移动网络通向未来之路--诺基亚论3G演进(上)

无线宽带是通信发展的一个重要方向,而技术的多元化使人们面临多种技术选择的困惑,诺基亚通过五个指标的评估提出了移动网络运营商技术演进的最佳选择.本刊将分两期刊登这篇文章.     

金象大药房如何实施VPN

北京金象大药房医药连锁有限责任公司隶属于北京金象复星医药股份有限公司，主要开展医药连锁经营业务。目前公司共有连锁门店300多家，2004年连锁店销售额达5亿多元。在成立至今短短的几年时间里，金象大药房己发展成为北京规模最大、知名度最高的医药连锁企业之一。     

The Effects of Filtered Channel Quality Feedback on Throughput of Proportional Fair Algorithm

1　IntroductionSchedulingalgorithmsarewidelystudiedforwirelesspacketdatasystems,whichgenerallyhavetwobasiccategories,oneisoptimizedforsystemthroughputandfairness[1～ 2 ] ,andtheotherisforthequalityofservice[3～6] .Forsystemswherepack etdataaretimedivisionmultiplexedacrossusersonthedownlink ,orfromBaseStation (BS)tomultipleMobileStations(MS) ,theBSusesschedulingalgo rithmstodecidewhichuseristransmittedto .ItisindicatedinRefs.[7,8]thatschedulingonlyoneus eratatimeisoptimalfromthepointofviewo…     

Power Management Based Grid Routing Protocol for IEEE 802.11 Based MANET

MANET(Mobile Ad Hoc Network)is a collection of wireless mobile nodes forming a temporary communica-tion network without the aid of any established infrastructure or centralized administration.The lifetime of a MANETdepends on the battery resources of the mobile nodes.So energy consumption may one of important design criterions forMANET.With changing the idle model to sleep model in the grid environment,this paper proposes a new energy-awarerouting protocol.Performance simulation results show that the proposed strategy can dynamic balance the traffic load in-side the whole network,extend the lifetime of a MANET,and without decreasing the throughput ratio.     

Analyses and Solutions of Specific Cases in Spatial Angles Calculation

1 Introduction “Spatial Angles Calculations” means that all the calculations of given and unknown parameters are related to calculating angles in 3D space. The functions and relevant parameters in 3D space are much more complicated than that in 2D space, i.e. on a plane. Professor Sun, based on his research conducting for more than a decade, presented a series of new algorithms to calculate angles in space which are valuable in both theory and applications[1]. The authors found that, in g…     

双程放大技术在光纤放大器中的应用

双程放大技术是一种高效率、低成本的实用化放大技术。本文介绍了双程放大技术的优点及在各种放大器中的应用。     

IMS将一统网络天下--爱立信IMS系统实现全IP的稳步过渡

IMS构建面向未来的网络结构目前,运营商开始把握时机引入面向未来的网络结构。而这种结构的核心就是IMS(IP多媒体子系统),一种能够帮助运营商逐步过渡到全IP(ALL-IP)网络的新技术标准。其原因显而易见,他们希望能够利用一个简单有效、低成本而且标准化的网络处理所有业务,标准化可以使运营商不受供应商的限制,随时选用最好的网络设备。但是,要将传统网络中所有网元升级到IP,不产生不必要的费用、不中断现有业务,并非易事;尤其是为所有业务建立可重复利用的、牢固且面向未来的平台更非轻易而举。爱立信宣布:其IMS标准现已准备就绪,可…     

A Survey of E-Commerce Security

E-commerce is a very active field of Internet research. A very important aspect of e-commerce is its security. Because of the variety of e-commerce applications, many security policies, protocols and techniques are involved in the deployment of the security. The related standards and protocols of e-commerce are studied in this paper. The general model of e-commerce security is set forth. In this model, two most important e-commerce protocols including secure sockets layer (SSL) and secure electronic transaction (SET) are analyzed. The open problems and new trends of e-commerce security are presented.     

具有刚性、经济性和导电性的聚丙烯

美国卡伯特塑料公司(Cabot Plastics)提供了一种价格低廉而具有优良刚性和高的弯曲模量的聚丙烯共聚物,作为它的Cabelec导电化合物系列的一部份。报导说Cabelec 3320用于抗静电容器和运输斗的生产是经济而合适的,目前已经有     

无线原来可以很"美的"--美的集团采用思科无线网络解决方案

广东顺德美的企业集团是目前国内家电企业中经营小家电较早、产品系列最多、市场份额最大的企业。最近3年内，美的集团的销售收入近乎翻了两番。美的也由此成为顺德市这一“家电王国”内第一家销售收入突破百亿元大关的企业。由于美的集团的迅速增长和扩大．迫切需要稳定、高效的数据网络来保证公司的日常运作和生产流程的管理。