This work aims to utilize capture effect to improve system throughput under a fair transmission environment for the IEEE 802.11 WLANs. In practice,when there is an access collision,the access point (AP) can still decode the corresponding data successfully if the received signal to interference plus noise ratio (SINR) is larger than a threshold. This phenomenon is called capture effect. To improve the system throughput,this work proposes a power control algorithm to take the advantage of capture effect. However,the proposed power control scheme cannot provide a fair transmission environment even though the system throughput increases. Therefore,this work also presents a method to adaptively adjust the transmission probability of each station in the contention window (CW) for fair transmission. In addition,this work adopts the non-orthogonal multiple access (NOMA) technique to further improve system throughput. The simulation results show that the proposed schemes can not only improve system throughput significantly,but also provide a fairer transmission environment.