ion; - gNB-CU UE F1AP ID uniquely identifies the mobile on the F1 interface. The identifier is created by the gNB-CU entity; - gNB-DU UE F1AP ID uniquely identifies the mobile on the F1 interface. The identifier is created by the gNB-DU entity; - gNB-CU UE E1AP ID uniquely identifies the mobile on the E1 interface. The identifier is created by the gNB-CU entity; - gNB-DU UE E1AP ID uniquely identifies the mobile on the E1 interface. The identifier is created by the gNB-DU entity. 2.4. References All standards can be downloaded from the ETSI website: https://www.etsi.org/ standards. 3GPP TS 29.413 Application of the NG Application Protocol (NGAP) to non-3GPP access Version 15.0.0 Release 15 3GPP TS 37.340 Universal Mobile Telecommunications System (UMTS); LTE; 5G; NR; Multi-connectivity; Overall description; Stage-2 Version 15.5.0 Release 15 NG-RAN Network - Protocol Architecture 3GPP TS 38.401 5G - NG-RAN: Architecture description; Version 15.5.0 Release 15 3GPP TS 38.410 5G - NG-RAN: NG general aspects and principles; Version 15.5.0 Release 15 3GPP TS 38.413 5G - NG-RAN: NG Application Protocol (NGAP); Version 15.5.0 Release 15 3GPP TS 38.423 5G - NG-RAN: Xn Application Protocol (XnAP); Version 15.1.0 Release 15 3GPP TS 38.470 5G - NG-RAN: F1 general aspects and principles; Version 15.7.0 Release 15 NG-RAN Network - Procedures 3.1. General procedure of the 5G-NSA mode The initial deployment of the 5G service is based on 5G-NSA option 3, also called dual EN-DC connectivity. When the phone is switched on, the mobile starts with a cell search procedure on the 4G/LTE (Long-Term Evolution) radio network. Once synchronized with the eNB (evolved Node Base station), the mobile reads the MIB (Master Information Block) system information carried by the BCCH (Broadcast Control Channel) beacon channel and the SIB (System Information Block) information carried by the PDSCH (Physical Downlink Data Channel) physical channel, in order to acquire the radio parameters of the cell. After synchronization, the mobile requests a sign