New design of pilot patterns for joint semi-blind estimation of CFO and channel for OFDM systems

The greatest threat to the OFDM system is the loss of orthogonality between subcarriers due to the carrier frequency offset (CFO) which results in significant performance degradation. In addition to this last problem was the effect of propagation over multipath fading channel. Hence, both the channel and the CFO need to be estimated and corrected at the receiver for subsequent symbol detection.A new joint semi-blind CFO and channel estimation method for OFDM systems operating in multipath fading channels is investigated in this paper. The proposed algorithms are based on virtual subcarriers (VSC) in one hand and on a new design of pilot patterns in OFDM blocks in other hand.We propose to use Newton–Raphson algorithm for the estimation of CFO that has a faster convergence and a lower complexity compared to similar estimators that not employed this algorithm.Finally, we derive the Modified Cramer–Rao bounds (MCRB) for semi-blind CFO and channel estimation to evaluate the performance bounds of the proposed methods for commonly encountered scenarios.The simulation results are given to verify the validity of the proposed methods.