中文摘要
Turbo码。它的主要特点在于编码器之间引入了交织和迭代译码。
图2-1所示是典型的Turbo码编码器结构框图,为了克服MAP算法的缺点,was presented byC.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,and their implementation methods are proposed .The influence of different interleavers on the performance of Turbo code is developed.
Keywords:Turbo code,and its design is described in the thesis. Several kinds of interleavers are studied,Turbo码交织器
Abstract
Turbo code, also named parallel concatenated convolution code,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 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,Turbo code interleaver
Turbo码是1993年由Berrou提出的一种新的编码方案。u和 ,但Turbo码己经被看作自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,从而产生不同码率的码字。u和 ,但比特位置经过重新排列)。
Turbo码编码器是由两个反馈的系统卷积码编码器通过一个随机交织器并行级连而成,但比特位置经过重新排列)。通过在分量码译码器之间传递外部信息,使Turbo码的性能逼近Shannon限。分量码采用RSC码,使Turbo码的译码可以由简单的分量码的译码迭代而成。迭代译码降低了Turbo码的译码复杂度,充分利用了接收到的信息,信息序列 经过N位交织器,信息序列 经过N位交织器,使在第一个编码器中产生小重量校验序列的信息序列在第二个编码器中以很大的概率产生大重量校验序列。
第1章绪论 3
1.1数字通信系统的组成及信道编码定理 3
1.2功率受限信道编码技术 5
第2章 Turbo码编译码研究 5
2.1Turbo码概述 5
2. 2 Turbo码编码及其分量码 6
2. 3分量码的最大后验概率译码(MAP算法) 7
2. 4SOVA译码算法 9
2. 5不同信道下Turbo码的译码修正 11
第3章Turbo码译码方式的修正算法 11
3. 1改进的滑动窗最大后验(MAP)译码 12
3.2基于短帧的一种新结构的Log-MAP方式 12
3. 2. 1 Turbo码的Trellis结束问题 12
3. 2. 2 一种新结构的Log-MAP方式 13
第4章Turbo码的其它技术 14
4. 1 Turbo码交织器的作用和设计 14
(优秀毕业设计 )
4. 2几种常用的Turbo码交织器的设计与实现 14
4. 2. 1行列交织器 14
4. 2. 2伪随机交织器 14
4. 2. 3固定交织器 15
4. 2. 4几种交织器的性能模拟和分析 16
第5章 Turbo编码器仿真——CDMA200系统Turbo编码器 17
5.1 Turbo编码器原理 17
5.2Turbo编码器的实现 18
结束语 22
参考文献 24
致谢 25