5G NR RRC states

5G NR UE RRC States IDLE, INACTIVE, CONNECTED

The 5G NR UE states are RRC_IDLE, RRC_INACTIVE and RRC_CONNECTED mode.

UE states and state transitions including inter RAT

A UE is either in RRC_CONNECTED state or in RRC_INACTIVE state when an RRC connection has been established.

If this is not the case, i.e. no RRC connection is established, the UE is in RRC_IDLE state.

The RRC states can further be characterised as follows:-

UE RRC state machine and state transitions in NR. A UE has only one RRC state in NR at one time.

UE RRC state machine and state transitions in NR

 

UE RRC state machine and state transitions berween NR/5G, E-UTRAN/EPC

RRC_IDLE: -

• UE specific DRX may be configured by upper layers
• UE controlled mobility based on network configuration; -
• Paging
• PLMN selection
• Broadcast of system information
• Cell re-selection mobility

RRC_INACTIVE: -

• Broadcast of system information
• Cell re-selection mobility
• Paging is initiated by NG-RAN (RAN paging)
• DRX for RAN paging configured by NG-RAN
• 5GC to 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.

Reference: 3GPP TS 38.300.

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