Abstract: The Chase2 algorithm is one of the soft-decision decoding algorithms of Turbo Product Code (TPC). The conventional Chase2 algorithm needs a large amount of computation to calculate the Euclidean distance and search for competing codeword, so it is complex to implement in the hardware. Therefore, on the basis of the conventional Chase2 algorithm, the correlation was substituted as the metric for the Euclidean distance and the process of searching for competing codeword was simplified to reduce the decoding complexity; and the soft-output value was adjusted when there was no competing codeword to improve the coding gain. The simulation results show that, compared with the conventional algorithm, the modified algorithm has better performance and faster decoding speed, and it is suitable for hardware implementation.

Key words: Turbo Product Code (TPC), Chase2 algorithm, soft-decision decoding, channel coding gain, complexity

摘要： Chase2算法是Turbo乘积码(TPC)软判决译码中常采用的算法之一。由于传统的Chase2算法中欧氏距离计算以及寻找竞争码字都需要大量的运算，因而在硬件上实现比较复杂。为此，在传统Chase2算法的基础上，采用相关度量等价替代欧氏距离的度量，简化寻找竞争码字的过程，以降低译码复杂度;调整竞争码字不存在时的软输出信息值，以提高编码增益。仿真结果表明：改进算法比传统的Chase算法译码速度更快，译码性能更好，非常适合硬件实现。

关键词: Turbo乘积码, Chase2算法, 软判决译码, 信道编码增益, 复杂度