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无线局域网(WLAN)是对目前无线接入系统的补充,可以使网络用户摆脱网线的束缚,实现真正意义上的移动互联。与蜂窝系统相比,它的户外移动性虽然受到限制,但适用面广,可在典型的应用环境如办公室、家庭、展览厅、机场、火车站等热点地区,向终端用户提供高速数据传输。WLA 相似文献
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无线局域网(WLAN)是数据通信与计算机网络的新技术,近年来发展迅速。关于无线局域网的802.11协议,经过几年的酝酿,其草案已经完成,最终文本将于1996年公布。 在我国,随着经济的发展,对数据信息通信的要求越来越高;随着各种便携式计算机和数据处理终端的大量使用,对方便、 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
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IEEE802.11无线局域网标准 总被引:1,自引:0,他引:1
介绍了IEEE802.11无线局域网技术规范.给出了ISM频段、扩频技术的背景及各国相应的标准、规范.描述了允许可证2.4GHzISM频段的直接序列扩频技术及IEEE802.11协议规范。 相似文献
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由于无线局域网所具有的优势,它不仅将在广电系统的办公自动化和智能化中发挥积极的作用,而且也将可能在视音频数据的传输中得到应用。本文详细介绍了无线局域网概念,相关标准内容、所涉及的协议,组网方式以及相关传输技术。 相似文献
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由于无线局域网所具有的优势,它不仅将在广电系统的办公自动化和智能化中发挥积极的作用,而且也将可能在视音频数据的传输中得到应用。本详细介绍了无线局域网概念、相关标准内容、所涉及的协议、组网方式以及相关传输技术。 相似文献
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阐述了直接序列扩频技术对IEEE802.11无线局域网协议的解决方案,介绍了支持802.11协议的全数 字化直接序列扩频处理芯片,分析了目前无线网络中采用的MBOK、CCK多进制正交码扩频调制方式及性能。 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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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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IEEE 802.11e enhanced distributed channel access (EDCA) is a distributed medium access scheme based on carrier sense multiple access with collision avoidance (CSMA/CA) protocol. In this paper, a model-based admission control (MBAC) scheme that performs real-timely at medium access control (MAC) layer is proposed for the decision of accepting or rejecting requests for adding traffic streams to an IEEE 802.11e EDCA wireless local area network (WLAN). The admission control strategy is implemented in access point (AP), which employs collision probability and access delay measures from active flows to estimate throughput and packet delay of each traffic class by the proposed unsaturation analytical model. Simulation results prove accuracy of the proposed analytical model and effectiveness of MBAC scheme. 相似文献
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IEEE 802.11ah is an approved amendment to IEEE 802.11 wireless local area network (WLAN) standard to support growing demand for machine‐to‐machine (M2M) applications. To enable an efficient scheme for accessing the channel by a large number of stations (STAs) within the coverage of an access point, 802.11ah has developed a novel mechanism known as Restrictred Access Window (RAW). Here, a group of STAs attempts channel access during their designated RAW slot by following the carrier sense multiple access‐collission avoidance (CSMA‐CA)‐based enhanced distributed channel access (EDCA) mechanism. In this paper, we develop an analytical model for finding the nonsaturation/saturation throughput of 802.11ah WLAN under the RAW‐based channel access mechanism. We describe an analytical model for finding the average frame delay as well. The impact of the number of STAs and number of groups on network throughput and average delay are presented. We establish that the RAW mechanism can improve the throughput while the average frame delay gets reduced. The analytical results are validated by extensive simulation studies. 相似文献
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对无线网络流量的分析和准确预测是无线网络管理与安全领域的重要研究内容之一,在网络规划、网络监控、流量趋势分析、网络优化以及入侵检测和异常检测等方面发挥着重要作用。介绍了目前典型的无线网络流量分析的模型与常用流量分析方法,综述了传统无线通信网络(如无线局域网和物联网)中的流量分析技术,指出了流量分析技术应用于无线自组网系统的可能性与面临的几点挑战,以及无线自组网系统与流量分析技术结合的发展方向。 相似文献
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Security protocol for IEEE 802.11 wireless local area network 总被引:1,自引:0,他引:1
As Wireless Local Area Networks (WLANs) are rapidly deployed to expand the field of wireless products, the provision of authentication and privacy of the information transfer will be mandatory. These functions need to take into account the inherent limitations of the WLAN medium such as limited bandwidth, noisy wireless channel and limited computational power. Moreover, some of the IEEE 802.11 WLAN characteristics such as the use of a point coordinator and the polling based Point Coordination Function (PCF) have also to be considered in this design. In this paper, we introduce a security protocol for the IEEE 802.11 PCF that provides privacy and authentication, and is designed to reduce security overheads while taking into account the WLAN characteristics. We prove this protocol using the original and modified BAN logic. 相似文献
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With the boom of wireless devices, the number of wireless users under wireless local area networks (WLANs) has increased dramatically. However, the standard backoff mechanism in IEEE 802.11 adopts fixed initial contention window (CW) size without considering changes of network load, which leads to a high collision probability and low channel utilization in bursty arrivals. In this paper, a novel CW dynamic adjustment scheme is proposed to achieve high throughput performance in dense user environment. In the proposed scheme, the initial CW size is dynamically adjusted to optimum according to the measured packet collision probability. Simulation results show that the proposed scheme can significantly improve the throughput performance. 相似文献
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Jianhua He Zuoyin Tang Hsiao‐Hwa Chen Shu Wang 《International Journal of Communication Systems》2012,25(7):821-831
Link adaptation (LA) plays an important role in adapting an IEEE 802.11 network to wireless link conditions and maximizing its capacity. However, there is a lack of theoretic analysis of IEEE 802.11 LA algorithms. In this article, we propose a Markov chain model for an 802.11 LA algorithm (ONOE algorithm), aiming to identify the problems and finding the space of improvement for LA algorithms. We systematically model the impacts of frame corruption and collision on IEEE 802.11 network performance. The proposed analytic model was verified by computer simulations. With the analytic model, it can be observed that ONOE algorithm performance is highly dependent on the initial bit rate and parameter configurations. The algorithm may perform badly even under light channel congestion, and thus, ONOE algorithm parameters should be configured carefully to ensure a satisfactory system performance. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献