U-APSD (Unscheduled Automatic Power Save Delivery)

U-APSD is a part of 802.11e and helps considerably in increasing the battery life of VoWLAN terminals. U-APSD must be supported both by the VoWLAN terminal and by the WLAN access point. U-APSD always only works for the WMM access category concerned, so it is important that the requirements listed in the chapter above are met.

The VoWLAN terminal logs in with Class of Service Expedited Forwarding (EF) and U-APSD at the WLAN access point.
The VoWLAN terminal then switches to power-save mode.
If the WLAN access point is sent data packets for the VoWLAN terminal concerned with the Class of Service Expedited Forwarding (EF), the access point temporarily stores this data for a short time and waits until the VoWLAN terminal is woken up again. Only then is the data sent.
The procedure works so rapidly that, even in the call status, the terminal still has enough time for the power-save mode.

Apart from the longer battery life, U-APSD has another positive effect. With longer phone calls, VoWLAN terminals with functioning U-APSD are far cooler than devices that do not support U-APSD.

U-APSD is supported by the access points (bintec W2003ac-ext™, bintec WI1003n™) upwards of relay 10.1.609.