A probability-based algorithm to adjust contention window in IEEE 802.11 DCF

The paper proposes a new probability-based algorithm to adjust the contention window in 802.11 DCF (distributed coordination function). Our main motivation is based on the observation that 802.11 DCF decreases the contention window to the initial value after each successful transmission, which essentially assumes that each successful transmission is an indication that the system is under low traffic loading. PDCF (probability-based DCF) takes a more conservative measure by halving the contention window size with a probability f after each successful transmission. This decrease behavior lowers the collision probability, especially when the competing node number is large. We compute the optimal value for f, and the numerical results from both analysis and simulation demonstrate that PDCF significantly improve the performance of 802.11 DCF, including throughput, fairness, and energy efficiency. In addition, PDCF is flexible for supporting priority access by selecting different values of f for different traffic types; it is fully compatible with the original 802.11 DCF, and simple to implement, as it does not require changes in control message structure and access procedures in DCF.