Radio Resource Control (RRC) states for NR
There are Three RRC states in NR
- RRC IDLE
- RRC CONNECTED
- RRC INACTIVE
Note :UE in RRC IDLE cannot move to RRC INACTIVE
- To complete cell selection and cell reselection ,the SI is necessary.
- UE read SI from BCCH.
- SI also provides the information related to complete the Random Access and RRC Connection Setup procedures.
- The UE performing mobility triggered Registration Area updates to ensure that the UE is always reachable by the AMF(knows where to forward the paging message).
- UE monitors the PDCCH (DCI) Format 1 0 using the P-RNTI defined by the Discontinuous Reception (DRX) pattern.
- 5G-S-TMSI is used to address UE within Paging message.
- 5G-S-TMSI is allocated by AMF.
- To improve security 5G doesn’t support IMSI based paging.
- UE is unable to transfer application data while in RRC Idle.
- Transfer of both application data and signaling between the UE and network is done in connected mode.
- Application data transferred by using DRB and signaling can be transferred using SRB.
- CRNTI is provided by Base station to address UE during RACH.
- AMF maintains NG signaling connection with Base Station.
- UPF maintains GTP-U tunnels with Base Station.
- UE monitors Control Channels for Resource Allocations.
- The UE reports Channel State information (CSI).It includes CQI,RI,PMI,LI,CRI (CSI-RS Resource Indicator) and SSBRI (SS/PBCH Block Resource Indicator).
- RRC context and CORE network connection is kept in both the UE and the gNB.
- Transition to connected state for data transfer is fast.
- RRC inactive make the device in sleep like an idle state but the mobility is handled through cell reselection without involvement of network.
- Its acts like mix combo of IDLE and Connected state.