Improved turbo SICMMSE equalization for coded intersymbol interference channels

In this paper, we propose a low-complexity soft-input/soft-output (SISO) intersymbol interference (ISI) channel detector based on soft interference cancellation (SIC) and instantaneous minimum-mean-square-error (MMSE) filtering, where the present evaluated equalizer´s soft output is fed back and used for SIC in order to achieve a performance gain. To avoid computationally intensive matrix inversion for calculating MMSE filter coefficients, iterative algorithms such as the steepest descent (SD) method are used to find an approximate solution. Simulation results show that the proposed receiver converges quickly to the MMSE solution even using a simple 2-step SD approach. Moreover, it outperforms the powerful linear turbo equalization (LE) scheme over the severely ISI-distorted Proakis C channel.