KauaiEx: Environmental effects on HF acoustic propagation with application to communications Free

The Kauai Experiment (22 June–9 July 2003) was designed to study high‐frequency (8–50 kHz) acoustics in a shallow‐water waveguide. In contrast to much of the previous literature, emphasis was placed on multipath arising from multiple boundary interactions. Various participants were interested in different applications; however, a core theme was the role of the environment on acoustic communications. A great deal of effort was made to characterize the environment including the surface wave spectrum, 2D temperature structure along the propagation path, salinity, currents, and bottom properties. Most of these parameters were measured continuously over the 2 weeks of the experiment, providing information on the diurnal cycles. At the same time, extensive acoustic measurements were made using a variety of vertical line arrays, some of which spanned the entire water column. The acoustic measurements included channel probes to characterize the variation of the impulse response. These probes were interleaved with a variety of modulation schemes for communications including noncoherent methods such as MFSK (multifrequency shift keying), and DPSK (differential phase‐shift keying), as well as coherent schemes such as QAM (quadrature amplitude modulation), OFDM (orthogonal frequency division modulation), and PPC (passive‐phase conjugation) methods. Thus, the experiment provides a vast amount of information relating environment to acoustic propagation to modem performance. This talk will present an overview of key lessons learned to date.