the significance of tv white spaces
DESCRIPTION
Although I have high hopes for TVWS I also expect that, 10-20 years from now, we will look back on the TV White Spaces decision and recognize it as a breakthough in getting access to all otherwise unused spectrum, for example in the 3 GHz - 9 GHz range.TRANSCRIPT
Disclaimer
• I look forward to great things from TVWS • I am worried adop@on will be slowed by: – Law suits – Restric@ve requirements for an antenna’s Height Above Average Terrain (HAAT)
– Adjacent channel restric@ons limit urban use and limit the poten@al market size
• But Carl invites me because I’m disrup@ve!
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Long term significance
• License-‐exempt access to otherwise unused spectrum, on a secondary use basis, despite powerful vested interests
4 October 2010 3
Long term significance
• License-‐exempt access to otherwise unused spectrum, on a secondary use basis, despite powerful vested interests
• 20 year dream: similar access to unused spectrum between 3 GHz and 9 GHz
• Why? Higher spectrum more useful !
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Spectrum Myths
TV Spectrum is “beach front” spectrum
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Spectrum Myths
TV Spectrum is “beach front” spectrum
• Based on 20th century technology, not physics! – Travels farther thru the air – No! – Thru windows – roughly the same – Goes thru masonry – yes, with 50,000 waas!
Higher frequency • Tighter Fresnel zone • Less clearance required
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Noise
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Free space path loss
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Free space path loss
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Seems to say more , more loss
Free space path loss
But this equa@on encapsulates two effects: ① Actual path loss (independent of frequency! ) ② Receiving antenna aperture (assumed to be ½ wavelength)
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Seems to say more , more loss
Free space path loss
But this equa@on encapsulates two effects: ① Actual path loss (independent of frequency! ) ② Receiving antenna aperture (assumed to be ½ wavelength)
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Seems to say more , more loss
5 GHz photons go just as far as 50-‐700 MHz photons !
Refrac@on and reflec@ons
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Shorter wavelength -‐ more reflec@ons, refrac@on “Mul@Path” “Ghosts” if a single receiver
MIMO: Mul@ple Input Mul@ple Output
• Mul@ple paths improve link reliability and increase spectral efficiency (bps/Hz), range & direc@onality
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Beamforming ~2014: >300 Mbps Wi-‐Fi to ~1 Km at mass market prices …
4x4 MIMO with 8 antenna elements
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Beamforming ~2014: >300 Mbps Wi-‐Fi to ~1 Km at mass market prices …
4x4 MIMO with 8 antenna elements
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Beamforming ~2014: >300 Mbps Wi-‐Fi to ~1 Km at mass market prices …
4x4 MIMO with 8 antenna elements
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MIMO & Beamforming
• Ideal antenna element separa@on >= ½ wavelength – 2.1 meters at 70 MHz – 21 cm at 700 MHz
• But only – 2.5 cm for 5.8 GHz Wi-‐Fi
Wavion Networks
D-‐Link DAP-‐2553
Ruckus Wireless
