Date Added: Jun 2011
Time domain spectrum sharing between Primary User (PU) and Cognitive Radio (CR) networks is considered. The Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) protocol is suitable for this type of spectrum sharing with unslotted access in which PUs and Secondary Users (SUs) are asynchronous. The goal is to maximize the average throughput of the SUs while guaranteeing the average throughput of the PUs. To achieve this, in the authors' proposal the CR network adaptively changes its minimum Contention Window size (CWmin), depending on the Channel Occupancy Rate (COR) from the PU network. The COR is approximately proportional to the average throughput and is estimated based on the observed traffic.