WMM APSD setting is basically a power saving mechanism implemented in the wifi standards. In this basic guide, we will explain a little bit in every day terms on how WMM APSD works, and whether you should enable or disable this option.

Please note that this basic guide is written in very simple terms that describe the process. We will not go into the technical details or graphs about how it works or how much battery that you can actually save with the WMM APSD function.

What does WMM APSD mean

WMM APSD stands for Wi-Fi Multimedia (WMM) Automatic Power Save Delivery. It is basically a feature mode that allows your mobile devices to save more battery while connected to your wifi network. By allowing your mobile devices to enter standby or sleep mode, it conserves battery. The APSD allows smooth transition in and out of sleep mode by allowing the mobile devices to signal the router of its status.

How does WMM APSD save battery power

Similar to how beacon interval and DTIM period works together to conserve your device’s power usage. Whenever your mobile devices’ wireless adapter enters into power saving mode or “sleep” mode, your router or access point can buffer data and hold it for your mobile devices with the WMM APSD function.

There are two types of APSD that goes under this type of battery power saving feature.
U-APSD (Unscheduled Automatic Power Save Delivery): Your client devices signal the router to transmit any buffered data.

S-APSD (scheduled Automatic Power Save Delivery), the Access Point will send buffered data based on a predetermined schedule known to the power-saving device without any signal from the station device.

When to WMM APSD Enable or Disable

Enable WMM APSD: when you use your Wifi for any real time applications such as VoIP. Your mobile devices such as windows phone, iphone, or ipad can benefit from the WMM APSD router option as well. The battery consumption benefit can range from 10~30% compared to when you disable this option.

Disable WMM APSD: When your phone or mobile devices do not play well with the specific router that you have. There are reported cases of mobile devices dropping connections when the WMM APSD options are turned on.

The reason for this is that the mobile devices cannot retrieve the data from router after being awaken from the sleep state. Usually in this case, you can either turn the WMM APSD power saving option off from your router or on the mobile devices. Alternatively, you should see if you can check to see if the router company has released a new firmware that solves the problem. The best way is to actually experiment and troubleshoot for the problem.

Keep this option on unless you have issues. If you do not use your wireless router for any mobile devices, you probably will not benefit from enabling the WMM APSD option. However, there is no real disadvantage to keeping this on, so we would simply recommend to keep the configuration setting as enabled.

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