ess radio network temporary identifier (RA-RNTI). The RA-RNTI is defined by the selected subframe (within the radio frame) of PRACH resource and by the selected PRACH frequency resource. For FD LTE, there are only the time domain resources and therefore the subframe or subframes for PRACH directly define the RA-RNTI [1]. In case the UE does not receive the random access response within a specified window starting 3TTIs from the sent preamble and ending random access response window size + 4TTIs later, the UE will re-initiate the RACH procedure from the beginning (selects randomly the preamble from available preamble groups) with preamble transmission counter incremented by one per each sent preamble. Therefore, each time the random access procedure needs to be repeated the preamble is sent with higher power level, incremented as can be seen from Eq. 12.1. The random access response window size is defined by the eNodeB parameter database and sent to the UE within system information block 2. The repetition of random access procedure is done by the UE until expiry of T300. Timer T300 supervises the RRC connection establishment procedure and is stopped at the reception of RRC Connection Setup or RRC Connection Reject message. Also cell reselec- tion or abortion of RRC connection establishment from higher layers can cause stopping of T300. In case T300 is running, the UE can continue to send random access preambles and PREAMBLE_TRANSMISSION_COUNTER = preambleTransM + 1 does not necessarily stop the preamble transmissions. Setting the T300 too short may result in better statistics in terms of random access setup success rate, but poor accessibility from end-user point of view due to users under poor radio conditions might not have enough power ramp-ups to compensate the large coverage area (especially in case of varying interference conditions). Therefore, the RACH procedure parameter tuning results should be always verified by drive testing to detect possible problems where the UE transmission power does not reach the