GPP Release 14 introduced enhancements to Cat-M including a new Cat-M2 UE category supporting higher data rates, multi-cast support using single-cell point-to-multipoint transmission, and enhancements for positioning. 14.4 Narrowband-loT NB-IoT takes the cost optimization even further than Cat-M. It is also known as Cat-NB. While LTE-M supports 1.4 MHz, NB-IoT only needs to support 200 kHz, which leads to a simpler implementation, even better coverage, and a lower data rate. NB-IoT is still designed to be deployed together with LTE. There are three options regarding how NB-IoT can be used with LTE. The in-band option has the NB-IoT carrier located within the LTE carrier. Most of the first NB-IoT deployments are based on the in-band option. Guard band options place the NB-IoT carrier just next to the LTE carrier within the guard band. Note that 10% of the LTE channel spacing is reserved for guard bands. 10 MHz LTE has a total of 1 MHz allocated for guard bands. The guard band option is the target deployment for many NB-IoT cases because it gives NB-IoT capability with- out sacrificing any existing LTE spectrum. The standalone option is used for those cases where NB-IoT is deployed together with GSM or WCDMA without any LTE carrier on the same spectrum. NB-IoT can replace one GSM carrier because both have 200 kHz bandwidth. NB-IoT can be deployed at the edge of the WCDMA carrier because the WCDMA transmission bandwidth is 3.84 MHz, while the typical channel spacing is 5 MHz. The deployment options are shown in Figure 14.6. 14 Internet of Things Optimization Standalone Standalone In-band Guard band with GSM with 3G nummer - 000000 GSM carriers LTE carrier LTE carrier 3G carrier Figure 14.6 NB-loT deployment options. Subcarrier Subcarrier spacing 15 kHz spacing 3.75 kHz Frequency domain 180 kHz 180 kHz 12 subcarriers 48 subcarriers domain 1 slot, 7 symbols 1 slot, 7 symbols 0.5 ms Figure 14.7 Uplink subcarrier spacings (SCSs) and frame structure. NB-IoT allows the normal LTE subcarrier spacing of 15 kHz to be used or