Non-Coherent Underwater Acoustic Space Modulation System Based on Time Difference of Arrival

A novel non-coherent acoustic underwater multiple-input multiple-output (MIMO) communication system is proposed and analyzed in this article. The proposed system uses space modulation techniques and relies on the time difference of arrival (TDOA) to determine active transmitters. In particular, at each symbol time, only one transmitter is active and transmits an unmodulated data towards the receiver. Via TDOA, the receiver localizes active transmitter and retrieve corresponding data bits. It is revealed in this study that leveraging TDOA with acoustic signals, the receiver can discern the index of the active transmitter precisely and attain very low error probability independent of any channel state information. As well, modulating the index of transmitters, as in space modulation, attains multiplexing gain and enhances the overall data rate. Analytical derivation of the error performance of the proposed system is presented and substantiated through comparison with Monte Carlo simulation results. Reported results reveal that the proposed system is a low complexity technique that is independent of the channel fading distribution, and can be designed to attain zero error probability with proper system dimensions.