A novel PSO based carrier frequency offset estimation technique for Wi-MAX uplink transmissions

Carrier frequency offset (CFO) estimation is a challenging task in Wi-MAX uplink as it uses orthogonal frequency division multiple access (OFDMA) which demands extremely accurate frequency synchronization. Here each user may experience a different CFO relative to the base station reference carrier and the estimation of them turn out to be a multiple parameter estimation problem. In this paper, we propose a null subcarrier based particle swam optimization (PSO) technique that performs the estimation by minimizing a cost function. As compared to the null subcarrier based grid search algorithm available in the literature, the computational complexity of the proposed technique is very low. The mean square error of the CFO estimator and bit error rate performance of the Wi-MAX base station receiver that employs the proposed estimation method are studied through computer simulations. It has been shown that the proposed technique achieves a better performance than the grid search algorithm at low to medium signal to noise ratio (SNR) where the algorithm reliability really matters.