entity becomes the C-RNTI, the definitive identity allocated to mobile. Radio Interface Procedures The mobile indicates its C-RNTI in the control element of the MAC frame and confirms the connection through the RRC ConnectionSetupComplete message. 4.2.1.2.2. Random access without contention The random access procedure without contention, when changing the cell during the session, is described in Figure 4.10. During the procedure of handover based on the X2 interface, the target eNB entity provides the characteristics of the radio interface to the source eNB entity in a message X2-AP HANDOVER REQUEST ACK. This message contains the information element handover command which specifies the preamble that the mobile must use during the random access procedure to the target eNB entity. The source eNB entity forwards the information element handover command in the RRC Connection Reconfiguration message which triggers the handover for the mobile. Source Target RRC ConnectionReconfiguration X2-AP HANDOVER REQUEST ACK (preamble) (preamble) PRACH (preamble) PRACH (preamble) PRACH (preamble) PDCCH (RA-RNTI) PDSCH / MAC RAR (TA, UL Grant ,TC-RNTI) PUSCH / RRC ConnectionReconfigurationComplete Figure 4.10. Random access without contention in case of changing the cell during the session The random access procedure comprises as before the preamble transmission by the mobile and the MAC RAR frame by the eNB entity. VoLTE and ViLTE The mobile connection is finalized when the mobile transmits the RRC Connection Reconfiguration Complete message. 4.2.2. Data transfer 4.2.2.1. Scheduling Data scheduling is the operation carried out by the eNB entity which consists of providing resource blocks (RB) to the mobiles and in controlling transmission power, for the downlink and the uplink direction. In the time domain, the allocation of the resources corresponds to a sub- frame of a TTI (Transmission Time Interval) duration of a millisecond, which represents two resource blocks (RB). In the frequency domain, the eNB entity can give the mobile