5G-NR RRC STATES

Radio Resource Control (RRC) states for NR

There are Three RRC states in 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.
  • 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.

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.


Categories: LTE,5G,TELECOMMUNICATION

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