Turbo/MAP 编译码器中的交织器优化设计

Interleaver Design in Turbo/MAP Code

讨论采用软输出迭代译交织级联卷积码（Ｔｕｒｂｏ码）编译码器中的交织器优化设计问题．从基于最大后验概率（ＭＡＰ）算法与迭代译码的Ｔｕｒｂｏ码编译码原理出发，给出交织器设计的一些基本方法并分析其特点；提出“保奇偶”的随机交织器设计方案，它能有效地改善某些以提高编码效率为目的的“删余截短”Ｔｕｒｂｏ码的纠错性能．通过计算机仿真得出一些Ｔｕｒｂｏ码在加性高斯白噪声信道中采用不同交织器时的误码率数据，分析了交织类型和交织深度的变化对Ｔｕｒｂｏ码纠错性能的影响．针对Ｔｕｒｂｏ码的特点提出了在卫星通信等应用中交织器设计的实用性结论．

This paper discusses the optimal design of interleavers in a sort of interleaved concatenated convolutional codes with iterative soft output decoding (so called turbo codes). It briefly describes the principle of turbo codecs, which is based on the maximum a posterior(MAP) and iterative decoding algorithm, and presents some essential designing methods of the key part interleavers and their features analyses. Meanwhile, an “Odd and Even Position Preserved” random interleaver scheme is proposed, which can effectively improve the performance of some rate increased puncturing turbo codes. By means of computer simulation, it also gives out some bit error ratio data of turbo codes with different interleavers under the AGWN channel and observes the relation between code's error correcting performance and interleavers with different types or different interleaving depths. Finally, according to the characteristic of turbo codes, some practical conclusions about optimal design of interleavers in Turbo/MAP codecs are given for application such as satellite communications.