Shortly after the release of iOS 6, many users complained that they could not connect to their own Wi-Fi networks and that transfer speeds dropped considerably. Although iOS 6.0.1 was released, not all iDevices got rid of problems, but there are a method simple to return to normal, at least until Apple solves its problems. It's all related to the WPA/WPA2 security modules that don't get along so well with iOS 6, and that generally reduce the speed of data transfer, as they are used to secure connections to routers.
Normally these connections should be seen as a method to secure all internet traffic made through the router, and in iOS 6 it would be good to switch to the WEP protocol to be sure that you can connect to the router and the transfer speed does not decrease . The measure is temporary, probably Apple will solve its problems and everything will return to normal, but in the meantime you can solve everything using WEP. Each router has a settings menu where you can change the protocol used, I couldn't tell you where to find the settings for any router model.
