It has been reported that there occurs unfairness between downlink and uplink in 802.11 WLAN. This is mainly caused by CSMA/CA employed in DCF. The unfairness specifically has an adverse impact on bi-directional voice calls. Downlink voice connections become a primary factor to limit voice capacity. In this paper, we propose a novel medium access protocol, so called DCFmm, in order to improve QoS of downlink voice traffic as well as fairness between bi-directional voice connections. DCFmm is designed to enhance 802.11 DCF, and is fully compatible to the legacy DCF. In addition, it only requires protocol modifications of the AP. Thus, it can be easily implemented into existing 802. 11 WLANs. DCFmm is compared with two conventional techniques through computer simulations. Extensive simulation results show that the proposed DCFmm scheme can improve fairness between downlink and uplink, and consequently, support larger number of voice calls than DCF.