A Comparison of the Multicarrier Modulations in Underwater Acoustic Channels

Recently, several new Multicarrier Modulation (MCM) techniques have been developed for next-generation wireless communications, particularly in high-mobility environments. Among these, Orthogonal Time Frequency Space (OTFS), Orthogonal Time Sequence Multiplexing (OTSM), Affine Frequency Division Multiplexing (AFDM), and Orthogonal Chirp Division Multiplexing (OCDM) have gained significant attention due to their excellent performance in time-varying and doubly spread channels. Underwater acoustic (UWA) channel is considered as one of the most challenging communication channels due to its strong time-varying and doubly-spread effect, which motivates the application of these MCM techniques to UWA communications. However, performance comparison of these techniques in the context of UWA channels remains scarce. In this paper, we compare the performance of AFDM, OCDM, OTFS, OTSM, and OFDM over both real and generated UWA channels. The results show that OFDM experiences significant performance degradation in both real and generated UWA channels. When parameters are properly adjusted, AFDM outperforms OCDM in terms of Bit Error Rate (BER), while OTFS and OTSM achieve the lowest BER.