 another option with 3.75 kHz subcarrier spacing in the uplink. The target of 3.75 kHz option is to further enhance the coverage. NB-IoT uplink has two further options: Single tone transmission, which is mandatory for NB-IoT UE. A single subcarrier of 15 or 3.75 kHz is used. The slot duration is 0.5 or 2 ms. See Figure 14.7. Multi-tone transmission, which is optional for NB-IoT UE. The number of subcarriers is 3, 6, or 12, and the subcarrier spacing is 15 kHz. The slot duration is 0.5 ms. Common channels on an LTE carrier have a transmission bandwidth of 1.4 MHz. Those channels cannot be utilized by NB-IoT with only 200 kHz RF bandwidth. There- fore, new physical channels will be required by NB-IoT, including Narrowband Primary and Secondary Synchronization Signals (NPSS/NSSS), Narrowband Reference Signals (NRSs), and Narrowband Physical Broadcast Channel (NPBCH). The new physical sig- nals and channels are listed in Figure 14.8, and the common control locations within 1 PRB are shown in Figure 14.9. The common control channels take 5 subframes out of 20. The NPBCH is based on the LTE Physical Broadcast Channel (PBCH) with a transmis- sion every 10 ms in subframe #0. The NPBCH consists of eight independently decodable blocks spanning 80 ms. The NPDCCH is based on the LTE PDCCH with a maximum aggregation level of 2 and repetitions for enhanced coverage. Three new DCI formats are 14.4 Narrowband-loT Figure 14.8 New physical signals and channels Synchronization NPSS/NSSS for NB-loT. Reference signals Downlink Broadcast NPBCH Dedicated control NPDCCH Dedicated data NPDSCH Random access NPRACH Uplink Dedicated data NPUSCH NPBCH NPBCH 1 PRB 20 ms Figure 14.9 Physical channel locations. Normal Robust Extreme Match GPRS GPRS + 10 dB GPRS + 20 dB Path loss High RSRP Low RSRP Very low RSRP Figure 14.10 Coverage extension levels. defined to support NB-IoT. The NPDSCH is based on the LTE PDSCH with one trans- port block that may be mapped to 1-10 subframes. The maximum NPDSCH transport block size is 680 bits. Single-process 