 Supported for Supported for Cyclic Subcarrier Cyclic Synchronization Useful Prefix Symbol Spacing Prefix (PDSCH, Blocks (PSS, SSS, Symbol Length Length symbol Af = 2H X 15 kHz PUSCH, etc.) PBCH) Length us Nslot subframe Normal 66.67 71.35 Normal 33.33 35.68 Normal/ 16.67 17.84 extended Normal Normal upper limit for the subcarrier spacing. A large subcarrier spacing would result in unwanted overhead due to CP. The maximum FFT size of the OFDM modulation along with subcar- rier spacing determines the channel bandwidth. Based on these observations, the subcarrier spacing should be as small as possible, while the system is still robust against phase noise and Doppler spread and supports the desired channel bandwidth. As shown in Table 3.12, in NR, the Primary and Secondary Synchronization Signals (PSS/SSS) and the Physical Broadcast Channel (PBCH), which are collectively known as SS block, will use 15/30 kHz SCS for sub-6 GHz and 120/240 kHz for above 6 GHz frequency bands. In the case of Physical Random-Access Channel (PRACH), the long preamble sequence utilizes 1.25/5 kHz SCS, in addition to the short preamble sequence using 15/30/60/120 kHz SCS. In other words, NR exploits a scalable OFDM subcarrier spacing (powers of 2) to support various frequency bands and deployment scenarios, where Af = 2H X 15kHz with u = {0, 1, 4} considered for PSS, SSS, and PBCH, and u = {0, 1, 2, 3} designated for other physical channels. The normal CP is supported for all subcarrier spacing values, whereas extended CP is only supported for u = 2. From the network perspective, multiplexing of dif- ferent numerologies over the same NR carrier bandwidth is possible in TDM and/or FDM manner in the downlink and uplink. From the UE perspective, multiplexing different numer- ologies is performed in TDM and/or FDM manner within or across a subframe. Regardless of the numerology used, the lengths of radio frame and subframe are always 10 and 1 ms, respectively. Different numerologies will then translate into the number of slots per sub- frame. 