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Seaweb Acoustic Wide-Area Networks
for Undersea Sensor Grids
Joe Rice, Chris Fletcher, Bob Creber
SPAWAR Systems Center, San Diego
rice @ spawar.navy.mil
(831) 656-2982
Dave Johnson, ONR 321 Littoral ASW FNC (DADS)
Don Davison, ONR 321 Discovery (Telesonar)
Larry Green, ONR 321 Discovery (Sealan)
Jim Eckman, ONR 321 NOPP (FRONT)
Doug Harry, ONR 36 (SBIRs)
LCDR John King, NWDC (Sublink)
Seaweb Communication & Navigation
Seaweb
CONCEPT OF OPERATIONS
Extend networkcentric C4ISR into
the undersea
battlespace
Use telesonar digital communications to form deployable autonomous
distributed sensor networks with:
Rice, “Telesonar signaling and seaweb
• wide-area coverage
underwater wireless networks,” Proc. NATO
New Information Processing Techniques for
• architectural flexibility
Military Systems,” October 2000
• environmentally adaptive wireless links
• self-configuring ad hoc topologies
• fixed sensor nodes and repeater nodes
• fixed and mobile peripheral nodes, e.g. bi-static projectors and UUVs
• fixed and mobile gateway nodes linked to command centers
submerged, afloat, aloft and ashore
Space & Naval Warfare Systems Center, San Diego
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Background: 2nd-generation telesonar modem was
developed through a SPAWAR-sponsored SBIR phase-2
contract to Datasonics
Seaweb
ATM-885 3rd-generation telesonar modem was
developed through an ONR-sponsored SBIR phase-3
contract to Datasonics (now Benthos)
Recent Navy enhancements:
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Space & Naval Warfare Systems Center, San Diego
TMS320C5410 DSP chip
Improved low-power wake-up
Moderate-power addressing
Modularized type-A algorithms
Utility packets
Probe signals
Seaweb protocols
Partial-band modes
Adaptive power control
3
Seaweb
FBE India
June 2001
Space & Naval Warfare Systems Center, San Diego
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2 Racom gateway buoys
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2 DADS sensors
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10 telesonar repeaters
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USS Jefferson City
equipped with sublink
as a BSY-1 TEMPALT
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Ashore ASW command
center
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GCCS-M links to fleet
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Flawless ops for entire
4-day test period
4
Telesonar undersea digital communications
Seaweb
PROBLEM:
Littoral undersea environments impair signal propagation
A
RTS
CTS
DATA
B
ARQ
DATA
9 bytes
9 bytes
up to 2 kbytes
9 bytes
up to 2 kbytes
APPROACH:
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Low-data-rate, spread-spectrum, channel-tolerant, secure RTS utility packet
initiates the telesonar link and uniquely addresses the intended receiver node
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Received processes RTS as a channel probe, permitting estimation of
prevailing scattering function and identification of viable signaling options
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CTS utility packet fully specifies the format for ensuing DATA transmission
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DATA packet has optimal coding, modulation, bit-rate, and power
PAYOFF: Channel-adaptive modulation enables undersea networks with
Rice, et al, “Adaptive modulation for undersea
security, reliability, efficiency, and low cost
Space & Naval Warfare Systems Center, San Diego
acoustic telemetry,” Sea Technology, May5 1999
Telesonar message example
Space & Naval Warfare Systems Center, San Diego
Seaweb
6
The seaweb server interfaces the
undersea network and the client systems
Seaweb
Other Command Centers
TCP / IP
seaweb
1
seaweb
N
seaweb super server
passive Seaweb servers
“netTCP / IP
centric”
C4ISR
Sensor
Station
1
Sensor
Station
N
Command Center
Seaweb networks connect to manned
command centers via radio, acoustic,
wire, and fiber gateway links
Space & Naval Warfare Systems Center, San Diego
Fletcher, et al, “Undersea acoustic network operations
through a database-oriented server/client interface,” Proc.
