In recent years, Wireless Local Area Networks (WLANs) are becoming more and more popular. The IEEE 802.11 protocol is one of the most widely deployed wireless access technologies. In order to minimize the collision probability due to multiple simultaneous transmissions, all stations compete for the wireless channel with a contention resolution method, namely the Binary Exponential Back off (BEB). In the BEB scheme, the contention window (CW) is doubled every time a station experiences transmission collision and decreases to its minimum value after a successful transmission. However, the performance degradation will be resulted from the aggressive reduction in the CW size. Accordingly, Exponential Increase Exponential Decrease (EIED) is proposed to suggest a slower reduction in a back off period after a successful transmission. Actually, the variation of CW causes unsteady system performance. In this paper, we proposed an Oneself Adjusts Back off (OAB) mechanism to improve system performance over contention-based Distributed Coordination Function (DCF) WLANs. In the OAB, the variation of CW state will be kept based on the number of the consecutive collision or successful transmission. The numerical results show that the OAB mechanism provides a better system throughput and collision rate than the related back off schemes.
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