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SignalEx: Linking environmental acoustics with the signaling schemes Michael Porter Ocean Sciences Division Science Applications International and Keyko.

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Presentation on theme: "SignalEx: Linking environmental acoustics with the signaling schemes Michael Porter Ocean Sciences Division Science Applications International and Keyko."— Presentation transcript:

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 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 SignalEx

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-kmspacing

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

5 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 SignalEx

6 Modem schemes tested in SignalEx typeMethodAnalysis group aMulti-frequency shift keyed (MFSK) SAIC/SPAWARSSC bFrequency-Hopped FSK (FH- MFSK) Benthos xDifferential phase-shift keyed (DPSK) Northeastern Univ. SAIC/SPAWARSSC dN-QAM (BPSK, QPSK, 16- QAM) Northeastern Univ., Delphi, NUWC, Benthos ePulse-Position Modulation (PPM) SAIC/SPAWARSSC gOrthogonal Frequency Division Multiplexing (OFDM) Polytechnic Univ. hMulti-Carrier Code Division Multiple Access (MC-CDMA) Polytechnic Univ.

7 Mk-1, 1998-99 Mk-1 Mk-2, 2000-01 Mk-1Sublink98 Telesonar testbeds SignalEx

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

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

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

14 Ray/beam trace and incoherent TL

15 CTD Record

16 Predicted Impulse Response

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

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

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

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

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 DSSS/DPSK (type-x) bit errors in SX-B 400-bit transmissions 8 kHz bandwidth SignalEx

24 DSSS/DPSK bit errors in SX-C 64-bit transmissions; 3 kHz bandwidth SignalEx R=3 km R=5 km

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

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