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.
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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.
