1. A system comprising: a first component that decodes an input bit of data transmission stream; a second component that de-interleaves on an output of said first component; a third component that decodes an output of said second component; a fourth component that interleaves an output of said third component in a feedback loop to said first component; a fifth component adapted to: calculate an initial branch metric associated with a received symbol of said input bit of a data transmission stream; and calculate an additional weight parameter for said received symbol based only on extrinsic hard information; and a sixth component adapted to compute a revised branch metric by combining said initial branch metric and said additional weight parameter.