A Wireless Tipping Point,
Open Spectrum Implications
Brough Turner
http://www.broughturner.com

1920s consumer radio receivers
Philips 2501
Very early tech, i.e. primitive
Crystal, Regenerative, Tuned RF …
Poor selectivity, low sensitivity,
low stability
Tuned RF
Crystal
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Radio Spectrum Occupancy
Urban areas, 30 MHz to 3 GHz. Above 3 GHz mostly vacant.
As measured by Shared Spectrum Company and the
University of Kansas Center for Research for the
NSF National Radio Network Research Testbed (NRNRT)
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New York City
Unusually heavy communications during Republican National Convention
August 30 to September 3, 2004 brought spectrum occupancy up to 13%.
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Most spectrum idle most of the time
806 – 928 MHz
Dublin Ireland Spectrum Occupancy Measurements
Collected On April 16-18, 2007
Shared Spectrum Company, www.sharedspectrum.com
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Most spectrum idle most of the time
806 – 928 MHz
Dublin Ireland Spectrum Occupancy Measurements
Collected On April 16-18, 2007
Shared Spectrum Company, www.sharedspectrum.com
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Most spectrum idle most of the time
806 – 928 MHz
Dublin Ireland Spectrum Occupancy Measurements
Collected On April 16-18, 2007
Shared Spectrum Company, www.sharedspectrum.com
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Open Spectrum
Noise, Interference, Chaos … !
How could it work?
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Open Spectrum
Noise, Interference, Chaos … !
How could it work?
Focus on Receiver Performance
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Visible light analogy
Our vision system
(eyes + visual cortex)
= extremely efficient
400-790 THz receiver
The product of years
of evolution!
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Spatial discrimination
For Humans:
~ 1/60th of a degree
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Enormous knowledge base
Detailed catalog of the characteristics of most
potential visible light sources
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Leveraging source motion
to increase received information …
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1920: Regulation made sense
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1920: Regulation made sense
2009: We’ve come a long way
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1920: Regulation made sense
2009: We’ve come a long way
Shared use of unlicensed spectrum
Enormous value creation
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1920: Regulation made sense
2009: We’ve come a long way
Shared use of unlicensed spectrum
Enormous value creation
Thermex Thermatron RF Dryers
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Open spectrum prospects
Regulation Vested interests
TV White Spaces
Crippled for now…
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Open spectrum prospects
Regulation Vested interests
TV White Spaces
Crippled for now…
What about higher frequencies?
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Spectrum Myth
TV Spectrum is “beach front” spectrum
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Spectrum Myth
TV Spectrum is “beach front” spectrum
Based on legacy technology, not physics!
Travels farther – No!
Goes thru walls – Not that different…
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Refraction and reflections
More at shorter wavelengths
Multiple versions “Multipath”
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MIMO: Multiple Input Multiple Output
Multiple paths improve link reliability and
increase spectral efficiency (bps per Hz),
range and directionality
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Rich Indoor MIMO Multipath
Source: Fanny Mlinarsky, Octoscope
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Municipal Multipath Environment
Source: Fanny Mlinarsky, Octoscope 25

TVWS – Beach-front Property?
MIMO antenna separation
>= ½ wavelength
2.1 meters at 70 MHz
21 cm at 700 MHz
But
2.5 cm for 5.8 GHz Wi-Fi
D-Link DAP-2553 Wavion Networks
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Multiple radios per chip
Like CPU cores … Intel
2x2 MIMO – 2008
4x4 MIMO – 2010-11
then
Fujitsu
8 radios, 16 radios?, …
what to use the silicon
for?
Beam-forming ! AMD
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Beamforming
2014: >200 Mbps Wi-Fi to >1 Km
at mass market prices ?
4x4 MIMO
with 12-16
antenna
elements
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Beamforming
2014: >200 Mbps Wi-Fi to >1 Km
at mass market prices ?
4x4 MIMO
with 12-16
antenna
elements
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Gaining spectrum for open use
Seeking only “Secondary access”
No interference with existing users
Geographic database; Listen-before-talk
License-exempt stations under positive
control of a “lightly” licensed station
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Wi-Fi 802.11y - 2008
Rich protocol set for “secondary access”
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Open spectrum
Wireless tipping point ahead
Focus on spectrum blocks above 3 GHz
More access at 5 GHz (4.9-6 GHz)
Anything between 6-10 GHz
“Secondary use”
Light licensing – 802.11y protocols
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Thank You
Brough Turner
broughturner@gmail.com
rbt@ashtonbrooke.com

Credits
Beyond those noted on individual pages…
Images…
Office building facade: http://commons.wikimedia.org/wiki/User:Beek100
Laptop icon: http://www.flickr.com/photos/ichibod/
Microwave oven: http://www.flickr.com/photos/code_martial/
802.11n performance in the field
http://www.tomshardware.com/reviews/beamforming-wifi-ruckus,2390.html
http://www.muniwireless.com/2009/02/23/80211n-dramatically-improves-
outdoor-wifi/
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