in CONNECTED, the UE is fully controlled by the network, and in IDLE, the UE is mostly functioning autonomously without (explicit) network control. Unsurprisingly, the INACTIVE state falls somewhat in between these, although it is closer to the IDLE than to the CONNECTED state. The various differences and similarities for each RRC state summarized in Table 7.1 Inter-RAT mobility is also supported between various RRC states, with some excep- tions: Mobility between NR and UTRAN/GERAN is not supported in Release 15, nor 7 5G Radio Protocols Figure 7.16 RRC states and allowed state transitions. RRC_CONNECTED Suspend Release Resume RRC_INACTIVE Release Setup RRC_IDLE Table 7.1 UE operation in different RRC states. RRC state UE operation RRC_IDLE RRC_INACTIVE RRC_CONNECTED Connection control UE-based (based only UE-based (based only Network-based (via on received SI) on stored RAN area RRC messages between and received SI UE and network) configuration) Mobility UE-based: Reselection UE-based: Reselection Network-based: based on SI and stored based on SI and stored Network decides and RRC release RRC release triggers any cell configuration configuration changes System information UE monitors SI and UE monitors SI, UE monitors SI (with maintenance and CN-based paging CN-based paging, paging used for SI paging from network RAN area - based changes) notifications from network Measurement As configured by RRC reporting (used for cell (used for cell (Periodic or reselection but not reselection but not event-triggered reported) reported) reporting) RRC context stored at SI from serving cell RRC context RRC context configured by network, configured by network SI from serving cell and stored RAN area configuration is a direct transition from NR RRC_INACTIVE to LTE RRC_INACTIVE state. This is partly because the initial NR deployments were envisioned to be done where LTE cover- age existed already, and support for older systems was to be done later if seen necessary. Having fewer inter-RAT transitions also simplifies the inter-R