一种新的低功耗图像及视频编解码算法

提出一种新的低功耗图像及视频编解码算法。该算法主要基于矢量量化,认为编码算法的质量和功耗地码本尺寸的大小,通过采用小尺寸码本,降低算法所需要的内存数量,从而降低功耗。编码时,利用分形理论中的同构变换计算虚拟码本,弥补由于采用小码本造成的图像质量损失,并使编码过程较少依赖于码本内存。编解码结果与全搜索型矢量量化算法相比,在不损失图像质量的前提下,可以极大地降低编解码功耗。     

静止图像小波系数嵌入式编码算法的研究

随着互联网的普及和图像应用范围的不断扩大,对静止图像的编解码算法的新的要求在不断提出,即要求在较高的压缩比基础上实现更多新的功能,如嵌入式编解码、从有损压缩到无损压缩等等。嵌入式零树小波编码(EZW),及在其基础上涌现出许多新的改进算法,如分层树的集分割算法(SPIHT),集分割的嵌入块编码(SPECK),最佳截断的嵌入式块编码(EBCOT)等,文中对这些算法的原理和性能进行了讨论,并说明了静止图像编解码的研究方向。     

一种基于H．264的运动估计改进算法

一、引言 H．264／AVC是由ITU-T和ISO／IECMPEG共同制订的新一代视频编码标准。这一编码标准可以获得很高的编码效率,尤其是在低码率视频编码方面比MPEG有明显的提高,非常适合低带宽质量网络视频的应用需要,但是,由于H．264为了提高编码效率,采用了许多高计算复杂度的算法,使得编解码计算量很大,因此为了实现实时编解码,就很有比较对其编解码算法进行优化。     

G.729编解码器在Blackfin537上的实现及优化

概述了ITU-G.729中共轭结构-算术码本激励线性预测编码(CS-ACELP)算法原理,结合了应用前景在Blackfin537平台上实现了定点编解码,针对算法特征及DSP体系结构特征对编解码关键部分进行了优化,达到了实时编解码要求。     

基于DSP的模糊增量调制算法的实现

首先阐述了模糊增量调制算法的编解码原理,再以TMS320C5402为核心的开发板上实现了此算法,实验结果表明此算法在DSP上有较好的编解码效果,基本实现了"透明"编码,达到了设计要求.     

EVRC语音编码算法研究及仿真

为了解决单一速率语音编码算法所带来的系统容量和频带利用率的浪费,第三代移动通信系统采用了变速率语音编码技术。介绍了一种用于第三代移动通信系统的EVRC(增强型变速率编解码)语音编码算法,简要地介绍了其编解码原理,着重分析了EVRC算法的关键技术:噪声抑制、速率判决、帧错误检测、自适应后置滤波等,并进行了该算法的浮点C代码仿真。仿真结果表明:该算法在较低的平均编码速率下获得了较高的合成语言质量。     

行业聚焦

DRA数字音频编解码技术简介广晟数码数字音频编解码算法(DRATM)是一种同时支持立体声和多声道环绕声的数字音频编解码技术,是《多声道数字音频编解码技术规范》的原型。该算法的特点是采用自适应时频分块(ATFT)方法实现对音频信号的最优分解,进行自适应量化和熵编码。其主要技术性能指标如下所示:     

基于LDPC码的数字喷泉编码

数字喷泉是近年发展起来的一类基于删除信道、面向数据分组的前向纠错编码技术,在广播类传输中具有明显的效率优势.该文提出了一种基于LDPC码的数字喷泉编解码方案,仿真结果表明,与已有的同类数字喷泉编解码算法相比,基于LDPC码的数字喷泉编解码算法具有更好的纠错性能和较低的编解码复杂度.     

