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一种最小竞争窗口自适应调整的802.11退避算法 总被引:1,自引:0,他引:1
该文在对原有的IEEE 802.11 DCF研究的基础上,提出了一种基于最小竞争窗口自适应调整的退避算法(Minimum Contention Window Self-adaptive Adjusting, MCWSA)。该算法的思想是每个站点根据网络中当前的时隙利用率和理论上最优时隙利用率进行比较,周期性动态调整自身的最小竞争窗口,以适应不同的网络拥塞状况。仿真表明,该算法提高了IEEE 802.11局域网在拥塞情况下的性能,在饱和吞吐量和时延上都有不同程度的改善。 相似文献
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在共享媒体的通信系统中,队列调度的公平性是很重要的。该文在研究了IEEE WLAN已有的各种队列调度算法的基础上,提出了一种预测式公平队列调度算法(Predict Fair Queuing,PFQ),并结合IEEE 802.11e的EDCF(Enhanced Distributed Coordination Function)机制提出一种基于PFQ的新的MAC层协议——P—EDCF(PFQ—based EDCF)。该协议通过引进PFQ算法来修改EDCF的优先级控制方式,提供一种公平、高效的接入机制。仿真结果表明,该机制很好地改善了EDCF的性能,为各种类型业务提供了公平的服务。 相似文献
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一种提高IEEE 802.11吞吐量和公平性的自适应优化算法 总被引:2,自引:0,他引:2
该文提出了一种针对IEEE 802.11 DCF网络增强其吞吐量和公平性性能的自适应优化算法,算法基于网络节点侦听信道得到的网络状态信息进行竞争发送的自适应调整以获得最优的网络性能,称之为CSCC(Channel Sensing Contention Control)算法。算法采用了对节点的信道接入请求以概率参数P_T进行过滤的方法控制节点竞争接入信道的激烈程度,其主要特点在于在优化调整过程中不需要进行计算复杂的网络节点数量估计,并且可以在不同网络状态下围绕始终确定的优化目标进行参数优化调整。仿真实验结果表明,算法能够适应不同节点数量和不同数据大小的网络进行自适应的网络优化调整,并获得了系统吞吐量、碰撞概率、延迟、延迟抖动、公平性等多方面的性能改善。 相似文献
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本文介绍并评估了几种支持IEEE 802.16标准QoS要求的包调度算法,并将它们的重要性能进行了比较. 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
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Wireless Internet Service Providers (WISPs) are expected to be the new generation of access providers using the emerging IEEE 802.11 technology. Face to the high competition of providing network services, the WISP have to offer the best service to the users. For this purpose, the WISP networks' managers need to provide Quality of Service (QoS) with a minimum cost in their wireless networks. The current link layer IEEE 802.11b provides fair sharing of the radio resource with no service differentiation mechanism; similarly to the Internet best effort service. However, the ongoing standard IEEE 802.11e should implement a priority mechanism at the link layer to differentiate the users' traffic. In order to overcome the lack of differentiated mechanism in the current link layer IEEE 802.11b, hence controlling the utilization of the scarce radio resource, we propose in this article to deploy Diffserv architecture coupled with an adaptive provisioning of QoS to provide better services to the users with minimum WISP cost and improve the utilization of the radio resource. Compliant with the current and future IEEE 802.11 link layer, the proposed adaptive QoS provisioning mechanism reacts to the radio resource fluctuation and improves the number of accepted clients in the IEEE 802.11 wireless cells based on the WISP business policies. The network layer differentiation provided by the Diffserv architecture intends to control the concurrent access of the traffic to the scarce radio resources at the IP layer of the mobile hosts for the uplink traffic on one hand, and at the IP layer of the base stations for the downlink traffic on the other hand. 相似文献
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Kenan Xu Quanhong Wang Hossam Hassanein 《International Journal of Communication Systems》2005,18(7):619-637
This paper proposes a multi‐dimensional Markov model to analyse the performance of the IEEE 802.11e EDCF MAC protocol. Based on this model, we present extensive performance evaluation in terms of throughput, throughput ratios, and access delay of flows of distinct priorities under RTS/CTS mode. We also provide quantitative analysis of the impact of prioritized parameters, i.e. Arbitration InterFrame Space (AIFS), Contention Window (CW) on Quality of Service (QoS) differentiation. The accuracy of the proposed model is verified by means of comparing the numerical results obtained from both analytical model and simulations. Our research can be used as a guideline for the prediction of how flows belonging to a certain Traffic Category (TC) perform with their TC‐specific parameters, as well as designing EDCF‐based WLANs and tuning the parameters to achieve the desirable differentiated QoS objectives. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
