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TV White Space & The Future of Wireless Broadband

CmdrTaco posted more than 6 years ago | from the something-to-think-about dept.

Wireless Networking 119

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."

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119 comments

Time Warner is going to just love this idea (5, Insightful)

elrous0 (869638) | more than 6 years ago | (#22234018)

With companies like Time Warner, who are both broadband providers and important content producers for broadcast TV, is there any doubt where the broadcast TV companies are going to come down on this "interference" issue?

I can hear it now:

Broadcast TV: Senator, this new scheme causes huge interference with our broadcast signal
Senator: This wouldn't have anything to do with Time Warner giving you the broadcast rights to a bunch of their movies and TV shows for a song, would it?
Broadcast TV: Don't be silly. We can answer any other questions you may have at the campaign fundraiser we're holding for you tonight.
Senator: I think I'm beginning to appreciate your point of view.

-Eric

Re:Time Warner is going to just love this idea (1)

Russell2566 (1205416) | more than 6 years ago | (#22234528)

I live in an area where Time Warner is extremely dominant. They spend a lot of money at the local level to make sure that companies like Verizon can't bring in competing products... They also drop their prices in areas where competing products are available and raise them in places where they are not....

Re:Time Warner is going to just love this idea (1)

SoulRider (148285) | more than 6 years ago | (#22235956)

Damn, O'Reilly could just cut/paste this into a book and call it "Politics in a Nutshell"

Great, another choice for those who have lots (2, Interesting)

professorguy (1108737) | more than 6 years ago | (#22234036)

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 (0)

Anonymous Coward | more than 6 years ago | (#22234056)

Get Netflix! Problem solved.

Re:Great, another choice for those who have lots (2, Funny)

ThinkingInBinary (899485) | more than 6 years ago | (#22234064)

Wow, way to RTFA. "White space" technology transmits in the gaps between broadcast TV channels. If anything, you have more potential bandwidth available than those who live in a city where many TV channels are used.

Re:Great, another choice for those who have lots (1)

SQLGuru (980662) | more than 6 years ago | (#22234156)

So, my new hobby will be using my old analog TV to watch your porn bits flying through the air.....please view more ascii porn, it will be easier for me to see.

Layne

Re:Great, another choice for those who have lots (1)

simong (32944) | more than 6 years ago | (#22235042)

Weeeellll, no. You need transmitters to provide that whitespace in the first place, and they ain't there in the places that the OP is talking about. A place that immediately springs to mind is Pocohontas County in WV, which is a radio and TV deadzone because of the National Radio Quiet Zone. There is a single low powered AM radio station in the area and Verizon has a monopoly on cable TV, phones and broadband. It isn't going provide any advantage there.

Re:Great, another choice for those who have lots (3, Informative)

Forseti (192792) | more than 6 years ago | (#22235368)

Why would you need transmitters to provide whitespace? Whitespace is a range of frequencies where nobody transmits. Just because that whitespace is there even when there's a transmitter doesn't mean that it's provided by said transmitter! You do need a separate transmitter to provide this new service in those whitespaces, but that has nothing to do with the presence or absence of existing transmitters. Plus, at those frequencies, a transmitter could more easily provide service to rural areas, so it might indeed help people who have no other broadband options.

And no, you can't count on a wireless technology to help people living in a radio quiet zone. That's the kind of thing someone could (should) find out about and consider before buying property there. In any case, a quick search on the NRQZ seems to indicate that it is not, in fact, a deadzone. There are merely more requirements and restrictions for anyone wanting to place a transmitter there...

Re:Great, another choice for those who have lots (1)

bluephone (200451) | more than 6 years ago | (#22235412)

Well that's a valid argument. The only place on earth that by gov't fiat is radio quiet and patrolled by radio detectors can't use this new braodband scheme so let's trash the whole idea.

Re:Great, another choice for those who have lots (1)

Isauq (730660) | more than 6 years ago | (#22235620)

You don't go to Pocahontas for the broadband and don't live there if you don't like roughing it at some level. Really, unless you're working at Green Bank or Snowshoe, I can't see why you would live there in the first place...

Re:Great, another choice for those who have lots (2, Insightful)

adamjgp (1229860) | more than 6 years ago | (#22234456)

Clearly businesses want to serve the least populated areas of the country. It is in their best interests to serve the least amount of people, usually with the lowest amount of disposable income. /sarcasm If you don't like your choices of broadband and TV, then I suggest either reading more, or moving.

Re:Great, another choice for those who have lots (2, Insightful)

anglete (782289) | more than 6 years ago | (#22234478)

I think this is actually great for rural areas. Most rural areas do receive TV signals. Some may not, but get broadband everywhere one step at a time.

