Viterbi detection of matched spectral null codes for PR4 systems

Practical considerations for implementation of trellis coding in magnetic storage channels are examined in a simulation study. Matched spectral null codes are shown to offer significant coding gains on magnetic channels over baseline PRML (class-4 partial response maximum likelihood sequence estimation). In magnetic storage products, requirements of minimum detection latency and guaranteed worst-case performance dictate the use of non-quasi-catastrophic codes. Degradation in simulated error rate performance due to quantization effects prior to Viterbi detection is characterized. Detector performance in the presence of colored noise, introduced in equalization of a Lorentzian channel to class-IV response via a zero-forcing or least-mean-square equalizer, is shown. The results shown are consistent with an asymptotic coding gain on the order of 3 dB over baseline PRML, despite the presence of colored noise