In this paper, the authors present the design and implementation of SpotFi, an accurate indoor localization system that can be deployed on commodity Wi-Fi infrastructure. SpotFi only uses information that is already exposed by Wi-Fi chips and does not require any hardware or firmware changes, yet achieves the same accuracy as state-of-the-art localization systems. SpotFi makes two key technical contributions. First, SpotFi incorporates super-resolution algorithms that can accurately compute the Angle of Arrival (AoA) of multipath components even when the Access Point (AP) has only three antennas.