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TV White Space & The Future of Wireless Broadband

Posted by CmdrTaco on from the something-to-think-about dept.

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."

29 of 119 comments (clear)

  1. Time Warner is going to just love this idea by elrous0 · · Score: 5, Insightful
    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

    --
    SJW: Someone who has run out of real oppression, and has to fake it.
  2. Great, another choice for those who have lots by professorguy · · Score: 2, Interesting
    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.

    1. Re:Great, another choice for those who have lots by ThinkingInBinary · · Score: 2, Funny

      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.

      --
      ttuttle is a rankmaniac
    2. Re:Great, another choice for those who have lots by adamjgp · · Score: 2, Insightful

      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.

    3. Re:Great, another choice for those who have lots by anglete · · Score: 2, Insightful

      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?)

    4. Re:Great, another choice for those who have lots by wampus · · Score: 2, Funny

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

    5. Re:Great, another choice for those who have lots by paganizer · · Score: 2, Interesting

      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.

      --
      Why, yes, I AM a Pagan Libertarian.
    6. Re:Great, another choice for those who have lots by Forseti · · Score: 3, Informative

      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...

      --
      Delay is preferable to error. (Thomas Jefferson)
    7. Re:Great, another choice for those who have lots by bmwm3nut · · Score: 2, Informative

      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).

  3. My friend who works at the FCC lab sez... by Anonymous Coward · · Score: 2, Interesting

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

  4. Whitespace? by TimeTraveler1884 · · Score: 5, Funny

    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!

    1. Re:Whitespace? by KutuluWare · · Score: 2

      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
  5. Low power? are they kidding? by LM741N · · Score: 2, Insightful

    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.

    1. Re:Low power? are they kidding? by link5280 · · Score: 2, Insightful

      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.

      --
      Iraq billions
  6. P2P free decentralized internet by Anonymous Coward · · Score: 2, Interesting

    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.

  7. Practical value? by Firehed · · Score: 5, Funny

    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.

    --
    How are sites slashdotted when nobody reads TFAs?
    1. Re:Practical value? by TimeTraveler1884 · · Score: 5, Funny

      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."
    2. Re:Practical value? by jonesy16 · · Score: 4, Interesting

      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?

    3. Re:Practical value? by GreggBz · · Score: 2, Informative

      Currently, DOCSIS cable modems use a TDMA 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. 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.

    4. Re:Practical value? by Overzeetop · · Score: 2, Interesting

      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.

      --
      Is it just my observation, or are there way too many stupid people in the world?
  8. Why are we running out? by cfulmer · · Score: 3, Insightful

    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.

    1. Re:Why are we running out? by TimeTraveler1884 · · Score: 2, Informative

      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.

    2. Re:Why are we running out? by link5280 · · Score: 3, Informative

      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.

      --
      Iraq billions
    3. Re:Why are we running out? by infinity314159 · · Score: 2, Informative

      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

    4. Re:Why are we running out? by frieko · · Score: 3, Informative

      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.

  9. Re:Does "white space" last forever? by Ephemeriis · · Score: 4, Informative

    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.
    --
    "Work is the curse of the drinking classes." -Oscar Wilde
  10. Superhet by tepples · · Score: 2, Informative

    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, create weak incidental emissions at any of several intermediate frequencies. In countries with a TV licence, those responsible for enforcing licence compliance drive vans carrying equipment to detect these emissions.
  11. Why not force internet into the VHF-Low TV band? by knorthern+knight · · Score: 2, Interesting

    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.

    --

    I'm not repeating myself
    I'm an X window user; I'm an ex-Windows user
  12. Re:[AC]Just because you don't get TV channels by everphilski · · Score: 2, Interesting

    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)