Equalization and carrier frequency offset compensation for UWA-OFDM communication systems based on the discrete sine transform

The Zero Forcing (ZF) equalizer suffers from noise enhancement and high complexity due to direct matrix inversion. On the other hand, the Minimum Mean Square Error (MMSE) equalizer suffers from high complexity, and requires Signal-to-Noise Ratio (SNR) estimation to work properly. In this paper, we use the Discrete Sine Transform (DST) for Multiple-Input-Multiple-Output (MIMO) Orthogonal Frequency Division Multiplexing (OFDM) instead of the Discrete Fourier Transform (DFT). Moreover, we present a Joint Low-Complexity Regularized ZF (JLRZF) equalizer to perform both equalization and Carrier Frequency Offset (CFO) compensation, jointly, in Underwater Acoustic (UWA)-OFDM systems. This equalizer mitigates the noise enhancement problem by using a constant regularization parameter. It has low complexity as it is based on banded-matrix approximation. The whole proposed system is compared with that based on the DFT. Simulation results prove the superiority of the proposed system compared to the traditional one. (C) 2019 Elsevier Inc. All rights reserved.