An Interview with Eric Blossom

by Don Marti

Eric Blossom's ambitious goal for the GNU Radio project is to "get the software as close to the antenna as is feasible" and turn radio hardware problems into software problems. Check out Eric's article, "GNU Radio: Tools for Exploring the Radio Frequency Spectrum", in the current issue of Linux Journal. In this interview, we catch up with the latest developments for GNU Radio.

Linux Journal: Does the FCC's new Broadcast Flag regulation shut down GNU Radio? Or does a person with the skills to configure and use GNU Radio not count as an "ordinary user"?

Eric Blossom: So far, we think we're okay. The EFF has requested a clarification on our behalf. The crucial word in the rule is "component", and it's not defined. If it means hardware component, then we narrowly are exempt from the requirements. If it means software component, then we've got a problem, and we'll put the lawyers in action.

LJ: Your Web site has a great page about the Universal Software Radio Peripheral (USRP), an experimenter's board that connects to your computer via USB. Will the USRP be able to receive all the modes you cover, including HDTV?

EB: We think we can cover a lot of interesting things, including HDTV. The limitation with the USB approach is the bandwidth we can sustain across the USB. We can sustain 32MB/sec, which should be enough to get the raw or slightly processed HDTV signal across. We expect to be able to access about a 6MHz chuck of the RF spectrum, so a TV channel just fits.

LJ: Are you planning to use GNU Radio as the basis for a wireless mesh network?

EB: There's a lot of interest in that area. In fact, the National Science Foundation has an initiative underway on Programmable Wireless Networking. We've been in communication with a bunch of people in the academic community. A lot of them are enthusiastic about using GNU Radio as the framework for their experimentation. To avoid a duplication of effort, our basic plan is to ensure they [have] whatever infrastructure they need and then to coordinate on the implementation of the various waveforms that would be required for wireless networking.

There are all kinds of interesting problems that need attention, and we think that GNU Radio will serve nicely as a free software platform for research. Folks are looking at wireless networking from all angles and layers: collision free media access layers, dynamic routing of moving nodes, appropriate transport protocols, etc. It turns out that TCP isn't a good transport for wireless. It will run over wireless, but it doesn't work all that well. The characteristics of the medium keep varying in ways that TCP doesn't handle well.

LJ: Do you have a business around GNU Radio as a consultant or hardware supplier?

EB:I've got a business that's primary charter is the support and management of the GNU Radio project. The bulk of my work on GNU Radio is supported by individual and corporate donations made through the Public Software Fund, Inc.

We kind of backed into the hardware project, because nobody else was building what we wanted. At first we looked for existing board manufacturers who would build what we wanted. We found a company and got the initial prototypes built, but then that company was acquired. The new parent didn't think the USRP fit their product line. So at this point, we are considering a variety of options. Putting together a company to build and sell them is one thing we're looking at. Even though the USRP is a free hardware design, unlike free software, somebody's got to take on getting the hardware designed, built, marketed, sold and delivered. It's a bigger problem then releasing tarballs.

Don Marti is Editor in Chief of Linux Journal.

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