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一种基于IEEE 802.11的多速率自适应MAC协议 总被引:2,自引:0,他引:2
提出了一种新颖的基于连续ACK帧统计信息的IEEE 802.11多速率自适应MAC协议EARF(EnhancedARF),其主要思想是:每一个速率有各自的成功阈值——速率升高的门限值,并且该值根据信道状况(用延时因子量化)动态地变化。协议不需对现有的IEEE 802.11标准做任何修改,因此易于通过编写驱动程序实现。仿真表明在大多数信道条件下,该协议性能较现有的基于ACK帧统计的速率自适应协议如ARF,ARF3-10都有较大的提高。 相似文献
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该文提出了一种新的应用于IEEE 802.11e EDCA (Enhanced Distributed Channel Access)中提供QoS(Quality of Service)的方法。这种方法是将几个时隙组合起来构成一个超时隙,每个超时隙的开始分配给不同的业务来进行发包。时隙的分配是根据各种业务的不同优先级来实现的。这种方法可以保证高优先级业务具有较大的吞吐量,较少的MAC延时和较低的丢包率。与802.11e EDCA草案中提出的不同冲突窗口大小的方法相比,这种方法具有可以提高吞吐量,降低丢包率,并能减小站点数目变化对高优先级业务吞吐量的影响等优点。这种新的提供QoS的方法优于不同冲突窗口大小的方法,在IEEE 802.11e EDCA中应用超时隙方法可以大大提高EDCA的性能。 相似文献
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基于IEEE802.11b无线局域网支持QoS的盲检测算法 总被引:1,自引:0,他引:1
这里提出了一种基于IEEE802.11b无线局域网(WLANs)的MAC层的终端盲检测算法.和以往的算法相比,该算法通过对连接接入点AP(Access Point)的所有活动终端进行盲检测,可以非常有效的增加每个AP点所支持的语音通信终端数量,从而增加了信道的带宽,提高语音服务质量QoS.而且算法只执行在接入点的点协调功能上(PCF),因此不需要对当前的IEEE802.11MAC层的协议做任何修改.仿真结果表明了本算法对WLANs语音服务质量的有效支持. 相似文献
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Hännikäinen Marko Lavikko Tommi Kukkala Petri Hämäläinen Timo D. 《Telecommunication Systems》2003,23(3-4):297-333
Quality of Service (QoS) support has generally been lacking from WPAN and WLAN technologies, which has motivated the research
of TUTWLAN. Design objectives have been relatively simple network architecture and capability to support real time services
ranging from sensor data to multimedia streaming. The main TUTWLAN entities for QoS support are the Medium Access Control
(MAC) protocol called TUTMAC and TUTWLAN Access Point (AP). The channel access is based on dynamic reservation Time Division
Multiple Access (TDMA). TUTWLAN is shown to be suitable for wireless home and office applications. It provides flexibility,
interoperability and availability of services exceeding the recent QoS proposals that has been accounted at the standardisation
bodies for standard wireless technologies.
This revised version was published online in September 2006 with corrections to the Cover Date. 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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With relatively high transmission capacity and usually unconstrained connections, IEEE802.11 WLANs provide the ideal infrastructure for pervasive video content sharing and communications. However, the delivery of high-performance video streams over 802.11 WLANs remains a challenging task due to the inherent characteristics of compressed video and dynamic channels. In this paper, we present a brief survey of various recent innovations that have been developed to enhance the Quality of Service (QoS) performance for video over WLANs. Based on the application scenarios, the solutions have focused mainly on three network layers, that is, Application layer (APP), Media Access Control layer (MAC), and Physical layer (PHY). After reviewing the video compression technology, we first examine various single-layer solutions for video over WLANs. We then discuss several cross-layer solutions that take advantage of mutual interactions between different network layers. Finally, several technical issues beyond QoS performance, including energy and security, are also addressed. We conclude that the application of video over WLANs will continue to increase in future. 相似文献