Last December, the FCC opened wide what many believe will be the next frontier in wireless communications. In a notice of proposed rule making (NPRM), it asked how cognitive radio could best be implemented. That action brought to the fore founding research by Joseph Mitola, who coined the term cognitive radio (CR), and sparked a flurry of activity among industry and academic wireless systems designers and researchers.
Derived from a need for more-efficient spectrum use, a CR fundamentally senses whether a band is being used and jumps in when the band is unoccupied. It jumps to another band when the primary user recommences transmissions. Or, the radio can stay in the band and alter its power frequency and modulation to avoid being an interferer.
Immediately, this raised the possibility that licensed TV bands, desirable for their long-range propagation characteristics and low components costs, could be used for broadband wireless transmissions, particularly in rural areas. But, as Bruce Fette of General Dynamics Decision Systems explains, CR can go beyond simply making better use of spectrum by imbuing portable devices with unprecedented levels of real-time intelligence.
But with promise come problems. As John Notor from Cadence points out, the FCC may have let the ball slip on CR with respect to TV spectrum. And Bill Krenik of Texas Instruments examines the basic issue with CR: sensing the interference temperature. Since software-defined radio can be a fundamental building block for CR, Mark Cummings explores how SDR has evolved to its present state and where it's going from here. To complement that, the role of FPGAs, advanced transmitter architectures and general-purpose processors in the context of SDR is explored by Altera, M/A-Com and Vanu, respectively.
But while the promise and issues with CR are many, Atheros and Bandspeed show how many of the building blocks are already being implemented in wireless LAN chip designs, while Philips Research-USA puts forth orthogonal frequency division multiplexing as the foundation of future highly flexible wireless networks that will suit the needs of CR.