A low complexity turbo equalizer

In this paper a new Soft Input - Soft Output (SISO) equalizer of linear complexity is developed. The algorithm can be used in the so-called Turbo Equalization scheme as a low cost solution in place of the Maximum A-Posteriori (MAP) equalization algorithm which has a prohibitive complexity for most real world applications. The proposed equalizer consists of two parts, namely, a Soft Interference Canceller (SIC) and a pre-processing part which is a new Variable-Threshold Decision Feedback Equalizer (VTDFE). The main difference in the proposed equalizer as compared to the SIC is that the input to the cancellation filter is computed not only using a-priori probabilities, but information from the received signal as well. Simulation results have shown that the proposed turbo equalizer exhibits a superior performance as compared to the turbo equalization scheme based on the conventional SIC as well as other linear complexity SISO equalizers.