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Cognitive radio seems the stuff of science fiction—a radio that will ‘know’ where ‘home’ is and manage the transceiving functions based on what the user wants the radio to do. But it may not be that much fiction or even that far from reality. Cognitive radio has the potential to enable a variety of communication functions. The concept of the ‘cognitive’ radio was originated by Defense Advance Research Products Agency (DARPA) scientist, Dr. Joseph Mitola, and is the ‘next step up’ for software defined radios that are emerging today, primarily in military applications.
Most commercial radios and many two-way communication devices are hardware-based with predetermined, analog operating parameters. Although device functionality is expanding, if you really want something significantly different, you pitch out the original and replace it with new hardware. Software defined radios (SDRs) change all that by relying on embedded software for their functionality and configuration.
Cognitive Radio Has SDR at its Root
Driving the development of SDR technology is the Software Defined Radio Forum (SDR Forum). It’s an independent technical council comprising industry scientists, engineers and regulators who are working on the regulatory, technical and operational aspects of software defined radios. Through the Forum’s work and with industry development, software defined radios are making it possible to change waveform properties and applications while operating in the field via the addition or upgrade of software. For SDRs, reprogramming or upgrading a single radio or a radio network takes about as much effort as upgrading a computer’s operating system or program options.
The SDR Forum continues to develop and refine the standards by which upgrades and modifications can be performed so that evolutionary technology can be harmoniously integrated into the radio once it has been sold and installed. The inherent flexibility of software defined radios allows equipment developers, and eventually users, to enhance the operating capabilities of their equipment. As an additional benefit, because software defined radios can allow upgrading, bug fixing and the delivery of additional functionality, the customer receives incremental value on the radio, considerably improving cost-effectiveness.
For its part, the U.S. Navy is likely to be the largest consumer of software defined radios with the military’s Joint Tactical Radio System Initiative (JTRS) radios following closely behind. For the Navy, the software-based Digital Modular Radio (DMR) is replacing a roomful of radios with a single rack of DMRs. The DMR (Figure 1) is a four-channel, full-duplex system that is essentially four radios in one. Currently operating on submarines and surface ships around the world, the DMR (AN/USC-61) is successfully demonstrating the viability of software defined radios on active duty.
The JTRS radios are software defined radios in various stages of development. In a number of demonstrations to the military, the small ‘form-fit-factor’ of the JTRS SDR displayed the ability to fulfill military communications functions and were small enough to integrate into miniature robotic devices or body electronics worn by soldiers. The demonstration emphasized that SDR technology improves interoperability among military services, coalition partners and public safety officers, resolving bandwidth problems and reducing the number of radios required to accomplish specified objectives. Once the JTRS radios are fielded, the military expects to have total communications interoperability between all armed services and across all operating platforms, an advantage they currently don’t have.
Technology transfer from the government/military use to the consumer marketplace is a popular development path for new consumer goods, particularly electronics. And, since software defined radios already use a significant COTS population in the electronic components, it’s not a huge leap to move from the military/government application to a shelf at the local consumer electronics store.
The Case for Cognitive Radio
The explosive growth in wireless services over the past several years illustrates the huge and growing demand of the American business community, consumers and the government for spectrum-based communications. Continuing advancements in technology, products and services are tasking the finite resources of the available spectrum and public policy is forced to address dramatic changes, as it must adapt to accommodate the exponential demand on spectrum access, efficiency and reliability. Increased demand versus finite resources—it’s an age-old predicament that is usually remedied by either technological break-through or very expensive, limited and exclusive access to the resources at stake.
It appears that the concept of cognitive radio has the inside track for resolving the technical side of the issue; however, regulatory considerations at the level of the Federal Communications Commission (FCC) are also an important component for a functional solution. In response, the FCC has convened a number of Cognitive Radio Workshops, an inter-industry and inter-regulatory task force responsible for gathering, analyzing and reviewing spectrum allocation (Figure 2), use and licensing issues for the future.
Where the Technology is Today
The cognitive radio, as its name implies, carries a level of cognition or intelligence that permits decision-making and learned patterns of behavior. According to Institute of Electrical and Electronic Engineers (IEEE), the cognitive radio is a radio transmitter/receiver that is designed to intelligently detect whether a particular segment of the radio spectrum is currently in use and to jump into (or out of) the temporarily-unused spectrum very rapidly without interfering with the transmissions of other users.
As explained earlier, the cognitive radio, according to Dr. Mitola, will ‘know’ where ‘home’ is and manage the transceiving functions based on what the user wants the radio to do. It will have the flexibility to operate in the 800 to 900 MHz band, be able to adapt to the 300 to 1000MHz ISM band, to the IEEE band or 5GHz. Based on experience, the radio would know what to do, where to go and how to make the operating changes without the user’s awareness and without interfering with other communication equipment.
Some of the radio’s other cognitive abilities include determining its location, sensing spectrum use by neighboring devices, changing frequency, adjusting output power or even altering transmission parameters and characteristics (Figure 3). All of these capabilities, and others yet to be realized, will provide wireless spectrum users with the ability to adapt to real-time spectrum conditions, offering regulators, licensees and the general public flexible, efficient and comprehensive use of the spectrum.
Putting cognitive radio in context, imagine this scenario: A cognitive radio is aware of a Bluetooth network and what is available of interest to its user within the Bluetooth service zone. It could also be aware of what is available in the wireless LAN range, cell phone range and so forth. This would be as though the cognitive radio notified its user that a bookstore down the street had a rare book the user wants and tells the user how to find the store.
With the help of the SDR Forum, the FCC and industry partners such as General Dynamics, Vanu, Rockwell Collins and others, standardization is expected to become formalized by 2009. With software defined radio products a reality today, SDRs with cognitive capabilities are the next logical step and it is just a step—no longer a leap—to the next best communications technology.
General Dynamics C4 Systems