UE restrictDCNR - use of dual connectivity with NR is restricted

Hi Experts, I have a query:
In NSA mode if UE receives restrictDCNR (use of dual connectivity with NR is restricted) in attach accept, won’t UE be able to add NR cell?

Yes, I think think it would not be able to add.

I also think adding NSA would not be possible.
This restrict DCNR comes in attach accept and it is due to SIM not provisioned for NR.

Sometime you can overtake this restrict DCNR=true by forcing UE to 3G and then forcing it to 5G.
Here are the steps how to do it:

  1. 4G attach in any MME
  2. put the phone in 3G: Preferred Network Type : Prefer 3G
  3. change Preferred Network Type : Prefer 5G. (Most likely the MME takes the profile from 3G SGSN and it doesn’t get any 5G restriction from there since the SGSN doesn’t know what 5G is. The 5G restriction is set in HSS.)
  4. Enjoy 5G.

If it doesn’t work from the 1st time, repeat steps 2 and 3.

More details about restrict DCNR=1 here:

Ok. Spec says this.

If the RestrictDCNR bit is set to “Use of dual connectivity with NR is restricted” in the EPS network feature support IE of the Attach Accept/Tracking Area Update Accept message, the UE provides the indication that dual connectivity with NR is restricted to the upper layers.

With the above methode (force to 3G then force to 5G) people get access to 5G VDF romania without any special needs.
Otherwise it needs special subscription at VDF.
This trick works with Huawei EPC Core.
Don’t know for other vendors what will happen.

All the screenshots are taken with NSguru.
Fantastic UE monitoring tool that allows saving DT logs directly in the phone for 2G/3G/4G/5G in dlf format (Qualcomm) or csv format.
It is a better option than TEMS ( which costs a lot) because NSGuru is only 50 usd/month.
It needs root on the phone and Qualcomm chipset.
Here’s a short movie of what this app can do:

I am so pleased with this NSGuru tool. :wink:
It allows to take officially any kind of logs in 4G and 5G.
You can find it in Google Play store “Network signal guru”.

I have a different understanding though.
When it says restricted doesnt it mean UE can access 5G only with LTE as anchor?

It means that this specific UE with this specific SIM card cannot acces the 5G NSA.
Of course it can access the LTE network normally.

Whether UE can use a specific LTE band as an achor depends on multiple parameters:

  1. First UE has to support that LTE+NR band combination (check in cacombos dot com for this).
  2. Parameters of vendors have to allow that LTE carrier as an anchor for 5G NSA. In Huawei PCC anhoring is a very complicated topic based on traffic volume, uplink quality of voice call for example traffic, volume, etc.

For this restrict DCNR you can also read a lot about it here:


Ue will not add NR but send MR only for NR.

UE will not be configured with B1 measurement events if restrictDCNR=1.

Ok thanks.
It means if we provisioned B1 at eNodeB then in RRC connection reconfig UE will discard it.
Let me configure and check.

Actually eNodeB will not configure UE with B1 IRAT measurements.
Don’t know what UE will do.

Actually in our lab we are seeing though UE receives DC with NR as restricted in attach accept.
It is able to measure NR and add NR cell.

So a bit confused… :frowning:

Which UE please?

Mediatek, Samsung.

Please make sure you are looking at right message.
There are 2 of them.

:attachh request:n The message carries the NAS Attach Request.
The DCNR bit in the “UE Network Capability” IE is set.
This signals to the 4G Core Network that the UE supports dual connectivity with 4G-LTE and 5G-NR.
The answer is in the attach accept where restrictDCNR is either present (meaning no 5G NSA possible for this UE and this SIM card) or it missing (meaning5g NSA possible).

So again where are you looking at DCNR?
Attach request or attach accept?

Im looking at attach accept.

If the build in the UE is old, I see not all 3gpp stuff are strictly followed.
So this might be one of the case.
Do make sure you have the latest build.

So we can say that your UEs do not follow 3gpp specs…

Yes, that can happen in old UE build.
I have also seen this behaviour with certain IE.
And the behaviour was corrected in the newer versions.

Based on above picture eNodeB does/should not setup B1 NR measurements setups for that UE.
So which vendor of eNodeB you are facing this problem?