Patent ID: 7032156

Claim:
A constituent decoding method for decoding a turbo code, comprising the steps of: (1) calculating the best and second best metrics of metrics being the sums of state metrics and a branch metric for a received information symbol in a turbo decoding trellis at an arbitrary time point during turbo decoding of the information symbol; (2) calculating the difference between the best metric for the information symbol being 0 and the best metric for the information symbol being 1; (3) calculating the difference between the second best metric for the information symbol being 0 and the second best metric for the information symbol being 1; (4) calculating the difference between the best metric difference and the second best metric difference and multiplying the calculated difference by a weighting factor, so that the metrics being the sums of the state metrics and the branch metric are linear; and (5) updating the log likelihood ratio (LLR) of the information symbol using the best metric difference obtained in the step of (2) and the product obtained in the step of (4) and deciding the value of the information symbol according to the updated LLR.