Soft output Viterbi algorithm
The soft output Viterbi algorithm is a variant of the classical Viterbi algorithm.
SOVA differs from the classical Viterbi algorithm in that it uses a modified path metric which takes into account the a priori probabilities of the input symbols, and produces a soft output indicating the reliability of the decision.
The first step in the SOVA is the selection of the survivor path, passing through one unique node at each time instant, t. Since each node has 2 branches converging at it, the difference in the branch metrics between the chosen and discarded branches indicate the amount of error in the choice.
This cost is accumulated over the entire sliding window, to indicate the soft output measure of reliability of the hard bit decision of the Viterbi algorithm.
