Doppler frequency offsets estimation for high-mobility OFDM systems

In this paper, we investigate the problem of multiple Doppler frequency offsets estimation for high-mobility orthogonal frequency division multiplexing (OFDM) systems. This scenario could arise when either the receiver or the transmitter moves at very high speed resulting into various Doppler shifts for paths with different angle of arrivals. The key point is to design a particular preamble structure. Then by remodeling the received blocks through downsampling, we compact parameter space and obtain a low complexity subspace-based estimator with the performance of high-resolution. The effectiveness of the proposed scheme is verified by simulations.