Practical implementation of an efficient forward-backward algorithm for an explicit-duration hidden Markov model

This correspondence addresses several practical problems in implementing a forward-backward (FB) algorithm for an explicit-duration hidden Markov model. First, the FB variables are redefined in terms of posterior probabilities to avoid possible underflows that may occur in practice. Then, a forward recursion is used that is symmetric to the backward one and can reduce the number of logic gates required to implement on a field-programmable gate-array (FPGA) chip.