How does WMM-Power Save work?

To benefit from WMM-Admission Control functionality, both the AP and client device need to be Wi-Fi CERTIFIED WMM-Admission Control. Any Wi-Fi CERTIFIED client devices in a WMM-Admission Control network that do not support WMM-Admission Control will operate as usual in WMM mode, but won’t use the access categories for which admission control is mandated by the AP.

WMM-Admission Control certification is required for the Voice-Enterprise certification program.

On a Wi-Fi network with a dense Wi-Fi deployment designed to support heavy traffic loads, such as an enterprise campus, hospital or educational campus, WMM-Admission Control helps ensure that the network can support good quality voice calls before admitting the voice call traffic stream, and assigns it priority over other traffic, such as downloads, email, and other best effort traffic.

WMM-Admission Control used IEEE 802.11 management frames for the signaling between the AP and the client device.  The AP evaluates the request frame from the client device against the network load and channel conditions.  If the AP can accommodate the request, it accepts the request and grants the client the medium time for the traffic stream.  If the request is rejected, the client device is not allowed to initiate the requested traffic stream, and may decide to either delay the traffic stream, associate with a different AP, or establish a best-effort traffic stream outside the operation of WMM-Admission Control.

WMM-Power Save is a more finely tuned power save mechanism which draws on a variety of tools to manage power consumption. In legacy power save, the driver decided when to transmit data, while in WMM-Power Save, the application makes the determination about when to transfer data. This enables customization of the power mechanism to the particular application (e.g., Voice over Wi-Fi, video gaming, etc.). WMM-Power Save is backwards-compatible with legacy power save.

WMM shortens the time between transmitting packets for higher priority traffic.

The power conservation achieved depends on the particular application in use, as well as how effectively the application uses WMM-Power Save. The Wi-Fi Alliance has produced a white paper which offers guidance to application developers.

Wi-Fi Multimedia, represented by the acronym WMM, is related to Wi-Fi CERTIFIED WMM^® programs. These optional certifications provide multimedia enhancements for Wi-Fi networks that improve the user experience for audio, video, and voice applications.

Compatibility and quality are achieved through testing of Wi-Fi products. Consumers should always look for the Wi-Fi CERTIFIED logo to ensure the best user experience possible.

If implemented correctly, WMM-Power Save will activate automatically when a Wi-Fi CERTIFIED™ for WMM-Power Save client device is communicating with a Wi-Fi CERTIFIED™ for WMM-Power Save access point. There is no action needed from a user.

Wi-Fi Alliance defined WMM as a profile of the IEEE 802.11e Quality of Service (QoS) extensions for 802.11 networks and started a certification program for WMM to satisfy the most urgent needs of the industry for a QoS solution for Wi-Fi networks. WMM provides prioritized media access and is based on the Enhanced Distributed Channel Access (EDCA) method.

As of July 1, 2020, all new Wi-Fi CERTIFIED devices require WPA3. The only way to be sure that a product meets the latest security standards is to purchase only Wi-Fi CERTIFIED products.

WMM-Power Save uses mechanisms from the IEEE 802.11e standard.

Without Quality of Service (QoS), all applications running on different devices have equal opportunity to transmit data frames. That works well for data traffic from applications such as web browsers, file transfers, or email, but it is inadequate for multimedia applications. Voice over Internet Protocol (VoIP), video streaming, and interactive gaming are highly sensitive to latency increases and throughput reductions, and require QoS. WMM defines four access categories (voice, video, best effort, and background) that are used to prioritize traffic to provide enhanced multimedia support.

Wi-Fi Alliance estimates that WMM-Power Save can provide from 15 to 40% improvement in battery life depending on the application characteristics.