Two Novel Iterative Joint Frequency-Offset and Channel Estimation Methods for OFDMA Uplink
The authors address joint estimation of frequency offsets and channel responses in OFDMA uplink. A cyclically equal-spaced, equal-energy interleaved pilot preamble is proposed by which two iterative estimators are developed. In the first estimator, they develop a modified SAGE (Space Alternating Generalized Expectation-maximization) method by incorporating multiuser interference cancellation in both time and frequency domains into the SAGE method. The proposed modified SAGE method yields a faster convergence rate, a better estimation performance, and a lower complexity than the existing conventional SAGE method from. In the second method, they propose a very low complexity ad-hoc method to replace the high complexity frequency offset estimator of the first method.