equest message, thereby resolving the collision. The mobile retrieves the DCI message with the TC-RNTI identifier and reads the description of the data in the physical PDSCH channel. After collision resolution, the temporary TC-RNTI identifier becomes the definitive C-RNTI identifier assigned to the mobile. For others, the msg4 response NG-RAN and 5G-NR waits until the timer expires. A new access request will then be renewed within the limits of the requests authorized in the SIB2 message. The aim of the beam management procedure is to pair a beam emitted by a set of TRxP transmission points with a beam from the mobile. The beam management procedure is carried out in four steps: - beam sweeping; - measurement of the power level of the beams; - determination of the beam; - the beam measurement report. In the case of initial access, the choice of beam is based on the reference signals of the SSB block (SSS, PSS and PBCH DMRS). When the mobile is in the RRC_CONNECTED state, the reference signals CSI-RS (DL) and the SRS (UL) are used to pair the beams. sweeping Synchronization signal -SSB sweeping Msg 1 PRACH - Preamble (best beam) UE choose the best Specific Msg 2 : PDCCH (RA-RNTI) PDSCH / MAC RAR (TA, UL Grant, TC-RNTI, RAPID) Msg 3 : PUSCH / MAC RRC SetupRequest Msg 4 : PDCCH / MAC RRC Setup Figure 3.7. Access radio procedure and beam management. For a color version of this figure, see www.iste.co.uk/launay/5g.zip 3.2.2. Establishment of radio connection Like the 4G network, following the random access procedure, the mobile requests the establishment of an RRC connection by sending the RRC SetupRequest. The purpose of this request is to inform the base station of the reason for its RRC connection request and to transmit its identifier (ng-5G-TMSI or a random value). NG-RAN Network - Procedures The RRC connection establishment can occur due to: - an exchange of signaling requests to the core network (MO signaling); - an emergency call request; - a non-priority IoT transmission request (delay tolerant); - a response