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Monday, December 31, 2012

Fixing WiFi limited connectivity in Surface RT

I thought that it may be useful to summarize some of the changes that have helped to some users to fix this issue. In my case I did not apply the registry changes because I have an AP with dual band 2.4 and 5GHz and both bands identified with different SSID and I'm forcing Surface to connect to 5Ghz.

In Metro, swipe your finger from the bottom of the screen up, select from the bar All Apps, locate the Command Prompt application, select it by dragging down the icon, select from the bar Run as Administrator, OK the warning message, the system will switch to Desktop mode. In the command prompt type the following commands:

  • netsh int tcp set heuristics disabled
  • netsh int tcp set global autotuninglevel=disabled
  • netsh int tcp set global rss=enabled

At this point reboot your Surface RT. After reboot proceed with this commands:

  • netsh interface ipv4 set address "Wi-Fi" dhcp (if this gave you an error check the name of your connection, it may not be "Wi-Fi")
  • ipconfig /renew

If you still have problems apply the following registry changes:

Open Desktop -> Search -> regedit
Open regedit. Select menu Edit -> Find...
Enter "AutoUse40Mhz" -> do search.

There are 2 such entries in registry. We need to change one, located under

   "HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\" branch.

  - Set "AutoUse40Mhz" to "0" (it has value "1" by default)(This limits the channel bandwidth to use 20MHz, this reduce the speed and it's the recommended setting when you are experiencing issues with  n connectivity)

  -  Set "Band" to "4" (it has value "6" by default)(for what I understand this change may force some devices to  connect g)(I would recommend to apply the first registry change, reboot and see what happens before applying this other change).

Reboot the Surface. Some users believe that these registry changes will make the Surface to connect using the g connection instead of n. That's not the case. Your Surface still be connected using the n protocol but using a slower bandwidth.

To achieve maximum output, a pure 802.11n 5 GHz network is recommended. If you have a 5GHz AP these registry changes should not be needed at all. To know what ratio are you using check the connection status to find the connection speed. If your speed is greater than 130Mbps, its 802.11N otherwise not. Some standard values for 802.11N are 150Mbps & 300Mbps. In my case, its 802.11g as speed is 54Mbps.

In your AP, WMM is required to be on for any Wi-Fi Alliance Certified N product. By default WMM is already on but many users disable it which may prevent N rates or lower throughput.

Useful links: