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无线局域网(WLAN)技术的发展带来的多媒体业务流量的剧增,是无线网络的资源管理、服务质量(QoS)保障等问题日益突出,传统的媒体访问控制(MAC)协议需要重新设计才能对无线网络的QoS问题进行有效的解决。本文介绍了无限局域网QoS技术的发展,包括针对IEEE802.11MAC层协议进行的各种QoS增强技术。通过与传统的802.11标准的MAC层进行对比分析,讨论了IEEE802.11e的两个新的策略:增强的分布式协调功能和混合协调功能。通过对受控竞争机制的分析,指出了IEEE802.11e仍存在的不足及未来的发展方向。 相似文献
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无线局域网的Qos机制分析 总被引:1,自引:0,他引:1
无线局域网(WLAN)技术的发展带来的多媒体业务流量的剧增, 使无线网络的资源管理、服务质量 (Qos)保障等问题日益突出。传统的媒体访问控制(MAC)协议需要重新设计才能对无线网络的Qos问题进行有效的解决。通过与传统的802.11标准的 MAC层进行对比分析,指出了802.11e 标准对MAC层所做的改进。 相似文献
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在分析无线网协议提供QoS保证方面存在的问题的基础上,讨论了IEEE802.11e的两个新的策略:增强的分布式协调功能和混合协调功能。通过对受控竞争机制的分析.指出了IEEE802.11e仍存在的不足及未来的发展方向。 相似文献
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将于2009年年底推出正式技术规范的IEEE802.11n已成为目前业界的焦点之一。802.11n基于之前的IEEE802.11标准,增加了MIMO(多入多出)技术、在PHY层的信道绑定,以及MAC层的帧聚合,是IEEE802.11-2007无线网络技术的重要补充。原始数据速率达到了54 Mbps,最高可达600 Mbps。 相似文献
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随着无线网络的迅速发展,网络上的业务流量与日俱增,如何保证无线局城网实时业务服务质量的问题也越来越突出.文中分别介绍了IEEE802.11中的MAC层协议和802.11e标准中所采纳的改进方式,通过对比分析DCF和EDCF的性能特性,具体仿真时延和丢包率两个性能参数,指出了802.11e标准对MAC层所做的改进. 相似文献
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本文在分析无线局域网媒体接入控制(MAC)协议的基础上,提出支持时分双工(TDD)的MAC协议:EDCF-TDD。IEEE802.11增强型分布式协调功能(EDCF)只支持单工通信,即数据帧只能由发送方传送到接收方。EDCF-TDD利用IEEE802.11点协调功能(PCF)提供的数据帧格式,可以实现数据帧的双向传输。EDCF-TDD更适合传输对称的实时业务和面向连接的TCP业务,而且与IEEE802.11完全兼容。仿真结果表明:EDCF-TDD可以提高吞吐量和实现时延、时延抖动和丢组率分级;理论分析结果基本准确。 相似文献
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Qiang Ni Lamia Romdhani Thierry Turletti 《Wireless Communications and Mobile Computing》2004,4(5):547-566
Quality‐of‐service (QoS) is a key problem of today's IP networks. Many frameworks (IntServ, DiffServ, MPLS etc.) have been proposed to provide service differentiation in the Internet. At the same time, the Internet is becoming more and more heterogeneous due to the recent explosion of wireless networks. In wireless environments, bandwidth is scarce and channel conditions are time‐varying and sometimes highly lossy. Many previous research works show that what works well in a wired network cannot be directly applied in the wireless environment. Although IEEE 802.11 wireless LAN (WLAN) is the most widely used IEEE 802.11 wireless LAN (WLAN) standard today, it cannot provide QoS support for the increasing number of multimedia applications. Thus, a large number of 802.11 QoS enhancement schemes have been proposed, each one focusing on a particular mode. This paper summarizes all these schemes and presents a survey of current research activities. First, we analyze the QoS limitations of IEEE 802.11 wireless MAC layers. Then, different QoS enhancement techniques proposed for 802.11 WLAN are described and classified along with their advantages/drawbacks. Finally, the upcoming IEEE 802.11e QoS enhancement standard is introduced and studied in detail. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
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无线局域网标准IEEE 802.11是一种较低成本的无线数据传输方案。无线网状网的产生解决了无线局域网覆盖范围小的问题。IEEE Task Group S早在2004年就开始策划制定关于无线网状网多跳通信,MAC层路由转发以及安全的标准——IEEE 802.11s。介绍了IEEE 802.11s最新的草案标准,并通过试验床的设计与试验评估了当前基于IEEE 802.11s无线网状网网络的整体性能。最后探讨了视频应用在IEEE 802.11s中的可行性。 相似文献
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Dukju Ko Seungjae Han Hojung Cha Rhan Ha 《Wireless Communications and Mobile Computing》2008,8(4):407-419
