Abstract
Motivated by current communication networks in which users can choose different transmission channels to operate and also by the recent growth of renewable energy sources, we study the average Age of Information of a status update system that is formed by two parallel homogeneous servers and such that there is an energy source that feeds the system following a random process. An update, after getting service, is delivered to the monitor if there is energy in a battery. However, if the battery is empty, the status update is lost. We allow preemption of updates in service and we assume Poisson generation times of status updates and exponential service times. We show that the average Age of Information can be characterized by solving a system with eight linear equations. Then, we show that, when the arrival rate to both servers is large, the average Age of Information is one divided by the sum of the service rates of the servers. We also perform a numerical analysis to compare the performance of our model with that of a single server with energy harvesting and to study in detail the aforementioned convergence result.
Highlights
In Proposition 1, we show that the computation of the average Age of Information of the system under study requires to solve Equation (2a–p), which is a system of 16 linear equations with 16 variables
We model this system as a system with Poisson arrivals of status updates to two parallel servers and of energy packets to a battery
We first show that the average Age of Information of this system can be computed by solving a system of 8 linear equations (Proposition 2)
Summary
The Age of Information is a recent metric of the performance of systems and it measures the freshness of the information that a monitor has about the status of a remote process of interest. Current communication networks are very complex and often allow users to operate using different transmission channels This is the case, for instance, when a user is a part of an overlay network (i.e., when it belongs to a set of nodes that are located in different spots over the Internet and collaborate with each other to forward data between any pair of nodes with minimum delay). In this instance, the user can choose the transmission channel that provides the IP protocol or through the overlay network. We consider that the transmission channel is formed by parallel servers that do not interchange information and a battery that can store energy that can be used to send status updates after getting service in the servers
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