Reduction in Complexity in Maximum Likelihood Estimation and Correction of Fractional CFO in OFDM Systems

Orthogonal frequency division multiplexing (OFDM) is a prominent standard for 4G and next generation wireless communication systems. The main disadvantage of OFDM is its high sensitivity to carrier frequency offsets (CFO) caused due to the inaccuracies in the frequencies of the local oscillators and the Doppler shift due to mobility. This gives rise to inter-carrier interference. Therefore, frequency offset compensation must be accomplished with high fidelity. The effect of CFO is observed with respect to signal to noise ratio and bit error rate. The system performance can be improved by using estimation techniques like maximum likelihood estimation (MLE), least square estimation, minimum mean square error estimation and other estimation techniques. In this paper, MLE is used as a frequency offset estimation and correction scheme. The presence CFO affects the orthogonality of the subcarriers, which deteriorates the performance of the system, hence the estimation and correction of the above is of great importance in the OFDM system.