There is a lot of new terms used in a connection to Dual Connectivity
The signaling connection for the UE is anchored at the Master Node. The cell UE is using in the MN node is called PCell Primary Cell. The UE also use the cell from the Secondary Node and this cell is called PSCell Primary Secondary Cell.
All radio resources used within MN are refered as MCG Master Cell Group, the resources from the SN are referred as SCG Secondary Cell Group. Figure 1 illustrates all those terms.
|Figure 1 PCell, PSCell, MCG and SCG|
While using PCell and PSCell, or rather Dual Connectivity, it is also possible to use Carrier Aggregation within both Master Node and Secondary Node. One or more SCells Secondary Cells might be configured. This is shown in Figure 2.
|Figure 2 PCell, PSCell and SCells|