Abstract
This paper first described the IEEE 802.11 MAC layer access control mechanism, that is, the DCF access control mechanism, analysis the basic DCF back-off algorithm BEB. Next, we study a variety of improved BEB algorithms, and then we proposed ZDCF back-off algorithm which is an exponential-based half back-off algorithm. ZDCF is flexible, easy to implement and has excellent performance as BEB algorithms when there is small scale of nodes, while at same time avoiding the shortcomings of BEB algorithm when there is large scale of nodes.