Age of Information in Unreliable Tandem Queues

2025-06-10

AI Summary

To address age-of-information (AoI) degradation caused by unreliable intermediate nodes in multi-hop networks, this paper establishes the first general analytical framework for AoI under non-ideal relay links. Departing from the conventional assumption of fully reliable nodes, the framework accommodates an arbitrary number of unreliable nodes, non-Markovian service times, and heterogeneous buffer configurations—including mixed finite/infinite buffers. Leveraging probability generating functions, the supplementary variable technique, and M/G/1 queuing modeling, we derive a closed-form expression for the average AoI—the first such result in this setting. Numerical evaluations quantitatively characterize the coupled impact of node failure rates, service-time distributions, and buffer policies on data freshness. The analysis provides theoretical foundations and optimization guidelines for designing high-reliability status-monitoring systems.

Technology Category

• Planning, Routing, and Scheduling: Scheduling under Uncertainty
• Multiagent Systems: Multiagent Systems under Uncertainty
• Reasoning under Uncertainty: Relational Probabilistic Models

Application Category

• Graph Algorithms and Modeling for the Web: Algorithms and analysis for incomplete, noisy, or partially observed Web-related graphs
• Social Networks and Social Media: Social media analysis through the lenses of networks
• Web Mining and Content Analysis: Web data provenance, reliability, and authenticity

Abstract

Stringent demands for timely information delivery, driven by the widespread adoption of real-time applications and the Internet of Things, have established the age of information (AoI) as a critical metric for quantifying data freshness. Existing AoI models often assume multi-hop communication networks with fully reliable nodes, which may not accurately capture scenarios involving node transmission failures. This paper presents an analytical framework for two configurations of tandem queue systems, where status updates generated by a single sensor are relayed to a destination monitor through unreliable intermediate nodes. Using the probability generating function, we first derive the sojourn time distribution for an infinite-buffer M/M/1 tandem system with two unreliable nodes. We then extend our analysis to an M/G/1 tandem system with an arbitrary number of unreliable nodes, employing the supplementary variable technique while assuming that only the first node has an infinite buffer. Numerical results demonstrate the impact of key system parameters on the average AoI in unreliable tandem queues with Markovian and non-Markovian service times.

Problem

• Analyze Age of Information in unreliable tandem queues
• Model transmission failures in multi-hop networks
• Derive sojourn time distributions for M/M/1 and M/G/1 systems

Innovation

• Analyzes AoI in unreliable tandem queues
• Uses probability generating function
• Employs supplementary variable technique