Can same NR cell be used as NSA cell and SA cell simultaneously?

Dear NR Experts,
Can same NR cell be used as NSA cell and SA cell simultaneously?


As per my understanding, no.

For NSA, SIB1 Configuration is not required.
Ony MIB is require. In MIB Kssb value for FR1 and FR2 should be more then 12 to 15 and 28 to 31( for perfect value I am not sure. Need to refer spec).

Yes. I see no reason why it can’t be.

Nokia support it. I was wondering how…

Even SIB1 is not required for NSA, but if it is there then it will not impact NSA right?

Traffic steering is main challenge.


Okay. Again, I talk.mostly from a simulated environment perspective.
So spec wise… it has no issues.
For different environments, I am sure there are different challenges.

It will not if Kssb and Ssb arfcn value is same for both nsa and Sa, but in spec 3gpp mentioned about when to use which Kssb value.

For simulation perspective only, same gNB can be connected to 4GC and 5GC simultaneously?
Because NSA (ENDC) UE need 4GC and SA UE need 5GC.

Since can be multiple SSBs as per BWP, there can be SSB linked with SIB1 (SSB for SA) and SSB not linked with SIB1 (SSB for NSA).
So SSB ARFCN and kssb can be same also and different also.
Do you agree?

Ssb contains 20 rb, so for SA 20 and NSA 20 you mean to say?
I don’t think so this is good idea…

Take Anritsu for eg.
Here there is no bifurcation of 4gc or 5gc as such in their box.
They can generate both at a time to be used according to test case requirement.
So you can start with attach on LTE cell1, add NR cell1 as ENDC cell.
And then handover to NR cell1 for SA operation.
Would be a valid scenario in the machine.

There can be multiple SSBs even in case of only SA.
Its basic requirement.
It is required because, if SSB is in bwp 1, and UE is just assigning resources in bwp 4.
So how UE can read ssb if UE supported BW is not equal to full channel BW?
So multiple ssbs are being used.

So HW point of view we still don’t know how its done, right?

Yes. But would it be an invalid scenario in a real networking for a gNB to be connected to a 4gc and 5gc core simultaneously?
Because I would imagine it to be a common scenario given a mix of NSA and SA devices would exist on the network


I am not talking multiple ssb in time domain, I am talking about ssb in frequency domain.
In time domain multiple ssb can be there.

Yes, I am talking about frequency domain only.

SSB is just 20 PRBs. I think UE always have to read those 20 PRBs regardless of the BWP.

Yes, I agree.

Yes, and these happens for all UE.
And when PRBs are not there, it counts as congestion.
Fundamental of getting ERAB or RAB fails due to resources not available.

No, only 1 ssb (20rb) can be there.
Even though ssb is folloing in bwp or out of bwp. As per spec bwp size should be more then 20 rb.
So ssb inside in bwp1 and then bwp switching happen to bwp4, still ue ll read ssb inside the bwp1.

Is there any criteria for BWP switching?
I mean, is it feature or UE dependent?

SSB can be configured separately per BWP.
In 400 MHz BW there can be a UE which can support only 50 MHz BW at a time.
UE cannot keep on changing frequncy every 20 ms just to read ssb, if it falls outside UEs current BWP.

BWP switching can happen dynamically when in connected mode, and it is not necessary to have ssb in each BWP.