I'm somewhat confused how the return will work (everybody has a tv station to broadcast with on their roof?)

Re:Great, another choice for those who have lots (2, Interesting)

paganizer (566360) | more than 6 years ago | (#22234708)

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.

Re:Great, another choice for those who have lots (1)

maxume (22995) | more than 6 years ago | (#22234514)

Is satellite not an option? Or is it not an option because you aren't interested in paying for it?

Anyway, I'm in what is pretty much a rural area(I'm several miles from the nearest 'city', which is really more of a town, there is a village that is closer, but it is still several miles away). I'm about 2 miles from a broadcast tower. So this solves the problem for me and my neighbors.

Re:Great, another choice for those who have lots (2, Funny)

wampus (1932) | more than 6 years ago | (#22234610)

Satellite's latency is horrible. Light isn't nearly as fast as it seems.

Re:Great, another choice for those who have lots (1)

LynnwoodRooster (966895) | more than 6 years ago | (#22234970)

But is the latency slower than connecting at 26 kbps? I'll take a 500 msec latency hit if my average throughput is 200 kbps, rather than 26 kbps with 50 msec latency. Maybe I can't game, but I can get a ton more information and overall throughput.

Re:Great, another choice for those who have lots (2, Informative)

bmwm3nut (556681) | more than 6 years ago | (#22235612)

I have satellite (Base package from WildBlue), so here are some numbers. Latency (measured by pings to google.com) measures about 1200-1600ms. Throughput (measured by downloading an Ubuntu .iso from mirrors.kernel.org) is about 60kbps. It's not bad, but it's not great either. My only other option where I live is $300/mo for a T1, which I think I'll be doing once my satellite contract runs out (and my wife lets me).

Re:Great, another choice for those who have lots (1)

LynnwoodRooster (966895) | more than 6 years ago | (#22236348)

Thanks for the numbers! So it looks like it could be a case of 10X the latency or 1/3rd the bandwidth... I guess it comes down to what you're doing on the net.

Re:Great, another choice for those who have lots (1)

BigwayneO (1229884) | more than 6 years ago | (#22234696)

true, my parents live out in the boondocks and my dad does ALOT of stuff on ebay (grease monkey he is)and the such, and his connection runs at like 25 kbps, he has been thinking about getting the sat. internet, but that costs so much, and really is not worth the money, but he has no other options... i hope one day some broad band company will figure something out....

Just because you don't get TV channels (1)

everphilski (877346) | more than 6 years ago | (#22234866)

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

Just because you don't get TV channels DOES NOT mean this won't work for you. It depends on bandwidth and encoding.

For example, in amateur radio, when voice communications are insufficient, Morse code (much narrower badwidth) tends to work over great distances, and when Morse doesn't work a digital mode like PSK31 (narrower) works even better, and often at lower powers.

It will really come down to the bandwidth and power output, it always does :) But just because you don't get TV (which is very wide bandwidth, analog video and voice) doesn't mean you won't get a digital internet connection.

VHF/UHF is the way to go (1)

Bananatree3 (872975) | more than 6 years ago | (#22235356)

I am an amateur radio operator and can attest to how easy working with VHF/UHF is on a small scale level. A 100watt VHF "repeater" on a tall hill can usually be reached 20-30 miles away with a 5 watt handheld radio and line-of-sight, and much less power for towers closer. Multipath is a problem, like anything else. Nonetheless, if the towers are properly placed so that line-of-sight is maximized (i.e. they do their homework), I have no doubt you would be able to work it with a PCMCIA laptop card and a small antenna off of it. Of course the wider the bandwidth signal the more power needed, however VHF is magnitudes better for long distance than 2.4GHz.

Re:Great, another choice for those who have lots (1)

The Cisco Kid (31490) | more than 6 years ago | (#22235382)

Guess what? NLOS, low-power, high-bandwidth wireless technology will make it *much* more cost-effective for regional ISP's to offer service in rural areas. Right now the telco and the cableco doesnt care about rural becuase there just isnt enough density to make it profitable for them to run cable. Broadband wireless with the range of TV and without the LOS requirement will make it much easier. Plus, without the monopoly control that telco/cable has with their wires, there might actually be some competition. Of course, due to that, I predict the telco/cable wont be interested in playing, but trust me, independent ISP's would *love* to have an easy way to get broadband to both people unserved by the monopolies, as well as the underserved (eg, treated like cattle with open wallets)

Re:Great, another choice for those who have lots (1)

Teflon_Jeff (1221290) | more than 6 years ago | (#22235706)

There are a lot of areas that have OTA TV channels without any broadband options. some people still have no options, but this does open up a lot of options for those who had none. farmers are a big one, my in-laws have this exact problem. But they can get OTA. Small townships could also benefit. heck, long-term, more competition lowers prices, and should see more expansion of DSL/Cable lines as well.

white space (-1, Offtopic)

rucs_hack (784150) | more than 6 years ago | (#22234058)

So If I start the code in a function one line down from the opening bracket I can get broadband in it?

