Performance Comparison of OFDM and DFT-s-OFDM in the THz-Band Communications Channels

The terahertz (THz) band is a promising frequency band that ranges from 0.3 THz to 10 THz and being considered for the next generation 6G wireless networks due to the large available bandwidth and potentially ultra fast data rates. THz channels and systems are unique in three aspects: 1) high path loss; 2) rich scattering from rough surfaces; 3) severe phase noise from local oscillators. These pose questions on what physical waveforms should be used in THz channels. Since orthogonal frequency division multiplexing (OFDM) and discrete Fourier transform spread OFDM (DFT-s-OFDM) are adopted waveforms in 5G new radio (NR) and 4G, their possible use in the future generation wireless networks is an open question. In this paper, we first review a THz channel model for accurate representation of THz channels. Then uncoded and coded OFDM and DFT-s-OFDM systems are investigated for their performance in THz channels, demonstrating their unique behaviors in these channels. The impact of phase noise is also examined, and a non-iterative compensation method slightly modified from the literature is used to mitigate the phase noise effect. DFT-s-OFDM shows advantages over OFDM in the studied THz environment. The simulation results in this paper can be used as a benchmark for future studies.