Slotted Aloha for cognitive radio users and its tagged user analysis

Cognitive radio (CR) is a promising dynamic spectrum access technique to improve the utilization of the licensed spectrum. In this paper, we investigate the medium access control (MAC) protocol for CR networks and propose a cognitive MAC using slotted Aloha to enable CR users to access spectrum holes in a licensed frequency band. In order to avoid the high computational complexities of traditional Markovian analysis, we investigate the tagged user analysis (TUA) based on queuing theories in CR scenarios and use TUA to analyze the proposed cognitive MAC performance. The theoretical derivations based on TUA are presented and computer simulations are performed to evaluate the CR network performance as well as TUA accuracy. The network throughput, packet blocking probability, queue length, packet waiting time and response time are evaluated.