Wow, Vim can do more than I thought.

My friend who works at the FCC lab sez... (2, Interesting)

Anonymous Coward | more than 6 years ago | (#22234072)

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

Does "white space" last forever? (1)

threeturn (622824) | more than 6 years ago | (#22234080)

The problem with this idea is that it assumes that TV broadcasting will always be done the way it is today with unused space between the channels. If "white space" equipment gets deployed it is going to create a massive problem for any attempts to change use of the existing TV spectrum. Any future users of this spectrum are going to have to work around the applications now running in what used to be the "white space".

Re:Does "white space" last forever? (4, Informative)

Ephemeriis (315124) | more than 6 years ago | (#22234540)

The problem with this idea is that it assumes that TV broadcasting will always be done the way it is today with unused space between the channels. If "white space" equipment gets deployed it is going to create a massive problem for any attempts to change use of the existing TV spectrum. Any future users of this spectrum are going to have to work around the applications now running in what used to be the "white space".
If I understand correctly, part of what this device does is detect television signals and avoid spectrum that is actually being used. That is part of what is being tested. The idea is that these devices would be allowed to transmit over fairly large chunks of the spectrum, but that they would automatically detect what is actually being used for television and only transmit in the gaps between channels. That is why there's so much concern about these devices causing interference - nobody is sure how well this detection/avoidance mechanism is going to work.

If it does actually work like it is supposed to it won't matter if the white space between channels moves or vanishes - the device will stop using that chunk of spectrum and move to another. The only real problem you'd have is if you completely saturated the spectrum with television, which could happen. But in that case the devices would simply be unable to find any white space and would not be able to transmit - it wouldn't actually interfere with the television broadcast.

That's how it's supposed to work, at least.

Re:Does "white space" last forever? (1, Informative)

Anonymous Coward | more than 6 years ago | (#22235688)

Between broadcast channels is a padding space meant to shield adjacent channels from sub-standard broadcasting equipment that might cause a frequency drift.
This is called whitespace, unused frequencies between channels to minimize collisions. Like airplanes keeping a couple mile buffer zone between each other, to prevent a bad pilot from accidentally colliding with another plane.

So even if every channel is used, there will still be some space left to squeeze a datastream into. And if this thing works as intended, shifting from bad broadcasters will be accommodated. If a broadcast starts drifting into other frequencies, this would back out of those and jump into the newly opened space on the other side of the broadcast.

Re:Does "white space" last forever? (1)

RicktheBrick (588466) | more than 6 years ago | (#22236814)

We need to subsidize fiber to every home in this country and leave the radio spectrum to mobile devices. The cost could be justified very easily by the added security and cost reductions(fire, law enforcement, and medical).

Re:Does "white space" last forever? (1)

imgod2u (812837) | more than 6 years ago | (#22235608)

This is the reason why the FCC exists and has the ability to "grant" who and what can use what spectrum. When the white space spectrum is sold, broadcasters who use it now for TV will be required by law to stop broadcasting. If Google has their way, an open standard will be developed on how to "share" this spectrum. All devices will then have to conform to this standard to use that spectrum so that they play nice with each other.

Towers that currently broadcast TV will have 2 options. Either they stop service or they start broadcasting using the new digital protocol standard. People will have to buy new antennas to receive and decode this signal for their TV. I believe the government has offered a rebate for people of low-income to get these antennas for cheap.

Really though, I don't see the need for rebates. The market will adjust. If people who watch Jerry all of a sudden can't do it anymore, they'll go out and try to buy a new antenna. They'll obviously go towards the one that's cheapest and still works and competition will drive prices down. The rebate thing reeks of "let's not piss people off" mentality but, like the rest of our rent-a-congress, fails to understand that in the long run, government interference = bad for the market.

Why is it called "white" space? (1, Funny)

niceone (992278) | more than 6 years ago | (#22234114)

Surely it's black if there's nothing there? Doesn't "white" mean filled with all kinds of frequencies, as in white noise? I suppose if you think of the spectrum as a sheet of paper...

Re:Why is it called "white" space? (1)

LordPhantom (763327) | more than 6 years ago | (#22234170)

Well.... tere's -lots- of background radiation, etc. If anything, it's more of a "grey".

