Performance comparison of modified multilevel decision feedback equalization detectors

Multilevel decision feedback equalization (MDFE) is a detection scheme that was developed for (1,k) coded recording channels, The user signal-to-noise ratio required to achieve a chosen bit error rate (BER) of 1e-6 has been s hown to be about 1.9 dB more than that of the maximum likelihood loser boun d for Lorentzian channel at user density 2.5. Recently, an advanced version of MDFE, called,M2DFE [8], was proposed. By using computer simulations, th e BER of M2DFE has been shown to improve by about I dB compared to MDFE. In this paper, se first discuss the various aspects of M2DFE design and the n present its theoretical analysis, Using the analysis, we show how the two critical parameters in the design are to be chosen for optimum performance . We also propose a modified M2DFE detector, which exploits the noise corre lation at the slicer input, to improve the BER performance as well as reduc e error propagation considerably. These MDFE detectors are then compared fo r their BER's and error propagation performances.