An efficient decoding technique for Huffman codes

We present a new data structure for Huffman coding in which in addition to sending symbols in order of their appearance in the Huffman tree one needs to send codes of all circular leaf nodes (nodes with two adjacent external nodes), the number of which is always bounded above by half the number of symbols. We decode the text by using the memory efficient data structure proposed by Chen et al. [Inform. Process. Lett. 69 (1999) 119-122].     

Shortest synchronizing strings for Huffman codes

Most complete binary prefix codes have a synchronizing string, that is a string that resynchronizes the decoder regardless of its previous state. This work presents an upper bound on the length of the shortest synchronizing string for such codes. Two classes of codes with a long shortest synchronizing string are presented. It is known that finding a synchronizing string for a code is equivalent to finding a synchronizing string of some finite automaton. The Černý conjecture for this class of automata is discussed.     

Design of efciently encodable nonbinary LDPC codes for adaptive coded modulation

This paper is concerned with constructions of nonbinary low-density parity-check(LDPC)codes for adaptive coded modulations(ACM).A new class of efciently encodable structured nonbinary LDPC codes are proposed.The defining parity-check matrices are composed of scalar circulant sub-matrices which greatly reduce the storage requirement when compared with random LDPC codes.With this special structure of paritycheck matrix,an efcient encoding algorithm is presented.Based on the proposed codes,a family of variablerate/variable-field nonbinary LDPC codes is designed for the ACM system.When combined with matched-size signal constellations,the family of constructed codes can achieve a wide range of spectral efciency.Furthermore,the resultant ACM system can be implemented via a set of encoder and decoder.Simulation results show that the proposed nonbinary LDPC codes for the ACM system perform well.     

Design of efficiently encodable nonbinary LDPC codes for adaptive coded modulation

This paper is concerned with constructions of nonbinary low-density parity-check （LDPC） codes for adaptive coded modulations （ACM）. A new class of efficiently encodable structured nonbinary LDPC codes are proposed. The defining parity-check matrices are composed of scalar circulant sub-matrices which greatly reduce the storage requirement when compared with random LDPC codes. With this special structure of parity- check matrix, an efficient encoding algorithm is presented. Based on the proposed codes, a family of variable- rate/variable-field nonbinary LDPC codes is designed for the ACM system. When combined with matched-size signal constellations, the family of constructed codes can achieve a wide range of spectral efficiency. Furthermore, the resultant ACM system can be implemented via a set of encoder and decoder. Simulation results show that the proposed nonbinary LDPC codes for the ACM system perform well.     

Complexity aspects of guessing prefix codes

Given a natural language cleartext and a ciphertext obtained by Huffman coding, the problem of guessing the code is shown to be NP-complete for various variants of the encoding process.     

DPCM与自适应Huffman结合的压缩算法

为了解决大容量雷达数据传输,满足雷达原始视频信号实时无损的要求,根据雷达原始视频信号的特点,给出了采用DPCM(DifferencePulseCodingModulation)与自适应Huffman编码相结合的压缩编码方式,分析了该算法的有效性和溢出问题,实验表明该方法相对于传统的自适应Huffman编码而言能改善实时性,提高压缩比。     

并行Huffman解码器算法分析与实现

介绍了一种新颖的并行Huffman解码器及算法的实现方法,这种解码器最大的优点是它能够在一个进钟节拍中同时处理多个数据,从而克服了串行处理技术中实时性差的缺点。这种并行Huffman译码技术在数字通信领域将会有很大的使用价值。     

赫夫曼树遍历算法的优化

对数据结构中赫夫曼树和赫夫曼遍历的算法问题进行探讨,针对传统使用的遍历算法存在循环次数较多、算法时间复杂度较大问题,通过修改参数和循环体结构对原有算法进行改进,从而减少循环次数,降低算法时间复杂度,同时也提出了动态编码算法等的优点和可行性。     

