Widely Turbo Equalizer for DFT-S-OFDM Systems with Transmitter IQ Imbalance

In this paper the frequency turbo equalization is investigated for Discrete Fourier Transformation Spread Orthogonal Frequency Division Multiplexing (DFT-S-OFDM) systems with transmitter In-phase and Quadrature Imbalance (IQI) interference caused by imperfect Zero Intermediate Frequency (ZIF) Radio Frequency (RF) front ends. Based on the widely orthogonal principle and the turbo equalization principle, the frequency Widely Linear Minimum Mean Square Error (WLMMSE) turbo equalizer for DFT-S-OFDM systems with transmitter IQI is derived. Matrix transformations are employed to further reduce the complexity. Simulation results confirm that with transmitter IQI, the proposed turbo equalizer significantly outperforms the conventional counterpart turbo equalizer with only slightly increasing of the computation complexity.