Turbo码并行译码算法的研究

Turbo码的译码算法大致可分为串行译码算法和并行译码算法两大类。串行译码算法如MAP、LOG-MAP等的研究已比较深入。但并行译码算法，尚有许多问题有待探讨。研究了Turbo码的并行译码算法，将Turbo码译码和图论结合起来，利用Bayesian网络图模型描述了Turbo码的译码过程，基于模型使用Pearl的信息传播算法，建立了Turbo码的并行译码算法。并对所讨论的并行译码算法进行了模拟，模拟结果表明：该并行译码在译码性能等方面比串行译码优越。     

不规则重复累积码的分析与仿真

本文主要研究非规则重复累积码(Irregular RepeatAccumulate,IRA码)的编译码原理。着重整理与实现了IRA码的编译码方法 ,对IRA码译码算法进行了研究。最后,对IRA码进行矩阵整理、仿真和分析,从而得出该码编译码性能以及相应的分析结果。     

Turbo码Log-MAP算法的SNR自适应估计和失配

对Turbo码的Log-MAP译码算法进行了分析，与其他算法进行了比较，分析了信噪比失配对Turbo码译码性能的影响，在此基础上着重探讨了自适应信噪比估计器估计SNRD的方法，并对此进行了模拟仿真。     

LDPC译码方法研究及实现

本文主要研究了低密度校验码（LDPC码）的编译码方法及其硬件实现。在讨论几种主要的LDPC码的编译码方法的基础上，对LDPC译码错误产生原因进行了分析，提出了一种改进的置信传播译码算法——最小和算法，该算法在几乎没有增加运算复杂度的情况下，明显地提高了译码性能。同时，本文基于几何思想的LDPC码为例，提出了并串结合的FPGA实现方法，给出了仿真结果。     

低密度校验码量化译码研究

介绍了基于置信传播算法的LDPC码和积译码算法，分析其密度进行化特性，对不同消息空间中的量化译码问题进行研究，对采用不同量化方案时LDPC码在AWGN信道下的译码性能进行了仿真。仿真结果表明相对连续译码，中间变量6bit均匀量化会带来约0．4dB左右的损失，而10bit非均匀量化性能明显得到改善。合适的高阶量化译码可以获得接近连续译码的性能。     

探讨数据通信中差错控制编译码（RS码）的软件算法

本文在较为具体地分析了RS码原理与性质的基础上，详细地推导了实现RS码编码、译码的算法过程，并通过实例对编码、译码的算法进行了数据验证。     

基于MATLAB的Turbo码译码算法研究分析

Turbo码的发展对编码理论以及研究方法造成了较大的推动作用,使得信道编码学进入了新的阶段。文章主要探讨的是基于MATLAB的Turbo码译码算法研究,全文在具体分析中主要从Turbo码编译码结构、Turbo码常用迭代译码算法分析以及对比研究、基于MATLAB的Turbo码译码不同译码算法对Turbo码能的影响等方面进行了全面的分析。     

纠正随机错误与长突发删除的多进制乘积码研究

考虑多进制LDPC码的符号特性，以及对其残留错误和删除的分析，本文采用多进制LDPC码作为内码，相同Galois域下的高码率RS码作为外码来构造多进制乘积码；并提出了一种低复杂度的迭代译码方案，减少信息传输的各类错误。在译码时，只对前一次迭代中译码失败的码字执行译码，并对译码正确码字所对应的比特初始概率信息进行修正，增强下一次迭代多进制LDPC译码符号先验信息的准确性，减少内码译码后的判决错误，从而充分利用外码的纠错能力。仿真结果显示，多进制乘积码相较于二进制LDPC乘积码有较大的编码增益，并通过迭代进一步改善了性能，高效纠正了信道中的随机错误和突发删除。对于包含2%突发删除的高斯信道，在误比特率为10-6时，迭代一次有0.4 dB左右的增益。      

级联码译码在PC平台上的实现

对清华小卫星地面应用系统级联码译码的研制进行较详细的阐述，比较各种实现的途径，并详细介绍如何利用PC机方法来实现该级联码译码。分别从硬件和软件，数据接收和数据处理的不同角度对其进行介绍，并对卷积码的Viterbi译码，RS码的Berlekamp迭代译码算法以及数据的加扰解扰作了简要的介绍。     

