Abstract
Recently, the orthogonal time-frequency space (OTFS) modulation technique has been proposed to provide reliable communication over time-varying channels, combined with the double dispersion characteristics of underwater acoustic channels to improve the BER performance and spectral efficiency of underwater acoustic communication. In this paper, we propose an underwater acoustic communication system combining index modulation with OTFS. This technique uses indexed bits to control the activation of the grid in the delay-Doppler domain, allowing flexible adjustment of the number of silent and activated grids, resulting in a system with better transmission performance. The effectiveness of the method is demonstrated through simulations where the modified scheme obtains better BER performance than the conventional OFDM-IM modulated underwater acoustic communication system.