Multilevel codes: Theoretical concepts and practical design rules
Multilevel codes: Theoretical concepts and practical design rules
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DOI：
10.1109/18.771140
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发表时间：
1999-07
期刊：
影响因子：
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通讯作者：
U. Wachsmann;R. Fischer;J. Huber
中科院分区：
文献类型：
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作者：
U. Wachsmann;R. Fischer;J. Huber
本文研究了采用多级编码（MLC）和多级译码（MSD）的二进制超高速传输。本文回顾了MLC和MSD在各层速率选择适当的情况下足以接近容量的已知结果。利用多用户信息理论，它表明，有一个大的空间的速率组合，使MLC和全最大似然解码（MLD）可以接近容量。值得注意的是，根据传统的平衡距离规则设计的多级码往往属于后一类，因此，需要巨大的复杂性MLD。比较了容量准则、平衡距离准则以及基于随机编码指数和截止率的两种准则，以供实际设计参考。使用多级二进制Turbo码的仿真结果表明，容量实际上可以接近高带宽效率。此外，在实际应用中的相关问题，如信号集标记，组成星座的维数，和硬判决解码的重点。由Caire等人提出的比特交织编码调制（参见同上，第44卷，第927 -46页，1998），在MLC的背景下进行综述。最后讨论了信号整形与编码的结合。只有考虑到这些设计规则，才能在实践中获得显著的成形增益。
This paper deals with 2/sup l/-ary transmission using multilevel coding (MLC) and multistage decoding (MSD). The known result that MLC and MSD suffice to approach capacity if the rates at each level are appropriately chosen is reviewed. Using multiuser information theory, it is shown that there is a large space of rate combinations such that MLC and full maximum-likelihood decoding (MLD) can approach capacity. It is noted that multilevel codes designed according to the traditional balanced distance rule tend to fall in the latter category and, therefore, require the huge complexity of MLD. The capacity rule, the balanced distances rules, and two other rules based on the random coding exponent and cutoff rate are compared and contrasted for practical design. Simulation results using multilevel binary turbo codes show that capacity can in fact be closely approached at high bandwidth efficiencies. Moreover, topics relevant in practical applications such as signal set labeling, dimensionality of the constituent constellation, and hard-decision decoding are emphasized. Bit interleaved coded modulation, proposed by Caire et al. (see ibid., vol.44, p.927-46, 1998), is reviewed in the context of MLC. Finally, the combination of signal shaping and coding is discussed. Significant shaping gains are achievable in practice only if these design rules are taken into account.