A channel frequency with a width of 200 kHz is allocated. This method is most effective for NB-IoT, but it is also the most costly, because in this case you have to spend from 300 to 600 kHz of the width of the frequency spectrum, including guard intervals. But this method provides minimal negative impact on other communication technologies.
With this approach, the frequency range inside LTE (GSM signal) is allocated for transmitting NB-IoT packets, but the NB-IoT signal is transmitted at a higher power (6 dB) compared to the LTE signal. This reduces the cost of the frequency spectrum, but at the same time, the increased level of the NB-IoT signal affects the other channels of the network, which may be unacceptable.
This method involves the transmission of NB-IoT signal in the guard frequency range. For example, in the LTE band of 10 MHz, 500 kHz of the free frequency spectrum is used as a guard interval. In addition, NB-IoT signal is also transmitted at increased power (by 6-9 dB) in comparison with the LTE signal, in order to provide greater coverage. This method allows both to save the frequency range and reduce the influence of the NB-IoT signal on the LTE network. However, the parameters of the LTE signal transmission are deteriorating.