Google Granted Patent Can Filter Distortion in Unused TV White Spaces
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’s “White Space” FCC Proposal Heralds New Day for Telecom and Broadcasting
- Google Submits ‘Foolproof’ Wireless Broadband Plan
- Google and the White Spaces
- Google’s Wi-Fi Dreams: Tech giants and broadcasters tussle over vacant TV channels
Google has a few other granted patents involving communications networks: