基于BDD的组合电路等价性检验方法

文章分析了目前常用的等价性检验方法的特点，包括功能性和结构性的验证方法，讨论了基于二叉判决图（BDD）的组合电路等价性检验方法，并分析了等价性检验过程中的误判问题及其消除方法，然后给出了一种关于带黑匣子的部分实现的隐式等价性检验方法，实验结果表明了该方法的有效性。     

一种新颖的基于层划分的等价验证方法

提出了一种基于SAT问题的组合电路等价验证算法，该算法特别适用于验证有着一定相似部分的两个电路。其主要创新之处为：1)基于层划分的配对点生成方法；2)基于值控制的回溯过程。ISCAS’85的实例很好地证明了该算法的有效性。     

基于存储元素映射的层次化等价性检验方法

为了提高验证效率和处理大规模电路的能力,提出了一种基于存储元素映射的层次化等价性检验方法,该方法将功能性和非功能性的映射方法相结合,提高了存储元素匹配的准确性和完备性.针对一款RSIC CPU设计完成了两组等价性验证实验,结果表明此方法具有很强的实用性.     

一种基于状态转换图的时序电路等价验证算法

提出一种基于状态转换图的时序电路等价验证算法。此算法通过验证两时序电路的状态转换图是否同构．得到两电路是否等价的信息。若两状态转换图同构，则两图中的状态可一一匹配为等价状态对，算法将状态转换图存储为待验证等价状态对的形式，若所有待验证等价状态对均为等价，则两时序电路等价，反之，则不等价。此算法对ISCAS89测试电路进行验证，与基于BDD方法的SIS系统和基于时间帧展开算法相比，均有较好的结果。     

基于改进型SAT求解器算法的组合电路等价性检查研究

随着工艺节点的缩小,集成电路规模的增加,集成电路设计过程中逻辑等价性检查在确保设计功能正确性方面起着重要作用。文章研究了组合电路逻辑等价性检查技术,针对该领域常用的DPLL和CDCL算法存在的问题,提出了一种基于蒙特卡洛树搜索的改进算法。通过对ISCAS85测试集的一个子集的实验,证实该算法对CDCL算法有一定的改进,应用于组合电路等价性检查的平均运行时间减少了20%。     

基于模型检测的URA—SAP安全性验证

在RBAC访问控制系统的安全性分析问题（RBAC—SAP）中,用户-角色分配相关的安全性分析问题（URA—SAP）是其中最重要的一个子问题,即用户-角色分配关系的变化对系统安全性的影响问题。提出了一种将URA—SAP转化为模型检测问题的自动化验证算法,实验表明采用该算法并结合现有的模型检测工具可以有效地解决URA—SAP问题。     

HFC宽带多媒体系统的安全技术

本简单介绍了HFC宽带多媒体系统所涉及到的各种安全技术，包括数字水印技术、有条件接收技术及局域网中的一些安全技术，同时就整个系统的安全运营提出了作本人的一些看法。     

并发系统模型检测中的状态约减算法

组合可达性分析是对并发系统模型分析验证的基础和关键,但是难于解决验证中的所谓的状态爆炸问题。对此提出了基于假定状态约减验证算法(ABSR),通过自动构造子系统接口定义来约束其状态规模,在验证过程中约减冗余状态,能更大程度降低状态爆炸几率和提高验证效率。借助假定-保证(Assume-Guarantee)算法有效性定理和组合可达性分析(CRA)算法安全性验证定理,证明该验证算法的有效性。通过采用通信系统演算(CCS)描述的任务模型为例证,证明上述算法比传统CRA算法更有效。     

A Novel Effective Bandwidth Based Call Admission Control for Multimedia CDMA Systems

A novel Call Admission Control(CAC)scheme is proposed for multimedia CDMA systems.The effectivebandwidth of real time calls is reserved in the CAC with the consideration of active factors.The admission of non-real timecalls is controlled by the system according to the residual effective bandwidth left from real time calls.Simulation resultshave shown that the novel CAC has greatly enlarged the admission region for real time calls and make the transmission de-lay of non-real time calls under an acceptable level.     

分布式多媒体存储系统中的全局缓存管理

多媒体存储系统必须同时支持连续媒体和非连续媒体的访问.由于连续媒体的实时要求,系统必须为访问连续媒体保留大量的磁盘带宽,并且持续很长的时间,这使其他类型文件的访问性能严重下降.本文根据连续媒体的访问特性,提出了一个分布式多媒体存储系统的协同缓存策略GLNU,充分利用系统中其他结点上可用的内存资源,提高缓存的利用率,以减少连续媒体的磁盘I/O,从而提高其他媒体的访问性能.仿真试验表明GLNU在各种不同的参数下,均优于现有的缓存策略,是一种适合分布式多媒体存储系统的缓存策略.     

Experience with Bayesian Reliability Measurement of Large Systems

Experience with two methods of Bayesian reliability measurement is described. An aerospace subsystem was evaluated assuming continuous gamma-distributed component failure rates. Priors were developed by conventional reliability prediction methods based on handbook data. The ``strength' of the prior was expressed in terms of variance about a predicted mean. Comparative evaluation was also made by a classical technique during a test program extending over 10 months. The Bayesian method was preferred though problems inherent in the method were apparent. More recently, a complex marine system was evaluated over a one-year period using a Bayesian formulation in which the failure rate is described by a discrete probability distribution with nonuniform cell widths. This technique avoids some of the operational problems of continuous formulations. Experience with Bayesian methods leaves little doubt of their utility as evaluation tools. The philosophical problems, however, remain as intransigent as ever.     

