华为3Com全千兆交换机家族添新成员

近日，华为3Com（简称H3C）展示了全千兆交换机家族的多位成员，这也是继去年H3C推出$5600以来，再次丰富全千兆接入交换机产品型态，这些产品形成了对二、三层安全智能全千兆交换机的全面覆盖。可以为用户提供更多的千兆接入选择。     

3Com新一代主干交换中心Switch 4007

本文介绍了３Ｃｏｍ公司的新一代主干交换中心Ｓｗｉｔｃｈ ４００７的特性和优点，回答了一些用户所关心的问题。     

千兆位以太网

1 千兆位以太网技术的标准及适用性 千兆位以太网的传输速率为1Gbps,是传统以太网的100倍。新的千兆位以太网标准与近1亿个以太网节点的安装基础保持兼容,维持以太网最初标准中的GSMA/CD访问方法,并包含全双工以及半双工操作模式,使目前的以太网用户能充分利用原有的投资。千兆位以太网标准将支持多模和单模光纤、短程铜线电缆(STP)以及远程铜线UTP(见表1)。     

3Com新一代主干交换中心Switch 4007

本文介绍了3Com公司的新一代主干交换中心Switch 4007的特性和优点,回答了一些用户所关心的问题。     

不容小看的千兆比特以太网交换机

最近，《数据通信》杂志与ＮＴＳＬ公司一起，对来自４个厂家的５种千兆比特以太网交换机进行了测试。测试比较全面，对每一部交换机都进行了１５项性能评测，其中包括速度性能、极端情况、特殊广播、媒体访问控制地址学习及第三层交换等。从这次评测结果可以看出，千兆比特以太网交换机性能有了很大提高，它除具有高速度外，还具备高端口密度、智能路由选择及服务质量等性能。     

千兆以太网和千兆路由交换机技术

本第一部分详细介绍千兆以太网的技术原理,并重点讨论千兆以太网的效率和可靠性问题。作为实现千兆以矿山多技术的产品,本第二部分详细介绍千兆路由交换机的系统结构,重点讨论在千兆路由交换机中线速和无阻塞的概念。最后针对广电现实的建网需求,提出在路由交换机选型时的五个主要标准。     

New structure for digital switching network

Methods for the design of cost-effective one-stage PCM switching networks composed of digital switching matrices are proposed. These one-stage networks have, in many cases, a more regular structure and contain fewer elements than networks currently known. The proposed one-stage networks can also be used as submodules for multistage networks.<>     

New architectures for optical TDM switching

A systematic theoretical study of architectures for optical TDM switching, using lithium niobate optical switches and optical fiber delay lines for storage, is undertaken. The architectures allow the bit rate and wavelength transparency of these devices to be exploited. A technique involving recursive definition and proof is used to define the networks, which are mathematically related to Benes and Waksman networks. This produces architectures that are very different from existing optical TDM networks. They exhibit economical use of components, which reaches the theoretical minimum in some cases. The use of feed-forward rather than feed-back delays give these networks superior crosstalk performance and more uniform attenuation than existing designs.<>     

1 GHz GaInAs:Fe photoconductive optical AND gate with approximately 100 fJ switching energy for time-division access fibre networks

A high-speed, three-port optical AND gate based on GaInAs:Fe photoconductive switches operating at lambda =1.3 mu m is demonstrated. An electrical power contrast ratio of 12 dB is obtained in optical-to-electrical time-division demultiplexing of a 1 GHz signal bit sequence by a 333.3 MHz clock with optical pulse energies of 100 fJ.<>     

FTTP技术的新宠--有源以太网

虽然无源光网络(PON)一直被美国的RBOC(地区性贝尔运营公司)选为光纤到驻地(FTTP)的支撑技术，但是仍有许多制造商和网络运营商推出另一种能够最佳利用以太网和IP(因特网协议)的有源以太网(Active Ethemet，AE)技术。为此，基于有源以太网网络结构和特点，从传输距离、成本、带宽、组网的灵活性、可靠性、维护的简便化等方面对两者进行了深入、细致的比较，最后得出结论，AE的优势明显，各网络运营商应该予以重视。     

承载新业务的电信级城域以太网

为了配合未来NGN和3G网络的大规模应用，国内各大运营商都在不断改造原有数据网络，力求做到为新业务提供有充分质量保证的网络平台。     

电波暗室1～18GHz性能的测试方法

文章介绍EMC电波暗室性能指标中与1～18GHz归一化场地衰减NSA、场地电压驻波比(SVSWR)和场均匀性(FU)三项指标相关的IEC/CISPR/A和IEC/SC77B委员会草案CISPR/A/342/CD、CISPR/A/531/CD和77B/429/CDV,这三项指标的校验和评估方法既适用于全电波暗室也适用于在接地平板上加铺适当数量吸波材料的半电波暗室.     

新一代的EPON网络管理系统

针对EPON系统是基于以太网的宽带无源光网络的特点和系统结构,提出了两种网络管理方式,然后介绍了EPON网络管理所需完成的功能。     

SDH网络承载以太网业务的新技术

介绍一种新的弹性分组环(RPR)技术。基于SDH的弹性分组环的网络带宽可根据用户的流量需要灵活分配。RPR环便于管理、易于扩展等特性为企业提供高性价比的网络解决方案,为运营商提供构造新型城域网的技术体制。     

Minimization of switching activities of partial products for designing low-power multipliers

This work presents low-power 2's complement multipliers by minimizing the switching activities of partial products using the radix-4 Booth algorithm. Before computation for two input data, the one with a smaller effective dynamic range is processed to generate Booth codes, thereby increasing the probability that the partial products become zero. By employing the dynamic-range determination unit to control input data paths, the multiplier with a column-based adder tree of compressors or counters is designed. To further reduce power consumption, the two multipliers based on row-based and hybrid-based adder trees are realized with operations on effective dynamic ranges of input data. Functional blocks of these two multipliers can preserve their previous input states for noneffective dynamic data ranges and thus, reduce the number of their switching operations. To illustrate the proposed multipliers exhibiting low-power dissipation, the theoretical analyzes of switching activities of partial products are derived. The proposed 16 /spl times/ 16-bit multiplier with the column-based adder tree conserves more than 31.2%, 19.1%, and 33.0% of power consumed by the conventional multiplier, in applications of the ADPCM audio, G.723.1 speech, and wavelet-based image coders, respectively. Furthermore, the proposed multipliers with row-based, hybrid-based adder trees reduce power consumption by over 35.3%, 25.3% and 39.6%, and 33.4%, 24.9% and 36.9%, respectively. When considering product factors of hardware areas, critical delays and power consumption, the proposed multipliers can outperform the conventional multipliers. Consequently, the multipliers proposed herein can be broadly used in various media processing to yield low-power consumption at limited hardware cost or little slowing of speed.