1. US Navy Seaweb program Undersea acoustic sensing, signaling, communications & networks
Networked through-water digital com/nav
Scalable wide-area wireless grid
Composable architectural flexibility
Fixed and mobile autonomous nodes
Gateways to command centers
Persistent and pervasive
Low source level, wide band, high freq
TRANSEC attributes
Integrating sensors, UUVs, SSNs
Sponsors: ONR, PEO LMW, SOCOM PEO IIS, CTTSO, PEO C4I & Space, PEO IWS, OSD, DARPA, SBIR
Collaborations:
TTCP Unet (Undersea networking)
DARPA DTN (Disruption-Tolerant Networking)
ONR DADS (Deployable Autonomous Distributed Sys)
ONR ASAP (Adaptive Sampling & Prediction)
OSD Coalition Warfare
Seaweb is in routine use by several client programs
POC: (831)
Seaweb is an SSC San Diego S&T product expected to reach Milestone C in FY08.
Seaweb is an enabling technology for an ASW sensor network program (DADS), an ISR sensor network program, and a METOC sensor network program.
Seaweb is routinely applied to undersea data telemetry, UUV command & control, and sea-mine remote control.
Seaweb modems are COTS items developed by Navy SBIR contracts.
Seaweb modem software is Navy developed and controlled.
Seaweb racom (radio/acoustic communication) gateway buoys incorporate various radio types, including Iridium SATCOM, FreeWave Line-of-Sight packet radio, Cellular telephone modem, Special Radio, and GPS.
Seaweb has been integrated with organic submarine sonar.
Seaweb has successfully supported submarine networked Comms at Speed & Depth (Fleet Battle Experiment India and TASWEX-04).
Seaweb is certified to carry encrypted GCCS-M messages.
J. Rice, “Enabling Undersea FORCEnet with Seaweb Acoustic Networks,” Biennial Review 2003, SSC San Diego TD 3155, pp , Dec 2003

2. Iridium, FreeWave, Telesonar Telesonar repeater nodes
US Navy Seaweb program Applied research, “Discovery & Invention”, 6.2 funding Art of the possible for Maritime sensor networks & Undersea Distributed Networked Systems (UDNS)
Iridium satellite
Ashore & afar
command centers
Racom buoy with
Iridium, FreeWave, Telesonar
UUVs
SDV
SSN/SSGN
with Seaweb server
Telesonar repeater nodes
ASW / ISR / MCM
nodes
Float
Telesonar modem
Acoustic release
Weight

3. SPAWAR SBIR topic N advanced and commercialized DSP-based acoustic comms SBIR contractor: Teledyne Benthos (formerly Datasonics, Inc.)
Pre-SBIR
ATM ATM-865
SBIR Phase-2
ATM-875
SBIR Phase-3
ATM-885
TMS320C5410
3rd generation telesonar
Spiral development
all analog
10 b/s FSK
TMS320C50
2nd generation telesonar
Spiral development
SBIR Phase-1
ATM-850 (not shown)
achievement:
Stable COTS hardware
COTS & Navy firmware
8X less expensive
40X more efficient
Multi-band MFSK
1st generation telesonar
Technology transfer from MIT/WHOI
2007: 4th gen telesonar with TRANSEC features

4. TBED Navy’s first experimental digital sensor network 1995-96
“TBED” Telemetry Buoy Environmental Data
NSWC Coastal Systems Station, Panama City, FL
Objective: telemeter environmental data from distributed seafloor sensor nodes to one or more gateway nodes
Sea test in 1996
Gulf of Mexico, 60 km offshore Panama City, 45-m water
8-km node-to-node ranges achieved
4 Datasonics ATM-850 telesonar modems
150-bit/s, 1024-bit messages
Flooding protocol designed for up to 10 nodes
Advantages: Simple, COTS modem firmware, Plug & play, Routing tables not required, Centralized control not required
Disadvantages: Redundant communications, Not bandwidth efficient for fixed network, High latency
Analogous to terrestrial “Zebranet”
Well suited for delay-tolerant AUV mobile networks
J. Rice, et al, “Evolution of Seaweb Underwater Acoustic Networking” Proc IEEE Oceans 2000