IEEE Oceans, November 2001
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Seaweb
FBE-I seaweb service
DADS - shore links
(61 ASW contact reports)
DADS - sub links (listen-all)
Shore - sub links (cellular-like)
Shore - DADS links
Sub - shore link (122 messages)
Sub - DADS link
Shore - repeater links
Sub - repeater links
Approx 793 MAC-layer transmissions
(up to 3700 m)
135 ARQ-prompted retries
Space & Naval Warfare Systems Center, San Diego
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Seaweb
FBE-I Seaweb service
Space & Naval Warfare Systems Center, San Diego
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DADS - shore links (61 ASW
contact reports)
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Sub - shore links (122 messages)
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Approx 793 transmissions
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135 ARQ-prompted retries
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121
one retransmission
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5
two retransmissions
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9
three retransmissions
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2253 total RTS
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1753 total CTS
Creber, et al, “Performance of undersea acoustic
networking using RTS/CTS handshaking and ARQ
transmissions,” Proc. IEEE Oceans, November 2001
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Seaweb
FBE-I Seaweb service
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DADS - shore links (61 ASW
contact reports)
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Sub - shore links (122 messages)
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Approx 793 transmissions
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135 ARQ-prompted retries
Number of Message
Hops
83.0%
600
400
15.3%
200
0.6%
0
0
1
2
1.1%
3
Number of ARQs per Message Hop
Space & Naval Warfare Systems Center, San Diego
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121
one retransmission
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5
two retransmissions
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9
three retransmissions
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2253 total RTS
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1753 total CTS
Creber, et al, “Performance of undersea acoustic
networking using RTS/CTS handshaking and ARQ
transmissions,” Proc. IEEE Oceans, November 2001
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Throughput
Seaweb
DADS Report
Position Report
Comex/FINEX
Comb Pos Report
Opnote
Chat
Ovly
ATI.ATR
DADS Report
Total
Position Report
FBE-I June 20-23
Bandwidth Analysis for 20-
Message # Analysis for 20-23 June
14000
Comb Pos Report
Opnote
Opnote
20
Comex/FINEX
6/2
1/2
001
6/2
2/2
001
6/2
3/2
001
DADS Report
Space & Naval Warfare Systems Center, San Diego
ATI.ATR
6000
Total
Total
ATI.ATR
Ovly
Chat
Opnote
Comb Pos Report
Mess
Comex/FINEX
Position Report
DADS Report
4000
2000
Message
0
Types
6/23/2001
Ovly
8000
6/22/2001
Total
40
Ovly
6/21/2001
6/23/2001
Chat
10000
Bytes of Data
6/2
0/2
001
Comex/FINEX
Types
12000
60
0
16000
6/20/2001
of
ages
80
6/22/2001
100
# of messages
6/21/2001
6/20/2001
120
# of bytes
Total
ATI.ATR
Ovly
Chat
Opnote
Comb Pos Report
Message
Comex/FINEX
Position Report
DADS Report
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Seaweb
Packet latency
Latency (minutes)
Submarine to ASWCC, FBE-I June 22
10
Nominal latency about 1 minute
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Small deviations caused by
network route variations
8
Large latencies caused by
network interference or poor
channel forcing the automatic
use of handshake retries and/or
ARQs
7
6
5
4
Dropped packets caused by
inappropriate cellular addressing
by submarine
3
2
1
0
Packet number
Space & Naval Warfare Systems Center, San Diego
Rice, et al, “Networked undersea acoustic
communications involving a submerged submarine,
deployable autonomous distributed sensors, and a
radio gateway buoy linked to an ashore command
center,” Proc. UDT Hawaii, October 2001
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FRONT ocean observatory
Seaweb
FRONT-3, March-June, 2001
Space & Naval Warfare Systems Center, San Diego
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Seaweb 2001 included the Hydra off-board
sensor against USS Dolphin
Seaweb
9-week experiment
culminating in the annual
Seaweb 2001 firmware
CDPD modems used
extensively for gateway
comms
Network header introduced
for machine-to-machine
networked communications
ARQ formalized as a
separate dialog
RCPT and ACK utility
packets implemented
Space & Naval Warfare Systems Center, San Diego
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Iceweb 2002, April 2002
Seaweb
US participation in international ICESHELF 2002 experiment
Ice-mounted seaweb network
First test of acoustic networking in the Arctic Ocean
First integration of Canadian UCARA sensor as a seaweb node
Prepares for RDS-4 experiment with interoperable US and Canadian ASW
sensor nodes
Space & Naval Warfare Systems Center, San Diego
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Portable undersea comm/nav ranges
Seaweb
teaming with NUWC Keyport
Ping/Echo utility packet dialogs
