haracterized by 5GC and NG-RAN connection (both control and user-planes) establishment for the UEs; storage of the UE AS context in NG-RAN and the UE; NG-RAN knowledge of UE location at cell level; transfer of uni- cast data between the UE and gNB; and network-controlled mobility including measurements. The SI consists of a master information block (MIB) and a number of system information blocks (SIBs), which are divided into minimum SI and other SI. The minimum SI comprises basic information required for initial access and information for acquiring any other SI. The other SI encompasses all SIBs that are not broadcast in the minimum SI. Those SIBs can either be periodically broadcast on downlink shared channel (DL-SCH), broadcast on- demand on DL-SCH upon request from UEs in RRC_IDLE or RRC_INACTIVE states or sent in a dedicated manner on DL-SCH to UEs in RRC_CONNECTED state. A UE is not required to acquire the content of the minimum SI of a cell/frequency that is considered for camping from another cell/frequency. This does not preclude the case that the UE applies stored SI from previously visited cell(s). A cell is barred, if a UE cannot determine/receive the full content of the minimum SI of that cell. In case of bandwidth adaptation the UE only acquires SI on the active BWP. In the next sections, we will discuss layers 2 and 3 functions and procedures in more detail. We will further discuss UE states, state transitions, and important procedures such as idle, New Radio Access Layer 2/3 Aspects and System Operation 201 inactive, and connected mode procedures, random-access procedure, mobility and power management, UE capability, and carrier aggregation. 2.2 Layer 2 Functions and Services 2.2.1 Medium Access Control Sublayer The MAC sublayer performs logical channel multiplexing and controls HARQ retransmis- sions. It also handles scheduling functions and is responsible for multiplexing/demultiplex- ing data packets across multiple component carriers when carrier aggregation is configured. The services of MAC 