数字对讲机语音编解码算法改进与优化

语音编解码算法是数字对讲机的核心。由于数字对讲机信道带宽和信道质量的限制,要求采用的数字语音编码算法在保证语音质量的情况下降低编解码速率,并且要求语音编解码算法有一定的容错能力。由于数字对讲机手持设备功耗的限制,要求数字语音编解码的算法复杂度尽可能低。文章对正弦激励线性预测（SELP）的2．4k语音编解码算法进行简化,在基本不降低语音质量的条件下大大降低了算法复杂度,并针对ARM9E硬件平台进行优化,最终在该平台上实现了该算法。     

基于TMS320VC5416的G.723.1语音编码算法的实现

G．723．1标准是一种针对语音的极低码率编解码算法，该标准提供了6．3kb／s和5．3kb／s两种码率的编码算法，两种码率都能提供较好的语音质量。本文从G．723．1编码算法和解码算法2方面介绍了G．723．1极低码率编解码器算法，并从硬件实现方面对TMS320VC5416的性能参数和技术指标进行了简要的介绍，最后从实时语音信号采集、实时语音编码模块、实时语音解码模块、语音输出模块等几个方面描述了G．723．1编解码算法在TMS320VC5416上的实现过程。研究结果表明。在TMS320VC5416DSK可以实现对语音信号的实时编解码。     

Theoretical analysis of the relationship between the Brillouin gain coefficient and the strain in the optical-fiber sensors

The relation between the power of the Brillouin signal and the strain is one of the bases of the distributed fiber sensors of temperature and strain. The coefficient of the Bfillouin gain can be changed by the temperature and the strain that will affect the power of the Brillouin scattering. The relation between the change of the Brillouin gain coefficient and the strain is thought to be linear by many researchers. However, it is not always linear based on the theoretical analysis and numerical simulation. Therefore, errors will be caused if the relation between the change of the Brillouin gain coefficient and the strain is regarded as to be linear approximately for measuring the temperature and the strain. For this reason, the influence of the parameters on the Brillouin gain coefficient is proposed through theoretical analysis and numerical simulation.     

Resolution Enhancement Technology:Integrated Process Solutions using OPC

DUV lithography, using the 248 nm wavelength, is a viable manufacturing option for devices with features at 130 nm and less. Given the low kl value of the lithography, integrated process development is a necessary method for achieving acceptable process latitude. The application of assist features for rule based OPC requires the simultaneous optimization of the mask, illumination optics and the resist.Described in this paper are the details involved in optimizing each of these aspects for line and space imaging.A reference pitch is first chosen to determine how the optics will be set. The ideal sigma setting is determined by a simple geometrically derived expression. The inner and outer machine settings are determined, in turn,with the simulation of a figure of merit. The maximum value of the response surface of this FOM occurs at the optimal sigma settings. Experimental confirmation of this is shown in the paper.Assist features are used to modify the aerial image of the more isolated images on the mask. The effect that the diffraction of the scattering bars (SBs) has on the image intensity distribution is explained. Rules for determining the size and placement of SBs are also given.Resist is optimized for use with off-axis illumination and assist features. A general explanation of the material' s effect is discussed along with the affect on the through-pitch bias. The paper culminates with the showing of the lithographic results from the fully optimized system.     

An improved parallel thinning algorithm with two subiterations

The parallel thinning algorithm with two subiterations is improved in this paper. By analyzing the notions of connected components and passes, a conclusion is drawn that the number of passes and the number of eight-connected components are equal. Then the expression of the number of eight-connected components is obtained which replaces the old one in the algorithm. And a reserving condition is proposed by experiments, which alleviates the excess deletion where a diagonal line and a beeline intersect. The experimental results demonstrate that the thinned curve is almost located in the middle of the original curve connectivelv with single pixel width and the processing speed is high.     

