RS(204,188)码连续解码的设计

先分析了RS码的编解码原理,RS（204,188）码可以纠错8位的随机误码,适用于DVB标准数字电视的信道纠错。通过Matlab软件获取了RS（204,188）的编码。解码主要包括求伴随子、求错误位置多项式和关键等式、错误位置、错误值,最后完成纠错。其中最关键的就是求错误位置多项式和关键等式,常有BM算法及欧几里德算法。设计时采用Verilog语言设计、ISE9.2集成工具、FIFO实现解码的连续。重点介绍了欧几里德算法求错误位置多项式和关键等式、各模块的硬件实现结构以及具体的实现,验证时随机设取了8个误码,经过解码后恢复了原码。     

基于VHDL语言的CRC信道编解码电路设计与实现

CRC码由于其具有良好的检纠错能力在现代通信中得到了非常广泛的应用.文中讨论了CRC码的原理,详细分析了编码,解码及纠正一个码元错误的设计思路,并用VHDL实现了CRC(15,6)码的编解码电路.     

基于循环长除法的BCH(31,16)译码算法

BCH码的快速译码算法一直是纠错编码领域研究的一个热点问题,针对特殊的BCH(31,16)快速译码问题,提出了一种新颖的基于循环长除法和置换群理论相结合的译码算法。该算法首先利用有限域F 2(x)中的循环长除法,用接收到的含有错误位的接收码循环长除生成多项式得到余式,如果余式项数小于等于BCH(31,16)纠错范围,此余式即为错误多项式,和接收码模2相加即得原码。如果所得余式不满足上述要求,利用置换群理论对接收码进行位置置换,再循环长除生成多项式得余式,若此余式项数小于等于BCH(31,16)纠错范围,此余式即为错误多项式,逆置换此余式,和接收码模2相加即得原码。本算法和常规的BCH译码相比较,不需要存储错误图样,也不需要解BM方程,可直接可编程实现。理论分析和程序仿真均证明此算法有效可行,软硬件实现简单,具有重要的实际应用价值。     

RS级联编码在超短波通信与卫星通信信道的仿真分析

超短波波段数据通信与卫星通信已被广泛应用。在这些信道中都存在较强的多径衰落,并且为克服两个波段中的多种干扰,纠正随机错误和突发错误,RS编码被普遍选为信道编码方案。RS码是线性分组码中纠突发错误能力最强,效率最高的编码,Turbo码是可以接近香农限的编码方案。文章提出RS编码与Turbo码的级联码编码方案和解码算法,适当选择参数,并通过仿真验证了方案的正确性与可行性。     

基于FPGA的空间存储器的纠错系统

国际空间站上AMS存储系统受到高能粒子的轰击,可能对随机存储器(RAM)电路产生影响,改变半导体存储器件的逻辑状态,导致存储单元在逻辑‘0’与‘1’之间发生翻转,产生一些关键存储数据出错和控制程序跑飞等问题。本文提出了基于纠错编码基本原理的BCH(31,16)算法,该算法能够有效解决三位随机错误的纠正问题,其译码算法采用错误图样查找法。利用Verilog DHL编程语言来设计BCH(31,16)码的编码与解码,并下载到FPGA开发板上进行电路验证。     

K量级群变换BCH码纠错方法研究与实现

介绍了一种新的方法——群变换BCH码编解码方法,这种方法简化了BCH码的编解码过程。然后利用该方法对长度在1K以上的信息位进行编码,得到K量级的数据,并将该K量级的数据作为一个数据包进行整体的解码和纠错。文中用的K量级的BCH码能纠正2位错误,传送率（简称码率）高达1003/1023≈98%,该通信系统的误码率能改善20 dB以上。同时,还用Cyclone-III大规模集成电路完成了硬件实现。     

基于比特概率优化算法的分布式视频编码

分布式视频编码器中Turbo码纠错所需要的校验位数量直接决定整个编码器的率失真(RD,Rate-Distortion)性能.分析了传统算法的次优化问题,提出一种新的基于比特概率优化的信道似然值计算算法,该算法首先将原始像素进行比特面分解,然后分别对每个比特面进行独立Turbo码编码及联合解码.解码端在已知已解码比特面的条件下,计算当前解码比特面更准确的信道似然值作为Turbo码的解码输入,减少解码所需要传输的校验位数量,提高编码器RD性能.实验结果表明所提算法能明显提升编码系统的RD性能.     

