基于Galois域Reed-Solomon码的数据包层FEC编码软件实现

本文提出一种基于Galois域Reed-Solomon码的数据包层FEC编码软件实现方法。文中利用Galois域的运算封闭性和Reed-Solomon码的变换特笥解决了FEC编码等字长变换问题；通过查找表实现多项式运算，有效降低多项式运算的复杂度，提高了软件FEC编码的效率；文中还介绍了查找表的生成方法。实验表明，基于本文所提出的方法，能够用软件实现高效的数据包层FEC编/解码。     

基于VCM的对地探测卫星数据传输体制分析

针对常规数据传输体制在卫星过境过程中不能充分利用系统链路余量的情况,开展了基于可变编码调制方式的卫星数据传输体制研究。通过分析比较发现,可变编码调制传输体制较常规数据传输体制节约了大量链路余量,使数据传输量提高了35.5%。最后,对可变编码调制传输体制的实现方式给出了建议。     

图像的四叉树平面编码

该文提出了一种平面逼近图像编码方法及其四叉树实现方案。在最小二乘方准则下,对于给定的图像子块,找到一个最佳平面,并用其上的点逼近图像的像点。于是,只需要对该平面的三个描述参数进行编码,编码质量和图像子块的平坦程度和大小有关,因此,可按照对编码质量的要求,以四叉树结构选择可变大小的图像子块。     

基于FPGA的高速FIR滤波器的设计与实现

对FIR滤波器中的乘法如何在FPGA得到高效实现进行了研究.结合FPGA查找表结构,兼顾资源和速度的要求,采用改进的分布式算法,设计了20阶常系数FIR滤波器.在此基础上,用OBC编码对其查找表进一步优化.最后,在ISE13.1下进行综合,并在Modelsim下进行仿真,用Matlab分析得到的数据频谱,以确定达到设计效果.结果表明,该设计既节省了FPGA的资源占用,又提高了运行速度.     

视频流传输中的差错复原视频编码技术

视频压缩技术在采用预测技术、变换编码技术和可变长熵编码技术以减少冗余信息的同时,也降低了视频流的容错能力.传输信道中的差错,不仅严重损害了视频服务质量,甚至会使通信系统崩溃,因此,在有错信道上进行视频传输,差错复原视频编码技术就显得尤为重要.对差错复原视频编码技术进行了概括和总结,首先指出在视频传输过程中存在的由于传输错误而引发的比特流同步丢失及错误蔓延问题,然后研究了解决这些问题的差错复原视频编码方法,最后指出:可伸缩视频编码和多描述视频编码是差错复原视频编码的发展方向;多描述编码同多路径技术相结合,能显著提高压缩视频信号的错误恢复能力和传输信道的性能.     

RS编码器的CPLD实现

在分析了RS码编码原理的基础上，提出一种用CPLD实现RS编码器的简单可行的硬件实现方法。介绍了实现过程，给出了实现结果。结果表明运行查找表的方法具有成本低、速度快等优点。     

一种可变长码在视频编码中的应用

本文所讨论的一种可逆的可变长码，其码长分布与Golomb-Rice和exp-Golomb编码相同。其编码数据格式能够很好地应用于图像和视频的统计编码中，在保持编码效率的同时，很大程度地提高编码在信道传输中的纠错能力。     

基于多域并行编码的高速IPv6流分类

IPv6的多域流分类是高速路由器设计中的一个难点.本文提出了一种使用TCAM的高速IPv6流分类方案,其核心思想是:(1)区分IPv6包头5个域字段的不同特征,根据IPv6地址的特征及其分配信息对其进行压缩,对TCP端口域实施扩展的层次编码,根据统计数据对协议域进行压缩,最终结果是把原始域的296比特转换成280比特的查找关键字,与TCAM的表项宽度相匹配;(2)使用嵌入SSRAM表查找技术,对5个域并行进行独立编码,消除瓶颈编码环节,达到线速处理要求;(3)分类规则数据库按照本文预设计的编码方式存储在TCAM中,使用流水线技术让域的编码操作和查找操作并行执行,每个TCAM访存周期完成一次查找操作.同时,为解决范围匹配问题,本文设计了一种预定义位宽的动态范围编码算法,既节省了TCAM的存储空间,又提高了硬件规则库的更新速度.分析和仿真表明,当路由查找和流分类共用一个TCAM时,使用较低的工作频率(66MHz),流分类和路由查找速度均可达到22Mpps,满足高速OC-192接口的线速查找与流分类要求.     

