Implementation of RNS-Based Distributed Arithmetic Discrete Wavelet Transform Architectures Using Field-Programmable Logic

Currently there are design barriers inhibiting the implementation of high-precision digital signal processing (DSP) objects with field programmable logic (FPL) devices. This paper explores overcoming these barriers by fusing together the popular distributed arithmetic (DA) method with the residue number system (RNS) for use in FPL-centric designs. The new design paradigm is studied in the context of a high-performance filter bank and a discrete wavelet transform (DWT). The proposed design paradigm is facilitated by a new RNS accumulator structure based on a carry save adder (CSA). The reported methodology also introduces a polyphase filter structure that results in a reduced look-up table (LUT) budget. The 2C-DA and RNS-DA are compared, in the context of a FPL implementation strategy, using a discrete wavelet transform (DWT) filter bank as a common design theme. The results show that the RNS-DA, compared to a traditional 2C-DA design, enjoys a performance advantage that increases with precision (wordlength).     

VLSI Architecture for Forward Discrete Wavelet Transform Based on B-spline Factorization

Based on B-spline factorization, a new category of architectures for Discrete Wavelet Transform (DWT) is proposed in this paper. The B-spline factorization mainly consists of the B-spline part and the distributed part. The former is proposed to be constructed by use of the direct implementation or Pascal implementation. And the latter is the part introducing multipliers and can be implemented with the Type-I or Type-II polyphase decomposition. Since the degree of the distributed part is usually designed as small as possible, the proposed architectures could use fewer multipliers than previous arts, but more adders would be required. However, many adders can be implemented with smaller area and lower speed because only few adders are on the critical path. Three case studies, including the JPEG2000 default (9, 7) filter, the (6, 10) filter, and the (10, 18) filter, are given to demonstrate the efficiency of the proposed architectures.Chao-Tsung Huang was born in Kaohsiung, Taiwan, R.O.C., in 1979. He received the B.S. degree from the Department of Electrical Engineering, National Taiwan University, Taipei, Taiwan, R.O.C., in 2001. He currently is working toward the Ph.D. degree at the Graduate Institute of Electronics Engineering, National Taiwan University. His major research interests include VLSI design and implementation for signal processing systems.Po-Chih Tseng was born in Tao-Yuan, Taiwan in 1977. He received the B.S. degree in Electrical and Control Engineering from National Chiao Tung University in 1999 and the M.S. degree in Electrical Engineering from National Taiwan University in 2001. He currently is pursuing the Ph.D. degree at the Graduate Institute of Electronics Engineering, Department of Electrical Engineering, National Taiwan University. His research interests include VLSI design and implementation for signal processing systems, energy-efficient reconfigurable computing for multimedia systems, and power-aware image and video coding systems.Liang-Gee Chen received the B.S., M.S., and Ph.D. degrees in electrical engineering from National Cheng Kung University, Tainan, Taiwan, R.O.C., in 1979, 1981, and 1986, respectively.In 1988, he joined the Department of Electrical Engineering, National Taiwan University, Taipei, Taiwan, R.O.C. During 1993–1994, he was a Visiting Consultant in the DSP Research Department, AT&T Bell Labs, Murray Hill, NJ. In 1997, he was a Visiting Scholar of the Department of Electrical Engineering, University of Washington, Seattle. Currently, he is Professor at National Taiwan University, Taipei, Taiwan, R.O.C. His current research interests are DSP architecture design, video processor design, and video coding systems.Dr. Chen has served as an Associate Editor of IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS FOR VIDEO TECHNOLOGY since 1996, as Associate Editor of the IEEE TRANSACTIONS ON VLSI SYSTEMS since 1999, and as Associate Editor of IEEE TRANSACTIONS CIRCUITS AND SYSTEMS II since 2000. He has been the Associate Editor of the Journal of Circuits, Systems, and Signal Processing since 1999, and a Guest Editor for the Journal of Video Signal Processing Systems. He is also the Associate Editor of the PROCEEDINGS OF THE IEEE. He was the General Chairman of the 7th VLSI Design/CAD Symposium in 1995 and of the 1999 IEEE Workshop on Signal Processing Systems: Design and Implementation. He is the Past-Chair of Taipei Chapter of IEEE Circuits and Systems (CAS) Society, and is a member of the IEEE CAS Technical Committee of VLSI Systems and Applications, the Technical Committee of Visual Signal Processing and Communications, and the IEEE Signal Processing Technical Committee of Design and Implementation of SP Systems. He is the Chair-Elect of the IEEE CAS Technical Committee on Multimedia Systems and Applications, During 2001-2002, he served as a Distinguished Lecturer of the IEEE CAS Society. He received the Best Paper Award from the R.O.C. Computer Society in 1990 and 1994. Annually from 1991 to 1999, he received Long-Term (Acer) Paper Awards. In 1992, he received the Best Paper Award of the 1992 Asia-Pacific Conference on circuits and systems in the VLSI design track. In 1993, he received the Annual Paper Award of the Chinese Engineer Society. In 1996 and 2000, he received the Outstanding Research Award from the National Science Council, and in 2000, the Dragon Excellence Award from Acer. He is a member of Phi Tan Phi.     

