Limits on communications in a cognitive radio channel

In this article we review FCC secondary markets initiatives and how smart wireless devices could be used to increase spectral efficiency. We survey the current proposals for cognitive radio deployment, and present a new, potentially more spectrally efficient model for a wireless channel employing cognitive radios; the cognitive radio channel. This channel models the simplest scenario in which a cognitive radio could be used and consists of a 2 Tx, 2 Rx wireless channel in which one transmitter knows the message of the other. We obtain fundamental limits on the communication possible over such a channel, and discuss future engineering and regulatory issues