A new model for the signal dependent transition noise and partial erasure which occurs in the readback signal from thin film recording media is reviewed. This model, which is referred to as the microtrack model, has its basis in physics and can be entirely specified by three parameters of the media. It is used both as a simulation tool and for analytical calculation. Through simulation, the effect of various amounts media noise on a PR4 channel is shown. Analytically, the amount of jitter and widening effects of the noise produced by the model are examined. Also, the autocorrelation of this noise and the effect of partial erasure on it is examined.

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Recent work on the application of turbo decoding techniques to partial response channels has focused on additive white Gaussian 'noise channel models. Simulations using these ideal partial response channel models show gains exceeding 5 dB over uncoded systenb at bit error rates of lo''. Since the APP detectors of the turbo decoder assume uncorrelated Gaussian noise, the performance on more realistic channel models, using correlated and mediadependent noise, was unknown. In this work, we replace the white noise partial response channel model with more realistic channel models. First, the effects of colored noise are investigated with an equalized Lorentzian channel model. Then, media noise is added by incorporating the microtrack model into the system. Simulation results of the ,turbo decoding system with the various channel models will be presented. Additionally, since the use of an outer Reed-Solomon code is anticipated in an actual system, the burst statistics at the error floor are investigated.

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