Alternative Schemes for Dynamic Secure VPN Deployment in UMTS

Three alternative schemes for secure Virtual Private Network (VPN) deployment over the Universal Mobile Telecommunication System (UMTS) are proposed and analyzed. The proposed schemes enable a mobile node to voluntarily establish an IPsec-based secure channel to a private network. The alternative schemes differ in the location where the IPsec functionality is placed within the UMTS network architecture (mobile node, access network, and UMTS network border), depending on the employed security model, and whether data in transit are ever in clear-text, or available to be tapped by outsiders. The provided levels of privacy in the deployed VPN schemes, as well as the employed authentication models are examined. An analysis in terms of cost, complexity, and performance overhead that each method imposes to the underlying network architecture, as well as to the mobile devices is presented. The level of system reliability and scalability in granting security services is presented. The VPN management, usability, and trusted relations, as well as their behavior when a mobile user moves are analyzed. The use of special applications that require access to encapsulated data traffic is explored. Finally, an overall comparison of the proposed schemes from the security and operation point of view summarizes their relative performance. Christos Xenakis received his B.Sc. degree in computer science in 1993 and his M.Sc. degree in telecommunication and computer networks in 1996, both from the Department of Informatics and Telecommunications, University of Athens, Greece. In 2004 he received his Ph.D. from the University of Athens (Department of Informatics and Telecommunications). From 1998–2000 was with the Greek telecoms system development firm Teletel S.A., where was involved in the design and development of advanced telecommunications subsystems for ISDN, ATM, GSM, and GPRS. Since 1996 he has been a member of the Communication Networks Laboratory of the University of Athens. He has participated in numerous projects realized in the context of EU Programs (ACTS, ESPRIT, IST). His research interests are in the field of mobile/wireless networks, security and distributed network management. He is the author of over 15 papers in the above areas. Lazaros Merakos received the Diploma in electrical and mechanical engineering from the National Technical University of Athens, Greece, in 1978, and the M.S. and Ph.D. degrees in electrical engineering from the State University of New York, Buffalo, in 1981 and 1984, respectively. From 1983 to 1986, he was on the faculty of Electrical Engineering and Computer Science at the University of Connecticut, Storrs. From 1986 to 1994 he was on the faculty of the Electrical and Computer Engineering Department at Northeastern University, Boston, MA. During the period 1993–1994 he served as Director of the Communications and Digital Processing Research Center at Northeastern University. During the summers of 1990 and 1991, he was a Visiting Scientist at the IBM T. J. Watson Research Center, Yorktown Heights, NY. In 1994, he joined the faculty of the University of Athens, Athens, Greece, where he is presently a Professor in the Department of Informatics and Telecommunications, and Director of the Communication Networks Laboratory (UoA-CNL) and the Networks Operations and Management Center. His research interests are in the design and performance analysis of broadband networks, and wireless/mobile communication systems and services. He has authored more than 150 papers in the above areas. Since 1995, he is leading the research activities of UoA-CNL in the area of mobile communications, in the framework of the Advanced Communication Technologies & Services (ACTS) and Information Society Technologies (IST) programmes funded by the European Union (projects RAINBOW, Magic WAND, WINE, MOBIVAS, POLOS, ANWIRE). He is chairman of the board of the Greek Universities Network, the Greek Schools Network, and member of the board of the Greek Research Network. In 1994, he received the Guanella Award for the Best Paper presented at the International Zurich Seminar on Mobile Communications.     

Characteristics of gradually doped LWIR diodes by hydrogenation

The hydrogenation effects on HgCdTe diode performance are presented and the mechanism of hydrogenation is revealed. By the hydrogenation, R₀A is increased by 30 times and photo-response is also improved. It is supposed that these are explained by the increased minority carrier lifetime by the hydrogenation. However, it is found from LBIC measurements that the minority carrier lifetime doesn’t increase by the hydrogenation. An important clue that explains the hydrogenation effects is found from Hall measurements. It is found that, after the hydrogenation, the doping concentration of Hg-vacancy doped substrate decreases and the mobility increases. For the heavily hydrogenated bulk substrate, it is also found that the hydrogen passivates the whole Hg-vacancy and reveals the residual impurity and p-type doping concentration is exponentially graded. From these measurements, the diffusion current model of gradually doped diode is proposed. This model shows that the diffusion current of the graded junction diode is 2 orders of magnitude smaller than that of the abrupt junction diode, which clearly explains the R₀A increase by the hydrogenation. Medicisimulation to investigate the change of LBIC signal by the doping grading also coincides with the measurements. From these measurements and model, the hydrogenation effects are attributed to the grading of Hg-vacancy doped p-type substrate by the diffused hydrogen.     

