Feedback-based access and power control for distributed multiuser cognitive networks

Cognitive radio networks enable secondary users to utilize spare bandwidth of primary users by limiting their interference. Moving beyond the traditional listen-before-talk paradigm, we propose a cognitive access methodology that exploits the feedback channel in two-way primary communication links for better spectrum utility and protection of primary users against secondary interference. We let secondary users dynamically control access and power based on primary ACK/NACK messages. We develop an optimal access policy applicable to multiple secondary user pairs. We also devise a distributed power control policy for multiple secondary users to maximize their individual throughput without significant cumulative interference to the primary link. Our distributed access and power control schemes can effectively provide good SU performance and primary protection without requiring central coordination.