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1.
Quality of service (QoS) support for multimedia services in the IEEE 802.11 wireless LAN is an important issue for such WLANs
to become a viable wireless access to the Internet. In this paper, we endeavor to propose a practical scheme to achieve this
goal without changing the channel access mechanism. To this end, a novel call admission and rate control (CARC) scheme is
proposed. The key idea of this scheme is to regulate the arriving traffic of the WLAN such that the network can work at an
optimal point. We first show that the channel busyness ratio is a good indicator of the network status in the sense that it
is easy to obtain and can accurately and timely represent channel utilization. Then we propose two algorithms based on the
channel busyness ratio. The call admission control algorithm is used to regulate the admission of real-time or streaming traffic
and the rate control algorithm to control the transmission rate of best effort traffic. As a result, the real-time or streaming
traffic is supported with statistical QoS guarantees and the best effort traffic can fully utilize the residual channel capacity
left by the real-time and streaming traffic. In addition, the rate control algorithm itself provides a solution that could
be used above the media access mechanism to approach the maximal theoretical channel utilization. A comprehensive simulation
study in ns-2 has verified the performance of our proposed CARC scheme, showing that the original 802.11 DCF protocol can
statically support strict QoS requirements, such as those required by voice over IP or streaming video, and at the same time,
achieve a high channel utilization.
Hongqiang Zhai received the B.E. and M.E. degrees in electrical engineering from Tsinghua University, Beijing, China, in July 1999 and January
2002 respectively. He worked as a research intern in Bell Labs Research China from June 2001 to December 2001, and in Microsoft
Research Asia from January 2002 to July 2002. Currently he is pursuing the PhD degree in the Department of Electrical and
Computer Engineering, University of Florida. He is a student member of IEEE.
Xiang Chen received the B.E. and M.E. degrees in electrical engineering from Shanghai Jiao Tong University, Shanghai, China, in 1997
and 2000, respectively, and the Ph.D. degree in electrical and computer engineering from the University of Florida, Gainesville,
in 2005. He is currently a Senior Research Engineer at Motorola Labs, Arlington Heights, IL. His research interests include
resource management, medium access control, and quality of service (QoS) in wireless networks. He is a Member of Tau Beta
Pi and a student member of IEEE.
Yuguang Fang received a Ph.D degree in Systems and Control Engineering from Case Western Reserve University in January 1994, and a Ph.D
degree in Electrical Engineering from Boston University in May 1997.
From June 1997 to July 1998, he was a Visiting Assistant Professor in Department of Electrical Engineering at the University
of Texas at Dallas. From July 1998 to May 2000, he was an Assistant Professor in the Department of Electrical and Computer
Engineering at New Jersey Institute of Technology. In May 2000, he joined the Department of Electrical and Computer Engineering
at University of Florida where he got the early promotion with tenure in August 2003 and has been an Associate Professor since
then. He has published over one hundred (100) papers in refereed professional journals and conferences. He received the National
Science Foundation Faculty Early Career Award in 2001 and the Office of Naval Research Young Investigator Award in 2002.
He is currently serving as an Editor for many journals including IEEE Transactions on Communications, IEEE Transactions on
Wireless Communications, IEEE Transactions on Mobile Computing, and ACM Wireless Networks. He is also actively participating
in conference organization such as the Program Vice-Chair for IEEE INFOCOM’2005, Program Co-Chair for the Global Internet
and Next Generation Networks Symposium in IEEE Globecom’2004 and the Program Vice Chair for 2000 IEEE Wireless Communications
and Networking Conference (WCNC’2000). 相似文献
2.
介绍了柳钢2800mm中板轧机液压自动厚度控制(HAGC0系统工艺参数与系统的结构、特点和功能。系统还包括平面形状控制、动态规程自动和控制轧制技术,构成一个较完善的控制系统。 相似文献
3.
中厚板轧制边部不均匀变形机理的探讨 总被引:1,自引:0,他引:1
通过分析宽中厚板轧制过程中的边部不均匀变形,探讨了其影响因素及大宽度板“切边纵裂”的产生原因,提出了解决问题的具体办法。 相似文献
4.
5.
6.
针对中小型企业销售管理的现状,利用J2EE架构技术设计了面向中小型企业的销售管理信息系统,该系统具有良好的跨平台性和可移植性,并且经过测试运行,达到了预期的效果。 相似文献
7.
夏季住宅空调能耗已成为目前广州地区电力过荷的一个主要原因,而目前建筑师对住宅设计中的空调能耗因素并未有深入的考虑。本文就广州地区中高层住宅标准层平面设计中的朝向、形状、大小及层高与空调能耗关系进行了相关的分析,适用于夏热冬暖地区。 相似文献
8.
This investigation proposes a fixed collision rate (FCR) back-off algorithm for wireless networks. The proposed scheme takes advantage of the central unit (CU) in a wireless network to broadcast a common back-off window size to all the users, significantly alleviating the unfairness of bandwidth utilization in conventional binary exponential back-off (BEB) algorithms. It is shown that, when maximum throughput is achieved, collision rate is almost a constant for any traffic load. In the operation of the FCR, the CU dynamically adjusts the back-off window size to keep the collision rate at a constant level for maximum throughput. Simulation results demonstrate that the unfairness of bandwidth utilization in the BEB is significantly lessened and the throughput can be maintained at e-1≈0.368 when the number of users approaches infinity. The capture effect even further improves system performance. 相似文献
9.
本文介绍了南钢中板厂将系统工程最优化技术中的随机服务系统理论和可靠性设计方法引入到电气设备的维护和管理工作中,并结合现场实际情况摸索出一套电气设备可靠性保障方法。 相似文献
10.