EG912 - Network Registration

IoT Modules LTE Standard Module
1

Hi

I am using a EG912UGL modem in a GPS tracker transmitting data in real time, and I ma having some issues.

In some situations the modem loses network connectivity and takes a very long time to recover (+10min), the product is being used in Airplanes (Experimental airplanes) that are travelling at speeds greater than 180Kmh and altitudes around 300m to 1km above terrain.

The time it takes to recover is very variable, and most of the times i understand the “cause” since the airplane may be flying in more remote areas that don’t have a very good 4G coverage. But even so, the time sometimes seems too long since most of times I am able to talk with the pilot via WhatsApp with the phone registered in 4G Network.

The SIM Card is operating in roaming, but it has agreements with all 3 operators available here.

The long recover time seems to derive from the modem not being able to detect any operator and then having a BackOff / Timeout / Retry period that seems to be very long. Is there any way to force a new network search?

Or if possible, a description of the retry/backoff algorithm and timeout values?

I have been doing some tests and it seems that sending AT+COPS=0 could be a solution, but this has the problem that reverts the scan mode back to Automatic (Independent of what was configured in +QCFG: “nwscanmode”``) and I don’t want to risk registering in a 2G Network since in most cases causes “noise” issues in the Airplane radio headsets.
I have tried to send AT+COPS=0,,,7 but the modem answer with +CME ERROR: parameters are invalid, so this command doesn’t seem to be a valid solution.

Would sending AT+CFUN=4 followed by AT+CFUN=1 trigger a new network search?

Other suggestions are welcome…

Another issue is that the modem sometimes loses connectivity in places where there should be no problem (with the airplane very close to ground (50m~100m) and close to the runway, the first symptom is that the CSQ value drops from values > 25 to 0 and after a while the registration status changes to +CREG: 0,0, normally it recovers quickly between 30s and 60s. The drops of CSQ to 0 happen with more frequency but not always the registration status changes back to +CREG: 0,0. Is there any setting that could help with this?

Thank You

2

hi,Artur;
According to your description, your product is mainly used in high-altitude environments. Generally, the signal at high altitudes is unstable. However, the modem can automatically search the network when the signal meets the basic access case.You can also try cfun0 or cfun4, but it’s difficult to determine at which time points to execute or trigger

3

Hi

Is there any way to know if the modem is currently searching for network or if it is in a Backoff period?

In some other modems, i notice that the answer to +CREG changes to +CREG: 0,2 to indicate the modem is currently searching for network, but in this Quectel modem it seems that behaviour does not exits since it changes from 0:0to 0,5 immediately (polling once a second).

Thank You