Time and Frequency Synchronization for OFDMA Uplink System using the SAGE Algorithm

In this letter, we propose an iterative time and frequency synchronization scheme for orthogonal frequency-division multiple access (OFDMA) uplink system using the space-alternating generalized expectation-maximization (SAGE) algorithm. In the proposed scheme, the expectation step of the SAGE algorithm is intended to remove the multiple-access interference (MAI) caused by the other asynchronous users. Then, the maximization step is utilized in the timing and frequency offset estimation of each asynchronous user using the MAI-canceled signals. Simulation results present that the proposed scheme shows performance enhancement in the presence of multiple asynchronous users