ive applica- tions results in frequent state transitions which would cause signaling overhead and additional delays. Therefore to reduce the signaling overhead and the latency, a third state has defined in NR. As shown in Fig. 2.23, in RRC_INACTIVE state, the UE context is maintained in the device and the gNB and the CN connection is preserved (i.e., the device is in CM-CONNECTED state). As a result, the transitions to or from the RRC_CONNECTED state for data transfer becomes more efficient and faster. In this mode, the UE is configured with sleep periods similar to the idle mode, and mobility is controlled through cell reselection without involvement of the network. The characteristics of NR UE states are summarized in Table 2.2. One important difference between the UE states in NR is the way that the mobility is handled. In the idle and inactive states, the mobility is Table 2.2: Characteristics of RRC states in NR [19]. RRC_IDLE RRC_INACTIVE RRC_CONNECTED UE-controlled mobility based on network configuration Network-controlled mobility (cell reselection) within NR and to/from LTE DRX configured by NAS DRX configured by NAS or DRX configured by gNB Broadcast of system information Neighbor cell measurements Paging (CN-initiated) Paging (CN-initiated or Network can transmit and/or NG-RAN-initiated) receive data to/from UE UE has an CN ID that uniquely NG-RAN knows the RNA NG-RAN knows the cell which the identifies it w/in a tracking area which the UE belongs to UE belongs to No UE context stored in gNB UE and NG-RAN have the UE AS context stored, and the 5GC-NG-RAN connection (both control/user-planes) is established for the UE New Radio Access Layer 2/3 Aspects and System Operation 245 Handover E-UTRA RRC_CONNECTED NR RRC_CONNECTED Resume/release with suspend Connection Connection E-UTRA establish/ establish/ RRC_INACTIVE* RRC_INACTIVE release release reselection Release Release reselection E-UTRA RRC_IDLE NR RRC_IDLE *The E-UTRA RRC_INACTIVE state is only supported when E-UTRA Is connected to 5GC Figure 2.24 UE