A Survey on Lifting-based Discrete Wavelet Transform Architectures

In this paper, we review recent developments in VLSI architectures and algorithms for efficient implementation of lifting based Discrete Wavelet Transform (DWT). The basic principle behind the lifting based scheme is to decompose the finite impulse response (FIR) filters in wavelet transform into a finite sequence of simple filtering steps. Lifting based DWT implementations have many advantages, and have recently been proposed for the JPEG2000 standard for image compression. Consequently, this has become an area of active research and several architectures have been proposed in recent years. In this paper, we provide a survey of these architectures for both 1-dimensional and 2-dimensional DWT. The architectures are representative of many design styles and range from highly parallel architectures to DSP-based architectures to folded architectures. We provide a systematic derivation of these architectures along with an analysis of their hardware and timing complexities. Tinku Acharya received his B.Sc. (Honors) in Physics, B.Tech. and M.Tech. in Computer Science from University of Calcutta, India, and the Ph.D. in Computer Science from University of Central Florida, USA, in 1984, 1987, 1989, and 1994, respectively. He is currently the Chief Technology Officer of Avisere Inc., Tucson, Arizona, USA. Dr. Acharya is also an Adjunct Professor in the Department of Electrical Engineering, Arizona State University, Tempe, USA. Before joining Avisere, Dr. Acharya served in Intel Corporation (1996–2002), where he led several R&D teams toward development of algorithms and architectures in image and video processing, multimedia computing, PC-based digital camera, reprographics architecture for color photo-copiers, 3G cellular telephony, analysis of next-generation microprocessor architecture, etc. Before Intel, Dr. Acharya was a consulting engineer at AT&T Bell Laboratories (1995–1996), a research faculty at the Institute of Systems Research, Institute of Advanced Computer Studies, University of Maryland at College Park (1994–1995), and held visiting faculty positions at Indian Institute of Technology, Kharagpur. He served as Systems Analyst in National Informatics Center, Planning Commission, Government of India (1988–1990). He collaborated in research and development with Xerox Palo Alto Research Center (PARC), Eastman Kodak Corporation, and many other institutions worldwide. Dr. Acharya is inventor of 88 US patents and 14 European patents. He authored over 80 technical papers and four books—Image Processing: Principles and Applications (Wiley, New Jersey, 2005), JPEG2000 Standard for Image Compression: Concepts, Algorithms, and VLSI Architectures (Wiley, 2004), Information Technology: Principles and Applications (Prentice-Hall India, 2004), and Data Mining: Multimedia, Soft Computing and Bioinformatics (Wiley, 2003). Dr. Acharya is a Fellow of the National Academy of Engineers (India), Life Fellow of the Institution of Electronics and Telecommunication Engineers (FIETE), and Senior Member of IEEE. His current research interests are in computer vision, image processing, multimedia data mining, bioinformatics, and VLSI architectures and algorithms. Chaitali Chakrabarti received the B.Tech. degree in electronics and electrical communication engineering from the Indian Institute of Technology, Kharagpur, India in 1984, and the M.S. and Ph.D degrees in electrical engineering from the University of Maryland at College Park, USA, in 1986 and 1990 respectively. Since August 1990, she has been with the Department of Electrical Engineering, Arizona State University, Tempe, where she is now a Professor. Her research interests are in the areas of low power embedded systems design including memory optimization, high level synthesis and compilation, and VLSI architectures and algorithms for signal processing, image processing and communications. Dr. Chakrabarti is a member of the Center for Low Power Electronics, the Consortium for Embedded Systems and Connection One. She received the Research Initiation Award from the National Science Foundation in 1993, a Best Teacher Award from the College of Engineering and Applied Sciences, ASU, in 1994, and the Outstanding Educator Award from the IEEE Phoenix section in 2001. She has served on the program committees of ICASSP, ISCAS, SIPS, ISLPED and DAC. She is currently an Associate Editor of the IEEE Transactions on Signal Processing and the Journal of VLSI Signal Processing Systems. She is also the TC Chair of the sub-committee on Design and Implementation of Signal Processing Systems, IEEE Signal Processing Society.     

