains to calculate the DoA of Wi-Fi signals
in real-time. Apart from other prototypes, we retrieve from frames
comprehensive information that could be used to DoA estimation: all preamble
fields in the time domain, Channels State Information, and signal-to-noise
ratio. Using our device, we collect a dataset for comparing different
algorithms estimating the angle of arrival in the same scenario. Furthermore,
we propose a novel calibration method, eliminating the constant phase shift
between receiving paths caused by hardware imperfections. All calibration data,
as well as a gathered dataset with various DoA in an anechoic chamber and in a
classroom, are provided to facilitate further research in the area of indoor
localization, intelligence surfaces, and multi-user transmissions in dense
deployments.
