Blind decision feedback equalizer for 64-QAM systems

This paper addresses the structure-criterion switching stability of self-adaptive decision feedback equalizer (DFE) proposed for 64-QAM systems. In the case of 64-QAM signal, this blind equalizer scheme shows an instability when its recursive part controlled by entropy-based algorithm switches operation from blind to decision-directed mode. Also, closely related to this difficulty, the problem of a robust decision-directed carrier phase recovery becomes more demanding. To eliminate these two sources of instability, the existing Soft-DFE scheme is improved by both the tap-leakage decorrelator and reduced constellation phase-locked loop.