VLSI Architecture for Lifting-Based Shape-Adaptive Discrete Wavelet Transform with Odd-Symmetric Filters

In this paper, a VLSI architecture for lifting-based shape-adaptive discrete wavelet transform (SA-DWT) with odd-symmetric filters is proposed. The proposed architecture is comprised of a stage-based boundary extension strategy and the shape-adaptive boundary handling units. The former could reduce the complexity of multiplexers that are introduced to solve the shape-adaptive boundary extension. The latter consists of two multiplexers and can solve the shape-adaptive boundary extension locally without any additional register. Two case studies are presented, including the JPEG 2000 default (9, 7) filter and MPEG-4 default (9, 3) filter. According to comparison results with previous architectures, the efficiency of the proposed architectures is proven.Chao-Tsung Huang was born in Kaohsiung, Taiwan in 1979. He received the B.S. degree from the Department of Electrical Engineering, National Taiwan University, Taipei, Taiwan in 2001. He is currently working toward the Ph.D. degree at the Graduate Institute of Electronics Engineering, National Taiwan University. His major research interests include VLSI design and implementation for 1-D, 2-D, and 3-D Discrete Wavelet Transform. cthuang@video.ee.ntu.edu.twPo-Chih Tseng was born in Tao-Yuan, Taiwan in 1977. He received the B.S. degree in Electrical and Control Engineering from National Chiao Tung University in 1999 and the M.S. degree in Electrical Engineering from National Taiwan University in 2001. He currently is pursuing the Ph.D. degree at the Graduate Institute of Electronics Engineering, Department of Electrical Engineering, National Taiwan University. His research interests include VLSI design and implementation for signal processing systems, energy-efficient reconfigurable computing for multimedia systems, and power-aware image and video coding systems. pctseng@video.ee.ntu.edu.twLiang-Gee Chen (S84–M86–SM94–F01) received the B.S., M.S., and Ph.D. degrees in electrical engineering from National Cheng Kung University, Tainan, Taiwan, R.O.C., in 1979, 1981, and 1986, respectively.In 1988, he joined the Department of Electrical Engineering, National Taiwan University, Taipei, Taiwan, R.O.C. During 1993–1994, he was a Visiting Consultant in the DSP Research Department, AT&T Bell Labs, Murray Hill, NJ. In 1997, he was a Visiting Scholar of the Department of Electrical Engineering, University of Washington, Seattle. Currently, he is Professor at National Taiwan University, Taipei, Taiwan, R.O.C. His current research interests are DSP architecture design, video processor design, and video coding systems.Dr. Chen has served as an Associate Editor of IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS FOR VIDEO TECHNOLOGY since 1996, as Associate Editor of the IEEE TRANSACTIONS ON VLSI SYSTEMS since 1999, and as Associate Editor of IEEE TRANSACTIONS CIRCUITS AND SYSTEMS II since 2000. He has been the Associate Editor of the Journal of Circuits, Systems, and Signal Processing since 1999, and a Guest Editor for the Journal of Video Signal Processing Systems. He is also the Associate Editor of the PROCEEDINGS OF THE IEEE. He was the General Chairman of the 7th VLSI Design/CAD Symposium in 1995 and of the 1999 IEEE Workshop on Signal Processing Systems: Design and Implementation. He is the Past-Chair of Taipei Chapter of IEEE Circuits and Systems (CAS) Society, and is a member of the IEEE CAS Technical Committee of VLSI Systems and Applications, the Technical Committee of Visual Signal Processing and Communications, and the IEEE Signal Processing Technical Committee of Design and Implementation of SP Systems. He is the Chair-Elect of the IEEE CAS Technical Committee on Multimedia Systems and Applications. During 2001–2002, he served as a Distinguished Lecturer of the IEEE CAS Society. He received the Best Paper Award from the R.O.C. Computer Society in 1990 and 1994. Annually from 1991 to 1999, he received Long-Term (Acer) Paper Awards. In 1992, he received the Best Paper Award of the 1992 Asia-Pacific Conference on circuits and systems in the VLSI design track. In 1993, he received the Annual Paper Award of the Chinese Engineer Society. In 1996 and 2000, he received the Outstanding Research Award from the National Science Council, and in 2000, the Dragon Excellence Award from Acer. He is a member of Phi Tan Phi. lgchen@video.ee.ntu.edu.tw     

