Google Granted Patent Can Filter Distortion in Unused TV White Spaces

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Google is aiming at providing wireless internet access in unused television channels in the white space between channels 2 and 51 on TV sets that aren’t hooked up to satellite or cable services.

While many stations broadcast between these ranges in the US, most areas have gaps where there aren’t broadcasts carried on those channels.

Google filed a letter with the Federal Communications Commission on March 21 – Authorized Ex Parte Contact – Unlicensed Operation in the TV Broadcast Bands (pdf) – presenting plans to use those gaps for wireless broadcasts in those TV bands to unlicensed personal and portable devices.

The access could be used for mobile devices, such as those that could be built to use Google’s open source Android platform.

The letter provides some details on the type of measures and technology that might be needed to enable the use of these unused airwaves.

One technology that isn’t detailed, but could possibly be used is described in a patent granted to Google this week. It provides details about a filtering system that would work with a receiver in this spectrum to reduce distortion in the signal and increase the transmission range in those signals.

Method and system for temporal autocorrelation filtering
Invented by Carroll Philip Gossett and Michial Allen Gunter
Assigned to Google
US Patent 7,352,833
Granted April 1, 2008
Filed November 18, 2002


An autocorrelation filter for use with a spread spectrum receiver. The autocorrelation filter can be used as a prefilter stage to reduce phase distortion present in a spread spectrum signal. The autocorrelation filter can be used to process the output from a lattice filter. The lattice filter is configured to remove magnitude distortion from the spread spectrum signal.

The autocorrelation filter performs a series of correlations on the output of the lattice filter. The results of these correlations are integrated over a period of time to generate a running impulse response for characterizing and removing the phase distortion in the spread spectrum signal.

More details on Google’s plans to use this space can be found at:

Google has a few other granted patents involving communications networks:

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4 thoughts on “Google Granted Patent Can Filter Distortion in Unused TV White Spaces”

  1. Google is not wasting any time in identifying future possibilities. Utilising this unused broadcast frequency range to provide free wireless, that will tie in exclusively with their mobile application makes good sense.

    The future lies in mobile, and by going this route they sure are stealing a march on the competition! Look forward to see where this is heading.

  2. I think that Google’s been considering the possibility for a few years, which is pretty wise.

    Mobile use of the wireless web will be huge, but I’m not sure how much of a lead they might have on their competition. Microsoft seems to be paying pretty close attention to the space, too. And Yahoo has a number of interesting mobile applications already out in the world.

  3. This can be trouble for people that use amps on tv antennas.
    Being close to transmitters may swamp the amps and with the switch to digital tv it could cause tptal loss for the tv’s close to the transmitters.

  4. Hi John,

    Yes, one of the issues that surrounds using this white space is the possible impact upon others. Hopefully technology can be developed to overcome problems like that.

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