Performance of a cognitive radio network with tolerable service degradation

We analyze the performance of a cognitive radio wireless network, where secondary users opportunistically share the radio spectrum with primary users through spectrum sensing and may cause service degradation to the primary users due to unreliable spectrum sensing. When a secondary user occupying a channel detects the presence of a primary call arriving to the channel, it switches from its current channel to another channel, if one is available, to continue its service; however, if the secondary user fails to detect the presence of the primary call, it remains on the channel and both calls will receive degraded service. Based on a queueing network model, we derive closed-form solutions for the equilibrium system state in terms of generating functions, and derive several performance metrics of interest. In particular, we introduce the system supportability metric to evaluate the extent to which the system can support secondary users and the interference factor to evaluate the degree of service degradation imposed on primary users by the secondary users. Numerical results are presented to show the impact of system parameters on the derived performance metrics.