Age of Information in Multiple Sensing of a Single Source

Having timely and fresh knowledge about the current state of information sources is critical in a variety of applications. In particular, a status update may arrive at its destination much later than its generation time due to processing and communication delays. The freshness of the status update at the destination is captured by the notion of age of information. In this study, we consider a network with a single source, a single monitor (destination), and n sensors. In this setting, a single source of information is being sensed independently by different sensors and the data is sent to the monitor. We assume that updates about the source of information arrive at the sensors according to a Poisson random process. Each sensor sends its update to the monitor through a direct link, which is modeled as a queue. The service time to transmit an update is considered to be an exponential random variable. We derive a closed-form expression for the average age of information in our model under a last-come-first-serve (LCFS) queue. Then, we compare different queue setups of first-come-first-serve (FCFS), LCFS, and LCFS with preemption in waiting in terms of the average age of information. It is observed that LCFS is the best queue among the service disciplines.