A method of setup a protection mechanism for scheduled transmissions to multiple stations is introduced. Through transmitting a control frame addressing to multiple stations for immediate simultaneous responses, the transmitter would know the stations that are ready for receiving the scheduled data frames and schedule the packet for those stations. Combining the transmission of the control frame with the power saving mechanism would allow triggering a group of power saving stations to wake up at same for receiving the control frame and scheduled user data frames. A new mechanism of simultaneous group responses to the control frame with orthogonal identifier information for individual station is provided to uniquely identify the responding stations.