Signal Processing and coding for High Density Magnetic Recording Channels

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William E. Ryan RIA: Signal Processing and Coding for High Density Magnetic Recording Channels In this project we first take a closer look at previously reported results on the performance of error control codes on high density magnetic recording channels (MRCs). In particular, we derive optimal code rates (in the sense of maximizing coding gain) and then examine the gains afforded by optimal rate codes assuming both infinite and finite decoding effort. Previous work examined coding gains of non-optimal rate codes assuming an infinite decoding effort. We will compare the performance of maximum likelihood sequence detection (MLSD) of a coded MRC with that of an uncoded MRC equalized to partial response shape of equivalent complexity. Such partial response shapes are to be determined by this research. This work has applications in very high density recording systems where codes may in fact be responsible for a performance loss. We will seek to find partial response shapes appropriate for commonly used constrained codes which, when combined with MLSD, provide an improvement over today's bit-by-bit detectors. The study will include both computer simulations and analysis and will examine the effectiveness of coding and partial response techniques on actual recorders. In particular, we will examine the immunity to nonlinear interference, overwrite, and increased track density.