ADSL宽带接入技术

ADSL是XDSL的一种非对称版本.非对称数字用户技术ADSL(Asymmetric Digital Sub-scriber Line)是目前国际上用来对现有电话网络进行宽带改造的一种通信方式,是传输技术中最常见的一种.指出了ADSL的特点和接入技术.ADSL具有很高传输频率;可以直接使用原双绞线,可同时上网和通话;独享宽带安全可靠等优点.同时把ADSL技术与其他常见接入技术进行了比较.     

Broadband Utilization in Space: Effects of Population and Economic Structure

The Internet segment of the information and communications technology industry has been forecast to reach nearly 1.5 billion users by 2007. Generally referred to as broadband, a number of alternative technologies are now deployed broadly across the United States. This article utilizes a unique data set of 9000 survey responses generated by the Pew Internet and American Life Project in 2004 to examine the impact of several spatial factors, including population size and economic structure, on the likelihood of broadband utilization, after controlling for a set of demographic characteristics. The utilization of broadband is found to be greater with larger cities and in cities with large telecommunications-intensive economic sectors. However, demographic characteristics are also found to be quite significant and relatively stronger than geographic factors in determining broadband utilization.     

2-μm GaAs HBT工艺的L型网络分布式放大器

首先对分布式放大器中L型和T型网络的频率特性进行了研究.分析表明,L型网络比T型网络在设计中具有更好的频率特性.基于稳懋半导体的2-μm GaAs HBT工艺实现了一种L型网络的分布式放大器.测试结果表明,在3～18GHz频率范围内其增益为5.5dB,增益平坦度为±1dB,体现了很好的带宽性能.此外,在设计的频率范围内反射损耗S11,S22均低于-10dB.在5GHz时的1dB压缩点处输出功率为13.3dBm.芯片面积为0.95mm2,在3.5V电源下功耗为95mW.     

Theft in a wireless world

I explore philosophically the phenomenon of home wireless networks as used to share broadband Internet connections. Because such networks are frequently unsecured, third parties can use them to access the Internet. Here I consider carefully whether this kind of behaviour should be properly called theft. I begin with a brief non-technical introduction to 802.11 wireless networks. Subsequently, I present a four part argument – appealing to the unsecured nature of the networks discussed, entrenched software and hardware behaviours, trespass law, and the openness of ‹public park’ spectrum – suggesting that this kind of behaviour is permissible and should not be construed as theft. Substantively, I conclude that, despite the quite compelling considerations that these arguments bring to bear, this behaviour is theft. Additionally, I draw attention to significant flaws in the design and implementation of wireless technology (specifically in the out-of-the-box configuration for wireless access points and in the wireless connectivity of early versions of Windows XP) that facilitate the intentional and unintentional theft of Internet bandwidth. I suggest some simple mechanisms that could be incorporated into the technology which would serve to remove the ethical ambiguity in its usage by third parties, including adding the ability for a network owner to explicitly mark her network as not for public use,␣and changes to default hardware and software behaviours. I conclude by encouraging increased use of value-sensitive design practices in the development of future wireless technologies.     

Mapping and measuring the information society: A social science perspective on the opportunities,problems, and prospects of broadband Internet data in the United States

Abstract

There are concerns across government, industry, and academia over the inadequacies of data on broadband Internet connections. These inadequacies are important to consider because government policies and regulations, industry strategies, and scholarly research can be impacted by inaccurate or distorted data. Given that there are ongoing discussions about policy initiatives to improve these data, this article sets out to critically review publicly available data, identify important limitations of these data, and profile studies that have used these data successfully. In this review, the dynamic nature of broadband data will be discussed and the tradeoffs of pursuing further investments to create better databases evaluated. This evaluation suggests a more fruitful research path would be to recognize and work around existing data drawbacks, using the studies profiled in this article as examples, to explore a multitude of issues related to broadband availability, adoption, and use.     

基于流程的宽带接入服务顾客满意关键因素研究

把宽带接入服务流程分为业务宣传、售前咨询、业务注册、资费支付、软硬件安装、报障受理、故障解决等环节;通过在线调查,收回411份有效问卷,经过分析各环节的满意度与重要性差距、满意度数值和非常满意顾客所占比例,并对各环节的满意度与总顾客满意度进行相关分析和回归分析,最终确定出影响宽带接入服务顾客满意的5个关键因素,电信企业应该及时采取相应对策。     

The impact of rural broadband development: Lessons from a natural field experiment

Significant public investments in rural broadband internet service authorized by the American Recovery and Reinvestment Act raise new questions regarding the impacts of broadband on rural residents and communities. The results of a natural field experiment involving broadband internet projects funded by the Community Connect program of the Rural Utilities Service are reviewed here to provide a context for future evaluations of the effects of broadband infrastructure deployment and efforts to stimulate sustainable broadband use in rural areas. Based on pre-post surveys conducted in four communities in 2005 and 2008, the implementation of broadband infrastructure grants increased broadband adoption, although penetration also increased where a grant was awarded but later terminated. Public education efforts in a community participating in the ConnectKentucky initiative had an incremental effect on broadband adoption by positively affecting residents' perceptions of broadband service. Impacts on individual economic development activities and community satisfaction were not found. Implications for rural broadband initiatives and future evaluations of their effects are drawn.     

Rob Kling Remembered: The Early Beginnings of Social Analysis of Computing in the URBIS Project 1

This article challenges conventional policy development and evaluation approaches that emphasize the instrumental side of technology. There is a growing gap between conventional planning and evaluation approaches for rural broadband ICTs that seek to demonstrate a direct link between investments and results on the one hand, and on the other, with evidence that the contribution of ICTs to rural economic, social and cultural wellbeing is increasingly difficult to demonstrate beyond short-term measurable indicators. The article proposes an alternative paradigm based on sociotechnical systems, stakeholder engagement, an acknowledgment of the multiple dimensions at play, and the growing evidence of unpredictability of ICTs. The article emphasizes a perspective based on “contribution,” not attribution; policymaking that is both adaptive and inclusive of multiple perspectives; methodological testing of emerging evaluation methodologies; and projects as learning experiments. This alternative theoretical and policymaking paradigm is encapsulated in a metaphor based on the management of natural resources where stakeholders track their own indicators of impact by reading how the system responds to a project intervention.     

GII发展态势及其对计算机和通讯技术的影响

GII是信息技术发展中一个重要概念 ,文章对GII的由来和含义做出明确的解释 ,并对其发展态势———三网融合进行定性描述 ,最后阐明GII对计算机和通讯的影响以及计算机和通讯技术在GII中作用     

易通话计划与软件无线电

在介绍易通话计划、软件无线电的基本概念和系统结构的同时,分析了实现软件无线电的关键技术.