TIVE state. As shown in Fig. 2.23, when a UE is powered up, it is in disconnected and idle mode. However, the UE can transi- tion to the connected mode with initial access and RRC connection establishment. If there is no UE activity for a short period of time, the UE can suspend its active session and tran- sition to the inactive mode. Nevertheless, it can resume its session by moving to the con- nected mode. 5G applications and services have different characteristics. To meet the requirements of different services, it was imperative to reduce the control-plane latency by introducing a new RRC state machine and a dormant state. The URLLC services are Power up Attach/RRC connect RRC suspend RRC_IDLE CONNECTED INACTIVE Detach/RRC release Deregistered, idle RRC resume Registered, connected Connection failure Connection failure Registration reject Registration update accept AN signaling connection established Registration accept (initial NAS message) RM-DEREGISTERED RM-REGISTERED CM-IDLE CM-CONNECTED Deregistration AN signaling registration reject connection released UE status Attach Idle/registered Connected to EPC Active UE status Attach Connected/inactive Connected/active EMM state Deregistered Registered RM state Deregistered Registered ECM state Connected CM state Connected RRC state Connected Connected RRC state Connected Inactive Connected Mobility UE-based UE-based Network-based Mobility UE-based UE-based/NW assisted Network-based Figure 2.23 NR UE states and comparison to LTE 8,14]. New Radio Access Layer 2/3 Aspects and System Operation 243 characterized by transmission of frequent/infrequent small packets that require very low latency and high reliability; thus the devices must stay in a low-activity state, and intermit- tently transmit uplink data and/or status reports with small payloads to the network. There is further a need for periodic/aperiodic downlink small packet transmissions. A UE can move to RRC idle mode from RRC connected or RRC inactive state. A UE needs to register with the network to rece