Re:Why is it called "white" space? (1)

squiggleslash (241428) | more than 6 years ago | (#22234236)

Well, if you can find a TV that tunes to one of those frequencies rather than blanking it with a blue screen (WTF? Why do they make TVs that do that?), then you'll hear and see plenty of white noise, as you're picking up lots of background radiation.

Re:Why is it called "white" space? (1)

lju (944654) | more than 6 years ago | (#22234366)

Because it has nothing to do with white noise. It's analogous to the space between different sections of a document, if printed on white paper, those spaces are "white spaces."

Re:Why is it called "white" space? (1)

AvitarX (172628) | more than 6 years ago | (#22234488)

They probably blank the screen because when I was little we used to watch scrambled spice channel (with fairly clean audio anyway). The scrambled channels now turn blue, the internet came out, and the children are safe.

Re:Why is it called "white" space? (1)

TheRaven64 (641858) | more than 6 years ago | (#22235680)

Surely it's black if there's nothing there?
Not for television. Strong signal means black. weak signal means white. If there is absolutely no signal, it's white.

Whitespace? (5, Funny)

TimeTraveler1884 (832874) | more than 6 years ago | (#22234208)

I think this is a bad idea. If we start transmitting data in whitespace, words will become very difficult to distinguish from each other in any given sentence. For example "The quick red fox jumped over the brown lazy dog." by itself, is very readable. But once you transmit extra data in the whitespace it becomes: "The1quick0red1fox0jumped1over0the0brown1lazy0dog." - An invariable piece of shit. It's only a matter of time before the greedy providers decide they need more bandwidth and bleed over in to the primary data stream.

Now if we were to transmit in the margins or between the lines, that may just work!

Re:Whitespace? (2)

KutuluWare (791333) | more than 6 years ago | (#22234484)

Now if we were to transmit in the margins or between the lines, that may just work!


I have discovered a most remarkable way to accomplish this, but the proof won't fit in the margin.

--K

Low power? are they kidding? (2, Insightful)

LM741N (258038) | more than 6 years ago | (#22234218)

Are they planning to have repeaters all over the place like the public wifi? If not they are going to need a lot of power. Some UHF TV stations run with a megawatt of RF. Its especially true in cities where the buildings create multipath distortion and/or block the signals entirely.

Re:Low power? are they kidding? (2, Insightful)

link5280 (1141253) | more than 6 years ago | (#22234412)

The amount of power will depend on the bandwidth and the distance to repeaters or hubs. The infrastructure would have to be similar to a cell phone network, not a single tower servicing an entire metropolitan area like the current TV broadcast system. If the power can remain low and the infrastructure designed correctly it will work, otherwise it would be a flop with consumers. No one wants to carry around a 500 watt device to communicate.

Re:Low power? are they kidding? (1, Insightful)

Anonymous Coward | more than 6 years ago | (#22235926)

Considering the client has to respond to the incoming signal, it needs to be low power. If not, the client cannot respond with his/her 12-50mW signal. So yes, they would need repeaters, but honestly, not many (or at least a reasonable amount, considering the number of repeaters for DSL). A bigger issue would be the antenna requirements for the clients.

Awesome! (1)

n3tcat (664243) | more than 6 years ago | (#22234224)

So with these wavelengths that can travel through walls much more easily, my internet will go down due to interference from my neighbor's automated channel search on his off-brand Korean knock-off TV?

I wonder though if this sort of technology could allow your wireless internet card to double as a wireless tv card. The same modem would take the cable data and broadcast the entire band and your computer would just sort out the data on it's end.

Re:Awesome! (1)

calebt3 (1098475) | more than 6 years ago | (#22234344)

my internet will go down due to interference from my neighbor's automated channel search on his off-brand Korean knock-off TV
Why would it do that? Your neighbor's device has no need to transmit anything.

Superhet (2, Informative)

tepples (727027) | more than 6 years ago | (#22235084)

Your neighbor's device has no need to transmit anything.
But it does anyway. Some methods of tuning into radio-frequency transmissions, such as superhet [wikipedia.org], create weak incidental emissions at any of several intermediate frequencies [wikipedia.org]. In countries with a TV licence [wikipedia.org], those responsible for enforcing licence compliance drive vans [bbc.co.uk] carrying equipment to detect these emissions.

Re:Awesome! (1)

imgod2u (812837) | more than 6 years ago | (#22235698)

I wonder though if this sort of technology could allow your wireless internet card to double as a wireless tv card. The same modem would take the cable data and broadcast the entire band and your computer would just sort out the data on it's end.
This is already true of (many) wired services. Verizon FIOS transfers both TV data and internet over the same fiber line. It's just a matter of routing different types of data and separating the different type of frames.

