Semiblind techniques for carrier frequency offset estimation in OFDM systems

In this paper we consider a semiblind carrier frequency offset (CFO) synchronization scheme based on the insertion of pilot tones and exploiting the statistical redundancy of the OFDM signal due to the cyclic prefix and/or to virtual subcarriers. In particular, under the assumption that the number of subcarriers is sufficiently large, the received signal is modeled as a circular complex Gaussian random vector (C-CGRV) with nonzero mean. Therefore, by exploiting the joint probability density function for C-CGRVs, unconditional maximum likelihood CFO estimators are derived. The performance of the proposed semiblind algorithms is assessed via computer simulation and compared with that of some blind and semiblind CFO estimators previously proposed in the literature.