接近香农极限的信道编码与FPGA实现

发布时间：2018-04-21 22:17

本文选题：极化码 + QC-LDPC码　；参考：《南京航空航天大学》2014年硕士论文

【摘要】：自从Shannon定理被提出以来,寻找性能能够接近甚至达到Shannon极限的信道编码一直是通信领域研究的热点之一。极化码是目前发现的性能最接近Shannon极限的一种信道编码,它是由Arikan提出的。极化码的优越性能在理论上得到了严格的证明,但在实际应用中还存在一些问题,需要进一步探索研究。而目前被广泛使用的是LDPC码,这是由Gallarger博士在1962年提出的一种信道编码,但由于实际条件所限,直到90年代才被广泛研究与应用。由于LDPC码具有非常好的性能,且实现方式简单高效,因此得到了广泛的重视与研究,并且已经成为第四代移动通信、卫星通信、网络数据传输等强有力的竞争者。QC-LDPC码是LDPC码的一个子类,由于具有准循环特性,因此它的编码与译码都可以用硬件高效实现。本文首先主要研究了信道的合并与拆分过程,然后基于此分析了信道的极化过程,并给出信道极化的示意图,以及在高斯信道下进行仿真得到的性能曲线。可以看出极化码是基于信道极化过程传输信息的,且性能优越。其次简单介绍了LDPC码通用的编码过程,并给出了针对QC-LDPC码准循环结构的块编码过程。然后进一步研究了QC—LDPC码的随机构造过程,详细介绍了消除4环与6环的过程。文章也给出了各自的性能比较,并构造了一个本文硬件实现中的码字。然后研究了LDPC码的几种软判决译码算法,并对其译码的性能进行了详细的分析,给出了不同的软件仿真结果对比,并确定了算法的修正因子。最终确定在硬件实现中采用基于归一化算法的分层译码算法,并对其中所有的软信息数据采用6bits量化处理。最后分析了LDPC码译码器的多种结构,确定本文的设计中采用分层译码结构,并详细介绍了各个子模块的实现功能,然后运用verilog硬件描述语言完成整个译码器的设计。使用Quartus软件在Alter公司的EP3SL340H1152I4芯片上完成译码器的布局布线与综合优化,并调用Modelsim软件完成译码器时序的仿真。在设定时钟频率为50MHZ,迭代5次的情况下,译码器达到了79.5Mbps的吞吐率。
[Abstract]:Since the Shannon theorem was proposed, it has been one of the hotspots in the field of communication to find channel coding that can reach or even reach the Shannon limit. Polarization code is one of the channel codes which is found to be the closest to the limit of Shannon. It is proposed by Arikan. The superior performance of polarization codes has been proved strictly in theory, but there are still some problems in practical applications, which need to be further explored. At present, LDPC codes are widely used, which was proposed by Dr. Gallarger in 1962. However, due to the limitation of practical conditions, it was not widely studied and applied until the 1990s. Because of its excellent performance and simple and efficient implementation, LDPC code has been paid more and more attention, and has become the fourth generation mobile communication and satellite communication. QC-LDPC code is a subclass of LDPC code, which is a strong competitor such as network data transmission. Because of its quasi-cyclic property, its coding and decoding can be implemented efficiently by hardware. In this paper, the process of channel merging and splitting is studied, then the polarization process of the channel is analyzed, and the schematic diagram of channel polarization and the performance curve obtained by simulation under Gao Si channel are given. It can be seen that the polarization code transmits information based on the channel polarization process, and its performance is superior. Secondly, the general coding process of LDPC codes is briefly introduced, and the block coding process for quasi-cyclic structure of QC-LDPC codes is given. Then the random construction process of QC-LDPC codes is studied, and the process of eliminating 4 rings and 6 rings is introduced in detail. This paper also gives a comparison of their performance and constructs a codeword in the hardware implementation of this paper. Then, several soft decision decoding algorithms for LDPC codes are studied, and their decoding performance is analyzed in detail. The results of different software simulations are compared, and the correction factors of the algorithms are determined. Finally, the hierarchical decoding algorithm based on normalization algorithm is adopted in hardware implementation, and all soft information data are processed by 6bits quantization. Finally, this paper analyzes the various structures of the LDPC decoder, determines that the layered decoding structure is adopted in the design of this paper, and introduces the implementation functions of each sub-module in detail. Then, the design of the decoder is completed by using the verilog hardware description language. The Quartus software is used to complete the layout, wiring and synthesis optimization of the decoder on the EP3SL340H1152I4 chip of Alter Company, and the time sequence simulation of the decoder is completed by using Modelsim software. When the clock frequency is 50 MHz and the iteration is 5 times, the decoder achieves the throughput of 79.5Mbps.
【学位授予单位】：南京航空航天大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TN911.22;TN791

【参考文献】