NAND闪存错误缓解技术综述

NAND闪存以其高存储密度、高速、低功耗等优点被广泛应用于数据存储。三维堆叠闪存技术的出现和多值存储技术的发展进一步提高了密度,降低了存储成本,同时也带来了更加严重的可靠性问题。闪存主控厂商一直采用更强大的纠错码(ECC),如BCH和LDPC码来对闪存中的数据错误进行纠正。但当NAND闪存中的错误数超出ECC纠错能力时,错误将无法被纠正,因此研究人员提出了多种基于NAND闪存的错误缓解技术作为ECC的补充方案。本文介绍了NAND闪存的工作原理和错误模式,对最新的错误缓解技术进行综述,为设计更加可靠的存储解决方案提供了有益参考。     

空间存储器纠错系统的软件实现

本文分析了国际空间站AMS存储系统中一些恶劣的空间环境对随机存储器RAM电路的影响,它可能改变半导体记忆器件的逻辑状态,导致存储单元在逻辑"0"与"1"之间发生翻转等问题.本文采用了基于纠错编码基本原理的BCH(15,7)算法,该算法能够有效解决两位随机错误的纠正问题.本文采用错误图样查找的译码方法,用Verilog DHL来设计BCH(15,7)码的编码与解码,并下载到FPGA芯片上,通过仿真和实践都证明了这种方案的正确性和可行性.     

MPEG-2中的错误隐藏技术

由于MPEG-2在编码端引入预测编码,使得MPEG-2视频码流对错误十分敏感。信道传输引起的错误会在时间上扩散,造成图像质量急剧下降。以MPEG-2编码技术为基础,结合实际视频传输的特点,提出了一种基于相邻帧的运动补偿算法和空域多关联线性内插算法,可在解码端实现错误隐藏。仿真实验表明,提出的错误隐藏算法可降低由于误码造成的图像失真和错误扩散,有效地改善了视频图像质量。     

A class of binary burst error-correcting quasi-cyclic codes

A class of binary quasi-cyclic burst error-correcting codes based upon product codes is studied. An expression for the maximum burst error-correcting capability for each code in the class is given. In certain cases, the codes exist in the class which have the same block length and number of check bits as the Gilbert codes, but correct longer bursts of errors than Gilbert codes. By shortening the codes, it is possible to design codes which achieve the Reiger bound     

Improved asymptotic bounds for error-correcting codes

The author has previously developed a new upper bound on nonsystematic binary error-correcting codes, using a sphere-packing approach and combinatorial analysis. A significant refinement is now added; together with a detailed study of the asymptotic behavior of the upper bound, this enables one to show that any large code must {em correct} almost all sequences with a larger number of errors than the code was designed for. This excess is expressed numerically as a fraction of the designed error-correcting capability of the code. The fraction is a function of the ratio of the sequence length and the designed error-correcting capability. A possible application might be in the use of a larger code giving almost certain error correction rather than a smaller one with certain correction capability.     

An on-chip ECC circuit for correcting soft errors in DRAMs withtrench capacitors

A modified error-correcting code that can correct up to two soft errors on each row (word line) in a dynamic random-access memory (DRAM) chip is proposed. Double-bit soft errors frequently occur in DRAM cells with trench capacitors, when charged alpha particles impinge on the intervening space between two vertical capacitors causing plasma shorts between them. The conventional on-chip error-correcting codes (ECCs) cannot correct such double-bit word-line soft errors, which significantly increase the uncorrectable error rate (UER). An ECC circuit that uses an augmented rectangular product code to detect and correct double-bit soft errors is presented. The proposed circuit automatically corrects the addressed bit if it is faulty, and then quickly locates the other faulty bit. A comprehensive study is made to estimate improvements in soft error rate (SER) and mean time to failure (MTTF). The ability of the circuit to correct soft errors in the presence of multiple-bit errors has also been analyzed by combinatorial enumeration     

Correction of synchronization errors with burst-error-correcting cyclic codes

It is shown that every linear cyclicb-burst-error-correcting code over any finite field can be modified to correct up to(b-2)symbols of synchronization slippage without additional redundancy, while maintaining its additive error-correcting capability in the absence of synchronization errors. For codes that are interleaved to a degreem, the synchronization error-correcting capability ism (b-1) - 1symbols, whereb geq 3is the length of the burst each subcode corrects. This technique gives an optimum burst-error-correcting code a synchronization error-corecfing capability that is only one symbol short of the known upper bound and is hence asymptotically optimal. Moreover, the implementation is very simple.     

