Can someone please explain why same cell (PCI), both RACH contention based and free?
Please check rach-ConfigCommon in RRC reconfiguration message just before RACH is performed.
If it have dedicated preamble, then RACH will be contention free, otherwise contention based.
Is the 1st case SCG add and 2nd case SCG change?
Then its right way.
1st case is initial SCG addition which can be contention based, 2nd is SCG change (NR to NR handover) so it will be contention free.
Why scg add & scg change need different rach procedure?
The second one is type of HO.
First one is type of Initial access.
This is what i feel.
It is as per 3gpp initial access and dedicated signaling used different RA procedure.
SCG add required contention based.
SCG change required contention free.