5. Seaweb ’98 engineering experiment Buzzards Bay, MA, September 1999 An undersea wireless sensor network employing ten telesonar modems and an RF gateway buoy
41°43´
Racom-1
10-m water depths
10 ATM-875 telesonar modems
3-FDMA
3 sensor nodes
FreeWave gateway
Bi-directional routing tables
Scaleable architecture
ATM-875
Isobath contours at
5-meter intervals
1 km
41°35´
70°46´
70°36´
M. D. Green, J. A. Rice and S. Merriam, “Underwater acoustic modem configured for use in a local area network,” Proc. IEEE Oceans ’98 Conf., Vol. 2, pp , Nice France, September 1998

6. Seaweb ’99 engineering experiment Buzzards Bay, MA, August 1999 SSC San Diego, Delphi, Benthos, SAIC
FreeWave 900-MHz LOS gateway
Cellular Digital Packet Data (CDPD) gateways
Seaweb server
15 ATM-875 nodes
Seaweb ‘99 firmware
FDMA-6 network
Node addressing
Ranging
Handshake protocol
Adaptive power control
Remote-controlled routing
Commercial sensors
J. Rice, et al, “Evolution of Seaweb Underwater Acoustic Networking” Proc IEEE Oceans 2000

7. Seaweb 2000 engineering experiment
Buzzards Bay, Aug-Sept 2000
ATM-885 modems
FreeWave LOS gateway
Cellular Digital Packet Data (CDPD) gateways
Asynchronous TDMA
Rerouting
RTS/CTS handshake + ARQ
Isobath contours at
5-meter intervals

8. Demonstrated capabilities: FRONT ocean observatory National Oceanographic Partnership Program
Jan-June, 2002
FRONT-3
March-June, 2001
Concept
D. L. Codiga, et al, “Networked Acoustic Modems for Real-Time Data Telemetry from Distributed Subsurface Instruments in the Coastal Ocean: Application to Array of Bottom-Mounted ADCPs,” J. Atmospheric & Oceanic Technology, June 2005

9. US participation in Canada’s ICESHELF 2002 April experiment in the Arctic Ocean
m water covered by rough ice of 2-8 m thickness and large subsurface ridges and keels
Upward-refracting water
Ice-mounted Seaweb network, first test of acoustic networking in the Arctic
Prepares for RDS-4 experiment with interoperable US and Canadian ASW sensor nodes

10. Demonstrated capabilities: FBE India June 2001
Racom
buoy
(Prior Seaweb tests with USS Dolphin submarine: Sublinks ’98, ’99, 2000)
SSN with BSY-1 sonar Seaweb TEMPALT
Ashore ASW command center
Seaweb server at SSN and ASWCC
Acoustic chat and GCCS-M links to fleet
SSN/MPA cooperative ASW against XSSK
Flawless ops for 4 continuous test days
Experimental DADS sensor node
J. 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

11. Precursor to Seaweb cellular routing Source node
Seaweb message example: Multi-Access Collision Avoidance (MACA) Internet Protocol (IP)
Fixed routing tables
Precursor to Seaweb cellular routing
Source node
DATA
RTS
CTS
CTS
RTS
DATA
DATA
CTS
RTS
RTS
CTS
DATA
G. Hartfield, Performance of an Undersea Acoustic Network during Fleet Battle Experiment India, MS Thesis, Naval Postgraduate School, Monterey, CA, June, 2003
Destination node

12. Iridium satellite radio links 3 glider UUV mobile nodes
Demonstrated capabilities: Seaweb network with UUVs US/Canada collaboration Gulf of Mexico, Feb 1-8, 2003
UUV nose
section
Iridium satellite radio links
Over-the-horizon
command center
Shipboard
command center
2 Racom buoy
gateway nodes
FreeWave radio links
Mobile gateway nodes
Mobile sensor nodes
200 km logged by UUVs
300 hrs logged by UUVs
Node-to-multinode comm/nav
6 fixed
repeater nodes
3 glider UUV mobile nodes