Study of waveguide coupling efficiency in hybrid silicon lasers

This paper presents a new method to increase the waveguide coupling efficiency in hybrid silicon lasers. We find that the propagation constant of the InGaAsP emitting layer can be equal to that of the Si resonant layer through improving the design size of the InP waveguide. The coupling power achieves 42% of the total power in the hybrid lasers when the thickness of the bonding layer is 100 nm. Our result is very close to 50% of the total power reported by Intel when the thickness of the thin bonding layer is less than 5 nm. Therefore, our invariable coupling power technique is simpler than Intel＇s.     

位屏蔽多叉树搜索射频识别防碰撞算法

针对RFID树型防碰撞算法中时隙数多、数据通行量大等问题,提出了一种改进的多叉树防碰撞算法,阅读器准确检测碰撞位并向标签反馈碰撞位信息,标签对阅读器已知的ID位进行屏蔽,把ID号转换成连续碰撞的序列号.阅读器利用屏蔽位信息和标签返回的碰撞位编码信息,对标签进行分层分类搜索.通过对标签ID进行屏蔽,阅读器和标签间仅发送对方不知道的碰撞位信息.该算法减少了碰撞时隙和识别时隙,避免了空闲时隙,减少了阅读器和标签间的数据通信量.理论分析和仿真结果表明,该算法减少了系统的时隙总数和数据通信量,提高了阅读器的识别效率.     

Design and nonlinearity compensation of Fabry-Perot type tunable optical filters for dynamic strain sensing systems

The collected spectrum of the fiber Bragg grating （FBG） and the loss of the detected optical power are discussed with respect to the 3-dB bandwidth of a Fabry-Perot （F-P） type tunable optical filter （TOF）, respectively. And the optimized parameters of the TOF are obtained consequently. It is demonstrated that the relationship between the transmission wave- length of the TOF and its drive voltage is nonlinear. A new method to compensate the nonlinearity of the TOF is proposed. The linear sweeping of the transmission wavelength of the TOF is achieved through modifying the drive voltage using interpolation algorithm. It is observed that the average error and the maximum error of the transmission wavelength are reduced sharply under linear fit. The dynamic strain sensing is realized by use of a reference FBG and moving averaging algorithm in this system.     

用FFT对8FSK信号进行解调方法的比较

随着DSP技术的发展,快速傅里叶变换(FFT)的应用越来越广泛。利用FFT算法对频移键控(FSK)信号进行频谱分布,通过比较FFT计算结果来确定信号的频率,可以实现对FSK信号的解调。采用MIL-STD-188-141A中的8FSK调制信号作为仿真信号,用MATLAB6.1对解调进行仿真。在提到的三种FFT的检测方案中,在没有频偏的情况下,第一种要较好;但当有频偏存在时,第二种方法较好。     

基于周期粒度的级间寄存器备份机制

单粒子翻转是空间环境下微处理器发生异常的重要诱因之一,随着集成电路特征尺寸的缩小,单粒子翻转不仅会引发单位错误,还会引发大量的多位错误,如何有效解决处理器所面临的多位故障是容错处理器设计面临的新挑战.本文提出了一种基于周期粒度的级间寄存器备份机制的容错方法,采用双流水线冗余结构,通过比较器对比两条流水线的级间寄存器以检测单粒子故障;以周期粒度对级间寄存器的内容进行备份,当检测到单粒子故障时,使用2个周期对流水线进行恢复;为避免脏数据流出流水线,在数据缓存和寄存器堆的入口设置写缓冲,通过延迟写入保证信息可靠性.本文基于实际的SPARC V8结构处理器,对提出的方法进行了具体实现,在实验平台上进行了仿真,仿真结果显示,本文提出的容错方法能够以一定的面积开销实现对SEU、SET、和MBU故障容错,加固处理器的主频最高可以提升70%.