The leaders of the Software Defined Radio (SDR) Forum, which is working to promote development and field deployment of SDR systems, seemed quite happy when I spoke to several of them when they called during the group's annual technical conference held this week in Scottsdale, Ariz. The Forum reported attendance of about 400, an increase of about 100 over last year's conference held in Orlando. Perhaps a better indicator of the growing interest in SDR was the 40 exhibitors on hand, double last year's turnout.

Even with the up-tick in attendance, SDR Forum leaders seemed happier about finally publishing the request for information (RFI) they have been talking about since August. Issued by the Forum's Public-Safety Special Interest Group, the RFI seeks specific ideas regarding how SDR technology can meet public-safety requirements. "It took a while to dot all the 'Is' and cross all the 'Ts,'" said Fred Frantz, SDR Forum member and director of law-enforcement communications for L3 Communications Government Services.

Among the things the Forum hopes to learn is how to leverage the investment the military has made in its Joint Tactical Radio Systems (JTRS) program, which was created to help the armed forces migrate from their current radio systems to SDR. While many of the military's requirements are shared by public safety, there are many others that are superfluous and would result in form factors and price points that would keep SDR beyond public safety's reach.

"The question is, how can we take what public safety really needs -- and just what it needs -- and roll that technology into something that will fit into the public-safety market," Frantz said.

The Forum also is taking a hard look at the commercial wireless sector, which is taking a much different approach to SDR, Frantz said.

"The commercial side isn't really following the detailed model of the Software Communications Architecture, which requires more hardware, greater computation and greater memory -- all of which drive up costs," Frantz said. The SCA was developed by the U.S. Department of Defense via the JTRS program to ensure that SDRs manufactured by different companies would be able to communicate with each other.

"Public safety is sort of a gray area somewhere between the commercial side and the military side, and would like to leverage that mass market, because they don't have the resources to fund things the way the military does," Frantz added. "So we're looking for the RFI to provide some feedback as to how we can achieve these conflicting goals of high capability and low cost."

John Powell, Forum member and senior consulting engineer to the U.S. Department of Justice and U.S. Department of Homeland Security, said the Forum is eager to see whether manufacturers such as Motorola and Ericsson will be willing to share waveforms that include significant intellectual property rights (IPR). "Company A can't build a product that will be interoperable in today's environment unless it can support Company B's proprietary waveform," Powell said. "[But] other than P25, there are no trunking protocols out there that are open today. They all have significant IPR."

Powell added that he doesn't believe any of the companies that own the most popular public-safety waveforms are going to give up, "in the name of promoting public safety and interoperability," those for which they own IPR. "Cross licensing is probably where we're going to end up," he said.

Another area of interest concerns standards. While the military has largely defined standards within the devices, public safety thus far has chosen to define standards "either between systems or between devices within a system," Frantz said, adding that he hopes that JTRS program participants and public safety comment on the advantages and disadvantages of their respective approaches.

The deadline for comments is Dec. 15. The RFI can be found by