State metrics based stopping criterion for turbo-decoding

摘要

A stopping criterion for a turbo-encoding method. The criterion is based on a state metrics calculated by a forward-backward recursion in a coding trellis of an elementary encoder. If, for at least one elementary decoding stage, forward state metrics of a last symbol of a block or backward state metrics of a first symbol of a block exceeds a first threshold, the turbo-decoding iterations are stopped. If it is not the case, it is further checked whether the state metrics exceeds a second threshold and if the absolute value of the difference between the current state metrics and the state metrics obtained at the previous iteration lies below a given margin. In the affirmative, the turbo-decoding iterations are stopped and a hard decision is taken on extrinsic values.