多进制（Q-ary）LDPC码的编译码原理

多进制(Q-ary)LDPC码是将二进制LDPC码一般化到有限域GF(q),其校验矩阵元素不再是(0,1),而是集合(0,1,…,q-1),其译码仍然采用高效的信度传递迭代译码算法.本文主要阐述了多进制LDPC码的编译码原理,并介绍了一种可简化译码的傅立叶变换译码算法.通过将多进制LDPC码的性能与二进制LDPC码和RS码的性能进行比较,可以看出多进制LDPC码在磁存储系统、下一代ADSL系统以及深空通信方面将是取代RS码的强有力的候选,有极其重要的应用价值.     

多进制LDPC译码算法的研究

多进制LDPC码是将二进制LDPC码推广到有限域GF（q）,其校验矩阵的元素不再是（0,1）,而是集合（0,1,…,q-1）,译码仍然采用高效的基于置信度传播的迭代译码算法。这里主要推导了多进制译码算法的迭代公式,分析证明了基于快速傅里叶变换（FFT）理论的改进算法,最后通过仿真手段验证和分析了基于FFT的多进制译码算法的优越性能。     

影响多进制LDPC码译码性能因素研究

多进制LDPC码是将二进制LDPC码推广到有限域GF(q),其校验矩阵的元素不再是0和1,而是集合(0,1,2,…,q-1),译码仍然采用高效的基于置信度传播的迭代译码算法。文中主要阐述了准循环多进制LDPC码(QC-LDPC)校验矩阵的构造以及最小和译码算法的原理,然后在高斯白噪声信道(AWGN)中,用Matlab了仿真不同条件下LDPC码的译码性能,比较分析了影响多进制LDPC码译码性能的因素。     

一种多进制扩频通信基带接收的实现方法

为了在不增加带宽和不减小灵敏度的情况下增加扩频通信的数据传输速率,采用了多进制扩频通信的方法,该方法利用不同的扩频码来代表并传输信息,而不是用一种扩频码对信息源进行频谱扩展,不同的扩频码之间互相关性小且自相关性强,针对多进制扩频通信的设计思想,介绍了FPGA实现方法,详细描述了多进制扩频通信中数字下变频、伪码捕获和跟踪、载波捕获和跟踪的理论推导和技术实现途径。利用多进制扩频通信可以提高数据传输速率,在工程应用中,多进制扩频通信是一个可靠且有效的数据传输方法。     

基于FPGA的多进制扩频系统的设计与实现

传统扩频的扩频增益和抗干扰性是以增加频谱为代价的,而无人机对链路既有带宽又有抗干扰性的要求。针对这一矛盾,介绍一种多进制正交扩频通信的数字化设计方案,阐述了多进制扩频通信的扩频和解扩原理,重点讲解多进制扩频通信解扩关键部分的数字化实现,包括扩频序列的选取、解扩的采样量化、同步捕获电路以及数字匹配滤波器的数字化实现。基于所述方案的FPGA实现已经在实际应用中得到了验证。     

PID码在卫视接收中的应用

现在的数字卫星接收机(DVB)都具有PID码添加、修改功能,PID码分为图文PID、视频PID、音频PID和PcrPID(时钟同步码),PID码有10进制(PID10)和16进制(PID16,由数字0～9和A,B,C,D,E,F 6个字母组成)两种,如笔者用海克威2000 S数字接收机在收视105.5°E亚卫3 S星上C波段的美亚卫视(MATV)时,按一下遥控器上的信号强度指示键,屏幕上就会出现一些相关的信息:节目名称MATV,本振5 150 MHz,下行频率4 105.9 MHz,符码率11.230,极化方式水平(H),图文PID 0000,视频PID 1310,音频PID 1320,PcrPID 1310,此机PID码为10进制.     

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。      

数字指纹的技术分析与模型改进

数字指纹作为数字作品版权保护的一种新型技术,越来越受到人们的重视。文章首先介绍了数字指纹的功能与特征,然后分析了指纹的多种编码方案以及指纹协议的演进过程,最后提出了一种数字指纹的系统模型,该模型可用于一些数字作品的版权保护。     

多进制正交码解扩的FPGA实现

本文提出了一种高速分组无线网中多进制正交码解扩方案,采用串行FHT、并行FHT和并行积分法三种方法,在FPGA中实现了其核心——最佳非相干16进制解扩单元。详细分析结果发现,并行积分法可获得计算速度和资源消耗量之间很好的平衡,且具有控制简单、方案灵活的特点。     

基于欧式距离的多频多进制数字已调信号的优化设计

本文讨论了多频多进制数字已调信号的优化设计问题。首先,将多频多进制数字已调信号抽象为n维信号空间中的多进制矢量信号(或称信号点);其次,基于不同信号点间的最小欧式距离最大化的设计原则,构造了最佳多进制矢量信号,给出了最佳信号的闭合表达式,从而完成了对多频多进制信号的优化设计工作;最后,给出了2路2正交频率16进制和2路2正交频率64进制两种最佳信号的例子。     

VI-2类5维q元线性码的汉明重量谱的确定

上 线性码c的汉明重量谱为序列 ,其中,dr是c的r维子码的最小支撑重量。第VI类5维q元线性码的汉明重量谱,按照新的必要条件可以分成6个子类。运用有限射影几何方法研究VI-2类的5维q元线性码的汉明重量谱,确定VI-2类5维q元线性码的几乎所有汉明重量谱。     

