Subspace-Based Multiple Access Suppression in Synchronous Interleaved OFDMA System

In this paper, multiple access interference (MAI) suppression in synchronous interleaved orthogonal frequency division multiple access (OFDMA) system is investigated. Based on the signature vector formulated for each user, a new user detector is proposed. It is shown that when matched filtering is employed to suppress MAI in the proposed detector, under imperfect power control, strong users can severely degrade the performance of its neighboring users. To improve the system performance, we derive a subspace zero-forcing and a subspace MMSE MAI suppression scheme for the proposed detector. We show that only the knowledge of the desired user´s CFO is required in MAI suppression and the system can be rendered almost MAI-free provided that the CFO estimation is accurate enough.