 the initial NAS messages during connection setup and connection resume. The NAS messages transferred via SRB2 are also contained 238 Chapter 2 in RRC messages, which do not carry any RRC protocol control information. Once security is activated, all RRC messages on SRB1, SRB2, and SRB3, including those containing NAS messages, are integrity protected and ciphered by PDCP sublayer. The NAS indepen- dently applies integrity protection and ciphering to the NAS messages [14]. 2.3.2 System Information The system information consists of an MIB and a number of SIBs, which are divided into minimum SI and other SI. The minimum SI comprises basic information required by the UEs for initial access and acquiring any other SI. The minimum SI itself consists of MIB which contains cell barred status information and essential physical layer information of the cell required for the UEs to receive further SI, for example, CORESET#0 configura- tion. The MIB is periodically broadcast on BCH. The minimum SI further includes SIB1 which defines the scheduling of other SIBs and contains information required for initial access. The SIB1 is also referred to as remaining minimum system information (RMSI) and is periodically broadcast on DL-SCH or sent in a dedicated manner on DL-SCH to UEs in RRC_CONNECTED state. The other SI encompasses all SIBs that are not broadcast as part of minimum SI. Those SIBs can either be periodically broadcast on DL-SCH, broad- cast on-demand on DL-SCH, that is, upon request from the UEs in RRC_IDLE or RRC_INACTIVE state or sent in a dedicated manner on DL-SCH to the UEs in RRC_CONNECTED state. The other SI is divided into the following SIBs [8]: SIB2 contains cell reselection information related to the serving cell. SIB3 contains information about the serving frequency and intra-frequency neighbor cells relevant for cell reselection, including cell reselection parameters common for a frequency as well as cell-specific reselection parameters. SIB4 contains information about other NR frequencies and inter-freque