Orthogonal Time Frequency Space Modulation: Analysis in Noisy Underwater Acoustic Channels

It is prominent that underwater acoustic channel has inherently dispersive characteristics for the communication due to multipath, relative mobility of hydrophones, small-large scale fading effects, delay spread and Doppler effects. So both time and frequency selective fading are severe in the underwater acoustic channel. So reliable underwater acoustic communication (UWAC) necessitates signaling techniques that are resilient to significant Doppler shifts as an example orthogonal time frequency space (OTFS). In this work, we analyzed the OTFS modulation technique in the Bellhop-based statistical underwater channel model for the different noises namely additive white Gaussian noise (AWGN), complex noise, and real channel noise. We also compare the bit error rate (BER) performance of the OTFS based UWAC with the base technique, orthogonal frequency division multiplexing (OFDM), based UWAC system under the AWGN noise. Lastly, the simulated results show that the OTFS based underwater communication provides acceptable BER performance for the discussed three noises even with the Doppler shift approximately of 11 Hz, and from the BER comparison plot, we conclude that the OTFS scheme outmatches the underwater communication based on OFDM when it comes to the error performance and transmitter-receiver (without detection) complexity.