Assessing the Efficiency of Multi-Carrier Waveforms in Next-Generation 6G Wireless Communication Systems

Envisaged as the future of wireless communication systems, the next generation of technology beyond 5G/6G will be required to handle high-mobility scenarios. However, traditional multicarrier waveforms such as orthogonal frequency division multiplexing (OFDM) may not perform well due to the loss of orthogonality between subcarriers induced by severe Doppler frequency shifts. To address this issue, various emerging waveforms have been proposed to enhance performance in high-mobility scenarios. This paper focuses on the three most promising candidates: (1) orthogonal time frequency space (OTFS) modulation, which is a 2D modulation technique designed in the delay-Doppler domain; (2) Orthogonal time sequency multiplexing (OTSM) is a modulation scheme that utilizes a single-carrier approach to transmit information symbols by arranging them in the delay-sequency domain, followed by a series of time-division multiplexing (TDM) and Walsh-Hadamard sequence multiplexing.; and (3) Orthogonal chirp division multiplexing (OCDM) is a recently developed multicarrier modulation scheme that utilizes chirp spread spectrum (CSS) as its foundation. OCDM has been demonstrated to exhibit enhanced robustness against interference arising from insufficient guard intervals. This paper presents a comprehensive overview of these candidate waveforms techniques, analyzes their performance over doubly dispersive channels, and demonstrates that they outperform OFDM over fast time-varying channels. Finally, we provide suggestions for candidate waveforms.