面向电力线通信的RA码自适应迭代译码方法

为降低信息在强干扰电力线信道中传输的误码率,对重复累积（RA）码的置信传播（BP）译码算法进行改进。修正BP译码算法中信息节点的初始值,利用自适应迭代译码减少译码过程中的迭代次数,并对译码进行预判决,降低了RA码译码复杂度、提高了译码效率。在Middleton A类电力线信道模型下仿真结果表明：改进后的译码方法在低信噪比区域与BP算法性能相近,而在较高信噪比区域改进后的算法与BP译码算法相比所需信噪比少约0.8 dB,并且显著减少了译码过程中的迭代次数。     

工件坐标系编程的译码程序设计

数控系统对零件加工程序段中的坐标值译码最为复杂,采用C语言开发了数控系统中的译码程序,实现了工件坐标系下的编程译码,为今后实现更多编程方法提供了方便。     

基于最小和的高效LDPC译码算法

针对低密度奇偶校验（LDPC）译码算法性能低的问题,提出一种基于最小和的高效译码算法。该算法从概率的角度分析消息的传递过程中校验节点的更新过程,得到近似的最小和算法等式,并采用动态归一化因子提高译码性能。仿真实验表明,与BP译码算法相比,该译码算法在损失极少译码性能的情况下,不仅减少迭代过程中的计算量,而且提高了译码效率。     

一种基于RBF神经网络的线性分组码的通用译码网络

文中讨论了关于神经网络在差错控制译码中的应用，构造了一种基于RBF人工神经网络的线性分组码的通用译码网络，该网络通过有监督的学习后，可对任意长度、任意类型的线性分组码进行译码，并能对纠错范围内的误码进行自动纠错。     

基于改进型UMP BP-Based算法的LDPC译码研究

为了弥补UMP BP-Based译码算法相对于LLR BP译码算法的性能缺陷,提出一种改进型UMP BP-Based译码算法.该算法中的参数是在最小均方误差准则下确定的,对所有的LDPC码的译码具有通用性.仿真结果表明,在相同误码率的情况下,改进型UMP BP-Based译码算法比UMP BP-Based译码算法、Normalized BP-Based译码算法以及Offset BP-Based译码算法具有更好的LDPC译码性能.     

低复杂度Log-MAP译码算法的研究

提出用插值函数来计算Log-MAP算法中的校正函数,并在AWGN信道上采用分段差值方法实现了Turbo译码。该算法解决了校正函数计算复杂度较大的问题,消除了译码计算中的指数和对数运算。仿真结果表明：用2段二次样条函数实现的Turbo译码器,其译码性能与Log-MAP算法等价,而计算的复杂度明显降低,运算时间大幅度减少。     

二维条码中RS纠错译码算法的优化实现

利用Berlekamp Massey迭代算法、钱搜索算法以及Forney算法改进并实现了Data Matrix、QR Code和MaxiCode二维条码ISO标准中的Reed-Solomon纠错译码算法（简称RS算法）,降低了三种二维条码码制中RS纠错译码算法的计算复杂度。在此基础上,利用RS缩短系统码的特点对译码过程作进一步简化。实验结果表明,通过简化译码过程再次提高了RS纠错译码的速度。     

低信噪比通信系统中Turbo码应用仿真

由于Turbo码能得到较大的编码增益,因此许多低信噪比通信系统中都选择了Turbo作为信道编码。本文在简要介绍Turbo码的编译码原理的基础上,对Turbo码在通信系统中的应用进行了仿真,重点分析分析了译码方法、译码迭代次数、码率对Turbo性能的影响。     

统计译码的算法分析

统计译码是线性分组码中一种新的通用译码算法。该算法实现的关键在于如何从码字的对偶空间中合理选择一个矢量集合Hw,利用它对接收码字的校验作用实现有效译码。论文重点研究了Hw的构造问题,通过利用掩码矢量对Hw进行分集,得到了正、误两种情况下码元统计分布值的计算公式,揭示了统计译码算法内在的分布特性,改进了原有的译码算法。     

一种快速相关攻击算法

提出一种针对序列密码的改进的快速相关攻击算法。将序列密码的攻击问题转化为线性分组码的译码问题,采用最大似然译码方法进行译码。利用Walsh变换进一步优化算法的计算复杂度。对算法中的穷搜索比特数和校验方程重量2个关键参数的选取进行探讨,从理论上推导出校验方程重量与算法攻击成功概率之间的解析关系,为选取参数提供了依据。仿真结果表明,该算法性能优于之前的快速相关攻击算法。     

A Posteriory Probability Decoding of Nonsystematically Encoded Block Codes

We consider the problem of symbol-by-symbol a posteriori probability (APP) decoding for information symbols of nonsystematically encoded block codes. This problem arises at soft concatenated decoding of generalized concatenated block codes. The well-known BCJR algorithm for efficient APP decoding is not able to solve the problem if it runs on the minimal code trellis of a block code. We introduce an extended trellis representation for block codes, which includes encoding information and thus makes it possible to apply the BCJR algorithm as well as trellis-based decoding in the dual code space. Complexity properties of the extended trellis are investigated.     

