DSCN1072.jpgWhen the 9/11 Commission released its final report in August 2004, one of the failures it cited was the inability of first responders to communicate across agencies. Police were on one system, firefighters on another, and firefighters inside the World Trade Center never got the message that the buildings were about to collapse.

If a cutting-edge technology called software-defined radio (SDR) had been available then, those problems could have quickly and easily been circumvented. SDR uses a computer and interface to digitize radio signals, with any updating or reconfiguring carried out via software. In addition to the obvious economic advantages, the technology provides unsurpassed flexibility to respond to changing needs and conditions, whether that means shifting frequencies to prevent enemies from listening in on military communications, identifying unused portions of the radio spectrum to avoid interference, or allowing public safety personnel from multiple agencies to communicate directly during an emergency.

Most research in the field is currently being done at the graduate level, but thanks to support from Edwards Air Force Base, CSUN is one of very few institutions involving undergraduates. Since January 2009, under the mentorship of professors Sharlene Katz, James Flynn and David Schwartz, several teams of Electrical and Computer Engineering students have completed senior projects in SDR, carrying out proofs of concept with broad implications.

One group, for example, established a telemetry link to transmit images and data, such as battery status, speed, altitude, temperature, position, etc., from an unpiloted air vehicle (UAV) to a ground station. The project not only educated students about the basic problem of sending telemetry down from an aircraft using only an onboard robot, but also addressed the issue of finding sufficient spectrum for the data transmission.

_DSC7402.jpg“We only have so much spectrum, and we’re using a lot of it—we have cell phones, Blackberries, garage door openers, etc., and we’re running out,” Katz explains. “We can’t make more spectrum, but software-defined radio allows you to design radios that can find unused chunks of spectrum and move around to access it.”

“There’s a rule in communications that the more information you need to send, the more spectrum you have to occupy,” Flynn adds. “Modern aircraft testing requires enormous amounts of information to be sent down in real time, but Edwards is constrained in what spectrum it can use—they don’t have an infinite amount of it. We had to educate the students about that.”

The students designed the SDR system so the mode and frequency could be changed on the fly. In place of the old cumbersome and time-consuming process—landing the aircraft to switch out equipment, which can take days or even weeks—operators using the prototype SDR system were able to make the necessary changes with the press of a button. Subsequent student teams have worked on enhancements to the system, including one that has made the search for available spectrum automatic.

Another project, which used the same hardware as the UAV project, replicated the performance of a high-end commercially available ham radio transceiver. With inexpensive hardware and software, the CSUN team was able to replicate and in some cases surpass the capabilities of the high-end hardware, which can cost as much as $2,000 to $3,000.

sdrgroupa.jpg“The students had to learn about modes of communication and implement them in software, as well as make a human interface that would allow someone with limited technical skills to get on the air,” Katz says.

They were so successful that a group of students in San Francisco found the CSUN team’s Web site, downloaded the software and got it working, all without ever talking to team members.

Katz, Flynn and Schwartz are eager to keep building on these successes. Current teams, for example, are working on miniaturizing the telemetry system using programmable integrated circuits and incorporating a camera that adds target recognition capabilities.

“SDR will be the technology of the future as far as radio is concerned,” Katz says. “It’s going to be very important.”