What are the benefits and drawbacks of WiFi power saving modes (PSM and U-APSD)?

1 PSM: Power Save Mode

Power Save Mode (PSM) is the basic power saving mode for WiFi devices that comply with the 802.11 standard. In PSM, the device enters a low-power state when it has no data to send or receive, and wakes up periodically to check for incoming packets. The device informs the access point (AP) that it is in PSM by sending a Power Save Poll (PSP) frame, and the AP buffers the packets destined for the device until it receives a PSP frame. PSM can save a significant amount of energy, especially for devices that have low or intermittent traffic, but it also introduces some drawbacks, such as increased latency, packet loss, and network congestion.

2 U-APSD: Unscheduled Automatic Power Save Delivery

Unscheduled Automatic Power Save Delivery (U-APSD) is an enhanced power saving mode for WiFi devices that support the 802.11e standard, which defines quality of service (QoS) features for wireless multimedia applications. In U-APSD, the device can trigger the delivery of buffered packets from the AP without sending a PSP frame, by using a QoS Data or QoS Null frame. The device can also specify how many packets it wants to receive in each delivery cycle, by using a Service Period (SP) parameter. U-APSD can improve the efficiency and responsiveness of the wireless network, especially for applications that require low latency and high throughput, such as voice over IP (VoIP) or video streaming. However, U-APSD also has some limitations, such as increased complexity, compatibility issues, and overhead.

3 How to enable PSM and U-APSD

The availability and configuration of PSM and U-APSD depend on the type and model of your device, the operating system and driver version, and the network settings. Generally, you can enable or disable PSM and U-APSD from the device's wireless adapter properties, or from the advanced settings of the WiFi network. Some devices may also have a power management switch or button that allows you to toggle between different power saving modes. You should check the user manual or the manufacturer's website for specific instructions on how to enable PSM and U-APSD on your device.

4 How to optimize PSM and U-APSD

Finding the optimal settings for PSM and U-APSD depends on several factors, such as the type and frequency of wireless traffic, the distance and interference between your device and the AP, and the battery capacity and usage of your device. There is no single solution for power saving modes, so you may need to experiment to find the best balance between energy efficiency and network performance. To optimize PSM and U-APSD, choose PSM for devices with low or sporadic traffic such as email or web browsing, and U-APSD for devices with high or continuous traffic like VoIP or video streaming. Adjust the wake-up interval or SP parameter according to your traffic pattern and latency requirements. A shorter interval or larger SP can reduce delay and packet loss but also increase power consumption and network overhead. Use a compatible AP that supports PSM and U-APSD, configuring it to match your device settings. Some APs may have a power saving mode option or QoS mode option that you can enable or disable. Avoid using multiple power saving modes simultaneously, as this may cause conflicts or inefficiencies - for example, do not use PSM and U-APSD at the same time, or do not use PSM or U-APSD along with other power management features like Bluetooth or WiMAX.

6 Here’s what else to consider

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