普用型会议室多媒体系统的设计与选型

各类企事业单位都有圆桌会议室,在目前富媒体信息交流趋势下,会议室具备多媒体展示功能已必不可少.结合实际应用情况,设计了一种具有普适性、功能强、投资少的会议室多媒体系统.     

利用多媒体系统改善公共课教学环境

多媒体教学网络系统,是在计算机网络实现数据共享的基础上,将影视、图像、声音、及动画文字等各种多媒体信息,以及实时控制动态引入到教学过程中,实现多向实时交互传输的一种专用多媒体计算机网络教学平台。教师可以利用该平台同时对数百同学进行多媒体互动教学。文中以Lanstar教学网络为例,就系统在大学公共机房的使用效果以及系统的常用功能、在教学中的使用策略进行了探讨。证明在公共机房安装此类教学网络系统可以提高教学成效。     

Power Allocation and Control in Multimedia CDMA Wireless Systems

This paper proposes an analysis of outage performance of a Direct Sequence-Code Division Multiple Access (DS-CDMA) wireless system with heterogeneous traffic. Imperfections in closed-loop power control and the activity characteristics of any traffic source in the system are taken into account. For given requirements of signal-to-(noise + interference) ratio and outage probability of every user in the system, the system capacity is derived in terms of the maximum number of users of each class that can be accomodated. The optimization problem is explicitly solved for a system consisting of a single cell and an approach is outlined for solving the optimization problem in a multi-cell system. The analysis is carried out by resorting to various approximations of Multiple Access Interference (MAI), that require different methods for solving the optimization problem and yield different degrees of accuracy. From numerical results it is seen that optimal power allocation is essential to limit the effects of power control imperfections, mainly in the case of non uniform amplitudes of residual power fluctuations. In the second part of the paper, a performance study of fixed step closed-loop power control algorithms is presented. A detailed simulation of the power control loop evidences that fast fading phenomena can not be easily tracked, even at moderate Doppler spread. Statistics of residual power fluctuations are estimated and can be used to support the assumptions in the first part of the paper. Furthermore, second order statistics of the controlled channel are estimated, and second order outage statistics (average rate and duration of outage events) are derived as a quantitative measure of residual channel burstiness.     

Channel Estimation for Realistic Indoor Optical Wireless Communication in ACO-OFDM Systems

Terahertz wave has attracted wide attention for its great transparency, low photon energy and high imaging resolution. Experiments were performed to explore the basic application of continuous terahertz wave. Some articles for daily use were chosen and sealed as samples and detected by the continuous-wave terahertz imaging system. Then a foam specimen was made with inclusions placed in it and detected by the system. The experimental results demonstrate that the system can detect and image the shapes and locations of the samples and inclusions correctly, though the air hole defect in the foam specimen is difficult to identify. The different colors indicating the strength of the reflected signal help to distinguish the different materials. The work paves the way for our future research and application of continuous terahertz wave.     

Resource Allocation in OFDMA Wireless Communications Systems Supporting Multimedia Services

We design a resource allocation algorithm for downlink of orthogonal frequency division multiple access (OFDMA) systems supporting real-time (RT) and best-effort (BE) services simultaneously over a time-varying wireless channel. The proposed algorithm aims at maximizing system throughput while satisfying quality of service (QoS) requirements of the RT and BE services. We take two kinds of QoS requirements into account. One is the required average transmission rate for both RT and BE services. The other is the tolerable average absolute deviation of transmission rate (AADTR) just for the RT services, which is used to control the fluctuation in transmission rates and to limit the RT packet delay to a moderate level. We formulate the optimization problem representing the resource allocation under consideration and solve it by using the dual optimization technique and the projection stochastic subgradient method. Simulation results show that the proposed algorithm well meets the QoS requirements with the high throughput and outperforms the modified largest weighted delay first (M-LWDF) algorithm that supports similar QoS requirements.     

Scheduling Algorithms for Packet-Oriented MAC Protocols in Wireless Multimedia Systems

Future generation wireless multimediacommunications will require efficient Medium AccessControl (MAC) protocols able to guarantee suitable Qualityof Service (QoS) levels for different traffic classes whileachieving a high utilization of radio resources. This paperproposes a new scheduling technique to be adopted at the MAClevel in wireless access systems, named Dynamic Scheduling-Time DivisionDuplexing (DS-TDD), that efficiently managesvideo, voice, Web and background traffics. A theoretical approachis proposed in this paper to evaluate the DS-TDD performance withvoice and Web traffics. Simulation results have permitted tohighlight the following promising characteristics of the DS-TDDscheme: (i) a high capacity of real-time traffics isattained with a QoS insensitive to Web and background trafficloads; (ii) a high throughput can be guaranteed whilepreserving the QoS levels of the different traffic classes;(iii) heavier downlink traffic loads do not modify the QoSof uplink traffics. Finally, extensive comparisons with differentscheduling schemes proposed in the literature have permitted tohighlight the better performanceof DS-TDD.     

Taylor-Based Least Square Estimation in MIMO-OFDM Systems for Multimedia Applications

Wireless Personal Communications - Recent mobile telecommunication systems are using multiple-input multiple-output system (MIMO) collective with the orthogonal frequency division multiplexing...     

基于Sigma-Delta ADC在衡器中的应用

引言 目前,高精度和低成本是衡器的发展趋势,这就对高性能的信号处理提出了更高的要求.对1:3000或者1:10000的衡器来说,一个12或者14位的ADC似乎就可以满足要求.但是实际应用中ADC的精度需要达到20位.本文对此介绍了衡器审计的一些系统指标和设计思想,并着重于峰-峰值的噪声分辨率、ADC动态范围、增益漂移和软件滤波的提高.最后,通过具体的参考设计进行详细的数据分析.