This may be of interest to others although may only be relevant to some routers. My UK BT router has two Wifi frequencies 2.4 and 5 GHz and the odd occasion I have Iooked at the router info, on the router itself, I noticed that it always seemed to use 2.4 GHz. Out of curiosity I investigated it last night and found that iPads and iPhones generally do not seem to like the same SSID used for both frequencies. (The SSID is the name of the network, i.e. the name under Settings, Wifi, Choose a Network...) I changed the 5GHz SSID on the router and up came both frequencies on the network list and so now I am connected at the higher frequency.