Broadcast ping produces staggered echoes from all receivers
Mobile node can track own position, and range can track mobile node
FBE-I demonstrated the fundamentals of this seaweb application
Space & Naval Warfare Systems Center, San Diego
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Mobile Gateway
Seaweb
Slocum UUV Glider
Webb Research Corporation
SBIR Phase II awarded to produce mobile gateway
communication models:
Replace acoustic tracking system with telesonar modem
Move acoustic transducer to nose area
Incorporate mobile gateway missions into operating profile
Reserve buoyancy increase to allow better antenna height
New antenna designs for LOS and L-Band SATCOM radios
New nose cone, with new modem and altimeter transducers
Slocum Low-power Mobile Ocean
Profiler sponsored by ONR 322OM
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Space & Naval Warfare Systems Center, San Diego
Buoyancy driven
CTD sensor
GPS receiver and data radio
Antennas located on tail fin
Designed especially for shallow
water—can operate in less than
10 feet of water
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APL/UW Seaglider and
Webb Research SLOCUM glider serve as mobile
autonomous gateway/master nodes
Space & Naval Warfare Systems Center, San Diego
Seaweb
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Seaweb
Summary
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Seaweb is a wide-area network for sensor grids
 Fixed: DADS, Hydra, Kelp, UCARA, FRONT, Wetnet
 Mobile: SLOCUM, ARIES, EMATT
 Moored: Racom, Freewave, CDPD, Satcom options
Sealan is a local-area network for sensor clusters
 Centralized networks with asymmetric links
 DARWIN, oceanographic moorings, sensor uploads to
servicing UUVs, dive teams, MCM swarms
 Central nodes are Seaweb-compatible
Sublink permits submarine access
 USS Dolphin, Sublinks ’98, ’99, 2000
 USS Jefferson City, Sublink 2001, FBE-I
Space & Naval Warfare Systems Center, San Diego
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Seaweb
Back-up slides
Space & Naval Warfare Systems Center, San Diego
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Seaweb
2-node MAC-layer state diagram
Node A
idle
idle
Node B
Wake up
Xmt RTS
Rcv RTS
Time
out
Xmt CTS
Rcv CTS
RTS
Xmt DATA
Time
out
or ARQ
Rcv DATA
Xmt ACK/ARQ
Rcv ACK/ARQ
idle
Space & Naval Warfare Systems Center, San Diego
ARQ
ACK
idle
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FBE-I acoustic propagation
Ray-trace diagram for a bottom source and typical sound
speed profile for the region. Ray launch angles extend from
0 to 20 at 0.5 increments. Bottom reflected paths are
omitted for clarity.
Baxley, et al, “Shallow-water acoustic communications
channel modeling using three-dimensional Gaussian beams,”
Proc. MTS Ocean Community Conf., November 1998
Space & Naval Warfare Systems Center, San Diego
Seaweb
Sound speed profiles obtained from CTD measurements
before and after the experiment.
Simulated impulse responses for a bottom-deployed source
and receiver for five source ranges from 1 to 5 km at 1-km
increments.
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Seaweb
Sealan operates with situationally
adaptive multi-access modes
Polled TDMA
Token TDMA
Other multi-access modes:
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Scheduled TDMA
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Asynchronous TDMA
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CDMA/FDMA
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Clandestine modes
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Hybrid modes
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Handshaking modes
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Full-duplex modes
Space & Naval Warfare Systems Center, San Diego
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The telesonar network organizes and maintains
itself under the control of autonomous master
nodes or seaweb servers at command centers
Preparation
10 days
Installation
1 day
Activation
1 hr
Analyze mission requirements
Measure or predict environment
Model transmission channels
Predict connectivity range limits
Specify spacing, aperture, and node mix
Pre-program master node only
Obey spacing constraints
Test master node link to gateway
Awaken network nodes
Discover neighbors
Initiation
2 hrs
Obtain reciprocal channel response
Perform 2-way ranging
Sound own depth
Initialize spectral shaping
Registration
1 hr
Report link data & node configuration
Assimilate data at master node
Optimization
1 hr
Compute optimal/alternate routes
Assign protocols
Operation
90 days
Monitor energy, links, and gateways
Optimize life, covertness, and latency
Space & Naval Warfare Systems Center, San Diego
Seaweb
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Seaweb 2002-2003 experiments
Seaweb
FRONT-4, US Eastern seaboard
Signalex, San Diego Bay
HF Signalex, San Diego Bay
Iceweb 2002, Arctic Ocean
Wetnet 2002, San Diego Bay
Seaweb 2002, Buzzards Bay
DADS-D, San Diego Bay
RDS-4, Halifax, Canada
DADS-D, San Diego Loma Shelf
Asymmetric links, Monterey Bay
Jan-June 2002
April 2002
April 2002
April 2002
May 2002
July-Aug 2002
September 2002
Sept-Oct 2002
November 2002
July-Dec 2002
FBE-K
Singapore
Summer 2003
Fall 2003
Space & Naval Warfare Systems Center, San Diego
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