The term cognitive radio, coined by Dr. Joseph Mitola, refers to "a radio frequency transmitter/receiver that is designed to intelligently detect whether a particular segment of the radio spectrum is currently in use, and to jump into (and out of, if necessary) the temporarily-unused spectrum very rapidly, without interfering with the transmission of other authorized users."
Cognitive radio (CR) is the next step in the evolution of software-defined radio (SDR). It takes SDR's ability to adapt to changing communications protocols and frequency bands and adds a new dimension: the ability to perceive the world around it and learn from experience.
FCC Commissioner Jonathan Adelstein says, "Cognitive radio technologies offer the potential for even more innovation that can spur our nation's productivity and our citizens' safety."
To the military this means radios that can adapt to the needs of any branch of the service, in any country, across time To emergency and public-service providers this means spectrum sharing, while maintaining their priority. For the consumer it means a cell phone that can "tell" them, in real time, what the traffic conditions are ahead, where the nearest gas station is, and even how the surrounding terrain was formed.
It is a powerful vision of the future, which brings with it attendant challenges. The advent of CR engenders a quantum leap for policy makers and users alike. The concept of radio that can "learn" is a fundamental change in the perception of radio and the rules that govern it. In addition, the technology to create this new usage means a substantial overhaul of the way we do telephony today.
To realize the full potential of cognitive radio, there are hurdles to overcome. These include: the FCC development of policies that address and enforce the process and rules governing how frequencies and waveforms are selected and approved for use by cognitive equipment; software flexibility that can interface with policy updates; and functional interaction in the real world.
Development of policies
The first actionable challenge to development of CR lies with the Federal Communications Commission and related international governing bodies in developing policies governing cognitive radio. The two primary considerations are the language and protocols for initial interfacing with software and compliance/validation for existing instruments as policies change across time.
May 2003, marked the FCC's first public recognition of CR as a way to dramatically improve the efficiency of spectrum use. One of its first steps was a notice of proposed rule making and request for comment on "how rules and enforcement policies should address possible regulatory concerns posed by authorizing spectrum access based on a radio frequency (RF) device's ability to reliably gather and process real-time information about its environment or on the ability of device and/or users to cooperatively negotiate for spectrum access."
In response, a number of groups formed to provide feedback to the FCC. The National Science Foundation is studying and holding a number of interactive meetings with interested participants.
The newly formed Software Defined Radio Forum (SDRF) is taking a leadership role in exploring the questions that will help the FCC define policy. The SDRF is actively organizing people to begin to ask the right questions, defining interfaces and holding technical conferences.
Legacy spectrum holders are weighing in with their concerns about losing their spectrum. Internationally, the European and Asian communities are moving forward to develop their own policies, hoping there will be efforts to harmonize these policies among Europe, Asia and the Americas.
This need for national and international standards and policies is not theoretical, but urgently practical. Without it there can be no software development, and software is the very heart of CR.
Fundamentally, CR will have computational models of itself, its user, the uses it is put to, the networks available and its environment. Formulating standards in which waveform software has well-defined interfaces will not only make it feasible, but will in fact spur cooperation among developers of software.
As development moves forward, the greatest difficulty will be creating for an unknown future. As cognitive radios are placed in service, they will comply with prevailing operating rules of engagement. But on both the national and international fronts, policy will necessarily be fluid, adapting to changing needs, users, borders and technological advancements and challenges. It will be no small task to develop software agile enough to anticipate, accommodate and adapt to these unknown changes.
Current software development includes cellular waveform software, specifying what kind of waveform is needed to communicate in a particular application. But it must now expand into the kind of software that multimode radios can use to implement more than one waveform type. In addition, networking software needs to be developed that allows CR to participate in more than one network.
Other software development in the United States, principally through the Department of Defense and in academia, is in the early experimental stages.
Meanwhile, in Europe the E2R research program took a brisk approach and is studying end-to-end reconfigurability. This could effectively position them to control the intellectual property of CR. If the United States wants leadership in software development it may be necessary to set a more aggressive pace in software development.
The third and final hurdle for cognitive radio is real-life functionality. Cognitive radio will be required to interface with ever-expanding networks.
When the dream of cognitive radio melds into our highly mobile lives, it will be necessary to exhibit maximum flexibility and cognition to access shared spectrum on an opportunistic basis. For example, a construction foreman who stops at Starbucks on his way to the job site will need to see the color of the roofing that is being delivered to the site, then find real-time alternatives to freeway congestion. When he gets to the site he'll need to e-mail the latest blueprint revisions to his home office, through the least expensive network. If he accidentally loses his phone, he needs it to call him and tell him where he lost it. And do this while sending and receiving phone calls and e-mails.
Currently there are few, if any, standardized protocols that lay the groundwork for this functionality.
As the appetite and need for services grows, networks are proliferating. In the defense community alone there are perhaps hundreds of different waveforms and networks made of those waveforms. Government networks are growing, including metro-area networks. In the commercial community there are Wi-Fi, WiMax, and Bluetooth networks. Add to these satellite networks based on Iridium that are capable of voice and data transmission.
The question now becomes: with so many points of entry and networks, each with their own services, how will CR be able to interface with the proliferation? The challenge then is to write software that is smart enough to choose the optimal network that fits the radio operator's requirements today and tomorrow.
Additionally, networks must be able to announce their availability. This network intelligence and access is integral to the CR's cognitive power.
We have difficult and complex questions facing us in the next decade. In addition to the pressing need to develop standards and policies, we face the daunting challenge of developing software that can imbue CR with the ability to reason, establish situational awareness and adapt to changing conditions in both policies and functionality.
By focusing time, energy and resources into both policies and software, we can realize the full potential of cognitive radio and its ability to maximize use of the spectrum while delivering ever-expanding services both here and around the world.
Bruce Fette (Bruce.Fette@gdds.com) is senior scientist at General Dynamics C4 Systems (Scottsdale, Ariz.).