LT码和q-LDPC码级联方案在深空通信中的应用

该文针对深空通信对长纠删码的需求,提出了LT (Luby Transform)码和q-LDPC码的级联方案。在综合考虑性能和复杂度的情况下,选取8-LDPC码和8PSK的级联作为等效的删除信道,长度选择灵活、编译码简单的LT码实现纠删功能。文中设计了两种短8-LDPC码,并对整个级联系统的纠错性能进行了仿真。仿真结果表明8-LDPC码的性能优于信源信息速率和码率相同的二进制LDPC码,级联系统在等效包删除概率不超过0.1时,系统误比特率以概率1趋于0。     

Constructions for q-Ary Constant-Weight Codes

This paper introduces a new combinatorial construction for q-ary constant-weight codes which yields several families of optimal codes and asymptotically optimal codes. The construction reveals intimate connection between q-ary constant-weight codes and sets of pairwise disjoint combinatorial designs of various types     

Forensic analysis of nonlinear collusion attacks for multimedia fingerprinting.

Digital fingerprinting is a technology for tracing the distribution of multimedia content and protecting them from unauthorized redistribution. Unique identification information is embedded into each distributed copy of multimedia signal and serves as a digital fingerprint. Collusion attack is a cost-effective attack against digital fingerprinting, where colluders combine several copies with the same content but different fingerprints to remove or attenuate the original fingerprints. In this paper, we investigate the average collusion attack and several basic nonlinear collusions on independent Gaussian fingerprints, and study their effectiveness and the impact on the perceptual quality. With unbounded Gaussian fingerprints, perceivable distortion may exist in the fingerprinted copies as well as the copies after the collusion attacks. In order to remove this perceptual distortion, we introduce bounded Gaussian-like fingerprints and study their performance under collusion attacks. We also study several commonly used detection statistics and analyze their performance under collusion attacks. We further propose a preprocessing technique of the extracted fingerprints specifically for collusion scenarios to improve the detection performance.     

k-error linear complexity of q-ary sequence of period p2

Based on element statistics in a matrix,a new efficient computing method for computing the k-error linear complexity of q-ary sequence of period p²was proposed,where p,q were odd primes and q modulo p²was primitive.A general result and a concrete proof were showed.To verify the correctness of the result,two kinds of q-ary sequence of period p²were illustrated.Because the new method does not need iterative calculation and when it is implemented by program and compared with existing algorithms,the results show that the proposed new algorithm is significantly more efficient in calculating k-error linear complexity of q-ary sequence of period p².     

数字喷泉码及其应用的研究进展与展望

 基于TCP协议的大部分网络通信都将接收到的数据包当作一个有序序列进行处理.TCP协议的这种有序序列模式限制了其在大量数据传输或将数据分布到大量用户的应用.基于数字喷泉码的数据传输模式不需要有序的数据序列,从而简化了网络中数据的传输方式,使得数字喷泉码成为一类适用于可靠通信的有效编码技术,而具有广阔的应用前景.本文综述了几类典型数字喷泉码的原理及其优缺点;探讨了这几类数字喷泉码的具体应用;指出了数字喷泉码研究中需要解决的一些关键问题.最后,对数字喷泉码的发展前景及研究方向进行展望.     

A Varshamov-Gilbert bound for a class of formally self-dual codesand related quantum codes

It is proved that a class of q-ary (2n,n) formally self-dual codes obtained from symmetric matrices over GF (q), contains codes that meet the Varshamov-Gilbert bound. The codes are self-dual with respect to the symplectic inner product and yield quantum codes encoding one state with n q-ary qubits and having minimum distance proportional to n     

Common coordinates in consecutive addresses

We consider lists of distinct q-ary addresses of length n. We wish that any b consecutive addresses in such a list agree in many positions. We give upper bounds on what can be achieved. Moreover, for each q and n, we give explicit constructions of address lists, among which is the conventional q-ary reflected Gray code, that attain these bounds for all b simultaneously. This work has applications in address retrieval on optical disc.     

Combine LDPC Codes Over GF(q) With q-ary Modulations for Bandwidth Efficient Transmission

Low-density parity-check (LDPC) codes are playing more and more important role in digital broadcasting standards due to their excellent error correction performance. In this paper, we study the combination of LDPC codes over GF(q) with q-ary modulations for bandwidth efficient transmission over AWGN channel and consider the design of the codes. Specifically, we develop the concept of quasi-regular codes, and propose an improved Monte Carlo method to optimize the quasi-regular codes. To justify the performance of our proposed scheme, simulation results are presented and analysed.     

Collusion-resistant fingerprinting for multimedia

Digital fingerprinting is a technology for enforcing digital rights policies whereby unique labels, known as digital fingerprints, are inserted into content prior to distribution. For multimedia content, fingerprints can be embedded using conventional watermarking techniques that are typically concerned with robustness against a variety of attacks mounted by an individual. These attacks, known as multiuser collusion attacks, provide a cost-effective method for attenuating each of the colluder's fingerprints and poses a real threat to protecting media data and enforcing usage policies. In this article, we review some major design methodologies for collusion-resistant fingerprinting of multimedia and highlight common and unique issues of different fingerprinting techniques. It also provides detailed discussions on the two major classes of fingerprinting strategies, namely, orthogonal fingerprinting and correlated fingerprinting.