To support Quality of service (QoS)‐sensitive applications like real‐time video streaming in IEEE 802.11 networks, a MAC layer extension for QoS, IEEE 802.11e, has been recently ratified as a standard. This MAC layer solution, however, addresses only the issue of prioritized access to the wireless medium and leaves such issues as QoS guarantee and admission control to the traffic control systems at the higher layers. This paper presents an IP‐layer traffic control system for IEEE 802.11 networks based on available bandwidth estimation. We build an analytical model for estimating the available bandwidth by extending an existing throughput computation model, and implement a traffic control system that provides QoS guarantees and admission control by utilizing the estimated available bandwidth information. We have conducted extensive performance evaluation of the proposed scheme via both simulations and measurements in the real test‐bed. The experiment results show that our estimation model and traffic control system work accurately and effectively in various network load conditions without IEEE 802.11e. The presence of IEEE 802.11e will allow even more efficient QoS provision, as the proposed scheme and the MAC layer QoS support will complement each other. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
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WKAN的安全性一直是市场关注的焦点。WLAN现有的安全机制包括MAC地址过滤、虚拟专网(VPN)、有线等效保密(WEP)和WEP保护接入(WPA),但这些安全机制均存在缺陷,整个行业期待新的标准802.11i能够从根本上解决WLAN的安全问题.但仍然需要市场对该标准进行验证。 相似文献
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Yang Xiao 《Wireless Communications and Mobile Computing》2006,6(4):453-466
Current IEEE 802.11 wireless local area network (WLAN) standard products can provide up to 54 Mbps raw transmission rate, while non‐standard WLAN products with 108 Mbps have already appeared in the market, and the next generation WLAN will provide much higher transmission rates. However, the medium access control (MAC) was designed for lower data rates, such as 1–2 Mbps, and it is not an efficient MAC. Furthermore, a theoretical throughput limit exists due to overhead and limitations of physical implementations, and therefore increasing transmission rate cannot help a lot. Designing efficient MAC strategies becomes critical and important. In this paper, we introduce and propose a series of efficient MAC strategies to overcome the fundamental overhead, and to improve performance. The protocols and mechanisms include Direct Link Protocol, Without Acknowledgement, Without Retransmissions, Block Acknowledgement Protocol, Concatenation, Packing, Multiple Frame Transmission (versions 1 and 2) and Piggyback. The aim of this paper is to introduce and propose these efficient new MACs not only for current IEEE 802.11 standards (.11a/.11b/.11g), but also for the next generation WLAN with higher speed and higher throughput, especially for IEEE 802.11n. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
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红外线作为室内通信无线传输媒质,具有低成本、低功耗等特点.本文描述 了IEEE 802.11红外局域网媒质访问控制协议(MAC)和红外数据协会(IrDA)提出的高级红外媒质访问控制层协议(AIr MAC);研究了两种协议性能估计模型并利用OPNET仿真工具对IEEE 802.11 MAC与高级红外AIr MAC接入性能进行了仿真验证.通过对两种MAC协议接入方式、吞吐量性能估计模型以及吞吐量性能仿真结果进行比较分析,总结了IEEE 802.11红外局域网媒质接入协议和高级红外媒质接入协议之间的不同之处. 相似文献