Low Complexity Soft Decision-Aided Equalizer for Turbo Equalization

This letter presents a soft decision-aided equalizer (SDAE), which combines linear equalizer and soft feedback interference canceller. In contrast to common turbo principle which only uses the extrinsic information from the decoder, the SDAE uses the full soft output channel decoding information and the equalizer outputs as a-prior input for the equalizer. The filter parameters of the SDAE are updated based on the minimum mean square error (MMSE) criterion. Its coefficients depend on the quality of the feedback information which changes with each iteration. The complexity is only linear with the length of the filters. Simulation results show that SDAE outperforms another similar structure of approximately same complexity for severely intersymbol interference (ISI) channel and can compare favorably with linear equalization (LE) with time varying filter coefficients.