ERROR PROPAGATION SUPPRESSION TECHNIQUES FOR MDFE DETECTOR

Abstract

DFE (decision feedback equalization)-type detection schemes are promising low cost solutions for signal detection in magnetic recording. Error propagation, however, is the major obstacle for these schemes. In this thesis, the phenomenon of error propagation of DFE-type detectors is investigated and the existing error propagation suppression techniques are illustrated. Two novel techniques are proposed to detect and suppress error propagation for MDFE (multi-level decision feedback equalization) detectors. The first technique approaches the problem from the modulation coding viewpoint. A new method to design dc-free (1,7) codes for MDFE detector is suggested. By exploiting the special characteristics of the dc-free codes, error propagation can be detected. This technique is simple to implement and provides efficient detection of error propagation. The second technique is based on the effect caused by error propagation. It detects error propagation by looking for specific offsets at the slicer input and then adds a time-varying offset to Lhe slicer input for a predefined duration to prevent further errors. Comparison of the new technique with existing techniques shows that the new technique is superior to the threshold method and code constraints violation method. Compared to the auxiliary detector method, whose performance is the best among the existing techniques, the new technique is inferior for reduction of short error bursts but superior for reduction of long error bursts. Moreover, it is much simpler to implement. Therefore, the new technique provides a good compromise between error propagation suppression performance and implementation complexity.