I would assume that the new wireless protocol will have a standard physical and MAC layer for everything that runs across it.

P2P free decentralized internet (2, Interesting)

Anonymous Coward | more than 6 years ago | (#22234228)

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:P2P free decentralized internet (1)

esocid (946821) | more than 6 years ago | (#22237124)

Sounds kinda like a variation on Tor [torproject.org] Imagine a commune of internet sharing.

Practical value? (5, Funny)

Firehed (942385) | more than 6 years ago | (#22234252)

TV, unlike the internet, is a one-way medium. My TV may be able to pick up signals from a giant transmitter thirty miles away, and that's great. How would this work for internet connections? Something tells me that putting an antenna powerful enough to reach back to that tower inside my laptop isn't going to be too friendly with my battery life, let alone my non-shielded nuts.

Re:Practical value? (5, Funny)

TimeTraveler1884 (832874) | more than 6 years ago | (#22234376)

antenna powerful enough to reach back to that tower inside my laptop isn't going to be too friendly with my battery life, let alone my non-shielded nuts.
It's nothing to worry about. From the FCC site: "Between January 1, 2008, and March 31, 2009, all U.S. households will be able to request up to two coupons, worth $40 each, to be used toward the future purchase of eligible testicle and ovary shields. Eligible testicle and ovary shields are for the conversion of non-shielded testicles and ovaries, and therefore are not intended for anuses connected to a paid provider such as cable or satellite TV service."

Re:Practical value? (-1)

ethicalBob (1023525) | more than 6 years ago | (#22234390)

one problem with that; After 2009(?) you won't have broadcast TV after everything has gone digital. If you want to watch TV, you WILL either have cable or satellite, both of which provide easy 2-way communication.

Re:Practical value? (1, Informative)

Anonymous Coward | more than 6 years ago | (#22234464)

Huh? After the switch in 2009, you'll just need a fancy new tuner to get your broadcast. No cable or satellite needed.

Re:Practical value? (1)

prencher (971087) | more than 6 years ago | (#22234516)

Wrong.. It's just digital broadcasting. You need a new tuner and nothing else; Nothing to do with satellite or cable.

Re:Practical value? (1)

AvitarX (172628) | more than 6 years ago | (#22234558)

You mean the digital OTA TV I am watching now will go blank?

I spent some extra money making sure I got a TV that could receive digital OTA. It comes in crisp and in HD, I will miss it.

Or maybe it is just analog broadcast that is going away?

Re:Practical value? (4, Interesting)

jonesy16 (595988) | more than 6 years ago | (#22234392)

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? (1)

archDC (1229900) | more than 6 years ago | (#22235026)

I don't think it would be that hard to transmit back. Think of your cell phone. It transmits miles away from a small, low power device. Something similar, if not identical could be used. Kind of like dish broadband, you send information by telephone line, you could send information across cellular frequencies.

Re:Practical value? (1)

zigziggityzoo (915650) | more than 6 years ago | (#22235044)

Maybe like a cell phone? Last i checked, no one's got a backpack radio transmitter just to make a phone call. Cell towers pump out a good amount of juice, too, and cell phones seem to be able to talk back to them.

Re:Practical value? (1)

meatspray (59961) | more than 6 years ago | (#22235718)

They could use the cellphone data network for the uplink.
the cell companies are mostly worried about broadband throughput, if they could provide 128 up, the system would be passible
 

Re:Practical value? (2, Interesting)

Overzeetop (214511) | more than 6 years ago | (#22235056)

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.

Re:Practical value? (1)

TooMuchToDo (882796) | more than 6 years ago | (#22236128)

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.

Don't be so sure. If a progressive carrier *ahem* T-Mobile *ahem* saw limited use of their data network, I'm sure they'd partner with someone to provide the uplink if it would make them some cash.

Never underestimate the power of the .

Re:Practical value? (1)

TooMuchToDo (882796) | more than 6 years ago | (#22236162)

Never underestimate the power of the *your-choice-of-currency-here*. (damn Slashdot and it's HTML filtering)

Re:Practical value? (2, Informative)

GreggBz (777373) | more than 6 years ago | (#22234694)

Currently, DOCSIS cable modems use a TDMA [wikipedia.org] scheme for return traffic. (Basically, divide the wavelengths up into "time slots" and each modem gets a certain time slot. The signal is generally modulated using 16-QAM. [wikipedia.org] Think of two waves offset by 90 degrees, one vertical and one horizontal. Add to that 2 levels of amplitude for each wave. So, you can have 16 combinations. Or 4 bits for each wavelength of signal. You can increase the numbers of levels of different amplitude to increase your possible bit combinations per wavelength, but this is risky and few cable companies actually do it.

