First Public White-Space Network Is Alive

An anonymous reader writes "The first public white space network officially launched on Wednesday in Claudville, Virginia. It uses sensing technology from Spectrum Bridge with software and Web cams supplied by Microsoft and PCs from by Dell. The project was funded the TDF Foundation. White space networks use unlicensed television spectrum and have been called 'WiFi on steroids.' They offer more bandwidth, over larger areas, than does WiFi. IT companies duked it out with broadcasters for years to get white spaces approved by the FCC. They finally got the FCC's nod in November, 2008."

Comments

Is this statement misleading?

[t0qer]

have been called 'WiFi on steroids.' They offer more bandwidth, over larger areas, than does WiFi.

Someone correct me if I'm mistaken, but doesn't lower frequency (30mhz to 300mhz) mean less bandwidth? I could see bonding several channels at once to achieve a higher bandwidth, but doesn't this mostly offer greater range?

Re:Is this statement misleading?

[spottedkangaroo]

It really doesn't matter what frequency when you're talking bandwidth. When you're talking size of the antenna or signal loss the wavelength might matter, but not for bandwidth. The reason you get more bandwidth here is because the spectrum is wider. The ISM spectrum is very very narrow and low power channels all bunched up around 2.4Ghz. With the new white spaces, they can use tons more and much louder. But, yes, they need longer antennas.

As far as the range? You can make a microwave signal go light years and a HAM signal go a few feet (although, there will be some distortion for transmitting a signal over a distance shorter than the wavelength). The range is more of a function of signal power.

Re:Is this statement misleading?

[slifox]

I think the OP was referring to data transfer bandwidth (the throughput, or data rate), rather than the traditional electronics use of "bandwidth" (referring to the width of the transmitted signal in the frequency spectrum; though "channel width" is a more exact term).

Of course higher carrier frequencies don't have a higher bandwidth, because bandwidth is a property of the whole system, including the data signal and modulation method. You can make the bandwidth as big or small as your system's constraints allow (e.g. one constraint might be to keep most of your transmitted power inside the allocated bandwidth).

If your data signal is modulated in the exact same manner regardless of the carrier, varying the frequency of the carrier will not affect the transmitted signal's bandwidth. The carrier frequency imposes the upper limit on the data signal's frequency, and thus a higher carrier frequency will theoretically allow for a high data rate.

Practically, however, the data signal is almost always much smaller than the carrier signal, and the transmitted frequency is subject to many other important factors such as noise, signal propagation through the environment, etc... In the case of 2.4GHz vs. 800MHz carrier frequencies, there is no practical gain in potential data rate.

This is all based on my limited understanding of communication theory. Please correct me and/or provide further details if possible!

Re:Is this statement misleading?

[evilviper]

As far as the range? You can make a microwave signal go light years and a HAM signal go a few feet (although, there will be some distortion for transmitting a signal over a distance shorter than the wavelength). The range is more of a function of signal power.

You're horribly wrong.

Distance has everything to do with frequency. You aren't going to have shortwave/ham radio skipping around the world with a 2.4GHz transmitter no matter how much power you put into it. Similarly, there's a reason WiFi is popular at 2.4Ghz but the higher 5Ghz band used with the now-forgotten 802.11a standard has been vastly less utilized.

Frequency determines how well a signal will disperse around obstacles, and therefore, whether it will work AT ALL if you don't have 100% line-of-sight between transmitter and receiver.

Re:Is this statement misleading?

[mwilliamson]

Uh, no. Range is not a function of signal power. It more is a function of the overall signal/noise ratio and the sensitivity of the receiver. This includes noise introduced in the transmitter, natural/other noise, and noise introduced in the receiver. An antenna system with gain can both concentrate and attenuate signals, depending on the directivity and where its pointed.

BTW, I got over 1400 miles out of a little 0.3 watt ham signal, but thats no where near as impressive as Earth still being able to receive signals from Voyager 1 and 2 nearly 10 billion miles away. That's impressive.

-Michael

Re:Is this statement misleading?

[niko9]

You can make a microwave signal go light years and a HAM signal go a few feet

Just for clarification, ham radio operators operate in the microwave region as well. They perform EME (earth-moon-earth) using microwave radios with regularity.

Some info here: http://www.dxzone.com/catalog/Operating_Modes/EME/

As a broadcast engineer...

[jjoelc]

while I am personally glad this finally went through... I can vouch for the potential issues this can cause with existing broadcasts. ATSC is so sensitive to multi-path as it is... (and other forms of interference to boot, but I digress) Throwing out a bunch of unlicensed transmitters, borrowing the space between TV stations is a very scary proposition.

