Fedora Networking :: Mobile Broadband Dongle Restarts Itself?

I few days ago I bought a mobile broadband, with dongle model Huawei e1820. I have no problem connecting to the internet. The settings in network manager are correct. But when I use the modem with high traffic for a while, like streaming, the speed gets slower and slower until finally the modem shuts down and restarts itself. After the modem restarts, it connects to the internet again, but now the speed is terrible. And if i continue using high traffic it will restart itself in a matter of minutes. But if I plug it out and don't use it for a while, the speed is back to "acceptable". For a while...

I'm using fedora 15, and have also tried it on Ubuntu Natty with the same result. Reinstalled usb_modeswitch. configured usb_modeswitch with all the guides on the web. No results.