shment or reestablishment. The random access procedure is said to be without contention when the eNB entity is providing the resource to be used to the mobile. This occurs for the handover or for the updating of the timing advance or for dual connectivity. 3.1.2.1. Random access with contention The random access procedure with contention, during the establishment or reestablishment of the eNB entity connection, is described in Figure 3.1: 1) The mobile transmits the preamble in the PRACH physical channel; this preamble is randomly chosen in a list communicated by the eNB entity in the SIB2 system information. NG-RAN Network - Procedures Without the response of the eNB, the mobile retransmits the preamble and increases the transmission power. The maximum number of retransmission is limited by SIB2 information or by the RRC ConnectionReconfiguration message. The risk of contention increases with the number of mobiles that try to access the same PRACH physical channel. 2) When the eNB entity receives the PRACH physical channel, it calculates the timing advance and transmits it to the mobile with the following information: - the Downlink Control Information (DCI) in the PDCCH physical channel, in format 1A or 1C scrambled with RA-RNTI identity; - the Random Access Response (MAC RAR) frame containing the index of the preamble, the timing advance, the resource to use (UL Grant) for the transmission in the Physical Uplink Shared Channel (PUSCH) and the Temporary Cell RNTI (TC-RNTI) in the PDSCH physical channel. This identity is temporary because in case of contention, several mobiles may assume that this identity is allocated to them, thereby leading to contention. The RA-RNTI identity is calculated as follows: - RA - RNTI=1+t_id+10*f_id; - t _id is the index of the first subframe used by the PRACH physical channel 0<t_id<9); - f_id is the index of the PRACH physical channel, in the frequency domain (0< f_id<6). 3) The mobile initializes its timing advance and responds with the RRC ConnectionRequest message containing: