对验证的量度：何时算充分？

Mentor Graphics公司首席验证科学家Harry Foster认为，今天的大多数设计经理要依赖于某种验证覆盖的量度来回答三个重要问题：我在哪里？去哪里？何时到？     

Multimedia Education in Computer Science: A Little Bit of Everything Is Not Enough

Media Impact usually focuses on the practical impact of multimedia research on IT business. Yet given the pervasiveness of multimedia technology in our everyday life, a thorough reflection on the impact of multimedia progress on education and, in particular, multimedia education is overdue. Multimedia teachers at the 2007 ACM Multimedia conference engaged in a panel discussion on the current state and future of multimedia education. In this issue's,Wolfgang Hürst of Utrecht University and his colleagues Gerald Friedland of the International Computer Science Institute, Berkeley, and Lars Knipping of Berlin University of Technology use this panel as an opportunity to argue the need for a dedicated multimedia curriculum in computer science education.     

越来越热的网络直播

<正>随着信息通信技术的不断发展及移动互联网和移动智能终端的日益普及,网络直播正以迅雷不及掩耳之势成功跻身移动互联网风口。无论是社交、秀场、教育,还是游戏、体育和娱乐,信息量更丰富、交互方式更便捷、互动性更强的网络直播都呈现出强劲的发展势头。"网络直播+"已然成为潮流,一众网络直播应用和网站纷纷涌现。网络直播已从让观众在网上收看电视节目的传统的"网络电视"式网络直播方式进化为更刺激,更具真正意义的"网络直播"方式,以新颖的样式和便捷的服务给观众带来全新的视角体验和视野冲击。     

基于压缩感知的单比特合成孔径雷达成像算法*

在合成孔径雷达系统中,要提高分辨率就意味着产生大量的回波数据,从而加重了数模转换器和存 储设备的负担。压缩感知理论的目的是在保证恢复稀疏信号的前提下降低采样率,而本文的目的是降低总的比特 率。本文提出了一种基于压缩感知的单比特合成孔径雷达成像算法,并通过仿真实验验证了该算法的性能。与匹 配滤波算法相比,该算法不仅能减少数据的总比特率,而且还能有效抑制目标的旁瓣和虚假目标。并且在低信噪比 条件下,该算法比传统的多比特压缩感知算法展现出更强的鲁棒性。     

见微知著:看FPGA小型化

当FPGA作为ASIC（专用集成电路）的廉价替代品首次面市时广受欢迎,FPGA不仅没有掩膜成本,而且易于修改设计,似乎FPGA只需要不断提高容量,就能够取代大部分产量有限的ASIC了。然而,经验表明,小容量FPGA在替代量产定制逻辑时更受青睐。[编者按]     

On One More Property of the Ideal Array Element Pattern

An infinite planar array of controlled elements in the form of overlapped subarrays excited through a multiport circuit is considered. It is analytically shown that the contour element (subarray) pattern with an ideal contour shape corresponding to the absence of backward mutual coupling and, as a consequence, to the 100% element efficiency can be exactly formed at a definite amplitude distribution over the densely arranged small ideal subarray radiators in spite of the fact that each such a radiator in the subarray has low efficiency caused by the presence of backward mutual coupling. If the small ideal radiators are controlled directly (without the multiport circuit), the contour pattern can be formed with 100% array efficiency for any shape of the contour. If the radiators are not ideal, then the efficiency of the array shaping the contour pattern is determined by averaging the mismatch efficiency of the uniformly excited array scanning over the region bounded by the contour pattern.     

一种考察CCR的ABR业务二值法流量控制方案

 本文提出了一种考察CCR的有关ATM网络中ABR业务的流量控制方案EFCI(CCR)算法,具有二值法算法简单的特点,并能保证带宽分配的公平性,能有效地控制交换节点队列的长度,且该算法在拓扑结构较为复杂的网络中性能良好.     

Enough already!

This publication contains reprint articles for which IEEE does not hold copyright. You may purchase this article from the Ask*IEEE Document Delivery Service at http://www.ieee.org/services/askieee/     

Fast Bit Gather, Bit Scatter and Bit Permutation Instructions for Commodity Microprocessors

Advanced bit manipulation operations are not efficiently supported by commodity word-oriented microprocessors. Programming tricks are typically devised to shorten the long sequence of instructions needed to emulate these complicated bit operations. As these bit manipulation operations are relevant to applications that are becoming increasingly important, we propose direct support for them in microprocessors. In particular, we propose fast bit gather (or parallel extract), bit scatter (or parallel deposit) and bit permutation instructions (including group, butterfly and inverse butterfly). We show that all these instructions can be implemented efficiently using both the fast butterfly and inverse butterfly network datapaths. Specifically, we show that parallel deposit can be mapped onto a butterfly circuit and parallel extract can be mapped onto an inverse butterfly circuit. We define static, dynamic and loop invariant versions of the instructions, with static versions utilizing a much simpler functional unit. We show how a hardware decoder can be implemented for the dynamic and loop-invariant versions to generate, dynamically, the control signals for the butterfly and inverse butterfly datapaths. The simplest functional unit we propose is smaller and faster than an ALU. We also show that these instructions yield significant speedups over a basic RISC architecture for a variety of different application kernels taken from applications domains including bioinformatics, steganography, coding, compression and random number generation.     

