EM12-G VoLTE Registration Failure on Iliad Italy - EMM Detached / IMS Status 0

IoT Modules LTE Standard Module
1

Hi ,

I am facing a persistent issue with an EM12-G module regarding VoLTE/IMS registration on the operator Iliad (Italy). While the Data connection works perfectly (IPv4), the Voice (IMS) registration fails. When attempting a voice call, the call drops immediately, and the error returned is EMM detached.
Note: When I try to call it says busy! :unamused_face:

Here is the detailed context and the steps I have already tried.

Hardware & Firmware Info:

  • Module: Quectel EM12-G
  • Firmware Version: EM12GPAR01A21M4G
  • Connection: Direct connection to Motherboard via M.2 (NGFF) slot (No external USB adapter/dongle used).
  • USB Mode: USB Audio Class enabled via usbcfg. The device is correctly enumerated on the USB bus.
  • Host OS: Linux (running on a VM/System directly connected to the hardware).
  • Operator: Iliad (Italy) - PLMN 22250
  • Network: LTE Band 3 / Band 7 (Signal Strength: Excellent, CSQ ~23)

The Issue:

  1. Data context (CID 1) connects successfully using APN iliad (IPv4).
  2. IMS context (CID 2) is configured, but AT+QCFG="ims" consistently returns 1,0 (enabled but not registered).
  3. When attempting a voice call, the modem returns NO CARRIER or busy signal instantly.
  4. Checking the error with AT+CEER returns: +CEER: EMM detached.

Configuration & Troubleshooting Steps Taken: I have tried multiple MBN profiles and APN configurations with no success.

  • USB/Audio: Audio Class enabled (AT+QCFG="usbcfg",0x2C7C,0x0512,1,1,1,1,1,0,1). lsusb shows the audio device correctly.
  • Network Settings:
    • Roaming enabled (AT+QCFG="roamservice",2).
    • Locked to LTE-Only (AT+QCFG="nwscanmode",3) to prevent CSFB to 3G (since 3G is being decommissioned/unstable in the area).
  • MBN Profiles Tested:
    1. ROW_Generic_3GPP_PTCRB_GCF (Index 10/Generic): Data works, IMS fails.
    2. Commercial-DT-VOLTE (Index 4/16): Fails to register on network (AT+COPS? returns 0).
    3. Commercial-TMO: Fails to acquire IP on Context 1.
  • APN Settings:
    • Tried setting CID 2 (IMS) to IPV4V6, IPV6, and IP.
    • Iliad official specs state IPv4, but setting AT+CGDCONT=2,"IP","ims" results in ERROR on some profiles, or simply fails to register (+CGPADDR: 2 is empty).

Logs & AT Command Outputs:

AT+ATI
Quectel
EM12-G
Revision: EM12GPAR01A21M4G

AT+CPIN?
+CPIN: READY

AT+COPS?
+COPS: 0,0,"Iliad Iliad",7  <-- Connected to LTE

AT+QCFG="ims"
+QCFG: "ims",1,0  <-- VoLTE Not Registered

AT+CGDCONT?
+CGDCONT: 1,"IP","iliad","10.x.x.x",0,0,0,0
+CGDCONT: 2,"IPV4V6","ims","0.0.0.0",0,0,0,0 <-- No IP assigned for IMS

AT+QMBNCFG="list"
(Shows ROW_Generic_3GPP_PTCRB_GCF as Selected/Active)

[After attempting a call]
AT+CEER
+CEER: EMM detached

Questions:

  1. Is there a specific MBN profile for Iliad Italy compatible with this firmware version?
  2. The error EMM detached suggests the network rejects the specific IMS configuration during the call setup. What are the correct CGDCONT parameters for this specific operator on EM12?
  3. Is an update to the firmware required to support VoLTE on this PLMN (22250)?

Thank you for your support.

2

Dear @eros23 ,

Good Day,

Based on what you’ve tried, this looks much more like an MBN mismatch issue.

  1. Is there a specific MBN profile for Iliad Italy compatible with this firmware version?
    Let me check with our internal on this matter

2.The error EMM detached suggests the network rejects the specific IMS configuration during the call setup. What are the correct CGDCONT parameters for this specific operator on EM12?

AT+CGDCONT=2,“IP”,“ims”` Returning ERROR
This usually means **the active MBN forbids manual IMS APN override

  1. Is an update to the firmware required to support VoLTE on this PLMN (22250)?
    [/quote]

Let me check the latest firmware and as well on the Release Notes of any ammendments of the particular issue.

Kindly address to us the following points as well:
a) what is the full version used( use AT+QGMR to check)
b) Is it possible to attach the complete log file?,currently im seeing only AT command flow

Thank You!

3

Hi @Alvin295337,
Thank you for the support.

I have collected all the requested data. I performed the capture on a fresh boot to show the default behavior that causes the failure.

A) Full Firmware Version:
EM12GPAR01A21M4G_01.300.01.300

B) DM Log (Binary Capture):
I have captured the full debug log (.qmdl) using QLog on Windows during a failed call attempt.
Download Link: https://next.tuttomed.com/public.php/dav/files/jmqWKnGq3XSYEx9/?accept=zip

C) AT Command Log Flow:
Below is the status of the modem on the Linux production environment.
Observation: As you suspected, the active MBN (ROW_Commercial, Index 0) seems to conflict with manual settings. You can see in the log below that AT+CGDCONT? shows empty APN names ("") despite my attempts to configure them, suggesting the MBN is overriding/blocking the configuration.

AT+QGMR
EM12GPAR01A21M4G_01.300.01.300

AT+COPS?
+COPS: 0,0,"Iliad Iliad",7

AT+QMBNCFG="list"
+QMBNCFG: "List",0,1,1,"ROW_Commercial",0x0801080A,201904121
[...other profiles...]

AT+CGDCONT?
+CGDCONT: 1,"IPV4V6","","0.0.0.0...",0,0,0,0
+CGDCONT: 2,"IPV4V6","ims","0.0.0.0...",0,0,0,0

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

D) Official Operator Parameters (Required):
For the VoLTE to work, the modem must accept the specific configuration for Iliad Italy, which uses a GID lock. The current generic MBN does not seem to handle this correctly.

  • APN: iliad
  • MCC: 222
  • MNC: 50
  • MVNO Type: GID
  • MVNO Value: F003

E) Cross-Reference (Important):
Please note that I have tested the exact same SIM card on a Quectel EC25-E module (latest firmware) and VoLTE works perfectly.
This confirms that the network side and SIM are fully functional. The issue is strictly related to the EM12-G firmware/MBN lacking the correct mapping for PLMN 222-50 + GID F003.

Request:
Could you please provide a firmware update or the specific .mbn file for Iliad Italy that includes the logic for GID F003?

Thank you.