Analysis of Age of Information for A Discrete-Time hybrid Dual-Queue System

TL;DR

This paper analyzes the age of information in a dual-sensor discrete-time system with different service time models, deriving analytical expressions and exploring the relationship with continuous-time systems, revealing that randomness can reduce AoI.

Contribution

It provides the first analytical expressions for AoI in a dual-queue discrete-time system with mixed service times and connects discrete and continuous-time AoI results.

Findings

Random service time reduces AoI more than deterministic service in most cases.

Discrete-time AoI results generalize continuous-time results as a limit case.

Numerical validation confirms the analytical expressions and insights.

Abstract

Using multiple sensors to update the status process of interest is promising in improving the information freshness. The unordered arrival of status updates at the monitor end poses a significant challenge in analyzing the timeliness performance of parallel updating systems. This work investigates the age of information (AoI) of a discrete-time dual-sensor status updating system. Specifically, the status update is generated following the zero-waiting policy. The two sensors are modeled as a geometrically distributed service time queue and a deterministic service time queue in parallel. We derive the analytical expressions for the average AoI and peak AoI using the graphical analysis method. Moreover, the connection of average AoI between discrete-time and continuous-time systems is also explored. It is shown that the AoI result of the continuous-time system is a limit case of that of the corresponding discrete-time system. Hence, the AoI result of the discrete-time system is more general than the continuous one. Numerical results validate the effectiveness of our analysis and further show that randomness of service time contributes more AoI reduction than determinacy of service time in dual-queue systems in most cases, which is different from what is known about the single-queue system.