respectively. Selection of the number of subcarriers for a resource unit can be 1, 3, 6, or 12 to support both single- tone and multitone transmission. The narrowband downlink physical resource block has 12 subcarriers with 15 kHz spacing, providing 180 kHz transmission bandwidth (see Fig. 6.26). It only supports a QPSK modulation scheme. To facilitate low-complexity decoding for downlink transmission in devices, the turbo coding was traded off with TBCC. NB-IoT achieves an MCL 20 dB higher than LTE. Coverage extension is achieved by increasing the reliability of data transmission through increasing the number of repetitions. Internet of Things NB-loT UL Spectrum mask 180 kHz Spectrum mask 878.8 879.28 879.76 880.24 880.72 881.2 Frequency (MHz) Figure 6.26 Example of NB-loT NPUSCH transmission spectrum with 15 kHz subcarrier spacing [16,17]. Coverage enhancement is ensured also by introducing single-tone NPUSCH transmission and /2 - BPSK modulation to maintain close to 0 dB PAPR, thereby reducing the unreal- ized coverage potential due to PA backoff. The single-tone NPUSCH transmission with 15 kHz subcarrier spacing provides a layer-1 data rate of approximately 20 bps when con- figured with the highest repetition factor, that is, 128, and the lowest modulation and coding scheme. The NPDSCH can provide a layer-1 data rate of 35 bps when configured with repe- tition factor 512 and the lowest modulation and coding scheme. These configurations sup- port close to 170 dB coupling loss. In comparison, the LTE network is designed for approximately 142 dB coupling loss. Fig. 6.27 shows an example of NPUSCH format 1 and 2 signal processing stages in order to achieve 144, 154, and 164 dB MCL in the uplink. The information bits can be mapped to NPUSCH format 1 based on LTE uplink SC-FDMA waveform. Furthermore, it depicts the processing stages for achieving 164 dB MCL based on NPUSCH format 2. In the latter case, following the use of /2 BPSK modulation, there are 3840 symbols which are repeated six times, appended with cyclic