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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."
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.
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.
Imagine if you weren't allowed to use roads because a bus company complained about your driving 3 times. --skunkpussy
The school system is using them for "distance learning". They aren't really relevant to the story.
Warning: this article may contain humor, sarcasm, parody, and perhaps even irony. Read at your own risk.
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
Using your sig line to advertise for friends is lame.
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.
Sig Battery depleted. Reverting to safe mode.
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!
"First Public White-Space Network Is Alive"
I think you mean "live". If it's "alive" we have some real problems ahead of us.
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.
Slashdot gets worse every day... Pipedot: News for nerds, without the corporate slant
It would be interesting to see whether the use of this spectrum white space "commons" will be effective.
The World Wide Web is dying. Soon, we shall have only the Internet.
I'm confused... what do they need webcams for in this project?
Live porn. Hey, you have to fill that broadcast schedule with something.
That's our life, the big wheel of shit. - The Fat Man, Blue Tango Salvage
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/