Date Added: May 2010
This paper on cognitive radio access ventures beyond the more traditional "Listen-before-talk" paradigm that underlies many cognitive radio access proposals. The authors exploit the bi-directional interaction of most primary communication links. By intelligently controlling their access parameters based on the inference from observed link control signals of Primary User (PU) communications, cognitive Secondary Users (SUs) can achieve higher spectrum efficiency while limiting their interference to the PU network. In one specific implementation, they let the SUs listen to the PU's feedback channel to assess their own interference on the primary receiver, and adjust radio power accordingly to satisfy the PU's interference constraint.