Method and apparatus for reducing noise correlation in a partial response channel

摘要

A method and apparatus are provided for reducing noise correlation through optimization of a look-ahead maximum likelihood (ML) detector. In the method of the present invention, the ML detector is optimized in terms of noise correlation generated in a partial response channel. The improved ML detector provides performance comparable to or superior to a Viterbi detector in the presence of colored noise. In the present invention, a set of finite impulse response (FIR) transversal filters are used as ML estimators for predictive detectors. The weighted sum outputs of the ML detector are compared to a set of threshold values based on previously detected data to make a determination for the current detection. The present invention improves the performance and reduces complexity of the MIL detector by optimizing the coefficients of the FIR filter in the presence of correlated noise or colored noise. The SNR (signal-to-performance ratio) of each FIR filter is determined for a range of coefficients based on the noise correlation of the channel at a given user density and a coefficient providing the highest SNR is determined for each decision function decision function. As a result, a less complex noise whitg ML detector is provided that provides improved performance over prior art ML detectors.