es in an optimal way, and in some cases cannot even serve them at all; therefore, different parameterizations are needed to cover different operational scenarios. The use of 15 kHz spacing provides the largest cyclic prefix, which may be necessary in large cells in low frequency bands. Another aspect of the subcarrier spacing selection to consider is the maximum band- width that can be used. As shown in Table 6.1, 15 kHz subcarrier spacing supports up to 50 MHz carrier bandwidths (as effectively some guard band left unused); in the same way, 30 kHz subcarrier spacing allows for bands with up to 100 MHz carrier bandwidth. 6.2 5G Multiple Access Principle V = 30 km/h SC spacing = 15 kHz SC spacing = 30 kHz SC spacing = 75 kHz SC spacing = 150 kHz SC spacing = 540 kHz Carrier frequency (GHz) Figure 6.3 Impact of carrier frequency on phase noise. The actual occupied bandwidth is now somewhat more than in LTE (though not in all cases), as shown in Table 6.2. The 5G numerology allows an implementation with 4k FFT size to keep the complexity to a reasonable level. The LTE channel occupancy was con- stant at 90%, while with 5G it varies depending on the bandwidth and subcarrier spacing in question. In some cases, the channel occupancy is approximately 95%, while in other cases it becomes worse than in LTE. As can be seen from Table 6.2, the use of 60 kHz subcarrier spacing with low bands would decrease the channel occupancy efficiency. The UE capabilities, as discussed in later in this chapter, leave support for 60 kHz subcarrier spacing as an optional feature and thus something not foreseen as being supported in the first-phase UE implementations, when there is no obvious need for that. For the higher frequency bands, LTE, of course, is not relevant as a reference as LTE cannot be operated there. For the 26 and 28 GHz ranges, it is possible to operate up to 400 MHz bandwidth, while 200 MHz is the minimum requirement for Release 15 UEs. Thus, for example, an allocation of 800 MHz would need to be operated with 200 MHz ca