超宽带无线通信及其关键技术

本文从落实科学发展观、充分利用国内外两个市场、两种资源、拓展发展空间以及更好地处理内需与外需、利用外资与利用内资关系等角度论述统筹国内发展和对外开放的蕴涵,并从发展国民经济全局和实现现代化战略目标出发提出统筹国内发展和对外开放应采取"4个相结合"的对策措施。     

无线传感器网络代码更新技术分析

无线传感器网络是由大量形体较小、能源受限并且配置有计算能力和无线通信能力的传感器节点组成。无线传感器网络高度自主性的特点使其广泛用于军事、环境监测等危险或人力无法干预的地方。为了适应时间、环境和需求的变化,在传感器节点布置后,不可避免地要节点进行代码更新。代码更新由代码分发和代码更新模式两部分组成。现有的代码分发协议和代码更新模式在可靠性、能量有效性和节点重启的设计上存在问题和不足。因此,有必要设计一个可靠又能量有效的代码分发协议,并采用自主的代码更新模式。     

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.     

基于ZIGBEE的无线传感网络的研究与设计

本文简单讲述了无线传感器网络技术在实际中的应用,详细介绍了ZIGBEE技术的定义,特点,和组网原理。其中更是对ZIGBEE的网络节点类型、网络拓扑结构和路由方式进行了深入的研究。最后,基于ZIGBEE技术的特点和组网原理,对无线传感网络进行探索研究,组建了一个简单的无线传感网络,用以采集环境的温湿度数据以及传感器板的电压,并对结果进行了分析。     

基于分层的WSN非均匀模糊分簇路由

基于分簇拓扑的无线传感器网络中常出现的"热区"问题,文章提出一种非均匀分簇的无线传感器网络多跳路由协议,基本思路是将网络划分为宽度不等的层来构建非均匀的簇,路由算法按轮运行。结合剩余能量和密集度,利用Mamdani模糊推理进行层内的簇首选择,构建层间路由树让簇首以多跳方式与基站进行通信。仿真结果表明该算法能够有效缓解"热区"问题,延长网络存活时间。     

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。     

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。     

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。     

Messaging specifications, properties and gratifications as institutions: How messaging institutions shaped wireless service diffusion in Norway and Japan

We address the following question: why have a large number of mobile services been successful in Japan but received only lukewarm response in Norway despite Norway’s lead in the late 1990s in wireless messaging? Current explanations are not sufficient in explaining this dilemma. We approach mobile service diffusion through the lens of new institutionalism by analyzing how messaging institutions emerged both on supply and demand sides that enabled and constrained mobile service innovation. A tripartite framework of institutional fields consisting of architectural service specifications, service properties, and use gratifications is formulated. Using secondary data we show that mobile service specifications in Japan integrated better interpersonal communication and data services and thereby allowed instrumental and aesthetic properties to align with expressive properties of messaging. In Norway disjoint service specifications caused service properties and gratifications to remain disconnected, which inhibited data service adoption and channeled data service adoption towards simple SMS based messaging solutions. Differences in service specifications and prospective gratifications not only account for differences in overall service diffusion, but offer valuable insights into institutional forces that shape complex mobile service innovation.     

Quantifying price-driven wireless substitution in telephony

For the better part of a decade, a non-trivial and steadily increasing share of households in the United States has come to rely exclusively on wireless technology for their voice communications needs. Aggregate data show clearly (1) that the share of wireless-only households has risen steadily in recent years; while (2) the price of wireless service has fallen substantially relative to traditional landline service. The aggregate data are therefore consistent with the hypothesis that wireless/wireline cross-price elasticities are positive and economically significant. However, econometric corroboration of this conjecture has proven elusive in the existing empirical literature, which has relied on datasets compiled at the turn of the millennium, when wireless substitution was very limited. Partly in response to this dearth of econometric evidence, regulators and competition authorities in the US have generally been reluctant to conclude that wireless voice service represents a meaningful economic substitute for traditional wireline telephony. In the absence of reliable econometric estimates, even the sign of the relevant cross-price elasticities is an open question: The majority of US households maintain both a landline and at least one wireless connection, so it is unclear, ex ante, whether the two services are substitutes or complements. Thus, it is critical to identify consumer behavior at the margin. Using state-level panel data from a relatively recent time period (2001-2007), this study develops and estimates a demand system that permits evaluation of the own-price, cross-price, and income elasticities of demand for wireless and wireline telephony in the United States. A one percent decrease in the price of wireless service is estimated to decrease the demand for fixed-line service by approximately 1.2-1.3%, and the parameter estimates imply that the Slutsky symmetry holds for the demand system. These results substantially exceed prior econometric estimates from the existing empirical literature, and provide evidence that wireless voice service has evolved into a strong economic substitute for traditional landline service. The parameter estimates from the demand system suggest that roughly two thirds of observed landline attrition in the United States over the sample period is attributable to the observed decline in the relative price of wireless service.