Underwater Acoustic Communication With an Orthogonal Signal Division Multiplexing Scheme in Doubly Spread Channels

Underwater acoustic (UWA) communication is an ongoing challenge because of the heavy time spread by multipath and Doppler spreads. In this paper, we propose a UWA communication system using orthogonal signal-division multiplexing (OSDM), a scheme that measures the multipath profile without an adaptation or interpolation process, to achieve stable communication in doubly spread channels. We previously evaluated the performance of an OSDM scheme in a UWA communication system in both an experiment and simulations. In the present study, we experimentally compared the performance of OSDM and existing communication schemes - single-carrier with decision feedback equalizer (DFE) and orthogonal frequency-division multiplexing (OFDM)-in a test tank with respect to communication quality, data rate, frame length, and calculation complexity. We found that OSDM with a multichannel receiver is attractive in terms of communication quality; it achieved a far better bit error rate (BER) performance compared to the other schemes in both static and dynamic channels with various input signal-to-noise ratios, although the complexity is less than that achieved with single-carrier DFE. Based on these findings, we suggest that OSDM can provide a highly reliable communication environment for UWA communication with multipath and Doppler spread, such as in shallow water.