  This paper studies the potential of using above 71GHz frequencies for
5G-Advanced or later in 6G. More specifically, the focus is to analyze what
could be needed in terms of waveform and numerologies. The results suggest that
higher baseline subcarrier spacings (SCSs) may be needed when moving above
71GHz, to fulfill the need for higher required bandwidths and phase noise
robustness. The required SCS depends on carrier frequency and modulation order.
It is also illustrated that single-carrier waveforms, especially Known Tail
Discrete Fourier Transform Spread Orthogonal Frequency Division Multiplexing
(KT-DFT-s-OFDM) waveform is a potential candidate to be used in 5G-Advanced or
6G for sub-THz frequencies due to its robustness to phase noise, lower output
power back-off and flexible adaptation of head and tail lengths.
