GSM modem operator connection lost

[estan]

Hi,

An other thing what i notice is that i lose on a regular base the connection with the GSM operator. The only thing i can do is reset the modem by sending the command AT+CFUN=1 because on all the rest it respond with an error.

Anyone had similar problems? Anyone can give me a hint how to verify this?

My GSM modem is a Fargo Maestro 100 Lite.

Thanks in advance.

[Hack]

Is the connection open for a long period of time with no activity?

[estan]

Well, actually there is activity, not so much but enough to get at least 1 activity every 6 hours. I receive sms messages and calls on that gsm modem. When i receive a call i send the command ATH and i reply by sending a sms message to the number (when CLIP is available).
What i see is that it does not respond correctly on some test commands that i send every 5 minutes to the GSM modem.
AT&T0 Response expected = OK
AT+CREG? Response expected = +CREG: 0,1 and an OK

The modem start to respond ERROR on both commands, when i try to call the gsm modem it does not respond (the operator cannot find the number) and messages of course does not arrive on the gsm modem.

When i restart the service, the gsm modem is still locked up, giving me rubbish and fails to connect due the internal testing. So i need to go to hyper terminal and send AT+CFUN=1 to reset the software stack and than restart the service to bring it back online.

I can understand that this happens one time, like a network glitch, but it start to be more regular. The reception is ok.

Besides the fact that this can happen, is there a proper way to detect this? And what could be the proper way to respond on this problem?

[Hack]

If the time between transaction activities is reaching 6 hours, then that might be why you are losing connections. With no activity, it could be disconnecting itself.

[estan]

no activity means, that you are not receiving any SMS or phone call? or no activity at all to the GSM modem? The last is certainly not, i developed an application that is monitoring the GSM modem connection by sending every 5 minutes some AT commands.

I found the following AT+WIND=xxx. This is a specific Maestro command to get unsolicited feedback from the modem, i set it to 255. the response from the modem if something happens is like +WIND: x with x a number that correspond to an event/action/situation. I hope that it can inform me what is going on when the connection is lost. Than it should send out the signal +WIND: 8 : The network is lost.

[Danny]

I think it's the former: not receiving calls or text messages. This dropout is deliberate, and it's meant to release some of the pressure on the network by disconnecting idle peers. You can prevent it by sending nonsense filler text messages every few minutes and see what happens.

[estan]

After further investigation, the modem have enough activity to stay alive. It is indeed sending out the +WIND signals when it is losing the connection with. I think that the modem itself is broken. It is also losing some of its setting during the operation, while the others don't have this problem.

[Hack]

Let us know if all you had to do to fix the problem was swap out the modem.

It is not unlikely that someone else could run into this same issue.

[estan]

another attachment to the story...

In the weekend, my system reported a Network Connection Lost (+WIND: 8)
Even after 6 hours, the modem could not regain network connection, and i didn't see any try either. I wonder if this is normal for a GSM modem. But that small devil popping up on my right shoulder says otherwise.

So, because i am fed up running to an internet connection so I remotely can re-establishing the network connection, I've implemented a respond on every time I receive +WIND: 8. I send the AT+CFUN=1 command and I wait 60 seconds before I send the configuration AT commands. That is another issue I have with this modem. It is not keeping the settings, even when I saved them by sending the command AT&W. Well yeah, we changed the modem to another location, another COM port and another SIM. The up coming days will bring us an answer packed as a late Christmas present.

I keep the forum informed.