ation process is the way the UE gains access to the network. It is the way the UE and the network mutually authenticate each other, and the network authorizes the UE to use the network resources according to its subscription or mobile plan: 5G SA network design fundamentals UE Performs Registration: RRC Setup (1 of 5) AMPCF Random Access Preamble Random Access Response Random Access Procedure RRC Connection Request RRC Connection Setup RRC Connection Complete RRC Connection Setup Procedure AS: Request Slice-ID NAS: Registration Request (SUCI, Request Slice-ID) UE Policy Status 9-10 digits MSIN: Mobile Subscriber Identification Number 01001100 nonce 1-4 digits Route ID SUCI: SUbscription Concealed Identity Figure 11.4 - UE registration - part 1 Let us go over each step one by one: The UE sends the Random Access Preamble to the gNB. This preamble is referenced with the help of a Random Access Preamble ID. This preamble is derived from a Zadoff-Chu sequence. The gNB sends a Random Access Response to the UE with an assigned temporary C-RNTI value. Then, the UE sends an RRC Connection Request Message to the gNB, which contains the UE identity and the establishment cause. The gNB responds with an RRC connection setup, which is sent to signaling radio bearer1 (SRB1). The message contains the radio bearer configuration and master cell group information elements. The UE sends an RRC Connection Setup Complete dedicated NAS message stating registration request to the gNB, which is intended to be sent to the AMF. 5G Standalone Networks UE Performs Registration: Authentication (2 of 5) AM PCF gNB Selects AMF Initial UE Message NAS: Registration Request (SUCI, Request Slice-ID) UE Policy Status AuSF Selection Authentication Request (SUCI, VPLMN ID) Authentication Request (SUCI, VPLMN ID) Deconceal SUCI, Select Auth Mech Authentication Response (SUPI, R, AUTN, KAUSF' XRES*) Authentication Response (SUPI, R, AUTN, HXRES*) KSEAF KDF2 (K AUSF' VPLMN,) DL NAS Transport HXRES* = SHA-256 (R Il XRES*) NAS: Registration Request (R, AUT