Underwater acoustic (UWA) communication is a fundamental technology supporting ocean exploration and observation, including the control of underwater robots, video transmission, and the development of ocean monitoring networks. However, the UWA channel suffers from severe delay and Doppler spreads. To address these issues, the author has focused on orthogonal signal division multiplexing (OSDM), which places information in the time-frequency lattice, and has explored its applicability to UWA communication. Although OSDM is equivalent to vector orthogonal frequency division multiplexing (OFDM) or orthogonal time-frequency space (OTFS), but its application in underwater acoustic communication remains limited. Since 2010, the author has been developing an OSDM-based UWA communication system and has demonstrated through experiments—from wave tanks to real-sea environments—that high-quality communication is possible even under harsh UWA channel. Additionally, the performance has been further enhanced through the integration of OSDM with MIMO signaling and sparse channel estimation techniques. This work provides an overview of the research and development history and key achievements of the author’s work on OSDM-based UWA communication.
Tadashi Ebihara (Wed,) studied this question.