Low complexity blind frequency-offset estimator for OFDM systems over ISI channels

Most previously reported carrier frequency off-set (CFO) estimation algorithms for OFDM systems rely on the assumption of sufficient cyclic prefix (CP) - i.e. the channel length is less than the length of CP. In practice, this can be violated leading to significant performance degradation characterized by an irreducible error floor due to model mismatch. This paper focusses on CFO estimation for uncompensated ISI channels - it introduces a modified signal model and by exploiting the special structure of the filtering matrix due to CP and virtual carriers, a novel subspace CFO estimator is proposed. The method is attractive for its low complexity by avoiding SVD computation and potential to achieve high channel utilization by decreasing the length of CP in ISI channels. Preliminary computer simulations illustrate the effectiveness of the proposed algorithm.