基于西门子工业无线通信在电解行车上的应用

西门子工业无线局域网是一种由SIMATIC Net提供的无线网络,其SCALANCE W产品系列为工业无线局域网应用而设计,特别适合于需要可靠的无线通信的工业应用,支持IEEE802.11n/a/b/g等国际标准。基于西门子无线通信在电解32 t行车和机组上的应用实例,对西门子工业无线局域网及产品SCALANCE W700的组态和维护进行介绍。     

无线局域网技术概述

本文论述了近年来发展迅速的无线局域网技术,并通过实际工程案例,介绍了相关的知识。     

到Wi-Fi淘金

蓝牙,WAP(无线通信协议)、3G(第三代移动通信技术)等技术或协议都曾经风光无限,可现在,业内人士普遍认为它们“早熟”了,蓝牙、WAP已成“明日黄花”,3G则迟迟没有到来。Wi-Fi(无线局域网)是眼下的新宠,但愿它的未来不是梦。     

企业无线局域网技术标准浅析

随着企业移动应用的逐步推广,用户对无线局域网的服务质量要求日益提高。目前适应企业移动应用需求的无线局域网标准还相对空缺。参考相关行业技术标准,提出了贯穿网络设计、安装施工、验收测试3个阶段的企业无线局域网技术规范编制思路,为企业无线局域网建设和运维工作的标准化和规范化提供了借鉴。     

局域网ARP攻击分析及安全防范措施

本文结合一起局域网ARP攻击实例,分析了局域网ARP协议存在的缺陷及攻击原理,提出了具体的防范措施。     

天坛医院打造无线医院

移动计算技术不断改变着人们的生活方式,随着医院各种信息化应用的不断深入,无线局域网技术作为一种新兴的组网技术,正在被广泛地应用在医疗系统中。在Intel公司的帮助下,北京天坛医院在30个病区架设了采用IEEE802．11b无线接入技术的无线局域网。通过平板无线电脑、PDA等移动终端,现在北京天坛医院的医护人员可以随时用平板无线电脑、PDA等手持终端设备接入医院的信息系统,查看病人所有的病历记录、检验、化验报告单、影像图,直接在病人的床边更新医嘱信息。     

无线传感器网络路由协议的安全性研究

介绍了无线传感器网络中常用的路由协议,指出这些路由协议在设计时并不是以安全性为主要目标,无线传感器网络的特性使它面临着比传统网络具有更大的不安全性。分析了这些协议中存在的安全漏洞,指出了针对路由协议的安全攻击行为,最后给出了安全对策。     

EPP协议在车载地震仪中的设计与应用

针对并行口设备开发的趋势及特点 ,详细介绍了 EPP协议的产生、特点及时序 ;并结合科研项目“ES2 42 0地震仪改造”提出了用 EPP协议仿 Intel 80 86系统接口的详细设计方案 ,该接口由读写逻辑生成电路、地址锁存器及译码器、仿 Intel 80 86总线及一些逻辑延时电路组成。并给出了电路框图及 Windows3 .x/95/98编程。经扩展后总线的双向通信速度为 850 KB/s与 ISA总线的速度相当。     

TD-SCDMA系统智能天线波束形成算法的研究

TD-SCDMA系统基站端的智能天线通过波束形成能够显著减小多址干扰,改善通信质量.提出了一种加入扩频序列的协方差矩阵求逆最小二乘恒模(SMI-LSCMA)波束形成算法,该算法在SMI-LSCMA基础上利用特定用户信号的扩频序列信息来锁定该用户接收信号,这样可以使权值向量更新算法更快收敛.经过仿真验证,该算法具有较好的...     

Linux和Windows之间的文件共享

一个局域网内常常存在着多种操作系统,在这些操作系统中比较流行的就是Windows和Linux操作系统。局域网中往往需要在这2种操作系统之间实现文件的双向共享,使用Samba软件包就可以很容易地实现这一目的。本文首先介绍了SMB协议、Samba的配置,然后通过实例详细介绍了如何利用Samba实现Linux和Windows之间文件的双向共享,并说明了Windows98和Windows2000与Linux共享文件资源时的区别。     

Wi-Fi as a Commercial Service: New Technology and Policy Implications

While Wi-Fi has enjoyed explosive growth and deployment for use in residential homes, the rollout of commercial Wi-Fi service has been more limited. Part of the holdback on large-scale commercial deployment has been the strategic concern that the commons model to spectrum management lacks the incentives for service providers to invest due to the limited ability to manage interference in the unlicensed band. Today, however, this situation appears to have changed. To explain the new confidence by service providers in commercial Wi-Fi, the activities of the Wi-Fi Alliance and IEEE 802.11 standards body are analyzed to show how these groups essentially replicate many, but not all, of the functions traditionally employed by an effective band manager that is optimizing efficiency on a licensed spectrum block more typically associated with the deployment of commercial services. Consequently, with the Wi-Fi ecosystem functioning as an effective spectrum manager, it is concluded that the service provider investment in Public Wi-Fi networks is rational and the risk posed by saturation or overuse has been reduced to an acceptable level. The strategic implications of this finding on the Wi-Fi platform are the examined. How the requirements from service providers are already significantly influencing the evolution of the Wi-Fi standard is discussed, and an attempt is made to address the risks and liabilities associated with the unlicensed spectrum management model. Thus, service providers increasingly need functionality in Wi-Fi technology to manage interference, and monitor and improve network performance. The current ideas under discussion are elaborated for the next version of Wi-Fi to support both commercial Wi-Fi requirements, which address the interference concerns, but only up to a point, as the unlicensed model intrinsically leaves some risk to participants of spectrum saturation through overuse.     

