一种改进IEEE 802.11 DCF的建模与分析

Modeling and Analysis of Improved IEEE 802.11 DCF

针对IEEE 802.11系列标准中分布式协调功能(DCF)的缺点,提出了一种简单有效的改进DCF算法.其主要的改进集中在2方面:在经典DCF的基础上,将第0级退避的退避窗口值加倍;使用选择概率p将第0级退避窗口分割成2部分.为了精确地反映改进后协议的性能,建立了二维马尔可夫模型,并将其与经典DCF比较.数值仿真结果表明,改进后的DCF协议在终端节点密度较大时,其吞吐量和时延等性能参数要比经典的DCF优越.

In view of shortcomings of distributed coordination function （DCF） in IEEE 802. 11 series standard, a simple but effective improved DCF mechanism was proposed. Main improvements are focuing on the size of backoff window and it＇s probability was chosen in 0 backoff stage ： doubling the backoff win- dow size of 0 backoff stage based on original mechanism and using probability p to divide the window size of 0 backoff stage into two parts. For purpose of reflecting the performance accurately, a comprehensive analytic model was constructed. We compare it with the classical DCF scheme and numerical simulation. It is shown that the new DCF mechanism has better performs than that of classical DCF in the case of dense terminal and heavy offered load.