The future of accessibility in disaster conditions: How wireless technologies will transform the life cycle of emergency management

By describing a transformed life cycle of emergency management, this paper re-envisions how emergency managers may prepare for, respond to, recover from, and mitigate against disaster impacts in the future. Additionally, this paper also reveals how the broader social, political, economic, and cultural levels must change to foment a culture of safety with and for people with disabilities. The authors use the framework to identify how future wireless technologies can empower people with disabilities with regards to individual (or household) emergency preparedness and in coping with the drastic life changes following a disaster.     

The Wi-Fi “congestion crisis”: Regulatory criteria for assessing spectrum congestion claims

“Wi-Fi congestion is a very real and growing problem.” So said then-Chairman of the FCC Genachowski in a recent proceeding, and this sentiment is widely heard. However, we are aware of very few engineering studies that have a bearing on this matter, and their conclusions are equivocal. Beyond this, evidence for “congestion problems” in the 2.4 GHz ISM band is anecdotal at best.While some users no doubt sometimes have service difficulties they ascribe to congestion, that is not sufficient to prove that there is a policy problem. In order to provide a basis for policy decisions, we offer an analysis of congestion metrics and results in the engineering literature. We conclude that there is little consensus on how to measure congestion, and that network metrics are difficult to correlate with user experience.We therefore propose a list of user experience-oriented service impairment criteria that, if met, would demonstrate that congestion exists to a degree that justifies regulatory intervention: For more than one of the key scenarios that are supported by an operator or technology there is a significant increase in the percentage of users who cannot complete a valuable task on a persistent, ubiquitous basis in spite of the use of state-of-the-art engineering/deployment best practices, and users׳ willingness to pay the market rate for the best available service level.Based on our assessment of public reports and experimental data, we conclude that there is currently no evidence for pervasive Wi-Fi congestion. We do not claim that the absence of evidence of congestion amounts to evidence for the absence of congestion. However, we do question the argument that congestion occurring somewhere, sometimes is a justification for regulatory intervention.     

一种提高无线环境中TCP性能的改进方案

本文针对无线信道的特点提出了一种用于提高无线环境中TCP性能的改进方案－Wireless-TCP，通过尝试对TCP的拥塞控制中时间的算法进行调整并增加Probe模块以应对无线信道中的长时间中断，保证TCP连接的存在，通过爱立信通信实验室的仿真实验验证了该改进方案的有效性。     

无线局域网安全技术研究

随着无线局域网技术的不断发展和应用,无线局域网已经成为网络应用的热点。本文从分析无线局域网存在的安全问题出发,阐述了无线局域网的安全现状,并提出了若干加强无线局域网安全的防范措施。     

Ad Hoc网络中的节能机制

Ad Hoc网络终端的连续工作时间是影响Ad Hoc网络实用化的关键因素，产业界也一直在寻求通过采用节能机制来延长终端工作时间的方法。本文对Ad Hoc网络中典型的节能机制进行了分类介绍和比较，对运用节能机制所面临的困难给予了阐述，最后给出了节能研究的发展方向。     

Quantifying the costs of a nationwide public safety wireless network

The existing US public safety wireless infrastructure consists of thousands of disparate systems built by separate local agencies. Problems with interoperability, cost, spectral efficiency, and limited functionality plague these systems but could be significantly reduced through the deployment of a single nationwide network that serves all public safety personnel. Two major efforts towards such a nationwide network are the federal-government-only Integrated Wireless Network (IWN) and an FCC-led effort to create a public-private partnership in the 700 MHz band; the future of both projects is uncertain due in part to concerns surrounding cost. This paper presents a model to estimate cost for two fundamental approaches to a nationwide network: a public-safety-only network and a public–private partnership which serves both public safety and commercial subscribers. We apply this general model to four network scenarios which differ in the amount and band of spectrum allocated as well as the number and type of subscribers (public-safety-only versus commercial and public safety) under three traffic scenarios: voice-only, data-only, and voice and data. We demonstrate that the nation's many small systems could be replaced with a single nationwide network with a small fraction of the tower sites and spectrum. The cost of building this new infrastructure is comparable to what is likely to be spent in just a few years on upgrading and maintaining the existing infrastructure. In addition, we show that these cost estimates are highly dependent on some key system design parameters including the public safety capacity required and signal coverage reliability, which must therefore be well-defined in advance.     

IEEE802.11b的DCF退避算法实现技术探究

本文研究了无线局域网IEEE802.11b的MAC层基于随机竞争的分布式协调功能（DCF：Distributed Coordination Funct0ion）的基本信道访问方式的实现技术。DCF主要包括载波侦听机制、随机退避机制、帧优先级机制等。它定义了两种工作方式,一种是基本访问方式CSMA/CA,基于物理信道的载波侦听;另外一种是基于RTS/CTS虚拟载波侦听,这种方式在CSMA/CA的基础上增加两个长度特别小的数据包RTS和CTS来克服＂隐藏终端＂问题。可以通过对这两种载波侦听机制的研究,并利用SDL图和状态转移图,完成退避算法的软件实现。     

无线数据传输的TTIB信号处理器的建模与实现

在多径传播信道中，因多径衰落导致的随机相位和幅度干扰会影响信号的接收效果，并且接收机和发射机都需要精确的频率参考，在此基础上发展起来的透明带内导音(TTIB)技术可以满足抗多径衰落与克服频率漂移的要求。以往的TTIB处理大多是利用DSP芯片来实现的，而本文对用FPGA这一新的方法来实现TTIB处理进行了探讨，并在EDA平台上理论地实现了THB的处理．从而说明基于FPGA平台也能有效地实现TTIB处理，并且在速度、灵活性以及成本上都具有优势。     

The 3G transition: Changes in the US wireless industry

The transition of the wireless industry from second generation (2G) to third generation (3G) is more than a simple technology upgrade. The industry's service profile will move far beyond telephony and services will converge with the computing and content sectors. This will bring many more players into this already huge industry. Thus the transition to 3G needs to be regarded as a major economic transformation as it requires a major reconfiguration of the existing value networks. Standards have traditionally been essential in the success of wireless services and will play an increasingly critical role in the future.Due to the on-going transition, wireless standardization has changed considerably—reflecting changes in the configuration of the value network. While the number of major air-interface standards has been reduced to just two, the overall number of standards bodies has increased by almost an order of magnitude while the number and scope of interfaces being standardized has grown at a breathtaking pace. This growth reflects the need to support the industry's new coordination requirements at critical interfaces in the value network. At the same time, the importance of the traditional standards development organizations (SDOs) has diminished as more nimble industry consortia have taken over the main responsibilities for standardization. The major standardization battlegrounds have shifted up the protocol stack to the service enabler level. In addition, the manufacture of handsets and other mobile communication devices is transitioning to a more horizontal industry structure. These changes, along with changes in the way value is extracted from new services and their influence on the reconfiguration of the industry are discussed.     

Impact of wireless telecommunications standards and regulation on the evolution of wireless technologies and services over Internet protocol

Beginning with the historical role and importance of multi-physical standards in wireless telecommunications for the future in the US, Japan and Europe, this paper provides a cohesive vision of how wireless communication, voice over Internet protocol (VoIP) is likely to develop. Also covered in this paper are its benefits, the technical and regulatory support required to realize this vision and an assessment of its potential impact on the structure of the telecommunications industry. Although the competitive structure of the Internet is relatively open, several factors, such as frequency allocation policy and radio interface standards, could block the efficient evolution of wireless services to an IP platform. The paper proposes two major technical requirements to enable effective competition in wireless VoIP and achieve greater technical productivity.