I guess you may need different external port and internal port configuration? mine is TL-R480T+ V5 that supports this function. if you can not find this, i think it may not support this feature.

try latest firmware; try binfile. I also get the following method from the website Step 1: Plug the 3G modem to your computer. Step 2: (On Windows XP) clickStart->go to All...

ad speed with an ethernet cable connected? and how many computers are there connected to the router? you can try to move the computer a little closer to the wireless router. and you can also change...

Deibidy, uninstall the antivirus on your computer and try to install the driver again. If the driver has some problem, you can download a new one from the website...

you can try to upgrade the latest firmware http://www.tp-link.com/en/support/download/?model=TL-MR3220

it may be the incompatibility issue. Go to Network -> 3G, and change the Connection Mode to Connect Manually