Acoustic Communications ANCHOR Workshop Feb 27-Mar 1 2006
description
Transcript of Acoustic Communications ANCHOR Workshop Feb 27-Mar 1 2006
Acoustic Communications ANCHOR WorkshopFeb 27-Mar 1 2006
Lee Freitag
Woods Hole Oceanographic InstitutionWoods Hole, Massachusetts
Outline• Communications system design
• Applications and Results• High frequency
• Medium Frequency
• Low Frequency
• Networking
• Interoperability
• Standardization
• Recommendations
Frequency Regimes
0.1 1 10 100 1k 10k 100k
Frequency (Hz)
Seismic Tomography
Typical Communications Band 1-50 kHz
Marine Mammals
Ambient Noise Studies
VLF MF VHF
Long-RangeNavigation
LF HF
Layered Architecture
From draft ASTM standard on communications developed by Committee F41, UUVs, with sponsorship from PMS-403 (US Navy).
Frequency Regimes
0.1 1 10 100 1k 10k 100k
Frequency (Hz)
Seismic Tomography
Typical Communications Band 1-50 kHz
Marine Mammals
Ambient Noise Studies
VLF MF VHF
Long-RangeNavigation
LF HF
UUVs and Scientific Applications
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.
Previous Results
Compressed Pre-stored Sidescan Images Transmitted from REMUS at AUV Fest 2001
Two AUV Simultaneous Operation with Acoustic Re-direction for MCM Work
Initial HoldingPattern
Vehicle 2 Path: Re-Acquisition Missions with REMUS equipped with APL-UW Acoustic Lens
Actual Missions Sent Using the Acoustic Modem
Frequency Regimes
0.1 1 10 100 1k 10k 100k
Frequency (Hz)
Seismic Tomography
Typical Communications Band 1-50 kHz
Marine Mammals
Ambient Noise Studies
VLF MF VHF
Long-RangeNavigation
LF HF
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.
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.
Frequency Regimes
0.1 1 10 100 1k 10k 100k
Frequency (Hz)
Seismic Tomography
Typical Communications Band 1-50 kHz
Marine Mammals
Ambient Noise Studies
VLF MF VHF
Long-RangeNavigation
LF HF
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.
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.
Interoperability
Application Layer: Compact Control Language (CCL)
• Standardized messages for TIME, POSITION, BATTERY, etc.
Surf-Zone Crawler Cetus II
REMUS Search-Classify-Map
Physical Layer: WHOI Frequency-Hopping Standard
• Low-rate (80 bps) standard for inter-operable modem communications.
Solar AUV: WHOI and Benthos Acoustic Modems
Real-Time Data: Two different Modems
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
Cetus II
REMUS AUVs
Gateway Buoys
Bluefin Sea Lion
Nekton Ranger
Compact Control Language Spec.
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 meterschar heading_encoded; LATLON_COMPRESSED lat_start; // ack only, where
started LATLON_COMPRESSED lon_start; char spare[3]; } MODEM_MSG_DATA_REDIRECT;
Messages are documented in detail using C-language structures with example hex dumps for use in validation.
Example Message: Bathymetry
Table 1: Bathymetry Message Fields
Bytes
Description
116699
Message type indicatorSpare byteDepth[3]Altitude[3]Latitude[3]Longitude[3]
32 Total bytes used
Example Message: Redirect Survey
Table 2: Redirect Message Fields
Bytes
Description
1133121121112111333
Message type indicatorSpare byteLatitude of center of search areaLongitude of center of search areaSpeed/Depth FlagsDepth goal encoded transitSpeed encoded transitDevice command transitDepth goal encoded transitSpeed encoded transitDevice command transitNumber of rowsRow length (meters)Row spacing (odd rows)Row spacing (even rows)HeadingLatitude of start (in acknowledgement)Longitude of start (in acknowledgement)Spare bytes
32 Total bytes used
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 100Slow
Fast
Msg
Rat
e
0 % Collided 100Slow
Fast
Msg
Rat
e
4-Way Handshake AlgorithmSimple (Greedy) Algorithm
Modular Acoustic Communications Vision
Acoustic Channel
Proprietary Modulation
N Types
Standard Modulation
M Types
Acoustic Modem
Manufacturer 1
Modem Interface & Driver
Standard Acoustic Modem Software API
NetworkType 1
NetworkType N
Standard Modulation
M Types
Acoustic Modem
Manufacturer P
Modem Interface & Driver
Proprietary Modulation
N Types
Different types of networks can be supported on top of multiple modems: Fixed, ad-hoc, etc.
Common API allows network development to be independent of modem
Modems Support open, proprietary and Navy-only protocols.
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
Questions?