Does split bearer always use NR PDCP?
Always NR PDCP for split bearer.
It always uses 5G version of PDCP, but not from gnodeb always.
eNodeB also supports 5G version of PDCP with a sn length of 12bit or more.
But SCG always NR PDCP.
Where as a MCG bearer can be configured with either E-PDCP or NR-PDCP.
Either MCG or SCG it depends on which node RLC Mac and PHY is used.
If Master node RLC MAC PHY are used its MCG.
E-UTRA PDCP -> E-UTRA-RLC/MAC, E-UTRA-PHY) and (NR-PDCP -> E-UTRA-RLC/MAC, E-UTRA-PHY) these are the 2 variations for MCG bearer.
This is how it works, right?
Ye, absolutely, for MCG.
From SharetechNote (Thanks @Jaeku_Ryu):
And I remember seeing same image in the Spec.
Split bearer is using NR PDCP in both cases.
So I didn’t get this point.
What you meant by not from gnodeb?
Did you mean this NR PDCP actually lies in the eNodeB?
In NSA mode master Node PDCP can be configured either as 4G PDCP or 5G PDCP.
Basically it’s about configuration… but ultimately the PDCP is NR.