ACOMMS: from cm to km and bps to Gbpsuwa.ua.edu/uploads/1/1/2/5/112596777/slides_singer...High...

ACOMMS: from cm to km and bps to Gbps

Andrew Singer

Sijung Yang, Michael Oelze, Youssef Hashash, and Omar Baltaji, Univ. Illinois Urbana Champaign

Thomas Riedl, James Younce, OceanComm, Inc

2018 NSF WORKSHOP ON UNDERWATER WIRELESS COMMUNICATIONS AND NETWORKING

Seismic communication between the burrows of

kangaroo rats, Dipodomys spectabilis.

https://www.washingtonpost.com/news/wonk/wp/2015/10/04/what-people-in-1900-thought-the-year-2000-would-look-like/

2018 NSF WORKSHOP ON

UNDERWATER WIRELESS COMMUNICATIONS AND [email protected]

High Frequency Acoustics

Larger acoustic bandwidths available

Background noise level independent of sea state

More compact, directional tx/rx possible

Underwater absorption prevents long-range HF,

but enables distance selectivity

Doppler effects require (per-path) resampling for mobile

applications

Nonlinearities in the medium increase with center

frequency and bandwidth



Subsea WIFI Hotspots

Today’s Seafloor-to-Space Network

E.g. Satcom at >1 Mbps

Fast, but limited to

above water.

RF links

E.g. Optical fiber at >1 Gbps

Fast, but requires

>$100k/day vessel for

tether management.

Wired links

E.g. 1 kbps at 5 km range

Slow, but good range

and low operating cost.

Acoustic links



Experimental Underwater HF Acoustic Communications

Acoustic bandwidth dominates achievable rate at longer distances, at shorter ranges, Doppler compensation key

Data rates Distances Modulation

23.4 kbps 7.2 km 16-QAM

39 kbps 2.7 km 16-QAM

1 Mbps 100 m 16-QAM

350 Mbps .01 m 64-QAM

[2]

cm km



Beam Pattern and Absorption Enabled LPI/LPD Comms

Adversary

Low Detection Probability

Signal attenuates,

doesn’t reach

Transmit Receive

comms distance D

clandestine distance D*F

Array

w/ SNR gain

AdversaryLow Detection Probability

Directional Transmit,

outside of beam



LPD Constrained Channel Capacity

LPD constraint: -10dB SNR @ 1.5D No LPD constraint



Time-Scale Processing for Motion



• Along a singe path, dispersionless

• Multipath, dispersion more complicated

Time-Scale



Through-Tissue HF Acoustic Communications



Hero Experiments in HF ACOMMS

• Setup below achieved 120 Mbps (64 QAM at 20MHz) using focused 20 MHz transducer and needle hydrophone

• Using 80MHz matched transducers with 128 QAM at 50MHz symbol rate achieved 350Mbps

• Amplifier and medium nonlinearities limited performance.

• Gbps is possible with MIMO array, better handling of nonlinearities

16

Sketch of ultrasound tank at UIUC



Acoustic/Seismic Communication through Soils17

Typical Soil Layer Variability in Urban Settings

Typical Borehole

Hashash et al. 2014

Piezometer (water pressure sensor)

Inclinometer (lateral deformation sensor)

http://www.geokon.com/6150 http://www.geokon.com/Piezometers



Acoustic/Seismic Communication through Soils18

Cerna-Diaz et al. 2016 Plan View

96 cm

66

cm

Cross-Section

Accelerometer-xx

Accelerometer-yy

Piezometer

LVDT

Bender Element

Typical centrifuge testing

device for earthquake

simulation



Acoustic Communication Through Soils

Field

1m

15m

25m

35m

• Subwoofer source

• 10 Hz QPSK at 30Hz center

• BER < 1E-4 up to 35m

• 20 bps at 35m, 10bps at 50m

50 m



Commerce Control List:

20https://www.pmddtc.state.gov/regulations_laws/itar.html

The updated U.S. Munitions List (USML) includes:

(iv) Acoustic modems, networks, and communications equipment with

real-time adaptive compensation or employing Low Probability of

Intercept (LPI);

and classifies such items as "Military Electronics".

https://www.pmddtc.state.gov/regulations_laws/itar.html

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