Wireless medium reservation for simultaneous transmission of multiple downlink spatial streams to multiple receiver wireless stations during a multi-user transmit opportunity over a wireless medium, is provided. Such a reservation includes reserving a transmission period for simultaneously transmitting data from a transmitting station to multiple intended receiving stations on multiple downlink spatial streams over a wireless communication medium. Reserving the transmission period includes transmitting a request-to-send (RTS) frame to the multiple receiving stations, the RTS frame including a receiver address (RA) field comprising compressed addresses for the multiple receiving stations.