Re:Good thing

[perlchild]

Anything will prove "The tragedy of the commons" as it doesn't really need proof at this point. However, expanding the commons is like that. The alternative is a shrinking commons, or actually having enough accountability and imputability that it's not really "the commons" anymore, but some form of public property under private ownership or management. I for one welcome expanding commons.

As for cell bandwidth, the process is so political, it's not really surprising they refuse or fight less for frequencies that are better, and duke it out with google for poorer frequencies. It lets the management say it's all someone else's fault.

It's Obvious Where This is Heading

[segedunum]

Interested parties (whose businesses rely and will expand with cheap or free bandwidth) are angling to use it as a means to get around current mobile operators, and it can't come a moment too soon in many ways as far as I'm concerned. However, I can only see this being a recipe for disaster given the state of many wireless devices and all their broken firmware updates today if it's accurate:

Devices must both consult an FCC-mandated database to determine which channels are available for use at a given location, and must also monitor the spectrum locally once every minute to confirm that no legacy wireless microphones, video assist devices or other emitters are present.

Webcams?

[d0rp]

I'm confused... what do they need webcams for in this project? I actually read the article and it didn't mention what they were for either.

Re:Webcams?

[John Hasler]

The school system is using them for "distance learning". They aren't really relevant to the story.

Re:Webcams?

[HangingChad]

I'm confused... what do they need webcams for in this project?

Live porn. Hey, you have to fill that broadcast schedule with something.

wif fi, that was invented by...

[MrKaos]

The people at the CSIRO wasn't it?

enjoy :-)

Why Claudville?

[molo]

Why Claudville? According to the Wikipedia page, there are around 20,000 people in the entire county. And according to the FCC DTV maps, they can only expect to receive two (!) TV stations, both from the Winston-Salem, North Carolina area. See here: (enter Claudville, VA) http://www.fcc.gov/mb/engineering/maps/

That is perhaps why they are testing it there. Its not hard to avoid active TV channels if there are only two.. and they are on adjacent RF channels (31 and 32).

-molo

Re:Why Claudville?

[Obfuscant]

And according to the FCC DTV maps, they can only expect to receive two (!) TV stations,

You didn't read the "maps" correctly. They are expected to get two STRONG signals, and 6 weak ones. The weak ones are on UHF 19, 29, 51, 33 and 14.

If the "white space" devices in that area are as capable of reading the maps as you are, those people WILL only get two stations instead of the 8 they might, especially those people who have invested money in good outside antennas so they CAN get the other weak signals.

But they're hicks who don't deserve TV anyway, right?

Re:Why Claudville?

[plover]

Why Claudville?

I'm not from Virginia, you insensitive Claud!

Wifi on STEROIDS!?!!

[Cajun Hell]

Please, think of the example this is setting for the children. Congress should immediately hold hearings about Wifi cheaters.

Re:Good thing

[icebike]

A foot long? Oh come on!!!

We are talking about "700-megahertz" band, covering TV channels 52 to 69 (698 to 806 MHz).

The upper end of this is only marginally longer wavelength than the 850MHz band used for 850-GSM cellular today.

This bandwidth could easily be merged into the cellular spectrum with virtually no change in antenna length required, or at best a marginal increase in length that would easily fit in the modern smart phone package format.

A quarter wave antenna for 850MHz is 3.3 inches.
for 800MHz a length of 3.50 inches is optimal.
for 700MHz 4.01 inches, etc.

The iPhone is 4.25 inches tall. Similar phones have similar sizes, all of which would accommodate a quarter wave for these frequencies.

I don't think that word means what you think it...

[owlnation]

"First Public White-Space Network Is Alive"

I think you mean "live". If it's "alive" we have some real problems ahead of us.

Re:Good thing

[FooAtWFU]

The last Nobel Prize in economics was basically saying, "Hey, a lot of important 'commons' have a small set of people who use them in repeated interactions, and so you can use game theory principles to describe how these people self-regulate the use of the commons. Oh, and therefore the government getting in on the action is less important than it might otherwise be."

It would be interesting to see whether the use of this spectrum white space "commons" will be effective.

Re:Using Television Spectrum

[commodore64_love]

In other news, the residents of Claudville VA are no longer able to watch distant stations in Roanoke due to these internet devices broadcasting over the channels.

The FCC Chairman's comment - "You're not supposed to see out of market stations anyway." One of the local viewers replied, "Now I only get 5 stations from Salem NC, where I used to get 10 from both Salem and Roanoke. They took away my channels."