Joint low-complexity nonlinear equalization and carrier frequency offset compensation for multiple-input multiple-output orthogonal frequency division multiplexing communication systems

The conventional zero forcing (ZF) equalizer suffers from the noise enhancement problem and the increasing complexity with the increase of the number of subcarriers. On the other hand, the minimum mean square error (MMSE) equalizer mitigates the noise enhancement, but it needs estimation of the signal-to-noise ratio (SNR) to work properly. In addition, the Joint Low-complexity Regularized ZF (JLRZF) equalization and carrier frequency offset compensation scheme mitigates the noise enhancement using a constant parameter called the regularization parameter without SNR estimation. In this paper, we present a JLRZF with successive iInterference cancelation (JLRZF-SIC) scheme for multiple-input multiple-output (MIMO) discrete Fourier transform orthogonal frequency division multiplexing (DFT-OFDM) system to cope with the above-mentioned problems. The proposed JLRZF-SIC scheme jointly performs the equalization and the carrier frequency offset (CFO) compensation processes in two steps. The coupling nature of the MIMO channel is canceled in the first step. A regularization term is added in the second step to avoid the inter-symbol-interference (ISI). Simulation results show that the proposed JLRZF-SIC scheme improves the system performance with low complexity, especially in the presence of estimation errors.