Virtual Antenna Array and Fractional Fourier Transform-Based TOA Estimation for Wireless Positioning.

In this paper, a novel virtual antenna array and fractional Fourier transform (FRFT)-based 2-dimension super-resolution time-of-arrival (TOA) estimation algorithm for OFDM WLAN systems has been proposed. The proposed algorithm employs channel frequency responses (CFRs) at the equi-spaced positions on a line or quasi-line moving trajectory, i.e., the CFRs of a virtual antenna array, to extract multipaths' TOA information. Meanwhile, a new chirp-like quadratic function is used to approximate the channel multipaths' phase variation across the space dimension, which is more reasonable than the traditional linear function, especially for relatively big virtual antenna array sizes. By exploiting the property of chirp-like multipaths' energy concentration in the FRFT domain, the FRFT can be first used to separate chirp-like multipath components, then the existing TOA estimation methods in frequency domain can be further employed on the separated multipath components to obtain the multipaths' TOA estimates. Therefore, the proposed algorithm can make more use of the multipaths' characteristics in the space dimension, thus it can efficiently enhance the multipath resolution and achieve better multipaths' TOA estimation performance without requiring a real antenna array. Simulation results demonstrate the effectiveness of the proposed algorithm.