You can't join the domain before the logon screen. You need to logon to the PC using a local account, then join it to the domain.
Or are you talking about it already being on the domain but the network connection does not start untill after you logon? If you logon locally and check the wireless connection, is it working like it should? If you do a logoff then and logon to the domain account, does it work? Does it only not work right after turning the computer on?