QC-LDPC码在部分响应信道中的性能研究

磁盘存储系统的高传输密度导致突发错误增多,QC-LDPC码可以作为磁存储系统的纠错编码。研究了构造QC-LDPC码的方法。搭建了磁记录系统模型,使用EPR4和PR4模拟磁记录信道,探讨了不同码率的QC-LDPC码在两种信道下的纠错性能。仿真结果表明QC-LDPC码在两种信道下具有良好的纠错能力。     

Unequal error protection for convolutional codes

In this correspondence, unequal error-correcting capabilities of convolutional codes are studied. For errors in the information symbols and code symbols, the free input- and output-distances, respectively, serve as "unequal" counterparts to the free distance. When communication takes place close to or above the channel capacity the error bursts tend to be long and the free distance is not any longer useful as the measure of the error correcting capability. Thus, the active burst distance for a given output and the active burst distance for a given input are introduced as "unequal" counterparts to the active burst distance and improved estimates of the unequal error-correcting capabilities of convolutional codes are obtained and illustrated by examples. Finally, it is shown how to obtain unequal error protection for both information and code symbols using woven convolutional codes.     

An embedded transmission scheme using PPM signaling with symmetric error-correcting codes for optical CDMA

An embedded transmission (ET) scheme is proposed to easily apply error-correcting codes into optical code-division multiple-access (CDMA) systems for immunity from multiple-access interference (MAI). The ET scheme offers high transmission capability over the traditional scheme using pulse position modulation (PPM) signaling, because a 2/sup J/-ary symbol of each user is embedded in the signature sequence with 2/sup J/ weighted positions. Furthermore, the ET scheme with 2/sup J/-ary PPM signaling makes the optical CDMA system J parallel transmission systems, because J bits consisting of 2/sup J/-ary symbol are separately decided. Since such a separate decision is a comparison decision, the effect of MAI added in the optical channel is converted to symmetric errors in the individual parallel transmission systems. Using the symmetric error-correcting (SEC) code immunizes the individual parallel transmission systems against MAI more easily than the embedded-modulation scheme described in because the ET scheme avoids using the asymmetric error correcting code, which is difficult to implement. We analyze the bit error rate under Poisson photon counting channel and show that the ET scheme has an advantage of good energy efficiency over the traditional scheme in applying SEC codes.     

Coherent网络中的纠错码

网络编码对网络中的传输错误或恶意攻击十分敏感,如果网络拓扑和网络码对于网络的收点和发点都是已知的,这种类型的网络称为Coherent网络。在Coherent网络中,网络汉明重量的概念拉近了网络纠错码和传统纠错码之间的距离,传统纠错码的一些理论和方法有望在将来应用于网络纠错码。类似于传统纠错码,极小距离反映了网络纠错码的纠错能力。利用陪集码理论去描述和研究网络纠错码是一个令人感兴趣的研究方向。     

针对前向纠错编码的脉冲干扰技术研究

数字通信系统通常采用前向纠错编码提高系统可靠性,传统干扰方法针对采用前向纠错编码通信系统的干扰效果较差,为了克服此缺点,提出了通过控制错误分布的脉冲干扰方法。分析了典型卷积码和RS码的纠错能力,根据2种纠错编码的特性分别探讨了干扰信号设计原则和方法。计算机仿真表明,针对不同的编码样式采用特定脉冲干扰参数,能够取得更好的干扰效果。     

An error-correcting code for data broadcasting and its error-correction capability

By using the vertical blanking period of television signals, it is possible to transmit coded data such as teletext, newspaper, telesoftware, music score, etc. However, the quality of ordinary TV channels is very poor for digital communications and a powerful error-correcting code is required to reliably transmit coded data. From the results of simulations using error pattern data collected in field tests and the comparison of various error-correcting codes under many conditions, it has been determined that the shortened (272, 190) majority-logic decodable difference-set cyclic code is a suitable code for NTSC TV signals. Moreover, the decoding algorithm for this code has been improved in order to increase the error-correction capability and a new LSI with this function has been developed. By using error-correcting codes proposed to date for teletext, it has been difficult to obtain a page error rate (PER) of 10⁻¹in many measurement points. However, PERs of less than 10⁻² can be obtained in this system, even when random noise, ghost interference, or waveform distortion are present and bit error rates (BERs) are 10⁻². This paper also gives PERs according to the error-data collected in field tests and shows that the error-correction capability increased equivalently up to 11 error-bits in a 272-bit by improving the decoding algorithm and the results of indoor and outdoor tests.