Date Added: Jan 2012
Increasingly ubiquitous communication networks and connectivity via portable devices have engendered a host of applications in which sources, for example people and environmental sensors, send updates of their status to interested recipients. These applications desire status updates at the recipients to be as timely as possible; however, this is typically constrained by limited network resources. In this paper, the authors employ a time-average age metric for the performance evaluation of status update systems. They derive general methods for calculating the age metric that can be applied to a broad class of service systems. They apply these methods to queue-theoretic system abstractions consisting of a source, a service facility and monitors, with the model of the service facility (physical constraints) a given.