06-12-04

One Box Fits All Software Radios

Researchers at Virginia Tech's Mobile and Portable Radio Research Group have written open-source radio software that may lead to creation of a single device that can receive and decode everything from emergency services radio signals to television -- and act as a garage-door opener. 
 
 When people think of a radio, they usually think of a small box that uses an antenna to pick up and play AM talk or FM music.

But a radio is any device that transmits or receives signals in the radio frequency (RF) part of the electromagnetic spectrum.

By that broad definition, radios include televisions, cell and cordless telephones, pagers, and even garage door openers.

So why don't we think of these everyday electronic gadgets as the radios they are?

Because they all have different hardware, or more simply, they all come in a different box.


Too Many Boxes

A combination TV/AM-FM device operates with two separate radios -- one to receive television broadcasts and the other to receive radio broadcasts.

Two distinct transmitters would also have to operate a combo garage and car door opener. A fire chief using a walkie-talkie could only contact a police officer if the two radios had the same type of hardware.

Clearly, dedicated hardware limits the function of a radio.

If one box, however, fit all, radios would become more like computers, whose function fluctuates with whatever software is running at the time.


That's the idea behind the so-called "software radio."

FM/AM with a Higher IQ

If you took an IQ test with this analogy: word processor is to spreadsheet as FM radio is to garage door opener, you might think the examiner was crazy.

Unless, of course, you knew about so-called "software radio."

Using a software radio, that flummoxed fire chief can simply load software designed to communicate with the police officer's radio -- a transition made possible because software rather than hardware defines the radio's signal processing capability.



 

Software radios use software to modulate and demodulate radio signals.

Modulating a radio signal is a way to encode sounds on radio waves. Modulating the wave in an AM, or "amplitude modulation," radio adjusts the amplitude of an electrical wave that a receiver then filters and amplifies, producing an audible sound.

Adjusting the frequency rather than amplitude of a radio wave to encode audible information is known as "frequency modulation," or FM.

Radios can use dozens of modulation techniques, however, including phase modulation (PM); pulse modulation; sideband modulation; and several others.

But until software radio, the idea of using one radio with all these modulation techniques was far-fetched at best.

Of course, with computer software, no one questions the idea of using one box to do multiple tasks -- Web surfing, word processing, database  building, and e-mailing, for instance.

Radio Wave of the Future

Software radio has been the purview of the entrepreneurial open-source community.

A recent addition to free open-source radio software available around the Web comes from Virginia Tech's Mobile and Portable Radio Research Group (MPRG).

"The tool available on the Virginia Tech Web site already has been downloaded by numerous companies and universities from around the world," said Jeffrey Reed, professor of electrical and computer engineering and deputy director of the MPRG.

Written in C++, OSSIE (Open-Source Software Communication Architecture Implementation: Embedded) is an operating environment, or software framework, that supports programming and operation of software radios.

MPRG's Robert and a team of graduate students first developed OSSIE as a tool for a software radio research project sponsored by the Office of the Director of the Central Intelligence Agency.

"Robert and Reed soon realized that other researchers could use OSSIE in their development of software radios," explained Virginia Tech spokesperson Liz Crumbley. "They also realized that pooling software with other researchers would add to a collective knowledge base for the creation of a variety of working software radios."

Open Source

Researchers can download OSSIE free, but "are responsible for sharing their findings for free with other researchers," Crumbley said.

"Offering OSSIE as an open-source tool over the Internet will speed up growth of the technology and make faster innovations possible," Robert said. "This will benefit all wireless  researchers who are working to develop software radios."

If the evolution of the PC  is any indication, software radio may be the radio wave of the future.

"Software radio technology is today where personal computer technology was in the 1970s," said Max Robert, the MPRG post-doctoral Fellow who led development of OSSIE.

 

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At last a revolution in the Wireless Software Radio technology!

 


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