LAUSR

The timely delivery of status update packets is essential for many real-time Internet of Things (IoT) applications. For monitoring and control, a key performance measure of interest is the Age of Information (AoI). We study the AoI for a status update system with two independent sources and a single server, where a status update packet of a source renders earlier status update packets irrelevant. As new updates might arrive during the service of a status update packet, we study various preemptive update mechanisms. In preemptive scenarios, the packet being served is updated, which affects the remaining service time. Using an effective service time approach, we find explicit expressions for the Laplace-Stieltjes transform of the time average age of information, and of the peak age of information.