Use of the Viterbi algorithm to compute error events of trellis phase coding in order of increasing distance

The use of the Viterbi algorithm to evaluate the minimum-distance parameters of trellis phase codes is extended to evaluate distances and paths of error events other than the free-distance event. Distances and paths are found for error events sequentially in order of increasing distance, starting with the free-distance event. Memory requirements increase slowly with the number of error events required. The time taken to find the next error event increases slowly with the number of error events already found. Results of sample calculations and computation times are included