Probability density functions of reliability information in PRML magnetic recording systems

It is well known that in high density magnetic recording channels noise models should comprise the contributions due to the non-ideal transitions. A simplified model of ´transition noise´ includes the first order Taylor´s expansion of the function that represents the ideal response in order to include the effects of transition (position) and width jitters. In this work we present an analysis that provides an evaluation of the probability density function of the noise projection over a generic error event. This procedure is used to evaluate the probability density functions of the reliability measures obtainable by a soft detection as max-log-MAP (maximum a posteriori) or SOVA (soft output Viterbi algorithm) applied to a magnetic channel.