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71.
无线局域网的快速发展已经成为近年来最惹人关注的通信产品,本文主要介绍了无线局域网的网络结构,技术特点和工作原理,并针对采用SIM卡的上网方式进行了全面较深入的讨论。 相似文献
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Zoran Hadzi-Velkov Boris Spasenovski 《International Journal of Wireless Information Networks》2002,9(3):191-199
In this paper, we estimated the influence of capture effect over the capacity of IEEE 802.11b DCF within a single picocell. The channel utilization is examined analytically by introducing two capture models based on Rayleigh-distributed envelopes of the captured and the interfering frames divided into two local-mean power classes. Simulations in a pure Rician-faded channel depict the conditions under which both Rayleigh-faded capture models can be used to accurately predict the peak network capacity. Unlike the RTS/CTS handshake access mode, Basic access mode is significantly sensitive to the capture ratio, i.e., the receiver design. The packet size threshold over which it is convenient to switch from Basic to RTS/CTS handshake access scheme is also sensitive to the capture effect. 相似文献
75.
日前无线网络的安全防护已经逐渐被提上议程,本文首先阐述了传统安全技术,随后重点论述802.11i标准及其相关理论--802.1x认证机制。802.11i标准引入了802.1x认证机制实现身份验证及密钥管理等功能。文章详细描述了802.1x认证机制的实现过程和802.11i标准的安全防护措施,为无线网络安全的各个方面提出了完整的标准措施。 相似文献
76.
史创明 《数字社区&智能家居》2005,(29)
无线局域网(WLAN)技术的发展使人们摆脱了传统线缆的束缚,可以更加方便、灵活、快捷地访问网络资源。但空间的开放性使无线局域网的安全受到来自外部入侵的威胁,安全方案已经成为无线网络发展的瓶颈。本文讨论了无线网络发展过程中的几种主要的安全方案,重点研究802.11i标准中采用的核心的加密方案WPA。 相似文献
77.
作为个人通信的一个重要组成部分,无线局域网已经掀起移动计算的新浪潮。无线技术在传榆速率、安全性方面不断改进,它不仅是有线网络的无线延伸,也可以作为LAN的无线替代。通过分析3种不同的IEEE802.11扩展标准的调制方式、工作频段等,突出说明了IEEE802.llg标准的优越性。根据医疗领域的特殊性,在基于IEEE802.11g基础上,初步构建了一个可扩展的无线医疗网络。 相似文献
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One of the challenges that must be overcome to realize the practical benefits of ad hoc networks is quality of service (QoS).
However, the IEEE 802.11 standard, which undeniably is the most widespread wireless technology of choice for WLANs and ad
hoc networks, does not address this issue. In order to support applications with QoS requirements, the upcoming IEEE 802.11e
standard enhances the original IEEE 802.11 MAC protocol by introducing a new coordination function which has both contention-based
and contention-free medium access methods. In this paper, we consider the contention-based medium access method, the EDCA,
and propose an extension to it such that it can be used to provide QoS guarantees in WLANs operating in ad hoc mode. Our solution
is fully distributed, uses admission control to regulate the usage of resources and gives stations with high-priority traffic
streams an opportunity to reserve time for collision-free access to the medium. 相似文献
80.
Richard Van Nee V. K. Jones Geert Awater Allert Van Zelst James Gardner Greg Steele 《Wireless Personal Communications》2006,37(3-4):445-453
An overview is given of the new IEEE 802.11n standard. This is the first wireless LAN standard based on MIMO-OFDM, a technique pioneered by Airgo Networks to give a significant performance increase in both range and rate relative to conventional wireless LAN. Performance results show that net user throughputs over 100 Mbps are achievable, which is about four times larger than the maximum achievable throughput using IEEE 802.11a/g. For the same throughput, MIMO-OFDM achieves a range that is about 3 times larger than non-MIMO systems. This significant improvement in range-rate performance makes MIMO-OFDM the ideal solution not only for wireless LAN, but also for home entertainment networks and 4G networks.
Richard van Nee received the M.Sc. degree in Electrical Engineering from Twente University in Enschede, the Netherlands, in 1990. In May 1995, he received the PhD degree from Delft University of Technology. From 1995 to 2000, he worked for Lucent Technologies Bell Labs on wireless LAN transmission techniques. He was one of the original proposers of the CCK and OFDM modulation techniques which were adopted by the IEEE 802.11b and IEEE802.11a wireless LAN standards. In 2001, he cofounded Airgo Networks that developed the first MIMO-OFDM modem for wireless LAN and which techniques form the basis of the IEEE 802.11n standard. Together with Ramjee Prasad, he wrote a book on OFDM, entitled ‘OFDM for Mobile Multimedia Communications.’ In 2002 he received the Dutch Veder award for his contributions to standardization of wireless communications. 相似文献