With this system running in the typical 25-35Khz frequency, you can have enough time slots for 400-600 modems, and about 7Mb of shared traffic.

To me, it's amazing they can build silicon to distinguish 500 different cable modems within microseconds. Kind of like what really happens in a Pentium IV.

But, this stuff is susceptible to noise and it can become hard to tell what bits are meant to be on the line if there's enough noise.

It's a good model, but I have no idea how you do it over the air, unless you increase the signal so high that the noise floor drowns out. But then jets would fall from the sky and we'd all get throbbing headaches.. or something.

Re:Practical value? (1)

realmolo (574068) | more than 6 years ago | (#22234800)

Remember that a giant antenna is a great *receiver* as well as a great *transmitter*. An enormous UHF TV antenna is going to be able to pick up some very weak signals.

Besides, how do you think your cell phone works? You have a tiny little phone, but it can talk to towers that are many miles away without issue.

Re:Practical value? (1)

mdvandam (1229908) | more than 6 years ago | (#22235058)

I don't -cancer- think this could be a -sarcoma- good idea. We need more -leucemia- cable connections and less -tumor- wireless.

Spectrum auction (1)

Wireless Joe (604314) | more than 6 years ago | (#22234264)

Why do these companies get to use this spectrum for free, when the telcos, cable operators, Paul Allen, etc. are currently bidding billions for similar frequencies? That last sentence should read:

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 for free."

Why are we running out? (3, Insightful)

cfulmer (3166) | more than 6 years ago | (#22234276)

Isn't there just as much bandwidth between 3Ghz and 4Ghz as there is between 0Ghz and 1Ghz? Why do we carve out larger chunks at higher frequencies? It seems to me that the real answer is finer-grained transmitters and receivers.

Re:Why are we running out? (2, Informative)

TimeTraveler1884 (832874) | more than 6 years ago | (#22234494)

There is actually more bandwidth between 3GHz and 4Ghz than 0Ghz and 1Ghz. Say you were to pick 100mhz wide channel right in between those ranges. 3.5ghz has 7 times the amount of cycles/sec than 500mhz. So assuming PCM and no losses, that's 7 times the bandwidth.

Re:Why are we running out? (0)

Anonymous Coward | more than 6 years ago | (#22234608)

You are confusing wavelength (cycles) with bandwidth, both have 1 GHz of available bandwidth. I would agree the 3 GHz to 4 GHz range is more useful though.

Re:Why are we running out? (1)

TimeTraveler1884 (832874) | more than 6 years ago | (#22234640)

Perhaps I am. But if each cycle is a potential bit, then it seems that there is more information carrying capacity at the higher frequencies. Maybe bandwidth is the wrong word for what I am saying?

Re:Why are we running out? (2, Informative)

infinity314159 (1109701) | more than 6 years ago | (#22234724)

No, information carrying capcity, (also referred to as "bandwidth" confusingly), is proportional to the analog frequency range, (which was the original "bandwidth" concept). Check the wikipedia article. There are physics-related reasons for this, but I'm not that much of a physicist: http://en.wikipedia.org/wiki/Bandwidth [wikipedia.org]

Re:Why are we running out? (1, Informative)

Anonymous Coward | more than 6 years ago | (#22235080)

That is usually not a limitation because it's based on the carrier frequency the data is being placed on along with the modulation techniques in use. Using some cool modulation schemes I can put 2Gbps of data onto a 1 GHz carrier and the cycle rate is not a factor. Remember there is a difference between the data rate and the symbol rate (actually changes to the sine wave). A 2 Gbps digital signal can equate to a much smaller symbol rate based on the modulation in use. Many cable modems use either a 16 QAM or 32 QAM, so 8 or 16 bits are represented in a single phase shift for any given sine wave. For example, a 2 Gbps data rate using 16 QAM only uses 250 MHz of spectrum. I say "only", 250 Mhz is a huge amount of the spectrum, but you get the idea. Additional note, the limitations on the various frequency spectrums is not technology limited but regulation limited to prevent interference. We have to transmit in perfect harmony :) http://en.wikipedia.org/wiki/Symbol_rate [wikipedia.org] http://en.wikipedia.org/wiki/Gross_bit_rate [wikipedia.org] http://en.wikipedia.org/wiki/Quadrature_amplitude_modulation [wikipedia.org]

Re:Why are we running out? (1)

shadow_slicer (607649) | more than 6 years ago | (#22236388)

The key is that each of those cycles is *not* a potential bit. Radio communication is inherently different from RS232 or other simple wired standards (the newer ones are more complicated and borrow quite a bit from techniques developed for radio).

