1 / 26

AquaNode: A Solution for Wireless Underwater Communication

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. Lagoon. Fore reef. Monitoring in Moorea.

oren
Download Presentation

AquaNode: A Solution for Wireless Underwater Communication

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  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. Lagoon Fore reef 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. Aquanodes Lab MOOREA Ad hoc network between Aquanode sensors. lagoon Collection station with acoustic sensor array 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 < 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. Matching Pursuit Core Matching Pursuit Core arg min i Matching Pursuit Core Note: 112 Nyquist samples/symbol + 112 samples for channel clearing. Matching Pursuit Core UWA Walsh/m-sequence GMHT-MP Modem Generalized multiple hypothesis test (GMHT)

  19. Acoustic Modem Performance • Nf: # paths assumed by MP estimation • N: Number of paths present • True multipath intensity profile (MIP) MP identifies major paths using one symbol of information

  20. > 4 dB gain over FSK @ .5 x 10-3 SER 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. 10dB = 90% reduction in amplifier power for all links less than 450 meters 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 used per bit transceived ≈ constant Energy used while “asleep” < 10% of total 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? (< 100 US $) • Computation • Data rates aren’t 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:

More Related