receiving gNB triggers the XnAP retrieve UE context procedure to obtain the UE con- text from the last serving gNB and may decide to move the UE back to RRC_INACTIVE state, RRC_CONNECTED state, or RRC_IDLE state. In case of peri- odic RNA update, if the last serving gNB decides not to relocate the UE context, it fails the retrieve UE context procedure and directly moves the UE back to RRC_INACTIVE state or to RRC_IDLE state by an encapsulated RRCRelease message. Table 2.3 provides the functional split between the UE NAS and AS procedures in RRC_IDLE and RRC_INACTIVE states. The UE may use DRX in RRC_IDLE and RRC_INACTIVE states in order to reduce power consumption. The UE monitors one paging occasion (PO) per DRX cycle. A PO is a set of Table 2.3: Functional split between access stratum and non-access stratum in RRC IDLE and RRC_INACTIVE states [12]. RRC_IDLE and UE Non-access Stratum UE Access Stratum RRC_INACTIVE State Procedure PLMN selection Maintain a prioritized list of PLMNs Search for available PLMNs, if the associated RAT(s) are Select a PLMN using automatic or manual mode set for the PLMN, search among those RAT(s) Request AS to select a cell belonging to this PLMN. For Perform measurements to support PLMN selection each PLMN, associated RAT(s) may be set Synchronize to a broadcast channel to identify PLMNs Evaluate reports of available PLMNs from AS for PLMN Report available PLMNs with the associated RAT(s) to selection NAS on request from NAS or autonomously Maintain a list of equivalent PLMN identities Cell selection Control cell selection by indicating RAT(s) associated Perform the required measurements to support cell with the selected PLMN to be used initially in the search selection of a cell in the cell selection process Detect and synchronize to a broadcast channel Maintain a list of forbidden tracking areas and provide the Receive and process broadcast information list to AS Forward NAS system information to NAS Search for a suitable cell. The cells broadcast one or more PLMN identity in the s