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Tricia Fu, Daniel Doonan, Chris Utley, Ronald Iltis, Ryan Kastner, and Hua Lee

Design and Development of a Software-Defined Underwater Acoustic Modem for Sensor Networks for Environmental and Ecological Research . Tricia Fu, Daniel Doonan, Chris Utley, Ronald Iltis, Ryan Kastner, and Hua Lee. Outline. Summary of MP Algorithm and Aquamodem Implementation

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Tricia Fu, Daniel Doonan, Chris Utley, Ronald Iltis, Ryan Kastner, and Hua Lee

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  1. Design and Development of a Software-Defined Underwater Acoustic Modem for Sensor Networks for Environmental and Ecological Research  Tricia Fu, Daniel Doonan, Chris Utley, Ronald Iltis, Ryan Kastner, and Hua Lee

  2. Outline • Summary of MP Algorithm and Aquamodem Implementation • Comparison w/ other Acoustic Modems • Hardware Implementation • Test Results: wire, air, tank • Future ideas (in the works)

  3. Design Objectives • Operating range: >= 100 m • Operating depth: up to 20 m • 90-day deployed lifetime • Handle multipath spread of several ms (up to 11.2 ms) • What else to add here?

  4. MP Algorithm

  5. MP Algorithm: Simulation • Estimated MIP from simulations, with actual number of multipaths = 10 and SNR = -4 dB. • Left: 2 training symbols, SER = 0.6645. • Right: 5 training symbols, SER = 0.1023.

  6. Matching Pursuits vs FSK • Direct Sequence Spread Spectrum (DSSS) preferred over frequency hopping when channel exhibits deep, narrow fades so that signal energy spread over wide bandwidth. • MP produces channel estimates during symbol demodulation process. • Add – check Iltis paper.

  7. Signaling Scheme • 8-ary code orthogonal modulation • 56-chip Gold sequences, 6000 chips/sec • Chip sequences applied to root-raised-cosine filter, 30 % excess bandwidth • 24 kHz center frequency • Guard interval, normally same length as symbol duration. • At Fs = 96 kHz rate, symbol rate is ~ 54 Hz, bit rate ~ 161 bps.

  8. Hardware Implementation • Texas Instruments’ C6713 DSP Board • Sonatech custom built transducers: horizontal omnidirectional coverage in 20 kHz – 30 kHz range • System power: alkaline primary cells • Commercial single-chip class D power amp driving matching network, automatic transmit/receive switch. • Tx transducer also connected to low-noise variable gain amplifier when power amp not operating.

  9. Hardware Implementation • Blah need djd input!

  10. Wire Test: results

  11. Air Test in Lab: results

  12. Air Test in Hallway: setup

  13. Air Test in Hallway : results

  14. Air Test in Stairway: setup Clockwise, from top left: Receiver setup on 3rd floor, view from middle of 4th and 3rd floor stairway, receiver setup on 4th floor.

  15. Air Test in Stairway: results

  16. Tank Test at MSI: setup • Need better pic from Chris (get Friday)

  17. Tank Test at MSI: noisy environment

  18. Tank Test Series A: video • To get from Chris (20-30 sec) on Friday.

  19. Tank Test Series A: error rates, results

  20. Tank Test Series A: Doppler Spread • Doppler Spectrum Plots, at 0.6 m distance and 12.7 m distance • Doppler Spread: 0.2 Hz vs 0.9 Hz

  21. Tank Test Series B • 5 training symbols per sync, up from 2 • NF estimation code integrated • Lower SNR due to Tx power amp problems (-1.0 dB vs. 6.1 dB) • Only 0.60 m results collected

  22. Tank Test Series B: results • Series A: 6.1 dB vs. Series B: -1.0 dB SNR • Note weak path at 6 ms not as apparent in Series B MIP compared with Series A MIP.

  23. Doppler Spread Plots

  24. Acknowledgments • MSI, Keck Foundation, Navy, Sonatech, blah

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