Carrier-frequency offset estimation for OFDMA uplink with generalized subcarrier-assignment

Maximum likelihood (ML) carrier-frequency offset (CFO) estimation in the uplink of an orthogonal frequency-division multiple-access (OFDMA) system with a generalized carrier-assignment scheme (GCAS) is a complex multi pie-parameter estimation problem. The computational complexity of the ML solution based on a multi-dimensional exhaustive search is prohibitive. The existing solutions reduce the complexity by replacing the multidimensional search with a sequence of single-dimensional searches. However, those solutions suffer from either poor estimation accuracy or is still of high complexity. In this paper, we propose a new approach called as the divide-and-update frequency estimator (DUFE), which outperforms the existing solutions in the sense that it has lower computational complexity while maintaining high estimation accuracy similar to the exact ML solution. Performance and complexity comparisons are provided with numerical results to illustrate the effectiveness of the proposed method.