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 shown to be about 1.9 dB more than that of the maximum likelihood lower bound for a Lorentzian channel at user density 2.5. Recently, an advanced version of MDFE, called M2DFE, was proposed. By using computer simulations, the BER of M2DFE has been shown to improve by about 1 dB compared to MDFE. In this paper, we first discuss the various aspects of M2DFE design and then 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 correlation at the slicer input, to improve the BER performance as well as reduce error propagation considerably. These MDFE detectors are then compared for their BERs and error propagation performances.