After having withdrawn the resource elements allocated to the cell- specific RS physical signal, to the PCFICH and PHICH physical channels, the mobile can analyze the PDCCH physical channel. The PDCCH physical channel transports the information which facilitates the recovery of the System Information Base 1 and 2 (SIB1 and SIB2) messages contained in the PDSCH physical channel from the detection of the system information radio network temporary identifier (SI-RNTI). The SIB1 message provides the following information: - the bandwidth of the radio channel, for the uplink; - the configuration of the type-2 time frame; - the scheduling of the other SIB system information. The SIB2 message provides the information related to the configuration of radio resources allocated to the PRACH physical channel. 4.2.1.2. Random access The random access procedure is initialized by the mobile and is required by the following cases: - when establishing the connection to the eNB entity; - when changing the cell during the session (handover); Radio Interface Procedures - when updating timing advance (TA); - when re-establishing the connection to the eNB entity. The random access procedure is said to be with contention when the mobile chooses the used resource (PRACH channel, preamble) randomly. This occurs for the establishment or re-establishment phases of the connection. 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 happens for the handover or the updating of the timing advance TA. 4.2.1.2.1. Random access with contention The random access procedure with contention, during the establishment or re-establishment of the connection to the eNB entity is described in Figure 4.9. PRACH (preamble) PRACH (preamble) PRACH (preamble) PDCCH (RA-RNTI) PDSCH / MAC RAR (TA, UL Grant ,TC-RNTI) PUSCH / MAC / RRC ConnectionRequest PDCCH (TC-RNTI) PDSCH / MAC (CRI) / RRC ConnectionSetup PUSCH/ MAC (C-RNTI) / RRC ConnectionSetupComplete Figure 4.9. Random acce