Optimal Status Updates in Cognitive Radio-Enabled IoT Networks: An Age of Information Approach

Age of information (AoI) is a performance metric which can be used to measure the freshness of time sensitive information such as health monitoring packets, which are medical information captured by body sensors. We consider a cognitive radio (CR)-enabled internet-of-things (IoT) network, where timely status updates over both primary and secondary links are critical. In such a setup, status updates by primary transmitter (PT) and secondary transmitter (ST) have to be designed in an efficient manner. To this end, we derive an expression for the overall average age of information (AoI) of the network, and formulate an optimization problem based on AoI to find optimal status updates. We show that the formulated optimization problem is convex. Further, we reformulate the AoI minimization problem in the asymptotic scenario of high signal-to-noise ratio, and derive a closed form expression for the optimal PT status rate with a predefined threshold on ST status rate as a constraint. We validate our analysis through numerical techniques.