Performance Analysis of Multi-Modal Overlay/Underlay Switching Service Levels in Cognitive Radio Networks

Cognitive radio networks have become a popular platform for many systems and applications of the future, and especially for Smart City applications and the Internet of Things. The wireless transceivers used for communicating between the different devices in the cognitive radio networks can operate in either of the two modes, namely overlay and underlay, or a hybrid of these two modes. While operating in the underlay mode, secondary users are likely to experience varying transmission rates due to the fluctuating power levels from the primary users. This has the effect of the channel capacity being dynamic, which forces the secondary user to switch between different transmission rates, or “service modes”, during a single networking session. In our previous work, we developed a discrete time queueing model for analyzing the performance of secondary users in such networks with multi-modal and hybrid overlay/underlay switching service levels. In this paper, we extend our previous work to present our novel result for computing the waiting-time distribution of the secondary users. Such results are essential for investigating the sensitivity of the secondary user's performance due to the queueing delays, and especially for real-time applications.