Bit-level stopping in turbo decoding

In turbo decoding, the reliability of each bit in a frame converges at a different speed, i.e. some bits converges faster than others. This motivates to propose a bit-level stopping criterion that prevents unnecessary iterations for those bits reliable enough. Simulation results show that the proposed bit-level stopping reduces the average number of iterations more than the conventional frame-level stopping while achieving the same bit error rate. The proposed bit-level stopping is particularly effective for fading channels. We also propose two efficient reliability measures that take that convergence of soft outputs and the reliability of decision into account.