基于衰落信道的数字喷泉码仿真及优化

发布时间：2018-04-16 06:35

本文选题：喷泉码 + 衰落信道　；参考：《西安电子科技大学》2014年硕士论文

【摘要】：随着无线通信技术的快速发展,信道编码作为一种重要的差错控制技术,在数字通信系统有着越来越深远的作用。数字喷泉码是一种新型的、无码率的、简单高效的编码方案。它具有很强的鲁棒性,能够适应各种信道状态。采用数字喷泉码还可以避免使用自动重发请求机制,保证信号传输的可靠性。本文主要研究了数字喷泉码在衰落信道下的性能及其优化方法,结论如下:1.采用Raptor码长码,BIAWGN的信道容量满足Cap?BIAWGN????=R?1?????R,其中???0是实际接收数量与最佳接收数量的差值所占的比例。??接近于0,说明在BIAWGN下,采用Raptor码长码,可以实现近理想的性能。2.信道交织器是抗突发错误和瑞利衰落的常用方法。信道交织器可以打乱编码符号的顺序,以降低相邻符号所受噪声的相关性。若慢衰落的衰落速率非常小,编码序列又短,一个衰落周期内有多个编码序列,则喷泉码有严重的块衰落。此时,可以考虑块间交织器,组合多个编码序列通过信道交织器。3.求解最优化方程,对LT码和Raptor码进行优化,可以计算任意长度的、优化的喷泉码的度分布函数。给出了LT码的度分布函数,构造opt-Raptor码,并与RSD-LT码做详细比较。4.基于生成矩阵的软判决BP译码,迭代过程是在某个固定次数后停止的。在信道状况良好时,固定迭代次数会浪费译码时间。基于生成矩阵的BP译码的迭代终止条件,可以减少其迭代次数而保持原有性能。
[Abstract]:With the rapid development of wireless communication technology, channel coding, as an important error control technology, plays a more and more far-reaching role in digital communication systems.Digital fountain code is a new coding scheme, which has no code rate and is simple and efficient.It has strong robustness and can adapt to various channel states.Digital fountain code can also avoid the use of automatic retransmission request mechanism to ensure the reliability of signal transmission.In this paper, the performance and optimization of digital fountain codes in fading channels are studied. The conclusions are as follows: 1.The channel capacity of BIAWGN using Raptor code length code can meet the requirements of Raptor BIAWGN, where the ratio of the difference between the actual number of received and the optimum number of receivers.Close to 0, it shows that the near ideal performance. 2. 2 can be achieved by using Raptor code length code under BIAWGN.Channel Interleaver is a common method to resist burst error and Rayleigh fading.The channel Interleaver can disrupt the sequence of coded symbols to reduce the correlation of noise to adjacent symbols.If the fading rate of slow fading is very small, the coding sequence is short, and there are more than one coding sequence in a fading period, the fountain code has serious block fading.At this point, interblock interleavers can be considered, combining multiple coding sequences through channel interleavers. 3.By solving the optimization equation and optimizing the LT code and Raptor code, the degree distribution function of the optimized fountain code of any length can be calculated.The degree distribution function of LT code is given, the opt-Raptor code is constructed and compared with RSD-LT code in detail.The iterative process of soft decision BP decoding based on generating matrix is stopped after a fixed number of times.When the channel is in good condition, a fixed number of iterations will waste decoding time.The iterative termination condition of BP decoding based on generating matrix can reduce the number of iterations and maintain the original performance.
【学位授予单位】：西安电子科技大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TN911.22

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