Optimal TCM codec search method for dual stream systems, and encoder/decoder using the same

A method for searching for an optimal codec suitable for dual stream transmission, comprising the steps of:

• a) determining a mixed pattern of normal stream and robust stream, a trellis of the normal stream or the robust stream being maintained as much as 4Z steps where Z is a natural number;
• b) determining a robust stream trellis structure to be applied to the mixed pattern based on how coders are connected;
• c) forming a dual stream trellis by mixing the normal stream trellis with the robust stream trellis to satisfy a condition that a normal stream state and a robust stream state are equal to modulo 4;
• d) computing a free distance based on a dual stream free distance computation termination condition which includes that a current step is positioned in the normal stream trellis, and that two paths reach predetermined states p and q to satisfy p=q modulo 4;
• e) determining an optimal coder based on the free distance.

An apparatus for decoding dual stream, comprising:

• a receiving means for converting receiving signals into baseband signals;
• an equalizing means for determining a symbol level of the receiving signals;
• and
• a decoding means for decoding the symbol level into data symbols,
• wherein a data symbol and a subsequent state are determined in a coder determined by forming a dual stream trellis by mixing a normal stream trellis and a robust stream trellis and by referring to a dual stream free distance computation termination condition at departing points of the dual stream trellis structure.