EG25-G not receiving SMS with China Unicom SIM roaming in the US

IoT Modules LTE Standard Module
1

Hi,

I’m trying to use an EG25-G USB dongle to receive SMS on my China Unicom SIM while roaming in the US. It connects to LTE on both AT&T and T-Mobile, but I haven’t been able to receive any SMS. The same SIM receives messages fine in a phone with VoLTE enabled.

Quectel email support suggested asking here.

The dongle is connected to Windows, and these are its firmware details:

ATI
Quectel
EG25
Revision: EG25GGBR07A08M2G

AT+QGMR
EG25GGBR07A08M2G_01.002.01.002

AT+CSUB
SubEdition: V07

AT+CVERSION
VERSION: EG25GGBR07A08M2G
Jun 13 2020 16:25:23
Authors: QCT

Here are the results while connected to T-Mobile:

AT+COPS?
+COPS: 0,0,"T-Mobile",7

AT+CEREG?
+CEREG: 0,5

AT+CREG?
+CREG: 0,5

AT+QCFG="ims"
+QCFG: "ims",1,0

AT+QMBNCFG="AutoSel"
+QMBNCFG: "AutoSel",1

AT+QMBNCFG="Select"
+QMBNCFG: "Select",OpenMkt-Commercial-CU

AT+QNVFR="/nv/item_files/modem/mmode/ue_usage_setting"
+QNVFR: 01

I configured AT+CMGF=1 and AT+CNMI=2,1,0,0,0, then checked both SIM and modem storage with AT+CMGL="ALL". Both stayed empty, and there were no incoming-message notifications. Rebooting and sending another test SMS didn’t help.

Could this be related to the US 3G shutdowns and needing SMS over IMS for China Unicom roaming? Since it works in a VoLTE-enabled phone, I’m wondering whether the dongle’s older firmware or carrier profile is missing something needed for this setup.

Is OpenMkt-Commercial-CU the correct profile, and are there any additional IMS/SMS settings I should check? Please let me know which diagnostic commands or logs would help.

I’d also like to update the firmware—it dates back to June 2020. I saw EG25GGBR07A08M2G_A0.304.A0.304 mentioned in another thread. Is that suitable for my SubEdition V07, and can I upgrade directly from 01.002.01.002? Could you provide the recommended firmware, Windows flashing tool, and upgrade instructions, including any backup requirements or downgrade restrictions?

Thanks,
Bruce

2

Hello,

On AT&T and T-Mobile, 3G/WCDMA is shut down, so a roaming device cannot use the legacy CS (3G) path for SMS. In this case SMS must arrive via SMS over IMS (device registers to IMS and receives SMS over IP) or via SMS over the SGs path over LTE. Your China Unicom SIM receives SMS in a VoLTE phone, so the SIM supports IMS/VoLTE. The issue is whether the EG25-G registers to IMS on the visited US network.

Your module config looks correct:

  • IMS enabled: AT+QCFG="ims" returns 1.
  • Registered on LTE and roaming: +CEREG: 0,5 and +CREG: 0,5.
  • Carrier profile selected: OpenMkt-Commercial-CU (China Unicom).

The likely missing piece is IMS registration, or the carrier profile not carrying the correct IMS/SMS-over-IMS configuration for the visited network. Firmware and AT command changes alone will not enable SMS over IMS if the operator does not provision IMS for the roaming SIM.

Please run these checks

  1. IMS registration status:
    • AT+CIREG? (if your firmware supports it; some builds return ERROR and have limited IMS debug).
    • AT+CEER (a value indicating IMS not registered shows the IMS bearer is not up).
    • Re-issue AT+QCFG="ims" to confirm IMS is still enabled after any reset.
  2. IMS APN and bearer:
    • AT+CGDCONT? (check if an IMS APN context exists).
    • AT+CGCONTRDP (check if the IMS bearer is active and has an IP address).
  3. Carrier profile:
    • AT+QMBNCFG="List" to list available profiles.
    • Try the generic profile for the visited network (OpenMkt-Commercial or ROW_Generic_3GPP) when roaming, then re-check IMS registration. The CU profile is tuned for the home network and may not provide SMS over IMS on T-Mobile or AT&T.

Please check your email, I will send you the latest firmware, along with the flashing tool. Once you have it, please proceed with the update and then confirm the IMS registration results.

3

Hi,

Thanks for the help and for sending the firmware!

A quick update after some more testing: before flashing, incoming SMS unexpectedly started working on the original 01.002.01.002 firmware. I confirmed fresh messages on both T-Mobile and AT&T, including an emoji message in text mode. It also worked after removing the Windows messaging app, so neither that app nor PDU mode was required at that point. I still haven’t established why the earlier tests failed.

I’ve now successfully updated to EG25GGBR07A08M2G_A0.304.A0.304 using QFlash. There are some clear changes while roaming on AT&T:

Check Before update After update
Selected MBN OpenMkt-Commercial-CU CU-VoLTE
AT+QCFG="ims" 1,0 1,1
AT+CGCONTRDP Active 3gnet context only Active 3gnet and ims contexts

The SIM is ready and both CEREG and CREG report roaming registration (0,5). AT+CIREG? still returns ERROR.

The updated firmware appears to have improved the IMS setup, although SMS had already begun working beforehand. Does the 1,1 result together with the active IMS bearer confirm IMS registration on this build, or is there another command I should use?

Thanks again,
Bruce