This dissertation introduces a finite-source retrial queueing system which models cognitive radio networks. We assume two non-independent frequency bands servicing two classes of users: Primary Users (PUs) and Secondary Users (SUs). A service unit with a priority queue and another service unit with an orbit are assigned to the PUs and SUs, respectively. Simulation was used to obtain several sample examples illustrating the effect of the distribution of the inter-events times on the first and second moments of response times. Some various case studies were treated by the addition of some real-life troubles such as the non-reliability of servers and collision.