On the Age of Information in Multi-Source Queueing Models

TL;DR

This paper analyzes the freshness of information in multi-source queueing systems, deriving exact and approximate formulas for average age of information in M/M/1 and M/G/1 models, validated by simulations.

Contribution

It provides the first exact average AoI expression for multi-source M/M/1 queues and introduces three approximations for M/G/1 queues with general service times.

Findings

Exact average AoI derived for M/M/1 queues.

Three approximate formulas for M/G/1 queues.

Simulation results validate and illustrate AoI behavior.

Abstract

Freshness of status update packets is essential for enabling services where a destination needs the most recent measurements of various sensors. In this paper, we study the information freshness of single-server multi-source queueing models under a first-come first-served (FCFS) serving policy. In the considered model, each source independently generates status update packets according to a Poisson process. The information freshness of the status updates of each source is evaluated by the average age of information (AoI). We derive an exact expression for the average AoI for the case with exponentially distributed service time, i.e., for a multi-source M/M/1 queueing model. Moreover, we derive three approximate expressions for the average AoI for a multi-source M/G/1 queueing model having a general service time distribution. Simulation results are provided to validate the derived exact average AoI expression, to assess the tightness of the proposed approximations, and to demonstrate the AoI behavior for different system parameters.