Shallow Water Fluctuations and Communications

Time reversal communications exploits spatial diversity to achieve spatial and temporal focusing in complex ocean environments. Spatial diversity easily can be provided by a vertical array in a waveguide. Alternatively, spatial diversity can be obtained from a virtual horizontal array generated by two elements, a transmitter and a receiver, due to relative motion between them, referred to as a synthetic aperture. In this case, the same data is transmitted periodically. The cost is a reduction in the overall data rate by the number of transmissions accumulated in generation of synthetic aperture. In addition, Doppler compensation is required involving Doppler shift estimation and re-sampling of the broadband communication signal.