s response SO that the UE can detect whether a random access response for the used preamble exists. In step 3, the UE will send an RRC CONNECTION REQUEST message on the uplink common control channel, Guard Preamble Sequence FIGURE 9-79 Random access preamble structure Table 9-26 Random Access Parameters [107] Preamble Format (~100 us) 3168Ts (~800 us) 24576Ts (~680 us) 21024Ts (~800 us) 24576Ts (~200 us) 6240Ts (~1600 us) 245762Ts (~680 us) 21024Ts (~1600 us) 245762Ts 4 (frame structure type 2) (~15 us) 448Ts (~130 us) 4096Ts 9.15 3GPP LTE physical layer protocols based on the uplink grant received in the previous step. In step 4, the eNB sends back a MAC PDU containing the uplink CCCH service data unit that was received in step 3. The message is sent on the downlink shared channel and addressed to the UE via the temporary identifier C-RNTI. When the received message matches the one sent in step 3, the contention resolution is considered successful; [30,109] otherwise the procedure is restarted at step 1. Paging is used for setting up network-initiated connection. A power-saving and efficient paging procedure should allow the UE to sleep without having to process any information and only to briefly wake up at predefined intervals to monitor paging information (as part of control signaling in the beginning of each subframe) from the network [30,109]. 9.15.10 Cell Search Cell search is a procedure performed by a UE to acquire timing and frequency synchronization with a cell and to detect the cell ID of that cell. 3GPP LTE uses a hierarchical cell search scheme similar to WCDMA. E-UTRA cell search is based on successful acquisition of the following downlink signals: (1) the primary and secondary synchronization signals that are transmitted twice per radio frame; and (2) the downlink reference signals based on the broadcast channel that carries system information such as system bandwidth, number of transmit antennas, and system frame number. The 504 available physical layer cell identities are grouped into 168 physic