A scheduling-based downlink MU-MIMO mechanism is proposed in a wireless communication system. An access point transmits a first scheduling message to a plurality of stations. The first scheduling message reserves a first transmission burst for channel sounding. The AP then transmits a sounding signal and in response receives channel state information (CSI) from the plurality of stations. Based on the CSI, the AP performs MU-MIMO encoding and applies transmit beamforming (precoding). The AP transmits a second scheduling message that reserves a second transmission burst for MU-MIMO transmission. The AP then transmits downlink data streams to multiple stations simultaneously. Finally, the AP receives uplink acknowledgements from the stations. In one embodiment, the scheduling-based MU-MIMO is implemented using PSMP scheduling technique. PSMP-based downlink MU-MIMO allows both 802.11n and 802.11ac stations to process multiple spatial streams with reduced complexity, enhanced performance, and significant power saving.