Patent ID: 7165210

Claim:
A method of producing path metrics in a trellis, whose nodes describe encoder states of a code used in signal encoding, and paths between the nodes belonging to successive trellis phases of the trellis describe allowed state transitions, to which the encoder unequivocally attaches an initial state, a final state, a bit to be encoded and bits of an encoding result, the method comprising: defining the trellis phase nodes that have common nodes of a preceding trellis phase through the allowed state transitions determined by the code as basic group nodes; processing a signal by producing, trellis phase by trellis phase, path metrics corresponding to the code, and storing winner information on a winner path and path metric information on rejected paths in a memory in respect of only one node in each basic group; and re-processing the signal in an opposite direction trellis phase by trellis phase starting from the path metrics produced last by producing the path metrics of the preceding trellis phase basic group by basic group using the path metrics of the one node of the basic group of the present trellis phase and the winner information and path metric information stored in the memory.