The primary difference is that bandwidth is limited. This means that you can't use every cycle. In the simplest case (ASK) you take the signal you want to transmit (which would be similar to your 800baud RS232 signal), and then remove the high frequency components so that the highest remaining frequency component is less than 1/2 the bandwidth. This will smooth all the edges out of your nice neat pulses, making them much more difficult to identify =(. Then we need to mix (multiply) this signal with the carrier frequency (located in the middle of your available bandwidth), and out pops the signal you want to transmit (centered around the carrier frequency).

Or mathematically:

s[n] = (bit == 1) ? 1 : -1;
s(t) = s[n*bitrate] at time n*bitrate < t < (n+1)*bitrate
x(t) = all frequency components of s(t) with frequency less than Bandwidth/2; //Low Pass Filter
y(t) = x(t)cos(2*pi*CarrierFrequency*t)

Then transmit y(t)

Re:Why are we running out? (1)

infinity314159 (1109701) | more than 6 years ago | (#22234650)

That's not how it works. There is the same amount of bandwidth in the 0-500 MHz range, as there is in the 3.5-4.0 GHz range. That's why they call it "bandwidth."

Re:Why are we running out? (1)

link5280 (1141253) | more than 6 years ago | (#22235410)

I will use my football analogy, you are 110% correct. People are confusing wavelength with bandwidth.

Re:Why are we running out? (1)

Flunitrazepam (664690) | more than 6 years ago | (#22234920)

There is actually more bandwidth between 3GHz and 4Ghz than 0Ghz and 1Ghz. Say you were to pick 100mhz wide channel right in between those ranges. 3.5ghz has 7 times the amount of cycles/sec than 500mhz. So assuming PCM and no losses, that's 7 times the bandwidth.

Physics called, he wanted you to know you're doing him wrong

Re:Why are we running out? (3, Informative)

frieko (855745) | more than 6 years ago | (#22235618)

Nope. You're counting everything from 0 to 3.5gHz as your "3.5gHz band". That's a 3.5 gHz channel, not a 100mHz channel.

When you want to send a signal on a 100 mHz wide channel, you would first construct a signal that uses frequencies between 0 and 100 mhz. Then you can shift it up by 450 mHz and get a 100mHz channel centered at 500 mHz, or shift it up by 100 gHz to each frequency and get a 100 mhz channel centered at 100.05 gigahertz. But it's still the same bandwidth and capacity.

Re:Why are we running out? (3, Informative)

link5280 (1141253) | more than 6 years ago | (#22234530)

Higher frequencies get attenuated by walls, rain, trees, etc... more easily than the lower ones. Yes the higher frequencies have more available bandwidth but there are disadvantages. TFA mentions the pros of using the UHF and VHF spectrum.

Re:Why are we running out? (1)

raidfibre (1181749) | more than 6 years ago | (#22234612)

3GHz is a fairly high frequency in the microwave region. It won't penetrate walls or the weather very well compared to frequencies 1GHz. This is why your cell phone operates closer to 1GHz.

C-band downlinks, for example, operate between about 3.7 and 4.2 GHz. This is why you can get a satellite dish and point it around at different 'birds' to get different sets of channels. They're very directional. Higher frequencies don't really help you if you're trying to cover a wide area. There's plenty of spectrum "available". Look at a chart lately? There are hundreds of sections for aeronautical and maritime mobile, all over the chart.

Re:Why are we running out? (1)

redxxx (1194349) | more than 6 years ago | (#22234822)

Uhh... I was under the impression that finer grained transmitters were exactly what all this whitespace hubbub was about. Because FM is FM, a given carrier frequency uses the adjacent frequencies. To allow stuff to actually work, there is some amount of a required gap between these carrier frequencies. The mandated gap is actually greater than necessary, and this is the white space.

Finer grained transmitters is exactly what TFA is talking about, and it is a fairly real answerer. That, or I'm talking out my bottom, or you know all this and I totally miss the point of your post.

Re:Why are we running out? (1)

anglete (782289) | more than 6 years ago | (#22235280)

Your right, but different frequency ranges have different properties. The 700Mhz range tends to go through walls and such while the 2.4Ghz range (near our friendly microwave frequency) doesn't pass through solid objects as well.

Think of sound. A base speaker goes through walls etc. while a high frequency sound can be blocked by your hand being put right in front of the speaker.

