CREG 0,3 and 0,0 issues when CGREG and CEREG work fine

Connectivity SIM Cards
1

Hello All,

This is my first post here…

We are using Quectel EM06-A modems with hologram in a marine application where the units move in and out of cell coverage and are having issues with registering on the circuit switch network. When the devices are in cell coverage the packet network end of things always works… in other words AT+CGREG and AT+CEREG always return 0,5 which means registered and roaming. However, AT+CREG often fails and returns mostly 0,3 and sometimes 0,0 which means that the unit registration is denied and the unit is no longer attempting to register. Registration success seems to be carrier dependent but we have seen failures on most. its hit or miss. In all cases forcing a new registration process usint AT+COPS=1 or AT+COPS=2 followed by AT+COPS=0 seems to work BUT may require multiple tries.

We need to be able to send SMS messages to these units so its critical that we get CREG registration working reliably.

Here is an example for a unit in Miami…

root@ZenVMS:/etc/gcom# cu -l /dev/GSM
Connected.
at
OK
at+cops?
+COPS: 0,0,“Sprint Hologram”,7

OK
at+creg?
+CREG: 0,3

OK
at+cgreg?
+CGREG: 0,5

OK
at+cereg?
+CEREG: 0,5

OK

Now… watch this…

at+cops=0
OK
at+creg?
+CREG: 0,3

OK
at+creg?
+CREG: 0,2

Note that the cops=0 above forces re-registration.
OK
at+cops?
+COPS: 0

OK
at+cops?
+COPS: 0,0,“Sprint Hologram”,7

OK
at+creg?
+CREG: 0,3

OK

so the registration fails… so we try again…

at+cops=0
OK
at+creg?
+CREG: 0,2

OK
at+cops?
+COPS: 0

OK
at+cops?
+COPS: 0,0,“T-Mobile Hologram”,7

OK
at+creg?
+CREG: 0,5

OK

note that this time we connect to T-Mobil and voila… CREG works!

i have not been able to get CREG to work with sprint. Here are the available carriers at this units location.
at+cops=?
+cops: (1,“AT&T”,“AT&T”,“310410”,7),(3,“311 490”,“311 490”,“311490”,7),(2,“T-Mobile”,“T-Mobile”,“310260”,7),(1,“Sprint”,“Sprint”,“310120”,7),(3,“313 100”,“313 100”,“313100”,7),(1,“AT&T”,“AT&T”,“310410”,2),(1,“311 882”,“311 882”,“311882”,7),(3,“312 250”,“312 250”,“312250”,7),(1,“312 530”,“312 530”,“312530”,7),(3,“Verizon”,“Verizon”,“311480”,7),(0-4),(0-2)

OK

Any thoughts on how this problem might be addressed is greatly appreciated.

Thanks,

–luis

2

hologram support says the following

Thanks for your continued patience on this. We have investigated the issue with Sprint and have found that the Sprint network is purely an LTE network. Some mobile devices/modems require connecting to an LTE network that is capable of interacting with a 3G/2G network to allow SMS functionality. This functionality is referred to as SMS over SGs and is not supported by Sprint (devices connected to it can only use data as confirmed by the carrier).

Which means that SMS using circuit switch will not work for Sprint since its an LTE only carrier.

But… the module we are using (EM06-A) supports IMS (IP Multimedia Subsystem) which among other things supports SMS over LTE. However, when I try to enable this on my unit the IMS fails to register…

as in…

AT+QCFG=“ims”
+QCFG: “ims”,1,0

OK

a quick search on the hologram forum comes up with

and specifically…

Hi @cblack,

Currently, we do not provide an IMS APN, as most LTE devices have SMS compatibility without it.

What module(s) are you currently looking at, and what’s your use case for SMS?

Thanks,
PFW

which tells me that SMS over LTE only networks is not supported by Hologram ?!?!

can someone at hologram comment on this? Given that Sprint is an LTE only carrier (and that other carrier are moving in that direction) seems to me that IMS/SMS over LTE should be something supported by Hologram.

Looking forward to comments.

–luis

3

Hello All,

here is hologram’s response to my continued inquires on the matter of SMS over Sprint which is an LTE only carrier making it impossible to send SMS over this network using a hologram SIM.

I quote hologram support:

“I just confirmed internally that we do not support VoLTE. Since IMS is the framework in which VoLTE runs, then enabling it in the modem will still not make SMS work over Sprint.”

and of more concern…I quote

  • Sprint coverage effectively no longer exists, since the new T-Mobile network coverage is much better than the old Sprint coverage nationally.

  • The SMS service issue is due to the old Sprint services being dismantled and soon the entire Sprint network will in effect be shut down.

  • The solution is to remove Sprint coverage and replace it with T-Mobile coverage where you can fully continue to use SMS services under the improved coverage.

which I read to mean… Sprint is going away so there is no need to be concerned since other carriers currently support SMS over SGs.

so basically (recapping) the way I read this is

  1. Hologram does not support IMS

  2. Hologram can’t be used for SMS on LTE only networks that do not support 2G/3G

  3. Hologram requires SGs over SMS for SMS which depends on 2G/3G

which brings me to this document…

and the fact that many carriers have announced the discontinuation of 2G/3G in 2022 including

  • [AT&T] announced that it will finish shutting down its 3G network by February 2022.

  • [Verizon] announced that will finish shutting down its 3G network by Dec. 31, 2022.

  • [T-Mobile] announced that it will finish shutting down Sprint’s 3G network by Jan. 1, 2022 and Sprint’s LTE network by June 30, 2022. It also plans to shut down T-Mobile’s 2G and 3G networks, but has not yet announced a date.

