5G • RAN
PCell
Primary Cell
The primary serving cell in a Master Cell Group (MCG) handling RRC connection, security, and initial PRACH.
Technical Explanation
In Carrier Aggregation and Dual Connectivity, the PCell is the cell on the primary frequency where the UE performs initial connection establishment, security key derivation, and RRC connection reconfiguration. The PCell's uplink carries PUCCH for UCI feedback and cannot be deactivated without handover.
Key Functions
- Terminates RRC control plane connection and NAS security context
- Hosts primary PUCCH carrying HARQ-ACK and CSI for all aggregated SCells
- Remains continuously active and can only be changed via handover
Specifications
3GPP TS 38.300, TS 38.331
Interfaces
Uu
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