An Efficient Near Blind Carrier Frequency Offset Estimation Scheme for MIMO-OFDM Systems

A novel technique for the estimation of carrier frequency offset (CFO) in orthogonal frequency division multiplexing (OFDM) based multiple input multiple output (MIMO) communication systems is proposed in this paper. While the conventional null subcarrier based methods estimate the CFO through a single global line 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 trial integer offset values. Then the fractional frequency offset is estimated through a fine search over one subcarrier spacing on either side centered on zero offset reference after correcting the integer offset. We also propose a novel null subcarrier allocation scheme based on Fibonacci series, which ensures a CFO estimation range equal to the OFDM bandwidth. Furthermore, performance of the proposed frequency offset estimator is mathematically analyzed by deriving the Cramer-Rao lower bound and compared it with the mean square estimation error to demonstrate its efficiency. Our algorithm is shown to outperform a popular method reported in literature in terms of BER performance and estimation complexity.