Orthogonal chirp-based frequency division multiplexing for short transmission time interval underwater communications

This paper proposes an orthogonal chirp-based frequency division multiplexing (OCFDM) for a short transmission time interval (sTTI) in underwater acoustic (UWA) communications. The proposed OCFDM replaces the tone signal basis of the conventional orthogonal frequency division multiplexing (OFDM) with a linear chirp basis. The proposed method reduces packet length by replacing an outer preamble for time synchronization and differential detection with an inner preamble. Through computer simulations and ocean experiments, the proposed method demonstrates superior throughput performances, validating the feasibility of sTTI in UWA communications. • Proposes orthogonal chirp-based OCFDM to reduce packet length and improve UWA communication for UUVs with short sTTI. • OCFDM replaces OFDM tones with chirps, enhancing time synchronization and channel estimation without extra preambles. • Maintains chirp orthogonality, improving robustness against Doppler effects and frequency-selective fading in UWA channels. • Simulations and ocean tests show OCFDM achieves superior BER and throughput compared to OFDM and OCDM methods. • Real ocean experiments confirm OCFDM as a promising solution for low-latency underwater communications.