RRC STATES

Radio Resource Control (RRC) states for NR. There are Three RRC states in 5G-NR

1.RRC IDLE

2.RRC CONNECTED

3.RRC INACTIVE

Note :UE in RRC IDLE cannot move to RRC INACTIVE

RRC IDLE

•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.

•To address UE within Paging message 5G-S-TMSI is used and allocated by AMF.

•To improve security 5G doesn’t support IMSI based paging.

•UE is unable to transfer application data while in RRC Idle.

RRC CONNECTED

•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 INACTIVE

•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.