关于Lempel-Ziv信源编码算法修正方法的研究

本文针对L-Z信源编码算法在对信息序列进行编码分段时,最后部分码段可能与前面的码段重复而不能编码,由此产生丢失数据的情况,提出了修正的方法,将L-Z编码编码时丢失数据的问题予以解决.     

预编码——差错控制编码的一种新方法

文章首先介绍了Ａ．Ｓ．Ｋｈａｙｒａｌｌａｈ提出的对差错控制码进行预编码的基本思想，然后指出了预编码理论与实践上的意义。     

数字电视信源编码的主要技术与标准

本文介绍了有关数字电视信源编码的一些主要技术和标准，包括数字演室标准ＩＴＵ－－６０１，压缩编码的基本原理和方法，图像压缩编码标准Ｈ２６１、ＪＰＥＧ和ＭＰＥＧ，以及作为数字电视信源编码标准输出的ＫＰＥＧ－－２码流的形成。     

保持编码效率的变长码分解方法

本文介绍了能用数学解杆式表示的变长码和它的三种编译码算法，提出了这种变长码的分解方法，分解后的多个变长码保持了原变长码的编码效率，但降低了编译码的复杂度。     

多进制霍夫曼编码方法及最优性证明

信源编码最常用的翟夫曼可变长编码是性能最优的唯一可译即时码。在讨论编码方法时常以二进制为例进行。多进制的霍夫曼编码如何进行,怎样证明得到的编码一定是平均码长最短的唯一可译即时码,是本文讨论和证明的主题。     

信源编码在密码学中的应用

信源编码（或数据压缩）可以有效地应用于密码学。本文描述五种信源编码方案。基中三种方案属于通用信源编码类型，可以用来产生强理想密码，实现“通用”多名码代替，测试随机比特发生器，以及强化序列密码的滚动密钥发生器等等。     

LDPC和SPIHT联合编码用于图像压缩与保护的方法

提出了结合SPIHT（set partitionine in hierarchical trees）算法和LDPC（Low-Density Parity-Check）码的信源与信道联合编码方案。这一方案充分考虑了SPIHT算法和LDPC码的特性，根据信源编码后数据在重建时的重要程度，进行不同等纠错保护的信道编码方案。通过实验仿真的结果表明，论的方法能够使图像在高码率下达到较好的抗噪性能。     

基于LDPC码的小波图像传输码率优化

LDPC码是一种具有低复杂度,强纠错能力的信道分组编码结构,SPIHT算法是嵌入式小波图像压缩编码中性能较好的一种。文中充分考虑SPIHT算法和LDPC码的特性,提出了根据信源编码后的数据在解码重建时的重要程度进行不等纠错保护的信源信道联合编码方案。实验表明,该方案有利于压缩图像在噪声信道上的可靠传输,提高系统整体纠错性能。     

矢量的线上投影表示法

本文提出一种矢量压缩编码新方法—线上投影法.它将输入矢量用它在某条空间直线上的投影近似表示,而用决定这条直线的两个参考点的序号和一个反映该投影点相对于两参考点位置的比例因子作为编码.由于一个大小为N的矢量量化码书中的码字可以确定N(N-1)/2条直线,因此这种方法可用较小的码书获得很高的编码精度.理论分析和实验结果表明:码书大小为N的线上投影法的编码精度与码书大小为N²的矢量量化法相当,并且明显优于用两个大小为N的码书构成的两级矢量量化法,而其码书生成和编码过程的计算复杂度均远远低于后者.它将是矢量信号高精度压缩编码的一种强有力的手段.     

数字通信中的信源编码技术

简述了数字通信各领域对于语音、图文、视频、音乐春它数据的实用信源编码技术，重点介绍了已经形成的国际标准和建议。     

Near-Shannon/Slepian-Wolf performance for unknown correlated sources over AWGN channels

We consider the problem of joint source-channel coding of two correlated binary information sequences. Instead of compressing the information using source coding, both sequences are independently channel encoded and transmitted over two independent additive white Gaussian noise channels. No information about the correlation between the sources is required in the encoding process. The correlation between both sequences is exploited at the receiver, allowing reliable communications at signal-to-noise ratios very close to the theoretical limits established by the combination of Shannon and Slepian-Wolf theorems. This occurs even when the correlation between sources is not known at the decoder, since it can be estimated jointly with the iterative decoding process.     

A Spectral Analysis of M-ary Direct Sequence Spread-Spectrum Multiple Access Communication Systems

This paper presents the power spectrum of the transmitted signal in a synchronous spread-spectrum communication system in which the users' information symbol sequences are encoded intoM-ary channel symbol sequences. Furthermore, when maximal-length shift register sequences are used as the spreading code sequences of the system, the average power spectrum over all possible sets of the allowable simultaneous users is presented. It is shown that distribution of the spectrum is influenced considerably by the spreading code and the channel symbol sequences.     

How to encode the modulo-two sum of binary sources (Corresp.)

How much separate information about two random binary sequences is needed in order to tell with small probability of error in which positions the two sequences differ? If the sequences are the outputs of two correlated memoryless binary sources, then in some cases the rate of this information may be substantially less than the joint entropy of the two sources. This result is implied by the solution of the source coding problem with two separately encoded side information sources for a special class of source distributions.     

