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AquaNode: A Solution for Wireless Underwater Communication Ryan Kastner Department of Electrical and Computer Engineering University of California, Santa.

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Presentation on theme: "AquaNode: A Solution for Wireless Underwater Communication Ryan Kastner Department of Electrical and Computer Engineering University of California, Santa."— Presentation transcript:

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2 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

3 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 Lagoon Fore reef Underwater wireless enabling technology for Moorea

4 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

5 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 lagoon MOOREA Lab Aquanodes Collection station with acoustic sensor array Ad hoc network between Aquanode sensors.

6 Underwater Acoustic Channel AquaNodes with acoustic modems/routers, sensors. Dock  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

7 WetNet using Aquanodes Dock Dockside acoustic/RF comms and signal processing. Cabled hydrophone array Wi-Fi or Wi-Max link CTD, currents, nutrient data to Internet. Adaptive sampling commands to AquaNodes. Data collection sites with acoustic modems/routers, sensors, mooring and underwater floats

8 Float Sensors Batteries Transducer Router Software Defined Acoustic Modem Sensor Interface Modem Circuitry Mooring AquaNode

9 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 Reconfigurable Hardware Platform Transducer CTD Sensor

10 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 Reconfigurable Hardware Platform Transducer CTD Sensor  Communication Interface:  Amplifiers, Transducers  Signal modulation  Hardware:  Software Defined Acoustic Modem (SDAM)  Reconfigurable hardware known to provide, flexible, high performance implementations for DSP applications

11  Complex, computationally intensive communication protocols  Limited power/energy  Ease of use: Good design tools, plug-n-play, reprogrammable Acoustic Modem Requirements Reconfigurable Hardware Platform Transducer Mapping CTD Sensor Communication Protocol Plug-N-Play

12 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

13 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?

14 AquaModem Data Sheet Signal and Data Parameters Data rate: 133 bps Chip duration T c =.2 msec. Symbol duration T sym = 11.2 msec. Time guard interval T c = 11.2 msec. M-sequence length L pn = 7 chips. Walsh sequence length N w = 8 Bandwidth = 5 kHz Carrier Frequency f c = 25 kHz Nominal range 100 – 300 m. Power Consumption Overview Load Tx State Rx State Sleep State CPU 440 mW 440 mW.30 mW CPU I/O 420 mW 420 mW.15 mW Flash Memory 165 mW 165 mW.10 mW Power Amp. 7.2 W.05 mW.05 mW Battery Total 9.3 W 2.1 W 10 mW Battery Life (Based on 20 amp-hours) Tx Duty Cycle Rx Duty Cycle Days.1%.2 % 624.5% 1 % 189 1% 2% 101 Power Amp and Transducer Matching Network TI 2812 DSP with CompactFlash, ADC, DAC < 1 meter Sonatech Transducer

15 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 b i. 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.

16 Transmitted Signal

17 Walsh/m-sequence Signal Parameters

18 8 Walsh Symbols

19 UWA Walsh/m-sequence GMHT-MP Modem Note: 112 Nyquist samples/symbol samples for channel clearing. Matching Pursuit Core Matching Pursuit Core Matching Pursuit Core Matching Pursuit Core arg min i Generalized multiple hypothesis test (GMHT)

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

21 Acoustic Modem Performance  Symbol Error Rate (SER)  Signal to noise ratio (E s /N 0 )  N f : # paths assumed by MP estimation  N  : Number of paths present > 4 dB gain over x SER

22 10dB = 90% reduction in amplifier power for all links less than 450 meters 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 Required Transmit Power

23 Energy used while “ asleep ” < 10% of total Energy used per bit transceived ≈ constant Energy Usage For all links up to 400 meters, projected energy use is ≤ 50 mJ per bit In most cases CPU power dominates (when using low transmit power)

24 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]

25 AquaModem Air Tests UCSB Engineering 1 Hallway 233’ 18’ 7’ 5’ 11’ 6’ 7’ 10’ 233’ 18’ 7’ 5’ 11’ 6’ 7’ 10’ Transmitter Location Receiver Location 233’ 18’ 7’ 5’ 11’ 6’ 7’ 10’ # Symbols Sent: 144 # Packets Sent: 36 Symbol Error: 1.4% Packet Error: 5.6% # Symbols Sent: 360 # Packets Sent: 90 Symbol Error: 1.1% Packet Error: 4.4% # Symbols Sent: 192 # Packets Sent: 48 Symbol Error: 10% Packet Error: 20.1%

26 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

27 Credits  Investigators: Ron Iltis, Hua Lee, Ryan Kastner  ExPRESS Lab –  Telemetry Lab –  AquaNode Research Team:  Research Tech – Maurice Chin  PhD Students – Bridget Benson, Daniel Doonan, Tricia Fu, Chris Utley  Undergrads – Brian Graham   Sponsor:


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