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AquaNode: A Solution for Wireless Underwater Communication

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Establish monitoring sites in lagoons and on fore reefs surrounding Moorea ... TI 2812 DSP with CompactFlash, ADC, DAC 1 meter. Sonatech. Transducer ... – PowerPoint PPT presentation

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Title: AquaNode: A Solution for Wireless Underwater Communication


1
AquaNode A Solution for Wireless Underwater
Communication
  • Ryan Kastner
  • Department of Electrical and Computer Engineering
  • University of California, Santa Barbara
  • CREON GLEON Workshop
  • March 30, 2006

2
Monitoring in Moorea
  • Establish monitoring sites in lagoons and on fore
    reefs surrounding Moorea
  • Response variables measured
  • Weather
  • Tides, Currents and Flows
  • Ocean Temperature Color
  • Salinity, Turbidity pH
  • Nutrients
  • Recruitment Settlement
  • Size Age Structure
  • Species Abundance
  • Community Diversity

Underwater wireless enabling technology for Moorea
3
Why Use Wireless Underwater?
  • Wired underwater not feasible in all situations
  • Temporary experiments
  • Tampering/breaking of wires
  • Significant cost for deployment
  • Experiments over longer distances
  • Ocean observatories
  • ORION, LOOKING, MARS, NEPTUNE
  • Not ideal for coral reefs, lakes
  • AquaNode can easily be used in conjunction with
    observatories
  • Why not use radios and buoys?
  • Common use is buoy with mooring commercial
    radio on buoy to satellite, shore,
  • Buoys/equipment get stolen
  • Cable breakage, ice damage

Underwater wireless will enable new experiments
complement existing technologies
4
Scenario for WetNet for Eco-Surveillance
  • Deploy Ad hoc wireless (acoustic) network in
    lagoon
  • Network consists of AquaNodes with Conductivity,
    Temperature, Depth (CTD) sensors (and many
    others)
  • Ad hoc network allows AquaNodes to relay data to
    a dockside collector
  • AquaNode requirements
  • Low cost, low power wireless modems
  • Integral router
  • Integral CTD sensor suite
  • Additional nitrate, oxygen chemical sensors
  • Real-time data from Moorea available on Web

5
Underwater Acoustic Channel
  • Severe multipath - 1 to 10 msec for shallow water
    at up to 1 km range
  • Doppler Shifts
  • Long latencies speed of sound underwater approx
    1500 m/sec

Dock
AquaNodes with acoustic modems/routers, sensors.
6
WetNet using Aquanodes
CTD, currents, nutrient data to Internet.
Adaptive sampling commands to AquaNodes.
Wi-Fi or Wi-Max link
Dockside acoustic/RF comms and signal processing.
Cabled hydrophone array
Dock
Data collection sites with acoustic
modems/routers, sensors, mooring and underwater
floats
7
AquaNode
Software Defined Acoustic Modem
Transducer
Float
Router
Modem Circuitry
Batteries
Sensor Interface
Sensors
Mooring
8
Hardware Platform
  • Ideal One piece of hardware for all sensor nodes
  • Hardware is wirelessly updatable no need to
    retrieve equipment to update hardware for
    changing communication protocols, sampling,
    sensing strategies

Transducer
CTD Sensor
Reconfigurable Hardware Platform
9
Hardware Platform Interfaces
  • Sensor Interface
  • Must develop common interface with different
    sensors (CTD, chemical, optical, etc.) and
    communication elements (transducer)
  • Wide (constantly changing) variety of sensors,
    sampling strategies
  • Communication Interface
  • Amplifiers, Transducers
  • Signal modulation
  • Hardware
  • Software Defined Acoustic Modem (SDAM)
  • Reconfigurable hardware known to provide,
    flexible, high performance implementations for
    DSP applications

Transducer
CTD Sensor
Reconfigurable Hardware Platform
10
Acoustic Modem Requirements
  • Complex, computationally intensive communication
    protocols
  • Limited power/energy
  • Ease of use Good design tools, plug-n-play,
    reprogrammable

Transducer
Communication Protocol
CTD Sensor
Reconfigurable Hardware Platform
Plug-N-Play
Mapping
11
Design Considerations for SDAM
  • Multipath Spread Range of 1 to 10 milliseconds
    for shallow water at up to 1 km range
  • Larger bandwidths reduce frequency dependent
    multipaths
  • Transducers
  • Size/weight/cost proportional to wavelength
  • Acceptable propagation losses at 100 meter ranges
  • Waveform
  • M-FSK signaling
  • Datasonics/Benthos modems (used in Seaweb, FRONT)
  • Narrowband thus sensitive to frequency-selective
    fading.
  • Use more tones increasing sensitivity to
    Doppler spread.
  • Walsh/m-sequence signaling (Direct-sequence)
  • Provides frequency diversity due to wide
    bandwidth
  • Can be detected noncoherently

