Trellis-coded modulation with redundant signal sets Part I: Introduction
Trellis-coded modulation with redundant signal sets Part I: Introduction
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DOI：
10.1109/mcom.1987.1093542
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发表时间：
1987-02
影响因子：
11.2
通讯作者：
G. Ungerboeck
中科院分区：
文献类型：
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作者：
G. Ungerboeck
瑞利编码调制（TCM）在过去的十年中已经发展成为用于在带限信道上进行数字传输的组合编码和调制技术。它的主要吸引力来自于这样一个事实，即它允许实现显着的编码增益超过传统的未编码的多级调制，而不影响带宽效率。第一个TCM方案于1976年提出[1]。在1982年更详细的出版物[2]之后，中医的研究和实际实施发生了爆炸，今天对中医方法的理论和能力有了很好的理解。在这篇由两部分组成的文章的第一部分，介绍了中医。回顾了中医药发展的原因，并讨论了简单的中医药方案的例子。第I1部分[I51]提供了对代码设计和性能的进一步了解，并解决了以下问题。中医药的最新进展TCM方案采用冗余非二进制调制与有限状态编码器的组合，该有限状态编码器控制调制信号的选择以生成编码信号序列。在接收端，噪声信号由软判决最大似然序列解码器解码。简单的四态TCM方案可以改进。与传统的未编码调制相比，数字传输对加性噪声的鲁棒性提高了3 dB。对于更复杂的TCM方案，编码增益可以达到6dB或更高。这些增益是在没有带宽扩展或降低有效信息速率的情况下获得的，而传统的纠错方案是需要这样做的。香农的信息理论在三十多年前就预测了具有这些特性的编码调制方案的存在。有效的中医技术的发展和今天的信号处理技术现在允许在实践中获得这些收益。如果表示信息序列的信号波形彼此非常不同，则它们最不受噪声引起的检测误差的影响。从数学上讲，这转化为信号序列在欧几里得信号空间中应该具有大距离的要求。TCM的本质新概念是利用信号集扩展为编码提供冗余，并联合设计编码和信号映射函数，以直接最大化编码信号序列之间的“自由距离“（最小欧几里德距离）。这使得调制码的自由距离大大超过未编码调制信号之间的最小距离，在相同的信息速率，带宽和信号功率的建设。术语“...
rellis-Coded Modulation (TCM) has evolved over the past decade as a combined coding and modulation technique for digital transmission over band-limited channels. Its main attraction comes from the fact that it allows the achievement of significant coding gains over conventional uncoded multilevel modulation without compromising bandwidth efficiency. T h e first TCM schemes were proposed in 1976 [I]. Following a more detailed publication [2] in 1982, an explosion of research and actual implementations of TCM took place, to the point where today there is a good understanding of the theory and capabilities of TCM methods. In Part 1 of this two-part article, an introduction into TCM is given. T h e reasons for the development of TCM are reviewed, and examples of simple TCM schemes are discussed. Part I1 [I51 provides further insight into code design and performance, and addresses. recent advances in TCM. TCM schemes employ redundant nonbinary modulation in combination with a finite-state encoder which governs the selection of modulation signals to generate coded signal sequences. In the receiver, the noisy signals are decoded by a soft-decision maximum-likelihood sequence decoder. Simple four-state TCM schemes can improve. the robustness of digital transmission against additive noise by 3 dB, compared to conventional , uncoded modulation. With more complex TCM schemes, the coding gain can reach 6 dB or more. These gains are obtained without bandwidth expansion or reduction of the effective information rate as required by traditional error-correction schemes. Shannon's information theory predicted the existence of coded modulation schemes with these characteristics more than three decades ago. T h e development of effective TCM techniques and today's signal-processing technology now allow these ,gains to be obtained in practice. Signal waveforms representing information sequences ~ are most impervious to noise-induced detection errors if they are very different from each other. Mathematically, this translates into therequirement that signal sequences should have large distance in Euclidean signal space. ~ T h e essential new concept of TCM that led to the afore-1 mentioned gains was to use signal-set expansion to I provide redundancy for coding, and to design coding and ' signal-mapping functions jointly so as to maximize ~ directly the " free distance " (minimum Euclidean distance) between coded signal sequences. This allowed the construction of modulation codes whose free distance significantly exceeded the minimum distance between uncoded modulation signals, at the same information rate, bandwidth, and signal power. The term " …