1. Seaweb acoustic com/nav networks
DARPA ATO Disruption Tolerant Networking Program
August 2, 2005
Seaweb acoustic com/nav networks
Joseph A. Rice
SPAWAR Systems Center, San Diego
Naval Postgraduate School, Monterey
Seaweb is a US Navy experimental technology.
SPAWAR Systems Center, San Diego

2. US Navy Seaweb Initiative Enabling Undersea FORCEnet for cross-system, cross-platform, cross-mission, cross-nation interoperability
Integrated undersea applications
Littoral ASW sensor telemetry
METOC sensor telemetry
Sensor-to-sensor cueing
Submarines
Submersibles
UUVs
Collaborative operations
Command & control
Deployable ranges
Harbor defense
Through-water digital com/nav networks
Scaleable wide-area wireless grid
Composeable architectural flexibility
Fixed and mobile autonomous nodes
Gateways to command centers
Persistent and pervasive
Low source level, wide band, high freq
J. Rice, “Enabling Undersea FORCEnet with Seaweb Acoustic Networks,” Biennial Review 2003, SSC San Diego TD 3155, pp , December 2003
SPAWAR Systems Center, San Diego

3. Demonstrated capabilities: FBE-India June 2001
Racom
buoy
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
SPAWAR Systems Center, San Diego

4. Seaweb message example: Multi-Access Collision Avoidance (MACA) Internet Protocol (IP)
G. Hartfield, Performance of an Undersea Acoustic Network during Fleet Battle Experiment India, MS Thesis, Naval Postgraduate School, Monterey, CA, June, 2003
DATA
RTS
CTS
CTS
RTS
DATA
DATA
CTS
RTS
RTS
CTS
DATA
SPAWAR Systems Center, San Diego

5. 4/26/2017
US Navy SPAWAR SBIR topic N advanced and commercialized DSP-based acoustic comms SBIR contractor: Benthos, Inc. (formerly Datasonics, Inc.)
ATM-885
telesonar modem
3rd generation telesonar modem, Benthos ATM-885
Introduced in 2000
TMS320C5410 DSP
5-kHz bandwidth
2400 bit/s, uncoded
15 kbit/s with optional daughter board
Various forward-error-correction options
4th generation telesonar in development, SBIR N03-224
Standard firmware for non-networked applications
UUV command & control
Oceanographic telemetry
Tsunami warning systems
Oil industry
US Navy firmware for Seaweb applications
K. Scussel, “Acoustic Modems for Underwater Communications,” Wiley Encyclopedia of Telecommunications, Vol. 1, pp , Wiley-Interscience, 2003
SPAWAR Systems Center, San Diego

6. Planned approach: 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
Final decision
SPAWAR Systems Center, San Diego

7. Demonstrated capability: MACA (multi-access collision-avoidance) protocol enables undersea networks with security, reliability, efficiency, and low cost
RTS
9 bytes A
CTS
9 bytes B
DATA
up to 2 kbytes
SRQ
9 bytes
DATA
up to 2 kbytes
Seaweb channel-tolerant utility packets resolve the compound constraints of:
Variable QoS, link outages
Channel multipath, Doppler, dynamic SNR
Limited spectral bandwidth
Asymmetric, half-duplex channel
Slow propagation, long latencies
Multi-access interference
Battery-limited operations
J. Rice, et al, “Adaptive Modulation for Undersea Acoustic Telemetry,” Sea Technology, May 1999
SPAWAR Systems Center, San Diego

8. Seaweb 2005 NSW 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
New repeater mooring design
Iridium-equipped Racom buoy
SDV Periscope Controller
Compressed image telemetry
NPS, SSCSD, CSS, Benthos
DADS ASW Barrier
Sea Eagle ACTD NSW Expeditionary Ops
2010 Mine RECO
SPAWAR Systems Center, San Diego

9. 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 Seaweb 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
SPAWAR Systems Center, San Diego

