Just so we are clear, this is for internet access from two networks, when one slows down the other picks up the pace?
Every solution ive managed to find so far is explaining things as being able to connect to two networks however every solution ends up being about turning your wifi card into two networks to share files or internet. I had a few issues with my wireless card but turns out the driver pre installed on my laptop which i bought new a few weeks ago, is actually for a totally different wireless card. Managed to set up a virtual wifi miniport but for all intensive purposes this is the same as setting up a ad hoc network for internet or file sharing.
The main reason for this is when i leave my laptop downloading overnight, occasionaly my wifi hotspot drops and i end up with an entire wasted night, along with occasional drops in speed, id like to have my second network connected as a fallback if one drops out (will also come in handy to prevent my minecraft server from dropping suddenly also)
I took a look at the multihoming solution but that doesnt seem to be what im looking for, mainly because its explaining it as two separate interfaces instead one wireless card and the only virtualwifi tutorials seem to be just doing what i said previously, setting up a ad hoc network basically