Abstract: A turbo equalizer is able to overcome severe inter-symbol-interferences because it benefits from the channel decoding gain by iteratively performing equalization and channel decoding.One of the key problems involved in turbo equalization is the information transmission between the equalizer and the decoder.In this paper, a linear minimum mean square error (MMSE) equalizer for turbo equalization of multi-level modulations is discussed.Simplified computation of the equalizer's extrinsic information for 16 QAM modulation is presented.The extrinsic information of the decoder is also discussed, and a new extrinsic information feedingback scheme proposed.Simulation results show that the proposed algorithm works effectively for multi-level modulations over severe frequency selective channel.

Key words: equalizer, MMSE, turbo equalization, channel decoding