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3G上网计费模式的问题实质依然是价格问题.供需关系决定价格的上限,而成本决定价格的下限. 3G上网带宽不是空气.目前,运营商折算到单个基站上的3G投资成本将近百万,每年运维成本几十万,但一个基站所能提供的上网带宽总共不过几兆,而这几兆带宽还被基站下所有用户共享.若运营商给用户提供的"3G高速上网"跟宣传的一样,那么全国只要有1%的人在用,三大运营商的3G网络恐怕统统都要瘫痪. 相似文献
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《广播与电视技术》2001,28(8)
Tech Trends公司最近出版的一份研究报告表明 :跟无效在线用户相比 ,有效在线用户 (使用时间每周不低于 30小时 )对所有的 i TV (交互电视 )应用更感兴趣。这份研究报告的题目为“交互电视应用和业务的机会 :市场利益和价格敏感性的分析”。该报告指出 :与上网和收看电视两项活动分别进行的非同时用户相比 ,在 PC上上网又同时收看电视的同时用户 ,对所有 i TV业务的兴趣要大得多。譬如 ,在有效在线用户中 ,68%以上的用户对基于 TV的Internet业务感兴趣 ;而对于非有效在线用户 (每周上网不到一小时的用户 ,包括未上网用户 )来说 ,上述相… 相似文献
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截至2007年底,我国手机上网用户达5000多万,其中一半是互联网用户,另外一半主要是WAP用户,只用手机上网。手机上网用户使得我国网民总数由原来预计的1亿8千多万人激增到2.1亿人。我国手机用户为5.3亿。目前200元的手机已经有上网功能,今后若干年内对于低收入人群和偏远农村地区用户,WAP手机上网将是上网的主要手段。 相似文献
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金陵石化炼油厂住宅小区网络改造方案 总被引:1,自引:0,他引:1
随着社会信息化的发展 ,我厂住宅小区原有的通信网络已无法适应用户对新兴网络业务的需求 ,主要存在以下两方面的问题。(1)用户上网还依靠拨号方式目前小区的住宅用户上网只能通过厂内电话拨号 ,这占用了我厂总机的出中继线 ,影响了正常的电话用户拨打外线电话。随着上网人数的增加和上网时间的延长 ,厂区电话的接通率明显下降 ,影响了厂区正常的工作和生活电话。因此 ,给小区提供一种宽带接入手段 ,为小区用户提供宽带网络服务将是大势所趋。(2)IP电话使用不方便目前 ,大多数用户的长途电话是以PSTN为主 ,价格比较高。而小区用户使… 相似文献
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The author observes that the social fabric of engineering, the support infrastructure of the profession, and the political and economic systems of the world are undergoing shifts that affect what engineering is, how it is accomplished, and what it should do. He asks what these changes mean in terms of the educational system and explores a few of these issues that lie between academia and the industrial environment beyond. He discusses the engineering curriculum as seen from industry, the role of continuing education, research in academia 相似文献
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"电路原理"与"信号与系统"课程的整合与优化 总被引:2,自引:2,他引:2
科学技术迅速发展,新兴学料不断增加,知识总量不断增长,迫使本科教育不断向着基础化方向发展,基础课程教学在本科教育中的地位愈来愈高。计算机技术的广泛应用,离散信号与系统的基础知识已是电气类各专业的必要的教学内容。因此基础课程要从根本上整体优化课程结构。本文提出了电气类专业“电路原理”与“信号与系统”课程教学改革方案,将两门课程教学内容进行整合与优化,并在实际教学过程中进行了教学试验,缩短了教学时间,提高了教学质量。 相似文献
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箔条和箔片的性能特性及其应用和趋势 总被引:6,自引:0,他引:6
从箔条和箔片用于干扰雷达测和扰乱、迷惑、转移或者引诱进攻出发,详细论述箔条、箔条云及箔片、箔片云的雷达散射截面、带度、平移速度、下降速度及转动等情况,空间和时间我、水平和垂直极化性能、多普勒频移效应以及频谱展宽特性等,通过箔条和箔片有效成火控雷达实例,提出对抗火控雷达的三个重要因素及其采取的对策。 相似文献
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Davis R.F. Kelner G. Shur M. Palmour J.W. Edmond J.A. 《Proceedings of the IEEE. Institute of Electrical and Electronics Engineers》1991,79(5):677-701
The deposition of silicon carbide thin films and the associated technologies of impurity incorporation, etching, surface chemistry, and electrical contacts for fabrication of solid-state devices capable of operation at temperatures to 925 K are addressed. The results of several research programs in the United States, Japan and the Soviet Union, and the remaining challenges related to the development of silicon carbide for microelectronics are presented and discussed. It is concluded that the combination of α-SiC on α-SiC appears especially viable for device fabrication. In addition, considerable progress in the understanding of the surface science, ohmic and Schottky contacts, and dry etching have recently been made. The combination of these advances has allowed continual improvement in Schottky diode p-n junction, MESFET, MOSFET, HBT, and LED devices 相似文献
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《Communications Magazine, IEEE》2008,46(9):52-56
Over the last 40 years in the semiconductor industry, one of the most reliable truths has been that "thepath forward is through integration." Moore's law and its various derivatives and cousins have illustrated how greater integration has provided tremendous benefits in cost, power, size, and performance. While shrinking process lithography has been a critical enabler of this trend, we should remember that tremendous innovation in device technology, circuits, system architecture, computer aided design (CAD), packaging, and many other areas have been necessary as well. The exponential integration phenomenon has not been limited to memory and microprocessors: mixed signal and radio functions have also seen striking advances in integration over the last 20 years, from cell phones to wireless LANs, integrated "systemon-a-chip" (SOC) transceivers have become prevalent in the circuits conferences, journals, and - in some applications - have even made it into commercial mainstream products. 相似文献
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在日本电视广播的发展过程中,电视信号技术、电视节目转播技术、发射机技术以及天线技术等发挥了不可替代的作用。这些技术在长达60多年的模拟电视广播中被大量的开发、使用,尤其是射频相关技术为日后地面数字电视广播的发展提供了重要参考。主要介绍了日本电视广播中该相关技术的发展,并进行了讨论。 相似文献
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目前所谓的全光网络一般指基于DWDM传送技术的光传送网络(OTN)。由于OTN的节点采用OADM和OXC技术,为解决目前点到点的DWDM技术在应用中不能实现灵活组网和当网络失效时不能有效进行保护的问题提供了一种解决方法,使得OTN具有传输容量大、组网灵活、网络具有可扩展性和可重构性、易于升级等特点,可透明传输具有代码格式的不同速率等级的用户数字信号,能够同时适应用户信号种类用服务种类不断增长的需求。 相似文献
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Cellular architecture partitioning can improve the performance of telecommunications systems. The model proposed by the author allows for changing the cell size for different services and the number of users. The cell size that will ensure the best possible performance and quality of service can be derived by the model. The main task of a telecommunication system is call processing. This includes identifying incoming calls, establishing a communication path for the duration of the connection, and disconnecting the call after the conversation has ended. Call processing uses different components of the software architecture and involves processes and messages performing different functions and accessing various resources. In addition, the system requires administration and maintenance that also involves processes using different resources 相似文献