易于硬件实现的内嵌图像编码算法

EZBC算法综合利用了子带内和子带间系数的相关性．把零树／零块结构和基于上下文编码的优点有机结合在一起,获得了比SPHIT算法更好的压缩性能,比EBCOT更高的压缩效率。但是EZBC算法编码中的两个排序链表需要很大且非固定的存储空间,这使得EZBC算法的硬件实现非常困难。在EZBC算法的基础上提出了一种易于硬件实现、低存储量、高压缩性能的内嵌零块图像编码算法。该算法利用比特平面节点重要性状态表和上下文查找表来完成整个编码过程和形成上下文。实验结果表明,所提出的算法具有与EZBC算法基本相同的高压缩性能,但所需存储空间约为EZBC算法的四分之一,所以该算法更易于硬件实现。     

一种适合硬件实现的高效算术编码

本文提出了利用表查找来实现二值算术编码,避免乘除法运算,可以简化硬件设计。该算法具有较小的概率逼近误差,因此性能退化较小。     

DWB-AES:基于AES的动态白盒实现方法

物联网设备因资源受限,需要兼具安全性、灵活性的轻量级密码模块保障安全,白盒密码能够满足物联网设备的安全需求。在常见的白盒密码实现方法中,往往密钥和查找表是绑定的,因此每次更换密钥都需要重新生成并更换查找表,这在实际应用中不够灵活。为了解决该问题,提出了一种基于AES的动态白盒实现方法,即DWB-AES。该方法通过改变轮与轮之间的边界,将加解密过程的所有操作均通过查找表来实现,并对表和密钥分别进行混淆,使整个加解密过程不会暴露密钥信息,且每次更换密钥时不需要更换查找表,所以DWB-AES更加灵活和实用。通过对DWB-AES的安全性分析表明,DWB-AES具有较高的白盒多样性和白盒含混度,且能够有效地抵御BGE和Mulder等常见的白盒攻击方法。     

High‐Speed Hardware Architectures for ARIA with Composite Field Arithmetic and Area‐Throughput Trade‐Offs

This paper presents two types of high‐speed hardware architectures for the block cipher ARIA. First, the loop architectures for feedback modes are presented. Area‐throughput trade‐offs are evaluated depending on the S‐box implementation by using look‐up tables or combinational logic which involves composite field arithmetic. The sub‐pipelined architectures for non‐feedback modes are also described. With loop unrolling, inner and outer round pipelining techniques, and S‐box implementation using composite field arithmetic over GF(2⁴)², throughputs of 16 Gbps to 43 Gbps are achievable in a 0.25 μm CMOS technology. This is the first sub‐pipelined architecture of ARIA for high throughput to date.     

Managing routing tables for URL routers in content distribution networks

Large‐scale content distribution networks (CDNs) can be built using URL routers to redirect client HTTP requests to the nearest content source. URL routers employ very large routing tables. To improve the manageability of CDNs, we propose to use URL signatures to reduce the size of routing tables and aggressive hashing to speed‐up routing look‐ups. Copyright © 2004 John Wiley & Sons, Ltd.     

SER‐Based Relay Selection for Two‐Way Relaying with Physical Layer Network Coding

To enhance the symbol error rate (SER) performance of the two‐way relay channels with physical layer network coding, this letter proposes a relay selection scheme, in which the relay with the maximal minimum distance between different points in its constellation among all relays is selected to assist two‐way transmissions. We give the closed‐form expression of minimum distance for binary phase‐shift keying and quadrature phase‐shift keying. Additionally, we design a low‐complexity method for higher‐order modulations based on look‐up tables. Simulation results show that the proposed scheme improves the SER performance for two‐way relay networks.     

