关键词: Turbo码, 译码, 迭代停止, 循环冗余校验准则, 可靠度, 重传, 阈值

Abstract:

Large iterations and errors may be caused by using the Cyclic Redundancy Check (CRC) criterion in decoding when channel condition gets worse. Thus, an iterative stopping algorithm based on reliability and a retransmission algorithm were proposed. First, the reliability of the intermediate result was calculated after each iteration, and it was used to achieve early stop of iteration by reaching a threshold. Second, the intermediate result corresponding to the maximum reliability was saved and used as the final result of decoding. Finally, after each decoding, the maximum reliability was used to determine whether to retransmit by being under a threshold of retransmission or not, and the best result of decoding was calculated by using results of no more than three transmissions. Simulations show that, when signal to noise ratio is less than 1.2 dB, in comparison with the CRC criterion, bit errors can be reduced by one or two on the basis of not increasing iterations by using this stopping algorithm, and bit errors can be further reduced by at least two by using the retransmission algorithm. The algorithm based on reliability can achieve less number of bit errors and iterations.

Key words: Turbo code, decoding, iterative stopping, Cyclic Redundancy Check (CRC) criterion, reliability, retransmission, threshold