Services and Functions

The main services and functions of the RRC

• Broadcast of System Information related to AS and NAS.
• Paging initiated by 5GC or NG-RAN
• Establishment, maintenance, and release of an RRC connection between the UE and NG-RAN including( Addition, modification, and release of carrier aggregation) & Addition, modification, and release of Dual Connectivity in NR or between E-UTRA and NR.
• Security functions including key management
• Establishment, configuration, maintenance, and release of Signalling Radio Bearers (SRBs) and Data RadioBearers (DRBs).

Mobility functions including

• Handover and context transfer
• UE cell selection and reselection and control of cell selection and reselection
• Inter-RAT mobility

QoS management functions

• UE measurement reporting and control of the reporting.
• Detection of and recovery from radio link failure.
• NAS message transfer to/from NAS from/to UE.

Protocol States

RRC_IDLE

• PLMN selection;
• Broadcast of system information;
• Cell re-selection mobility;
• Paging for mobile terminated data is initiated by 5GC;
• DRX for CN paging configured by NAS.

RRC_INACTIVE

• PLMN selection;
• Broadcast of system information;
• Cell re-selection mobility;
• Paging is initiated by NG-RAN (RAN paging);
• RAN-based notification area (RNA) is managed by NG- RAN;
• DRX for RAN paging configured by NG-RAN;
• 5GC – NG-RAN connection (both C/U-planes) is established for UE;
• The UE AS context is stored in NG-RAN and the UE;
• NG-RAN knows the RNA which the UE belongs to.

RRC_CONNECTED:

• 5GC – NG-RAN connection (both C/U-planes) is established for UE;
• The UE AS context is stored in NG-RAN and the UE;
• NG-RAN knows the cell which the UE belongs to;
• Transfer of unicast data to/from the UE;
• Network controlled mobility including measurements.