Anyone know the difference between EN-DC and Coexistence (DSS)?

I know EN-DC is when you have a MCG which is LTE and SCG which is 5GNR. While DSS allows the LTE and NR to share the spectrum. Anyone have further insights?’

Thank you

ENDC is a user-based concept. There are 2 nodes (Lte Master node and secondary NR node) and at least 2 cells: min 1 LTE cell (Pcell) and min 1 NR(PScell). In order for the user to access the NR cells (SCG), the user must first connect to the LTE cell (MCG)

DSS is a cell-based concept. At least 2 cells from 2 different technologies use the same spectrum ( typically 1 LTE cell and 1 NR cell). Each cell has its own users. The schedulers are designerd to ensure no collision between the traffic of each cell.

The 2 concepts can exist together.

Thank you! A couple of more questions come to mind.

Question 1 for ENDC does RACH have to occur on the secondary NR node?
Question 2 Can the two cells in DSS use the same time frequency resources and possibly interfere with each other? ?

Appreciate your insights

  1. Yes, RACH to PSCell must occur

  2. No, each cell uses separate time frequency

DSS is completely transparent to LTE users but NR uses must support some optional capabilities ( e.g. rate matching around LTE CRS)