A slotted Aloha based random access cognitive radio network and its performance evaluation

In this paper, a slotted Aloha based cognitive radio (CR) network that consists of two classes of users, primary users (PUs) and CR users is considered and its throughput performance is evaluated. PUs and CR users share the time slotted based common communication channel. PUs are authorized to access the channel and utilize Time Division Multiple Access (TDMA) as a Medium Access Control (MAC) technique. CR users employ slotted Aloha as a random access scheme and can access the channel when it is not occupied by the PUs. We have derived new expressions for the throughput of both CR network and overall network to evaluate the channel utilization. In addition, an example network scenario has been developed, modeled and simulated by using the OPNET Modeler simulation software with the aim of verifying the analytical throughput results. The simulation results obtained under various network load conditions are precisely match with the analytical results. This study has also shown that the overall channel utilization can be improved by well exploiting the spectrum holes without interfering with the PUs´ transmissions.