Fine-Grained Indoor Localization Using Single Access Point With Multiple Antennas We propose a single access point-based fine-grained indoor localization system in multipath environments using 802.11ac Wi-Fi signals. The physical layer of 802.11ac supports orthogonal frequency-division multiplexing modulation (OFDM) scheme, more antennas, and multiuser multiple-input multiple-output. Angle-of-arrival (AOA) of the paths can be obtained using the phase difference among all the antennas. Similarly, time of arrival (TOA) information is estimated from the phase difference among all the subcarriers of the OFDM signal. After obtaining the AOA and TOA information of the dominant paths, an auto paring approach is proposed to identify the line-of-sight (LOS) path. Mobile device can be localized using the estimated AOA and TOA information of the LOS path. Performance analysis of the proposed method is provided. Numerical simulations are carried out to evaluate the performance. Based on the simulation results, meter or submeter level accuracy is obtained for the proposed method.