TV White Space & The Future of Wireless Broadband

DeviceGuru writes "The unoccupied radio spectrum between broadcast TV channels may soon become a source of low-cost, ubiquitous broadband connectivity. Earlier this month, the U.S. Federal Communications Commission began Phase II testing of 'white space device' prototypes, to determine whether WSDs can operate without interfering with the other wireless devices commonly used in homes, offices, and public locations. A key advantage of white space wireless technology, compared to the combination of WiFI and WiMAX, is its TV-like ability to cover broad areas and penetrate walls and trees, using relatively low power levels."

Comments

Great, another choice for those who have lots

[professorguy]

Yes, we need to discover yet another way to deliver high speed internet to people in cities. They don't have enough choices for their broadband.

While we in rural communities who are not served by broadband, can be skipped by another technology. Yeah, TV transmitters will give internet. Too bad there's no TV transmitters around here.

I have no broadband choices (I connect at 26.4kbps) but at least I get 0 over-the-air-channels. All right! Problem solved.

Re:Great, another choice for those who have lots

[paganizer]

Could be like some of the satellite setups; use your phone for upload, TV for download. Most of the VHS/FM internet tests I've seen are really more similar to the way that sat TV works right now, they send out signals, you can choose which one you get, but there isn't really effective two-way communication.
My biggest question, and one that googling doesn't want to answer, is what exactly are we talking about in bandwidth, here?
TTBOMK, a HDTV VHS broadcast has about 25mbs data; thats a pretty respectable chunk, but how many users is that going to be split up for? obviously there is a hard limit to how many of those streams are going to be broadcast.
Is it really going to be broadband, in other words? that, and the return communication aspect do not seem to adequately explained anywhere.

My friend who works at the FCC lab sez...

[Anonymous Coward]

... these tests are open to the public. Why not go and watch?

P2P free decentralized internet

[Anonymous Coward]

Maybe we could find a way to create a p2p wireless internet this way. Get rid of ISPs and make the internet free again like it should be.

There is a whole lot of unused network bandwidth on our personal computers and I know that there are enough neighbors around me that it would be like a bit torrent model of a decentralized internet.

Re:Practical value?

[jonesy16]

You got modded as funny but I think this is the most insightful comment on this page and I was thinking the exact same thing. That's great if we can use TV-like waves to blanket a large area with low power, reasonable bandwidth internet access. But how the hell is the upload signal going to work? My homeowner's associate even tries to prevent us from having TV antennas on our roofs (which is against the law for them to prohibit, but that's another story). But if the signal really is pretty low power, maybe a small return signal can be sent using only a modest sized/powered home antenna, who knows?

Re:Practical value?

[Overzeetop]

While I'm not an RF engineer, the equation is an unbalanced one for down- and uploads. The downlink transmitter must coverer an immense area, whereas the uplink side can be aimed. As a result you can use an extremely high gain directional antenna from your home to the main tower to achieve lower power requirements. There might even be a layered service at several different wavelengths - higher freqs for those with LOS, lower for those without.

Portable devices are more troublesome, but there is the possibility of using the cell phone networks for uplink and TV for downlink. That would, of course, require interoperability and coordination between providers...which we all know would never occur.

Why not force internet into the VHF-Low TV band?

[knorthern knight]

Broadcasters are avoiding channels 2 through 6 when given a choice which channels to select after the digital switchover. There will be almost no TV stations in that band in the USA after Feb 17, 2009 (and in Canada after Aug 31, 2011). That's 30 mhz of usuable frequency space (not counting the 4-mhz gap between channels 4 and 5).

While these frequencies may not be so great for a 6mhz wide TV channel, they're perfectly usable for digital internet. And you're guaranteed no interference with TV, because there won't be any TV stations in that spectrum.

You asked your grandparents why there isn't a channel 1... your grandchildren will be asking you why there aren't any channels 1-through-6.

Re:[AC]Just because you don't get TV channels

[everphilski]

PSK31 uses 31hz of bandwidth.

The formula for CW bandwidth is the bits per second (BPS) times a shape factor, K. CW speed is generally in words per minute, the word "PARIS" is the general word benchmark, 5 letters with 50 bits of information. 50/60 = 0.83 bits/second.

With a shape factor K=4, at 10 WPM (relatively slow), the signal width is about 40hz, wider than PSK31. At 25wpm (what I personally find comfortable) it's about 100hz. More experienced practitioners can speak even faster :)

The shape factor is a function of the wave modulating the carrier ... and in reality could be much higher, or possibly a bit lower.

(this information can be found a number of places, including here)