Feedback Reliability Calculation for an Iterative Block Decision Feedback Equalizer

A new class of iterative block decision feedback equalizer (IB-DFE) was pioneered by Chan and Benvenuto. Unlike the conventional DFE, the IB-DFE is optimized according to the reliability of the feedback (FB) symbols. Since the use of the training sequence (TS) for feedback reliability (FBR) estimation lowers the bandwidth efficiency, FBR estimation without the need for additional TS is of considerable interest. However, prior FBR estimation is limited in the literature to uncoded M-ary phaseshift keying (PSK). In this paper we investigate FBR calculation methods for uncoded and coded M-ary quadrature amplitude modulation (QAM) systems. Results show that our newly proposed method has similar or better error rate performance than the TS method without the associated loss of bandwidth efficiency.