面向数据可靠传输的高译码率带反馈的LT码

基于有码率和无码率的纠删码技术常用于解决网络丢包问题,但是存在译码率不高等缺点.面向数据可靠传输的高译码带反馈的LT码通过利用多个编码之间相互异或操作制造新的译码条件,可以大大提高译码率.相应的反馈机制能够以较小的传输反馈代价,实现可靠传输.实验结果表明,与现有译码方案相比,该方案的译码率可以提高35％.     

List decoding of Reed–Solomon codes from a Gröbner basis perspective

The interpolation step of Guruswami and Sudan’s list decoding of Reed–Solomon codes poses the problem of finding the minimal polynomial of an ideal with respect to a certain monomial order. An efficient algorithm that solves the problem is presented based on the theory of Gröbner bases of modules. In a special case, this algorithm reduces to a simple Berlekamp–Massey-like decoding algorithm.     

A coding theorem for multiple access channels using a maximum likelihood list decoding scheme

Bounds on the probability of error for list decoding, in which the receiver lists L messages rather than one after receiving a message, have been obtained by Elias, Ebert, and Shannon, Gallager and Berlekemp. In the present paper the problem of list decoding has been considered for a multiple access channel. The paper contains an upper bound on the probability of error for list decoding in this case.     

喷泉码中LT码的二次译码算法

LT码是喷泉码的一种,采用LT码的BP译码算法时,当处理完度数为1的数据后,译码将无法继续,造成停止集为空集,影响译码效率。为此,提出一种新的二次译码算法,在译码停止后,针对剩下的编码分组仍然具有可译性的特点,进行进一步译码。仿真结果表明,该算法在译码开销为0.2~0.5的情况下,译码效率普遍提高20%左右。     

基于BP神经网络的SCL译码研究

现存极化码译码算法仍然遭受非常高的复杂度.针对此问题,提出一种基于BP神经网络的SCL译码算法,该算法通过离线收集数据来搭建并训练一个合适的BP神经网络;借助已完成训练的BP神经网络,通过在线操作来寻找列表大小L的最优初始值;在此基础上,通过设计一种改进的SCL译码算法来降低复杂度.实验结果表明,与现存算法相比,新算法在低信噪比下能够显著降低平均译码复杂度.     

Bounded distance decoding of linear error-correcting codes with Gröbner bases

The problem of bounded distance decoding of arbitrary linear codes using Gröbner bases is addressed. A new method is proposed, which is based on reducing an initial decoding problem to solving a certain system of polynomial equations over a finite field. The peculiarity of this system is that, when we want to decode up to half the minimum distance, it has a unique solution even over the algebraic closure of the considered finite field, although field equations are not added. The equations in the system have degree at most 2. As our experiments suggest, our method is much faster than the one of Fitzgerald–Lax. It is also shown via experiments that the proposed approach in some range of parameters is superior to the generic syndrome decoding.     

Joint source channel VL coding/decoding for deep space communication networks based on a space trellis

This paper presents joint source channel variable length (VL) coding/decoding based on a space trellis.Through constructing a joint decoding plane trellis,better decoding performance can be achieved than by using the bit-level decoding algorithm.However,the plane trellis is complicated,which results in high decoding complexity for decoding VL turbo codes.To solve this problem,we construct a space trellis and design a low-complexity joint decoding algorithm with a variable length symbol-a posteriori probabil...     

Arc minimization in finite-state decoding graphs with cross-word acoustic context

Recent approaches to large vocabulary decoding with weighted finite-state transducers have focused on the use of determinization and minimization algorithms to produce compact decoding graphs. This paper addresses the problem of compiling decoding graphs with long span cross-word context dependency between acoustic models. To this end, we extend the finite-state approach by developing complementary arc factorization techniques that operate on non-deterministic graphs. The use of these techniques allows us to statically compile decoding graphs in which the acoustic models utilize a full word of cross-word context. This is in significant contrast to typical systems which use only a single phone. We show that the particular arc-minimization problem that arises is in fact an NP-complete combinatorial optimization problem. Heuristics for this problem are then presented, and are used in experiments on a Switchboard task, illustrating the moderate sizes and runtimes of the graphs we build.     

无线多跳网络下解码率可控的匿名网络编码

无线网络易于受到外界攻击,现有的匿名通信方案均无法满足资源受限的无线网络,网络编码的自然匿名特性能够较好地解决这一问题,但是其解码率很难控制。LT码的编解码特性可以有效控制可解码率,但是它对于多级传输过程无法适应。结合LT码和网络编码的思想,采用LT码的编解码方式,通过控制各节点编码包的度分布和对系数矩阵的重新构造完成再编码,完成多级匿名通信,使得信宿在解码时解码率接近1－δ。