Abstract
The extreme and uncertain underwater environment presents significant challenges for achieving reliable acoustic communications, mainly due to limited bandwidth and time-varying channels. To address these challenges, this work proposes a novel multiple-access technique called Orthogonal Signal Division Multiple Access (OSDMA). OSDMA enables the simultaneous transmissions of different data streams from a single transmitter to corresponding receivers/users by modulating the streams with an orthogonal Inverse Discrete Fourier Transform (IDFT) matrix. In a low-noise environment, each receiver/user can accurately estimate the channel and demodulate the data. Emulations and simulations are conducted based on collected at-sea channel state information. The results demonstrate that OSDMA offers higher robustness against underwater time-varying channels than traditional Orthogonal Frequency Division Multiple Access (OFDMA).