An advanced radio technology that will help public safety agencies manage spectrum more efficiently is making its way out of the laboratory and into the hands of first responders. The multiband cognitive radio system, being developed by Shared Spectrum Company (SSC), hinges on a spectrum management subsystem for radio networks that controls how individual devices access spectrum through “policies” that allow better use of available frequencies.

The cognitive radio access and management (CRAM) subsystem, funded by the National Institute of Justice (NIJ), will permit the creation and dissemination of a range of spectrum access and priority rules. These tenets include trusted security measures to prevent unauthorized access and operation. CRAM also will feature the capability to log transmissions for monitoring usage and to correct interference rapidly.

The program’s first phase will determine the characteristics of the spectrum gaps that public safety cognitive radios can exploit. SSC will conduct laboratory and field demonstrations using prototype cognitive radios. This will highlight the prototype cognitive radios’ ability to exploit spectrum gaps across multiple bands automatically without causing interference in legacy radios.

The CRAM subsystem and the company’s prototype radio are modeled on a policy-based cognitive radio system the firm developed for the Defense Advanced Research Projects Agency’s (DARPA’s) Next Generation (XG) radio program. According to Preston Marshall, DARPA’s XG program manager, the key aspect of cognitive radio technology is the device’s awareness of its environment, including local spectrum and other users in the spectrum as well as the radio’s internal environment—what the device’s user and network are trying to accomplish. He notes that XG technology is centered mostly on the radio as a participant in the environment.

DARPA researchers believe that moving from fixed spectrum assignments to dynamic spectrum assignments yields 10 times more user access in the same amount of spectrum. The agency has installed its XG-based SSC technology into push-to-talk military radios from Harris Corporation and Thales that are similar to those used by first responders.
Marshall explains that XG’s core principle is “Do no harm.” Introducing XG radios into the spectrum will not affect the ability of other military or civilian users to access the spectrum. He admits that XG systems require more resources than conventional radios, but adds that they also provide users with more capability. “Typically the XG implementations that we are looking at spend less than 5 percent of their time doing dynamic spectrum. But for a 5-percent overhead, maybe you can get 10 times more devices in the spectrum. That’s a really good return,” Marshall emphasizes.

The technology also reduces the manual footprint, so users can operate the devices without preplanning their spectrum allocations. “By taking people out of the chain, we can make the system much more responsive. Managing our wireless networks today is a very touch-labor-intensive business. A lot of man-hours go into setting up and managing these networks. If we’re really going to push wireless to the edge, we’ve got to reduce the manpower footprint as well as everything else,” he says.

Marshall notes that the military and first-responder communities have many similar communications needs. Both groups operate in high-surge scenarios, and both may have to operate without depending on infrastructure in an unpredictable environment.

Dynamic spectrum allocation is the first entry-level technology into cognitive radio. Marshall explains that dynamic spectrum provides radios with many advantages. He notes that the radio spectrum is very crowded, and it is very difficult for managers to build spectrum plans in advance that are responsive to user needs. Installing the technology into a radio—and allowing it to use those free parts of the spectrum that it senses—provides a clear operational advantage, he maintains. “We really see dynamic spectrum as opening up an opportunity to deploy the first generation of cognitive radios that use existing equipment and to set the stage for the next generation where we start to build around it.”

A variety of future technologies will follow this second generation, such as handsets that index all of the content they transmit so users will not have to access the communications infrastructure to locate information. These devices also would learn what users around them were interested in and manage this content.

Marshall notes that the U.S. military is very interested in the technology, but he cautions that regulatory organizations need to develop methods to manage and regulate cognitive radio. DARPA is working with the U.S. Army’s spectrum office to develop operational procedures for cognitive radio systems.