This paper proposes a new soft-input soft-output decoding algorithm particularly suited for low-complexity high-radix turbo decoding, called local soft-output Viterbi algorithm (local SOVA). The local SOVA uses the forward and backward state metric recursions just as the conventional Max-Log-MAP algorithm does, and produces soft outputs using the SOVA update rules. The proposed local SOVA exhibits a lower computational complexity than the Max-Log-MAP algorithm when employed for high-radix decoding in order to increase throughput, while having the same error correction performance even when used in a turbo decoding process. Furthermore, with some simplifications, it offers various trade-offs between error correction performance and computational complexity. For instance, employing the local SOVA algorithm for radix-8 decoding of the LTE turbo code reduces the complexity by 33% without any performance degradation and by 36% with a slight penalty of only 0.05 dB. Moreover, the local SOVA algorithm opens the door for the practical implementation of turbo decoders for radix 16 and higher.

中文翻译：

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使用 SOVA 更新规则重新审视 Max-Log-Map 算法：高基数 SISO 解码器的新简化

本文提出了一种新的软输入软输出解码算法，特别适用于低复杂度的高基涡轮解码，称为局部软输出维特比算法（local SOVA）。本地 SOVA 使用前向和后向状态度量递归，就像传统的 Max-Log-MAP 算法一样，并使用 SOVA 更新规则产生软输出。当用于高基数解码以增加吞吐量时，所提出的局部 SOVA 表现出比 Max-Log-MAP 算法更低的计算复杂度，同时即使在涡轮解码过程中使用时也具有相同的纠错性能。此外，通过一些简化，它提供了纠错性能和计算复杂性之间的各种权衡。例如，采用本地 SOVA 算法对 LTE turbo 码进行 radix-8 解码将复杂度降低了 33%，而没有任何性能下降，降低了 36%，只有 0.05 dB 的轻微损失。此外，局部 SOVA 算法为基数 16 及更高的 turbo 解码器的实际实现打开了大门。