A multidimensional isomorphic operator and its properties-aproposal of finite-extent multidimensional cepstrum

We propose a new multidimensional homomorphic operator that replaces the conventional complex cepstrum transformation. We treat multidimensional signals of finite support since any signal we can actually observe and deal with is of finite support. We first show that for any sequence of finite support there exists a coordinate transformation that transforms the support of a given sequence into the first quadrant in the multidimensional signal space. We then propose a new multidimensional homomorphic operator Ψ which transforms a sequence of finite support into another sequence of finite support in the first quadrant. It is proved that the operator Ψ is an isomorphism between two multidimensional signal spaces of finite support where finite convolution and usual addition, respectively, are defined as binomial operations. It is also shown that unlike the conventional complex cepstrum, the proposed operator Ψ is quite simple to compute and requires no complicated procedure like phase unwrapping, while it maintains the special features of the conventional complex cepstrum transformation that are useful in homomorphic signal processing. Moreover we clarify some algebraic structure of the multidimensional signal space with the finite convolution as a binomial operation. Finally it is shown by a numerical example that the deconvolution system using the proposed operator Ψ gives a much better result than the conventional complex cepstrum method     

On the computation of complex cepstrum through differential cepstrum

A relation between complex cepstrum and differential cepstrum is derived. The problem of aliasing associated with the computation of complex cepstrum through differential cepstrum is demonstrated with an example.     

Moment generating functions of generalized fading distributions and applications

This letter provides novel expressions for the moment generating functions of generalized fading distributions, namely eta-mu and kappa-mu. Our results find applicability in the derivation of several performance metrics, such as average error rate (AER), of a broad class of modulation formats. For exemplification purposes, the AER of binary modulation schemes is derived. The novel expressions include several others available in the literature, such as those for Nakagami-m, Hoyt, and Rice.     

Optimal cepstrum smoothing

The cepstrum of a random process has proven to be a useful tool in a wide range of applications. The common cepstrum estimator based on the periodogram suffers from large variance, and, to a smaller degree, from bias. The variance can be reduced by smoothing. However, the smoothing may be performed in four different domains: the covariance, the spectral, the log-spectral, and the cepstral domain. We present the mean square error (MSE) optimal smoothing kernels in each domain for estimation of the cepstrum. The lower MSE bound of each of the four families of estimators are compared. We also demonstrate how the four MSE optimal estimators differ in robustness.     

TAP及其应用

TAP(Test Access Port/Traffic Access Port)是一种新兴的用于网络监测的硬件设备,它提供了一种在不中断网络正常流量的情况下,获得网络流量的方法.因此,TAP可以用来实现监测网络性能、解决网络故障、分析网络流量和阻止恶意攻击等一系列功能.文章阐述了TAP的产生背景、主要特点、工作原理及其应用.     

ADSL及其应用

用户接入网(从本地电话局到用户间)是电信网的重要组成部分,也是信息高速公路的“最后一英里”。为实现用户接入网的数字化、宽带化,用光纤作为用户线是用户网今后发展的必然方向,由于光纤用户网成本过高,提出了多项过渡性宽带接入网技术,其中ADSL(不对称数字用户环路)和HFC(光纤同轴混合网)是最具有竞争力的两种。     

The cepstrum: A guide to processing

This paper is a pragmatic tutorial review of the cepstrum literature focusing on data processing. The power, complex, and phase cepstra are shown to be easily related to one another. Problems associated with phase unwrapping, linear phase components, spectrum notching, aliasing, oversampling, and extending the data sequence with zeros are discussed. The advantages and disadvantages of windowing the sampled data sequence, the log spectrum, and the complex cepstrum are presented. The influence of noise upon the data processing procedures is discussed throughout the paper, but is not thoroughly analyzed. The effects of various forms of liftering the cepstrum are described. The results obtained by applying whitening and trend removal techniques to the spectrum prior to the calculation of the cepstrum are discussed. We have attempted to synthesize the results, procedures, and information peculiar to the many fields that are finding cepstrum analysis useful. In particular we discuss the interpretation and processing of data in such areas as speech, seismology, and hydroacoustics. But we must caution the reader that the paper is heavily influenced by our own experiences; specific procedures that have been found useful in one field should not be considered as totally general to other fields. It is hoped that this review will be of value to those familiar with the field and reduce the time required for those wishing to become so.     