13. Iridium satellite constellation
Seaweb navigation development Seaweb 2005 UUV Experiments Monterey Bay, May 9-11, July St. Andrews Bay, December 5-9
Iridium satellite constellation
GPS
satellite
constellation
Racom buoy
gateway node
Shipboard
command center
ARIES UUV
NPS
M. Hahn, Undersea Navigation via a Distributed Acoustic Communications Network, MS Thesis, Naval Postgraduate School, June 2005
S. Ouimet, Undersea Navigation of a Glider UUV using an Acoustic Communications Network, MS Thesis, Naval Postgraduate School, Sept 2005
Slocum
UUV
EMATT
UUV
constellation of
6 Seaweb repeater nodes
fixed on seabed
M. Reed, Use of an Acoustic Network as an Underwater Positioning System, MS Thesis, Naval Postgraduate School, June 2006

14. (d) Networked telemetry
Demonstrated capability: All Seaweb communications yield the node-to-node range as a by-product of the link-layer RTS/CTS handshake. The broadcast ping command returns ranges to all neighboring nodes.
(a) Networked command
(b) Broadcast ping
(c) Echoes
(d) Networked telemetry

15. Seaweb cellular grid deployment
Theater ASW Experiment – TASWEX 04
Submarine speed & depth (CSD)
Average speed 6.5 knots
Average 1 repeater every 20 min

17. Seaweb 2004 grid post mortem
Impacted by trawling along the 300-m isobath 3 nodes removed, 6 nodes displaced or damaged
COMEX
FINEX
FINEX
H. Kriewaldt, Communications Performance of an Undersea Acoustic Wide-Area Network, MS Thesis, Naval Postgraduate School, December 2005

18. Seaweb 2005 experiment February 2005, Panama City, FL
SRQ link-layer mechanism
NSMA (Neighbor Sense Multiple Access, a cross-layer variation on CSMA)
Ranging and node localization
Iridium-equipped Racom buoy
Compressed image telemetry
NPS, SSCSD, CSS, Benthos

19. Demonstrated capability: Selective Automatic Repeat Request (SRQ) is a link-layer mechanism for reliable transport of large datafiles even when the physical layer suffers high BERs
Node A
Node B
RTS
1. Node A initiates a link-layer dialog with Node B.
2. Node B is prepared to receive a large Data packet as a result of RTS/CTS handshaking.
CTS
HDR
4. Node B receives 12 subpackets successfully; 4 subpackets contained uncorrectable bit errors.
3. Node A transmits a 4000-byte Data packet using byte subpackets, each with an independent CRC.
5. Node B issues an SRQ utility packet, including a 16-bit mask specifying the 4 subpackets to be retransmitted.
6. Node A retransmits the 4 subpackets specified by the SRQ mask.
SRQ
7. Node B receives 3 of the 4 packets successfully (future implementation of cross-layer time-diversity processing will recover 4 of 4). B issues an SRQ for the remaining subpacket.
HDR
9. Node B successfully receives and processes Data packet.
SRQ
8. Node A retransmits the 1 subpacket specified by the SRQ.
HDR
J. Kalscheuer, A Selective Automatic Repeat Request Protocol for Undersea Acoustic Links, MS Thesis, Naval Postgraduate School, June 2004

20. Seaweb telesonar repeater node
Seaweb telesonar modem, circa
Texas Instruments TMS320C5410 DSP
Teledyne Benthos COTS hardware
US Navy firmware
Spectral bandwidth = 5 kHz (9-14 kHz)
SL = 174 dB (typ) re 1m
Modulation = Multi-channel 4-FSK
Forward Error Correction
Raw bit rate = 2400 bit/s
Data packets = 800 b/s
Utility packets = 150 b/s
DI = 0 dB (omni)
K. Scussel, “Acoustic Modems for Underwater Communications,” Wiley Encyclopedia of Telecommunications, Vol. 1, pp , Wiley-Interscience, 2003

