I'm using a huawei 3G modem under linux. After using NetworkManager for some time, I now use wvdial to talk to the modem and start pppd: i added a udev rule so wvdial starts automatically when the usb device is plugged in.
- The good case: i plug the modem in, wvdial fails a few time while the modem is registering, then succeeds.
- The bad case: same but wvdial keeps failing with "NO CARRIER", forever.
Only thing to do when 2) happens: unplug device, replug and hope we fall on the good case this time ...
Tried many things, like switching between gprs/umts, manually switching operator to force it to re-register ... no luck. Once it doesn't work it stays that way.
Few days ago i even came across a case where umts fails all the time, but gprs succeeds reasonably well. Now what's interesting is under windows umts just worked right away, so this is definitely a linux issue.
The modem is a huawei E1762.
NetworkManager / modem-manager somewhat suffers from same issue.
Running ubuntu lucid