Novel Blind CFO Estimator for Uplink Interleaved OFDMA Systems
In Orthogonal Frequency-Division Multiple Access (OFDMA) systems, closely spaced and overlapped sub-carriers are divided into groups and assigned to multiple users for simultaneous transmission. However, Carrier Frequency Offsets (CFOs) between the transmitter and the receiver destroy the orthogonality and introduce Inter-Carrier Interference (ICI), resulting in Multiple-Access Interference (MAI). By the inner structure of the received signals, this paper presents a novel CFO estimation algorithm for interleaved OFDMA uplink systems. The proposed algorithm exploits the idea of whitening the spatial covariance matrix of received signals to obtain the CFO estimates of all users.