le of the different cyclic prefix lengths and OFDM symbol lengths for all the supported subcarrier spacings. The lengths are indicated assuming a 4K FFT, as was mentioned previously. Waveform, numerology, and frame structure 1 OFDM symbol = 71.35 US (incl CP 4.69 us) 15 kHz low band 14 OFDM symbols = 1 slot = 1000 US 1 OFDM symbol = 35.68 US (incl CP 2.34 us) 30 kHz mid-band 14 OFDM symbols = 1 slot = 500 US Normal CP, 14 OFDM symbols per slot, 60 kHz 1 OFDM symbol = 17.74 US (incl CP 1.17 us) normal/ extended CP ECP, 12 OFDM symbols per slot, 1 OFDM symbol = 20.83 US (incl CP 4.17 us) 1 slot = 250 US 1 OFDM symbol = 8.92 US (incl CP 0.59 us) 120 kHz 14 OFDM symbols = 1 slot = 125 US Figure 4.14 - An illustration of numerologies There are some basic rules for numerology. The slot length is 1 millisecond in 15 kHz. Note that 15 kHz carrier spacing is the same as LTE for normal CP. This is to support LTE-NR coexistence in the same radio frequency. As the subcarrier spacing increases, the slot duration halves. We always have 14 OFDM symbols in a slot regardless of the slot duration. There is an exception in 60 kHz subcarrier spacing with an extended cyclic prefix. As you can see from the preceding diagram, when the extended cyclic prefix is utilized, the OFDM symbols drop to 12. All these rules guarantee OFDM symbol alignment between the different numerologies, which will make multiplexing of different subcarrier spacing both in time and frequency much easier. Numerology - delay and cell size Frequency is one factor to consider when choosing numerology. A frequency's phase noise determines the minimum subcarrier spacing. The phase noise rises in the high-frequency bands. Therefore, larger subcarrier spacing is required to compensate for the increased phase noise. 5G Air Interface and Physical Layer Procedures - Part 1 cell size large 15 kHz 15 kHz medium 30 kHz 30 kHz 15 kHz 30 kHz small 30 kHz 60 kHz 60 kHz 60 kHz frequency medium Figure 4.15 - Numerology and cell size For a given frequency, the required cyclic pre