Discovering Services Is Not Enough

Faced with multiple electronic devices, service providers, and ISPs, tomorrow's mobile users might find it challenging to identify available services and acquire the rights to use them. The authors tackle this problem, combining the acquisition of role-based credentials with servicediscovery.     

100G光传送技术渐入佳境

高速Internet和视频业务的迅速发展,IP网络流量持续强劲增长,对运营商的骨干传送网络提出了更高的要求,100G光传技术因此应运而生。该技术在码型、复用方式、相干接收和前向纠错(FEC)等关键技术方面都有创新。对于100G传输商用设备,业界一般看好的长距传输码型是采用相干接收的偏振复用正交相移键控(PDM-QPSK),但由于目前模数转换器(ADC)和DSP芯片等处理技术水平的限制,几乎所有高速电信号处理芯片都没有商用解决方案,这是目前的技术攻关重点。近年来实验室和现网实验方兴未艾,预计基于100G的长距传送系统在1～2年后开始部署。     

宽带服务扮演越来越重要的角色

自2001年初宽带基础设施建设形成了新的网络热潮后,中国电信、网通、广电企业、长城宽带、蓝波万维等纷纷加入“战团”,宽带接入社区后,必然有完善服务内容、增加服务种类、服务更具个性化的需求。由此,宽带内容平台建设已经势在必行,专业内容服务提供商、宽带频道运营商等提供宽带内容的企业将在今后的宽带领域唱主角。 大家都知道,此番宽带内容建设有别于以往窄带内容的“大而全”,“小而全”的特点,不仅仅局限在新闻、聊天、发邮件等传统“项目”,而具备“宽带特色”的特点和特征。     

Bit Error Probability and Bit Outage Rate in Chaos Communication

This paper investigates the notion of the probability of bit error (PBE) and its distribution in chaos-based communication systems; these are seen as being the fundamental quantities to both the well-known bit error rate (BER) and the new concept in chaos communications of bit outage rate (BOR). The form of the distribution illustrates the degree to which bit error rate is a stable representation of performance. Bit outage rate is another measure of performance which gives practically helpful information about bit error. For a simple coherent chaos-shift-keying system the distribution of bit error probability is derived exactly, and theoretically exact formulas for the bit outage rate and bit error rate are presented. Two specific cases are developed to obtain useful qualitative and quantitative information. The cases concern independent Gaussian spreading, as a lower benchmark and logistic map spreading, as typical of effective chaotic spreading. Comparisons are obtained between these spreading distributions and between different extents of their spreading, calibrated against per bit signal to noise ratio. A general conclusion is that bit outage and bit error rates are complementary measures of performance.     

基于硬件的安全性设计

在今天的数字世界里面，远程访问正越来越普遍，语音、视频和宝贵的数据不断通过有线和无线连接进行传播。消费者下载视频和音乐，员工登陆公司网络，手机提供上网服务，家庭观看收费的电视节目。随着新的在线应用的出现，一系列的安全隐患摆在了人们面前。     

既能防水又能透气的机壳

在设计高性能电子系统时,工程师都明白进行器件保护是非常重要的问题,既要保护其免受干扰又要保护敏感电子器件不被损坏。随着人类越来越依赖电子系统,保护措施对于系统可靠性和使用寿命的保证变得至关重要。敏感且昂贵的电子系统的应用环境也大大拓展了。长期以来,电子系统已经被广泛用于从舰船技术到食品生产设备等几乎一切领域之中,而近年来无线通信设备的普及是电子系统应用扩展过程中的最新进展,甚至包括刮胡刀和牙刷在内的消费产品也需要保护其中的敏感元器件。然而,工程师发现的问题是,对于设备外壳(或机壳)而言,既需要阻止或防止外…     

移动本地传输网引入多厂家设备的策略

本文对移动本地传输网中引入多厂家传输设备进行探讨和分析,通过分析两种模式下引入不同厂家的设备对现网的影响,提出移动本地传输网中多厂家的引入策略和组网方式。