Wireless Modem Reboots

[Mark Gajdosik]

Hi multi-techies,

I have programmed OCG to reboot its wireless modem every 4 hours. I do this by terminating PPPD, issuing AT#ENHRST and waiting for 2 minutes before re-launching PPPD.

It works, but what if I don’t use PPP connection, e.g. I am connecting to the internet via ETH and have PPP as a fall-back? Is in such cases, are modem reboots necessary?

I know that the mobile network providers don’t like devices which are constantly registered/connected, but does this apply when modem is not in use? I don’t want to get our SIM card barred and when the PPP fall-back is needed, OCG won’t connect.

Thank you in advance.

[Lonny Knudson]

I don’t think it matters much if you are using the cellular service as a primary or secondary network link. In general, I wouldn’t recommend rebooting the wireless modem unless there is real problem detected (no AT command response, unable to obtain cellular service for an extended period of time, etc…). What was the reason for implementing an automated radio reboot every 4 hours?

[Mark Gajdosik]

Lonny: In 2011, when the project using wireless modems started (we used a different product back then), we had devices configured never to reboot their modems.

The first site in London (using Vodafone UK network) went offline after 3 weeks of consistent connection. They [Vodafone] told us that the device in London hasn’t re-registered on the network for some time and that it was blocked because of that.

They advised us to let our devices reconnect to the network every now and then, which we figured, should be a wireless modem reboot.

I spoke to Campbell Elder in Reading regarding this and he confirmed that the network providers don’t like consistently connected devices.

[Lonny Knudson]

Hi Mark,
So the automated reset is to circumvent ‘fixed terminal’ detection algorithm? If re-registration is the event that prevents your SIM from being barred, then you will need to manage this even if you aren’t using the cellular modem as the primary network link (the cellular radio maintains registration even when not actively used for a data link). You can force the cellular modem to re-register with a reset or by issuing AT+COPS=2, then AT+COPS=0.
If you are in contact with Campbell, I would recommend following his advice regarding this issue, I know he has worked on projects where the cellular carrier has implemented ‘fixed terminal detection’ in the past (I’m in the US and carriers don’t seem to do this here).

[Mark Gajdosik]

Lonny: Thank you. We are happy with the reboot procedure. The first MTCDP device we have on the network has been doing this every 4 hours since early autumn 2013, without issues.

I will consider using AT+COPS – thanks for the idea. Sounds lighter than AT#ENHRST and it should do what we need it to do. AT#ENHRST will be kept for, like you said, cases of a long-term disconnection.

If we were, however, to use the Ethernet as primary connection, is it still reasonable to re-register with the network even if it’s not in use, but it has SIM in it?

I need that modem to take over in case Ethernet fails. The whole project is about getting most out of MTCDPs, making them as maintenance free as possible.

[Lonny Knudson]

Hi Mark,
As I understand the issue, periodic re-registration will prevent the SIM from being barred. This will need to be done as long as a SIM is installed and the cellular radio is powered up.

[Mark Gajdosik]

Thanks Lonny, that answers my question.

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