Last Post: October 5, 2006:
Concerning power management bits:
11.2.1 Power management in an infrastructure network: "STAs changing Power Management mode shall inform the AP of this fact using the Power Management bits within the Frame Control field of transmitted frames. The AP shall not arbitrarily transmit MSDUs to STAs operating in a PS mode, but shall buffer MSDUs and only transmit them at designated times."
220.127.116.11 "To change Power Management modes, a STA shall inform the AP through a successful frame exchange initiated by the STA. The Power Management bit in the Frame Control field of the frame sent by the STA in this exchange indicates the Power Management mode that the STA shall adopt upon successful completion of the entire frame exchange. The Power Management bit shall not be set in any management frame, except an Action frame."
All frames have a two octet frame control field. All frame control fields have a power management subfield bit. That bit, in some but not all frame types/subtypes, is a communication channel between transmitter and receiver concerning the future power management status of the transmitter after a successful completion of the frame exchange sequence of the moment.
Only non-AP stations, either infrastructure or independent, have any business setting this bit to 1 to signal an upcoming power save state. If IBSS then broadcast data exchanges might signal power save.
I am at a loss whether control frames as well as data frames are marked. My guess is only data frames but a protocol analyzer can answer that one.
I hope this helps. Thanks. /criss