USB mobile broadband dongle randomly disconnects

Question

This is really driving me mad. I had to get a USB dongle for my net connection because I couldn't afford a wired net connection, and after spending hours on the phone trying to get the tech support people to tell me what details I could enter into NetworkManager so I could use it as they don't publish a non-proprietary-software guide on their site, I finally managed to get it to work.
Asides from the connection being crap (I live in a small country town so even ordinary mobile phones get < 3 bars), I've found that the device disconnects for no apparent reason, like it just shuts down. NetworkManager can't reboot it, unplugging it and plugging it in again doesn't fix it, and it seems the only solution is to reboot my computer (just like Windows huh). I've read somewhere that Huawei devices are supposed to be flipped to their modem state for them to work properly, but I'm not entirely sure how to do this, and don't really want to risk borking the device as it's the only net connection I've got for the time being.
Where should I look to find debug information from the device and how to stop it from disabling itself after several hours? And are the usb_modeswitch and similar programs safe, i.e. are they likely to work as expected without totally messing up the device?

Answer 1

I hope you have solved this problem by now but just in case here is my experience:-
I have had this problem with on 2 different linux and windows machines. In my case it turned out to be a mechanical problem.  The USB sockets are very unreliable and for some reason particularly so with USB mobile broadband dongles.  In the first case the machine had front usb ports.  When the dongle was plugged into the front ports the connection was very unreliable and when plugged directly to the motherboard ports at the rear there was no problem.
In the second case I was using a long usb cable as the signal strength at the PC was too weak for broadband connection. In this case the connection to the usb socket at the end of the cable was very loose so the internet connection would dropout for no apparent reason and as with your experience I would have to reboot to get it going again. This was an expensive usb cable too, so price was no guide to reliability.