State-space characterization of Viterbi detector path metric differences

Issues related to determining the state-space of survivor path metric differences in applications of the Viterbi algorithm are explored. In particular, the problem of characterizing the entire space of path metric differences, achievable from a given initial state, and calculating the probability density for the differences as a function of the distribution of the (noisy) channel output samples is addressed. For two cases of interest in digital recording the one-step dynamics of Viterbi detectors is described, and the recurrent region of difference metrics is characterized