Design of a Lowcost Acoustic Modem for Moored Oceanographic Applications

1
Design of a Low-cost Acoustic Modem for Moored
Oceanographic Applications

• Bridget Benson, Grace Chang, Derek Manov, Brian
  Graham, Ryan Kastner
• University of California Santa Barbara
• WUWNet Presentation
• September 25th 2006

2
Outline

• Motivation
• Requirements
• Design
• Experimental Results
• Meeting the Requirements for the SB CHARM
• Future Work

3
Motivation

• To understand the ocean we must be able to
  observe large regions for long periods of time
• Such data could help predict earthquakes,
  tsunamis, or spread of a toxic algal bloom
• Platforms to measure large sets of data for long
  periods have been and are being established

4
Cabled Observatories
Marthas Vineyard Coastal Observatory
LEO
NEPTUNE
5
Moorings

• MBARI Ocean Observing System (MOOS)
• EOM cable in this mooring system parted in a
  storm on December 15, 2002.

6
Mooring Modem Requirements

• Sensor to Modem Interfacing

• Packaging

• Power

• Low Cost

• Data Transmission Range

• Data Transmission Rate

• Oceanic Motion Resistance

• Acoustic Interference

7
Mooring Modem Design
Transmitter
Receiver
8
Mooring Modem Specifications

• Power Supply 12 V
• Sampling Frequency 8 kHz
• Data Rate 80 bps
• Carrier Frequency 50 kHz
• Frequency Separation 320 Hz
• Transducer Beam Width 20o

9
Experimental Set-Up
10
Experimental Results
11
Experimental Results
12
SB CHARM
13
Meeting the Requirements for the SB CHARM
14
Future Work

• Determine actual power consumption and battery
  life of mooring modems
• Reduce size of the Mooring Modem design and
  waterproof the electronics
• Implement error correcting codes to reduce the
  BER
• Determine how to network the Mooring Modems
• Interface the Mooring Modem with oceanographic
  sensors using RS-232 protocol
• Test the Mooring Modem on the SB CHARM at depths
  0, 4, 10, and 22m

15
Acknowledgements

• W.M Keck Foundation
• Hua Lee and Ronald Iltis