ICI compensation for interleaved OFDMA with carrier frequency offsets

One primary challenge in an OFDMA system is that different carrier frequency offsets (CFOs) simultaneously present at the transmitters. In spite of some peripheral synchronization methods already adopted for coarse estimation of CFO values, residual CFOs can exist and degrade system performance at the OFDMA receiver. A popular post-processing method, called the CLJL scheme, can be used to reduce the intercarrier interference (ICI) at the receiver end. The CLJL scheme involved circular convolution and a diagonal matrix to isolate the output signal for a required user. Although it is efficient and thereafter is successfully applied by Huang and Letaief to solve the multiuser interference (MUI) problem, we found that the ICI is not completely eliminated due to the CLJL scheme. In this paper, the effect of the residue ICI is analyzed when the OFDMA system uses interleaved subcarrier allocation. Moreover, we propose a modification technique to compensate the CLJL scheme for the residue ICI. An adaptive approach is also developed to recursively estimate the compensation factor. Simulation results show that the interleaved OFDMA system performance is improved with the proposed ICI compensation method.