The 5G RAN can be deployed with NSA and SA architecture. Non-Standalone deployment involves utilizing the DC (Dual Connectivity). The initial 5G NSA deployment, known as EN-DC (EUTRA–NR Dual Connectivity ), Where Master RAN Node is a eNB and the Secondary RAN Node is an en-gNB (ENDC gNB).
When working with 5G NSA mode, we hear daily many acronyms related to Cells Types, Cell groups and Cell nodes like Master Node, MCG, SCG, SpCell etc. In this post, we have tried to simply will definition of these acronyms.
5G NR Node Types
There are following 2 node type in 5G NR and also depicted in picture.
- Master Node: This node provides the control plane connection to the core network in case of multi radio dual connectivity (MR-DC).
- Secondary Node: This node will not have control plane connection to the core network. It provides additional resources to the UE in case or MR-DC.
5G Cell Groups Types
There are following two types of Cell Groups defined for Dual Connectivity by the 3GPP Specifications.
1. MCG (Master Cell Group)
2. SCG (Secondary Cell Group)
- Master Cell Group – This is a group of serving cells associated with the Master RAN Node, comprising of the SpCell (Special Cell) which is known as the PCell (Primary Cell) and optionally one or more SCell (Secondary Cell).
- Secondary Cell Group – this is a group of serving cells associated with the Secondary RAN Node, comprising of the SpCell which is known as the PSCell (Primary SCell) and optionally one or more SCells
5G NR Cell Types
As per 3GPP, there are following 4 types of cells in 5G NR:
- PCell means Primary Cell. It will come under MCG. There might be many cells under MSG. PCell is used to initiate the initial access and considered as main cell in MCG.
- PScell means Primary Secondary Cell. It will come under SCG. PSCell performs the initial access under SCG.
- Scell means Secondary Cell. It will come under MCG/SCG. UE might be configured with one or more SCell in connected mode. SCell can be activated or deactivated according to traffic.
- SpCell means Special Cell. A SpCell = PCell + PSCell
- 5G NR Resource Block Definition and RB calculations
- 5G NR Modulation and Coding Scheme (MCS)
- NR-Cell Physical Layer Cell ID
- NR-Primary Synchronization Signal (PSS)
- NR-Secondary Synchronization Signal (SSS)