Force Module to LTE NB-IoT

[Thalhammer]

Hi,

I currently try to get the module to connect to a NB-IoT Network. I have a simcard that should support NB-IoT and configured any AT command I could find to force it to LTE and yet it connects to GSM. I now have a state that in my understanding should not even be possible and yet it is:

AT+CNMP?;+CFUN?;+CREG?;+CMNB?;+COPS?;+CPSI?
+CNMP: 38
+CFUN: 1
+CREG: 2,5,"E2D1","22DE",0
+CMNB: 2
+COPS: 0,2,"26203",0
+CPSI: GSM,Online,262-03,0xe2d1,8926,754 DCS 1800,-88,0,18-18
OK

Shouldn't CNMP=38 and CMNB=2 force the module to ignore GSM networks and only connect to LTE NB-IoT ?

I am pretty sure the card supports NB-IoT because if I do a AT+COPS=? I get the following:

AT+COPS=?
+COPS: (2,"o2 - de","o2 - de","26203",0),(1,"262 01","262 01","26201",0),(1,"262 02","262 02","26202",0),(1,"262 01","262 01","26201",9),(1,"262 02","262 02","26202",9),,(0,1,2,3,4),(0,1,2)
OK

The last two are NB-IoT networks and the module detects them as status 1 so it should be able to connect to them. I also tried

AT+COPS=1,2,"26202",9

But it just hangs until I press enter a second time and then reconnects to the same GSM Network it had before.

What am I doing wrong ?

EDIT: After reset this is what it outputs. Somehow it switches back to GSM only mode. Is it possible my setting of CNMP gets ignored ?

AT+CNMP?;+CFUN?;+CREG?;+CMNB?;+COPS?;+CPSI?
+CNMP: 13
+CFUN: 1
+CREG: 0,5
+CMNB: 2
+COPS: 0,0,"o2 - de",0
+CPSI: GSM,Online,262-03,0xe2d1,28926,676 DCS 1800,-91,0,15-15
OK

[botletics]

What firmware version do you have? It's possible that if you had an older version, the AT+CNMP command is being reset. YOu could also try checking "AT+CNMP?" after it reverts back to GSM.

[VeselaHouba]

I don't mean to hijack this issue, but my issue might be related. I have the regular SIM which should support LTE speeds (provider calls it 4G and I haven't found any real technology specs) When I leave CNMP in automatic, I get connected with some 30Kb speed limit over GSM network

AT+CGMR;+CNMP?;+CFUN?;+CREG?;+CMNB?;+COPS?;+CPSI?
Revision:1351B08SIM7000E
+CNMP: 2
+CFUN: 1
+CREG: 0,1
+CMNB: 1
+COPS: 0,0,"4KA SK 4KA SK",3
+CPSI: GSM,Online,231-03,0x000a,7343,535 DCS 1800,-67,0,39-39
OK

When I force the module to LTE, I just get kicked of the network.

AT+CNMP=38
OK
AT+CGMR;+CNMP?;+CFUN?;+CREG?;+CMNB?;+COPS?;+CPSI?
Revision:1351B08SIM7000E
+CNMP: 38
+CFUN: 1
+CREG: 0,2
+CMNB: 1
+COPS: 0
+CPSI: NO SERVICE,Online
OK

And when I manually select the provider, It just switches back to GSM. And yes, the AT+CNMP? still says 38

Does that mean that the CAT-M1 is not "the same" LTE as in phone? Sorry for stupid question, I'm very confused by all those LTE/4G terms.

[botletics]

LTE CAT-M is not the same as traditional LTE, and using a typical LTE SIM card that is in most smartphones will likely not work.

[VeselaHouba]

Ok, thanks for explanation and fast response.

[nolimitdev]

What is the solution please? I have exact problem described here, but Im sure I have correct special SIM card for just NB-IoT. I have some SIM7000E which connects to NB-IoT correctly but another SIM7000E still forces to GSM but both have the same firmware (as mentioned above 1351B08SIM7000E). I have another SIM 7070G (global band support) and it does the same - ignores forced connection to NB-IoT (AT+CNMP=38 after setting AT+COPS is reverted to 13 -> GSM only). Exactly as described here setting AT+COPS=... waits until I press enter.

[nolimitdev]

I have found where is the problem.... AT+CBANDCFG.

E.g. SIM7000E has by default...

  AT+CBANDCFG?
  +CBANDCFG: "CAT-M",3,5,8,20,28
  +CBANDCFG: "NB-IOT",3,5,8,20,28

but when you change by mistake by running any testing chat-scripts or via AT tool (screen, minicom) it is permanently remembered and maybe saved band number is not compatible with operator of used SIM card.

Also SIM7070G (global variant of SIM7000E which is for Europe primary) by default have only one band number for NB-IOT...

SIM7070G has by default:
  AT+CBANDCFG?
  +CBANDCFG: "CAT-M",1,2,3,4,5,8,12,13,14,18,19,20,25,26,27,28,66,85
  +CBANDCFG: "NB-IOT",8

but for my operator Deutsche/Slovak Telekom NB-IOT has band number 20 but this number by default was not enabled, that is why modem ignores AT+CNMP=38 and still switches to GSM (Deutsche/Slovak Telekom uses band number 8 for E-GSM).

So I fixed it by AT+CBANDCFG="NB-IOT",20