which is necessary for trans- mission over the NPUSCH. Further, the RAR message provides the uplink grant for msg3, containing all relevant data for msg3 transmission. The remaining procedure is performed similar to LTE; that is, the UE sends an identification and upon reception of the contention resolution message, indicating successful completion of the random-access procedure. The network can configure up to three NPRACH resource configurations in a cell in order to serve UEs in different coverage scenarios (based on the measured path loss). In each con- figuration, a repetition value is specified to increase the reliability of random-access pream- ble transmission. The UE measures the downlink received signal strength to estimate its coverage level, and transmits a random-access preamble in the NPRACH resources 780 Chapter 6 configured for that coverage level. To facilitate NB-IoT deployment in different scenarios, NB-IoT allows flexible configuration of NPRACH resources in time-frequency resource grid with the following parameters: (1) periodicity of NPRACH resource and starting time of NPRACH resource; (2) subcarrier offset (location in frequency) and number of subcar- riers (see Fig. 6.23). The UE should indicate its support of single-tone/multi-tone transmis- sion in the first step of random-access procedure in order to facilitate the network's scheduling of uplink transmission in the third step. The network can partition the NPRACH subcarriers in the frequency domain into two non-overlapping sets. A UE can select one of the two sets to transmit its random-access preamble to signal its supports for multi-tone transmission in the third step of random-access procedure. As we mentioned earlier, a set of PRACH resources (e.g., time, frequency, and preamble sequences) is provided for each coverage level. The PRACH resources per coverage level are configurable by the system information. The UE selects PRACH resources based on the coverage level estimated using downlink signal measurements, for example, RSRP [5]