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SignalEx: Linking environmental acoustics with the signaling schemes

SignalEx: Linking environmental acoustics with the signaling schemes. Michael Porter Ocean Sciences Division Science Applications International and Keyko McDonald, Paul Baxley, Joseph Rice Space and Naval Warfare Systems Center San Diego, CA. SignalEx. Outline.

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SignalEx: Linking environmental acoustics with the signaling schemes

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  1. SignalEx: Linking environmental acoustics with the signaling schemes Michael Porter Ocean Sciences Division Science Applications International and Keyko McDonald, Paul Baxley, Joseph Rice Space and Naval Warfare Systems Center San Diego, CA

  2. SignalEx Outline • Motivation Case study: Front engineering test • SignalEx tests • Telesonar testbeds • Sites b, c, d • Measured channel impulse response • Predicted channel impulse response • Performance of a DPSK/DSSS system

  3. The National Oceanographic Partnership Program (NOPP) FRONT system is being installed by a consortium led by U. Conn • Cellular modems relay data to shore from the Montauk Point and Block Island USCG buoys • ADCP sensor nodes with trawl-resistant bottom frame design • Diver-free recovery: acoustic release holds ball floats, line packed in canister. • Acoustic modem (azimuthal omnidirectional 409 transducer) at apex; all other components below its lower plane. • Smooth outer surface to limit snaring of fishing gear. 9-km spacing

  4. Wind (kts) Depth (m) SignalEx S/N (dB) Depth (m) BER=0 (%) Sound speed (m/s) Upward refraction in FRONT-1 caused strong dependence on the sea-surface boundary Range (m) Year-day

  5. SignalEx Summary • The environment can have a big effect on modem performance • These effects are not well understood • SignalEx program • study a variety of modems in diverse environments • learn which work … and when • optimize modem parameters • develop and validate a channel model to provide a predictive capability for modem performance • Result: ’Smart Modem’ selects best operating mode for the channel

  6. Modem schemes tested in SignalEx

  7. SignalEx Mk-1 Telesonar testbeds Mk-2, 2000-01 Mk-1, 1998-99 Mk-1 Sublink’98

  8. SignalEx waveform LFM chirps (8-11 kHz) Type-a MFSK waveforms 7-tone comb LFM chirps (8-16 kHz) Type-x DPSK waveforms

  9. SignalEx spectrogram LFM chirps (8-11 kHz) Type-a MFSK waveforms 7-tone comb LFM chirps (8-16 kHz) Type-x DPSK waveforms

  10. SignalEx 2000 experiment locations SX-D Buzzard’s Bay (in SeaWeb00) August 10-11, 2000 SX-C San Diego (in SubLink00) May 23-25, 2000 SX-B New England Shelf (in ForeFront) April 17-20, 2000

  11. SignalEx-B in ForeFRONT (New England Shelf) April 17-20, 2000

  12. SignalEx-C in Sublink (Point Loma)May 23-25, 2000

  13. SignalEx-D (Buzzard’s Bay)August 10-11, 2000

  14. Ray/beam trace and incoherent TL

  15. CTD Record

  16. Predicted Impulse Response

  17. SignalEx SX-B (New England Shelf)impulse response

  18. SX-C (San Diego)Eigenrays and impulse response

  19. SX-D (Buzzard’s Bay) impulse response Drift 1: 0-3.5 km Drift 2: 2.2-4.2 km Drift 3: 1.4-3.8 km

  20. SignalEx Type-x (DPSK) bit error rates Range = 7 km Range = 5 km

  21. MFSK BER

  22. DSSS/DPSK (type-x) • Transmitter • ½ rate, contraint length 7 convolutional coder • (interleaver) • Gold sequence for spreading (4000 chips/sec) • BPSK on I/Q channels (QPSK out) (12 kHz carrier) • Shaping filter • Receiver • RAKE receiver, variable number of taps (or sparse) • Delay-locked loop • Viterbi decoder, 35 stage lookback • (John Proakis/Ethem Sozer Delphi/NEU)

  23. SignalEx DSSS/DPSK (type-x) bit errors in SX-B400-bit transmissions8 kHz bandwidth

  24. SignalEx DSSS/DPSK bit errors in SX-C64-bit transmissions; 3 kHz bandwidth R=3 km R=5 km

  25. SignalEx DSSS/DPSK bit errors in SX-D (Drift 1)500-bit transmissions; 8 kHz bandwidth Channel errors Convolutional coding

  26. SignalEx DSSS/DPSK bit errors in SX-D (Drift 3)500-bit transmissions; 8 kHz bandwidth Channel errors Convolutional coding

  27. Summary • Channel impulse response is well-predicted by classical multipath picture • Type-x multi-access DPSK performs reliably at 100 bps in all cases tested to date (ranges from 0-7 km) • Further SignalEx analysis will provide common-platform comparisons between many signaling schemes

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