Inference and minimization of hidden Markov chains
David W. Gillman, Michael Sipser · 1994
A hidden Markov chain (hmc) is a finite ergodic Markov chain in which each of the states is labelled 0 or 1. As the Markov chain moves through a random trajectory, the hmc emits a 0 or a 1 at each times step according to the label of the state just entered.