Section: 4.2.1 UE states and state transitions including inter RAT
Content: 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: - A UE specific DRX may be configured by upper layers; - At lower layers, the UE may be configured with a DRX for PTM transmission of MBS broadcast; - UE controlled mobility based on network configuration; - The UE: - Monitors Short Messages transmitted with P-RNTI over DCI (see clause 6.5); - Monitors a Paging channel for CN paging using 5G-S-TMSI, except if the UE is acting as a L2 U2N Remote UE; - If configured by upper layers for MBS multicast reception, monitors a Paging channel for CN paging using TMGI; - Performs neighbouring cell measurements and cell (re-)selection; - Acquires system information and can send SI request (if configured); - Performs logging of available measurements together with location and time for logged measurement configured UEs; - Performs idle/inactive measurements for idle/inactive measurement configured UEs; - If configured by upper layers for MBS broadcast reception, acquires MCCH change notification and MBS broadcast control information and data. - RRC_INACTIVE: - A UE specific DRX may be configured by upper layers or by RRC layer; - At lower layers, the UE may be configured with a DRX for PTM transmission of MBS broadcast and/or a DRX for PTM transmission of MBS multicast; - UE controlled mobility based on network configuration; - The UE stores the UE Inactive AS context; - A RAN-based notification area is configured by RRC layer; - Transfer of unicast data and/or signalling to/from UE over radio bearers configured for SDT. - The UE: - Monitors Short Messages transmitted with P-RNTI over DCI (see clause 6.5); - While T319a is running, monitors control channels associated with the shared data channel to determine if data is scheduled for it; - While T319a is not running, monitors a Paging channel for CN paging using 5G-S-TMSI and RAN paging using fullI-RNTI, except if the UE is acting as a L2 U2N Remote UE; - If configured by upper layers for MBS multicast reception, while T319a is not running, monitors a Paging channel for paging using TMGI; - Performs neighbouring cell measurements and cell (re-)selection; - Performs RAN-based notification area updates periodically and when moving outside the configured RAN-based notification area; - Acquires system information and, while SDT procedure is not ongoing, can send SI request (if configured); - While SDT procedure is not ongoing, performs logging of available measurements together with location and time for logged measurement configured UEs; - While SDT procedure is not ongoing, performs idle/inactive measurements for idle/inactive measurement configured UEs; - If configured by upper layers for MBS broadcast reception, acquires MCCH change notification and MBS broadcast control information and data; - If configured for MBS multicast reception in RRC_INACTIVE, acquires multicast MCCH change notification and MBS multicast control information and data; - Transmits SRS for Positioning. - RRC_CONNECTED: - The UE stores the AS context; - Transfer of unicast data to/from UE; - Transfer of MBS multicast data to UE; - At lower layers, the UE may be configured with a UE specific DRX; - At lower layers, the UE may be configured with a DRX for PTM transmission of MBS broadcast and/or a DRX for MBS multicast; - At lower layers, the UE may be configured with a cell specific cell DTX/DRX; - For UEs supporting CA, use of one or more SCells, aggregated with the SpCell, for increased bandwidth; - For UEs supporting DC, use of one SCG, aggregated with the MCG, for increased bandwidth; - Network controlled mobility within NR, to/from E-UTRA, and to UTRA-FDD; - Network controlled mobility (path switch) between a serving cell and a L2 U2N Relay UE, or vice versa. - The UE: - Monitors Short Messages transmitted with P-RNTI over DCI (see clause 6.5), if configured; - Monitors control channels associated with the shared data channel to determine if data is scheduled for it; - Provides channel quality and feedback information; - Performs neighbouring cell measurements and measurement reporting; - Acquires system information; - Performs immediate MDT measurement together with available location reporting; - If configured by upper layers for MBS broadcast reception, acquires MCCH change notification and MBS broadcast control information and data. Figure 4.2.1-1 illustrates an overview of UE RRC state machine and state transitions in NR. A UE has only one RRC state in NR at one time. Figure 4.2.1-1: UE state machine and state transitions in NR Figure 4.2.1-2 illustrates an overview of UE state machine and state transitions in NR as well as the mobility procedures supported between NR/5GC, E-UTRA/EPC and E-UTRA/5GC. Figure 4.2.1-2: UE state machine and state transitions between NR/5GC, E-UTRA/EPC and E-UTRA/5GC Figure 4.2.1-3 illustrates the mobility procedure supported between NR/5GC and UTRA-FDD. Figure 4.2.1-3: Mobility procedure supported between NR/5GC and UTRA-FDD