Re:Why are we running out? (1)

Lunhil (1063882) | more than 6 years ago | (#22235416)

At high frequencies radio waves take on the properties of light waves. They just bounce off of stuff rather than go through it. 3 and 4 GHz needs line-of-sight to really work well. The lower frequencies, such as VHF television, propagate much better through materials and depend a little less on line-of-sight. It would work better over longer distances.

Re:Why are we running out? (0)

Anonymous Coward | more than 6 years ago | (#22235874)

Dibs on the bandwidth from 0 to minus infinity GHz. Ha! Nobody thought of that. And I'll patent turning the antenna upside down to receive the negative frequencies - I'll be rich, rich beyond my wildest dreams! Ha-ha-haaa!

Having doubled the spectrum at a stroke, for my next trick, I'll grab all the imaginary frequencies, and the technique of turning the antenna sideways to receive those. Where will it end! Anyone for quaternion defined frequencies?

Channel Bandwidth (1)

link5280 (1141253) | more than 6 years ago | (#22234468)

As part of the migration of U.S. TV stations to digital transmission technology, between 12 and 40 unused channels
Anyone know the bandwidth of these "White spaces"

Re:Channel Bandwidth (1)

tepples (727027) | more than 6 years ago | (#22235132)

As part of the migration of U.S. TV stations to digital transmission technology, between 12 and 40 unused channels
Anyone know the bandwidth of these "White spaces"
TV channels in the NTSC/M (USA and Canada), NTSC/J (Japan), and PAL/M (Brazil) systems are 6.0 MHz wide. Most PAL countries use a wider channel.

The commons (0)

Anonymous Coward | more than 6 years ago | (#22234718)

The problem with opening this for personal devices is that we will create another 2.4 GHz mess. 2.4 GHz has become nearly useless in many areas for delivering Internet to people's homes because of the background noise created by home wireless routers, wireless phones, etc. We've been a wireless ISP for 7 years now and seen 2.4 GHz drop in the toilet sinking further every year to the point where it is time to flush. Lets not do this again.

I'm hoping, like 900 MHz the equipment will be too expensive to use for consumer devices.

upload? (1)

Fusen (841730) | more than 6 years ago | (#22234746)

It's been asked at least 3 times in comments on this article yet still no one seems to know the answer to how uploading will work?
anyone?!

Re:upload? (0)

Anonymous Coward | more than 6 years ago | (#22235114)

How will uploading work? Start by understanding that just because a former intra-channel TV frequency is being used, it would have nothing to do with TV broadcast transmissions. So it will work just the same way that wireless does now, just with additional frequencies.

No one will be transmitting at anything like broadcast power, and I doubt any manufacturer will be trying to receive as weak a signal as is done with TV broadcasts.

Why bother with broadcast TV? (1)

boyko.at.netqos (1024767) | more than 6 years ago | (#22235106)

Here's my question. If the spectrum can be used for Internet connectivity, why bother with having the TV over-the-air channels at all?

Re:Why bother with broadcast TV? (1)

Erwos (553607) | more than 6 years ago | (#22235772)

This is basically the same argument as "why have cell phone service? Let's just have TCP/IP data and let people run VoIP over it!", except you'd substitute VoIP for "multicast video streaming". I think, eventually, we'll get there, but one thing at a time.

Re:Why bother with broadcast TV? (1)

imgod2u (812837) | more than 6 years ago | (#22235784)

Because the vast majority of the US population values their daily Jerry Springer more than their daily /. article.

Re:Why bother with broadcast TV? (0)

Anonymous Coward | more than 6 years ago | (#22236076)

Legacy...

With wireless internet, why bother with any other radio signals *at all* when we could just have all of 0-60GHz dedicated to the internet? Because people wouldn't be willing to just drop their cellphones, TVs, radios, etc. They would whine, alot.

Rabbit ears and coat hangers for my computer! (1)

tjstork (137384) | more than 6 years ago | (#22235818)

We have come full circle.

I remember, back when I was a youth, and TV was just over the air, the Sunday afternoon ritual of standing outside with my father during football season, making adjustments to an ever complicated contraption of antenna.

All manners of materials and shapes were experimented on, and my mother would yell, "better", "worse", or, "oh my god", depending on just how our adjustments altered the picture.

Now, my son and I will be standing outside, in the not too distant future, adjusting the antenna as my wife stands by some sort of a bandwidth meter, yelling, "better", "worse", or "oh my god".

Why not force internet into the VHF-Low TV band? (2, Interesting)

knorthern knight (513660) | more than 6 years ago | (#22236356)

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.
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