Minimal-memory bit-vector architecture for computational mathematical morphology using subspace projections.

Computational mathematical morphology (CMM) is a nonlinear filter representation particularly amenable to real-time image processing. A windowed, translation-invariant filter is represented by a set of less-than-or-equal decisions that are executed by a parallel arrangement of comparators. In the state-of-the-art implementation, each pixel value of a windowed observation is indexed into separate lookup tables to retrieve a set of bit vectors which are "anded" together to produce a bit vector with a unique nonzero bit. The position of that bit is used to look up a filter value in a table. The number of stored bit vectors is proportional to the number of image gray levels. An architecture for CMM is presented that uses a minimal number of bit vectors so that required memory is less sensitive to the number of gray levels. The number of pixels in the observation window is the dimension of the image space. In the proposed architecure, basis elements are projected to subspaces of the image space and only bit vectors unique to each subspace are stored. Each projection corresponds to a subspace partition. Filter memory is greatly reduced by using intermediate lookup tables to map observations to unique bit vectors. We investigate two possible projection strategies: A fixed, singleton architecture, in which each subspace is one dimension, and a minimal architecture, in which a large number of subspace projections are searched for, one with minimal memory. Insensitivity to the number of gray levels is demonstrated through simulated, random-image space tessellations. We also present memory savings in a digital photocopier application.     

A New Timing-Driven Placement Algorithm Based on Table-Lookup Delay Model

There have been extensive studies on timing-driven placement in recent years.Theapproaches toward this problem fall into two main categories:net-based and path-based.In a typical net-based one,potential critical paths and acceptable d...     

An Efficient Paging Strategy Based on Paging Agents of Base Stations in Cellular Mobile Networks

We propose a new paging strategy to reduce paging cost by adding paging agents at base stations. When a mobile‐terminated call occurs, the base stations look up the paging agents to determine if terminal paging is actually to be made. An analytical model based on a Markov chain is used to evaluate the performance of the proposed strategy. The numerical results show that the proposed strategy significantly reduces the paging cost compared with the simultaneous paging strategy.     

利用大洋浮标数据和NCEP再分析资料对FY-2C红外分裂窗通道的绝对辐射定标

介绍利用大洋浮标数据和NCEP再分析资料对FY-2C红外分裂窗通道进行在轨绝对辐射定标的方法,并选择了2006年10个时次的卫星数据进行辐射定标试验.将利用这种方法获得的定标结果与FY-2C卫星数据产品中提供的定标查找表进行比较分析,结果表明两套不同的定标系数反演的大气层顶(TOA)亮度温度的主要差别集中在云顶、冰雪覆盖区域等低温像元;而在常温区的陆表和海表像元定标结果差别较小,反演的TOA亮温差在2K左右.提出的替代定标方法可以极大地提高定标频次,为实现FY-2C红外分裂窗通道的实时绝对辐射定标提供了重要的方法基础.     

Indirect angle estimation in switched reluctance motor drive usingfuzzy logic based motor model

In this paper, a novel rotor position estimation scheme is described that was developed to overcome the drawbacks of the previous sensorless techniques, which were proposed for switched reluctance (SR) motor drives. It is based on fuzzy-logic, and does not require complex mathematical models or large look up tables. The scheme was implemented by using a digital signal processor. The real-time experimental results given in this paper show that the position estimation method proposed can provide accurate and continual position data over a wide range of speeds (zero/low/high), and can also function accurately at different operating conditions (chopping/single pulse mode and steady state/transient operation)     

An improved floating-random-walk algorithm for solving themulti-dielectric Dirichlet problem

An improved floating-random-walk algorithm for solving the multidielectric Dirichlet problem is outlined. The improvement is achieved by using statistically generated Green's functions that are calculated beforehand and stored as lookup tables. These tables have been used to solve the multidielectric Dirichlet problem for an arbitrary two-dimensional geometry. The improved algorithm is also compared with the conventional floating-random-walk algorithm and is found to be at least two times more efficient. Results are presented for two types of parallel-plate geometries