Wifi: About U-APSD
UAPSD is an acronym for Unscheduled Automatic Power Save Delivery, a feature of Wi-Fi devices that allows them to save power.
UAPSD is also known as WMM power save.
For AP Mode, AP will buffer its frame to a STA in PS mode until a trigger frame is received from STA.
On receiving the trigger frame, AP will flush the buffered frame immediately.
Trigger frame is expected to be QoS Data or QoS NULL frame, with Pwr Mgmt bit in frame control field set or cleared.
if(PwrMgmt == 1){
if(AP already in PowerSave mode) discard.
else AP enter PowerSave mode.
}else{
if(AP in PS mode) trigger,exit PS mode, AP to flush data to the STA.
else discard.
}