ABSTRACT
The performance of acoustic modems in the ocean is strongly affected by the ocean environment. A storm can drive up the ambient noise levels, eliminate a thermocline by wind mixing, and whip up violent waves and thereby break up the acoustic mirror formed by the ocean surface. The combined effects of these and other processes on modem performance are not well understood. The authors have been conducting experiments to study these environmental effects on various modulation schemes. Here the focus is on the role of the thermocline on a widely used modulation scheme (frequency-shift keying). Using data from a recent experiment conducted in 100-m-deep water off the coast of Kauai, HI, frequency-shift-key modulation performance is shown to be strongly affected by diurnal cycles in the thermocline. There is dramatic variation in performance (measured by bit error rates) between receivers in the surface duct and receivers in the thermocline. To interpret the performance variations in a quantitative way, a precise metric is introduced based on a signal-to-interference-noise ratio that encompasses both the ambient noise and intersymbol interference. Further, it will be shown that differences in the fading statistics for receivers in and out of the thermocline explain the differences in modem performance.
ACKNOWLEDGMENTS
This work was supported by the Office of Naval Research. We would like to express particular appreciation to the team from the Marine Physical Laboratory at the University of California, San Diego, William Hodgkiss, Jeff Skinner, and Dave Ensberg for the vertical array data used here. The authors also gratefully acknowledge the University of Delaware team, led by Mohsen Baidey, for the CTD and thermistor data used for this analysis. We would also like to thank Naval Research Enterprise Internship Program (NREIP) student Laura Meathe and SPAWARSYSCEN, San Diego employee Leo Ghazikhanian for their assistance with operating the Telesonar Testbed instrument. Additionally, we would like to acknowledge Joe Rice for the Telesonar Testbed concept and for his support during its development. The KauaiEx Group consists of: Michael B. Porter, Paul Hursky, Martin Siderius (HLS Research), Mohsen Badiey (University of Delaware), Jerald Caruthers (University Southern Mississippi), William S. Hodgkiss, Kaustubha Raghukumar (Scripps Institute of Oceanography), Daniel Rouseff, Warren Fox (University of Washington), Christian de Moustier, Brian Calder, Barbara J. Kraft (University of New Hampshire), Keyko McDonald (SPAWARSSC), Peter Stein, James K. Lewis, and Subramaniam Rajan (Scientific Solutions).
- 1. M. B. Porter and the KauaiEx Group, “The Kauai experiment,” in High-Frequency Ocean Acoustics (AIP, Melville, NY, 2004), pp. 307–321. Google ScholarCrossref
- 2. M. Siderius, M. B. Porter, and the KauaiEx Group, “Impact of thermocline variability on underwater acoustic communications: Results from KauiEx,” in High-Frequency Ocean Acoustics (AIP, Melville, NY, 2004), pp. 358–365. Google ScholarCrossref
- 3. M. B. Porter, V. K. McDonald, P. A. Baxley, and J. A. Rice, “Signalex: Linking environmental acoustics with the signaling schemes,” in Proceedings of MTS/IEEE Oceans00 (IEEE, New York, 2000), pp. 595–600. Google ScholarCrossref
- 4. N. M. Carbone and W. S. Hodgkiss, “Effects of tidally driven temperature fluctuations on shallow-water acoustic communications at ,” IEEE J. Ocean. Eng.0364-9059 25, 84–94 (2000). Google ScholarCrossref
- 5. J. G. Proakis, Digital Communications, 3rd ed. (McGraw-Hill, New York, 1995). Google Scholar
- 6. D. B. Kilfoyle and A. B. Baggeroer, “The state of the art in underwater acoustic telemetry,” IEEE J. Ocean. Eng.0364-9059 https://doi.org/10.1109/48.820733 25, 4–27 (2000). Google ScholarCrossref, ISI
- 7. J. Rice et al., “Evolution of seaweb underwater acoustic networking,” in Proceedings of MTS/IEEE OCEANS’00 Conference (IEEE, New York, 2000), pp. 2007–2017. Google ScholarCrossref
- 8. V. K. McDonald, P. Hursky, and the KauaiEx Group, “Telesonar testbed instrument provides a flexible platform for acoustic propagation and communication research in the band,” in High-Frequency Ocean Acoustics (AIP, Melville, NY, 2004), pp. 336–349. Google ScholarCrossref
- 9. J. G. Proakis, “Coded modulation for digital communications over Rayleigh fading channels,” IEEE J. Ocean. Eng.0364-9059 16, 66–73 (1991). Google ScholarCrossref
- 10. R. J. Urick, Principles of Underwater Sound (McGraw-Hill, New York, 1983). Google Scholar
- 11. A. Zielinski, Y. H. Yoon, and L. Wu, “Performance analysis of digital acoustic communication in a shallow water channel,” IEEE J. Ocean. Eng.0364-9059 20, 293–299 (1995). Google ScholarCrossref
- 12. C. Bjerrum-Niese, L. Bjorno, M. Pinto, and B. Quellec, “A simulation tool for high data-rate acoustic communication in a shallow-water time-varying channel,” IEEE J. Ocean. Eng.0364-9059 21, 143–149 (1996). Google ScholarCrossref
- 13. M. B. Porter and H. P. Bucker, “Gaussian beam tracing for computing ocean acoustic fields,” J. Acoust. Soc. Am.0001-4966 https://doi.org/10.1121/1.395269 82, 1349–1359 (1987). Google ScholarScitation, ISI
- 14. M. Siderius and M. B. Porter, “Modeling techniques for marine mammal risk assessment,” IEEE J. Ocean. Eng.0364-9059 31, 49–60 (2006). Google ScholarCrossref
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