Data rate: Assuming one white-spaces Internet tower for every 2,000 people, with each person transferring data 24 hours a day, long-range wireless data speeds will vary considerably. Blue shows the lowest speeds; red the highest.
Mubaraq Mishra/Berkeley/IEEE
People in rural areas may gain more wireless airspace from the shutdown of analog television.
A person living in upstate Michigan may gain significantly more from the death of analog television than someone living in New York City--at least, as far as long-range wireless Internet is concerned, a study suggests. On November 4, 2008, the Federal Communications Commission voted to allow the "white spaces" in the radio spectrum that were freed up by the analog television switch-off to be used for long-distance wireless Internet connectivity. This spectrum will be unlicensed, meaning any standards-compliant device can use it.
The most detailed analysis yet of the potential of these white spaces for long-distance wireless Internet has now been published by researchers at the University of California, Berkeley. Their models illustrate how the interaction of population density, television stations, and economics will determine what consumers ultimately get.
The decision to free up white spaces was warmly welcomed by companies including Google, Microsoft, and Intel because the lower-frequency signals in the newly released spectrum travel further and penetrate buildings more effectively than existing wireless data connections like Wi-Fi, Bluetooth, or cell-phone links. (Google cofounder Larry Page has dubbed this kind of wireless connectivity "Wi-Fi on steroids.") But unlike other commercial spectrum, the frequencies available to devices will not be the same in every location. Devices will instead have to use whatever spectrum is unclaimed by the digital television stations in their area. Although this is intended to make more efficient use of available spectrum, it makes the actual deployment of these white-spaces devices more complex, because they will need to avoid treading on the radio-frequency toes of local television broadcasts.
The FCC has drafted rules on the requirements for how devices might do that, with the final version expected late this year, and various electronics companies are already working on white-spaces devices. But the exact scale of the opportunity is still unclear, says Mubaraq Mishra, who conducted the new study with Berkeley colleagues Anant Sahai and Kate Harrison.
To get at what may be on offer to people who want to use white-spaces Internet, their model uses the FCC's database of active television stations to calculate the usable white space available in each area. It also draws on census figures for the number of people living in each U.S. zip code. Including population data at the zip-code level makes their assessments unique, says Mishra, and more powerful. "White spaces are ultimately for people, not random locations, so we think it's important to also incorporate that," he says. "We wanted to know how many channels or how much bandwidth does a random person in the U.S. get."
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The results of the work-in-progress analysis are interesting, and personally relevant because I reside in a metropolitan fringe area where broadband availability has been quite limited until recently. A link to some enlarged version of the map would be very nice, even if it's a low-resolution graphic in order to preserve the proprietary value of the original for the authors.
Hi,
I am the Berkeley faculty member whose study is being discussed. My student Mubaraq (now graduated with his PhD) is the one who initiated this line of research, but proper credit for the figure shown here belongs equally to my first-year graduate student Kate who is continuing this line of investigation for her MS thesis. I hope that the TR will update the caption accordingly.
The per-person long-term average data-rates depicted in the map represent the work in our 2010 DySpAN paper (linked to on my homepage). These take a little more conservative perspective regarding frequency reuse. (read the paper for the exact assumptions made) Kate has recently obtained results from a more cellular-like model (that takes into account that some users in a cell are closer while others are at the edge) that I previewed at the Wireless Innovation Forum's event in Washington this past Tuesday. The average per-person data rates come out higher in that case.
We are in the process of writing the updated results up (it is also Summer, so keep that in mind!) so those interested can see my website where I will post the preprint when it is done. In addition, all the downloadable code/data required for people to replicate the results will also be linked to in the paper, so others can build on our work -- or find bugs for that matter.
This is a matter of public interest, and we at Berkeley tend to believe strongly that such discussions should not be proprietary.
It is good to see people are analyzing data points for white spaces, but this is just one use case, 2000 people to 1 tower. And while that’s an interesting data point, what would happen to the map in a scenario with 1000 or 500 users per tower? More data points are needed. In addition, other use cases need to be evaluated, for example, a use case on personal portable devices or using white spaces as an enhancement to WiFi in the home.
The point of opening the white space spectrum is rural broadband. While the bias of the article is that the benefits of white space access is disproportionately to rural users, this is by policy design. Rural users do not have 3G. Rural users do not have fibre connections. Many rural users do not have broadband cable. If anything, perhaps the title of the article should be, "Urban users get unexpected benefit from white-space usage".
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39 Comments
Cell phone like protocol?
The new "white space" wireless technology will be a boon to people in rural areas where there are no good alternatives for Internet access. I hope the FCC preserves the valuable bandwidth by requiring protocols like cell phones have, reducing power to the minimum needed so as to avoid interference. That way more white space stations operating at lower power can be constructed at a later date, if traffic increases.
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