I recently bought the prepaid UMTS stick from Tschibo as a backup and mostly for mobility. After unpacking it I discovered it's the Huawei E160 which is generally the same as the E220. It just comes with an additionally USB cable and a micro SD-card reader - which causes just trouble: You will need USB_ModeSwitch to change the device from card reader mode to modem. Otherwise you will have a cdrom - no don't ask.
Asking Google about linux and UMTS will lead to lots of wiki and forum entries, but most of them had one thing in common for me: They usually don't work.
Next suggestion is using NetworkManager whis utilizes a server/client concept with fancy applets that can't find my stick - out of question.
The harder way is to use wvdial directly - let's go for it. The tricky part is the config and the right/order of the AT strings. After reading some non-working examples I came up with a solution that works:
1 [Dialer Defaults] 2 Phone = *99# 3 Username = o2 4 Password = o2 5 Stupid Mode = 1 6 Carrier Check = no 7 Dial Command = ATDT 8 Modem = /dev/ttyUSB0 9 Baud = 460800 10 Init2 = ATZ 11 Init3 = ATQ0 V1 E1 S0=0 &C1 &D2 +FCLASS=0 12 ISDN = 0 13 Modem Type = Analog Modem 14 Init5 = AT+CGDCONT=1,"IP","webmobil1";
If you don't use the Tschibo stick you will probably change in the Init5 line the webmobil1 to something your ISP uses. Also phone needs sometimes to be changed to
Additionally if your card still wants a PIN add this to your config:
1 Init1 = AT+CPIN=YOUR_PIN
Finally just fire up wvdial and it should work!