21. Transmit/Receive Board Digital Board
Small Business Innovative Research SBIR N is producing the 4th-gen telesonar modem Contractor: Teledyne Benthos, Inc. Sponsor: PEO C4I & Space, PMW 770
Transmit/Receive Board
Digital Board
ATM-885
board set
New ATM-900
Spectral bandwidth up to 20 kHz, Operating frequency up to 70 kHz
Processing speed increased by 2X, Memory increased by 20X
Xmit efficiency improved by 50%, Rcvr efficiency improved by 50%
One new digital board can support 4 T/R boards (for multi-band, MIMO, spatial diversity, etc)
SBIR Ph-2 Option will integrate SBIR N directional ducer (Image Acoustics, Inc)
SBIR Ph-3 5-year delivery-order contract being negotiated by SSC San Diego

22. Current work The Seaweb network organizes and maintains itself under the control of autonomous master nodes or Seaweb servers at command centers
Preparation
5 days
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
Installation
1 day
Activation
1 hr
Obey spacing constraints
Test master node link to gateway
Awaken network nodes
Discover neighbors
Initiation
2 hrs
Registration
1 hr
Obtain reciprocal channel response
Perform 2-way ranging
Sound own depth
Initialize spectral shaping
Report link data & node configuration
Assimilate data at master node
Optimization
1 hr
Operation
90 days
Compute optimal/alternate routes
Assign protocols
Monitor energy, links, and gateways
Optimize life, TRANSEC, and latency

23. Current research Adaptive modulation
Node A
Node B
Demodulate RTS
transmission
Reconstruct transmitted
waveform
RTS
Estimate channel scattering function
CTS
Specify
Data-packet comms
parameters
Determine h(τ, t ) / Doppler / SNR
S. Dessalermos, Undersea Acoustic Propagation Channel Estimation, MS Thesis, Naval Postgraduate School, Monterey, CA, June 2005
Data
Map channel characteristics against available repertoires and signal techniques
Decision

24. Current research Asymmetric links
Low-rate C2
Submarine
High-rate
data telemetry
Autonomous node

25. Node-to-node range (m)
Unet through-water acoustic signaling range regimes Categorized at Unet Workshop 5 and refined at Unet Workshop 6
Range regime
Node-to-node range (m)
Frequencies (kHz)
Use
Very short
5 – 50
>100
Proximity communications,
e.g., Seamule
Short
50 – 500
30-100
Local-area networks,
e.g., Seastar
Medium
500 – 5k
8-30
Wide-area networks,
e.g. Seaweb
Long
5k – 50k
1-8
Tactical paging
Very long
50k – 500k
<1
Blue-water paging

26. Acoustic link budget
Each term in the standard radio link budget is analogous to specific quantities in the sonar equation.
SNR(f) = PSL(f) – TL(f) – AN(f) + DIxmt(f) + DIrcv(f)
We develop the acoustic link budget as a wideband model because, unlike most radio channels, the acoustic channel exhibits strong frequency dependency.
PSL
pressure
spectrum
level AN
DIxmt
DIrcv TL
SNR
Pxmt
Prcv

27. Sonar equation analysis (TL+AN) for 500-m range and 4 noise spectraW=
20kHz
PSL
TL + NSL (dB re 1μPa)
Frequency (kHz)

28. Current research Seastar local-area networks
Asymmetric links: high-BW links from peripheral nodes to central node; low-BW links from central node to peripherals and peer-to-peer
Point-to point communications at short ranges (50 to 500 m) employ the kHz band
Data are fused/beamformed at the central node
Seastar LAN increases the carrying capacity of the undersea environment by an order of magnitude
Central node reports compressed information through the wide-area network
Applications include sensor arrays, sensor clusters, autonomous MCM vehicles, and SDV/DDS dive teams
DADS magnetometer array a near-term pilot application
Prototype Seastar at AUVfest 2007, 2 NPS thesis students
ONR 321MS 6.2 funding
Seaweb
WAN
Seastar
LAN

29. Over 40 Seaweb deployments Spirally developed USW com/nav capability
NPS
Iceweb, 2002
Q272 Seaweb
GoM, 2003 Q G H K U R
FBE-I, 2001
RDS-4, 2002
FRONT-4, 2002
TASWEX04
Seaweb NSW, 2004