Symptoms
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.
Cause
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.
Workaround
To work around this issue, use one of the following methods, as appropriate for your situation.
Method 1: Connect the mobile PC to a power source
When you plug the mobile PC into a power source, Windows switches the wireless network adapter power setting in the default power plan from the Medium Power Saving setting to the Maximum Performance setting. This turns off the 802.11 power save mode.
Method 2: Modify the default power saving power plan
Modify the default on-battery power setting for the wireless network adapter. Configure the wireless network adapter to use the Maximum Performance setting when Windows is configured to use the Balanced power plan or the Power saver power plan. To do this, follow these steps:
-
Click Start
-
Click Change plan settings under the power plan that is selected. For example, if the Balanced option is selected, click Change plan settings under Balanced.
-
Click Change advanced power settings.
-
In the Power Options dialog box, expand Wireless Adapter Settings, and then expand Power Saving Mode.
-
In the list that appears next to On battery, click Maximum Performance, and then click OK.
-
Open Power Options by swiping in from the right edge of the screen, tapping Search (or if you're using a mouse, pointing to the upper-right corner of the screen, moving the mouse pointer down, and then clicking Search), entering Power options in the search box, and tapping or clicking Power options.
-
Tap or click Change plan settings under the power plan that is selected. For example, if the Balanced option is selected, tap or click Change plan settings under Balanced.
-
Tap or click Change advanced power settings.
-
In the Power Options dialog box, expand Wireless Adapter Settings, and then expand Power Saving Mode.
-
In the list that appears next to On battery, tap or click the current setting and select Maximum Performance, and then OK.
Method 3: Use the "High performance" power planIf the computer is running on a power plan other than the High performance power plan when you connect to a wireless network, manually change the power plan to High performance. To do this, follow these steps:
-
Click Start
Note You can also right-click the battery icon in the notification area to access the Power Options command. -
Click High performance.
-
Open Power Options by swiping in from the right edge of the screen, tapping Search (or if you're using a mouse, pointing to the upper-right corner of the screen, moving the mouse pointer down, and then clicking Search), entering Power options in the search box, and tapping or clicking Power options.
Note You can also right-click the battery icon in the notification area to access the Power Options command. -
Tap or click High performance.
Method 4 (for advanced users): If "Wireless Power Setting" can't be customized in the User Interface as described in Method 3, here is how to implement the same change using the PowerCfg command
Windows 8 or 8.1
The workaround documented for Windows 8.1 is to change the Balanced power plan, Wireless Adapter Settings power saving mode for "On battery" to "Maximum performance". This has the same effect as the following command, when issued from an Admin command prompt:
powercfg -setdcvalueindex 381b4222-f694-41f0-9685-ff5bb260df2e 19cbb8fa-5279-450e-9fac-8a3d5fedd0c1 12bbebe6-58d6-4636-95bb-3217ef867c1a 0
It is possible that the system may not be using the Balanced power mode The following steps should be followed to make thsi change:
1. Run "powercfg /l" to find a list of power plans, and confirm that "Balanced" is the default. For example:
powercfg /l
Existing Power Schemes (* Active)
----------------------------------
Power Scheme GUID: 381b4222-f694-41f0-9685-ff5bb260df2e (Balanced) *
Power Scheme GUID: 8c5e7fda-e8bf-4a96-9a85-a6e23a8c635c (High performance)
Power Scheme GUID: a1841308-3541-4fab-bc81-f71556f20b4a (Power saver)
2. Then, set the DC Power Saving Mode to "Maximum Performance" for the Wireless Adapter by running the following command:
powercfg -setdcvalueindex 381b4222-f694-41f0-9685-ff5bb260df2e 19cbb8fa-5279-450e-9fac-8a3d5fedd0c1 12bbebe6-58d6-4636-95bb-3217ef867c1a0
where:
-setdcvalueindex [...] 0 - sets the "Current DC Power Setting Index" to "0", where 0 = Maximum Performance
381b4222-f694-41f0-9685-ff5bb260df2e - is the Balanced power plan. If your system is not using the Balanced power plan, change this value to the "* Active" plan you're using
19cbb8fa-5279-450e-9fac-8a3d5fedd0c1 - Wireless Adapter Settings
12bbebe6-58d6-4636-95bb-3217ef867c1a - Power Saving Mode
More Information
If you choose to modify the default On battery power saving setting by setting it to Maximum Performance, this change affects the Balanced power saving mode and the running time of the computer when it runs on battery power. This change reduces the battery time by between approximately two percent and nine percent running time.
Note This change may not be reflected in original equipment manufacturer (OEM) versions of Windows that may be installed on mobile PCs. Computer manufacturers may change the default Windows power settings according to their guidelines.
You may also experience this issue when you connect to a Wi-Fi hot spot by using a Microsoft Windows XP-based computer. This issue is less likely to occur in Windows XP because the default power saving mode in Windows XP does not turn on the 802.11 power save mode of the wireless network adapter. However, if you do experience this issue in Windows XP, you can modify the power saving settings of the wireless network adapter to work around this issue. To do this, follow these steps:
-
Click Start, click Run, type ncpa.cpl, and then click OK.
-
In the Network Connections dialog box, right-click the wireless network adapter, and then click Properties.
-
Click Configure under the name of the network card.
-
Click the Advanced tab, and then modify the power management settings. For example, click Power Management in the Property list, drag the Value slider to the power management setting that you want to use, and then click OK.
Note These settings may differ depending on the manufacturer of the wireless network adapter.
For help with power consumption and battery life problems in Windows Vista, visit the following Microsoft Web page:
Fix problems in which power consumption is more than expected or the battery life is short