一种新型基于提升算法的二维离散小波变换结构的实现

在提升算法原理分析的基础上，设计出一种采用提升算法的二维离散小波变换结构，改变了传统的提升算法先行后列的运算方式，将行列运算操作结合起来进行，这样，相比于传统结构，在基本不增加硬件单元的前提下，变换时间减小为原来的75％左右，提高了硬件效率。     

基于离散插值样条的提升小波变换

文中引入了一种对信号递归滤波的提升方法,该方法与通常的提升方法不同之处是使用IIR滤波器.探讨了空间域中基于离散插值样条的预测算子和更新算子的设计.提出的方法以插值为基础,只涉及信号的采样,不要求使用正交公式,更适合信号的处理.最后由数值仿真验证了该算法的性能,对于软阈值法小波系数去噪,提升小波变换T12同B9/7相比,前者略优于后者,提升方法的优点在于其设计上的灵活性和计算花费少.     

多级多维离散小波变换的快速提升计算

提升方法是计算离散小波变换的有效手段,它由一系列的提升步和拉伸变换组成.在计算多级和多维离散小波变换时,现有方法在每一次小波分解的过程中都做完整的提升步计算和拉伸变换计算.我们发现该方法存在运算过程的冗余,为此本文提出了一种称之为后拉伸变换的提升方法,基本思想是计算完所有的提升步后,再统一进行拉伸变换.它能减少离散小波变换的乘法运算量.例如,对图像与视频压缩中应用广泛的Daubechies 9/7小波,做一维5级分解时与现有方法相比,乘法运算减少20%,而二维5级分解时,乘法运算减少28%.     

一维离散小波变换VLSI结构分析设计

提升算法的推出使得离散小波变换硬件的快速实现成为可能。翻转结构在提升架构的基础上进一步提高运算速度。在此,对翻转结构的舍入误差进行了分析,在翻转结构的基础上,对提升步骤进行了合并,提出一种有效的DWT硬件实现方案。实验结果表明,通过采用流水线模式提出的这种硬件结构,在关键路径约束的条件下,可以充分利用硬件资源。     

A Programmable Parallel VLSI Architecture for 2-D Discrete Wavelet Transform

Many VLSI architectures for computing the discrete wavelet transform (DWT) were presented, but the parallel input data sequence and the programmability of the 2-D DWT were rarely mentioned. In this paper, we present a parallel-processing VLSI architecture to compute the programmable 2-D DWT, including various wavelet filter lengths and various wavelet transform levels. The proposed architecture is very regular and easy for extension. To eliminate high frequency components, the pixel values outside the boundary of the image are mirror-extended as the symmetric wavelet transform (SWT) and the mirror-extension is realized via the routing network. Owing to the property of the parallel processing, we adopt the row-based recursive pyramid algorithm (RPA), similar to 1-D RPA, as the data scheduling. This design has been implemented and fabricated in a 0.35 m 1P4M CMOS technology and the working frequency is 50 MHz. The chip size is about 5200 m × 2500 m. For a 256 × 256 image, the chip can perform 30 frames per second with the filter length varying from 2 to 20 and with various levels. The proposed architecture is suitable for real-time applications such as JPEG 2000.     

High-Level Cache Modeling for 2-D Discrete Wavelet Transform Implementations

The main implementations of the 2-D binary-tree discrete wavelet decomposition are theoretically analyzed and compared with respect to data-cache performance on instruction-set processor-based realizations. These implementations include various image-scanning techniques, from the classical row-column approach to the block-based and line-based methods, which are proposed in the framework of multimedia-coding standards. Analytical parameterized equations for the prediction of data-cache misses under general realistic assumptions are proposed. The accuracy and the consistency of the theory are verified through simulations on test platforms and a comparison is made with the results from a real platform.     

