Improving the OFDMA performance with common carrier frequency offset correction

In an OFDMA system, different carrier frequency offsets (CFOs) are possibly raised due to the mismatch of local oscillators and the Doppler effect because of multiple-antenna channels. In spite of an initial CFO synchronization scheme able to be applied at transmitters, the compensation of residual CFOs is required at the receiver in order to eliminate the inter-carrier interference (ICI) for individual subscribers, especially with an interleaved subcarrier allocation scheme. Unfortunately, conventional ICI mitigation methods cannot simultaneously remove the CFOs caused by multiple subscribers, and therefore, the multiuser interference (MUI) remains. In this case, a common CFO (CCFO) existing among the multiple CFOs is found in relation to the overall OFDMA system performance. In this paper, a CCFO estimation method is proposed at the OFDMA receiver, and the CCFO is then corrected to reach the minimum weighted mean square error (MSE) performance. Numerical results show that new OFDMA receivers after correcting the estimated CCFO significantly improve the overall bit error rate (BER) performance over the conventional receivers.