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介绍了无线局域网较蜂窝电话和有线局域网在办公、时间和费用方面的优势,以及在发展中所遇到的障碍以及未来发展的趋势。 相似文献
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展望无线技术走近无线局域网 总被引:1,自引:0,他引:1
吴南晖 《信息技术与标准化》2002,(4):4-8
无线局域网技术(包括IEEE802.11、蓝牙技术、HomeRF等)将是新世纪无线通信领域最有良好发展前景的重大技术之一,本文着重介绍了无线局域网标准的进展,IEEE802.11、蓝牙技术、HomeRF等几种主流标准的比较,分析了无线局域网技术,市场,发展与应用前景。 相似文献
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本文对无线局域网的标准--802.11做了一个总体的介绍,包括其传输媒体、三扑结构、媒体访问控制等。IEEE802.11是无线局域网的一个新标准,需要经过实践检验并在实践中逐步改进和完善。 相似文献
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RomanPolz PatrickGrabienski 《世界电子元器件》2004,(5):34-35,43
符合802.11b标准的无线局域网为市场上无线网络的发展搭建了稳定的平台。WiFi标准可保证不同厂商产品的互操作性,从而确保最终消费者投资的安全。随着与802.11b同在2.4GHz带宽上运行的更新的802.11g网络的推出,无线网络得到进一步发展。它们既能支持更高速率(最大54Mb/秒),又具有向下兼容的特性。此外,消费者也可以选择在5GHz带宽的速率上运行802.11a 相似文献
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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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基于IEEE802.11无线局域网的安全性研究 总被引:1,自引:0,他引:1
随着无线局域网的不断发展,网络安全问题日益突出。这里根据无线局域网信道的特点,首先介绍了无线局域网的安全需求,其次,描述了基于IEEE802.11无线局域网标准的有线等效保密(WEP)协议原理,并对WEP协议存在的安全漏洞及其相应的攻击进行了分析,最后,针对这些安全漏洞和攻击提出了增强无线局域网安全性的改进方案。 相似文献
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Wireless local area networks experience performance degradation in presence of small packets. The main reason for that is
the large overhead added at the physical and link layers. This paper proposes a concatenation algorithm which groups IP layer
packets prior to transmission, called PAC-IP. As a result, the overhead added at the physical and the link layers is shared
among the grouped packets. Along with performance improvement, PAC-IP enables packet-based fairness in medium access as well
as includes QoS support module handling delay-sensitive traffic demands. The performance of the proposed algorithm is evaluated
through both simulations and an experimental WLAN testbed environment covering the single-hop and the widespread infrastructure
network scenarios. Obtained results underline significant performance enhancement in different operating scenarios and channel
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Dzmitry Kliazovich received his Masters degree in Telecommunication science from Belarusian State University of Informatics and Radioelectronics
in 2002. He is currently working towards the Ph.D. degree in University of Trento, Italy. From September 2005 to February
2006 he was a visiting researcher at the Computer Science Department of the University of California at Los Angeles. He is
an author of more than 20 research papers published in international books, journals and conference proceedings. His main
research interest lies in field of wireless networking with a focus on performance optimization and cross-layer design.
Fabrizio Granelli was born in Genoa in 1972. He received the “Laurea” (M.Sc.) degree in Electronic Engineering from the University of Genoa,
Italy, in 1997, with a thesis on video coding, awarded with the TELECOM Italy prize, and the Ph.D. in Telecommunications from
the same university, in 2001. Since 2000 he is carrying on his teaching activity as Assistant Professor in Telecommunications
at the Dept. of Information and Communication Technology—University of Trento (Italy). In August 2004, he was visiting professor
at the State University of Campinas (Brasil). He is author or co-author of more than 60 papers published in international
journals, books and conferences, and he is member of the Technical Committee of the International Conference on Communications
(from 2003 to 2007) and Global Telecommunications Conference (GLOBECOM2003 and GLOBECOM2004). Dr. Granelli is guest-editor
of ACM Journal on Mobile Networks and Applications, special issues on “WLAN Optimization at the MAC and Network Levels” and
“Ultra-Wide Band for Sensor Networks”, and Co-Chair of 10th IEEE Workshop on Computer-Aided Modeling, Analysis, and Design
of Communication Links and Networks (CAMAD’04). Dr. Granelli is General Vice-Chair of the First International Conference on
Wireless Internet (WICON’05) and General Chair of the 11th IEEE Workshop on Computer-Aided Modeling, Analysis, and Design
of Communication Links and Networks (CAMAD’06). His main research activities are in the field of networking and signal processing,
with particular reference to network performance modeling, medium access control, wireless networks, cognitive radio systems,
and video transmission over packet networks. He is Senior Member of IEEE and Associate Editor of IEEE Communications Letters. 相似文献
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WLAN的出现,充分解决了有线网络先天性缺陷所带来的一系列问题。与有线网络相比,WLAN具备了很多特定优势。作为有线局域网的一种补充和扩展,WALN使计算机具有了可移动性,能快速、方便地解决有线网络不易实现的网络连通问题,成为今后网络发展的主导方向。IEEE802.11标准是IEEE制定的无线局域网标准,各厂商的产品在同一物理层上可以互相操作,这样就使得无线局域网的两种主要用途“多点接入”和“多网段互联”更易于低成本实现,从而为无线局域网的进一步普及打通了道路,文中介绍了几个常用标准的特点。 相似文献
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P. Nicopolitidis G. I. Papadimitriou A. S. Pomportsis 《International Journal of Communication Systems》2001,14(1):1-42
In this paper an overview of the wireless local area network (LAN) area is provided. The two types of wireless LAN topologies used today, infrastructure and ad hoc, are presented. The requirements that a wireless LAN is expected to meet are discussed. These requirements impact on the implementation of both the Physical and MAC layer of a wireless LAN. The unique characteristics of wireless physical layers are discussed and the five technology alternatives used today are presented. MAC layer issues are discussed and the two existing standards, IEEE 802.11 and HIPERLAN 1, are examined. Polling‐based MAC protocols (RAP, GRAP) are also reviewed. Finally, an introduction is made to wireless technologies that interact with WLANs, such as personal area networking (PAN) and wireless ATM and an overview of HIPERLAN 2, a WLAN using ATM technology, is provided. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
