基于Turbo码的图像数字水印技术

在详细分析数字水印系统等效信道的基础上，提出了一种基于Turbo码的图像数字水印算法．该算法利用Turbo码的纠错性能和人眼视觉特性，以实现静止图像中数字水印的嵌入和提取；在水印嵌入之前，对水印序列进行Turbo码编码，然后利用人眼视觉特性进行水印嵌入，并采用了Turbo迭代译码算法进行水印提取，最后进行了数值仿真和算法比较．实验结果表明，该算法降低了水印在传输过程中的误码率，提高了水印的抗攻击能力，同时较好地解决了水印的鲁棒性和不可见性之间的矛盾．     

基于子空间的空时分组码的解码

空时码解码算法往往假设信道状态信息(CSI)已经事先估计出,信道估计需要额外的运算量,而且信道估计误差使解码性能降低.本文提出一种基于子空间方法的空时分组码直接解码算法,利用空时分组码的结构,结合子空间算法,可以不需要信道信息,直接得到码符信息的闭式解.仿真实验结果表明,随着噪声子空间求解准确度的提高,直接解码算法性能逐渐接近使用确切信道信息的相关解码器.     

一种新的高功率微波折叠式谐振腔径向速调管振荡器

 提出一种高功率微波折叠式谐振腔径向速调管振荡器，用电子与电磁场相互作用的一维单电子模型分析了这种折叠式谐振腔径向速调管振荡器的特点。其特点为：径向尺寸小，起振电流低。用二维半PIC程序对折叠式谐振腔径向速调管振荡器进行数值模拟研究。结果表明，当二极管电压为380kV，电流为18kA时，输出微波功率峰值为1GW，主要微波频率为1.52GHz，输出微波为多频率成分微波。通过折叠式谐振腔的电子束得到很强的调制。     

CRC校验及其软件实现

数据通信技术是计算机网络技术发展的基础,已经成为现代生活中必不可少的一部分。但通过通信信道传输的数据往往会有差错的产生,而且差错的产生是不可避免的,我们的任务是分析差错产生的原因与差错类型,研究检查是否出现差错及如何纠正差错。循环冗余码(CRC)是目前应用最广的检错纠错编码方法之一。论述了CRC的教学原理及其在数据通信中的作用,并提出了用8031汇编语言实现CRC校验的程序设计。     

Binary caps with many free pairs of points

We introduce the following new viewpoint in the study of caps in PG(m,q). The objective is to maximize, among all caps of given cardinality in a given projective space, the number of free pairs of points, which we define as pairs of points not participating in any coplanar quadruple of points of the cap. We survey the known results (which were motivated by an application in statistical experiment design) and then we improve the known lower bound on the number of free pairs of points for q = 2 and the smallest cap sizes for which the maximization problem is non‐trivial. © 2006 Wiley Periodicals, Inc. J Combin Designs 14: 490–499, 2006     

Code Generation Framework for Grid Development

1Introduction Withrapidincreasinginnetworktechnologyanddis tributedcomputing,gridhasemergedfromitsinitial scientificbackground[1]andmadefirstattemptstostart acommercialusagewithaccesstonongrid relatedpro fessionalsandend users[2-5].Significantworkhasbeen …     

Using the Simplex Code to Construct Relative Difference Sets in 2-groups

Relative Difference Sets with the parameters (2a, 2b, 2a, 2a-b) have been constructed many ways (see davis, EB, jung, maschmidt, and pottsurvey for examples). This paper modifies an example found in arasusehgal to construct a family of relative difference sets in 2-groups that gives examples for b = 2 and b = 3 that have a lower rank than previous examples. The Simplex code is used in the construction.     

Prove the Minimal Delay of Complex Orthogonal Space-Time Block Code by Hadamard Matrix

1IntroductionWith the development of mobile communications inthe world Space-Ti me Block Code(STBC)fromcom-plex orthogonal designs have received extensive interestin Code Division Multiple Access(CDMA)system de-sign recently,see for example[1~3].Since the…     

Optimal binary covering codes of length 2j

The minimum size of a binary covering code of length n and covering radius r is denoted by K(n,r), and codes of this length are called optimal. For j > 0 and n = 2^j, it is known that K(n,1) = 2 · K(n?1,1) = 2^{n ? j}. Say that two binary words of length n form a duo if the Hamming distance between them is 1 or 2. In this paper, it is shown that each optimal binary covering code of length n = 2^j, j > 0, and covering radius 1 is the union of duos in just one way, and that the closed neighborhoods of the duos form a tiling of the set of binary words of length n. Methods of constructing such optimal codes from optimal covering codes of length n ? 1 (that is, perfect single‐error‐correcting codes) are discussed. The paper ends with the construction of an optimal covering code of length 16 that does not contain an extension of any optimal covering code of length 15. © 2005 Wiley Periodicals, Inc. J Combin Designs     

GPS伪随机码捕获算法研究

基于MATLAB环境对GPS的C/A码的捕获算法进行了研究。传统的滑动相关算法的主要缺点是需要做大量的滑动相关运算,导致搜索时间过长;为克服这一缺点,提出了一种新的改进算法,对采样数据先进行累加积分,然后做相关运算,可以有效地降低相关次数,使得捕获速度得到明显提高。这种研究方法也适用于其他系统的伪随机码的捕获研究。