Exploiting The Turbo Principle

近年来，Turbo编码已经成为一种强大的前向差错控制编码范型。虽然Turbo编码仍然是新的，但它在各种应用中的广泛应用证明了Turbo编码的成功，包括深空通信、卫星通信和数字蜂窝通信。这一成功背后的关键是优雅的迭代解码器，它以合理的实现复杂性接近理论极限。最近，迭代译码结构被抽象并推广到现在所知的Turbo原理。由于其卓越的性能，预计Turbo原理将对数字通信系统的几乎所有方面产生巨大影响。这项研究的主要目的是探索Turbo原理的基本极限，同时提供实际实现。第一个研究重点是开发一种计算Turbo译码收敛门限的解析方法。除了预期的计算复杂性节省外，分析方法还试图为代码设计提供更有用的见解。收敛分析将有助于构造接近加性高斯白噪声(AWGN)信道容量极限的非规则类Turbo码。小块长和中等块长的码性能将被作为额外的设计准则。本研究还将研究多径衰落信道的图形码设计。码结构将针对参数衰落模型进行优化，以捕捉实际系统中的不同限制。此外，收敛分析将被用于探索广义衰落信道中Turbo多用户接收机性能的基本极限。

In recent years, Turbo coding has emerged as a powerful forward error control coding paradigm. Although still new, the success of Turbo coding is witnessed by its widespread use in a variety of applications, including deep space communication, satellite communication, and digital cellular communication. The key behind this success is the elegant iterative decoder that approaches theoretical limits with reasonable implementation complexity. More recently, the iterative decoder structure was abstracted and generalized to what is now known as the Turbo Principle. Because of its remarkable performance, it is expected that the Turbo Principle will have an enormous impact on virtually all aspects of digital communication systems. The main goal of this research is to explore the fundamental limits of the Turbo Principle while offering practical implementations.The first research thrust aims at developing an analytical approach for computing the convergence thresholds of Turbo decoders. In addition to the expected savings in computational complexity, the analytical approach is sought to offer more useful insights for code design. The convergence analysis will facilitate constructing irregular ``Turbo-like" codes that approach the capacity limit of Additive White Gaussian Noise (AWGN) channels. The code performance with small and moderate block lengths will be considered as an additional design criterion. This research will also investigate graphical code design for multi-path fading channels. Code constructions will be optimized for parametric fading models that capture the different limitations in practical systems. Furthermore, The convergence analysis will be used to explore fundamental limits on the performance of Turbo multi-user receivers in generalized fading channels.