赫夫曼树遍历算法的优化

对数据结构中赫夫曼树和赫夫曼遍历的算法问题进行探讨,针对传统使用的遍历算法存在循环次数较多、算法时间复杂度较大问题,通过修改参数和循环体结构对原有算法进行改进,从而减少循环次数,降低算法时间复杂度,同时也提出了动态编码算法等的优点和可行性。     

不依赖树结构的规范哈夫曼码压缩算法

传统的哈夫曼编码需要构建哈夫曼树方可生成,同时要保留原始的哈夫曼树供译码时参照恢复原信息.由于哈夫曼编码码长不一,对照哈夫曼树译码的方法麻烦费时;而且每棵哈夫曼树都必须有以下结构:编码,信息,频度,双亲,左孩子,右孩子.而解码时只需用到编码、信息域就可以了,因此造成不必要的空间浪费.鉴于这种情况,本文提出了一种不依赖树结构进行高速编码/译码的规范哈夫曼码压缩算法,实验证明,该算法的整个压缩、解压缩过程比传统的哈夫曼压缩算法快得多,所需空间少得多,是一种行之有效的快速压缩算法.     

改进的四进制哈夫曼算法

提出了一种改进的四进制哈夫曼树的生成算法,通过分析算法的平均码长和编码效率,论证了算法相对于传统的四进制算法的优点。并用C语言分别实现两种算法,进行了压缩比和压缩时间的比较,证明了改进算法在压缩比和压缩速度上的提升。     

对哈夫曼树唯一性的探讨

在我们的日常教学中,我们经常会对哈夫曼树的建立给出不同答案,那么是否有唯一标准答案?通过相关程序流程及代码实验,分析了导致认为创建哈夫曼树不唯一的原因,说明了在一种既定的算法下,我们是可以达到哈夫曼树建立的唯一性的.     

构造赫夫曼树的高效算法

构造特定的赫夫曼树是编译码的前提,为此提出了一种新的赫夫曼树构造算法,以提高赫夫曼树的构造效率。     

Huffman algebras for independent random variables

Based on a rearrangement inequality by Hardy, Littlewood, and Polya, we define two-operator algebras for independent random variables. These algebras are called Huffman algebras since the Huffman algorithm on these algebras produces an optimal binary tree that minimizes the weighted lengths of leaves. Many examples of such algebras are given. For the case with random weights of the leaves, we prove the optimality of the tree constructed by the power-of-2 rule, i.e., the Huffman algorithm assuming identical weights, when the weights of the leaves are independent and identically distributed.     

哈夫曼算法的改进与应用

哈夫曼树是带权路径长度(WPL)最小的二叉树,通过对哈夫曼算法的研究,提出一种求取哈夫曼树带权路径长度的改进方法,简化运算,有效提高求取WPL的效率和正确性。同时利用哈夫曼算法进行数据压缩,获得明显的压缩效果。     

哈夫曼算法的改进与应用

哈夫曼树是带权路径长度（WPL）最小的二叉树，通过对哈夫曼算法的研究，提出一种求取哈夫曼树带权路径长度的改进方法，简化运算．有效提高求取WPL的效率和正确性。同时利用哈夫曼算法进行数据压缩，获得明显的压缩效果。     

New bounds on D-ary optimal codes

We propose a simple method that, given a symbol distribution, yields upper and lower bounds on the average code length of a D-ary optimal code over that distribution. Thanks to its simplicity, the method permits deriving analytical bounds for families of parametric distributions. We demonstrate this by obtaining new bounds, much better than the existing ones, for Zipf and exponential distributions when D>2.     

优化哈夫曼算法的数据压缩研究

在信息快速传输和存储的过程中，数据压缩有着很重要的作用。本文介绍了目前无损压缩技术发展现状及哈夫曼原理，并对哈夫曼算法进行优化实现整个过程，使文件压缩率更高。实验结果证明了这种方法的有效性。     

优化哈夫曼算法的数据压缩研究

在信息快速传输和存储的过程中,数据压缩有着很重要的作用。本文介绍了目前无损压缩技术发展现状及哈夫曼原理,并对哈夫曼算法进行优化实现整个过程,使文件压缩率更高。实验结果证明了这种方法的有效性。