Adaptive Iteration Methods for Blind Carrier Frequency Estimation in Multi-User OFDMA Systems

Subspace-based blind carrier frequency offset (CFO) estimation algorithms in orthogonal frequency division multiple access (OFDMA) systems have been developed in the literature. However, the algorithms have some restrictions or require high computational complexity. In this paper, we propose simple iteration schemes to reduce complexity with an adaptive manner and present a time-variant CFO adaptive estimation method. In the first part of the proposed algorithm, with initial rough estimated CFOs, it employs iterative methods to obtain CFO estimates. And the second part is to use proposed adaptive process to obtain the updated CFO estimation and track the parameters' time-variations. The simulation results demonstrate the efficacy of the proposed iteration and adaptive schemes and the mean squared errors are near to the Cramer-Rao bounds.