RAR message MSG 2 inprach-NumCBRA-StartSubcarriers Number of starting sub-carriers allocated to contention based NPRACH response NPDCCH+NPDSCH random access numRepetitionsPerPreambleAttempt Number of NPRACH repetitions per attempt RRC connection Inprach-StartTime NPRACH starting time MSG 3 request (scheduled MSG 3 inprach-SubcarrierMSG3-RangeStart Fraction for calculating starting subcarrier index for the range of NPRACH NPUSCH transmission) subcarriers reserved for indication of UE support for multi-tone msg3 transmission RRC connection setup (contention MSG 4 MSG 4 resolution) NPDCCH+NPDSCH RRC connection NPUSCH setup complete Figure 6.23 NB-loT RACH procedure (these messages are repeated according to the UE coverage enhancement level) [6]. to the network using the scheduled resources; and (4) the network transmits a contention resolution message to resolve any contention due to multiple UEs transmitting the same random-access preamble in the first step. More specifically, upon transmission of the pre- amble, the UE first calculates its RA-RNTI from the transmission time. It then looks for a PDCCH with the DCI format N1 scrambled with the expected RA-RNTI, in which the RAR message is signaled. The UE expects this message within the response window, which starts three subframes after the last preamble subframe and has a coverage enhancement depen- dent length given in SIB2-NB. If the preamble transmission was not successful, that is, the associated RAR message was not received, the UE transmits another RACH preamble. This process is repeated up to a maximum number, which depends on the coverage enhancement level. For the case that this maximum number is reached without success, the UE proceeds to the next coverage enhancement level, if this level is configured. If the total number of access attempts is reached, an associated failure is reported to the RRC sublayer. With the RAR message, the UE receives a temporary C-RNTI and the timing advance command. Consequently, the forthcoming msg3 is already time aligned, 