Reduced complexity carrier frequency offset estimation for OFDM systems

In broadband wireless communications, extensive research has been devoted to Orthogonal Frequency Division Multiplexing (OFDM) due to its ability in mitigating the multi-path effects. In OFDM, however. carrier frequency offsets (CFO) induce the loss of orthogonality among the sub-carriers and this results in significant performance degradation. In this paper, we propose a reduced complexity algorithm for CFO estimation with the aid of null sub-carriers. Using only one training OFDM symbol with N sub-carriers. the estimation range of the proposed scheme call be N/2 times larger than conventional CFO estimation schemes. As a result, the precision of the oscillators call be significantly reduced, thus, enabling low cost implementation. This paper will also investigate null sub-carrier allocations for the proposed scheme. It will be shown that the allocations should be based upon some specific binary sequences Such as the extended m-sequences proposed in this paper.