基于循环冗余校验的极化码研究

极化码具有简单明确的编码方式和译码算法,在理论上被证明可以达到香农极限。但是其连续删除译码(SC译码)始终在单路径上逐比特进行译码,导致其实际译码性能并不理想。连续删除列表译码(SCL译码)是SC译码的改进型算法,这种译码方式以付出一定译码复杂度为代价提高了极化码的译码性能。而将SCL译码结合循环冗余校验(CRC)可以译码多路径中错误译码的概率,基于这一点该文将对不同CRC码结合极化码所产生的性能差异进行分析,从而得到合适的CRC     

改进Min-sum的LDPC译码算法研究

为了弥补Min-Sum译码算法相对于LLR-BP算法的性能缺陷,降低LLR-BP算法的实现复杂度,提出一种改进型Min-Sum译码算法,将Normalized BP-Based和Offset BP-Based 2种算法有效地结合,在计算校验节点消息时,同时引进校正因子和偏移因子,并通过最小均方差准则来选择参数。仿真结果表明,在误码率相同的条件下,改进型Min-Sum译码算法比Min-Sum算法、Normalized BP-Based算法和Offset BP-Based算法具有更好的译码性能,译码性能逼近于LLR-BP译码算法。     

DTS音频文件软件解码的实现

介绍了DTS音频文件的解码标准，给出了软件解码需要的开发环境和解码流程，对3个DTS音频文件的软件解码结果进行了分析，最后列举了在编写DTS音频文件解码软件过程中需要注意的一些问题。     

On algebraic soft-decision decoding algorithms for BCH codes

Three algebraic soft-decision decoding algorithms are presented for binary Bose-Chaudhuri-Hocquengham (BCH) codes. Two of these algorithms are based on the bounded distance (BD)+1 generalized minimum-distance (GMD) decoding presented by Berlekamp (1984), and the other is based on Chase (1972) decoding. A simple algebraic algorithm is first introduced, and it forms a common basis for the decoding algorithms presented. Next, efficient BD+1 GMD and BD+2 GMD decoding algorithms are presented. It is shown that, for binary BCH codes with odd designed-minimum-distance d and length n, both the BD+1 GMD and the BD+2 GMD decoding algorithms can be performed with complexity O(nd). The error performance of these decoding algorithms is shown to be significantly superior to that of conventional GMD decoding by computer simulation. Finally, an efficient algorithm is presented for Chase decoding of binary BCH codes. Like a one-pass GMD decoding algorithm, this algorithm produces all necessary error-locator polynomials for Chase decoding in one run     

基于MHC快速译码算法的译码树的构造方法

在传真通信中需要对数据进行压缩后再发送。一维改进的Huffman码（MHC）是在传真通信中使用较多的一种压缩编码。MHC的译码算法和快速译码算法都是通过构造译码树实现译码,但将译码树的码表应用到线性地址空间上时,都存在一定程度冲突,从而会对译码速度产生影响。文中通过对MHC快速译码算法的分析,提出了一种新的译码树构造方法,实现了在线性地址空间上对译码树的构造,并解决了原方法中的冲突问题。     

Universal decoding for finite-state channels

Universal decoding procedures for finite-state channels are discussed. Although the channel statistics are not known, universal decoding can achieve an error probability with an error exponent that, for large enough block length (or constraint length in case of convolutional codes), is equal to the random-coding error exponent associated with the optimal maximum-likelihood decoding procedure for the given channel. The same approach is applied to sequential decoding, yielding a universal sequential decoding procedure with a cutoff rate and an error exponent that are equal to those achieved by the classical sequential decoding procedure.     

