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.