12
What about existing modems?
  • Commercial modems (Benthos, Linkquest)
  • Too expensive, power hungry for Eco-Sensing.
    Proprietary algorithms, hardware.
  • M-FSK (Scussel, Rice 97, Proakis 00) does use
    frequency diversity, but requires coding to
    erase/correct fades.
  • Navy modems
  • Need open architecture for international LTER
    community precludes military products.
  • Direct-sequence, QPSK, QAM, coherent OFDM
  • Great deal of work on DS, QPSK for underwater
    comms. But equalization, channel estimation are
    difficult. (Stojanovic 97, Freitag, Stojanovic
    2001, 2003.)
  • MicroModem (WHOI)
  • Best available solution for WetNet.
  • FSK/Freq. Hopping relies on coding to correct bad
    hops.

But can we do better? Less power? Wider
bandwidth?
13
AquaModem Data Sheet
Sonatech Transducer
lt 1 meter
TI 2812 DSP with CompactFlash, ADC, DAC
Power Amp and Transducer Matching Network
14
Walsh/m-Sequence Waveforms
Chip rate 5 kcps, approx. 5 kHz bandwidth.
Uses 25 kHz carrier. Use 7 chip m-sequence c per
Walsh symbol, 8 bits per Walsh symbol bi.
Composite symbol duration is thus T 11.2 msec.
(Longer than maximum multipath spread.) Symbol
rate is 266 bps, or 133 bps using 11.2 msec. time
guard band for channel clearing.
11 msec.
15
Transmitted Signal
1
1
-1
1
-1
-1
-1
1
1
-1
1
-1
-1
-1
-1
-1
1
-1
1
1
1
16
Walsh/m-sequence Signal Parameters
1
1
-1
1
-1
-1
-1
1
1
-1
1
-1
-1
-1
-1
-1
1
-1
1
1
1
17
8 Walsh Symbols
18
UWA Walsh/m-sequence GMHT-MP Modem
Generalized multiple hypothesis test (GMHT)
19
Acoustic Modem Performance
  • True multipath intensity profile (MIP)
  • Nf paths assumed by MP estimation
  • N? Number of paths present

MP identifies major paths using one symbol of
information
20
Acoustic Modem Performance
  • Symbol Error Rate (SER)
  • Signal to noise ratio (Es/N0)
  • Nf paths assumed by MP estimation
  • N? Number of paths present

21
Required Transmit Power
  • Transmit power control
  • Adapt automatically to field conditions, Use only
    enough to get reliable links
  • Often use small of amplifier capacity ?
    Significant reduction in system energy use

22
Energy Usage
In most cases CPU power dominates (when using low
transmit power)
For all links up to 400 meters, projected energy
use is 50 mJ per bit
23
Battery life
  • System example uses alkaline D cells
  • (low self discharge, good J / )
  • 16 or 32 cells 1.3 or 2.6 MJ respectively
  • At 50 mJ per bit, with 16 cell battery,
  • endurance days 300 / rate bps

24
AquaModem Air Tests
UCSB Engineering 1 Hallway
7
6
Symbols Sent 144 Packets Sent 36 Symbol
Error 1.4 Packet Error 5.6
7
10
18
5
5
11
7
233
7
6
Symbols Sent 360 Packets Sent 90 Symbol
Error 1.1 Packet Error 4.4
7
10
18
5
5
11
7
233
7
6
Symbols Sent 192 Packets Sent 48 Symbol
Error 10 Packet Error 20.1
7
10
18
5
5
11
7
233
Transmitter Location
Receiver Location
25
Challenges
  • Power
  • Communication
  • Transducer size/weight/cost proportional to
    wavelength
  • Adaptive power control
  • Computation
  • Microprocessors extremely power hungry
  • Move towards FPGA, ASIC
  • Cost
  • Communication
  • Current transducer 3K US
  • Fish finders? (lt 100 US )
  • Computation
  • Data rates arent particularly high ? simple
    microprocessors
  • Communication protocols complex ? DSP, FPGAs
  • Low power/energy will cost money ? FPGA, ASIC
  • Ease of use
  • Plug-n-play interfaces to sensors
  • Change network/communication protocols
  • Adjust sampling strategies

26
Credits
  • Investigators Ron Iltis, Hua Lee, Ryan Kastner
  • ExPRESS Lab http//express.ece.ucsb.edu/
  • Telemetry Lab http//telemetry.ece.ucsb.edu/
  • AquaNode Research Team
  • Research Tech Maurice Chin
  • PhD Students Bridget Benson, Daniel Doonan,
    Tricia Fu, Chris Utley
  • Undergrads Brian Graham
  • http//aquanode.ece.ucsb.edu/
  • Sponsor
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