Date Added: Dec 2009
The authors venture beyond the "Listen-before-talk" strategy that is common in many traditional cognitive radio access schemes. They exploit the bi-directional nature of most primary communication systems. By intelligently choosing their transmission parameters based on the observation of Primary User (PU) communications, Secondary Users (SUs) in a cognitive network can achieve higher spectrum usage while limiting their interference to the PU. Specifically, they propose that the SUs listen to the PU's feedback channel to assess their interference on the primary receiver (PU-Rx), and adjust radio power accordingly to satisfy the PU's interference constraint. They investigate both centralized and distributed power control algorithms without active PU cooperation.