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

• Published in: IEEE transactions on information theory Vol. 65; no. 3; pp. 1807 - 1827
• Main Authors: Yates, Roy D., Kaul, Sanjit K.
• Format: Journal Article
• Language: English
• Published: New York IEEE 01-03-2019; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Age of information; Automobiles; communication networks; Hybrid systems; Markov analysis; Markov chains; Measurement; Monitoring; Queueing analysis; queueing systems; Queues; Queuing theory; Sensors; Servers; stochastic hybrid systems; Wireless communication
• ISSN: 0018-9448; 1557-9654
• DOI: 10.1109/TIT.2018.2871079

We examine multiple independent sources providing status updates to a monitor through simple queues. We formulate an age of information (AoI) timeliness metric and derive a general result for the AoI that is applicable to a wide variety of multiple source service systems. 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. A new simplified technique for evaluating the AoI in finite-state continuous-time queuing systems is also derived. Based on stochastic hybrid systems, this method makes AoI evaluation to be comparable in complexity to finding the stationary distribution of a finite-state Markov chain.