Unable to register to LTE network

IoT Modules LTE Standard Module
1

I am having issue registering some SIM cards to the LTE network on EC21-E and EG21-G. Sim cards from a different telco have no issues. For the telco that has issues, some of the SIM cards work but most can’t. Those that can’t register to LTE network will fall back to 2G network. When these SIM cards are used on a Android phone, there are able to register to LTE network.

Wondering how to troubleshoot this type of issues? Both EC21-E and EG21-G supports the LTE band used by the telco.

The firmware for EC21-E is EC21EFAR06A04M4G and EG21-G is EG21GGBR07A11M1G.

Are they the latest version ?

Thanks in advance.

2

Have you changed the APN to suit the different telco?

For most telcos, their specific APN must be configured on the modem for LTE network registration to be successful.

This restriction does not apply to 2G or to 3G, because they both support circuit-switched connections. LTE does not.

3

I have configured the APN using AT+CGDCONT. The module has already registered itself to 2G network.

I request the module to select the LTE network using

AT+COPS=1,1,“xxxxx”,7

+CME ERROR: 30

but it returned error

Tried again to select 2G network

AT+COPS=1,1,“xxxxx”,0

+CME ERROR: 30

and it also gave same error

But if I use

AT+COPS=4,1,“xxxx”,7

OK

And it registered itself to 2G network again,

This particular SIM is a MVNO sim.

4

Please try: AT+COPS=0,,,7

5

Registration denied even after a long wait.

AT+COPS=0,,,7

OK
AT+CREG?

+CREG: 0,3

OK

Specifying AT+COPS without access technology register itself to 2G

AT+COPS=0

OK
AT+CREG?

+CREG: 0,3

OK

AT+CREG?

+CREG: 0,1

OK

AT+COPS?

+COPS: 0,0,“xxxxxxxx”,0

6

Does the AT+CGDCONT? command now show the same APN as you set?

7

Yes. AT+CGDCONT gave the required APN. Same also for “IPV4V6”

AT+CGDCONT?

+CGDCONT: 1,“IP”,“xxxx”,“0.0.0.0”,0,0,0,0
+CGDCONT: 2,“IP”,“xxxx”,“0.0.0.0”,0,0,0,0
+CGDCONT: 3,“IP”,“xxxx”,“0.0.0.0”,0,0,0,0

OK

8

I think we need Quectel to tell you if there is a firmware upgrade available.

I have run out of ideas.

9

Thanks. Appreciate your help.