Frequency Domain Turbo Equalization under MMSE Criterion for Single Carrier MIMO Systems

In this paper, we study the design of frequency domain turbo equalization (FDTE) in single carrier (SC) multiple-input multiple-output (MIMO) systems, and prove the equivalence of two typical FDTE schemes under constant-modulus modulation. In the design of FDTE schemes, received signals and soft decision symbols obtained at the previous iteration are utilized to recover the transmitted symbols under the minimum mean squared error (MMSE) criterion. Frequency domain equalization with frequency domain decision feedback (FDE- FDDF), and frequency domain equalization with parallel interference cancellation (FDE-PIC) are presented with details. Under constant-modulus modulation, the FDE-FDDF scheme and the FDE-PIC scheme are proved to be equivalent mathematically. The equivalence of the two FDTE schemes under constant-modulus modulation has also been verified through numerical simulations.