5G NR SA/NSA cell reselection scenarios

Dear NR Experts.
Please check below scenarios possible or not:

  1. NSA to NSA cell reselection
  2. NSA to SA cell reselection
  3. SA to NSA cell reselection
  4. SA to SA cell reselection
  5. SA to LTE cell reselection and vice versa

As per best knowledge I think 1, 2 not possible.
Rest all possible.
Please comment.

How 3 is possible?

It seems 3=5.

Isn’t 1 a normal LTE reselection?
There is no 5G secondary cell in idle mode, is there?

Left out 3.
I mean 1, 2, 3 not possible.
4, 5 possible.

Please list if any other scenario there for cell reselection in NR.

For 1 mean cell reselection between 2 SCG cells.
Someone asked me same query.
Please check if any other scenario there for cell reselection in NR.

If question is only about reselection, then I think point 3 is possible.
Provided that SA cell has given NSA frequency to measure to UE via SIB.
Since NSA cell always broadcast SSB signal. Reselection to NSA cell is possible, but UE won’t be able to make RACH, etc…so it’s of no use.

Practically no SA network will broadcast NSA frequency.
Will only give LTE frequency. So no question of point 3.

If my above understanding in not correct , please let me know.

In my view, NSA to NSA cell reselection is not valid at all as reselection happens only in idle mode and hence there is no 5G bearer at that moment.
So, it will be pure LTE-LTE reselection.

Thanks @moradiya. So point 1, 2, 3 not valid scenario.
Any other possible scenario please add in list.

I agree but here for point 3 I mentioned SA to NSA reselection which not look feasible, i.e. SA cell to SCG or MCG cell of ENDC.

Theoretically it’s feasible with conditions I mentioned.
Though it’s not usefull at all.

I’m thinking how NSA cell i.e. SCG can be in idle mode.
For ENDC first step itself is X2 link between MCG and SCG.
Is any definition there for SCG idle in ENDC?

Don’t go by practical call flow.
We are discussing about reselection from SA NR carrier cell to NSA NR carrier cell.
Reselection just require target NSA SSB frequency information and its RSRP/RSRQ.
If SA cell is providing NSA cell ssb frequency then its reselection is possible.
But after reselection UE cannot do anything since MIB SIB are not broadcasted by NSA cells.

Please let me know what’s wrong in this.

MIB is broadcasted in NSA but SIBs are not broadcasted.
Huawei broadcasts even SIB1 in NSA for ANR purpose.

Yes, MIB broadcasted. But not SIB. Which carries RACH information.

UE will not camp/reselect to an NSA cell unless it reads its SIBs to know the qrxlevmin at least.
so I think reselection to NSA is never possible.

You are right. I missed this point.
So it is possible in case sib1 is transmitted.

This ANR for NSA cell to NSA cell neighbour or NSA to SA cell neighbour addition.

For 4G to 5G cell relations.

Then it’s for LTE to SA only I think.
Not seen for ENDC such mechanism still.

Huawei has it but very few UE supports CGI reporting for ANR.

Huawei P40pro supports it:


Actually Mate 40 Pro chinese version is the only UE that has this IE present: nr-CGI-Reporting-ENDC
All the other phones do not have it…yet.

So it mean UE having ENDC can add LTE to 5G SA cell?