Performance comparison of detection methods in magnetic recording

Various detection schemes suitable for magnetic recording are compared in terms of their effective signal-to-noise ratios. It is shown that at high densities the performance of conventional detectors such as a peak detector, a threshold detector with partial response equalization, a decision feedback equalizer, and a Viterbi algorithm detector tuned to a linearly truncated channel fall far below the optimum performance that can be achieved by the maximum-likelihood sequence detector (MLSD). It is shown that while implementing the full MLSD is clearly out of the question for high densities with severe intersymbol interference (ISI), there exists an efficient detection scheme which achieves an excellent compromise between hardware complexity and detection performance. This scheme, which is called the fixed-delay tree search with decision feedback, combines a fast and efficient tree-search algorithm with a decision feedback equalizer to cancel out a portion of ISI without noise enhancement. It is well suited for run-length-limited systems and attains performance close to that of MLSD while maintaining reasonable implementation cost and processing requirements