Google Looks to "White Space" Spectrum

Nerdposeur writes "After maneuvering the major carriers into agreeing to open access rules via the recent spectrum auction, Google appears to be looking into a new area of spectrum that could provide internet connectivity. 'In comments filed with the Federal Communications Commission, the Internet leader outlined plans for low-power devices that use local wireless airwaves to access the 'white space' between television channels. A Google executive called the plan 'Wi-Fi 2.0 or Wi-Fi on steroids.' Interestingly, Google has Microsoft, Intel, and others on their side in this one. Was this spectrum their target all along?"

Comments

Microsoft Device

[Pointy McButterpants]

Is this the same technology that Microsoft has tried to demo (twice) with less-than-spectacular results?

Re:Microsoft Device

[Anonymous Coward]

A rhetorical question is, in fact, a statement of sorts. If this is such a question then it can certainly be insightful or informative - presumably that's how the mods have interpreted it.

Re:Microsoft Device

[Megane]

Woah.

Woah.

Your "weak but still watchable televsion 5" will disappear in 11 months anyhow, before any of this can get implemented. And since channels 2-5 are generally bad for DTV, they will probably keep their new channel, which is almost certainly UHF.

And depending on lots of factors, including antenna direction and getting a relatively recent DTV tuner, your "weak but still watchable" signal might get replaced with a crystal-clear signal. (DTV actually has more problems within 10-20 miles of the transmitter than with distant reception.)

Re:Microsoft Device

[Megane]

If you're having trouble at 20 miles, then your problem is multipath interference. Basically, reflections of the signal off of various objects in an urban area are delayed copies of the original signal. With an analog tuner, this results in ghosting. With a digital tuner, this results in being unable to decode the digital signal. Older ATSC tuners in particular are very bad about rejecting multipath interference.

Rotating your antenna will affect your signal quality. (I have to adjust my roof antenna every two or three months because winds knock it out of position and I lose CBS.) Installing an attenuator in the signal path may result in better reception. The worst thing you can do when you are that close to the transmitter is to use an amplified antenna. The amplifier may distort the signal in a way that reduces the signal quality.

Also, your tuner should have a signal "strength" display. This is usually in fact a signal quality display. Often 75% is the threshold below which there is not enough good data for the error correction to work. If it has an audible signal meter, turn up the TV volume to where you can hear it outside while adjusting the antenna, and set it to the most finicky channel.

It's a simple enough idea

[zappepcs]

and with digital television on the way, much easier to implement without interference. The UHF channels used on your television (most households in the USA have some cable or Satellite feed so don't use broadcast television really) have a small amount of bandwidth between each. If you combined that bandwidth with multiple radio links or some transmission technique, you could use it for WiFi like services locally in the home. The strength of signal could be such that it wouldn't interfere with neighbors reception ( as most aren't using broadcast television anyway) and it gives out more spectrum for home use.

Additionally, there are methods to use a small footprint in the WiFi band to herd the small signals between tv channels. It would look like frequency hopping, require much smaller signal strength, and would cause negligible interference to broadcast television. Simpler still is to allow the user to input the television channels they do watch so that interference is even more remote. If you can steal (locally only) use of channels that are not used at all in the area (how many stations are on channel 63 or 42?), there is literally TONS of bandwidth to use, and all of it at a better frequency range for non-line-of-sight transmissions. That is to say; better signal quality at lower signal strengths.

Re:Already been done?

[qbzzt]

You're talking about teletext. It used extra space in the TV channel for text broadcast. With today's technology, the same bandwidth can be used for decent bandwidth communication instead. The two are not really related except for using the same frequencies.

Re:Google is already Old Media

[Bryansix]

You do know that Google owns You Tube right?

Re:White Noise?

[RenderSeven]

Well, yessss, but guard bands (in lower case) are necessary for TV stations and such not to bleed into each other. That doesnt mean an entirely different modulation scheme wouldnt be able to utilize the bandwidth without interfering with the broadcasts. The newer software radios can operate below the noise threshold, and I can't see how more traditional broadcast methods would be interfered with. Older analog broadcasts are hugely wasteful of the RF spectrum.

Perhaps Google engineers are just smarter than you are :-)

Re:Already been done?

[TheRaven64]

Teletext doesn't use space between channels, it uses space between frames. Analogue TV is a modulated version of the signal that is sent directly into the CRT. For each line, there is a series of peaks and troughs setting the intensity along the scan line[1]. TV resolutions are defined in terms of a number of lines and an aspect ration, rather than a number of columns, for exactly this reason, since signal along a line is analogue (you can squeeze in more, smaller, pixels if you have a good enough signal to noise ratio). At the end of each line, the electron gun is turned off and moved to the start of the next one (you could scan alternate lines right-to-left, but I don't think anyone does. I could be wrong though). At the end of each frame (technically, each field, since TV is interlaced), the gun is turned off again and repositioned pointing at the top-left of the next field.

Each of these repositioning takes time and the signal transmitted in this period is ignored by the TV (since the gun is turned off). Teletext works by encoding digital data in the signal during this period. You can only transmit a small amount of data in this period, but you can do it every frame and it will be buffered inside the receiver.

[1] Colour TV is slightly more complicated.