Analytical expressions of 2-D complex cepstrum

An analytical expression for complex cepstrum of a 2-dimensional second-order (finite) real discrete signal is derived for minimum phase condition in terms of multinomial coefficients and signal values. The theoretical cepstral expression obtained agrees favourably with the actually computed cepsta using a reasonably large size DFT to minimise any effects of aliasing. A few important properties of 2-D cepstrum as an extension of the 1-D case are stated.     

Modeling of two-dimensional random fields by parametric cepstrum

A method is presented for parametric modeling of stationary random fields. The class of parametric models considered allows the most general elliptic field, and by linear constraints can include such special cases as isotropic, quarter plane, and separable fields. The technique, based on the cepstrum, has the great advantage of requiring only the use of fast Fourier transforms in the fitting process. Thus, unlike the fitting of two-dimensional autoregressions, no iteration is necessary. Other advantages are that any (Wiener) filters constructed from the fitted spectrum are guaranteed to be stable, and that the spectrum is guaranteed to be positive. Statistical tests for determining various special types of field from data are developed. The choice of model order is discussed as well.     

印刷纸电池及其在无线温度传感标签中应用

文章介绍了纸电池的基本结构和印刷制备方法，并讨论了印刷纸电池在无线温度传感标签中的应用。     

OFDM-PON技术及其应用

OFDM-PON(正交频分复用无源光网络)是目前光接入网研究热点之一。文章简述了OFDM-PON技术的研究背景,阐明了OFDM-PON的技术原理、网络架构和关键技术,对基于OFDM-PON的业务及带宽调度进行了研究分析,并对OFDM-PON技术的应用前景进行了展望。研究表明,与传统的PON相比,OFDM-PON系统不仅传输带宽大幅度提升,而且可以实现基于子载波、调制格式和时间的三维业务及带宽调度。     

Picosecond photoconductivity and its applications

Phenomenon of picosecond photoconductivity has gained importance recently due to ultrafast optoelectronic switching. We describe the various theoretical considerations, which need to be taken into account during any analysis to this phenomenon. It is also pointed out that the conductive as well as dielectric properties of the photo-induced plasma can be used to control the wave propagation depending on the wavelength of the electromagnetic waves. Various possible applications of this phenomenon are discussed.     

隧道技术及其应用

隧道技术（Ｔｕｎｎｅｌｉｎｇ）是一种通过使用互联网络的基础设施在网络之间传递数据的方式。使用隧道传递的数据（或负载）可以是不同协议的数据帧或包。隧道协议将其它协议的数据帧或包重新封装然后通过隧道发送。新的帧头提供路由信息,以便通过互联网传递被封装的负载数据。 这里所说的隧道类似于点到点的连接。这种方式能够使来自许多信息源的网络业务在同一个基础设施中通过不同的隧道进行传输。隧道技术使用点对点通信协议代替了交换连接,通过路由网络来连接数据地址。隧道技术允许授权移动用户或已授权的用户在任何时间、任何地…     

数据可视化技术及其应用

数据可视化是计算机学科的一个重要研究方向。文中简要介绍了数据可视化所需的技术：数据预处理、映射、显示以及可视化技术在医学、气象预报、工程及数据挖掘中的应用。     

群签名及其应用

综述了群签名及基应用方面的研究成果及发展状况。分析了现有的群签名方案中所存在的一些缺陷。指出了这方面研究目前所存在的问题及几个值得重视的研究方向。     

IDS的标准化及其应用

随着互联网安全的迅速发展,入侵检测技术正以其特有的优势发展成为安全领域的一项不可或缺的重要技术。为了更好地实现各IDS及其组件间共享信息以及协同通信,必须采用一套适用的标准来定义信息的格式、传输的方式等等。由互联网工程任务组(IETF)的入侵检测工作组(IDWG)提出的标准草案,包括三部分内容:入侵检测消息交换格式(IDMEF)、隧道轮廓(TunnelProfile)及入侵检测交换协议(IDXP)。然后针对该草案提出一些改进的方案并将之应用于分布式IDS中加以实现。入侵检测系统标准1. 入侵检测消息交换格式入侵检测消息交换格式描述了一种…     

极化合成孔径雷达及其应用

先进的对地观测卫星(即ALOS)在日本于2006年1月24日成功发射.在所携带的三个传感器中,L波段的相控阵合成孔径雷达(即PALSAR)能够使我们利用全极化的观测模式日夜对地球进行观测.尽管极化运行是实验性质的,但在世界上它首次为我们提供了星载的全极化数据.该文简单介绍ALOS卫星上的PALSAR系统、全极化数据的各种应用以及极化SAR图像分析结果.