erving cell: 1) The mobile sends its random access request by transmitting a preamble. Once the preamble has been sent, the terminal UE listens to the response of the base station between the instant t1 and t2=t1+ Window_reception (timer T300). The RA-RNTI identity is calculated as follows: - -1+s_id+14*t_id+14*80*f_id+14*80*8*ul_carrier_id; - - s_id is the index of the first OFDM symbol (1<s_id<14) of the PRACH channel; NG-RAN Network - Procedures - t_id is the index of the first slot of the PRACH channel (0<t_id<80) in the frame; - f id is the index of the PRACH physical channel in the frequency domain (0< fid<8); - ul carrier id is the subcarrier index that carries the preamble. 2) When the radio node receives the PRACH physical channel, it calculates the timing advanced (TA) and transmits the MAC RAR (Random Access Response) response to the mobile (message 2), allocating the radio resources to it for the next uplink message (UL Grant) and giving a temporary identity TC-RNTI (Temporary Cell RNTI). The gNB broadcasts the response on the PDCCH Channel. All of the mobiles received the response, but the CRC of the DCI message is scrambled by the RA-RNTI identifier: - the mobile retrieves the DCI information from the RA-RNTI identifier; - the mobile checks whether the preamble RAPID identifier (Random Access Preamble IDentifier) transmitted by the gNB entity corresponds to the preamble initially chosen by the mobile; - the mobile retrieves the description of its data in the physical PDSCH channel from the DCI information. In message 3, the mobile sends an RRC ConnectionRequest with a UE identifier. This identifier allows the gNB base station to resolve conflicts. When the gNB entity receives the RRC SetupRequest message, it responds to the mobile with the RRC Setup (message 4) comprising: - DCI information (Downlink Control Information) in the physical PDCCH channel; - the MAC RAR header containing the UE CRI (Contention Resolution Identity) control element. This control element replicates the identity of the RRC R