How to Clear Configured NSSAI?

IoT Modules 5G Module
1

RM520N-GL

How to Clear Configured NSSAI?

When the modem/MT first registers on a 5G SA network, it uses the default NSSAI configuration set using +C5GNSSAI as the Requested NSSAI. After a successful registration it stores the Allowed NSSAI as Configured NSSAI.

When the modem re-registers on the same network, it uses the configuration stored in the Configured NSSAI as the Requested NSSAI, and ignores what has been configured using +C5GNSSAI.

How to get the modem/MT to delete the Configured NSSAI configuration and the configuration set using +C5GNSSAI again?

I have tried using +CFUN and power-cycling the modem/MT but the Configured NSSAI configuration persists. I have also tried invalidating the TMSI on the network side, but that did not help.

Would the AT+QCFG=“ResetFactory” command delete this configuration? It is safe to use this command often?

ATI
Quectel
RM520N-GL
Revision: RM520NGLAAR03A03M4G

AT+COPS=2
OK

+C5GREG: 1,"000001","03E88A001",11,4,"01.000000"
+C5GREG: 0

AT+C5GNSSAIRDP=3
+C5GNSSAIRDP: 8,"01.000000:01.000002"
+C5GNSSAIRDP: "46007",0,"",4,"01.000000"
OK

AT+C5GNSSAI?
+C5GNSSAI: 8,"01.000000:01.000002"

OK
AT+COPS=1,2,"46007",12
OK

+C5GREG: 1,"000001","03E88A001",11,4,"01.000000"

AT+C5GNSSAIRDP=3
+C5GNSSAIRDP: 8,"01.000000:01.000002"
+C5GNSSAIRDP: "46007",0,"",4,"01.000000"
OK
2

Dear @Ron-McLeod
You can use AT+C5GNSSAI=0,“” to clear.

3

Hi Silva –

I don’t know the internals of the RM520N-GL, but this is the observed behaviour:

  • When a MT (modem) registers with a network, the Requested NSSAI will contain the S-NSSAIs from Configured NSSAI.
  • If the Configured NSSAI is empty, the Requested NSSAI will contain the S-NSSAIs from the Default Configured NSSAI specified with the +C5GNSSAI command.
  • After successfully registering with the network, the MT stores the Allowed NSSAI sent by the network as the Configured NSSAI.
  • Subsequent registration attempts with the network use the stored Configured NSSAI, not Default Configured NSSAI specified with the +C5GNSSAI command. I was able to verify this by watching the NAS messaging between the MT and the AMF.
  • Using the +C5GNSSAI command does update the Default Configured NSSAI, but does not alter the Configured NSSAI which was received the network, and has no affect on the S-NSSAI in the Requested NSSAI sent to the network.
  • I expected that if the MT was restarted that the Configured NSSAI information would be lost and the MT would fallback to using the Default Configured NSSAI specified using the +C5GNSSAI command. However, it appears that the MT stores the the Configured NSSAI in non-volatile storage which is persisted through restarts.

What I am wanting to is clear the information stored in the Configured NSSAI, so that a follow-on registration with the network will use the Default Configured NSSAI specified using the +C5GNSSAI command.

I have seen it mentioned that the +QNVR command may be able to clear NAS-related data, but this seems to be a non-documented command.

I assume that the +QCFG="ResetFactory" command would clear out the Configured NSSAI, but I have not tried this command because I don’t know what side effects it may have, and I don’t know if it is the kind of command which can be executed multiple times.

Thanks for your help,
Ron

4

Dear @Ron-McLeod
This command enables updating the default NSSAI configuration stored at MT. If want to clear, please use AT+C5GNSSAI=0,“” .

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5

I have tried that. It does clear the Default Configured NSSAI, but it does not clear the Configured NSSAI.

After using the AT+C5GNSSAI=0 command, the Requested NSSAI sent with registration attempts still use the the last Allowed NSSAI provided to the MT (which is stored in the Configured NSSAI); I am looking to a way for it to be empty.

6

Dear @Ron-McLeod
Configure NSSAI, which is the NSSAI provided by the network for the UE to use. Once the UE receives this configuration parameter, it will know which S-NSSAI are available in the network.
I am not sure how to clear configured NSSAI.
If the UE does not carry the Allowed NSSAI in the Registration Request message, the network will use the default S-NSSAI to provide services to the UE.

7

Thanks for your reply.

I am guessing that the AT+QCFG="ResetFactory" command would clear out the Configured NSSAI. Is that command safe to use? Would it result in any unexpected side-effects?

8

Dear @Ron-McLeod
AT+QCFG=“ResetFactory” is a internal At command, it is not recommended to use.