逆向工程中对离散点云的特征识别算法探究

基于逆向设计中点云处理的表面识别问题,本文提出了一种基于小波变换的离散点云数据的特征识别算法。首先将离散点云表示成小波变换可以处理计算的形式,然后在此基础上提出了具体的二维和三维离散点云的小波分解算法,最后引入实例,对二维离散点云的小波分解算法进行验证分析。实验结果表明本文提出的算法达到了对点云数据的特征分解的目的。将离散点云数据按特征分解从而提取出不同的特征成分,可以根据后期点云预处理的不同要求,将小波变换后的数据进行进一步的处理。     

逆向工程中对离散点云的特征识别算法探究

基于逆向设计中点云处理的表面识别问题,本文提出了一种基于小波变换的离散点云数据的特征识别算法。首先将离散点云表示成小波变换可以处理计算的形式,然后在此基础上提出了具体的二维和三维离散点云的小波分解算法,最后引入实例,对二维离散点云的小波分解算法进行验证分析。实验结果表明本文提出的算法达到了对点云数据的特征分解的目的。将离散点云数据按特征分解从而提取出不同的特征成分,可以根据后期点云预处理的不同要求,将小波变换后的数据进行进一步的处理。     

基于新的整型9/7小波变换的硬件设计

提出了基于新的整型9/7小波变换的硬件设计方案.整个系统采用流水结构,充分利用硬件存储资源,实现了行列变换的并行处理.同时把常系数乘法优化为较少次数的移位加操作,加快了运算速度,缩小了电路规模.采用VHDL语言对系统进行描述并在Quartus Ⅱ 5.0环境下仿真,经验证满足图像实时处理的要求,为后续实时压缩编码和传输提供了有利条件.     

二维实值离散Gabor变换与DCT在图像编码中性能的比较

介绍了二维实值离散Gabor变换(RDGT)的快速算法,并着重探讨了二维实值离散Gabor变换与二维离散余弦变换在图像编码中的性能及差异.     

基于提升算法的离散小波变换FPGA实现

离散小波变换是当今许多图像处理和压缩技术的基础,并得到了广泛的应用.本文以4阶Daubechies小波为例阐述基于提升算法的离散小波变换的原理,并给出其硬件实现架构,然后进行仿真,将仿真结果与Matlab软件实现结果进行比较,结果表明硬件实现与软件实现基本一致,该硬件架构与基于传统的卷积方法实现相比,可以减小硬件实现面积,并利用插入流水线寄存器的方法,缩短关键路径,提高运算速度.     

基于离散平稳小波变换的红外图像对比度增强

提出一种基于离散平稳小波变换的红外图像增强方法,对红外图像进行离散平稳小波 变换后,分别对各个分解层的高频子带利用所提出的非线性增强方法进行对比度增强。实验结果表明,本文提出的方法在有效的提高红外图像中目标对比度的同时,又能突出红外图像的细节部分信息。算法在性能上优于传统的直方图均衡法、反锐化掩膜法和基于离散正交小波变换的对比度增强方法。     

Real-Valued Discrete Gabor Transform of Linear TimeVarying Systems： Exact Representation and Approximation

An efficient algorithm for the representation and approximation of linear time-varying systems is presented via the fast real-valued discrete Gabor transform. Compared with the existingalg orithm based on the traditional complex-valued discrete Gabor transform, the proposed algorithm runs faster, can more edsily be implemented in software or hardware, and leads to a more compact representation. Simulation results are given for demonstration.     

Reconfigurable Discrete Wavelet Transform Processor for Heterogeneous Reconfigurable Multimedia Systems

