Use cases for Underwater networking Environment monitoring Review - - PowerPoint PPT Presentation

Slide 1

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Environment monitoring

– Review how human activities affect the marine echosystem

Undersea explorations

– Detect underwater oilfields

Disaster prevention

– Monitoring ocean currents and winds (Tsunamis)

Assisted navigation

– Locate dangerous risks in shallow waters

Distributed tactical surveillance

– Intrusion detection (Navy), harbour protection

……

Use cases for Underwater networking

Slide 2

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• We don’t like our autonomous vehicles to be

too autonomous

• Safety of operations
• Real-time data is usually a requirement
• Cooperation, in general, requires some kind of

explicit information exchange

• Increased number of assets being deployed

(currently from few up to 15 underwater and surface nodes)

The Requirement for Underwater Communications

Slide 3

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UW Communications Channels: Qualitative

• verview

ACOUSTIC ELECTROMAGNE TIC

• Low power
• Small hardware
• High Bandwidth
• Requires line of

sight

• Requires tight

alignment of end points

• Susceptible to

marine fouling

• Sensitive to

suspended particles and turbidity

• Unaffected by

turbidity ,marine fouling or acoustic noise

• Crosses the air-

water boundary

• High bandwidth
• Very limited

networking support for underwater communication

• Loop antennas far

from ideal for small AUV integration

• Established

technology

• Full networking

support

• Supports ranges of

10s of Km

• Sensitive to

pressure and temperature gradients

• Performance

degrades in shallow water

• Limited bandwidth

Range Bandwidt h 10s b/s 10s Kb/s G b/s

OPTICA L

10s m 100s m 10s Km

Slide 4

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Acoustic communications: The Channel

“Advances in Integrating Autonomy with Acoustic Communications for Intelligent Networks of Marine Robots”,Toby Schneider, PhD thesis, 2013

Slide 5

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• Slow speed of propagation: five orders of magnitude lower than

in Radio Frequency)

• High Doppler shifts (example: v=2m/s, f=25 kHz, shift = 33 Hz)
• Spreading Loss
• Energy covering a big volume
• Absorption Loss (Frequency Dependent)
• Losses from energy propagation/ transfer
• Scattering Loss
• Surface scattering – rough sea surface introduces rapidly

fluctuating arrivals

• Bubble layer scattering

Acoustic communications: The Channel

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• Low Bandwidth
• Ambient noise and high interference level
• High bit errors and temporary loss of connectivity with

possible asymmetric links

• Waveguide, multipath, shadow zones
• Reflections from bottom and surface
• Refraction form spatially varying sound speed
• Masses of water with different characteristics
• Imposes multipath and time spread –ISI

Acoustic communications: The Channel

Slide 7

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Channel Impulse Responses : Examples

“Channel Sounding For Acoustic Communications: Techniques and Shallow Water Examples”, Paul Van Walree, Technical Report 2011

Wind burst at around t=25 seconds Cyclic arrival agreeing with the period of the dominant waves

Slide 8

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What a very benign acoustic channel will do to your signals

“Underwater Acoustic Communications Performance Modeling in Support of Ad Hoc Network Design”, Fox, W. L J; Arabshahi, P.; Roy, S.; Parrish, N., OCEANS 2007 , vol., no., pp.1,5, Sept. 29 2007-Oct. 4 2007

Slide 9

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UW Acoustics Physical Layer Performance

“The state of the art in underwater acoustic telemetry” Kilfoyle, D.B.; Baggeroer, A.B.; MIT & Woods Hole Oceanogr. Instn. Joint Program in Oceanogr. Eng., Woods Hole Oceanogr. Instn., MA IEEE Journal of Oceanic Engineering, Jan 2000

Slide 10

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• Interoperability is nonexistent !
• Software architectures based on the OSI stack fall short of

providing cross-layer information essential for achieving

• ptimized solutions
• There is no single adopted way to simulate the acoustic

channel

• Usually simulations fail to fully capture underwater channel

dynamics resulting in oversimplified scenarios

• Going at sea is expensive. Doing it in a controlled way

even more so.

• Reliable and robust multi-hop communication coping with

channel dynamics

Challenges

Slide 11

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• Interoperability will hopefully come ! JANUS is here, hopefully

promulgated as a standard soon.

• Improved data throughput to be pursued by:

–

More sophisticated modulation and coding schemes, signal processing techniques.

–

Multi-carrier systems,

–

Multi-modality, hybrid systems

• Software-defined architectures will improve sharing of solutions

and promote a true “survival of the fittest” in terms of protocol solutions

• Network security for underwater communications
• Combination of sensing, networking, communication and

navigation capabilities to improve underwater node operations

• Network coding, data compression and DTN solutions

Trends