Wavefront segmentation in phase-conjugate arrays for spatially modulated acoustic communication

Research on underwater acoustic communication has shown that throughput and reliability can be improved if the spatial dimension is exploited to create multiple parallel channels in the ocean. This work proposes a technique for creating such channels that builds on the concept of a time-reversal mirror, a retroreflective array that focuses signals at a given point in the ocean by emitting acoustic rays along the directions of impinging energy. The approach used for creating these channels is based on space-time segmentation of received wavefronts, so that distinct transmitted messages can be associated with them. Unlike other parallelization techniques, individual channels exhibit low intersymbol interference, and all channels arrive synchronously at the focus. Due to these properties, input-output channel behavior can be approximately modeled as Rayleigh flat fading, thus providing a framework for applying several results that have been developed for wireless radio channels with low delay dispersion. Simulation results illustrate the performance of this technique and the impact of segmentation and beamforming accuracy