Acoustic Communications ANCHOR Workshop Feb 27-Mar 1 2006

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Acoustic Communications ANCHOR WorkshopFeb
27-Mar 1 2006

• Lee Freitag
• Woods Hole Oceanographic Institution
• Woods Hole, Massachusetts

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• Outline
• Communications system design
• Applications and Results
• High frequency
• Medium Frequency
• Low Frequency
• Networking
• Interoperability
• Standardization
• Recommendations

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Frequency Regimes
VLF
MF
LF
HF
VHF
Ambient Noise Studies
Marine Mammals
Typical Communications Band 1-50 kHz
Long-Range Navigation
Seismic
Tomography
0.1
1
10
100
1k
10k
100k
Frequency (Hz)
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Layered Architecture
From draft ASTM standard on communications
developed by Committee F41, UUVs, with
sponsorship from PMS-403 (US Navy).
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Frequency Regimes
VLF
MF
LF
HF
VHF
Ambient Noise Studies
Marine Mammals
Typical Communications Band 1-50 kHz
Long-Range Navigation
Seismic
Tomography
0.1
1
10
100
1k
10k
100k
Frequency (Hz)
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UUVs and Scientific Applications
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Very High-Rate Shallow Water (15 m)

• Test Parameters
• 1.5 km Range
• 10 kHz BW
• 4 bits per Hertz
• 8 channel array (one meter)
• 40,000 bps raw, 30,000 bps coded.

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Previous Results
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Compressed Pre-stored Sidescan Images Transmitted
from REMUS at AUV Fest 2001
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Two AUV Simultaneous Operation with Acoustic
Re-direction for MCM Work
Vehicle 2 Path Re-Acquisition Missions with
REMUS equipped with APL-UW Acoustic Lens
Initial Holding Pattern
Actual Missions Sent Using the Acoustic Modem
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Frequency Regimes
VLF
MF
LF
HF
VHF
Ambient Noise Studies
Marine Mammals
Typical Communications Band 1-50 kHz
Long-Range Navigation
Seismic
Tomography
0.1
1
10
100
1k
10k
100k
Frequency (Hz)
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Medium Frequency Example 6 km

• Test Parameters
• 6 km Range
• 200 m depth
• 1.25 kHz BW
• 2 bits per Hertz
• 8 channel, 8 m array
• 2500 bps raw, 2,000 bps coded.

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Medium Frequency Example 44 km

• Test Parameters
• 44 km Range
• 200 m depth
• 1.25 kHz BW
• 2 bits per Hertz
• 8 channel, 8 m array
• 2500 bps raw, 2,000 bps coded.

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Frequency Regimes
VLF
MF
LF
HF
VHF
Ambient Noise Studies
Marine Mammals
Typical Communications Band 1-50 kHz
Long-Range Navigation
Seismic
Tomography
0.1
1
10
100
1k
10k
100k
Frequency (Hz)
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(No Transcript)
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(No Transcript)
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VLF Example AET Tomography Signal 3200 km

• Test Parameters
• 3200 km Range
• Pacific Ocean
• 37.5 Hz BW
• 1 bit per Hertz
• 20 channel array
• 37.5 bps max raw, 0.1-20 bps coded, depending
  on array.

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VLF Example AET Tomography Signal 3200 km

• Test Parameters
• 3200 km Range
• Pacific Ocean
• 37.5 Hz BW
• 1 bit per Hertz
• 20 channel array
• 37.5 bps max raw, 0.1-20 bps coded, depending
  on array.

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Interoperability

• Physical Layer WHOI Frequency-Hopping Standard
• Low-rate (80 bps) standard for inter-operable
  modem communications.

• Application Layer Compact Control Language (CCL)
• Standardized messages for TIME, POSITION,
  BATTERY, etc.

Surf-Zone Crawler
Cetus II
Solar AUV WHOI and Benthos Acoustic Modems
Real-Time Data Two different Modems
REMUS Search-Classify-Map
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Multi-Vehicle Command and Control and
Interoperability
Multi-vehicle operations using a common
acoustic navigation network and common command
and control structure at AUV Fest 2003 and 2005
Surf-Zone Crawlers
Gateway Buoys
Nekton Ranger
REMUS AUVs
Cetus II
Bluefin Sea Lion
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Compact Control Language Spec.
Messages are documented in detail using
C-language structures with example hex dumps for
use in validation.
Example Message Format (Re-Direct) typedef
struct unsigned char mode // MDAT_REDIRECT
unsigned char message_number LATLON_COMPRESSED
lat // Center of search LATLON_COMPRESSED
lon // Center of search char
speed_depth_flags unsigned short
depth_goal_encoded_transit char
speed_encoded_transit unsigned char
device_cmd_transit //range. unsigned short
depth_goal_encoded_survey char
speed_encoded_survey unsigned char
device_cmd_survey unsigned char num_rows // 0
if not rows. unsigned short row_length // in
meters unsigned char spacing_0 // in meters
unsigned char spacing_1 // in meters char
heading_encoded LATLON_COMPRESSED lat_start
// ack only, where started LATLON_COMPRESSED
lon_start char spare3 MODEM_MSG_DATA_RED
IRECT
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Example Message Bathymetry
Table 1 Bathymetry Message Fields Table 1 Bathymetry Message Fields
Bytes Description
1 1 6 6 9 9 Message type indicator Spare byte Depth3 Altitude3 Latitude3 Longitude3
32 Total bytes used
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Example Message Redirect Survey
Table 2 Redirect Message Fields Table 2 Redirect Message Fields
Bytes Description
1 1 3 3 1 2 1 1 2 1 1 1 2 1 1 1 3 3 3 Message type indicator Spare byte Latitude of center of search area Longitude of center of search area Speed/Depth Flags Depth goal encoded transit Speed encoded transit Device command transit Depth goal encoded transit Speed encoded transit Device command transit Number of rows Row length (meters) Row spacing (odd rows) Row spacing (even rows) Heading Latitude of start (in acknowledgement) Longitude of start (in acknowledgement) Spare bytes
32 Total bytes used
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Network Access Protocol Prof. J. Schindall R.
Kanthan

• Objectives
• To allow all AUVs to cooperatively communicate
  and navigate in the field without centralized
  access control.
• Create fair access protocol.
• Allow desperate node to go first.
• Status Thesis complete available.

0 Collided 100
0 Collided 100
4-Way Handshake Algorithm
Simple (Greedy) Algorithm
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Modular Acoustic Communications Vision
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• Recommendations
• Confirm draft requirements vis-à-vis
• Platform needs and capabilities (size, etc.)
• Development effort (risk)
• Infrastructure cost
• Operations and Maintenance
• Develop functional specification to capture
  requirements
• Describe notional implementation which is
• Modular Layered
• Standardized (interoperable at various levels)
• Isolates high-risk developmental areas

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• Questions?