  Age of Information (AoI) is a critical metric for several Internet of Things
(IoT) applications, where sensors keep track of the environment by sending
updates that need to be as fresh as possible. The development of edge computing
solutions has moved the monitoring process closer to the sensor, reducing the
communication delays, but the processing time of the edge node needs to be
taken into account. Furthermore, a reliable system design in terms of freshness
requires the knowledge of the full distribution of the Peak AoI (PAoI), from
which the probability of occurrence of rare, but extremely damaging events can
be obtained. In this work, we model the communication and computation delay of
such a system as two First Come First Serve (FCFS) queues in tandem,
analytically deriving the full distribution of the PAoI for the M/M/1 - M/D/1
and the M/M/1 - M/M/1 tandems, which can represent a wide variety of realistic
scenarios.
