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5G NR 中的 PCell / SCell / PScell / SpCell

四种 cell 之间的区别和联系

abbrenameconditionproperties
PCellPrimary Cellunder MCG* Under MCG there may be many Cells,
* PCell is used to initiate the initial access.
* As the name implies, PCell is the most “main” cell in MCG.
PSCellPrimary Secondary Cellunder SCG* Most important cell under the SCG.
* PSCell Performs the initial access under the SCG
SCellSecondary Cellunder MCG / SCG* PCell is the cell which UE initially finds and connects to,
* One or more SCells can be configured once the UE is in Connected mode.
* SCell can be rapidly activated or deactivated to meet the variations in the traffic Pattern.
SpCellSpecial Cell* SpCell = PCell + PSCell
* a lot of signaling is only sent on PCell and PSCell.
* SpCell supports PUCCH transmission and contention based Random access.
* It is always activated

两种 Cell Group - Master & Secondary

abbrenamepropertiesprimary cell
MCGMaster Cell groupgroup of serving cells associated with the Master Node comprising of the PCell and optionally one or more SCellsPCell
SCGSecondary Cell groupSpCell = PCell + PSCell
group of serving cells associated with the Secondary Node comprising of the SpCell (PSCell) and optionally one or more SCells.
PSCell

两种 Node - Master & Secondary

NameTags
Master NodeThe node (radio access node) that provides the control plane connection to the core network in case of multi radio dual connectivity (MR-DC).
Secondary NodeThe radio access node, with no control plane connection to the core network, providing additional resources to the UE in case of MR-DC."
  • Under MCG: The PCell under MCG and the SCell under MCG are united together by Carrier Aggregation (CA) technology.
  • Under SCG: The PSCell under SCG and SCell under SCG are united by CA technology.

Summary:
MCG and SCG are concepts under DC (Dual connectivity). It can be simply understood that the group where the initiates random access (RACH) is performed is the MCG. If there is no dual link, there is no concept of MCG and SCG. It can also be understood that when link is performed, the cell group corresponds to the MCG.

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