5G RAN can be deployed using both NSA and SA architectures. Non-Standalone (NSA) deployment involves the use of Dual Connectivity (DC). The initial 5G NSA deployment is referred to as EN-DC (EUTRA-NR Dual Connectivity), where the master node is the eNB, and the secondary node is the en-gNB (ENDC gNB).
At the same time, when using 5G NSA mode, you will also encounter many terms related to cell types, cell groups, and cell nodes, such as MCG, SCG, SpCell, etc. Below, we will briefly introduce the definitions of these terms.
5G NR Node Types
5G NR has the following two node types.
- Master Node: In the case of Multi-Radio Dual Connectivity (MR-DC), this node provides the control plane connection to the core network.
- Secondary Node: This node does not have a control plane connection to the core network. In the case of Multi-Radio Dual Connectivity (MR-DC), it provides additional resources to the UE.
5G Cell Group Types
The 3GPP specification defines the following two types of cell groups for dual connectivity:
- MCG (Master Cell Group): This is a group of serving cells associated with the primary RAN node, composed of SpCell (Special Cell, also known as PCell – Primary Cell) and one or more SCells (Secondary Cells).
- SCG (Secondary Cell Group): This is a group of serving cells associated with the secondary RAN node, composed of SpCell (referred to as PSCell – Primary Secondary Cell) and one or more optional SCells.
5G NR Cell Types
According to the 3GPP standard, 5G NR has the following four cell types:
- PCell: Stands for Primary Cell, and it belongs to MCG (Master Cell Group). There may be many cells under MSG. PCell is used for initiating initial access and is considered the primary cell within MCG.
- PSCell: Stands for Primary Secondary Cell, and it belongs to SCG (Secondary Cell Group). PSCell performs initial access under SCG.
- SCell: Represents Secondary Cell, and it belongs to MCG/SCG. A UE may be configured with one or more SCells in connected mode. SCell can be activated or deactivated based on traffic.
- SpCell: Stands for Special Cell, SpCell = PCell + PSCell
