UE states and state transitions including inter RAT

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:

- RRC_IDLE

- RRC_INACTIVE

- RRC_CONNECTED

Ø RRC_IDLE:-

ü A UE specific DRX may be configured by upper layers;

ü  UE controlled mobility based on network configuration

ü  The UE  Monitors a Paging channel for CN paging using 5G-S-TMSI

ü  Performs neighbouring cell measurements and cell (re-)selection

ü  Acquires system information and can send SI request (if configured).

 

Difference Detween LTE and 5G RRC States

Ø RRC_INACTIVE:-

ü  A UE specific DRX may be configured by upper layers or by RRC layer

ü   UE controlled mobility based on network configuration

ü  The UE stores the AS context ; - A RAN-based notification area is configured by RRC layer

ü  Monitors a Paging channel for CN paging using 5G-S-TMSI and RAN paging using I-RNTI.

ü   Performs neighbouring cell measurements and cell (re-)selection.

ü   Performs RAN-based notification area updates periodically and when moving outside the configured RAN-based notification area.

ü   Acquires system information and can send SI request (if configured).

Ø RRC_CONNECTED:-

ü The UE stores the AS context.

ü  Transfer of unicast data to/from UE.

ü  At lower layers, the UE may be configured with a UE specific DRX.

ü  For UEs supporting CA, use of one or more SCells, aggregated with the SpCell, for increased bandwidth.

ü  For UEs supporting DC, use of one SCG, aggregated with the MCG, for increased bandwidth.

ü  Network controlled mobility within NR and to/from E-UTRA.

ü  Monitors a Paging channel, if configured.

ü  Monitors control channels associated with the shared data channel to determine if data is scheduled for it.

ü  Provides channel quality and feedback information.

ü  Performs neighbouring cell measurements and measurement reporting.

ü  Acquires system information.

3GPP TS 38.331 version 15.3.0 Release 15

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