A Low Complexity Null Subcarrier Aided Frequency Offset Estimation Technique for OFDM

In this paper, a novel scheme for the carrier frequency offset estimation in OFDM communication systems is proposed. While the conventional null subcarrier based methods estimate the offset by a single global search, the proposed method employs a two step procedure. Firstly the integer frequency offset is estimated by means of a cost function minimization over the integer offset values. Then the fractional frequency offset is estimated through a fine search over one subcarrier spacing on either side centered on zero after correcting the integer offset. Performance of the frequency offset estimator is mathematically analyzed by deriving the Cramer-Rao bound (CRB). Our algorithm is shown to outperform some of the methods reported in literature in terms of BER performance and receiver complexity.