关键词: 分布式协调功能, 马尔可夫模型, 非饱和数据流, 服务质量

Abstract:

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 window 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.

Key words: distributed coordination function, Markov model, unsaturated situation, quality of service