基于效用最大化的IEEE 802.11 DCF性能分析及改进
doi: 10.3724/SP.J.1146.2007.00922
Maximum Utility Based Performance Analysis and Improvement of the IEEE 802.11 DCF
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摘要: 针对802.11 DCF在系统负载较大时不能有效利用带宽资源的缺点，该文提出一种基于效用函数的DCF优化机制(U-DCF)。通过设置站点吞吐量的对数效用函数，将带宽资源的有效利用问题建模为系统效用最大化问题；应用最优化理论将此系统问题等效为可分布式求解的用户问题，即各站点只须独立选择最大化其净效用的竞争参数(CWmin)，则系统整体效用也获得最大化。仿真结果表明：与标准DCF相比，U-DCF通过预估系统的当前平均分组长度和竞争站点数来调整竞争参数CWmin，能够显著提高系统的饱和吞吐量，减小分组发送时延和丢帧率。
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关键词:
- 无线局域网 /
- 媒体访问控制 /
- IEEE 802.11 DCF /
- 效用函数
Abstract: An enhanced DCF scheme, called U-DCF, based on logarithm utility function is proposed in this paper, since bandwidth resource can not be utilized efficiently in the chosen backoff parameters of 802.11 DCF. The users utility is a function of his data throughput, thus the bandwidth resource utilization problem is modeled as a utility based constrained maximization problem, called a system problem. A user problem formulation of the system problem is derived by using Lagrange relaxation and duality theory, thus the competing stations only need to choose their optimal channel access strategies (CWmin) independently to maximize their net utility. Then the maximum aggregate utilities can be achieved in a distributed way. Simulation results show that, by adjusting the backoff parameter CWmin to the average frame-length and the number of the competing stations on the channel, U-DCF outperforms the original DCF in terms of system throughputs, delay bound and frame-loss-rate. -
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