Non-linear limited-feedback precoding for ICI reduction in closed-loop multiple-antenna OFDM systems

We consider precoding for intercarrier interference (10) reduction due to frequency offsets in closed-loop orthogonal frequency-division multiplexing (OFDM) systems. Since the complete channel state information (CSI) is difficult to obtain at the transmitter, we develop a novel non-linear limited-feedback Tomlinson-Harashima (LFB-TH) precoder to suppress ICI in closed-loop multiple-antenna OFDM. Our precoder applies a pre-designed codebook of matrices, which is available at both the transmitter and the receiver. The receiver selects the feedback matrix from the codebook according to a specific selection criterion and transfers the index of the chosen matrix to the the transmitter. Hence the CSI is not required at the transmitter in the proposed precoder. The codebook design criterion and feedback matrix selection criteria are analyzed. Our LFB-TH precoder significantly reduces the bit error rate (BER) degradation due to frequency offset; the degradation is virtually eliminated for normalized frequency offsets as high as 10%.