no emulator currently works with WFC.
Anybody else telling you that it works doesn't really understand what they are saying.
So far no way has been found to reliably emulate Nintendo WFC. I did some reading on the developers forums, which is swamped with idiots asking how to play online using an emulator, when it says in every thread that it's currently not possible, that the emulators are banned from nintendo's servers. Furthermore all videos on youtube showing apparent "b/w wifi battles" are 100% fake, otherwise you would be able to do it, which you are not.
If you want to play pokemon white / black on wifi you need to get a DSi and a Flashcart. Because that works just fine.