User separation and frequency-time synchronization for the uplink of interleaved OFDMA

This paper exploits the signal algebraic structure on the uplink of OFDMA system adopting interleaved carrier assignment scheme for synchronization and user separation. We first propose a subspace based method to estimate multiple user CFO deterministically using only one OFDMA block. Next, we derive a MMSE filter which can extract the ideal received signal waveform of all users individually to implement user separation and frequency synchronization at the same time. Time synchronization is carried out on single user's signal. The performance of the proposed algorithms is evaluated by simulations.