Authors: Rih-Lung Chung and Rih-Lung Chung
In this paper, we propose a high accuracy window-based carrier frequency offsets (CFO) estimator with multiple access interference (MAI) cancellation scheme to achieve better CFO's correction for the orthogonal-frequency-division multiple access (OFDMA) systems. First, under the assumption of multiple different CFOs, we construct the frequency-domain signal model with scalable window, and then derive the lower bound of signal-to-interferenceand- noise ratio (SINR) for different user. The analysis result shows that the performance of small CFO significantly suffers from the effects of MAI from the large CFOs.
Then, we propose two-stage CFO estimator according to the result of theoretical analysis. In the first stage, we use the window-based CFO estimator to obtain the initial CFO's estimates, where the best window width can be found the lower bound of the SINR (/ determined by the pre-simulation results). In the second stage, we adopt the multiple access interference (MAI) cancellation scheme to improve the accuracy of CFO estimation. Finally, we investigate the proposed CFO estimator algorithm for OFDMA systems by using computer simulations.
Simulation results demonstrate that the mean-square errors of the proposed algorithm with one-iteration MAI cancellation deviates the single-user bound only within 2 dB.
Keywords: carrier-frequency-offset (CFO); orthogonal frequency-divion multiple access (OFDMA); interference cancellation; scalable window.