In IEEE 802.11 DCF, performance unfairness inevitably occurs between downlink (AP-to-station) and uplink (station-to-AP) directions. The asymmetry of the DCF operation degrades downlink traffic severely. Therefore, it is important to enhance downlink QoS by alleviating link congestion. In this paper, we propose a novel medium access control scheme, B-DCF (Burst DCF), to enhance the legacy DCF. It is designed to provide a level of QoS differentiation with downlink traffic, and can improve downlink multimedia QoS in a cell. QoS differentiation is realized using burst transmission control. B-DCF is fully backward compatible to the legacy DCF, and can friendly operate with normal DCF stations. B-DCF is evaluated and compared to DCF and EDCA schemes. For heavy BE (best effort) loads, the proposed B-DCF scheme can support larger number of conversational voice calls while achieving larger BE throughput.