一种数据包合并跨层优化编码方案

在传统分层系统中,信息数据包首先在数据链路层进行数据包级的检错码编码,然后一个数据包对应一个信息分组在物理层进行符号级的纠错码编码,最后送入信道中传输。为提高系统的传输效率,提出了一种基于数据包合并的物理层与数据链路层编码的跨层优化方案,即数据链路层的多个数据包合并对应物理层的一个信息分组,然后进行纠错编码后再传输。通过理论推导得出了使系统传输效率最大的最优合并数据包个数和数据包长度表达式。通过仿真验证了理论推导的正确性,并与传统方案进行了比较,结果表明,该方案能有效提高系统的传输效率。     

降低头肩视频序列编码码率的一种新方法

在头肩视频低码率编码的情况下,需要准确判定不编码宏块,从而节省码字。本文描述了一个基于运动矢量扫描的新算法,能够预测运动区域和静态背景区域,并在保证感兴趣区域质量的情况下,对静态区域的大部分宏块不编码。实验结果显示在低码率下,该算法能够大大节约编码的码字,而且在小运动序列时,可以显著减少编码的时间。     

Test Data Compression Using Multi-dimensional Pattern Run-length Codes

Test data compression is an efficient methodology in reducing large test data volume for system-on-a-chip designs. In this paper, a variable-to-variable length compression method based on encoding runs of compatible patterns is presented. Test data in the test set is divided into a number of sequences. Each sequence is constituted by a series of compatible patterns in which information such as pattern length and number of pattern runs is encoded. Theoretical analyses on the evolution of the proposed Multi-Dimensional Pattern Run-Length Compression (MD-PRC) are made respectively from one-Dimensional-PRC to three-Dimensional-PRC. To demonstrate the effectiveness of the proposed method, experiments are conducted on both larger ISCAS’89 benchmarks and the industrial circuits with large number of don’t cares. Results show this method can achieve significant compression in test data volume and have good adaptation to industrial-size circuits.     

Robust multiplexed codes for compression of heterogeneous data

Compression systems of real signals (images, video, audio) generate sources of information with different levels of priority which are then encoded with variable-length codes (VLCs). This paper addresses the issue of robust transmission of such VLC encoded heterogeneous sources over error-prone channels. VLCs are very sensitive to channel noise: when some bits are altered, synchronization losses can occur at the receiver. This paper describes a new family of codes, called multiplexed codes, that confine the de-synchronization phenomenon to low-priority data while reaching asymptotically the entropy bound for both (low- and high-priority) sources. The idea consists of creating fixed-length codes for high-priority information and of using the inherent redundancy to describe low-priority data, hence the name multiplexed codes. Theoretical and simulation results reveal a very high error resilience at almost no cost in compression efficiency.     

Analysis of TFCI coding performance of WCDMA systems

In WCDMA system, transport format combination indicator (TFCI) is encoded by an encoder based on Reed-Muller code and transmitted in a time-multiplexed fashion. When the number of TFCI information bits is less than the number of input bits to encoder, subset of basis sequences should be used. In this paper, we analyze the upper bound of word error rate (WER) of TFCI coding and find the optimal subset of basis sequences that minimize the bound. Since the bound of the WER is dependent on the channel correlation, the basis sequences to mitigate the effect of channel correlation are selected. From the result, a basis sequence with uniformly distributed bit of '1' is firstly chosen in optimal subset of basis sequences. The choice of basis sequences is more significant for high mobile speed.     

Generalized interframe vertex-based shape encoding scheme for videosequences

The efficiency of shape coding is an important problem concerning content-based image manipulations and object-based coding of the video sequences. In order to encode the shape information of an object, the boundary is approximated by a polygon which can be encoded with the smallest number of bits for maximum allowable distortion. The conventional boundary coding schemes, however, does not successfully remove the temporal redundancy of the video sequences. This paper proposes a new boundary encoding scheme by which the temporal redundancy between two successive frames is efficiently removed, resulting in lower bit-rate than the conventional algorithms. The interframe vertex selection problem is solved by finding the path with the minimum cost in the directed acyclic graph (DAG) and its fast version using a simplified graph is introduced to reduce the computational load. The vertices were selected from both the current frame to be encoded and the previous frame already encoded, and thus, the temporal redundancy was effectively removed.     

Generalization of Gallager's adaptive error control scheme

One of the simplest, yet most effective schemes thus far devised for the correction of errors on compound channels is the adaptive decoding scheme invented by Gallager. In this paper we present a generalization of this scheme which, at a modest sacrifice in rate, enables the decoder to correct a burst even when the guard space following the burst contains random errors. This is accomplished with the use of two convolutional codes,CandC^ {ast}, whereC^ {ast}containsC. At the encoder, the information sequence is first encoded withCand then, after a fixed delay, is encoded with a "shortened" version ofC^ {ast}, which is added to the parity sequences ofC. At the decoder there are two modes of operation, a random mode and a burst mode. In the random mode errors are corrected withCin a manner similar to that of the Gallager scheme. In the burst mode, the information bits in the bursty blocks are recovered from the later blocks where they have been superimposed on the parity bits. In this mode a decoder forC^ {ast}, which precedes the decoder forC, removes random errors from these later blocks, thereby greatly increasing the probability of recovery from the burst.