New stopping criterion for turbo code in the presence of SNR mismatch

This paper proposes a new stopping criterion for turbo codes which is derived by observing the role of the unreliable bits in the received sequence. The proposed criterion computes the mean of inverse absolute LLR values and compares it with a pre-defined threshold to decide whether further iteration is needed or not. The simulations in different situations show that this criterion outperforms ME and is close to CE but with much less computational complexity. The performance of the proposed stopping criterion has been also simulated in the presence of SNR mismatch and shown that it is much better than ME and interestingly it is still close to CE even closer than the case when SNR is exact especially in low constraint length.