Performance of a new decoding method used in open-loop all-optical chaotic communication system

A new decoding method with decoder is used in open-loop all-optical chaotic communi-cation system under strong injection condition. The performance of the new decoding method is nu-merically investigated by comparing it with the common decoding method without decoder. For new decoding method, two cases are analyzed, including whether or not the output of the decoder is ad-justed by its input to receiver. The results indicate the decoding quality can be improved by adjusting for the new decoding method. Meanwhile, the injection strength of decoder can be restricted in a certain range. The adjusted new decoding method with decoder can achieve better decoding quality than decoding method without decoder when the bit rate of message is under 5 Gb/s. However, a stronger injection for receiver is needed. Moreover, the new decoding method can broaden the range of injection strength acceptable for good decoding quality. Different message encryption techniques are tested, and the result is similar to that of the common decoding method, indicative of the fact that the message encoded by using Chaotic Modulation (CM) can be best recovered by the new decoding method owning to the essence of this encryption technique.     

迭代检测算法在比特交织编码调制系统中的比较研究

迭代检测技术不仅局限于在传统的级联码系统中的应用,还可用于解决现代数字通信中的许多检测／译码问题。随着Turbo码的出现,人们对迭代译码算法进行深入研究,并提出一些简化译码算法。比特交织编码调制及迭代检测（bit—interleaved coded modulation with iterative decoding,BICMID）是一种高效数据传输系统。比特交织和迭代译码是BICM—ID系统具有卓越性能的关键因素,译码算法的选择不仅影响接收机的性能,也决定了系统的复杂度。文中研究迭代译码算法对BICM—ID系统性能的影响,分析各种译码算法的计算复杂度。仿真结果表明log-APP算法有好的性能同时复杂度也高,简化的译码算法能降低译码器的复杂度,但会带来一定的性能损失;随着信道条件的改善,算法简化带来的性能损失也随之减小。     

Multistage decoding of multilevel block M-PSK modulationcodes and its performance analysis

Multistage decoding of multilevel block multilevel phase-shift keying (M-PSK) modulation codes for the additive white Gaussian noise (AWGN) channel is investigated. Several types of multistage decoding, including a suboptimum soft-decision decoding scheme, are devised and analyzed. Upper bounds on the probability of an incorrect decoding of a code are derived for the proposed multistage decoding schemes. Error probabilities of some specific multilevel block 8-PSK modulation codes are evaluated and simulated. The computation and simulation results for these codes show that with multistage decoding, significant coding gains can be achieved with large reduction in decoding complexity. In one example, it is shown that the difference in performance between the proposed suboptimum multistage soft-decision decoding and the single-stage optimum decoding is small, only a fraction of a dB loss in SNR at the block error probability of 10^-6     

Algebraic Soft-Decision Decoding of Reed–Solomon Codes Using Bit-Level Soft Information

The performance of algebraic soft-decision decoding of Reed–Solomon codes using bit-level soft information is investigated. Optimal multiplicity assignment strategies for algebraic soft-decision decoding (SDD) with infinite cost are first studied over erasure channels and the binary-symmetric channel. The corresponding decoding radii are calculated in closed forms and tight bounds on the error probability are derived. The multiplicity assignment strategy and the corresponding performance analysis are then generalized to characterize the decoding region of algebraic SDD over a mixed error and bit-level erasure channel. The bit-level decoding region of the proposed multiplicity assignment strategy is shown to be significantly larger than that of conventional Berlekamp–Massey decoding. As an application, a bit-level generalized minimum distance decoding algorithm is proposed. The proposed decoding compares favorably with many other Reed–Solomon SDD algorithms over various channels. Moreover, owing to the simplicity of the proposed bit-level generalized minimum distance decoding, its performance can be tightly bounded using order statistics.      

基于预译码的极化码最大似然简化连续消除译码算法

针对极化码译码串行输出造成较大译码时延的问题,该文提出一种基于预译码的最大似然简化连续消除译码算法。首先对译码树节点存储的似然值进行符号提取并分组处理,得到符号向量组;然后比较符号向量组与该节点的某些信息位的取值情况,发现向量组中储存的正负符号分布规律与该节点的中间信息位的取值具有一一对应的关系;在此基础上对组合码中间的1～2 bit进行预译码;最后结合最大似然译码方法估计组合码中的剩余信息位,从而得到最终的译码结果。仿真结果表明:在不影响误码性能的情况下,所提算法与已有的算法相比可有效降低译码时延。