Half-iteration early termination of turbo decoding

Early stopping (ES) methods reduce the average number of iterations required for decoding turbo codes. These methods monitor the generated outputs along the iterations to terminate the loop once this output reaches a satisfactory level of reliability. It is the norm among the published ES methods to be applied after the output of the second decoder becomes available. In other words, an iteration index includes both decoders. In this paper, we propose a more efficient way to apply an ES method. This improvement relies on the fact that almost any ES check can be executed twice per iteration, i.e., after each decoder instead of after only the second one. In all the cases, the used ES algorithm considers the two most recent outputs from the constituent decoders. Results show further reduction in the average iterations for the decoding, which is practically important for conserving decoding resources.