视频字符叠加器

文章介绍了实现在电视信号上叠加字符的方法，并具体给出了一个实际用于水井电视检修的视频字符叠加器的软硬件。     

A note on generalized Hamming weights of BCH(2)

Determines results for the first six generalized Hamming weights of double-error-correcting primitive binary BCH codes     

Generalized Hamming weights of BCH(3) revisited

Determines the first five generalized Hamming weights of 3-error-correcting primitive binary BCH-codes     

On the generalized Hamming weights of several classes of cycliccods

The generalized Hamming weights of a linear code are fundamental code parameters related to the minimal overlap structures of the subcodes. They were introduced by V.K. Wei (1991) and shown to characterize the performance of the linear code in certain cryptographical applications. Results are presented on the generalized Hamming weights of several classes of binary cyclic codes, including primitive double-error-correcting and triple-error-correcting BCH codes, certain reversible cyclic codes, and some extended binary Goppa codes. In particular, the second generalized Hamming weight of primitive double-error-correcting BCH codes is determined and upper and lower bounds are obtained for the generalized Hamming weights for the codes studied. These bounds are compared to results from other methods     

Improving the Hamming binary associative memory

The Hamming network is a binary associative memory which exhibits the maximum theoretically obtainable performance in terms of capacity and associativity. The structure is not ideal and two modifications which reduce the number of connections in the correlation matrix and in the selection layers are suggested. These modifications offer a significant reduction in the number of calculations required.<>     

Inversionless decoding of binary BCH codes

The iterative algorithm for decoding binary BCH codes presented by Berlekamp and, in an alternative form, by Massey is modified to eliminate inversion. Because inversion in a finite field is time consuming and requires relatively complex circuitry, this new algorithm should he useful in practical applications of multiple-error-correcting binary BCH codes.     

The normalized second moment of the binary lattice determined by aconvolutional code

Calculates the per-dimension mean squared error μ(S) of the two-state convolutional code C with generator matrix [1,1+D], for the symmetric binary source S=(0,1), and for the uniform source S={0,1}. When S=(0,1), the quantity μ(S) is the second moment of the coset weight distribution, which gives the expected Hamming distance of a random binary sequence from the code. When S={0,1}, the quantity μ(S) is the second moment of the Voronoi region of the module 2 binary lattice determined by C. The key observation is that a convolutional code with 2^υ states gives 2^υ approximations to a given source sequence, and these approximations do not differ very much. It is possible to calculate the steady state distribution for the differences in these path metrics, and hence, the second moment. The authors only give details for the convolutional code [1,1+D], but the method applies to arbitrary codes. They also define the covering radius of a convolutional code, and calculate this quantity for the code [1,1+D]     

Parallel decoding of binary BCH codes

A parallel decoding procedure for the BCH codes is introduced, which is particularly useful for decoding BCH codes with small error-correcting capability. The high regularity inherent in the scheme enable it to be easily implemented with VLSI circuits.<>     

Steganalysis of BCH code based stego schemes

The class of stego systems based on error correcting codes is one of the alternatives to conventional steganographic systems. In the context of code based steganography, the BCH code based stego system offers a very smart solution based on the hardness of syndrome decoding. It has been shown that syndrome decoding problem is able to resist the existing steganalysis attacks. In this paper, we introduce an attack against these systems using a new syndrome decoding method. This scheme also generates a direct estimate of the secret message bit locations by exploiting the embedding patterns. This new attack notably points out that BCH code based stego system with its original parameters do not provide sufficient security.     

On the optimality of the binary reflected Gray code

This paper concerns the problem of selecting a binary labeling for the signal constellation in M-PSK, M-PAM, and M-QAM communication systems. Gray labelings are discussed and the original work by Frank Gray is analyzed. As is noted, the number of distinct Gray labelings that result in different bit-error probability grows rapidly with increasing constellation size. By introducing a recursive Gray labeling construction method called expansion, the paper answers the natural question of what labeling, among all possible constellation labelings, will give the lowest possible average probability of bit errors for the considered constellations. Under certain assumptions on the channel, the answer is that the labeling proposed by Gray, the binary reflected Gray code, is the optimal labeling for all three constellations, which has, surprisingly, never been proved before.     

汉明码的Matlab设计

通信技术与人们的生活越来越紧密,对通信技术的仿真和研究使复杂的通信过程变得简单直观化。文中对编码通信中汉明码的编译码原理进行了分析,并用Matlab语言仿真,不但简化了学生的学习过程,提高了教学效果,而且激发了其学习兴趣。     

Complete decoding of triple-error-correcting binary BCH codes

An extensive study of binary triple-error-correcting codes of primitive lengthn = 2^{m} - 1is reported that results in a complete decoding algorithm whenever the maximum coset weightW_{max}is five. In this regard it is shown thatW_{max} = 5when four dividesm, and strong support is provided for the validity of the conjecture thatW_{max} = 5for allm. The coset weight distribution is determined exactly in some cases and bounded in others.     

汉明编译码仿真系统的实现

随着通信事业的快速发展,差错控制编码技术在确保通信质量方面具有举足轻重的地位。（7,4）汉明码是差错控制编码中最基本、最简单的一种。这里着眼于利用功能强大、效果强劲的Flash软件实现（7,4）汉明码的设计与系统仿真。重点介绍了系统的实现过程和功能演示,突出了（7,4）汉明码的纠、检错能力,在科学研究的示例说明、相关产品的辅助介绍以及多媒体教学等诸多方面都具有较高的实用价值。     

汉明码在数字音频水印嵌入中的应用

汉明码作为一种具有纠错功能的编码技术,在通信领域被广泛研究与应用。为降低水印提取的误码率,文中利用汉明码良好的纠错性能和均值量化的稳定性,提出一种基于汉明码的数字音频水印算法。首先将作为水印信号的二值信号进行汉明编码,并将编码后的汉明码矩阵利用Logistic映射加密,然后将原始音频数据小波变换,通过均值量化将加密后的汉明码嵌入到音频中。实验结果表明,该算法具有较好的透明性,对常规处理具有鲁棒性,有效降低了水印的误码率。     

On minimal decoding sets for the extended binary Golay code

Minimal decoding sets consisting of fourteen permutations have been found for the (24,12,8) extended binary Golay code. It is shown that by properly sequencing the permutations of one such set, the average number of permutations required to decode a random received word can be minimized     

超高速BCH码解码改进算法研究

为了满足高速光纤通信系统纠错编码(FEC)的要求,本文提出了一种简单的BCH码解码算法,省略了复杂的矩阵运算,除法运算,也避免了难以理解的迭代运算。其编译码速度快、效率高,并针对硬件特点做了一些优化,特别适合于硬件实现。同时,本文提出了并行算法,大大加快了编译码速度。利用可编程器件FPGA实现,仿真结果完全正确,且非常有效。该算法不仅可用于高速光纤通信系统中,也可以用于其他高速通信系统。