10. Demonstrated capabilities: Seaweb 2004 UV racom buoy
6-8 min deployment time
Deck Staging
SPAWAR Systems Center, San Diego

11. Seaweb 2004 Undersea Vehicle Experiment cellular grid deployment
Average speed 6.5 knots
Average 1 repeater every 20 min
SPAWAR Systems Center, San Diego

12. SPAWAR Systems Center, San Diego

13. Seaweb 2004 grid post mortem
Impacted by trawling along the 300-m isobath 3 nodes removed, 6 nodes displaced or damaged
COMEX
FINEX
SPAWAR Systems Center, San Diego

14. Seaweb 2004 Experiment Undersea Vehicle initiates the Seaweb sessions
Seaweb network-layer statistics show excellent performance with dropped messages attributable to UV limited aspect, UV fix-expansion uncertainty, and interference from other UV active sonar
Seaweb network-layer success
Ship
Ship
Initiating message
Response message
Return receipt
Undersea Vehicle
Undersea Vehicle
SPAWAR Systems Center, San Diego

15. Iridium satellite constellation
The Seaweb Initiative is performing Seaweb navigation experiments this year as risk mitigation for CNAV Seaweb 2005 UUV Experiments Monterey Bay, May 9-11, July St. Andrews Bay, December 5-9
GPS satellite
constellation
Iridium satellite constellation
Racom buoy
gateway node
Shipboard
command center
ARIES UUV
NPS
SLOCUM
UUV
constellation of
6 Seaweb repeater nodes
fixed on seabed
SPAWAR Systems Center, San Diego

16. DARPA CNAV architectures include situation adaptive, energy conserving, and transitional topologies
Mobile formations
Swarms
Mobile node as gateway
Zebranet flooding
Assimilation following ad hoc deployment
Fixed grids
Self-healing
Seamule
SPAWAR Systems Center, San Diego

17. What can DTN do for Seaweb?
Network layer is fragile – needs dynamic routing for healing during/after disruption
No reliable packet transport
need mechanism for recovering lost packets at the network layer
No support for data mules
Infrastructure support needs work
currently no packet counter (move to 8b)
rough time synchronization: ~0.1s resolution, 16b timer, ~12 hour rollover
Seaweb expertise is UW acoustics & systems, not in networking
Simulation support lacking (OPNET radio modeler has been adapted for the telesonar channel)
Development funding & assistance from network experts
SPAWAR Systems Center, San Diego

18. What does Seaweb do for D-DTN? (why get involved?)
General:
Closely related to tactical radio MANET problem
Naval warfare applications/transition
Specific:
Reality check for DTN in harsh environments
“brutal constraints” comparable to MANPACK constraints
DTN isn’t a bolt-on – need a stripped-down bundle protocol
issues with time stamps, header efficiency, time sync
DTN must be integrated into system with routing etc
DTN gets a hard problem with a likely transition on success
Can DTN be made to work in such constrained environments?
Testbed
system to sea roughly 4 times a year
SPAWAR Systems Center, San Diego

19. Seaweb spiral development
Conclusion: Seaweb is an enabling technology for Undersea FORCEnet and Sea Shield
Seaweb spiral development
Fulfilling the Seaweb blueprint
Directional transmit & receive
Four bands
Full physical-layer repertoire, from low-rate/clandestine to high-rate/overt signaling
Adaptive modulation & power control
Automatic cellular handoff for mobile nodes
Ad hoc network initialization
Integration with manned platforms
¼ A-size modem
Asymmetric
links
Submarine
Low-rate C2
High-rate
data telemetry
Autonomous node
Seaweb advanced concepts
Saturating the undersea battlespace
Backward compatible with Seaweb
Seastar tier
Sensor grids and UUV swarms against SSK, UUV, and sea-mine threats
Networked weaponry
Fully mobile networks (e.g., CNAV)
Seastar
local-area
network
Seaweb
wide-area
network
Seamules
SPAWAR Systems Center, San Diego