Method and apparatus for producing path metrics in trellis

An apparatus for forming path metrics in a trellis, whose nodes describe encoder states of the code used in signal encoding, and the paths between the nodes belonging to successive trellis phases of the trellis describe allowed state transitions, to which the encoder unequivocally attaches the initial state, the final state, the bit to be encoded and the bits of the encoding result, the apparatus comprising:

• means for defining the trellis phase nodes that have the common nodes of the preceding trellis phase through the allowed state transitions determined by the code as basic group nodes;
• means for processing the signal by producing, trellis phase by trellis phase, path metrics corresponding to the code, and storing in each basic group winner information on the winner path and path metric information on the rejected paths in a memory in respect of only one node;
• and
• means for re-processing the signal in the 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.

An apparatus for producing path metrics in a trellis, whose nodes describe encoder states of the code used in signal encoding, and the paths between the nodes belonging to successive trellis phases of the trellis describe allowed state transitions, to which the encoder unequivocally attaches the initial state, the final state, the bit to be encoded and the bits of the encoding result, and the apparatus is configured to:

• define the trellis phase nodes that have the common nodes of the preceding trellis phase through the allowed state transitions determined by the code as basic group nodes;
• process the signal by producing, trellis phase by trellis phase, path metrics corresponding to the code, and storing in each basic group winner information on the winner path and path metric information on the rejected paths in a memory in respect of only one node;
• and
• re-process the signal in the 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.