5G NSA: UE not reporting EN-DC capability

Hello experts!

I’ve been fighting a problem for a long time and being at my wits end I’d like to ask for your help.
The problem is as follows:
I have a 5G NSA test/research network setup with a Samsung S21 as a test device. Everything is working fine when I use the USIM provided by the vendor of the 5G network (UE attaches to the gNB for data), but when I try a different USIM, provided by Sysmocom, the UE does not even report that it is capable of EN-DC. The NAS Attach message is missing the additional UE network capabilities flags and the additional UE security , it’s not just that the DCNR bit is not set.
I have tried to make the USIMs equal in term of services, PLMN and access technology settings, different band of LTE/NR, etc. to no avail. It is as if the UE is behaving as a before Release 14 device with the Sysmocom USIM.
One major difference between the two USIMs is that the Sysmocom has ISIM application and the UE operation mode is ‘normal’, while the other does not.

I’d be much obliged if anyone can give me an advice/hint/lead.

When the UE camped on the network, what is the roaming status seen for both SIMs? I am asking this as some operator reqs are in such a way that they want to disable NR capability in roaming.

Hi pradeep!
I haven’t checked the roaming status, but it should be “Not roaming”, as this is purely a test network and I can change MCC/MNC at will and always set them according to the IMSI or USIM settings.

Change of PLMN, band with new sim can’t guarantee ENDC will work or not.
Binary capability need to enabled in sim using commands.

Hi ankgitm!
Are there technical specifications about those commands? Could you point me to them, so I can read about them?

What is the plmn configured on sim card or mcc-mnc in imsi?

The SIM that works is with the test MCC/MNC 001/01 and the not working is the default of Sysmocom, 901/70.

That is the problem. Mobile software is programmed to enable modem feature based on the mcc-mnc of sim card. Unless you root your phone , and tinker with the modem config files you will not be able to overcome this behavior. Otherwise get a sim card with test mcc-mnc.

Thank you very much! This solved the problem, it never did occur to me that THIS could be the problem.

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