Frequency-Hopping Radio Wastes Less Spectrum
With a rising tide of smart-phone data threatening to drown the airwaves, a White House advisory panel is poised to suggest that wireless carriers and research labs ramp up efforts to use computing to far more efficiently tap spectrum.
This will require, among other things, so-called “cognitive” radios, which sense unused radio bands and can intelligently switch heavy data loads between different frequencies without any interruption.
A New Jersey startup has come out with the fastest cognitive radio yet. It works on the widest possible range of spectrum, and is part of a crop of improved technologies that are crucial to bringing the technology to market and avert network overload.
The gadget in question, called CogRadio, and made by Radio Technology Systems of Ocean Grove, New Jersey, can switch at fast-enough rates to be imperceptible for, say, a video viewer; as well as in sufficient quantities that any research done on it, or software written for it, will be applicable in future real-world commercial devices.
“It’s the most usable and versatile wideband radio the research community has ever had access to,” says Dipankar Raychaudhuri, director of the Winlab, the wireless research lab at Rutgers University, where the technology was codeveloped. Existing models, he says, can’t switch fast enough, and have limited spectrum range and data-carrying capacity. “Today, it is the best available experimental cognitive radio, and this is crucial because the whole community is gearing up” to test and deploy such technology.
The device is the first that can operate from 100 megahertz to 7.5 gigahertz, meaning all the way from AM and FM bands though television and Wi-Fi and cellular frequencies. It can also sense available spectrum and switch between frequencies within at 50 microseconds, and in some cases as little as one microsecond. This is a record speed, according to Peter Woliansky, a Bell Labs alumnus who made the gadget and founded the startup behind it.
Finally, it can handle 400 megabits per second of data—about eight times what a typical home Wi-Fi system can do. With this kind of rate—and since it can send on multiple frequencies at once—it could conceivably dispatch 20 HD movies at the same time.
Ultimately, intelligent commercial wireless technologies using such features could allow for more services. And as new and disruptive wireless technologies enter a field now dominated by a few major carriers, it could create competition that lowers costs for average consumers.
The gadget costs close to $6,000, but that’s cheaper than existing models. As prices keep coming down, such gadgets become available to wider swaths of code writers, not just well-heeled labs. “For people studying wireless technology, building the radio and getting it to work is ridiculously hard,” says Woliansky.
One of CogRadio’s jobs will be to serve as the test bed for the National Science Foundation’s research efforts to build a mobile-centric Internet, in which radio communications and smart phones are seen as the major delivery vehicle for Internet access, a project headquartered at Raychaudhuri’s lab.
CogRadio will also be used in one of the first outdoor tests of cognitive radios, underway at the University of Colorado, Boulder, where its software was developed. (Cognitive radio research has mainly been conducted in shielded labs because of the potential for dangerous interference, but the U.S. Federal Communications Commission has started granting outdoor permits to promote research.)
And researchers at Virginia Tech will use the gadgets to develop next-gen high-speed broadband police and fire and other emergency radios that include video and Internet access.
Cognitive radio technology could enable a range of new services. For example, it could route cellular calls to Wi-Fi signals—something that is done today in small wireless base stations called micro cells—but also avoid having to use fiber to send the signal out over the Internet, and instead use available television spectrum in the 400 megahertz range.
With all such projects, the big challenge is rapid switching speed and high bandwidth—all things that pound on radio hardware. “You want to jump around in radio spectrum as fast as possible and as far as possible, and when you land somewhere, you want to grab as much spectrum as you can, and pump it in and out of the radio, and these are actually very challenging to do,” says Chip Elliot, project director for the NSF’s cognitive radio project at BBN in Cambridge, Massachusetts. “This radio is perfect for things like that.”
Someday, future smart phones and other gadgets will incorporate portions of such technologies. “While this is an important milestone for realizing high-performance and usable cognitive radios, much more work needs to be done by industry on chip design, interfaces, and much else,” Raychaudhuri says. Other companies and research groups are working on developing better and cheaper cognitive radios.
The field is heating up as demands on mobile networks rise. Bell Labs estimates that mobile data traffic will grow by a factor of 25 by 2016, and Cisco says it will grow 18-fold by that year. With the FCC making clear that existing spectrum will run out by next year, new technologies will be needed.
The forthcoming White House report is being co-authored by Google chairman Eric Schmidt and others, including Craig Mundie, the chief research and strategy officer at Microsoft. FCC chairman Julius Genachowski has also been pushing industry to develop intelligent spectrum-sharing technologies.
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