The Age of Information: Real-Time Status Updating by Multiple Sources

We examine multiple independent sources providing status updates to a monitor through simple queues. We formulate a status-age timeliness metric and derive a general result for the average status age that is applicable to a wide variety of multiuser service systems. An alternate technique for evaluating status age based on stochastic hybrid systems is also introduced. For first-come first-served and two types of last-come first-served systems with Poisson arrivals and exponential service times, we find the region of feasible average status ages for multiple updating sources. We then use these results to characterize how a service facility can be shared among multiple updating sources. Index Terms Age of information, queueing systems, random processes, communication networks