In this paper, a novel reconfigurable discrete wavelet transform processor architecture is proposed to meet the diverse computing requirements of future generation multimedia SoC. The proposed architecture mainly consists of reconfigurable processing element array and reconfigurable address generator, featuring dynamically reconfigurable capability where the wavelet filters and wavelet decomposition structures can be reconfigured as desired at run-time. The lifting-based reconfigurable processing element array possesses better computation efficiency than convolution-based architectures, and a systematic design method is provided to generate the hardware configurations of different wavelet filters for it. The reconfigurable address generator handles flexible address generation for data I/O access in different wavelet decomposition structures. A prototyping chip has been fabricated by TSMC 0.35 μm 1P4M CMOS process. At 50 MHz, this chip can achieve at most 100 M pixels/sec transform throughput, together with energy efficiency and unique reconfigurability features, proving it to be a universal and extremely flexible computing engine for heterogeneous reconfigurable multimedia systems.Po-Chih Tseng was born in Tao-Yuan, Taiwan in 1977. He received the B.S. degree in Electrical and Control Engineering from National Chiao Tung University in 1999 and the M.S. degree in Electrical Engineering from National Taiwan University in 2001. He currently is pursuing the Ph.D. degree at the Graduate Institute of Electronics Engineering, Department of Electrical Engineering, National Taiwan University. His research interests include VLSI design and implementation for signal processing systems, energy-efficient reconfigurable computing for multimedia systems, and power-aware image and video coding systems.Chao-Tsung Huang was born in Kaohsiung, Taiwan, R.O.C., in 1979. He received the B.S. degree from the Department of Electrical Engineering, National Taiwan University, Taipei, Taiwan, R.O.C., in 2001. He currently is working toward the Ph.D. degree at the Graduate Institute of Electronics Engineering, National Taiwan University. His major research interests include VLSI design and implementation for signal processing systems.Liang-Gee Chen (S’84–M’86–SM’94–F’01) received the B.S., M.S., and Ph.D. degrees in electrical engineering from National Cheng Kung University, Tainan, Taiwan, R.O.C., in 1979, 1981, and 1986, respectively. In 1988, he joined the Department of Electrical Engineering, National Taiwan University, Taipei, Taiwan, R.O.C. During 1993–1994, he was a Visiting Consultant in the DSP Research Department, AT&T Bell Labs, Murray Hill, NJ. In 1997, he was a Visiting Scholar of the Department of Electrical Engineering, University of Washington, Seattle. Currently, he is Professor at National Taiwan University, Taipei, Taiwan, R.O.C. His current research interests are DSP architecture design, video processor design, and video coding systems.Dr. Chen has served as an Associate Editor of IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS FOR VIDEO TECHNOLOGY since 1996, as Associate Editor of the IEEE TRANSACTIONS ON VLSI SYSTEMS since 1999, and as Associate Editor of IEEE TRANSACTIONS CIRCUITS AND SYSTEMS II since 2000. He has been the Associate Editor of the Journal of Circuits, Systems, and Signal Processing since 1999, and a Guest Editor for the Journal of VLSI Signal Processing Systems. He is also the Associate Editor of the PROCEEDINGS OF THE IEEE. He was the General Chairman of the 7th VLSI Design/CAD Symposium in 1995 and of the 1999 IEEE Workshop on Signal Processing Systems: Design and Implementation. He is the Past-Chair of Taipei Chapter of IEEE Circuits and Systems (CAS) Society, and is a member of the IEEE CAS Technical Committee of VLSI Systems and Applications, the Technical Committee of Visual Signal Processing and Communications, and the IEEE Signal Processing Technical Committee of Design and Implementation of SP Systems. He is the Chair-Elect of the IEEE CAS Technical Committee on Multimedia Systems and Applications. During 2001–2002, he served as a Distinguished Lecturer of the IEEE CAS Society. He received the Best Paper Award from the R.O.C. Computer Society in 1990 and 1994. Annually from 1991 to 1999, he received Long-Term (Acer) Paper Awards. In 1992, he received the Best Paper Award of the 1992 Asia-Pacific Conference on circuits and systems in the VLSI design track. In 1993, he received the Annual Paper Award of the Chinese Engineer Society. In 1996 and 2000, he received the Outstanding Research Award from the National Science Council, and in 2000, the Dragon Excellence Award from Acer. He is a member of Phi Tan Phi.     

基于小波变换的数字信号符号率估计

小波变换对暂态信号有很好的检测能力。数字信号在其符号边界上具有暂态特性，即有幅度、频率、相位的变化。而且数字信号经过小波变换后其边界仍为暂态。因此利用二次小波变换，在未知信号类型的情况下，可对数字信号进行符号率估计，计算机仿真结果表明，该方法具有较高的精确度及抗噪性。     

一种基于离散小波变换和RC6的信息隐藏算法

离散小波变换在离散随机数字信号处理中占有重要地位,论文提出了一种基于离散小波变换和RC6的信息隐藏方法,通过一系列运算将明文图像隐藏于掩饰图像中。此方法独特之处是文中设计了一个相当于密码本的位置矩阵表,它很好地解决了通讯双方的密码同步问题。由于使用只有通讯双方才知道的位置矩阵表以及每次通讯时位置矩阵表要进行混洗和掩饰图像加以更换,因此实现了密码设计中加密算法可以公开,密钥必须保密的设计思想,同时实现了一次一密。