T410 + LMDE: WWAN connection automatically disconnects

[Ormu]

I have some problems with the WWAN card (Gobi 2000) of my T410 running Linux Mint Debian. It seems to disconnect the network connection without any good reason. It may happen even when the connection is not idle. This doesn't usually happen on Windows. I have noticed this with WLAN as well but it isn't very common.

I have disabled "Send PPP echo packets" in the network manager but it seems that it didn't help. There are two settings for data compression (Allow Deflate & Allow BSD data compression) and they're enabled. Could these cause problems?

Could this be caused by power management? Is there a way to disable all power saving features of all network interfaces? In my opinion, an active network connection should never be subjected to power saving of any kind.

Another cause might be a firmware bug. I'm using the newest generic/default UMTS firmware. On Windows the card is configured to use Vodafone firmware but I haven't tested it on Linux (yet). However, the Vodafone firmware seems to behave a bit differently when choosing between "2G" (GPRS/EDGE) and "3G" (UMTS/HSPA) and for some reason I haven't been able to use the AT commands to configure the card since the last firmware/Windows driver update. (It prefers "2G" which I don't like.)