EXPERIMENTATION OF OTFS PULSE DESIGN FOR UNDERWATER ACOUSTIC CHANNELS USING SDRS

This paper presents the design and experimentation of orthogonal time-frequency space (OTFS) pulse shaping for underwater acoustic communication using software-defined radios (SDRs). The objective is to adapt OTFS modulation to the underwater channel, which is severely affected by multipath propagation, Doppler spread, and signal attenuation. A Hermite-based pulse shaping approach is integrated within a GNU Radio framework to improve spectral efficiency and minimize bit error rate (BER). The experimental setup employs hydrophones to transmit and receive low-frequency acoustic signals suitable for long-range communication. Initial validation was performed using 16-QAM over RF before transitioning to underwater transmission, where chirp-based signaling provided greater reliability than single-tone excitation. The hardware platform included a USRP N210 with LFRX/LFTX daughterboards and Teledyne VP2000 preamplifiers. Results highlight the challenges of SDR configuration, the complexity of OTFS-NOMA implementation, and the critical role of synchronization in system performance. Future work will refine the modulation scheme, compare BER and SNR performance across varying conditions, and explore Hermite polynomial–based designs for enhanced robustness. This research advances underwater acoustic communication by improving adaptability and reliability in challenging propagation environments.