【作者】 杨海芬；

【导师】 靳蕃；

【作者基本信息】 西南交通大学 ， 通信与信息系统， 2003， 硕士

【摘要】 Turbo码，又称并行级联卷积码（PCCC），是由C.Berrou等在1993年ICC会议上提出的。当时的模拟结果表明，如果采用大小为65535的随机交织器，并且进行18次迭代，则在E_b/N_o≥0.7dB时，码率为1/2的Turbo码在AWGN信道上的误比特率（BER）≤10^-5，达到了近Shannon限的性能。尽管目前对Turbo码算法性能还缺乏有效的理论解释，但Turbo码已经被看作自1982年TCM技术问世以来信道编码理论上一项伟大的技术成就，而且它重要的编译码思想正引起众多学者的关注和兴趣。 本文对Turbo码的研究工作主要集中在以下几个方面： 对Turbo码的编译码方法进行研究。Turbo码是建立在一种特殊的系统卷积码的基础上的，它以两个RSC码作为它的分量码，因此分量码的选取对Turbo码的性能有重要的影响。本文主要使用了16状态的（37，21）原始码型和8状态的（15，13）码型。Turbo码的译码算法主要有MAP算法和SOVA算法两大类，本文重点研究了前者。 研究了几种在MAP算法基础上的改进算法。由于MAP算法存在巨大的计算量和时延，为了克服MAP算法的缺点，研究了MAP算法的对数域内的简化算法Log-MAP算法以及滑动窗MAP算法。为了避免短帧情况下trellis的结束带来的译码性能的降低，本文把一种新颖的MAP译码结构应用到Log-MAP中并进行了计算机模拟，模拟结果表明短帧情况下这种新结构的译码方法在性能方面略有改进。 交织器对于Turbo码的性能有重大的影响，文中给出了Turbo码交织器的设计原则，对几种常用的Turbo码交织器的原理和实现方法进行了研究，进行了计算机模拟并对其性能进行了分析比较。 其它诸如trellis结尾问题、删余矩阵的设计、TCM调制等方面，本文给出了初步介绍，详细可查阅文献。 Turbo码现在正得到越来越广泛的应用，但是由于理论的缺乏和算法的时延性，使Turbo码的实际应用受到一定的限制。本文考虑了适合于短帧情况下Turbo码的设计方法，并得到较好的结果。更多还原

【Abstract】 Turbo code, also named parallel concatenated convolution code , was presented by C.Berrou, A. Glavieux and P.Thifimajshiwa in ICC’93 . According to the simulation results Turbo code can approach the Shannon bound with iteratively processed maximum-a-posteriori decoders . Because of its excellent performance , Turbo code is considered one of the most exciting and potentially important developments in coding theory in many years. Now Turbo code is widely applied in mobile communication and personal communication .The thesis investigates some aspects of Turbo code with emphasis on the improvement of the decoding algorithm and the design of the interleaver. The main results are below.The principles of Turbo code coding and decoding are described. Simulation are conducted employing 16 and 8 states constituent codes such as (37,21)RSC and (15,13)RSC. There are two sorts of decoding methods : MAP algorithm and SOVA algorithm and the thesis emphasizes the former.Several improved decoding algorithms are discussed including Log-MAP algorithm and sliding window MAP algorithm . And a new decoding structure is presented to avoid the decreasing of the decoding performance in case of the end of trellis. Simulation results show that the new algorithm has improved the performance of Turbo code in transmission of short frames.The interleaver is very important for Turbo code , and its design is described in the thesis. Several kinds of interleavers are studied , and their implementation methods are proposed . The influence of different interleavers on the performance of Turbo code is developed.The thesis also gives a simple introduction about the end of trellis , the design of puncture matrix and TCM technology , etc.Though Turbo code is becoming more and more popular , its practical application is limited because of absence in theory and time delay in algorithm . The thesis developed some suitable methods for short frames and gets a better performance at a certain level.更多还原