Revisiting Wireless Internet Connectivity: 5G vs Wi-Fi 6

In recent years, significant attention has been directed toward the fifth generation of wireless broadband connectivity known as ‘5G’, currently being deployed by Mobile Network Operators. Surprisingly, there has been considerably less attention paid to ‘Wi-Fi 6’, the new IEEE 802.1ax standard in the family of Wireless Local Area Network technologies with features targeting private, edge-networks. This paper revisits the suitability of cellular and Wi-Fi in delivering high-speed wireless Internet connectivity. Both technologies aspire to deliver significantly enhanced performance, enabling each to deliver much faster wireless broadband connectivity, and provide further support for the Internet of Things and Machine-to-Machine communications, positioning the two technologies as technical substitutes in many usage scenarios. We conclude that both are likely to play important roles in the future, and simultaneously serve as competitors and complements. We anticipate that 5G will remain the preferred technology for wide-area coverage, while Wi-Fi 6 will remain the preferred technology for indoor use, thanks to its much lower deployment costs. However, the traditional boundaries that differentiated earlier generations of cellular and Wi-Fi are blurring. Proponents of one technology may argue for the benefits of their chosen technology displacing the other, requesting regulatory policies that would serve to tilt the marketplace in their favour. We believe such efforts need to be resisted, and that both technologies have important roles to play in the marketplace, based on the needs of heterogeneous use cases. Both technologies should contribute to achieving the goal of providing affordable, reliable, and ubiquitously available high-capacity wireless broadband connectivity.     

Oracle数据库的安全性讨论

数据库的安全性是 Oracle的一个重要特点 ,本文对 Oracle数据库的安全机制做了介绍 ,并对 Oracle数据库中的用户、口令、权限管理、审计和备份恢复等功能进行了详细的描述和讨论。     

第三代移动通信3GPP规范中的HSDPA技术

高速下行分组接入HSDPA(HighSpeedDownlinkPackageAccess)是第三代移动通信后继发展中非常重要的增强技术。HSDPA以5MHz的带宽向WCDMA的下行提供高达10～14Mbps的分组数据,用以实现多用户高速下行数据以及流媒体业务。本文通过研究高速下行分组技术的发展现状及在发展过程中遇到的问题,分析了影响该项技术发展的几个重要因素,并对这些问题提出了笔者的观点。     

TD向前冲

奥运的"高压锅"近期大幅推动了TD的发展,但奥运结束后很多问题也会浮出水面。"奥运期间一定能够提供3G服务!"中国政府许下的承诺,终于在某种程度上兑现了。     

局域网代理服务器的实现方案

在局域网中使用代理服务器 ,可以节省 IP地址和上网设备 ,提高整体上网速度并便于管理和起到应用级的防火墙作用。叙述了在局域网中使用代理服务器的方法 ,并以一具体的代理服务软件为例 ,说明了代理服务器的设置与使用。     

基于局域网的实时语音通信时延研究

在局域网中语音通信时延是影响语音质量的重要因素。为了最大限度地降低局域网中语音通信时延,提高语音质量,以采用低阶音频函数和UDP协议实现语音传输系统为基础,通过实验并分析了造成局域网中语音通信时延的主要因素,提出了在局域网中最大限度地降低实时语音通信时延的解决策略,实验数据证明,时延的分析是正确的,降低时延的策略是有效的。     

集装箱信息的条码化研究

现代集装箱码头很多作业已经实现了自动化或半自动化,但码头理货和闸口工作人员仍要用无线手提终端机人工输入集装箱信息。本文研究了使用条码技术(39条码和PDF417码)对集装箱信息进行编码。运用了文本压缩技术,将包含集装箱信息的PDF417码压缩为5行二维条码。通过将集装箱信息的条码化,并借助市场上已有的无线条码数据采集器扫描条码,可以实现码头理货和闸口工作人员录入数据的自动化,降低工作强度,提高生产效率。     

基于以太网接口的电源变换器的设计

以太网是现有局域网中最通用的通信协议标准,而以太网电源是以太网的基础设备。本文设计了一种基于以太网接口的15W DC/DC电源变换器模块电路。该电源由以太网接口电路和高效率DC/DC电源变换器2部分组成,模块中包含PoE识别信号阻抗、“0”类类型电路,采用MOSFET开关时,电源变换器的效率高达88％,PoE接口的效率可达97%以上。     

Spectrum Auction Design

Spectrum auctions are used by governments to assign and price licenses for wireless communications. The standard approach is the simultaneous ascending auction, in which many related lots are auctioned simultaneously in a sequence of rounds. I analyze the strengths and weaknesses of the approach with examples from US spectrum auctions. I then present a variation-the combinatorial clock auction-which has been adopted by the UK and many other countries, which addresses many of the problems of the simultaneous ascending auction while building on its strengths. The combinatorial clock auction is a simple dynamic auction in which bidders bid on packages of lots. Most importantly, the auction allows alternative technologies that require the spectrum to be organized in different ways to compete in a technology-neutral auction. In addition, the pricing rule and information policy are carefully tailored to mitigate gaming behavior. An activity rule based on revealed preference promotes price and assignment discovery throughout the clock stage of the auction. Truthful bidding is encouraged, which simplifies bidding and improves efficiency. Experimental tests and early auctions confirm the advantages of the approach.