You may experience random connectivity issues when you connect a Windows-based mobile PC to certain Wi-Fi "hot spots." These connectivity issues include the following:
- The wireless network connection is dropped.
- You experience poor performance.
You experience these issues if the computer is running on battery power.
Note You may also experience these issues when you connect a Windows-based mobile PC to a wireless access point (AP) in a small office/home office (SOHO) environment or in an enterprise environment.
This issue occurs if the Wi-Fi hot spot uses wireless APs or routers that do not support the 802.11 power save protocol.
This issue occurs because of the power saving features that are included in Windows. The default power plan that Windows uses for a mobile PC is the Balanced power plan. The following is true for mobile PCs that are configured to use the Balanced power plan:
- When the mobile PC is plugged into a power source, the wireless network adapter is configured to use Maximum Performance mode. This turns off 802.11 power save mode.
- When the mobile PC is running on battery power, the wireless network adapter is configured to use Medium Power Saving mode. This uses the 802.11 power save mode.
When an 802.11 wireless network adapter that is set to use power save mode wants to enter a sleep state, the adapter indicates this intention to the wireless AP. The adapter does this by setting the power save option in its packets or in the 802.11 frames that it sends to the wireless AP. In this scenario, the following behavior should occur:
- When the wireless AP receives the frames that have the power save option set, the wireless AP determines that the client network adapter that sent the frames wants to enter a power saving state.
- The wireless AP then buffers packets that are destined for the client network adapter.
- When the radio of the client network adapter turns on, the client network adapter then communicates with the AP to retrieve the buffered packets.
This behavior enables the wireless network adapter to use less power and to wake up periodically at the correct time to receive network traffic from the AP.
If the wireless AP does not support this feature correctly, the wireless AP continues to send packets to the client network adapter even if the client network adapter radio is turned off. Therefore, these packets are lost. In this scenario, the symptoms that you experience may vary depending on the phase of the wireless connection in which these packets are lost.