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一种IEEE 802.11中慢启动递减的竞争窗口控制算法 总被引:2,自引:0,他引:2
本文在研究现有的无线局域网802.11 MAC层拥塞控制的基础上,提出了一种增强的拥塞控制性能的算法,称为"慢启动递减算法"(SSDS:Slow-Start Decrease Scheme).该算法通过修改802.11的MAC层中的DCF(Distributed Coordination Function)子协议,改善了IEEE802.11无线局域网在拥塞情况下的性能,提高了网络吞吐量.文中通过仿真对算法进行了分析和研究. 相似文献
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基于WLAN技术的无线校园网组网研究 总被引:10,自引:0,他引:10
无线局域网(WLAN)使用无线多址信道方法来支持计算机间通信。简要介绍了IEEE802.11g标准协议以及无线局域网基本原理和拓扑结构,并结合无线局域网组网特点,详细阐述设计规划无线校园网的原则、方法和步骤。最后介绍一个可行的802.11g无线校园网设计方案。 相似文献
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Youngsoo Lee Minsik Lee Chong‐Ho Choi 《International Journal of Communication Systems》2013,26(7):832-852
The demand for multimedia services, such as voice over Internet Protocol, video on demand, information dissemination, and ?le sharing, is increasing explosively in wireless local area networks. These multimedia services require a certain level of QoS. Thus, it is important to provide QoS for multimedia applications. IEEE 802.11e tries to meet the QoS requirement of multimedia services by using Enhanced Distributed Channel Access. This gives more weights to high‐priority tra?c than low‐priority tra?c in accessing the wireless channel. However, Enhanced Distributed Channel Access suffers from many problems such as low aggregate throughput, high collision rates, and ineffective QoS differentiation among priority classes. In this paper, we propose a new medium access scheme, the Arbitration Interframe Space‐controlled Medium Access Control (AC‐MAC), that guarantees absolute priority in 802.11 wireless networks. In AC‐MAC, the AIFS and contention window values are controlled, so that a higher‐priority tra?c can preferentially access and effectively utilize the channel. Extensive simulations show that AC‐MAC can perfectly provide absolute priority and good throughput performance regardless of the number of contending nodes. In the simulation of voice over Internet Protocol service, AC‐MAC provides effective QoS differentiation among services and also meets the high level of QoS requirements. AC‐MAC also adapts quickly in a dynamic environment and provides good fairness among the nodes belonging to the same priority class. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
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Enhancing channel utilization by improving media access coordination in wireless local area networks
Distributed coordination function (DCF) is the basis protocol for IEEE 802.11 standard wireless local area networks. It is based on carrier sense multiple access with collision avoidance (CSMA/CA) mechanism. DCF uses backoff process to avoid collisions on the wireless channel. The main drawback with this process is that packets have to spend time in the backoff process which is an additional overhead in their transmission time. The channel is rendered idle when all the stations defer their transmissions due to their backoff process. Therefore, the channel utilization and the total throughput on the channel can be improved by reducing the average time spent by the packets in the backoff process. In this paper, we propose a new media access coordination function called proposed media access protocol (PMAP) that will improve the channel utilization for successful packet transmission and therefore, the total achievable throughput. In addition, we propose an analytical model for PMAP under saturated conditions. We use this model to analyze the performance of PMAP under saturated conditions. To substantiate the effectiveness of our model, we have verified the model by simulating PMAP in NS‐2. Simulation and analytical results show that under saturated conditions, PMAP shows profound improvement in the throughput performance compared to DCF. In addition, the throughput performance of PMAP under unsaturated conditions is presented. We have also presented the delay performance of PMAP and DCF through simulation in both saturated and unsaturated conditions. Simulation results show that the average delay experienced by the packets is less in PMAP compared to DCF. Further, the variance in the packet delay is same for both PMAP and DCF protocols under unsaturated conditions. From the performance results obtained for PMAP under both saturated and unsaturated conditions, it can be concluded that PMAP is superior in performance compared to DCF. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
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With an increasing popularity of DCF based wireless LAN, the modeling of 802.11 distributed coordination function (DCF) has attracted lots of research attention. Existing analysis of 802.11 DCF has been focused on the determination of the throughput and the packet delay under saturated traffic and ideal channel conditions. Although some recent papers address the saturated performance under a simple uniform error model, they can hardly capture the impact of bursty characteristics of wireless fading on the performance of 802.11 DCF. This paper presents exact formulae for the throughput and the delay in DCF for various traffic conditions when either saturated or unsaturated traffic load is present. A two-state Markov channel model is incorporated to present the bursty characteristics of channel errors. With our analysis, the impact of bursty channel error on unsuccessful transmission probability and the DCF performance can be determined. The results of our analytical framework reveal that the four-way handshaking scheme does not improve throughput substantially for light traffic load. However, for heavy traffic load, the four-way handshaking scheme is advantageous as compared to the basic access scheme. Also, extensive simulation is done to substantiate the accuracy of our analytical model. 相似文献