5G NR ScellIndex configuration

Hi Folks,

Recently I observed in a few log files, the scellindex for ENDC 5G-NR SCG is configured with :

Case1: sCellIndex 2,3,4
Case 2: sCellIndex 8,9,10
Case 3: sCellIndex 9,10,11

for SCC1, SCC2, and SCC3 respectively in a 4CA configured network.

Here the spCellConfig uses 1,7 & 8 as servCellIndex respectively.

One sample (case3) is shown below:(9,10,11 case)

servCellIndex 8,

  •     sCellToAddModList 
            **sCellIndex 9,**
            sCellConfigCommon *

sCellIndex 10,
sCellIndex 11,

Can anyone help me to understand what is the deciding factor for this type of index definition?
If life is normal we expect scellindex 2,3, and 4 and PScell in servCellIndex as 1 .
Is this defined by vendors like Nokia ,Ericsson or Huawei ?
If so is there a technical reason of choosing the above 3 cases?

Any help on this topic is highly appreciated


Hi above Pscell config value is for CA case in 5G NR with 4CC …generally this index given in rrc reconfiguration message by network to add SCell with PCell ie Scell addition case …yes agree no sequence can be 1,2,3 4 let me check

I didn’t know UE would also be accepting non sequential numbers also in Sell Index!

Normally, lowest index is used for pCell and other consecutive for sCells. May be with some vendors pCell servCellIndex is already fixed in advance.

Awaiting your reply on this …

I can make a wild guess,If Scell 1 to 6 is used by LTE for 7 CA, there is possibility for 5G SCG PSCell will be 7 and SCG SCC1 can take values from 8,910…and so on for Eg :may be a multiradio e/gNB

But still I see for case 3 , PSCell taking value 8 ,and SCG scc1 from 9,10,11…which makes me confused to even guess the above point.


Hello ankit, we need to under the network configuration before I could answer your question.

Like how many frequency bands and sectors are used in this cell.

Usually it happens because of different technology/bands co-located.

I could only guess that 1,2,3,4 are the LTE and 8,9,10,11 are NR.

If that so you can call me at 8586972332. I will ask you few questions and than may be I can explain this.

One thing is clear that these nomenclature are defined during the network planning phase and has got nothing to do with vendor however vendor could help operator decide the same.

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Thank you for your response
I can say that both scellindex 2,3,4 and 8,9,10 are for pure 5G band 27GHz where it is not used for LTE.