Page 7 of the above document states

“data centric terminal: higher possibility of losing voice and SMS services”

and in section 3.3

“SMS are based on SGs interface, reusing 2/3G MSC, for mobile originated and terminating SMS”

So…

  1. can we get assurances from Hologram that SMS will continue to work through their network in 2022 as carriers discontinue their 2G/3G networks?

  2. Can hologram provide us with guidance on how they plan to address the future of SMS on their network.

Looking forward to hearing form a knowledgable resource at Hologram.

Thanks,

–Luis

4

Hey, sorry for any confusion here. The SMS issues are only with Sprint due to them being absorbed into TMo and shut down. We will continue to support SMS with no issue for other LTE networks going forward, even past the 2G/3G sunset.

5

Hello Reuben,

Thank you for your reassuring reply. I assume that you represent Hologram’s official position on SMS after the post 2/3G sunset transition.

Its important for us to know if any settings need to be changed on our devices before the transition OR if our devices will continue to work exactly the same using CREG and SMS over SGs as they do now.

Please advise so that we can program all of our devices appropriately before shipping and deployment.

Thanks,

–luis

6

It’s hard to really say for every single device but our understanding is that most should transition fine. We have done some testing here with LTE-only devices with no issues. We’ll continue that testing and we would suggest reaching out to your device manufacturer to see if they suggest any specific settings you might want to look at to try to simulate these conditions before.
We’ll look through own internal knowledge base to see if we have any suggestions for you on that modem.

7

What technology are the LTE only devices using for SMS? Its not IMS since you don’t support that. Please advise so that we can make sure that we setup our quectel EM06-A modems appropriately.

I am assuming that the LTE modems you are referring to are not using SMS over SGs which (my understanding is) will be going away.

Please advise… as you can tell we are quite concerned about SMS and the 2G/3G sunset and need to make plans for our devices in the field.

–Luis

8

Hello All,

the status of SMS post the 2G/3G migration continues to be in flux. Last week I receive the following reassuring email from Hologram. I quote

Thank you for your patience whilst we have been working with our network team to confirm SMS support.

You previously reference the GSMA NG.121 document where several options are proposed in section 5.

There are several reasons why operators are choosing to sunset their 2/3G networks but one of the primary drivers is to free up radio spectrum for 4/5G. Therefore we expect that the favored approach will be that described in section “5.3 Partial 2/3G removal” or “5.1 Limited 2/3G radio network” (particularly outside the US). One reason for this approach is to maintain support for IoT/M2M devices that were never intended for VoLTE/IMS.

For example it has been confirmed to us by AT&T in the US that whilst they will be removing the 3G Radio Access Network elements of the network they will be retaining the MSC/SS7 functionality, meaning that SMS over 4G remains in place (SGsAP interface between MSC & MME). Indeed we have been informed that AT&T are 100% retaining the core network required to deliver SMS to/from their network over LTE without the requirement for VoLTE (*data centric devices).

Please note that as discussed below, Sprint is an exception where there has never been any connectivity to a legacy core network and therefore SMS using the SGs interface is not supported.

to which I replied…

Thanks for the informative response.

My take away form this is that SMS will continue to work as it does now (at least for ATT) after the 2G/3G sunset and that nothing additional is required on our end. Please confirm.

Lets hope the other carriers follow suit.

Still quite nervous about this and hoping that indeed the transition is seamless.

and received this from Hologram…

Yes, that is correct. Nothing additional is required on your end. The transition should be seamless, and if we get any other updates stating otherwise, we will inform you/other customers about it immediately.

However, we continue to have SMS issues with both Sprint (and see no resolution for this carrier as discussed previously in this thread) and surprisingly ATT. Give then statement from Hologram we were under the impression that ATT would continue to support SMS over SGs (2G/3G). However we have a unit in Miami registered with ATT that refuses to register over 2G/3G which prevents SMS working to this units. Here are diagnostics from this morning for this unit.

at+creg?

+CREG: 0,0

OK

at+cereg?

+CEREG: 0,5

OK

at+cgreg?

+CGREG: 0,5

OK

at+cops?

+COPS: 0,0,“AT&T Hologram”,7

OK

at+cops=?

+cops: (1,“T-Mobile”,“T-Mobile”,“310260”,7),(3,“313 100”,“313 100”,“313100”,7),(3,“311 490”,“311 490”,“311490”,7),(1,“312 530”,“312 530”,“312530”,7),(2,“AT&T”,“AT&T”,“310410”,7),(1,“Sprint”,“Sprint”,“310120”,7),(3,“311 882”,“311 882”,“311882”,7),(3,“Verizon”,“Verizon”,“311480”,7),(1,“312 250”,“312 250”,“312250”,7),(1,“AT&T”,“AT&T”,“310410”,2),(0-4),(0-2)

OK

on Friday CREG failed with code 3. Today… its failed with code 0.

a 0 being “Not registered. ME is not currently searching a new operator to register to”
and 1 being “Registration denied”

Interestingly we have a unit in TN that registers correctly with ATT.

So wondering what is going on in Florida and if anyone else is experiencing SMS issues.

Input on this matter would greatly be appreciated.

Looking forward to your comments.

Thanks,

–Luis

9

I might add that the same unit in Miami works fine when connected to T-Mobile.

10

Hello All,

Today we have a unit in the Tampa/St. Petersburg area also registered with ATT having the exact same problem. CREG fails but EREG registers correctly. So the ATT units in Florida are able to do data but not SMS.

Anyone experiencing this issue in Florida or other parts of the country? We have a unit in TN that is currently registered with ATT and working fine with SMS.

Today… Feb 22, 2022 is the day ATT has announced the disconuation of 2G/3G services. So not too surprised that this is happening.

just wondering if anyone else is seeing this or just us.

looking forward to hearing from anyone else having SMS issues out there.

Thanks,

–Luis

11

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