SignalEx: Linking environmental acoustics with the signaling schemes

Michael PorterOcean Sciences Division

Science Applications Internationaland

Keyko McDonald, Paul Baxley, Joseph Rice

Space and Naval Warfare Systems CenterSan Diego, CA

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

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 9-km spacingspacing

340 342 344 346 3480

10

20

30

Win

d sp

eed

(mph

)

340 342 344 346 3480

50

100

150C

orre

ct re

cept

ions

(%) R = 0.5 km

R = 1.0 kmR = 1.5 kmR = 2.0 km

Upward refraction in FRONT-1 caused strong dependence on the sea-surface boundary

Upward refraction in FRONT-1 caused strong dependence on the sea-surface boundary

Year-day

BE

R=

0 (%

)S

/N (

dB

)W

ind

(kt

s)

1485 1490 1495 1500

0

10

20

30

40

50

Sound Speed (m/s)

Depth

(m

)D

epth

(m

)D

epth

(m

)

Range (m)

Sound speed (m/s)

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

SignalEx

Modem schemes tested in SignalEx

type Method Analysis groupa Multi-frequency shift keyed

(MFSK)SAIC/SPAWARSSC

b Frequency-Hopped FSK (FH-MFSK)

Benthos

x Differential phase-shift keyed (DPSK)

Northeastern Univ.SAIC/SPAWARSSC

d N-QAM (BPSK, QPSK, 16-QAM)

Northeastern Univ., Delphi, NUWC, Benthos

e Pulse-Position Modulation (PPM)

SAIC/SPAWARSSC

g Orthogonal Frequency Division Multiplexing (OFDM)

Polytechnic Univ.

h Multi-Carrier Code Division Multiple Access (MC-CDMA)

Polytechnic Univ.

Mk-1, 1998-99Mk-1, 1998-99

Mk-1Mk-1

Mk-2, 2000-01Mk-2, 2000-01

Mk-1Mk-1Sublink’98Sublink’98

Telesonar

testbeds

Telesonar

testbeds

SignalEx

SignalEx waveform

LFM chirps(8-11 kHz)

7-tone comb

LFM chirps(8-16 kHz)

Type-a MFSK waveforms

Type-x DPSK waveforms

SignalEx spectrogram

LFM chirps(8-11 kHz)

7-tone comb

LFM chirps(8-16 kHz)

Type-a MFSK waveforms

Type-x DPSK waveforms

SignalEx 2000 experiment locations

SX-CSan Diego(in SubLink00)May 23-25, 2000 SX-B

New England Shelf(in ForeFront)April 17-20, 2000

SX-DBuzzard’s Bay(in SeaWeb00)August 10-11, 2000

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

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

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

Ray/beam trace and incoherent TL

CTD Record

Predicted Impulse Response

SX-B (New England Shelf)impulse response

SignalEx

SX-C (San Diego)Eigenrays and impulse response

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

Type-x (DPSK) bit error rates

Range = 5 km Range = 7 km

SignalEx

MFSK BER

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)

DSSS/DPSK (type-x) bit errors in SX-B

400-bit transmissions8 kHz bandwidth

SignalEx

Transmission 10 bps 50 bps 100 bps 200 bps 400 bps1 0 3 13 400 1582 0 0 3 46 1303 0 0 400 25 1264 0 0 1 10 605 0 0 0 0 306 0 0 0 4 747 0 0 0 0 158 0 0 0 15 1599 0 0 0 15 127

10 0 37 24 28 7311 0 400 205 400 207

DSSS/DPSK bit errors in SX-C64-bit transmissions; 3 kHz bandwidth

SignalEx

50 bps 100 bps 150 bps 300 bps 500 bps0 0 1 17 150 0 0 1 140 0 0 32 170 0 0 8 210 0 0 2 200 0 0 6 210 0 1 3 240 0 1 8 170 0 0 7 210 0 0 9 250 0 0 1 160 0 1 5 210 0 0 5 180 0 0 2 140 0 0 4 200 0 0 7 160 0 37 11 220 0 0 0 160 0 0 8 210 0 0 9 240 0 0 6 21

37 0 0 5 260 0 38 5 240 0 1 9 230 0 0 7 210 0 0 4 220 0 0 6 180 0 0 2 220 0 0 5 20

50 bps 100 bps 150 bps 300 bps 500 bps0 0 2 23 640 0 0 8 190 0 0 12 240 1 1 10 220 0 1 6 200 0 0 11 180 0 0 2 140 0 0 8 150 0 0 12 110 3 14 14 230 0 1 8 270 0 64 11 240 64 3 16 280 0 64 12 26

38 0 0 5 180 0 0 7 180 0 0 4 160 0 0 4 150 0 1 9 160 0 0 8 160 0 0 9 230 0 0 4 130 0 0 6 170 0 0 1 130 0 0 18 220 0 1 11 220 0 1 9 190 1 0 15 210 2 3 22 26

R=3 km R=5 km

DSSS/DPSK bit errors in SX-D (Drift 1)

500-bit transmissions; 8 kHz bandwidth SignalEx

Channel errors Convolutional coding

20 bps 50 bps 100 bps 200 bps 400 bps 20 bps 50 bps 100 bps 200 bps 400 bps7 0 0 11 46 0 0 0 0 387 1 0 5 41 0 0 0 0 230 0 0 1 28 0 0 0 0 00 0 0 0 23 0 0 0 0 8

242 1 5 1 32 121 0 0 0 050 4 0 0 24 36 0 0 0 25 0 0 64 62 0 0 0 34 577 0 0 0 60 0 0 0 0 361 0 0 1 46 0 0 0 0 158 0 2 0 47 0 0 0 0 286 0 0 2 27 4 0 0 0 0

123 0 7 30 32 93 0 0 13 3128 24 26 17 47 4 9 15 9 101 0 0 0 40 0 0 0 0 53 0 0 1 19 0 0 0 0 01 0 0 0 26 0 0 0 0 0

42 0 65 3 86 8 0 55 0 37

DSSS/DPSK bit errors in SX-D (Drift 3)

500-bit transmissions; 8 kHz bandwidth SignalEx

Channel errors Convolutional coding20 bps 50 bps 100 bps 200 bps 400 bps 20 bps 50 bps 100 bps 200 bps 400 bps

0 0 0 3 116 0 0 0 0 1170 0 254 7 43 0 0 125 0 122 0 0 10 62 0 0 0 0 940 0 0 3 56 0 0 0 0 270 0 0 1 83 0 0 0 0 591 0 0 5 42 0 0 0 0 110 0 0 0 66 0 0 0 0 470 0 0 6 145 0 0 0 0 910 0 0 0 22 0 0 0 0 00 0 0 1 38 0 0 0 0 130 0 0 6 33 0 0 0 0 00 0 0 3 25 0 0 0 0 00 0 0 0 41 0 0 0 0 60 0 0 0 31 0 0 0 0 40 0 0 2 48 0 0 0 0 350 0 0 3 33 0 0 0 0 120 0 0 0 30 0 0 0 0 40 0 0 1 193 0 0 0 0 1110 0 0 1 59 0 0 0 0 490 0 0 0 38 0 0 0 0 110 0 0 0 46 0 0 0 0 44

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