Turbo equalization for non-binary coded modulation schemes over frequency selective fading channels

This paper presents a new method of equalizing and decoding multilevel coded modulation signals over frequency selective Rayleigh fading channels. A combined receiver using iterative (turbo) concept is proposed. Reliability information coming out of the soft-input soft-output (SISO) equalizer is used to get soft values at the output of the channel decoder. Specific extrinsic values out of the decoder are then fed back to the equalizer to be used as the a priori inputs. Through simulation, after only a small number of iterations (2-3), error performance of the combined receiver can be improved with good coding gains to compare with the case of separate equalizer and decoder for TCM and TTCM schemes.