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81.
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
82.
针对有线电视系统工程建设的特点,依照《招标投标法》的规定和程序,对有线电视系统工程招标的种类、招标方式、招标工程必备的条件、标底的编制及审定、开标、评标和中标的原则进行详细介绍,对招标文件的编制进行具体说明。 相似文献
83.
84.
本文重点研究基于包错误率测量的链路自适应算法,分析了包错误率与信道参数的关系,提出了一种有别于固定门限值方案的优化门限值方案。仿真结果表明,优化门限值方案的网络吞吐量要大于固定门限值方案和基于信干比估计的链路自适应算法,最大增幅可达12Mbit/s。在系统引入重传机制后,网络吞吐量将有所损失,但最大不超过1Mbit/s,相比较服务质量的提高是值得的。需指出的是,虽然分析和仿真均以HIPERLAN/2为例,但不失一般性,它们同样适合于WPAN/WLAN等类似系统。 相似文献
85.
在文献[1]的基础上,提出几个改进的模糊加权平均滤波器。本文的方案不仅同时考虑了相邻像素对中心像素的兼容性以及中心像素对相邻像素的兼容性,而且还考虑到了权系数对局部环境的适应性。实验结果表明,该方法相比文献[1]中的模糊加权平均滤波器以及标准的均值滤波器、中值滤波器在噪声消除与边缘保留方面具有更好的性能。 相似文献
86.
从图像的二维谱可以得出现行广播电视图像为什么不能满足人眼的视觉匹配以及现行电视制度的不足 ,从而对未来的高清晰度电视发展提出要求。 相似文献
87.
88.
89.
黑龙江省电子政务建设及思考 总被引:1,自引:0,他引:1
黑龙江省电子政务"王"字型广域网络结构采用MPLSVPN技术,解决了网络互联互通、允许内部IP地址重复问题,为推广网上应用系统实现信息共享奠定了良好的基础;反思了黑龙江省电子政务建设的一些做法,为兄弟省电子政务建设提供一些可借鉴的模式。 相似文献
90.
基于有限状态的全周期序列混沌映射的研究 总被引:1,自引:1,他引:0
在有限长度的数字计算机中,混沌迭代序列是一个有限周期序列,其相关性能远远低于理想序列。基于skew tent映射,提出一种离散化的有限状态混沌映射,它允许精确的数值计算,没有舍入误差,通过选择合适的参数,映射能产生全周期长度的序列。仿真实验表明,归一化的序列平均周期对计算机精度不敏感,生成的二进制序列具有良好的相关性能。 相似文献