nment [3]. Therefore, the current cellular systems have limited parameter sets that are defined in the standards. Figure 7.4 illustrates the waveform parameter options in 5G NR [25]. Numerologies change mainly with the subcarrier spacing parameter in 5G NR. CP ratio is fixed and CP durations depend on the subcarrier spacings. However, there are normal and extended CP versions as an exception for 60 kHz subcarrier spacing. Extended CP usage is not available for the other subcarrier spacings. Subcarrier spacings of 15, 30, and 60 kHz are used up to 6 GHz spectrum. The 60 and 120 kHz subcarrier spacings are preferred for above 6 GHz. For 52.6 GHz and beyond, there may be larger subcarrier spacings [41]. In [5], different pulse shapes are compared to each other. 5G NR provides options for rectangular and raised-cosine windowing. There is a flexibility to apply windowing with different or same roll-off factors on the subframes for each numerology or composite signal of multiple numerologies at the transmitter. Receiver windowing is the other option for 5G NR. Filtering is also possible in addition to windowing. Inter-numerology guard band utilization aims to decrease the INI effects rather than changing the pulse shape as in windowing and filtering. All of them can be called as wave- form processing techniques but inter-numerology guard bands are utilized while design- ing the frame structure. As discussed in Section 7.1, multiple numerologies are related with the lattice structure, applying window and filter are related with the pulse shape, and inter-numerology guard band is related with the frame structure. Guard band utilization can be in a fixed or adaptive manner. For example, some of the subcarriers that are not affected by INI in the guard bands are used for data communications in [42]. It is possi- ble to develop different types of adaptive guard band utilization methods. Additionally, the 5G numerology Optional waveform structures processing techniques Subcarrier spacing CP duration (us) Slot duration (ms) N