Optimizing the IEEE 802.11b Performance using Slow Congestion Window Decrease

Jerome Galtier

France Telecom et Mascotte


We investigate a new process for the decrease of the IEEE 802.11b Contention Window (CW) called CW decrease, introduced by Ni et al. We give some mathematical analysis of the model that explains the experimental results previously obtained. The analysis allows us to re ne the MAC optimization and reach the optimal asymptotical saturation throughput when the number of stations increases. We also investigate other parameters such as the average waiting time, that lead us to introduce another variant of the CW decrease that we call additive - as opposed to the multiplicative original scheme. We provide some experimental results based upon simulation to validate our analysis. Surprisingly our global goodput rate in the basic mode is kept from 7.4 Mbit/s with 5 stations to more than 7.3 Mbit/s with 100 stations, overperforming by 40% the original basic scheme and by 8% the scheme with the RTS/CTS enhancement.

[Jerome Galtier]
[France Telecom]