

Extending WiFi to one mile, thanks to empty TV channels - abraham
http://arstechnica.com/tech-policy/news/2011/04/extending-wifi-to-one-mile-thanks-to-empty-tv-channels.ars

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willidiots
Whitespace is a mess. Uncertain regulatory restrictions, narrow channels, lack
of standardization. That said, it's got a lot of potential for specific uses,
as this article shows.

The CSMA congestion problem already exists in the WISP world. Ubiquiti built
their own in-house TDMA protocol to get around it. I think Alvarion and Canopy
have similar, if simpler, timeslotting capabilities.

What's interesting is that the 802.11 standard actually includes a Point
Coordination Function for this sort of application, but very few (if any)
chipsets have ever implemented it.

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derobert
_"The longest link he could make with existing point-to-point WiFi connections
was 400-500 feet; with the new Super WiFi gear in the TV band, he can reach a
mile—and it's not a point-to-point signal."_

Something doesn't make sense here. This is the furthest they could get with
point-to-point line of sight links, on towers. When I worked at a WISP, we
routinely made longer PtP links—heck, even longer point-to-multipoint links. A
mile should be easily doable with a clear line of sight.

Using <http://www.afar.net/rf-link-budget-calculator/> shows that a five-mile
link should be no problem with 24dBi grid dishes (which are more or less the
size of DirecTV, DISH, etc. dishes).

~~~
wmf
"signals don't easily penetrate the tree branches and leaves which surrounded
Aguirre's home"

The whole point is non line of sight.

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VladRussian
the phased array WiFi switches have interesting feature - adaptively found
best beam direction to your computer may actually be not a straight line from
the switch to you, instead it may happen to be a reflected beam.

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wmf
Other than Vivato (who went broke), is there any shipping outdoor phased-array
WISP equipment?

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thaumaturgy
Huh. Anybody have any idea what the FCC restrictions are on stuff like this?

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endian
_"Guerra is part of a Rice team [...whose...] goal is basic research on
providing broadband in the TV "white spaces" — empty channels that the
government recently cleared for use by unlicensed Internet providers"_

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thaumaturgy
Yeah, I was hoping to find a little bit more in-depth information though. I'm
finding reports of a handful of companies (including Google) being selected to
be database "administrators" for this, but I can't get clarity on whether such
a database is supposed to apply to equipment manufacturers or to service
providers.

There's also an ongoing federal lawsuit over the use of this technology.

I'm still looking into it though.

edit: looks like the equipment is still under development, experimental, and
not commercially available. Phooey. I can't find any development timelines,
either, and it looks like the FCC wants to restrict devices using certain
frequencies to certain geographic areas, so it could be a while before it
becomes possible to roll this out.

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trotsky
You need an experimental license because none of the (still prototype) devices
have received FCC approval yet. In theory, the use of the whitespace
frequencies is already open to the public - if you had approved equipment. The
rate that the FCC is approving experimental licenses has accelerated a lot in
the past 9 months, and new deployments are rolling out much faster as some
quasi-commercial gear has started going to trial. While it is difficult to say
for sure when the first generally available radios might arrive, I've heard a
vendor suggest the second half of 2012. That would be for enterprise gear
though, it might take a couple of years before it was hitting consumer price
points. The database issues shouldn't be a big deal.

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dasil003
And what does the signal look like if you tune a TV to that channel? Is it
possible to fabricate a signal that shows up as a recognizable image?

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StavrosK
From what I gather, it's already very recognizable as moving specks of salt
and pepper.

