Low complexity iterative decision feedback equalizer for 8PSK modulation in time dispersive channels

This paper addresses the problem of low complexity iterative channel equalization in intersymbol interference channels using 8PSK modulation. In this paper, we apply a recently proposed low complexity iterative channel equalization technique, called the iterative decision feedback equalizer (IDFE) to a coded system using 8PSK modulation. In this system, the structure of the DFE has been modified to incorporate soft a priori information from previous iterations of the channel decoder in detection of the corrupted signal. As a result, in this algorithm complexity is only a linear function of channel memory length. Simulation results show that this technique, using a convolutional code with constraint length K=3 and interleaver size N=3000 over a known time invariant ISI channel achieves a remarkable gain of about 5 dB compared to the conventional DFE. Complexity evaluation also shows that the iterative DFE has advantages in terms of complexity compared to other types of turbo equalization techniques and is an appropriate candidate for EDGE (Enhanced Data rates for GSM Evolution) systems.